JP7766928B2 - Vehicle antenna device - Google Patents

Description

This disclosure relates to an in-vehicle antenna device.

Patent Document 1 discloses an in-vehicle receiver. This in-vehicle receiver includes a receiving antenna mounted on the vehicle to receive target radio waves arriving from outside the vehicle; a flat metal body electrically separated from the vehicle body in a location where the target radio waves are less likely to reach than the receiving antenna; a voltage detection unit that detects the voltage between the metal body and the vehicle body; and a noise removal unit that treats the voltage detected by the voltage detection unit as noise and removes the noise from the radio waves received by the receiving antenna.

Patent Document 2 discloses an antenna system. This antenna system includes a glass antenna attached to the window glass installed in a window opening formed in the metal body of a vehicle and receiving radio waves in the MF or LF band, an interior antenna located inside the vehicle relative to the metal body and in the vicinity of the glass antenna, and cancellation means for canceling noise signals from the interior antenna from signals received by the glass antenna.

Patent Document 3 discloses an antenna system. This antenna system includes a first antenna having a first antenna conductor and a first feed point and receiving broadcast waves of a predetermined frequency band; a second antenna having a second antenna conductor and a second feed point and receiving noise from a noise source; and a cancellation device that cancels a noise signal received by the second antenna from a signal received by the first antenna. The first and second antennas are located at positions where broadcast waves of the predetermined frequency band arrive. The reception gain of the predetermined frequency band received by the second antenna is lower than the reception gain of the predetermined frequency band received by the first antenna. The conductor length of the second antenna conductor is shorter than the conductor length of the first antenna conductor. This adjusts the noise output received by the first antenna to be equal to the noise output received by the second antenna.

JP 2013-168744 A International Publication No. 2015/016307 International Publication No. 2015/093490

Traditionally, radio broadcast wave antennas are installed in vehicles. Because radio broadcast wave antennas are analog, they are susceptible to the effects of electromagnetic noise generated inside or outside the vehicle. This phenomenon is particularly pronounced in the AM wave band. Furthermore, in recent years, in addition to conventional gasoline-powered vehicles, PHEVs (plug-in hybrid vehicles) and EVs (electric vehicles) have been developed and put into practical use. These vehicles are equipped with electrical components not found in gasoline-powered vehicles, such as drive motors, large batteries for driving the drive motors, and voltage converters. Furthermore, the vehicle layout of some of the conventional electrical equipment differs from that of gasoline-powered vehicles. Therefore, radio broadcast wave antennas pick up the large electromagnetic noise generated by these electrical components and equipment.

One technique that has been proposed is to provide a noise pickup antenna separate from the radio broadcast wave antenna, install the noise pickup antenna in a location that is difficult to receive radio broadcast waves but is equally susceptible to electromagnetic noise as the radio broadcast wave antenna, and then subtract the output signal of the noise pickup antenna from the output signal of the radio broadcast wave antenna to cancel the noise components contained in the radio broadcast wave antenna's output signal (see, for example, Patent Documents 1 to 3). However, this technique poses a problem: the phase difference between the noise components contained in the output signal of the radio broadcast wave antenna and the noise components contained in the output signal of the noise pickup antenna. For example, if the distance from the noise source to the noise pickup antenna is significantly different from the distance from the noise source to the radio broadcast wave antenna, or if the shape of the noise pickup antenna is different from that of the radio broadcast wave antenna, a phase difference will arise between the noise components contained in the output signal of the radio broadcast wave antenna and the noise components contained in the output signal of the noise pickup antenna. This phase difference prevents the effective cancellation of the noise components, resulting in a large amount of noise remaining. Signal processing circuits (phase correction circuits) exist that eliminate the phase difference between the output signal of the radio broadcast wave antenna and the output signal of the noise pickup antenna, but using such signal processing circuits complicates the circuit configuration and increases manufacturing costs.

One embodiment of the present disclosure has been made in consideration of these problems, and aims to provide an in-vehicle antenna device that can reduce the phase difference between the noise components contained in the output signal of the radio broadcast wave antenna and the noise components contained in the output signal of the noise pickup antenna without complicating the circuit configuration.

[1] In order to solve the above-mentioned problems, an in-vehicle antenna device according to one embodiment of the present disclosure is an antenna device mounted on a vehicle, and includes a first conductor, a second conductor, and a noise reduction circuit. The first conductor includes a first antenna installed in the vehicle and receiving radio broadcast waves from outside the vehicle and outputting a first signal, and a first feeder line electrically connected to the first antenna and transmitting the first signal. The second conductor includes a second antenna installed in a location where radio broadcast waves are more difficult to receive than the first antenna and outputting a second signal, and a second feeder line electrically connected to the second antenna and transmitting the second signal. The second conductor includes a capacitive coupling portion that capacitively couples with at least a portion of the first conductor. The noise reduction circuit is electrically connected to the first feeder line and the second feeder line, receives the first signal from the first antenna via the first feeder line, receives the second signal from the second antenna via the second feeder line, and performs processing to reduce noise components included in the first signal using the second signal.

[2] An in-vehicle antenna device according to one embodiment of the present disclosure is an antenna device mounted on a vehicle and includes a first conductor, a second conductor, and a noise reduction circuit. The first conductor includes a first antenna installed on the vehicle, receiving radio broadcast waves arriving from outside the vehicle and outputting a first signal, and a first feeder line electrically connected to the first antenna and transmitting the first signal. The second conductor includes a second antenna installed in a location more susceptible to noise from vehicle noise sources than the first antenna, outputting a second signal, and a second feeder line electrically connected to the second antenna and transmitting the second signal. The second conductor includes a capacitive coupling portion that capacitively couples with at least a portion of the first conductor. The noise reduction circuit is electrically connected to the first feeder line and the second feeder line, receives the first signal from the first antenna via the first feeder line, receives the second signal from the second antenna via the second feeder line, and performs processing to reduce noise components included in the first signal using the second signal.

In the vehicle antenna devices of [1] and [2] above, the first antenna receives radio broadcast waves and outputs a first signal containing radio broadcast waves and noise components. The second antenna outputs a second signal in which the ratio of noise components to radio broadcast waves is greater than that of the first signal. The first and second signals are transmitted via first and second feed lines, respectively, and reach the noise reduction circuit. The noise reduction circuit uses the second signal to reduce the noise components contained in the first signal.

In addition, in the vehicle-mounted antenna devices of [1] and [2] above, the second conductor has a capacitive coupling portion that capacitively couples with at least a portion of the first conductor. The capacitive coupling portion has the effect of bringing the phases of the signals, particularly noise components, transmitted to the first and second conductors closer together. Therefore, this vehicle-mounted antenna device can reduce the phase difference between the noise components contained in the output signal of the first antenna (radio broadcast wave antenna) and the noise components contained in the output signal of the second antenna (noise pickup antenna). Furthermore, because a structure that reduces the phase difference can be achieved with a simple configuration that simply capacitively couples the conductors, a complex circuit configuration is not required. In this disclosure, the capacitance value of the capacitive coupling is preferably within the range of 0.5 pF to 6 pF.

[3] In the vehicle-mounted antenna device of [1] or [2] above, the shape of the second antenna may be different from the shape of the first antenna. In this case, a phase difference is likely to occur between the first signal and the second signal, making the above-mentioned configuration of the vehicle-mounted antenna device particularly useful. Note that "shape" here also includes size.

[4] In any of the above-described in-vehicle antenna devices [1] to [3], the first antenna may be a glass antenna installed on the vehicle window glass, and the second antenna may include a conductive plate-shaped portion. In many cases, glass antennas are installed within a relatively large area of a large glass surface, such as a rear window. In contrast, the second antenna is placed in a relatively small area where it is more difficult to receive radio broadcast waves than the first antenna, such as near the glass inside a metal body. Even in such cases, by including a conductive plate-shaped portion (capacitive loading plate) in the second antenna, the second antenna can be made compact while still being given noise susceptibility equivalent to that of a glass antenna.

[5] In any of the above-mentioned in-vehicle antenna devices [1] to [4], the noise reduction circuit may include a circuit that inverts the first signal or the second signal and then adds the first signal and the second signal. For example, with this configuration, the noise component contained in the first signal can be reduced using the second signal.

[6] In any of the above in-vehicle antenna devices [1] to [5], the capacitive coupling section may be capacitively coupled to an intermediate portion of the first feed line. Even in this case, the effects of the above in-vehicle antenna device can be obtained.

[7] In any of the above in-vehicle antenna devices [1] to [6], the capacitive coupling portion may include a flat plate disposed opposite the upper surface of the terminal portion of the first conductor, and may include a portion that covers the terminal portion of the first conductor from at least three sides to further increase the capacitance value. In this case, the capacitance value of the capacitive coupling portion can be increased to further reduce the phase difference between the two noise components.

[8] In any of the above-described vehicle-mounted antenna devices [1] to [7], the first and second feeder lines may each have an insulated wire, and at least a portion of the insulated wire of the second feeder line may be arranged parallel to and adjacent to at least a portion of the insulated wire of the first feeder line. In this case, the capacitance value of the capacitive coupling section may be increased to further reduce the phase difference between the two noise components.

[9] In any of the above-mentioned in-vehicle antenna devices [1] to [8], the first feed line may be arranged along the shortest path between the feed point of the first antenna and the noise reduction circuit, and the capacitive coupling unit may include a portion arranged parallel to and adjacent to the first feed line arranged along that path. In this case, the first feed line may be shortened to suppress the effect of electromagnetic noise on the first feed line, while the capacitance value of the capacitive coupling unit may be increased to effectively reduce the phase difference between the two noise components.

[10] Any of the above-described vehicle-mounted antenna devices [1] to [9] may further include a wiring board on which circuit components that perform the above-described processing are mounted, and the first and second feeder lines may include pattern wiring portions provided on the wiring board.

[11] In the in-vehicle antenna device of [10] above, the capacitive coupling section may include a pattern wiring portion of the second feeder line that provides capacitive coupling with the pattern wiring portion of the first feeder line. In this case, stable capacitive coupling can be achieved by the pattern wiring portion provided on the wiring board.

[12] In the vehicle-mounted antenna device of [1] above, the second antenna may be installed on the inner surface of the vehicle's metal body. In this case, the second antenna can be installed in a location where it is more difficult to receive radio broadcast waves than the first antenna.

[13] In the vehicle-mounted antenna device of [2] above, the noise source may be located at the bottom of the vehicle, and the second antenna may be installed closer to the bottom of the vehicle than the first antenna. In this case, the second antenna can be installed in a location where it is more susceptible to noise from the vehicle's noise source than the first antenna.

[14] In the vehicle-mounted antenna device of [13] above, the first antenna may be a glass antenna installed on the rear windshield of the vehicle, and the second antenna may include a linear portion provided around the combination lamp located below the rear windshield. In this case, the second antenna can be made less noticeable on the vehicle's exterior and can be installed in a location that makes it easy to connect to a noise reduction circuit inside the vehicle.

[15] In the vehicle-mounted antenna device of [2], [13], or [14] above, the noise source may be located at the bottom of the vehicle, and the vehicle-mounted antenna device may further include a canopy that covers at least the upper part of the second antenna to block radio broadcast waves. In this case, the second antenna has difficulty receiving radio broadcast waves, and the noise components contained in the first signal can be more effectively reduced using the second signal.

[16] In any of the above in-vehicle antenna devices [2], [13] to [15], the second feeder may partially include a cable in which the conductor transmitting the second signal is shielded at ground potential. Depending on the arrangement of the second antenna, the second feeder may be long, which may cause noise from a noise source other than the noise source generating the noise input to the first antenna to be superimposed on the second signal via the second feeder. In such cases, by constructing the portion of the second feeder that is susceptible to noise from the other noise source with the above cable, it is possible to reduce the noise from the other noise source superimposed on the second signal.

[17] In any of the above in-vehicle antenna devices [2], [13] to [16], the second antenna may be located on the outside of the metal body. In this case, the second antenna can be installed in a location that is more susceptible to noise from noise sources installed on the outside of the vehicle than the first antenna.

[18] In any of the above in-vehicle antenna devices [1] to [17], the reception sensitivity of the second antenna for radio broadcast waves may be equal to or less than the reception sensitivity of the first antenna for radio broadcast waves minus 20 dB. In this case, the reception sensitivity of the entire in-vehicle antenna device for radio broadcast waves can be sufficiently increased.

[19] An in-vehicle antenna device according to one embodiment of the present disclosure is an antenna device mounted on a vehicle and includes a first conductor, a second conductor, a third conductor, and a noise reduction circuit. The first conductor includes a first antenna installed on the vehicle, receiving radio broadcast waves from outside the vehicle and outputting a first signal, and a first feeder line electrically connected to the first antenna and transmitting the first signal. The second conductor includes a second antenna installed in a location less susceptible to receiving radio broadcast waves than the first antenna, outputting a second signal, and a second feeder line electrically connected to the second antenna and transmitting the second signal. The third conductor includes a third antenna installed in a location more susceptible than the first antenna to noise from a noise source located outside the metal body of the vehicle, outputting a third signal, and a third feeder line electrically connected to the third antenna and transmitting the third signal. The noise reduction circuit is electrically connected to the first, second, and third feed lines, receives a first signal from the first antenna via the first feed line, receives a second signal from the second antenna via the second feed line, and receives a third signal from the third antenna via the third feed line, and performs processing to reduce noise components contained in the first signal using the second and third signals. The second and third conductors have capacitive coupling portions that are capacitively coupled to at least a portion of the first conductor.

In the vehicle-mounted antenna device of [19] above, the first antenna receives radio broadcast waves and outputs a first signal containing radio broadcast waves and noise components. The second and third antennas output second and third signals, respectively, in which the ratio of noise components to radio broadcast waves is greater than that of the first signal. The first, second, and third signals are transmitted via the first, second, and third feeders, respectively, and reach the noise reduction circuit. The noise reduction circuit uses the second and third signals to reduce the noise components contained in the first signal.

In addition, in the vehicle-mounted antenna device of [19] above, the second and third conductors have capacitive coupling portions that capacitively couple with at least a portion of the first conductor. The capacitive coupling portions have the effect of bringing the phases of the signals, particularly noise components, transmitted to the first, second, and third conductors closer together. Therefore, this vehicle-mounted antenna device can reduce the phase difference between the noise components contained in the output signal of the first antenna (radio broadcast wave antenna) and the noise components contained in the output signals of the second and third antennas (noise pickup antennas). Furthermore, because a structure that reduces the phase difference can be achieved with a simple configuration that simply capacitively couples the conductors, a complex circuit configuration is not required.

An in-vehicle antenna device according to one embodiment of the present disclosure can reduce the phase difference between the noise components contained in the output signal of the radio broadcast wave antenna and the noise components contained in the output signal of the noise pickup antenna without complicating the circuit configuration.

FIG. 1 is a block diagram showing a schematic configuration of an antenna device according to an embodiment of the present disclosure. FIG. 2 is a diagram showing an example of a state in which the antenna device is attached to a vehicle. FIG. 3 is a diagram showing a cross section of the second antenna and the surrounding window glass and metal body. FIG. 4 is a plan view showing the specific structure of the second antenna and the covering portion. FIG. 5 is a cross-sectional view taken along line VV in FIG. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. FIG. 7 is a diagram showing the noise reduction circuit, the first feed line, and the second feed line. FIG. 8 is a diagram showing an example of a signal waveform output from the noise reduction circuit. FIG. 9 is a diagram showing, as a comparative example, an example of a signal waveform when the noise component is not canceled. FIG. 10 is a diagram showing an example of a state in which the antenna device of the first modified example is attached to a vehicle. FIG. 11 is a diagram schematically showing a cross section of the second antenna of the second modified example and the window glass and metal body around the second antenna. FIG. 12 is a diagram showing an example of the arrangement of the second antenna. FIG. 13 is a diagram showing an example of an actual measurement of a signal waveform output from a noise reduction circuit. FIG. 14 is a diagram showing an example of a signal waveform measured when the noise component is not canceled, as a comparative example. Parts (a) and (b) of FIG. 15 are cross-sectional views showing an example of the configuration of the second antenna and its vicinity according to the second modified example. FIG. 16 is a plan view showing the configuration of a circuit board according to a third modified example. FIG. 17 is a block diagram showing a schematic configuration of an antenna device according to the second embodiment.

Embodiments of an in-vehicle antenna device according to the present disclosure will be described in detail below with reference to the accompanying drawings. Note that identical elements will be designated by the same reference numerals throughout the description of the drawings, and duplicate explanations will be omitted.

[First embodiment]
FIG. 1 is a block diagram showing a schematic configuration of an in-vehicle antenna device 1 (hereinafter simply referred to as an antenna device) according to a first embodiment of the present disclosure. The antenna device 1 of this embodiment is attached to a vehicle such as an automobile. FIG. 2 is a diagram showing an example of the antenna device 1 attached to a vehicle. In the example shown in FIG. 2, the antenna device 1 is disposed inside (toward the passenger compartment) the metal body of the automobile and a window glass 51 attached to an opening in the metal body. As shown in FIGS. 1 and 2, the antenna device 1 of this embodiment includes a first conductor 10, a second conductor 20, a noise reduction circuit 30, a relay cable 41, and a tuner 42. Note that the relay cable 41 and the tuner 42 are not shown in FIG. 2.

The first conductor 10 has a first antenna 11, a first power supply line (feeder line) 12, and a terminal portion 13. The first antenna 11 is an antenna for radio broadcast waves. The first antenna 11 is installed in a location in the vehicle where it can receive radio broadcast waves, receives radio broadcast waves arriving from outside the vehicle, and converts the radio broadcast waves into an electrical first signal Sg1. The first antenna 11 outputs the first signal Sg1 to the noise reduction circuit 30. The first antenna 11 also receives electromagnetic noise generated from electrical components and electrical equipment inside the vehicle. The first signal Sg1 output from the first antenna 11 includes noise components converted from this electromagnetic noise.

As shown in FIG. 2, the first antenna 11 may be a glass antenna attached to a window glass 51 of a vehicle. The window glass 51 may be any window glass installed in an opening in a metal body, such as a rear window, quarter glass, rear side glass, or roof glass. When the first antenna 11 is a glass antenna, it is provided planarly on the surface of the window glass 51 and may be formed by printing a conductive paste, such as silver paste, on the interior-facing surface of the window glass 51 and then baking the conductive paste. However, the shape of the glass antenna is not limited to this. For example, a linear or film-like conductor may be fixed to the interior-facing or exterior surface of the window glass 51 with an adhesive or the like, or may be embedded inside the window glass 51 (between the interior-facing and exterior surfaces).

The first antenna 11 is installed within a relatively large area AR on a large glass surface. The area AR has, for example, a horizontally elongated shape. The area AR is located, for example, within the upper half of the window glass 51. The window glass 51 is installed in a window opening formed in the metal body of the vehicle, so radio broadcast waves pass through the window glass 51 to reach the first antenna 11. Note that the first antenna 11 is not limited to being a glass antenna. The first antenna 11 may also be installed on the outside of the metal body, for example, inside a door mirror. The radio broadcast waves have frequencies within, for example, the AM band (520 kHz to 1710 kHz), the MF band (300 kHz to 3000 kHz), or the LF band (30 kHz to 300 kHz).

The first feeder 12 has one end electrically connected to the first antenna 11. The first feeder 12 transmits the first signal Sg1 output from the first antenna 11. The first feeder 12 is, for example, an insulated wire (AV wire) in which a linear conductor is coated with a resin such as polyvinyl chloride. Note that the first feeder 12 in this embodiment does not use a cable (shielded wire or coaxial cable) in which the conductor transmitting the signal is shielded at ground potential. The first feeder 12 is linearly arranged along the shortest path between the feed point (terminal portion 13) of the first antenna 11 and the noise reduction circuit 30. Note that "shortest" does not mean the shortest in the strict sense, but rather means a range within which the effects of the present invention can be achieved, and refers to the substantially shortest path. The first feeder 12 is mainly arranged inside the metal body in an area along the outer edge of the window glass 51. A portion of the first feeder 12 may overlap the window glass 51. In this case, the first power supply line 12 also receives radio broadcast waves from outside the vehicle, but the magnitude of these waves is small compared to the magnitude of the radio broadcast waves received by the first antenna 11.

The terminal portion 13 is provided between the first antenna 11 and the first power supply line 12. The first antenna 11 is electrically connected to the first power supply line 12 via the terminal portion 13. As shown in FIG. 2 , the terminal portion 13 is provided on the inner surface (the surface facing the passenger compartment) of the window glass 51, for example, in an area near the edge of the window glass 51.

The second conductor 20 has a second antenna 21, a second feeder line 22, and a covering portion 23. The second antenna 21 is a noise pickup antenna. The second antenna 21 is installed in a location in the vehicle where it is more difficult to receive radio broadcast waves than the first antenna 11. The second antenna 21 receives electromagnetic noise generated from electrical components and electrical equipment inside the vehicle to the same extent as the first antenna 11. The receiving sensitivity of the second antenna 21 to radio broadcast waves is equal to or less than the receiving sensitivity of the first antenna 11 to radio broadcast waves, for example, 20 dB. In other words, the receiving sensitivity of the second antenna 21 to radio broadcast waves is equal to or less than 10% of the receiving sensitivity of the first antenna 11 to radio broadcast waves. Note that the receiving sensitivity to radio broadcast waves here refers to, for example, the signal-to-noise ratio. The closer the sensitivity of the second antenna 21 to electromagnetic noise generated from electrical components and electrical equipment inside the vehicle is to the sensitivity of the first antenna 11 to that electromagnetic noise, the better. In one example, the sensitivity of the second antenna 21 to electromagnetic noise is approximately equal to the sensitivity of the first antenna 11 to the same electromagnetic noise. Figure 3 is a schematic cross-sectional view of the second antenna 21 and the surrounding window glass 51 and metal body 52. In the example shown in Figures 2 and 3, the second antenna 21 is disposed on the inner surface (the surface facing the passenger compartment) of the vehicle's metal body 52, near the edge of the window glass 51. In this arrangement, radio broadcast waves from outside the vehicle are blocked by the vehicle's metal body 52, making it difficult for them to reach the second antenna 21. The location of the second antenna 21 is not limited to this, and it may be disposed in another location, such as in the luggage compartment behind the rear seats. Furthermore, the second antenna 21 is preferably disposed in the space between the vehicle's metal body 52 and the interior trim so as not to be visible to occupants.

The second antenna 21 generates an electrical second signal Sg2 (see FIG. 1) that includes noise components due to electromagnetic noise generated from electrical components and electrical equipment inside the vehicle. The second signal Sg2 may include components due to radio broadcast waves to a lesser extent than the first signal Sg1. The second antenna 21 outputs the second signal Sg2 to the noise reduction circuit 30.

The second feeder line (feeder line) 22 has one end electrically connected to the second antenna 21. The second feeder line 22 transmits the second signal Sg2 output from the second antenna 21. The second feeder line 22 is, for example, an insulated wire (AV wire) in which a linear conductor is coated with a resin such as polyvinyl chloride. Note that the second feeder line 22 in this embodiment does not use a cable (shielded wire or coaxial cable) in which the conductor transmitting the signal is shielded at ground potential. The second feeder line 22 is mainly disposed inside the metal body 52 in an area along the outer edge of the window glass 51. A portion of the second feeder line 22 may overlap the window glass 51.

The covering portion 23 is provided between the second antenna 21 and the second power feed line 22. The second antenna 21 is electrically connected to the second power feed line 22 via the covering portion 23. Alternatively, the covering portion 23 may be provided so as to protrude so that only one end is connected to the wiring electrically connecting the second antenna 21 and the second power feed line 22 or to the second antenna 21.

In this embodiment, the first power supply line 12, terminal portion 13, second power supply line 22, and coating portion 23 constitute a noise phase tuning unit 27 (see Figure 1) for bringing the phases of the noise components contained in the first signal Sg1 and the second signal Sg2 closer together (tuning them). The specific configuration of the noise phase tuning unit 27 and the second antenna 21 is described below.

Figures 4 to 6 show the specific structures of the second antenna 21, covering portion 23, and terminal portion 13. Figure 4 is a plan view, Figure 5 is a cross-sectional view taken along line V-V in Figure 4, and Figure 6 is a cross-sectional view taken along line VI-VI in Figure 4. As shown in these figures, the terminal portion 13 includes a metal plate attached to one end of the first power supply line 12, and in one example, is made of this metal plate. The terminal portion 13 is covered by a terminal holding portion 14 made of resin (e.g., rubber) and is held by the terminal holding portion 14 within a recess 14b formed in the bottom surface 14a of the terminal holding portion 14. Note that the material of the terminal holding portion 14 is not limited to resin; various other insulating materials may also be used. The terminal holding portion 14 has a roughly rectangular parallelepiped outer shape and is fixed to the window glass 51 by adhering its bottom surface 14a to the window glass 51. The power supply portion of the first antenna 11 attached to the window glass 51 contacts the terminal portion 13 within the recess 14b. The recess 14b extends to the front surface 14f of the terminal holder 14, and the first power supply line 12 extending from the terminal portion 13 extends from the front surface 14f to the outside of the terminal holder 14.

The covering portion 23 constitutes a capacitive coupling portion 24 that capacitively couples with at least a portion of the first conductor 10. The covering portion 23 includes a flat plate 231 disposed opposite the upper surface of the terminal portion 13. The flat plate 231 capacitively couples with the terminal portion 13 across the terminal holding portion 14. In the illustrated example, the covering portion 23 is composed of a conductor that covers the terminal portion 13 on at least three sides. In one example, the covering portion 23 is provided on at least a portion of the surfaces of the terminal holding portion 14 other than the bottom surface 14a. In the illustrated example, the covering portion 23 is provided across the pair of side surfaces 14c, the back surface 14d, and the top surface 14e of the terminal holding portion 14. However, this example is not limiting, and the covering portion 23 may also be composed of a conductor that covers the terminal portion 13 from at least one side. For example, the covering portion 23 may be provided only on the top surface 14e of the terminal holding portion 14.

The covering portion 23, having the above-described configuration, capacitively couples with the terminal portion 13. The capacitance value of this capacitive coupling depends on the thickness and dielectric constant of the terminal holding portion 14 and the opposing area of the covering portion 23 and the terminal portion 13. The covering portion 23 may be a metal plate or metal foil processed to fit the surface of the terminal holding portion 14, or may be a metal film formed on the surface of the terminal holding portion 14 by vapor deposition, plating, or the like. One end of the second power supply line 22 is connected to the surface of the covering portion 23 (e.g., the surface of the portion above the upper surface 14e) by a conductive adhesive structure such as soldering or brazing. The second power supply line 22 extends along the first power supply line 12. The constituent material of the covering portion 23 includes one or more conductive materials, such as sheet metal, metal film, and conductive resin.

As shown in FIG. 4, the second antenna 21 has a different shape from the first antenna 11. In the illustrated example, the second antenna 21 has a conductive plate-shaped portion (capacitance loading plate) 25. In addition, the second antenna 21 further includes a conductive plate-shaped portion 26 extending from the plate-shaped portion 25 toward the second feed line 22 and the covering portion 23. The width W2 of the plate-shaped portion 26 in a direction perpendicular to the connection direction of the plate-shaped portions 25 and 26 is smaller than the width W1 of the plate-shaped portion 25 in the same direction. The area of the plate-shaped portion 26 is also smaller than the area of the plate-shaped portion 25. In one example, one longitudinal end of the plate-shaped portion 26 is connected to the plate-shaped portion 25, and the other longitudinal end of the plate-shaped portion 26 is connected to the surface of the covering portion 23. The plate-shaped portion 25 and the plate-shaped portion 26 may be formed from a single common metal plate. The other longitudinal end of the plate-shaped portion 26 is connected to the surface of the covering portion 23 by a conductive adhesive structure such as soldering or brazing. The plate-shaped portions 25, 26 of the second antenna 21 are made of one or more conductive materials, such as sheet metal, conductive film, and conductive resin.

In the illustrated example, the plate-shaped portion 25 is connected to the covering portion 23 only via the plate-shaped portion 26, but this is not limited to this configuration. The plate-shaped portion 25 may be connected to the covering portion 23 via the plate-shaped portion 26 and other wiring, or may be connected to the covering portion 23 via other wiring instead of the plate-shaped portion 26. Furthermore, the portion of the second antenna 21 that is connected to the covering portion 23 and a portion nearby (e.g., part of the plate-shaped portion 26) may be positioned in a position where radio broadcast waves can be received (e.g., a position overlapping the window glass 51). It is sufficient that the second antenna 21 as a whole is less likely to receive radio broadcast waves than the first antenna 11.

Figure 7 is a diagram showing the noise reduction circuit 30, the first power supply line 12, and the second power supply line 22. As shown in Figure 7, at least a portion of the insulated wires that make up the second power supply line 22 are arranged parallel to and adjacent to at least a portion of the insulated wires that make up the first power supply line 12. The portion of the second power supply line 22 that is arranged parallel to and adjacent to the first power supply line 12 constitutes the capacitive coupling portion 24. In this way, the capacitive coupling portion 24 also capacitively couples with an intermediate portion of the first power supply line 12. That is, the capacitive coupling portion 24 in this embodiment includes the coating portion 23 described above and the portion of the second power supply line 22 that is arranged parallel to and adjacent to the first power supply line 12.

This portion of the second feed line 22 is arranged parallel to and adjacent to the first feed line 12, thereby capacitively coupling with the first feed line 12. The capacitance value of this capacitive coupling depends on the sum of the thicknesses of the insulating coatings of the first feed line 12 and the second feed line 22, the dielectric constant of the insulating coatings, and the opposing areas of the conductors of the first feed line 12 and the second feed line 22.

The configuration of the noise reduction circuit 30 will be described with reference to Figures 1 and 7. The noise reduction circuit 30 is electrically connected to the first feed line 12 and the second feed line 22, receives a first signal Sg1 from the first antenna 11 via the first feed line 12, receives a second signal Sg2 from the second antenna 21 via the second feed line 22, and performs processing to reduce the noise components contained in the first signal Sg1 using the second signal Sg2. The noise reduction circuit 30 of this embodiment includes a circuit that inverts the first signal Sg1 or the second signal Sg2 and then adds the first signal Sg1 and the second signal Sg2. Specific examples are described below.

As shown in FIG. 1, the noise reduction circuit 30 of this embodiment includes a first high-frequency amplifier 31, a second high-frequency amplifier 32, and an adder 33. The signal input terminal of the first high-frequency amplifier 31 is electrically connected to the other end of the first feeder 12 (the end opposite the first antenna 11). The first high-frequency amplifier 31 amplifies the first signal Sg1 transmitted from the first antenna 11 via the first feeder 12. The signal input terminal of the second high-frequency amplifier 32 is electrically connected to the other end of the second feeder 22 (the end opposite the second antenna 21). The second high-frequency amplifier 32 amplifies the second signal Sg2 transmitted from the second antenna 21 via the second feeder 22. Either the first high-frequency amplifier 31 or the second high-frequency amplifier 32 performs inverting amplification. The signal amplification factor of the second high-frequency amplifier 32 may be the same as the signal amplification factor of the first high-frequency amplifier 31. Alternatively, the ratio between the signal amplification factor of the first high-frequency amplifier 31 and the signal amplification factor of the second high-frequency amplifier 32 may be adjusted according to the ratio between the noise reception sensitivities of the first antenna 11 and the second antenna 21 so that the magnitude of the noise components contained in the first signal Sg1 and the second signal Sg2 are equivalent.

One signal input terminal of the adder 33 is electrically connected to the signal output terminal of the first high-frequency amplifier 31, and the other signal input terminal of the adder 33 is electrically connected to the signal output terminal of the second high-frequency amplifier 32. The adder 33 adds the first signal Sg1 amplified by the first high-frequency amplifier 31 and the second signal Sg2 amplified by the second high-frequency amplifier 32. As a result, the noise components contained in the first signal Sg1 are reduced by the noise components contained in the second signal Sg2. The signal output terminal of the adder 33 is electrically connected to the tuner 42 via the relay cable 41. The adder 33 provides the added signal to the tuner 42.

Note that specific examples of the noise reduction circuit 30 are not limited to those described above. For example, the noise reduction circuit 30 may include a circuit that outputs the difference between the first signal Sg1 and the second signal Sg2. Alternatively, the noise reduction circuit 30 may include a circuit that converts the first signal Sg1 and the second signal Sg2 into digital signals and calculates the difference between the digital values of the first signal Sg1 and the second signal Sg2.

As shown in FIG. 7 , the noise reduction circuit 30 has a circuit component 35. The antenna device 1 includes a wiring board 34 on which the circuit component 35 is mounted. The wiring board 34 includes a dielectric substrate and conductive pattern wiring portions provided on and inside the dielectric substrate. The circuit component 35 includes the first high-frequency amplifier 31, second high-frequency amplifier 32, and adder 33 described above (or another circuit that performs processing to reduce the noise components included in the first signal Sg1 using the second signal Sg2). The insulated wires of the first feeder line 12 and the insulated wires of the second feeder line 22 are connected to the wiring board 34 and are connected to the circuit component 35 via the pattern wiring portions within the wiring board 34.

The effects achieved by the antenna device 1 according to the present embodiment described above will now be explained. In the antenna device 1 according to the present embodiment, the first antenna 11 receives radio broadcast waves and outputs a first signal Sg1 that includes the radio broadcast waves and noise components. The second antenna 21 outputs a second signal Sg2 that mainly includes noise components (in other words, the ratio of noise components to radio broadcast waves is greater than that of the first signal Sg1). The first signal Sg1 and the second signal Sg2 are transmitted via the first feed line 12 and the second feed line 22, respectively, to the noise reduction circuit 30. The noise reduction circuit 30 uses the second signal Sg2 to reduce the noise components included in the first signal Sg1.

In addition, in the antenna device 1, the second conductor 20 has a capacitive coupling portion 24. The capacitive coupling portion 24 is capacitively coupled to at least a portion of the first conductor 10. The capacitive coupling portion 24 has the effect of bringing the phases of the signals, particularly noise components, transmitted through the first conductor 10 and the second conductor 20 closer together. Therefore, with the antenna device 1 of this embodiment, the phase difference between the noise components contained in the first signal Sg1 and the noise components contained in the second signal Sg2 can be reduced. This further reduces the noise components contained in the first signal Sg1. Furthermore, a structure that reduces the phase difference can be achieved with a simple configuration that simply capacitively couples the conductors, eliminating the need for a complex circuit configuration.

Figure 8 shows an example of a signal waveform output from the noise reduction circuit 30. Figure 9 shows, as a comparative example, an example of a signal waveform when noise components are not canceled. In Figures 8 and 9, the horizontal axis represents frequency (kHz), and the vertical axis represents signal level (dBμV). Note that the peak near 1100 kHz is a signal transmitted from outside the vehicle simulating a radio broadcast wave. The noise source is an inverter power supply installed inside the vehicle. Graph G1 shows the state when both the simulated signal source and the noise source are turned off, graph G2 shows the state when only the simulated signal source is turned on, and graph G3 shows the state when both the simulated signal source and the noise source are turned on. Comparing Figures 8 and 9 clearly shows that the antenna device 1 of this embodiment, which includes the capacitive coupling unit 24, significantly reduces the noise components contained in the signal waveform output from the noise reduction circuit 30.

As in this embodiment, the shape of the second antenna 21 may be different from the shape of the first antenna 11. In this case, a phase difference is likely to occur between the first signal Sg1 and the second signal Sg2, making the configuration of the antenna device 1 of this embodiment particularly useful.

As in this embodiment, the first antenna 11 is a glass antenna installed on the vehicle's window glass 51, and the second antenna 21 may include a conductive plate-like portion 25. In many cases, glass antennas are installed within a relatively large area AR on a large glass surface, such as a rear window. In contrast, the second antenna 21 is placed in a relatively small area where it is more difficult to receive radio broadcast waves than the first antenna 11, such as near the window glass 51 inside the metal body 52. Furthermore, the sensitivity of the second antenna 21 is likely to decrease due to the influence of the metal body 52. Even in such cases, by including the conductive plate-like portion 25 (capacitive loading plate) in the second antenna 21, the second antenna 21 can be made compact while still being given noise sensitivity equivalent to that of a glass antenna.

As in this embodiment, the noise reduction circuit 30 may include a circuit that inverts the first signal Sg1 or the second signal Sg2 and then adds the first signal Sg1 and the second signal Sg2. For example, with this configuration, the noise components contained in the first signal Sg1 can be reduced using the second signal Sg2.

As in this embodiment, the capacitive coupling portion 24 may be capacitively coupled to a midpoint of the first feed line 12. In this case, the above-described effects of the antenna device 1 can still be obtained.

The capacitive coupling portion 24 may include a flat plate 231 disposed opposite the upper surface of the terminal portion 13 of the first conductor 10, or, to further increase the capacitance value, may include a covering portion 23 that covers the terminal portion 13 of the first conductor 10 from at least three sides, as in this embodiment. In this case, the capacitance value of the capacitive coupling portion 24 can be increased to further reduce the phase difference between the two noise components.

As in this embodiment, the first power supply line 12 and the second power supply line 22 each have insulated wires, and at least a portion of the insulated wire of the second power supply line 22 may be arranged parallel to and adjacent to at least a portion of the insulated wire of the first power supply line 12. In this case, the capacitance value of the capacitive coupling unit 24 can be increased to further reduce the phase difference between the two noise components.

As in this embodiment, the first feed line 12 is arranged along the shortest path between the feed point (terminal portion 13) of the first antenna 11 and the noise reduction circuit 30, and the capacitive coupling portion 24 may include a portion arranged parallel to and adjacent to the first feed line 12 arranged along that path. In this case, the first feed line 12 can be shortened to suppress the effects of electromagnetic noise on the first feed line 12, while the capacitance value of the capacitive coupling portion 24 can be increased to effectively reduce the phase difference between the two noise components.

As in this embodiment, the receiving sensitivity of the second antenna 21 for radio broadcast waves may be equal to or less than the receiving sensitivity of the first antenna for radio broadcast waves minus, for example, 20 dB. While this varies slightly depending on the performance of the radio tuner, generally, an antenna receiving sensitivity (signal-to-noise ratio) of 10 dB results in a sound quality level where the demodulated audio is audible (but noise is present), while a receiving sensitivity of 20 dB results in a sound quality level where the demodulated audio is barely audible or inaudible. In this embodiment, the second signal Sg2 output from the second antenna 21 is subtracted from the first signal Sg1 output from the first antenna 11. Therefore, if the combined receiving sensitivity of the first antenna 11 and the second antenna 21, i.e., the value obtained by subtracting the receiving sensitivity of the second antenna 21 for radio broadcast waves from the receiving sensitivity of the first antenna 11 for radio broadcast waves, is 20 dB or more, a high sound quality level where noise is barely audible can be achieved. In other words, the receiving sensitivity of the radio broadcast waves of the antenna device 1 as a whole can be sufficiently increased.

[First Modification]
Next, a modified example of the antenna device 1 according to the above embodiment will be described. The antenna device according to this modified example differs from the above embodiment in the shape and arrangement of the second antenna 21. The other configurations of the antenna device, except for the shape and arrangement of the second antenna 21, are the same as the configuration of the antenna device 1 according to the above embodiment.

In this modified example, the second antenna 21 is installed in a location that is more susceptible to noise from vehicle noise sources than the first antenna 11; in other words, at a shorter distance from the vehicle noise source than the first antenna 11. The vehicle noise source is an electrical component or electrical equipment installed inside or outside the metal body 52. Noise sources installed outside the metal body 52 are, for example, equipment such as a large battery, high-voltage transmission cable, and voltage converter located on the bottom of the vehicle. Here, the bottom of the vehicle refers to the outer surface of the metal body 52 that faces the ground (in other words, the underside of the steel plate that makes up the floor).

In this way, by placing the second antenna 21 closer to the noise source than the first antenna 11, even if the size of the second antenna 21 is smaller than the size of the first antenna 11, the second antenna 21 can receive noise at a level equivalent to that received by the first antenna 11. Therefore, the S/N ratio of the second signal Sg2 output from the second antenna 21 is smaller than the S/N ratio of the first signal Sg1 output from the first antenna 11. As in the above embodiment, the receiving sensitivity of the second antenna 21 to radio broadcast waves is equal to or less than the value obtained by subtracting, for example, 20 dB from the receiving sensitivity of the first antenna 11 to radio broadcast waves. In other words, the receiving sensitivity of the second antenna 21 to radio broadcast waves is, for example, 10% or less of the receiving sensitivity of the first antenna 11 to radio broadcast waves.

Figure 10 is a diagram showing an example of the antenna device of this modified example mounted on a vehicle. Figure 11 is a diagram showing a cross section of the second antenna 21 of this modified example and the surrounding window glass 51 and metal body 52. In the example shown in Figures 10 and 11, the second antenna 21 is positioned on the outer surface of the vehicle's metal body 52 (the surface facing away from the passenger compartment) in an area close to the edge of the window glass 51. Furthermore, if the noise source is located at the bottom of the vehicle, the second antenna 21 is installed in a position closer to the bottom of the vehicle than the first antenna 11 (for example, below the rear window).

With this arrangement, radio broadcast waves from outside the vehicle are not blocked by the metal body 52 and reach the second antenna 21 in the same manner as the first antenna 11. Furthermore, noise waves from a noise source reach the second antenna 21, which is closer to the noise source than the first antenna 11, more significantly. According to the inventor's findings, if the noise source is located at the bottom of the vehicle and the second antenna 21 is the same size as the first antenna 11, the receiving sensitivity of the second antenna 21 for radio broadcast waves can be reduced to a value equal to or less than the receiving sensitivity of the first antenna 11 for radio broadcast waves minus 20 dB by setting the difference between the installation heights of the first antenna 11 and the second antenna 21 to 0.3 m or more.

Note that the location of the second antenna 21 is not limited to this, and it may be located elsewhere outside the metal body 52. Alternatively, if the noise source is located inside the metal body 52 (i.e., inside the vehicle cabin), the second antenna 21 may be located closer to the noise source within the vehicle cabin than the first antenna 11.

As shown in FIG. 10 , the second feeder line 22 in this modified example extends further from the sheath 23 toward the second antenna 21. The portion of the second feeder line 22 extending further from the sheath 23 toward the second antenna 21 is mainly laid inside the metal body 52. The second antenna 21 is connected to the sheath 23 via the second feeder line 22. If the wiring path of the second feeder line 22 is long, the second feeder line 22 may partially include a cable configured such that the conductor transmitting the second signal Sg2 is shielded at ground potential to avoid noise from other noise sources.

Figure 12 shows an example of the arrangement of the second antenna 21, illustrating the exterior of the rear of the vehicle. As indicated by the bold line in Figure 12, the second antenna 21 may include a portion, such as a linear portion 211, provided around the combination lamp 53 located below the rear window. In the illustrated example, the linear portion 211 is laid in a U-shape across the top surface of the combination lamp 53, the side of the combination lamp 53 farthest from the vehicle's exterior, and the bottom surface of the combination lamp 53. The linear portion 211 is, for example, an insulated electric wire (AV wire) in which a linear conductor is coated with a resin such as polyvinyl chloride. The linear portion 211 may be laid inside the plastic cover of the combination lamp 53 or outside the plastic cover of the combination lamp 53. The linear portion 211 may be connected to the second power supply line 22 on the top surface of the combination lamp 53 or on the bottom surface of the combination lamp 53.

The configuration of the second antenna 21 is not limited to the above example, and may include, in addition to or instead of the linear portion 211, one or more of the following components: sheet metal, conductive film, and conductive resin. Furthermore, the linear portion 211 is not limited to a U-shape, and may be arranged, for example, in a meandering shape.

The second antenna 21 generates a second electrical signal Sg2 that includes both noise components due to electromagnetic noise generated by electrical components and electrical equipment, and components due to radio broadcast waves. The second signal Sg2 includes noise components that are greater than those of the first signal Sg1. The second antenna 21 outputs the second signal Sg2 to the noise reduction circuit 30. The processing in the noise reduction circuit 30 is the same as in the above embodiment.

The effects achieved by the antenna device according to this modified example described above will now be explained. In the antenna device according to this modified example, the first antenna 11 outputs a first signal Sg1 that includes radio broadcast waves and noise components. The second antenna 21 outputs a second signal Sg2 that includes radio broadcast waves and noise components, and in which the ratio of the noise components to the radio broadcast waves is greater than that of the first signal Sg1. The first signal Sg1 and the second signal Sg2 are transmitted via the first feed line 12 and the second feed line 22, respectively, to the noise reduction circuit 30. The noise reduction circuit 30 uses the second signal Sg2 to reduce the noise components contained in the first signal Sg1.

In addition, in the antenna device of this modified example, the second conductor 20 also has a capacitive coupling portion 24. This reduces the phase difference between the noise components contained in the first signal Sg1 and the noise components contained in the second signal Sg2. This further reduces the noise components contained in the first signal Sg1. Furthermore, because a structure that reduces the phase difference can be achieved with a simple configuration that simply capacitively couples the conductors together, the circuit configuration does not need to be complicated.

Figure 13 shows an example of a measured signal waveform output from the noise reduction circuit 30. Figure 14 shows, as a comparative example, an example of a measured signal waveform when noise components are not canceled. In Figures 13 and 14, the horizontal axis represents frequency (kHz) and the vertical axis represents signal level (dBμV). Note that the peak near 1200 kHz is a signal transmitted from outside the vehicle simulating radio broadcast waves. The noise sources are a large battery, high-voltage transmission cable, and voltage converter installed at the bottom of the vehicle. Comparing Figures 13 and 14 makes it clear that in the antenna device of this modified example equipped with the capacitive coupling unit 24, the reception level of radio broadcast waves is maintained at the same level, while the noise components contained in the signal waveform output from the noise reduction circuit 30 are significantly reduced (specifically, by 10 dB).

As mentioned above, if the noise source is located at the bottom of the vehicle, the second antenna 21 may be installed closer to the bottom of the vehicle than the first antenna 11. In this case, the second antenna 21 can be installed in a location that is more susceptible to noise from the vehicle noise source than the first antenna 11.

As mentioned above, the first antenna 11 is a glass antenna installed on the rear windshield of the vehicle, and the second antenna 21 may include a linear portion 211 provided around the combination lamp 53 located below the rear windshield. In this case, the second antenna 21 can be made less noticeable on the vehicle's exterior and installed in a location that makes it easy to connect to the noise reduction circuit 30 inside the vehicle. Furthermore, by arranging the linear portion 211 along the periphery of the combination lamp 53, the capacity of the second antenna 21 can be increased, thereby improving reception sensitivity.

As mentioned above, the second antenna 21 may be located on the outside of the metal body 52. In this case, the second antenna 21 can be installed in a location that is more susceptible to noise from noise sources outside the vehicle than the first antenna 11.

As described above, the second power supply line 22 may partially include a cable having a configuration in which the conductor transmitting the second signal Sg2 is shielded at ground potential. Depending on the arrangement of the second antenna 21, the wiring path of the second power supply line 22 may be long. In particular, when the second antenna 21 is installed outside the metal body 52, the position at which the second power supply line 22 can be pulled into the vehicle interior is limited due to considerations such as vehicle rigidity and waterproofing, which tends to result in a long wiring path for the second power supply line 22. In such cases, noise from a noise source other than the noise source generating the noise input to the first antenna 11 or from another electrical component cable magnetically coupled to the second power supply line 22 may be superimposed on the second signal Sg2 propagating through the second power supply line 22. In this case, the noise contained in the second signal Sg2 will be different from the noise contained in the first signal Sg1. In contrast, by using the above cable for the portion of the second power supply line 22 that is susceptible to noise from other noise sources, it is possible to reduce noise from other noise sources or electrical equipment cables that is superimposed on the second signal Sg2. Note that the longer the wiring path of the above cable, the more the noise that should be included in the second signal Sg2 is attenuated, so it is preferable that the second power supply line 22 only partially includes the above cable in necessary locations.

[Second Modification]
15A and 15B are cross-sectional views showing an example of the configuration of the second antenna 21 and its vicinity according to a second modification. The antenna device of this modification further includes a canopy portion 29 in addition to the configuration of the first modification. The canopy portion 29 covers at least the upper portion of the second antenna 21 to block radio broadcast waves. In this modification, the noise source is located at the bottom of the vehicle.

Specifically, the eaves portion 29 includes a conductive material and is short-circuited to a portion having a reference potential (e.g., the metal body 52). The eaves portion 29 protrudes horizontally from the metal body 52 toward the outside of the vehicle. When viewed from above, the eaves portion 29 overlaps the entire second antenna 21. The eaves portion 29 may include one or more conductive materials selected from the group consisting of sheet metal, metal film, and conductive resin. The conductive material may spread seamlessly across the entire surface of the eaves portion 29, or may spread in a mesh-like pattern. As shown in FIG. 15 , the eaves portion 29 may have a curved portion 291 that bends downward at its tip. The curved portion 291 enables more effective shielding of radio broadcast waves.

In this modified example, the second antenna 21 has difficulty receiving radio broadcast waves, so the ratio of noise components to radio broadcast waves in the second signal Sg2 becomes even greater than that in the first signal Sg1. Therefore, the noise components contained in the first signal Sg1 can be more effectively reduced using the second signal Sg2. Note that the second antenna 21 may be arranged to extend along the metal body 52 as shown in part (a) of Figure 15, or may be arranged to extend in a direction intersecting the metal body 52 as shown in part (b) of Figure 15.

[Third Modification]
16 is a plan view showing the configuration of a wiring board 34A according to a third modification. The antenna device of this modification includes a wiring board 34A instead of the wiring board 34 of the above-described embodiment, the first modification, or the second modification. Circuit components 35 (see FIG. 7 ) are mounted on the wiring board 34A. The wiring board 34A has a hole 341 through which a conductor, the coating of which is removed at the tip of the insulated wire constituting the first power supply line 12, is inserted, and a protrusion 343 around which the conductor is wound and fixed. In addition, the wiring board 34A has a hole 342 through which a conductor, the coating of which is removed at the tip of the insulated wire constituting the second power supply line 22, is inserted, and a protrusion 344 around which the conductor is wound and fixed.

The first power supply line 12 includes a pattern wiring portion 36 provided on the wiring board 34A. One end of the pattern wiring portion 36 forms a circular pattern 36a surrounding the protrusion 343. The conductor exposed from the tip of the insulated wire that makes up the first power supply line 12 is in conductive contact with the pattern 36a. The other end of the pattern wiring portion 36 forms a terminal 36b that is electrically connected to the circuit component 35.

The second power supply line 22 includes a pattern wiring portion 37 provided on the wiring board 34A. One end of the pattern wiring portion 37 forms a circular pattern 37a surrounding the protrusion 344. The conductor exposed from the tip of the insulated wire that forms the second power supply line 22 is in conductive contact with the pattern 37a. A chip capacitor 38 is connected between the pattern 36a and the pattern 37a. The other end of the pattern wiring portion 37 forms a terminal 37b that is electrically connected to the circuit component 35.

Pattern wiring portion 37 is included in capacitive coupling section 24 and is capacitively coupled to pattern wiring portion 36. Specifically, pattern wiring portion 37 is arranged along (e.g., parallel to) pattern wiring portion 36. Furthermore, pattern wiring portions 36 and 37 bend once in the direction opposite to the direction toward circuit component 35 so that they run parallel to each other for a longer distance, and then return toward circuit component 35. The distance between pattern wiring portion 36 and pattern wiring portion 37 is, for example, 1.6 mm or less. Furthermore, the sum (L1 + L2) of the parallel running length L1 of pattern wiring portion 36 and pattern wiring portion 37 and the parallel running length L2 of first power supply line 12 and second power supply line 22 is, for example, 50 mm or less.

As in this modification, the first power supply line 12 and the second power supply line 22 may each include pattern wiring portions 36 and 37 provided on the wiring board 34A. The capacitive coupling portion 24 may also include pattern wiring portion 37 of the second power supply line 22, which provides capacitive coupling with pattern wiring portion 36 of the first power supply line 12. In this case, stable capacitive coupling can be achieved by pattern wiring portions 36 and 37 provided on the wiring board 34A.

Second Embodiment
Fig. 17 is a block diagram showing a schematic configuration of an antenna device 1A according to the second embodiment. As shown in Fig. 17, the antenna device 1A of this embodiment includes a first conductor 10, a second conductor 20A, a third conductor 20B, a noise reduction circuit 30A, a relay cable 41, and a tuner 42. The configurations of the first conductor 10, the relay cable 41, and the tuner 42 are the same as those of the first embodiment described above.

The second conductor 20A has a second antenna 21A, a second power feeder (feeder line) 22A, and a sheath 23A. The second antenna 21A has a configuration similar to that of the second antenna 21 in the first embodiment. That is, the second antenna 21A is installed in a location in the vehicle where it is more difficult to receive radio broadcast waves than the first antenna 11. The second antenna 21A outputs a second signal Sg21 that mainly contains noise components due to electromagnetic noise generated from electrical components and electrical equipment inside the vehicle (in other words, the proportion of noise components to radio broadcast waves is greater than that of the first signal Sg1). The second antenna 21 outputs the second signal Sg21 to the noise reduction circuit 30A. The second power feeder 22A has a configuration similar to that of the second power feeder 22 in the first embodiment. The second power feeder 22A transmits the second signal Sg21 output from the second antenna 21A. The sheath 23A has a configuration similar to that of the sheath 23 in the first embodiment.

The third conductor 20B has a third antenna 21B, a third feeder line (feeder line) 22B, and a covering portion 23B. The third antenna 21B has a configuration similar to that of the second antenna 21 of the first modified example. That is, the third antenna 21B is installed in a location more susceptible to noise from vehicle noise sources than the first antenna 11. The third antenna 21B generates an electrical third signal Sg22 that includes both noise components due to electromagnetic noise generated from electrical components and electrical equipment and components due to radio broadcast waves. In the third signal Sg22, the ratio of noise components to radio broadcast waves is greater than in the first signal Sg1. The third antenna 21B outputs the third signal Sg22 to the noise reduction circuit 30A. The third feeder line 22B has a configuration similar to that of the second feeder line 22 of the first modified example. The third feeder line 22B transmits the third signal Sg22 output from the third antenna 21B. Covering portion 23B has the same configuration as covering portion 23 in the first embodiment. Note that covering portions 23A and 23B may be formed by two separate portions of covering portion 23 in the first embodiment.

In this embodiment, the first power supply line 12, terminal portion 13, second power supply line 22A, coating portion 23A, third power supply line 22B, and coating portion 23B constitute a noise phase tuning portion 27A that brings the phase of the noise components contained in the second signal Sg21 and the third signal Sg22 closer to (tunes) the phase of the noise components contained in the first signal Sg1. The coating portions 23A and 23B, and the second power supply line 22A and the third power supply line 22B constitute a capacitive coupling portion that capacitively couples with at least a portion of the first conductor 10.

The noise reduction circuit 30A is electrically connected to the first feed line 12, the second feed line 22A, and the third feed line 22B. The noise reduction circuit 30A receives a first signal Sg1 from the first antenna 11 via the first feed line 12, a second signal Sg21 from the second antenna 21A via the second feed line 22A, and a third signal Sg22 from the third antenna 21B via the third feed line 22B. The noise reduction circuit 30A uses the second signal Sg21 and the third signal Sg22 to reduce the noise components contained in the first signal Sg1. The noise reduction circuit 30A of this embodiment includes a circuit that inverts the first signal Sg1 or inverts both the second signal Sg21 and the third signal Sg22, and then adds the first signal Sg1 to the second signal Sg21 and the third signal Sg22.

As shown in FIG. 17, the noise reduction circuit 30A of this embodiment has a first high-frequency amplifier 31, a second high-frequency amplifier 32A, a third high-frequency amplifier 32B, and an adder 33A. The signal input terminal of the first high-frequency amplifier 31 is electrically connected to the other end of the first feeder line 12 (the end opposite the first antenna 11). The first high-frequency amplifier 31 amplifies the first signal Sg1 transmitted from the first antenna 11 via the first feeder line 12. The signal input terminal of the second high-frequency amplifier 32A is electrically connected to the other end of the second feeder line 22A (the end opposite the second antenna 21A). The second high-frequency amplifier 32A amplifies the second signal Sg21 transmitted from the second antenna 21A via the second feeder line 22A. The signal input terminal of the third high-frequency amplifier 32B is electrically connected to the other end of the third feeder line 22B (the end opposite the third antenna 21B). The third high-frequency amplifier 32B amplifies the third signal Sg22 transmitted from the third antenna 21B via the third feeder line 22B. The first high-frequency amplifier 31 performs inverting amplification, or both the second high-frequency amplifier 32A and the third high-frequency amplifier 32B perform inverting amplification. In this case, the ratio of the signal amplification factors of the first high-frequency amplifier 31, the second high-frequency amplifier 32A, and the third high-frequency amplifier 32B may be adjusted according to the ratio of the noise receiving sensitivities of the first antenna 11, the second antenna 21A, and the third antenna 21B so that the magnitude of the noise component included in the first signal Sg1 is equivalent to the sum of the magnitude of the noise component included in the second signal Sg21 and the magnitude of the noise component included in the third signal Sg22.

One signal input terminal of the adder 33A is electrically connected to the signal output terminal of the first high-frequency amplifier 31. Another signal input terminal of the adder 33A is electrically connected to the signal output terminal of the second high-frequency amplifier 32A. A further signal input terminal of the adder 33A is electrically connected to the signal output terminal of the third high-frequency amplifier 32B. The adder 33A adds the first signal Sg1 amplified by the first high-frequency amplifier 31, the second signal Sg21 amplified by the second high-frequency amplifier 32A, and the third signal Sg22 amplified by the third high-frequency amplifier 32B. As a result, the noise components contained in the first signal Sg1 are reduced by the noise components contained in the second signal Sg21 and the third signal Sg22. The signal output terminal of the adder 33A is electrically connected to the tuner 42 via the relay cable 41. The adder 33A provides the added signal to the tuner 42.

Note that specific examples of the noise reduction circuit 30A are not limited to those described above. For example, the noise reduction circuit 30A may include a circuit that outputs the difference between the first signal Sg1 and the second and third signals Sg21 and Sg22. Alternatively, the noise reduction circuit 30A may include a circuit that converts the first signal Sg1, the second signal Sg21, and the third signal Sg22 into digital signals and calculates the difference between the digital value of the first signal Sg1 and the digital values of the second and third signals Sg21 and Sg22.

In the antenna device 1A of this embodiment, the first antenna 11 receives radio broadcast waves and outputs a first signal Sg1 containing radio broadcast waves and noise components. The second antenna 21A and third antenna 21B output a second signal Sg21 and a third signal Sg22, respectively, in which the ratio of noise components to radio broadcast waves is greater than that of the first signal Sg1. The first signal Sg1, second signal Sg21, and third signal Sg22 are transmitted via the first feed line 12, second feed line 22A, and third feed line 22B, respectively, to the noise reduction circuit 30A. The noise reduction circuit 30A uses the second signal Sg21 and third signal Sg22 to reduce the noise components contained in the first signal Sg1.

In addition, in the antenna device 1A of this embodiment, the second conductor 20A and the third conductor 20B have capacitive coupling portions that capacitively couple with at least a portion of the first conductor 10. The capacitive coupling portions have the effect of bringing the phases of the signals, particularly noise components, transmitted through the first conductor 10, the second conductor 20A, and the third conductor 20B closer together. Therefore, the antenna device 1A of this embodiment can reduce the phase difference between the noise components contained in the output signal of the first antenna 11 (antenna for radio broadcast waves) and the noise components contained in the output signals of the second antenna 21A and the third antenna 21B (antennas for noise pickup). Furthermore, because a structure that reduces the phase difference can be achieved with a simple configuration that simply capacitively couples the conductors, a complex circuit configuration is not required.

The vehicle-mounted antenna device according to the present disclosure is not limited to the above-described embodiments and variations, and various other modifications are possible. For example, in the above embodiments, an example was described in which the shape of the second antenna 21 is different from the shape of the first antenna 11. However, the shape of the second antenna may be the same as the shape of the first antenna. In addition, in the above embodiments, an example was described in which the first antenna 11 is a glass antenna. However, the first antenna may be an antenna other than a glass antenna. In addition, in the above embodiments, an example was described in which the second antenna 21 includes a plate-shaped portion 25 (capacitance loading plate). However, the second antenna may be an antenna without a capacitance loading plate. In addition, in the above embodiments, an example was described in which the plate-shaped portion 25 is connected to the covering portion 23 via the plate-shaped portion 26. However, the plate-shaped portion 25 may be connected to the covering portion 23 via an electric wire such as a wire harness, or may be connected to the covering portion 23 using capacitive coupling in which metal plates are arranged in a planar configuration.

In addition, in the above embodiment, an example was shown in which the capacitive coupling portion 24 included the covering portion 23 and a portion of the second feed line 22 that is arranged parallel to and adjacent to the first feed line 12, but the capacitive coupling portion may include only one of these. Furthermore, the capacitive coupling portion may include another portion that capacitively couples with the first conductor, together with or instead of one or both of the covering portion 23 and the second feed line 22. For example, the capacitive coupling portion may include a portion of the second antenna, and a portion of the second antenna may be capacitively coupled with a portion of the first antenna.

1, 1A...(vehicle mounted) antenna device, 10...first conductor, 11...first antenna, 12...first feeder line, 13...terminal part, 14...terminal holding part, 14a...bottom surface, 14b...recessed part, 14f...front surface, 20, 20A...second conductor, 20B...third conductor, 21 , 21A...Second antenna, 21B...Third antenna, 22, 22A...Second feeder line, 22B...Third feeder line, 23, 23A, 23B...Coating portion, 24...Capacitive coupling portion, 25, 26...Plate portion, 27, 27A...Noise phase tuning portion, 29...Eave portion, 30, 30 A...noise reduction circuit, 31...first high-frequency amplifier, 32, 32A...second high-frequency amplifier, 32B...third high-frequency amplifier, 33, 33A...adder, 34, 34A...wiring board, 35...circuit component, 36, 37...pattern wiring portion, 41...relay cable, 42...tuner, 51...window glass, 52...metal body, 211...linear portion, 231...flat plate, 291...curved portion, 341, 342...holes, 343, 344...protrusions, AR...area, Sg1...first signal, Sg2, Sg21...second signal, Sg22...third signal.

Claims (18)

An antenna device mounted on a vehicle,
a first antenna installed in the vehicle, receiving radio broadcast waves arriving from outside the vehicle and outputting a first signal; and a first conductor having a first feeder line electrically connected to the first antenna and transmitting the first signal;
a second antenna that is installed in a location that is less able to receive the radio broadcast waves than the first antenna or that is more susceptible to noise from a noise source in the vehicle than the first antenna , and that outputs a second signal; and a second conductor that is electrically connected to the second antenna and has a second feeder line that transmits the second signal.
a noise reduction circuit electrically connected to the first feed line and the second feed line, receiving the first signal from the first antenna via the first feed line and the second signal from the second antenna via the second feed line, and performing processing to reduce noise components included in the first signal using the second signal;
Equipped with
The second conductor has a capacitive coupling portion that performs capacitive coupling with at least a part of the first conductor without passing through the vehicle . An antenna device mounted on a vehicle,
a first antenna installed in the vehicle, receiving radio broadcast waves arriving from outside the vehicle and outputting a first signal; and a first conductor having a first feeder line electrically connected to the first antenna and transmitting the first signal;
a second antenna that is installed in a location that is less able to receive the radio broadcast waves than the first antenna or that is more susceptible to noise from a noise source in the vehicle than the first antenna, and that outputs a second signal; and a second conductor that is electrically connected to the second antenna and has a second feeder line that transmits the second signal.
a noise reduction circuit electrically connected to the first feed line and the second feed line, receiving the first signal from the first antenna via the first feed line and the second signal from the second antenna via the second feed line, and performing processing to reduce noise components included in the first signal using the second signal;
Equipped with
the second conductor has a capacitive coupling portion that is capacitively coupled to at least a part of the first conductor;
The capacitive coupling portion is capacitively coupled to a midpoint of the first feeder line. The in-vehicle antenna device according to claim 2 , wherein the capacitive coupling portion includes a portion that covers the terminal portion of the first conductor from at least three sides. An antenna device mounted on a vehicle,
a first antenna installed in the vehicle, receiving radio broadcast waves arriving from outside the vehicle and outputting a first signal; and a first conductor having a first feeder line electrically connected to the first antenna and transmitting the first signal;
a second antenna that is installed in a location that is less able to receive the radio broadcast waves than the first antenna or that is more susceptible to noise from a noise source in the vehicle than the first antenna, and that outputs a second signal; and a second conductor that is electrically connected to the second antenna and has a second feeder line that transmits the second signal.
a noise reduction circuit electrically connected to the first feed line and the second feed line, receiving the first signal from the first antenna via the first feed line and the second signal from the second antenna via the second feed line, and performing processing to reduce noise components included in the first signal using the second signal;
Equipped with
the second conductor has a capacitive coupling portion that is capacitively coupled to at least a part of the first conductor;
the first power supply line and the second power supply line each include an insulated wire;
At least a portion of the insulated wire of the second power feeder is disposed parallel to and adjacent to at least a portion of the insulated wire of the first power feeder . An antenna device mounted on a vehicle,
a first antenna installed in the vehicle, receiving radio broadcast waves arriving from outside the vehicle and outputting a first signal; and a first conductor having a first feeder line electrically connected to the first antenna and transmitting the first signal;
a second antenna that is installed in a location that is less able to receive the radio broadcast waves than the first antenna or that is more susceptible to noise from a noise source in the vehicle than the first antenna, and that outputs a second signal; and a second conductor that is electrically connected to the second antenna and has a second feeder line that transmits the second signal.
a noise reduction circuit electrically connected to the first feed line and the second feed line, receiving the first signal from the first antenna via the first feed line and the second signal from the second antenna via the second feed line, and performing processing to reduce noise components included in the first signal using the second signal;
Equipped with
the second conductor has a capacitive coupling portion that is capacitively coupled to at least a part of the first conductor;
the first feed line is disposed on a path that is the shortest between the feed point of the first antenna and the noise reduction circuit;
The capacitive coupling portion includes a portion disposed in parallel to and adjacent to the first feed line disposed in the path . An antenna device mounted on a vehicle,
a first antenna installed in the vehicle, receiving radio broadcast waves arriving from outside the vehicle and outputting a first signal; and a first conductor having a first feeder line electrically connected to the first antenna and transmitting the first signal;
a second antenna that is installed in a location that is less able to receive the radio broadcast waves than the first antenna or that is more susceptible to noise from a noise source in the vehicle than the first antenna, and that outputs a second signal; and a second conductor that is electrically connected to the second antenna and has a second feeder line that transmits the second signal.
a noise reduction circuit electrically connected to the first feed line and the second feed line, receiving the first signal from the first antenna via the first feed line and the second signal from the second antenna via the second feed line, and performing processing to reduce noise components included in the first signal using the second signal;
a wiring board on which circuit components for performing the processing are mounted;
Equipped with
the second conductor has a capacitive coupling portion that is capacitively coupled to at least a part of the first conductor;
The first feeder line and the second feeder line include pattern wiring portions provided on the wiring board. The in-vehicle antenna device according to claim 6 , wherein the capacitive coupling portion includes the pattern wiring portion of the second feeder line that is capacitively coupled with the pattern wiring portion of the first feeder line. The vehicle-mounted antenna device according to any one of claims 1 to 7 , wherein the second antenna is installed on an inner surface of a metal body of the vehicle at a location where it is more difficult to receive the radio broadcast waves than the first antenna. An antenna device mounted on a vehicle,
a first antenna installed in the vehicle, receiving radio broadcast waves arriving from outside the vehicle and outputting a first signal; and a first conductor having a first feeder line electrically connected to the first antenna and transmitting the first signal;
a second antenna that is installed in a location that is more susceptible to noise from a noise source in the vehicle than the first antenna and that outputs a second signal; and a second conductor that has a second feeder line that is electrically connected to the second antenna and transmits the second signal;
a noise reduction circuit electrically connected to the first feed line and the second feed line, receiving the first signal from the first antenna via the first feed line and the second signal from the second antenna via the second feed line, and performing processing to reduce noise components included in the first signal using the second signal;
Equipped with
the second conductor has a capacitive coupling portion that is capacitively coupled to at least a part of the first conductor;
the noise source is located under the vehicle;
The second antenna is installed at a position closer to the bottom of the vehicle than the first antenna. 10. The in-vehicle antenna device according to claim 9, wherein the first antenna is a glass antenna installed on a rear window of the vehicle, and the second antenna includes a linear portion provided around a combination lamp located below the rear window. An antenna device mounted on a vehicle,
a first antenna installed in the vehicle, receiving radio broadcast waves arriving from outside the vehicle and outputting a first signal; and a first conductor having a first feeder line electrically connected to the first antenna and transmitting the first signal;
a second antenna that is installed in a location that is more susceptible to noise from a noise source in the vehicle than the first antenna and that outputs a second signal; and a second conductor that has a second feeder line that is electrically connected to the second antenna and transmits the second signal;
a noise reduction circuit electrically connected to the first feed line and the second feed line, receiving the first signal from the first antenna via the first feed line and the second signal from the second antenna via the second feed line, and performing processing to reduce noise components included in the first signal using the second signal;
Equipped with
the second conductor has a capacitive coupling portion that is capacitively coupled to at least a part of the first conductor;
the noise source is located under the vehicle;
The vehicle -mounted antenna device further comprises a canopy portion that covers at least an upper portion of the second antenna to block the radio broadcast waves. An antenna device mounted on a vehicle,
a first antenna installed in the vehicle, receiving radio broadcast waves arriving from outside the vehicle and outputting a first signal; and a first conductor having a first feeder line electrically connected to the first antenna and transmitting the first signal;
a second antenna that is installed in a location that is more susceptible to noise from a noise source in the vehicle than the first antenna and that outputs a second signal; and a second conductor that has a second feeder line that is electrically connected to the second antenna and transmits the second signal;
a noise reduction circuit electrically connected to the first feed line and the second feed line, receiving the first signal from the first antenna via the first feed line and the second signal from the second antenna via the second feed line, and performing processing to reduce noise components included in the first signal using the second signal;
Equipped with
the second conductor has a capacitive coupling portion that is capacitively coupled to at least a part of the first conductor;
The second feeder line includes a cable having a conductor for transmitting the second signal and a shielded cable surrounding the conductor at a ground potential. The vehicle-mounted antenna device according to any one of claims 1 to 7 and 9 to 12 , wherein the second antenna is arranged outside the metal body in a location more susceptible to noise from noise sources in the vehicle than the first antenna . The in-vehicle antenna device according to any one of claims 1 to 7 and 9 to 12, wherein the receiving sensitivity of the second antenna to the radio broadcast wave is equal to or less than a value obtained by subtracting 20 dB from the receiving sensitivity of the first antenna to the radio broadcast wave. 13. The vehicle-mounted antenna device according to claim 1 , wherein the second antenna has a shape different from that of the first antenna. The in-vehicle antenna device according to any one of claims 1 to 7 and 9 to 12, wherein the first antenna is a glass antenna installed on a window glass of the vehicle, and the second antenna includes a conductive plate-like portion. The in-vehicle antenna device according to any one of claims 1 to 7 and 9 to 12, wherein the noise reduction circuit includes a circuit that inverts the first signal or the second signal and then adds the first signal and the second signal. An antenna device mounted on a vehicle,
a first antenna installed in the vehicle, receiving radio broadcast waves arriving from outside the vehicle and outputting a first signal; and a first conductor having a first feeder line electrically connected to the first antenna and transmitting the first signal;
a second antenna that is installed in a location where it is more difficult to receive the radio broadcast wave than the first antenna and outputs a second signal; and a second conductor that has a second feeder line that is electrically connected to the second antenna and transmits the second signal;
a third antenna that is installed in a location that is more susceptible than the first antenna to noise from a noise source located outside the metal body of the vehicle and that outputs a third signal; and a third conductor that is electrically connected to the third antenna and has a third feeder line that transmits the third signal.
a noise reduction circuit electrically connected to the first feed line, the second feed line, and the third feed line, receiving the first signal from the first antenna via the first feed line, receiving the second signal from the second antenna via the second feed line, and receiving the third signal from the third antenna via the third feed line, and performing processing to reduce noise components included in the first signal using the second signal and the third signal;
Equipped with
The second conductor and the third conductor have capacitive coupling portions that are capacitively coupled with at least a portion of the first conductor.