JP7308312B2 - real-time transceiver - Google Patents

Description

The present disclosure relates to a real-time transmitting/receiving device that includes a transmitting antenna and a receiving antenna and simultaneously transmits and receives electromagnetic waves with frequencies in the millimeter wave band or higher, and in particular, the electromagnetic waves transmitted by the transmitting antenna are directly received by the receiving antenna. The present invention relates to a real-time transmitter/receiver that suppresses noise generation.

Radio waves called centimeter waves having a frequency band of several gigahertz (GHz) are used in mobile communications such as mobile phones, wireless LANs, automatic toll collection systems (ETC), and the like.

In addition, by receiving the reflected wave of the electromagnetic wave transmitted from the transmitting antenna by the object to be measured by the receiving antenna and measuring the distance from the object to be measured, the position of the object can be specified and the movement of the object can be detected. Radar systems that detect

As a device used for such data communication or radar, it is equipped with a transmitting antenna and a receiving antenna, and transmits electromagnetic waves from the transmitting antenna and receives electromagnetic waves at the receiving antenna at the same time. Techniques for performing processing have been proposed (see Patent Documents 1 and 2).

JP-A-9-326630 JP-A-5-341042

In recent years, wireless communication using a frequency of 60 gigahertz has been planned in order to make it possible to further increase the capacity of data to be transmitted. The use of millimeter-wave radar having frequencies in the so-called millimeter-wave band (30 to 300 gigahertz) is being promoted. Further, as a high-frequency radio wave exceeding the millimeter wave band, research is also progressing on a technology that uses radio waves having frequencies in the terahertz band up to 3 terahertz (THz).

In such a technology using electromagnetic waves of a high frequency of millimeter wave band or higher, in a transmitting/receiving device provided with a transmitting antenna and a receiving antenna, if the receiving antenna directly receives the electromagnetic wave transmitted by the transmitting antenna, the other device may It becomes noise in electromagnetic waves that should be received by the receiving antenna, such as transmitted electromagnetic waves and electromagnetic waves reflected by objects, and reduces the accuracy of high-speed data communication and accurate object position detection by radar. cause.

The present disclosure solves the above-described conventional problems, and in a real-time transmitting/receiving device that transmits/receives electromagnetic waves with a high frequency in the millimeter wave band or higher in real time, noise is generated by directly receiving the electromagnetic waves transmitted by the transmitting antenna. It is an object of the present invention to obtain a real-time transmission/reception device capable of suppressing the transmission and reception of electromagnetic waves with high accuracy.

In order to solve the above problems, the real-time transmission/reception device disclosed in the present application is a real-time transmission/reception device that includes a transmission antenna and a reception antenna and simultaneously performs transmission and reception using electromagnetic waves having a frequency in the millimeter wave band or higher. An electromagnetic wave absorber is arranged between the arrangement position of the transmitting antenna and the arrangement position of the receiving antenna, and the receiving antenna absorbs the reflected wave of the electromagnetic wave transmitted from the transmitting antenna reflected on the surface of the object to be measured. The electromagnetic wave absorber contains a magnetic iron oxide powder that magnetically resonates at a frequency of a millimeter wave band or higher and an organic material binder, and the distance D between the antenna element of the transmitting antenna and the electromagnetic wave absorber is the above It is characterized by satisfying the relationship D>(λ/2π) with respect to the wavelength λ of the electromagnetic wave absorbed by the electromagnetic wave absorber.

In the real-time transmitting/receiving device sheet disclosed in the present application, an electromagnetic wave absorber that absorbs electromagnetic waves of frequencies in the millimeter wave band or higher is placed between the transmitting antenna and the receiving antenna with a predetermined distance D from the antenna element of the transmitting antenna. are placed. Therefore, the electromagnetic wave absorber absorbs the electromagnetic waves radiated from the transmitting antenna toward the receiving antenna, and the noise in the received signal received by the receiving antenna can be reduced, enabling highly accurate transmission and reception of electromagnetic waves. A real-time transceiver can be implemented.

It is a perspective view for explaining the basic configuration of the radar device according to the present embodiment. FIG. 4 is a diagram showing the relationship between the distance from a transmitting antenna and the wave impedance of transmitted electromagnetic waves; FIG. 3 is a diagram for explaining the size and planar arrangement position of an electromagnetic wave absorber with respect to the arrangement positions of a transmitting antenna and a receiving antenna; FIG. 4 is a diagram for explaining the size of an electromagnetic wave absorber in the height direction with respect to the heights of a transmitting antenna and a receiving antenna; FIG. 11 is another diagram for explaining the size of the electromagnetic wave absorber in the height direction with respect to the heights of the transmitting antenna and the receiving antenna;

A real-time transmitting/receiving device disclosed in the present application is a real-time transmitting/receiving device that includes a transmitting antenna and a receiving antenna, and performs simultaneous transmission and reception using electromagnetic waves having a frequency in the millimeter wave band or higher, wherein the transmitting antenna is arranged. An electromagnetic wave absorber that absorbs electromagnetic waves having a frequency of a millimeter wave band or higher is disposed between the position and the position where the receiving antenna is arranged, and a distance D between the antenna element of the transmitting antenna and the electromagnetic wave absorber is the electromagnetic wave. The relationship D>(λ/2π) is satisfied with respect to the wavelength λ of the electromagnetic wave absorbed by the absorber.

By doing so, in the real-time transmitting/receiving device disclosed in the present application, the electromagnetic wave absorber absorbs electromagnetic waves emitted from the transmitting antenna toward the receiving antenna. In particular, the distance D between the antenna element of the transmitting antenna and the electromagnetic wave absorber satisfies the relationship D>(λ/2π) with respect to the wavelength λ of the electromagnetic wave absorbed by the electromagnetic wave absorber. Reducing surface reflections can effectively reduce the electromagnetic waves transmitted by the transmitting antenna and received by the receiving antenna directly. As a result, noise contained in the electromagnetic wave received by the receiving antenna can be suppressed, and highly accurate data communication and radar detection can be performed.

In the real-time transmitting/receiving apparatus disclosed in the present application, it is preferable that the distance D between the antenna element of the transmitting antenna and the electromagnetic wave absorber further satisfies the relationship D<(λ/π). By doing so, the electromagnetic waves radially transmitted from the transmitting antenna can be effectively absorbed by the electromagnetic wave absorber, and the noise of the electromagnetic waves received by the receiving antenna can be reduced.

Moreover, it is preferable that the electromagnetic wave absorber contains magnetic iron oxide that magnetically resonates at frequencies in the millimeter wave band or higher. By including magnetic iron oxide that magnetically resonates at frequencies above the millimeter wave band, the electromagnetic waves incident on the electromagnetic wave absorber can be converted into heat and absorbed. An electromagnetic wave absorber having a desired shape can be arranged between the transmitting antenna and the receiving antenna according to the position and size of the antenna and the position and size of the receiving antenna.

In this case, it is preferable that the electromagnetic wave absorber further contains a binder made of a non-conductive organic material. By doing so, the volume content of magnetic iron oxide that absorbs electromagnetic waves in the electromagnetic wave absorber can be adjusted, and the electromagnetic waves transmitted from the transmitting antenna can be efficiently absorbed. In addition, since the magnetic iron oxide powder is contained in the organic material binder, the electromagnetic wave absorber can be provided with elasticity and flexibility, and the electromagnetic wave absorber can be easily arranged in a desired shape. can be done.

Furthermore, it is preferable that the electromagnetic wave absorber is arranged so that the antenna element of the receiving antenna cannot be seen from the antenna element of the transmitting antenna. By doing so, it is possible to suppress direct incidence of the electromagnetic wave radiated from the transmitting antenna to the receiving antenna according to the size, shape, and arrangement position of each of the transmitting antenna and the receiving antenna.

The real-time transmitting/receiving apparatus disclosed in the present application can be implemented as a radar apparatus in which the receiving antenna receives reflected waves of electromagnetic waves transmitted from the transmitting antenna that are reflected by an object.

Hereinafter, the real-time transmitting/receiving apparatus disclosed in the present application will be described with reference to the drawings, taking as an example a radar apparatus that accurately measures the position of an object to be measured using electromagnetic waves in the millimeter wave band.

(Embodiment)
FIG. 1 is a perspective view for explaining a schematic configuration of a radar device according to this embodiment.

As shown in FIG. 1, the radar device 100 according to this embodiment has a transmitting antenna 20, a receiving antenna 30, and an electromagnetic wave absorber 40 mounted on a circuit board 10. FIG. Further, as shown in FIG. 1, an operating circuit unit 50 of the radar device 100 is arranged on the back side of the circuit board 10 of the radar device 100, and inputs and outputs of signals and operating power to the operating circuit unit 50 are provided. An input/output terminal 60 is arranged at the end of the circuit board 10 . In order to avoid complicating the drawing, illustration of a housing constituting the outer shell of the radar device 100 is omitted.

In the radar device 100 described in this embodiment, electromagnetic waves in the millimeter wave band with a frequency of 76 to 77 GHz are used as the electromagnetic waves transmitted from the transmission antenna 20 and received by the reception antenna 30 .

The circuit board 10 serves as the base of the radar device 100, and a normal hard board (rigid board) such as a bakelite board, an epoxy board, or a ceramics board can be used. Also, it is possible to employ a so-called flexible substrate having flexibility such as polyimide so that the entire circuit substrate 10 can be bent. It is preferable that at least a part of the flexible substrate is provided with a supporting substrate made of paper, resin, glass or other hard material.

In FIG. 1, only one circuit board 10 is shown for the sake of convenience, but the number of circuit boards 10 constituting the radar device 100 is not limited to one, and necessary electronic circuit components are mounted on two or more circuit boards. can be installed. Although not shown in FIG. 1, the radar device 100 itself can be provided with an image display device for displaying the detection result of the radar device 100. In this case, the image display device and the image display signal processing circuit can be provided. can be configured to include another circuit board or the like on which is mounted.

The transmitting antenna 20 is arranged on one surface of the circuit board 10 and transmits a predetermined transmission signal.

In the radar device 100 of the present embodiment, a grounded monopole antenna (λ/4) is adopted as the antenna element 21 of the transmission antenna 20, and a predetermined number of antenna elements 21 are arranged in a line in a resin frame. are placed. The number of antenna elements 21 and the arrangement intervals thereof are appropriately set according to the length (height) of the antenna elements 21 and the frequency of the electromagnetic waves transmitted from the transmitting antenna 20 .

In the radar device 100 according to the present embodiment, an example of using a grounded monopole antenna that can reduce the size of the entire device as the antenna element 21 because the length can be shortened has been shown. As 21, various antenna elements other than the grounded monopole antenna, such as a half-wave dipole antenna (λ/2), can be employed.

In addition, as the transmitting antenna of the real-time transmitting/receiving device disclosed in the present application, for example, including the case where it is a transmitting/receiving device of a device that performs real-time data processing of a transmitted signal and a received signal, the above-mentioned grounded monopole antenna, half In addition to wavelength dipole antennas, chip antennas such as triplate antennas and microstrip antennas, pattern antennas composed of conductor patterns on circuit boards, Yagi antennas with antenna elements, ground plane antennas, etc. can be employed and there is no restriction on the types of antenna elements that can be used.

The receiving antenna 30 is arranged on the surface of the circuit board 10 on which the transmitting antenna 20 is arranged, and receives a reflected wave of the electromagnetic waves transmitted from the transmitting antenna 20 reflected on the surface of the object to be measured.

In the radar device 100 of the present embodiment, the receiving antenna 30 also employs a grounded monopole antenna (λ/4) similar to the transmitting antenna 20, and a predetermined number of antenna elements 31 are arranged in a line in a resin frame. are placed side by side. In FIG. 1, the transmitting antenna 20 and the receiving antenna 30 are shown to have the same shape, but the number and arrangement intervals of the antenna elements 31 of the receiving antenna 30 are such that the reflected wave from the object to be measured can be reflected with a higher gain. It is appropriately set so that the conditions for receiving are obtained. When the real-time transmitting/receiving device is a radar device as in this embodiment, the frequency of the transmission signal and the frequency of the reception signal are basically the same. length) is the same as the length of the antenna element 21 of the transmitting antenna 20 .

As for the type of the antenna element 31 of the receiving antenna 30, as with the antenna element 21 of the transmitting antenna 20 described above, various types of antenna elements such as a half-wave dipole antenna can be used in addition to the grounded monopole antenna. can be used.

The electromagnetic wave absorber 40 is arranged between the arrangement position of the transmitting antenna 20 and the arrangement position of the receiving antenna 30 on the circuit board 10. In the radar device 100 according to the present embodiment, the electromagnetic wave absorber 40 has a width W and a length (depth) It has a cubic shape with L and height H.

The electromagnetic wave absorber 40 is made by dispersing ferritic magnetic iron oxide powder such as epsilon iron oxide, hexagonal ferrite, and strontium ferrite in a binder made of a non-conductive organic material such as resin or rubber. It is configured by solidifying the magnetic paint contained.

Resin materials such as epoxy resins, polyester resins, polyurethane resins, acrylic resins, phenol resins, melamine resins, and rubber resins can be used as binders. Among these, it is preferable to use a rubber-based resin for the purpose of imparting flexibility to the radio wave absorber.

Rubber resins include styrene-based thermoplastic elastomers such as SIS (styrene-isoprene block copolymer) and SBS (styrene-butadiene block copolymer), petroleum-based synthetic rubber EPDM (ethylene propylene diene rubber), and other rubber-based materials such as acrylic rubber and silicon rubber are preferably used.

The magnetic iron oxide powder described above can magnetically resonate at a frequency in the millimeter wave band or higher, and can convert the electromagnetic waves transmitted from the transmission antenna 20 incident on the electromagnetic wave absorber 40 into heat and absorb the heat. In addition, in the radar device 100 of the present embodiment, the electromagnetic wave absorber 40 is formed by hardening the magnetic paint in which the magnetic iron oxide powder is dispersed in the binder. can be

Here, an example of a method for producing the electromagnetic wave absorber 40 will be described.

In order to produce the electromagnetic wave absorber 40 as described above, first, a magnetic paint is produced. For example, when epsilon iron oxide is used as the magnetic iron oxide powder, the magnetic paint consists of the epsilon iron oxide powder and a dispersant. It is prepared by obtaining a kneaded mixture of a phosphoric acid compound and an epoxy resin as a resin binder, diluting it, further dispersing it, and filtering it with a filter.

The kneaded product is obtained by kneading with a pressurized batch type kneader or by other methods. Further, the kneaded material can be dispersed as a dispersion using, for example, a sand mill filled with beads such as zirconia. At this time, a cross-linking agent can be blended as necessary. The magnetic paint thus obtained is coated on a releasable support, such as a polyethylene terephthalate (PET) sheet having a predetermined thickness that has been subjected to a release treatment with a silicone coat, using a table coater or bar coater. apply.

Thereafter, the wet magnetic paint is dried at 80° C. and calendered at a predetermined temperature using a calender to form the radio wave absorber 40 having a predetermined shape and size on the support.

As another method for producing the electromagnetic wave absorber 40, an extrusion molding method can be used.

When the extrusion molding method is used, for example, magnetic iron oxide powder, a binder, and optionally a dispersant are blended in advance, and these blended materials are fed into a plastic cylinder from the resin supply port of the extruder. do. As an extruder, a normal extruder equipped with a plastic cylinder, a die provided at the tip of the plastic cylinder, a screw rotatably disposed in the plastic cylinder, and a drive mechanism for driving the screw A molding machine can be used.

The molten material plasticized by the band heater of the extruder is sent forward by the rotation of the screw and extruded from the tip in the form of a sheet. The electromagnetic wave absorber 40 having a predetermined thickness can be obtained by subjecting the extruded material to drying, pressure molding, calendering, or the like.

Furthermore, as a method of producing the electromagnetic wave absorber 40, a method of producing a magnetic compound containing a magnetic iron oxide powder and a binder, molding it to a predetermined thickness, and cross-linking it can also be used.

In this case, first, a magnetic compound is produced. A magnetic compound can be obtained by kneading a magnetic iron oxide powder, a binder, and, if necessary, a dispersant. The kneaded material is obtained, for example, by kneading with a pressurized batch kneader. At this time, a cross-linking agent can be blended as necessary.

The resulting magnetic compound is crosslinked and molded into a predetermined shape at a temperature of 150° (hereinafter, the temperature is Celsius) using, for example, a hydraulic press. After that, secondary cross-linking treatment is performed at a temperature of 170° in a constant temperature bath. In this manner, an electromagnetic wave absorber 40 having a predetermined shape can be produced.

The electromagnetic wave absorber 40 manufactured as described above is peeled off from the support and adhered to a predetermined position of the circuit board 10 with an adhesive or the like.

At this time, the distance D between the electromagnetic wave absorber 40 and the antenna element 21 of the transmitting antenna 20 is D>(λ/2π), so that the electromagnetic wave radiated from the transmitting antenna 20 is absorbed by the surface of the electromagnetic wave absorber 40. It is possible to avoid the fact that the light is reflected at and is not well absorbed. Details of the distance D between the antenna element 21 and the electromagnetic wave absorber 40 and details of the position and size of the electromagnetic wave absorber 40 will be described later.

The operating circuit unit 50 is an assembly of electronic circuits for operating the radar device 100 shown in this embodiment. The operation circuit unit 50 generates a transmission signal to be transmitted from the transmission antenna 20, performs various processing such as amplification and noise removal on the reception signal received by the reception antenna 30, and determines the position and movement of the object to be measured. are analyzed, and the data is recorded, displayed, or output to other equipment. Further, the drive circuit section 50 includes a power supply circuit that operates the drive circuit section 50 itself. The specific configuration of these operating circuit sections 50 uses conventional circuit technology and varies depending on the purpose and usage conditions of the real-time transmission/reception apparatus, so a detailed description thereof will be omitted.

As shown in FIG. 1, in the radar device 100 according to the present embodiment, the drive circuit unit 50 is arranged on the surface of the circuit board 10 behind the surface on which the transmitting antenna 20 and the receiving antenna 30 are arranged. This is a measure to prevent electromagnetic waves leaked from the drive circuit section 50 from adversely affecting received signals, and to avoid the effects of electromagnetic waves incident on the device on the drive circuit section. The arrangement position of the drive circuit unit 50 and the configuration of the circuit board 10 are not limited to those shown in FIG. If it can be avoided, the drive circuit section 50 can be arranged on the surface of the circuit board 10 on which the transmitting antenna 20 and the receiving antenna 30 are arranged. In addition, as a structure in which a plurality of circuit boards are laminated, the transmitting antenna and the receiving antenna are arranged on the circuit board positioned on the outermost layer, and the antennas are positioned on the lower side of the outermost circuit board on the second layer and below. Various forms can be employed, such as a configuration in which the drive circuit section 50 is arranged on a circuit board.

The input/output terminal 60 is a terminal unit for connecting the radar device 100 and external devices, such as supplying operating power to the radar device 100 and outputting received signals and data-processed signals. be.

Since the input/output terminal 60 can use a conventionally well-known technique as a terminal structure for connecting a circuit board that constitutes an electrical device, detailed description thereof will be omitted in this specification.

<Regarding the distance D between the antenna element of the transmitting antenna and the electromagnetic wave absorber>
FIG. 2 shows the relationship between the distance from the transmitting antenna and the wave impedance of the transmitted electromagnetic waves. In FIG. 2, the distance from the transmitting antenna is shown normalized by half the wavelength λ of the transmitted electromagnetic wave.

As shown in Fig. 2, although there are variations in the measurement data, the distance from the transmitting antenna differs greatly at 1/2π (λ/2π: horizontal axis = 1) of the wavelength λ of the transmitted electromagnetic wave. , a region where the distance is smaller than λ/2 is separated into a portion where the magnetic field indicated by the solid line of symbol a in FIG. As /2 becomes smaller, the wave impedance a of the magnetic field decreases exponentially, and the wave impedance b of the electric field increases exponentially. Therefore, when the distance D between the antenna element 21 of the transmitting antenna 20 and the electromagnetic wave absorber 40 becomes smaller than λ/2π, the electromagnetic wave is reflected on the surface of the electromagnetic wave absorber 40 , and the electromagnetic wave absorber 40 absorption is almost non-existent.

On the other hand, in a region where the distance from the transmitting antenna is greater than 1/2π (λ/2π: horizontal axis = 1) of the wavelength λ of the transmitted electromagnetic wave, the solid line a and the dotted line b overlap. , neither the magnetic field nor the electric field is dominant. In this case, since an electromagnetic wave is composed of an electric field and a magnetic field, the electromagnetic wave can be incident on the electromagnetic wave absorber 40, and the electromagnetic wave absorber 40 can be designed considering the impedance of 377Ω in normal air. , the reflection on the surface can be suppressed, and the electromagnetic waves transmitted from the transmitting antenna 20 can be absorbed satisfactorily.

The electromagnetic waves transmitted from the transmitting antenna 20 spread radially from the antenna element 21 . Therefore, if the distance D between the transmitting antenna 20 and the electromagnetic wave absorber 40 is too large, most of the electromagnetic waves radiated from the transmitting antenna 20 in the direction of the receiving antenna 30 pass through the position where the electromagnetic wave absorber 40 is arranged. There is a risk that the light will be diffused to the surroundings, reflected by other components such as the housing of the radar device 100 , and received by the receiving antenna 30 . From the viewpoint of avoiding such a situation, the arrangement interval D between the transmitting antenna 20 and the electromagnetic wave absorber 40 should not be too large so that the electromagnetic waves radiated from the transmitting antenna 20 toward the receiving antenna 30 are It is preferable to allow more light to enter the electromagnetic wave absorber 40 and be absorbed.

According to the study of the inventors, when the size of the transmitting antenna 20 and the electromagnetic wave absorber 40 are the same, the distance D between the transmitting antenna 20 and the electromagnetic wave absorber 40 is the distance of the electromagnetic wave transmitted from the transmitting antenna. It was confirmed that the electromagnetic wave absorber 40 can absorb most of the electromagnetic waves radiated from the transmitting antenna 20 toward the receiving antenna 30 by satisfying the condition D<(λ/π) with respect to the wavelength λ.

<Regarding the size and position of the transmitting antenna>
Next, regarding the outer shape of the electromagnetic wave absorber 40, more specifically, as shown in FIG. 40 will be described based on the positional relationship between the transmitting antenna 20 and the receiving antenna 30. FIG.

FIG. 3 is a diagram for explaining the size and planar arrangement position of an electromagnetic wave absorber with respect to the arrangement positions of a transmitting antenna and a receiving antenna.

As shown in FIG. 3, in a horizontal plane parallel to the surface of the circuit board 10 of the radar device 100, the electromagnetic wave absorber 40 can see each antenna element 31 of the receiving antenna 30 from each antenna element 21 of the transmitting antenna 20. It is preferably formed and arranged such that it cannot.

As shown in FIG. 3, when the transmitting antenna 20 has five antenna elements 21a to 21e, the five antenna elements 31a to 31e of the receiving antenna 30 are connected from the first antenna element 21a of the transmitting antenna 20. The viewing direction is between the viewing direction of the first antenna element 31a of the receiving antenna 30 indicated by the arrow 71a in FIG. 3 and the viewing direction of the fifth antenna element 31e indicated by the arrow 71b. Considering the other antenna elements 21b to 21e of the transmitting antenna 20 in the same way, the direction in which the fifth antenna element 21e of the transmitting antenna 20 sees the fifth antenna element 31e of the receiving antenna 30, which is shown as an arrow 72 in FIG. is the rightmost direction in FIG. Therefore, as shown in FIG. 3, by arranging the electromagnetic wave absorber 40 having a length L that blocks both the arrows 71a and 72 at a position that blocks both the arrows 71a and 72, the transmission antenna It can be said that the antenna elements 21 of the receiving antenna 30 are arranged so that the antenna elements 31 of the receiving antenna 30 cannot be seen from the antenna elements 21 of the receiving antenna 30 .

Next, the height H of the electromagnetic wave absorber 40 will be considered.

In order to prevent the electromagnetic wave transmitted from the transmitting antenna 20 from being directly received by the receiving antenna 30 by the electromagnetic wave absorber 40, the height H of the electromagnetic wave absorber 40 from the surface of the circuit board 10 is adjusted by the electromagnetic wave absorber 40. , the antenna elements 21a to 21e of the transmitting antenna 20 and the antenna elements 31a to 31e of the receiving antenna 30 cannot be seen.

FIG. 4 is a diagram for explaining the size of the electromagnetic wave absorber in the height direction with respect to the heights of the transmitting antenna and the receiving antenna.

In the radar device 100 of this embodiment, grounded monopole antennas are used as the antenna elements 21 and 31 in both the transmitting antenna 20 and the receiving antenna 30 as described above. A grounded monopole antenna is essentially an antenna because the frequency of the electromagnetic wave to be transmitted and received is determined by the length to the tip of the antenna element and the ground (ground) on the substrate on which the antenna element is placed. It can be considered that electromagnetic waves are transmitted and received at the tips of the elements 21 and 31 .

For this reason, as shown in FIG. 4, the electromagnetic wave absorber 40 is placed at a height that blocks the arrow indicated by reference numeral 81 in FIG. It is preferable to define the height H ₁ of . By doing so, the antenna element 31 of the receiving antenna 30 cannot be seen from any part of the antenna element 21 of the transmitting antenna 20 in the height direction, and the electromagnetic wave radiated from the antenna element 21 of the transmitting antenna 20 can be prevented from being blocked by the electromagnetic wave absorber 40 and received by the antenna element 31 of the direct receiving antenna 30 .

In this embodiment, which exemplifies the radar device 100, the wavelengths of the transmitted and received electromagnetic waves are the same, so the antenna element 21 of the transmitting antenna 20 and the antenna element 31 of the receiving antenna 30 have the same length (height). Therefore, if the transmitting antenna 20, the receiving antenna 30, and the electromagnetic wave absorber 40 are all placed on the same plane of the circuit board 10, the height H ₁ of the electromagnetic wave shield 40 is equal to that of the antenna elements 21 and 31. If it is larger than the length, it can be said that the antenna element 31 of the receiving antenna 30 cannot be seen from the antenna element 21 of the transmitting antenna 20 .

3 and the vertical direction shown in FIG. In other words, virtual lines connecting all parts of all the antenna elements 21 of the transmitting antenna 20 and all parts of all the antenna elements 31 of the receiving antenna 30 must be the electromagnetic wave absorber 40. By determining the size and arrangement position of the electromagnetic wave absorber 40 so as to block the electromagnetic wave absorber 40, the effect of reducing the signal noise of the received signal by the electromagnetic wave absorber 40 is effectively exhibited.

Even if the real-time transmitting/receiving device disclosed in the present application is a radar device, it is possible that the heights of the mounting surfaces of the transmitting antenna and the receiving antenna are not the same. Also, if the real-time transmitting/receiving device is not a radar device, the frequencies of the electromagnetic waves to be transmitted and the electromagnetic waves to be received may differ, and the length of the antenna element may differ between the transmitting antenna and the receiving antenna. Even in such a case, by setting the height of the electromagnetic wave absorber 40 so that the antenna element of the receiving antenna cannot be seen from the antenna element of the transmitting antenna, the electromagnetic waves transmitted from the transmitting antenna can be directly received by the receiving antenna. Therefore, noise in the received signal can be effectively prevented.

FIG. 5 is another diagram for explaining the size of the electromagnetic wave absorber in the height direction with respect to the heights of the transmitting antenna and the receiving antenna.

In the example shown in FIG. 5, the receiving antenna 30 is not placed directly on the surface of the circuit board 10, but placed on a member 83 having a predetermined height. In the example shown in FIG. 5 as well, the electromagnetic wave absorber blocks the arrow 82 in FIG. A height H ₂ of 40 is preferably defined.

Note that, for example, when the electromagnetic wave absorber 40 is arranged on the upper surface of a separate member on the circuit board 10, the height of the arrangement position of the electromagnetic wave absorber 40 is the same as the height of the arrangement positions of the transmitting antenna 20 and the receiving antenna 30. A virtual line indicating the direction in which the tip of the antenna element 31 of the receiving antenna 30 is viewed from the tip of the antenna element 21 of the transmitting antenna 20 when placed on the separate member. It is preferable to determine the height H of the electromagnetic wave absorber 40 so as to block the .

Furthermore, when the circuit board is curved, when the circuit boards on which the transmitting antenna and the receiving antenna are mounted are different, and the height of the surface of the circuit board on which each antenna is arranged is different, the transmitting antenna In any case, a virtual line is drawn from the tip of the transmitting antenna to the tip of the receiving antenna, and this virtual line is blocked. It is preferable to set the height H of the electromagnetic wave absorber to

Regarding the length L of the electromagnetic wave absorber 40 shown in FIG. 3 and the height H (H ₁ , H ₂ ) of the electromagnetic wave absorber 40 shown in FIGS. When it is determined to block 82, it is necessary to have a margin of several millimeters, for example, about 5 to 8 mm or more, in consideration of manufacturing errors and electromagnetic wave wraparound that may occur very slightly. preferable.

Further, the width of the electromagnetic wave absorber 40 indicated by W in FIG. At least 1 mm thick enough to absorb electromagnetic waves, for example, when epsilon iron oxide powder is used as the electromagnetic wave absorbing material and the volume content of the electromagnetic wave absorbing material contained in the binder is 45%. can be

In general, in the case of an electromagnetic wave absorber that absorbs electromagnetic waves with magnetic iron oxide powder that magnetically resonates at frequencies in the millimeter wave band or higher, as shown in this embodiment, the thickness in the incident direction of the electromagnetic waves is preferably as large as possible. . For this reason, considering the placement distance between the transmitting antenna and the receiving antenna, the presence or absence of components that may cause problems if the electromagnetic wave absorber is placed nearby, and the cost, the electromagnetic wave transmitted from the transmitting antenna should be sufficiently absorbed. It is preferred to make it as thick as possible.

As described above with reference to FIGS. 3, 4, and 5, in the radar device 100 according to the present embodiment, the size and arrangement position of the electromagnetic wave absorber 40 can be determined from the antenna element 21 of the transmitting antenna 20. By making the antenna element 31 of the receiving antenna 30 invisible, it is possible to prevent the electromagnetic wave transmitted from the transmitting antenna 20 from being directly received by the receiving antenna 30 . The inventors have confirmed that in the radar device 100 of the present embodiment, the antenna element 21 of the transmitting antenna 20 and the antenna element 31 of the receiving antenna 30 cannot be expected between the transmitting antenna 20 and the receiving antenna 30. By arranging the electromagnetic wave absorber 40 having a thickness of 10 dB, the noise in the signal received by the receiving antenna 20 could be reduced by 10 dB at maximum.

Note that the length L and height H of the electromagnetic wave absorber 40 are restricted by the configuration of the radar device 100, etc., and the antenna element 31 of the receiving antenna 30 cannot be expected from the antenna element 21 of the transmitting antenna 20 at all. It can also be assumed that it cannot be placed in a state. Even in this case, by setting the electromagnetic wave absorber to have a length and height of 60% or more of the ideal length L and height H, an undesirable The effect of absorbing electromagnetic waves and reducing noise components is obtained.

In the above embodiment, as an example of the real-time transmission/reception device, the transmission antenna and the reception antenna are grounded monopole antennas. , a chip antenna or a pattern antenna can be used as the antenna element. Since these antenna elements have substantially no height above the circuit board, the height H of the electromagnetic wave absorber can be reduced.

In the above embodiment, the electromagnetic wave absorber is exemplified by one in which the magnetic iron oxide powder is dispersed in an organic material binder such as resin or rubber. It is also possible to form a shaped electromagnetic wave absorber. However, in the case of using a baked molding as the electromagnetic wave absorber, a molding container must be prepared each time an electromagnetic wave absorber of a predetermined shape is produced, which tends to increase the cost. In addition, by using a flexible resin material or rubber material as a binder constituting the electromagnetic wave absorber, the electromagnetic wave absorber itself can be provided with flexibility and elasticity. When the electromagnetic wave absorber is deformable, it is possible to finely adjust the shape of the electromagnetic wave absorber by deforming it according to the state of arrangement on the circuit board, which is highly convenient.

The electromagnetic wave absorber includes a dielectric layer with a predetermined thickness and a metal layer provided on the back side, and absorbs the electromagnetic wave by reversing the phases of the incident electromagnetic wave and the electromagnetic wave reflected by the metal layer. It is also possible to use a reflective (λ/4 type) electromagnetic wave absorbing member. However, when a reflective electromagnetic wave absorbing member is used as the electromagnetic wave absorber, a metal layer is arranged as a reflective layer on the receiving antenna side. Consideration such as adjusting the placement interval with the antenna is required.

Furthermore, the electromagnetic wave absorber can be formed using various electromagnetic wave absorbing members, such as carbon and carbon nanotubes, which can absorb electromagnetic waves in a frequency band higher than the millimeter wave band.

The real-time transmitting/receiving device disclosed in the present application is useful in the fields of radar devices and data communication devices as a real-time transmitting/receiving device that transmits and receives radio waves in a high frequency band equal to or higher than the millimeter wave band and performs data processing in real time.

10 circuit board 20 transmitting antenna 21 antenna element (transmitting antenna)
30 Receiving antenna 31 Antenna element (receiving antenna)
40 electromagnetic wave absorber 50 drive circuit unit 60 input/output terminal 100 radar device (real-time transmission/reception device)

Claims (5)

comprising a transmitting antenna and a receiving antenna,
A real-time transmitting/receiving device that simultaneously performs transmission and reception using electromagnetic waves having a frequency in the millimeter wave band or higher,
The transmitting antenna and the receiving antenna each have a rod-shaped antenna element having a predetermined height arranged on one surface of a circuit board,
An electromagnetic wave absorber is arranged between the arrangement position of the transmitting antenna and the arrangement position of the receiving antenna,
The receiving antenna receives a reflected wave of the electromagnetic wave transmitted from the transmitting antenna reflected on the surface of the object to be measured;
The electromagnetic wave absorber is arranged so that the antenna element of the transmitting antenna cannot be seen from the antenna element of the receiving antenna,
The electromagnetic wave absorber contains a magnetic iron oxide powder that magnetically resonates at frequencies above the millimeter wave band and an organic material binder,
The distance D between the antenna element of the transmitting antenna and the electromagnetic wave absorber satisfies the relationship D>(λ/2π) with respect to the wavelength λ of the electromagnetic wave absorbed by the electromagnetic wave absorber. Time transmitter and receiver. 2. The real-time transmitting/receiving apparatus according to claim 1, wherein a distance D between an antenna element of said transmitting antenna and said electromagnetic wave absorber further satisfies the relationship D<([lambda]/[pi]). 3. The real-time transmitter/receiver according to claim 1, wherein the noise in the signal received by said receiving antenna is reduced by up to 10 dB. The electromagnetic wave absorber is arranged so as to block virtual lines connecting all parts of all the antenna elements of the transmitting antenna and all parts of all the antenna elements of the receiving antenna. 4. The real-time transmitting/receiving device according to any one of 3 . 5. The real-time transmitting/receiving apparatus according to claim 1, wherein said electromagnetic wave absorber suppresses direct incidence of electromagnetic waves radiated from a transmitting antenna to a receiving antenna.

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