JP4940404B2 - Folded antenna - Google Patents

Description

  The present invention relates to a multi-resonant folded antenna that eliminates a deep drop in directivity by providing a capacitive element.

Conventionally, Patent Document 1 below discloses a held antenna in which a metal wire is bent in a loop shape. In Patent Document 2 below, a multi-resonance antenna is realized by using an inverted F-type antenna and an inverted L-type or rod antenna parallel to the antenna. In Patent Document 2, in order to prevent the current in the radiation line of the electromagnetic wave from being reversed in the even mode excitation, the non-excited element provided in parallel is inductively coupled as a rod instead of an inverted L type. Thus, the radiated radio wave at the second resonance frequency is prevented from dropping. ,
JP 2006-262356 A JP-A-9-326632

  However, in Patent Document 1, although impedance matching can be achieved in a wide frequency band at a feeding point, it cannot be used at a plurality of frequencies. In Patent Document 2, although it can be used at a plurality of frequencies, there is a problem that the radiation efficiency is poor because the radiation side of the non-excitation element is not used for radiation of electromagnetic waves at the plurality of frequencies.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to realize a multi-resonant antenna having a compact structure that is non-directional and has high radiation efficiency.

In order to solve the above problems, the following means are effective.
The present invention relates to a folded antenna comprising at least two first metal wires parallel to each other and connected to each other by a connection line, and a second metal wire. Each of the second metal wirings bends and extends at 90 degrees with respect to the first rising portion and the second rising portion disposed in the polarization direction of the radio wave to be transmitted and received, and the rising portions. A first extension portion and a second extension portion, provided in parallel with the first rising portion of the first metal wiring, and made of a metal wiring connected to the first metal wiring; A folded antenna having a capacitor element inserted in a second rising portion of the second metal wiring.

  In the present invention, a third rising portion parallel to the first rising portion of the first metal wiring and the second rising portion of the second metal wiring, the first extension portion of the first metal wiring, and the second A third metal wiring composed of a third extension parallel to the second extension of the second metal wiring may be provided.

The third metal wiring can be configured as follows.
The third metal wiring is longer than the first metal wiring and the second metal wiring, and has a second connection line parallel to the connection line, and the tip of the second connection line is The structure connected to the 2nd extension part of the 2nd metal wiring which opposes, or the 1st extension part of the 1st metal wiring can be employ | adopted.

  The third metal wiring is provided between the first metal wiring and the second metal wiring and on the side close to the first metal wiring, and the tip of the second connection line is A configuration in which the second extension of the second metal wiring is connected can be employed.

  In addition, the third metal wiring is disposed between the first metal wiring and the second metal wiring, and the tip thereof is connected to the connection line. A configuration in which an element is inserted can be employed.

  In addition, a configuration in which the first metal wiring, the second metal wiring, and the feeder line are metal plates having a width parallel to a plane perpendicular to the polarization direction can be employed.

  Further, it is possible to adopt a configuration in which the first metal wiring and the second metal wiring are bent into a U-shape, and the first extension portion and the second extension portion are paired in parallel.

  Further, it is possible to employ a configuration in which the third metal wiring is bent into a U-shape and the third extension portion is a parallel pair.

  In addition, the first rising portion of the first metal wiring, the second rising portion of the second metal wiring, and the power supply line are erected on the ground conductor, and the first extension portion of the first metal wiring is provided. And the 2nd extension part of the 2nd metal wiring can employ | adopt the structure arrange | positioned in parallel with this ground conductor. This configuration is not a pair of extension portions provided in parallel, but forms a mirror image of the parallel portion and the upright portion with respect to the ground conductor, and the actual flat portion, the upright portion, and the mirror image thereof. Thus, a pair of plane portions and an upright portion are formed. The ground conductor only needs to have a larger area than the metal wiring, and preferably has a planar shape. However, as long as a mirror image of the planar portion can be formed, the shape is not limited to the surface, and may be a line having a width wider than that of the metal wiring. The ground conductor is a roof or a frame of an automobile when the antenna is mounted on the automobile.

  Further, the third rising portion of the third metal wiring is erected on the ground conductor, and the third extension portion of the third metal wiring is arranged in parallel to the ground conductor. Can be adopted. The point that a mirror image of the ground conductor of the third metal wiring is used and the configuration of the ground conductor are the same as described above. The above-mentioned ground conductor can be employed.

  In addition, the capacitive element includes an electrode plate formed by bending an end portion on the ground conductor side of the second raised portion of the second metal wiring in parallel with the ground conductor, and between the electrode plate and the ground conductor. It is possible to adopt a configuration comprising a dielectric material disposed.

  According to the present invention, with respect to the first metal wiring, the power supply line is provided in parallel to the first rising portion, and the capacitive element is provided to the second rising portion of the second metal wiring parallel to the first metal wiring. The directivity in the plane perpendicular to the polarization direction of the radio wave to be transmitted and received is deep in the first resonance frequency and the second resonance frequency that appears in the vicinity of a frequency about twice that of the first resonance frequency. The depression can be eliminated. Moreover, since one radiation can have a plurality of radiation sides, radiation efficiency can be increased. In addition, as a result of facilitating impedance matching, radiation efficiency is improved.

By providing the third metal wiring, it is possible to eliminate a deep drop in the directivity on the plane perpendicular to the polarization direction of the radio wave to be transmitted and received and to increase the number of resonance frequencies. In particular, in the third and fourth aspects of the invention, it is possible to effectively prevent the drop in directivity and increase the number of resonance frequencies to 3, for example.
According to the invention of claim 5, the impedance of the antenna viewed from the feeding point of the feeding line can be increased by inserting the capacitive element into the third rising portion of the third metal wiring. As a result, impedance matching can be easily achieved and radiation efficiency can be improved.

According to the invention of claim 6, since the width of the metal wiring is widened, the resonance length has a width, the resonance frequency has a width, and the usable frequency band is widened.
According to the inventions of claims 9 and 10, the metal wiring can be reduced by half compared to the inventions of claims 7 and 8 formed in a U-shape in which a pair of plane portions are provided, and the material can be reduced. In addition, the size of the antenna can be reduced. Moreover, it becomes easy to attach on a planar or linear metal conductor.
According to the eleventh aspect of the present invention, since the capacitor element can be formed simultaneously with the second metal wiring, manufacturing is facilitated.

  A structure in which the folded antenna of Patent Document 1 is applied to an inverted F-type antenna is not known. An antenna in which the inverted F-type antenna is arranged as a target and is a folded antenna with a double wiring will be considered below as a comparative example. A perspective view of the antenna A11 having the structure is shown in FIG. The metal wiring p11 and the metal wiring q11, which have two bent parts of approximately 90 degrees and are bent in a U shape, are arranged in parallel and short-circuited at both ends with metal wiring s101 and s102, respectively. is doing. Both ends of a metal wiring r11 having a feeding point F11 that is a pair of two points FT11 and FB11 are connected to two points on the metal wiring p11. In this way, a folded structure is formed, that is, another metal wiring q11 is added in parallel to the metal wiring p11 and the metal wiring r11, and the two are connected by the metal wirings s101 and 102. As a result, in the antenna A11, the second resonance frequency appears in the vicinity of a frequency twice as high as the first resonance frequency. Therefore, for example, it can be applied to a dual frequency antenna of 900 MHz band and 1800 MHz band.

  On the other hand, a structure in which the metal wiring q11 and the metals s101 and 102 are removed from the folded antenna A11, that is, a single antenna composed only of the metal wiring p11 and the metal wiring r11, is three times the first resonance frequency. A second resonance appears near the frequency of.

  Here, focus on the xy plane directivity. 9 (a) and 9 (b) show the xy plane directivities at the first resonance fe and the second resonance 1.76fe of the antenna A11 of the comparative example. The first resonance fe is omnidirectional. The minimum value is 0 dBi. On the other hand, in the second resonance 1.76fe, as shown by the R part in FIG. 9 (b), a drop of −8.3 dBi occurs. Therefore, when communicating with a communication device in the xy plane, communication cannot be performed depending on the direction of the communication device. The problem is to eliminate the drop in the xy plane.

  In order to consider the cause of the deep dip, the current distribution in the first resonance fe and the second resonance 1.76fe is shown in FIGS. 10 (a) and 10 (b). The size of the arrow represents the current intensity. The current component in the z-axis direction of the polarization direction corresponds to the wave source of the Eθ component of the xy plane directivity. In the first resonance fe, a strong current flows through the metal wiring r11 extending in the z-axis direction and the wiring portion 90 extending in the z-axis direction of the metal wiring q11 and has the same phase. Therefore, the xy plane directivity is omnidirectional. On the other hand, in the second resonance 1.76fe, a large current is applied to the wiring portion 80 and the wiring portion 90 extending in the z-axis direction of the metal wiring r11 extending in the z-axis direction and the metal wiring p11 and the metal wiring q11, respectively. Is flowing. Moreover, it can be seen that the phase of the current in the wiring portion 90 extending in the z-axis direction of the metal wiring q11 is opposite in phase to the current in the wiring portion 80 extending in the z-axis direction of the metal wiring r11 and the metal wiring p11. . Therefore, this causes a drop in the directivity in the xy plane.

  The following examples are antennas in which this drop in directivity is effectively prevented. Hereinafter, the present invention will be described based on specific examples. The present invention is not limited to the following examples.

  FIG. 1 shows a perspective view of the folded antenna A1 according to the first embodiment of the present invention. The first metal wiring p1 is bent at approximately 90 degrees at the first raised portion 10 rising in the vertical direction and the bent portions 13 and 14 with respect to the raised portion 10, and the first extensions parallel to each other. It consists of parts 11 and 12. Similarly, the second metal wiring q1 is also bent at approximately 90 degrees at the second raised portion 30 rising in the vertical direction and the bent portions 33, 34 with respect to the raised portion 30, and the second raised portions 30 are parallel to each other. 2 extension parts 31 and 32 are comprised. The first and second upright portions 10 and 30 are parallel to the polarization direction of the radio wave to be transmitted and received and are in the Z-axis direction. When this antenna is mounted on an automobile, the Z-axis direction is generally the vertical direction. As described above, the first metal wiring p1 and the second metal wiring q1 configured in a U-shape are arranged in parallel, and the first extensions 11 and 12 and the second metal wiring q1 are arranged in parallel. The distal ends of the extension portions 31 and 32 are short-circuited by a metal wire s11 and a metal wire s12 that are connection lines.

  Both ends 51 and 52 of a feed line r1 made of metal wiring having a feed point F1 consisting of a pair of two terminals FT1 and FB1 are connected to two points on the first metal wiring p1. The connection points 51 and 52 are provided at a position of 0.092 λa from the first rising portion 10. Note that λa is a free space wavelength at the first resonance frequency fa (= 923 MHz). Therefore, the distance between the connection points 51 and 52 and the first rising portion 10 is 30 mm. The difference from the antenna A11 of the comparative example is that a capacitive element C1 is provided at substantially the center of the second raised portion 30 of the second metal wiring q1. The dimensions of the antenna include the length L of the extensions 11, 12, 31, 32, the height 2h of the upright portions 10, 30, and the distance d between the first metal wiring p1 and the second metal wiring q1. The lengths of the metal wirings s11 and s12 were set to 0.308λa, 0.123λa, and 0.015λa, respectively. Expressed in terms of distance, they are 100 mm, 40 mm, and 9 mm, respectively. The capacitance value of the capacitive element C1 was 0.05 pF.

  FIG. 2 shows the voltage standing wave ratio (VSWR) of the antenna A1 of the first embodiment. A second resonance appears at 1.9 times the first resonance frequency fa. In the vicinity of the first and second resonance frequencies, the voltage standing wave ratio is 2 or less. The first resonance frequency fa of the antenna A1 of Example 1 and the first resonance frequency fe of the comparative example antenna A11 have a relationship of fa = 1.21fe.

  The xy plane directivities of the antenna A1 at the first resonance frequency fa and the second resonance frequency 1.9fa are shown in FIGS. Both the first and second resonance frequencies are omnidirectional, and the minimum value of the Eθ component is -1.3 dBi and -1.2 dBi, respectively. From this result, it became clear that the drop in the xy plane directivity at the second resonance frequency, which was a problem with the antenna A11 of the comparative example, can be eliminated.

  Next, the effect of the capacitive element C1 on the current distribution will be considered. FIGS. 4 (a) and 4 (b) show the current distribution of the antenna A1 at the first resonance frequency fa and the second resonance frequency 1.9fa. By providing the capacitive element C1 at the center of the second rising portion 30 of the second metal wiring q1, the z-axis direction current of the second metal wiring q1 is reduced in both the first and second resonance frequencies. I understand that. At the second resonance frequency 1.9fa, as shown in FIG. 4 (b), the current flowing through the feed line r1 and the rising portion 10 extending in the z-axis direction of the first metal wiring p1 has the same phase, It becomes a radiation wave source. In other words, it can be understood that by providing the capacitive element C1, the anti-phase current flowing in the metal wiring q11 in the antenna A11 of the comparative example hardly flows. On the other hand, in the present invention, at the first resonance frequency fa, the current flowing through the feeder line r1 becomes the radiation wave source.

  FIG. 5 shows a perspective view of the folded antenna A2 according to the second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals. The difference from the first embodiment is between the first metal wiring p2 and the second metal wiring q2, close to the first metal wiring p2, and the first metal wiring p2 and the metal wiring that is the connection line. A third metal wiring t2 is provided along the inside of s21 and s22 in parallel with the metal wirings s21 and s22. The third metal wiring t2 is bent at a 90 ° angle by the third rising portion 60 parallel to the first rising portion 10 and the bent portions 63 and 64, and is parallel to the first extending portions 11 and 12. The third extension portions 61 and 62 and the second connection lines w21 and w22 having some lines parallel to the connection lines and the metal lines s21 and s22 are provided. The second connection lines w21 and w22, which are the end portions of the third metal wiring t2, are bent along the metal wirings s21 and s22 and extend toward the second metal wiring q2, so that the second metal wiring Connected to two points A and A 'on q2. The length of the third metal wiring t2 is longer than the length 2 (L + h) of the first or second metal wiring. Therefore, it can be said that the third metal wiring t2 is arranged in parallel along a part of the first metal wiring p21, the metal wiring s22, and the second metal wiring q2. With this configuration, a third resonance can be generated between the resonance frequencies fa and 1.9fa. For example, it becomes possible to cover 900 MHz band / 1500 MHz band / 1800 MHz band.

  FIG. 6 shows a perspective view of the folded antenna A3 according to the third embodiment of the present invention. Parts having the same functions as those in the first and second embodiments are denoted by the same reference numerals. The difference from the first embodiment is that a third metal wire t3 having the same length is placed between the metal wires in parallel with the first metal wire p3 and the second metal wire q3. It is a point provided in. This metal wiring t3 is also bent at 90 degrees by the third rising portion 60 parallel to the first rising portion 10 and the bent portions 63 and 64, and the third extension parallel to the first extending portions 11 and 12 It has parts 61 and 62. The tips of the third extension portions 61 and 62 are connected to the connection lines s31 and s32. Further, the capacitive element Cq3 is inserted into the third rising portion 60. With this configuration, the degree of freedom of means for impedance matching at the feed point is improved, and impedance matching becomes easier. Note that the resonant frequencies are fa and 1.9fa, similar to the antenna A1.

  FIG. 7 shows a perspective view of the folded antenna A4 according to the fourth embodiment of the present invention. Parts having the same functions as those in the first embodiment are denoted by the same reference numerals. Also in this embodiment, the antenna has a first upright portion 10, a second upright portion 30, a first extension portion 11 formed by bending 90 degrees with respect to the first upright portion 10, and a second extension portion 32. Yes. There are three differences from the first embodiment.

  The first is the first metal wiring p1, the second metal wiring q1, and the connection lines s1, s2 of the antenna A1, and the antenna A4 has a width parallel to a plane perpendicular to the polarization direction of the radio wave to be transmitted and received. The first metal plate p4, the second metal plate q4, the power feeding plate r4, and the connection plate s4. Thereby, the bandwidth of each resonance frequency can be widened.

  Second, a structure corresponding to one side of the antenna A1 is formed on the ground conductor g4. That is, the other U-shaped metal wiring is configured as a mirror image of the ground conductor g4. With this configuration, the antenna size can be halved. The power feeding unit connects the inner conductor (signal line) of the coaxial line provided on the back side of the ground conductor g4 to the power feeding plate r4 that is the power feeding line by the power feeding pin FP4 through the hole FTH4 provided in the ground conductor g4. The outer conductor (ground) of the coaxial line is connected to the ground conductor g4.

  Third, the capacitive element C4 of the antenna A4 is bent in parallel with the ground conductor g4 at the end of the second raised portion 30 on the side of the ground conductor g4 to form an electrode plate u4. That is, it is composed of the dielectric v4 disposed between the ground conductor g4. Thereby, the capacitive element C4 can be made of the same material as the antenna. Therefore, the antenna A4 can be made more easily manufactured. Note that the dielectric v4 may be omitted as long as the gap between the electrode u4 and the ground g4 can be maintained.

  In the second embodiment shown in FIG. 5, the third metal wiring t2 is disposed on the inner side with respect to the first metal wiring p2 and the second metal wiring q2, but may be disposed on the outer side. good. The distance between the third metal wiring t2 and the first metal wiring p2 may be determined according to the value of the third frequency. Further, the extension portions 61 and 62 of the third metal wiring t2 are configured in parallel over substantially the entire length of the extension portions 11 and 12 of the first metal wiring p2, but on the contrary, The extensions 61 and 62 of the metal wiring t2 may be configured in parallel over substantially the entire length of the extensions 31 and 32 of the second metal wiring q2. In this case, it is desirable that a capacitive element is inserted in the third rising portion 60 of the third metal wiring t2. These relationships are selected by the value of the third frequency to be generated.

  In the third embodiment shown in FIG. 6, the third metal wiring t2 is disposed so as to be connected to the midpoint of the connection line between the first metal wiring p2 and the second metal wiring q2. However, it may not necessarily be the midpoint. Further, the third metal wiring t2 is not limited to one, and a plurality of third metal wirings t2 may be provided in parallel. These relationships are selected according to the impedance matching relationship at the feeding point.

The perspective view of antenna A1 which concerns on the specific Example 1 of this invention. FIG. 5 is a characteristic diagram showing a voltage low standing wave ratio of the antenna A1 according to the first embodiment. (A) is a characteristic diagram showing the xy plane directivity (frequency fa) of the antenna A1 of Example 1, and (b) is a characteristic diagram showing the xy plane directivity (frequency 1.9fa) of the antenna A1. (A) is the characteristic figure which showed current distribution (frequency fa) of antenna A1 of Example 1, (b) is the characteristic figure which showed current distribution (frequency 1.9fa) of the antenna A1. The perspective view of antenna A1 which concerns on the specific Example 2 of this invention. The perspective view of antenna A1 which concerns on the specific Example 3 of this invention. The perspective view of antenna A1 which concerns on the specific Example 4 of this invention. The perspective view of antenna A11 of a comparative example. (A) is a characteristic diagram showing the xy plane directivity (frequency fe) of the antenna A11 of the comparative example, and (b) is a characteristic showing the xy plane directivity (frequency 1.76fe) of the antenna A11 of the comparative example. Figure. (A) is a characteristic diagram showing the current distribution (frequency fe) of the antenna A11 of the comparative example, and (b) is a characteristic diagram showing the current distribution (frequency 1.76fe) of the antenna A11 of the comparative example.

Explanation of symbols

A1, A2, A3, A4, A11: Antenna
F1, F2, F3, F11: Feeding part
FP4: Power supply pin
p1, p2, p3, p11: First metal wiring
q1, q2, q3, q11: Second metal wiring
t2, t3: Third metal wiring
s11, s12, s21, s22, s31, s32: Connection line (metal wiring)
w21, w22: second connection lines r1, r2, r3, r11: feeder lines
p4, q4, s4, r4, u4: Metal plate
C1, C2, Cq3, Ct3, C4, C11: Capacitance elements
v4: Dielectric
g4: Ground conductor
10: First rise
30: Second rise
60: Second rise
10, 12: First extension
31:32: Second extension
61:62: Third extension

Claims (11)

In a folded antenna composed of at least two first metal wires parallel to each other and connected to each other by a connection line, and a second metal wire,
The first metal wiring and the second metal wiring are respectively provided with respect to the first rising portion and the second rising portion disposed in the polarization direction of the radio wave to be transmitted and received, and 90% of these rising portions. A first extension and a second extension bent and extended each time,
A power supply line comprising a metal wiring provided in parallel to the first raised portion of the first metal wiring and connected to the first metal wiring;
A folded antenna comprising: a capacitor element inserted in the second rising portion of the second metal wiring. A third rising portion parallel to the first rising portion of the first metal wiring and the second rising portion of the second metal wiring; and the first extension portion of the first metal wiring. The folded antenna according to claim 1, further comprising: a third metal wiring comprising: a third extension parallel to the second extension of the second metal wiring.   The third metal wiring is longer than the first metal wiring and the second metal wiring, and has a second connection line parallel to the connection line. 3. The folded portion according to claim 2, wherein a front end portion is connected to the second extension portion of the second metal wiring or the first extension portion of the first metal wiring facing each other. antenna.   The third metal wiring is provided between the first metal wiring and the second metal wiring and on the side close to the first metal wiring, and the tip of the second connection line The folded antenna according to claim 3, wherein the portion is connected to the second extension of the second metal wiring.   The third metal wiring is disposed between the first metal wiring and the second metal wiring, and a tip portion of the third metal wiring is connected to the connection line. The folded antenna according to claim 2, wherein a capacitive element is inserted.   The said 1st metal wiring, the said 2nd metal wiring, and the said feeder are comprised by the metal plate which has a width | variety parallel to the surface perpendicular | vertical to the said polarization direction. The restricted folded antenna according to claim 5.   The first metal wiring and the second metal wiring are bent in a U-shape, and the first extension part and the second extension part are configured as a parallel pair. The folded antenna according to any one of claims 1 to 6, characterized in that:   6. The method according to claim 2, wherein the third metal wiring is bent in a U-shape, and the third extension portion is constituted by a pair of parallel wires. The folded antenna according to the item.   The first rising part of the first metal wiring, the second rising part of the second metal wiring, and the power supply line are erected on a ground conductor, and the first metal wiring has a first rising part. 7. The folded antenna according to claim 1, wherein the extension part and the second extension part of the second metal wiring are arranged in parallel to the ground conductor.   The third rising portion of the third metal wiring is erected on the ground conductor, and the third extension of the third metal wiring is disposed in parallel to the ground conductor. The folded antenna according to any one of claims 2 to 5, wherein the folded antenna is characterized.   The capacitor element includes an electrode plate formed by bending an end portion of the second metal wiring on the second conductor at the side of the ground conductor in parallel with the ground conductor, and the electrode plate and the ground conductor. The folded antenna according to claim 9, comprising a dielectric disposed between the folded antennas.

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