JPH09214244A - Two-frequency resonance antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an antenna system in which two radiation conductor boards are arranged closely and resonated at two close frequencies. SOLUTION: Two radiation conductor boards 1A, 1B are provided to one side and the other side of a dielectric board 20 and arranged with an interval to an earthing plate 6, a coupling control capacitive element 2 is connected between the two radiation conductor boards 1A, 1B and a resonance control capacitive element 4A(4B) is connected between the radiation conductor boars 1A (1B) and earthing plate 6 respectively. The capacitance of the coupling control capacitive element 2 is selected so that a current coupled from one radiation conductor board to the other radiation conductor board is opposite in phase with a current given from the one radiation conductor board to the other radiation conductor board via the coupling control capacitive element 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small antenna device used in a communication system having a wide band, or a communication system sharing two or more communication systems, and more particularly to a dual frequency resonance antenna device.

[0002]

2. Description of the Related Art FIGS. 1 and 2 are views showing a conventional antenna device. FIG. 1 shows a printed antenna having two upper and lower radiation conductor plates, and FIG. This is the case when the antennas are arranged side by side in parallel.
Here, 101A and 101B are radiation conductor plates, which are composed of two conductor plates having different lengths or widths. 102 is a power supply line,
103 is a short-circuit metal plate between the radiation plate and the ground plate, 104 is the ground plate, 1
20 is a dielectric plate. In this way, the conventional antenna device achieves two resonances or a wide band with one antenna by causing resonances at two different frequencies in the radiation conductor plates of two different sizes.

[0003] In this case, two resonance frequencies F _L, the ratio of F _H
If it is about 1.5 or more (1.5F _L <F _H ), it can be realized relatively easily. However, it is not possible to resonate at frequencies very close to each other, for example, when the ratio of the two frequencies is less than about 1.5 (F _L <F _H <1.5F _L ), or to bring the two frequencies close to each other to substantially widen the band. extremely difficult. This is because the two resonance wavelengths are close to each other and the two radiation conductor plates are very close to each other, so that the electromagnetic coupling between the two radiation conductors is large and the two radiation plates are electrically combined into one. It is visible, and the effect of using two radiation conductor plates is completely lost. This phenomenon is remarkable when two radiation conductor plates are provided on the upper and lower sides as shown in FIG. 1, but the same is true for the antenna of FIG.

Moreover, in order to suppress this phenomenon, it is necessary to make a large gap between the two radiation conductor plates, so that there is a drawback that the antenna becomes large. On the other hand, when the radiating conductor plates are strongly coupled (narrow gap), if the matching circuit is forced to resonate at two frequencies close to each other, there is a loss in the matching circuit and the antenna gain decreases. there were.

Therefore, in the conventional antenna, (a) the two radiating conductor plates are so close to each other that their coupling is so strong that they cannot be resonated at any two frequencies. (b) When resonating at two frequencies that are very close to each other, or when making them closer to each other to broaden the band, in order to reduce the coupling of the radiating conductor plates, it is necessary to provide a space between them, so that the antenna There is a drawback that it becomes large, and (c) there is a drawback that the antenna gain decreases when the distance between the radiating conductor plates is narrowed and forcibly resonating at two frequencies that are close to each other in a matching circuit or the like.

The object of the present invention is to solve these drawbacks of the prior art and to resonate at any two frequencies.
Further, it is an object of the present invention to provide a dual-frequency resonant antenna device that can reduce the distance between the radiation conductor plates even when resonating at two frequencies that are very close to each other, and thus is small in size and has no fear of lowering the antenna gain.

[0007]

A dual-frequency resonant antenna device according to the present invention has a ground plane, a dielectric plate arranged in parallel with the ground plane, and a space on the dielectric plate in parallel with the ground plane. And at least one radiation conductor plate whose one end is electrically grounded to the ground plate, and a central conductor substantially connected to at least one of the two radiation conductor plates and the ground plate, respectively. A power supply line having an outer conductor; and a coupling control capacitive element connected between the two radiation conductor plates, wherein the capacitance of the coupling control capacitive element is from one of the two radiation conductor plates. The current coupled to the other and the current supplied from the one radiation conductor plate to the other radiation conductor plate through the coupling control capacitive element are selected so that they have opposite phases in the other radiation conductor plate. Has been.

Since the two radiation conductor plates are connected by the coupling control capacitor as described above, the two radiation conductor plates can be arranged close to each other, and two resonance frequencies can be selected close to each other. .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 3 shows a first embodiment of the present invention. Two points on each side of the two quadrilateral radiating conductor plates 1A and 1B, which are arranged to face each other with the quadrilateral dielectric plate 20 interposed therebetween, in this example, ground metal plates 5A and 5B are provided on both sides of the ground plane. Connect with 6,
One point on a side (hereinafter referred to as an open end side) 1a, 1b opposite to the grounded side, one end on the opposite side in this example, is connected to the ground plane 6 via resonance control capacitive elements 4A, 4B, respectively. Connecting. In this embodiment, these capacitive elements 4
The open end sides 1a and 1b to which A and 4B are connected are not parallel to each other, but are oblique sides opposite to each other. A capacitive element 2 for coupling control is connected between these two opposite hypotenuses according to the principle of the present invention. In this coupling control capacitive element 2, a current coupled from one of the two opposing radiation conductor plates 1A, 1B to the other and a current supplied from the one through the coupling control capacitive element to the other are provided. The capacitances of the other radiation conductor plates are adjusted so as to have opposite phases.

Reference numeral 3 is a coaxial feeder line, 5A and 5B are ground metal plates, and 6 is a ground plate. Two radiation conductor plates 1A and 1B
The open end sides 1a and 1b of the above are inclined sides opposite to each other in order to widen the resonance frequency bandwidth of each radiating conductor plate by changing the length in the Z-axis direction for standing a co-standing wave. Is. In addition, the reason why they are made non-parallel is to provide a portion that does not overlap between the opposing radiation conductor plates to facilitate adjustment of the resonance point by each of the capacitive elements 4A and 4B. The center conductor of the coaxial feeder 3 is composed of two ground metal plates 5A,
Between 5B, it is connected to the side of one radiation conductor plate, here 1A, and the outer conductor of the power supply line 3 is connected to the ground plate 6. The position of the connection point of the central conductor is determined by measurement such that the impedance of the antenna device viewed from the connection point is, for example, 50Ω, which is substantially the same as the characteristic impedance of the feeder line 3.

In this way, the radiation conductor plates 1A and 1B are closely opposed to each other and are arranged substantially parallel to the ground plane 6, and the radiation conductor plate 1 is arranged.
The coupling between the radiation conductor plates can be controlled by connecting the coupling control capacitive element 2 between A and 1B. However, the capacitive element 2 for coupling control and the capacitive elements 4A, 4B for resonance control
Has to adjust its capacity according to the shape and resonance frequency of each radiation plate. The heights L ₃ + L ₄ and L ₄ of the radiation conductor plates 1A and 1B from the ground plane 6 are the average lengths of the radiation conductor plates in the Z direction (L ₁ -L ₅
/ 2) is one of the factors that determine the resonance frequency of each radiation conductor plate, and the distance L ₃ between the two radiation conductor plates 1A and 1B is one of the factors that determines the difference between the resonance frequencies. By adjusting the lengths L ₁ , L ₃ , L ₄ , L ₅ and the capacitances C ₁ , C ₂ , each radiating conductor plate can be resonated at any frequency and very close to each other. Even when resonating at one frequency, the distance L ₃ between the two radiating conductor plates can be made relatively small, so that the disadvantage of increasing the size of the antenna is eliminated.

In order to verify this, FIG. 4 shows the result of measurement performed on the antenna device having the structure shown in FIG. However, the dimensions of each part shown in the figure of the antenna device are L ₁
= L ₂ = 30mm, L ₃ = 1.6mm, L ₄ = 5mm, L ₅ = 10mm, each capacitance is C ₀ = 1.5pF, C ₁ = 0.5pF, C ₂ = 1pF, and the dielectric plate 20 The relative permittivity ε _{r of} is ε _r = 3.6. The measurement was performed by installing this antenna device on a square metal housing (not shown) of 130 × 40 × 20 mm. FIG. 4 shows the return loss frequency characteristic. It clearly shows two resonance characteristics from Fig. 4, which is about 820M.
Resonating at Hz and 875MHz. In this case, the difference between the two frequencies is about 6%. With such a simple structure, the distance L ₃ between the two radiation conductor plates 1A and 1B is only 1.6 m.
Even with m, it is possible to resonate at two frequencies that are very close to each other, which is something that could not be done conventionally. Furthermore, as is clear from the figure, a very high antenna gain is obtained at both frequencies. Also, when the efficiency of this antenna was measured, it was -2.4 dB at 820 MHz and at 875 MHz.
It was a high value of -1.8 dB. As described above, it was confirmed by experiments that the present antenna device is a very small antenna, yet it can resonate at any two frequencies and is a small and high gain antenna.

In this case, as the condition of the antenna, it is sufficient that there are two radiation conductor plates, and even if the shapes and sizes of these are different, the height L _{4 of} the radiation conductor plates 1A and 1B with respect to the ground plane 6 and the resonance. Similar effects can be obtained by appropriately selecting constants such as the capacitances of the control capacitive elements 4A and 4B. Further, the capacitive elements 2, 4A and 4B may be constructed by a distributed element configured by a printed conductor on the substrate instead of the lumped element. Second Embodiment FIG. 5 shows a second embodiment of the present invention, which is a case where the number of ground metal plates 5 is one. Two radiation conductor plates 1A, 1
B have the same right-angled quadrilateral shape and the same size, and are provided so as to face each other with the dielectric plate 20 having the same shape interposed therebetween. Further, in this example, both ends of the coupling control capacitive element 2 are connected to the sides of the radiation conductor plates 1A and 1B to which the ground metal plate 5 is connected. The resonance controlling capacitive element 4B for one radiation conductor plate 1B is connected to the midpoint of the side adjacent to the side to which the ground metal plate 5 is connected.
The resonance frequencies due to these two radiation conductor plates 1A and 1B are the capacitances C ₁ and C _{2 of the} resonance control capacitive elements 4A and 4B, respectively.
Has been adjusted to the desired value. In this example C ₁ = 0.5
pF and C ₂ = 1pF. The capacitance C ₀ of the coupling control capacitive element 2 is C ₀
= 0.5pF. The dimensions of each part shown in the figure are L ₁ = L ₂ = 30
mm, L ₃ = 1.6 mm, L ₄ = 5 mm, and the relative permittivity of the dielectric plate 20 is ε _r = 2.6. The position of such a capacitive element and the dimension of each part are obtained as a result of experimental examination. By doing so, a small-sized and wide-band dual-frequency resonant antenna device can be realized.

FIG. 6 shows the return loss frequency characteristic of the antenna device shown in FIG. In this case as well, the measurement was carried out by mounting on a rectangular metal case of 130 × 40 × 20 mm. It is apparent from Fig. 6 that resonance occurs at two points of about 820MHz and 875MHz. Moreover, when the efficiency of this antenna was measured, it was -1.2 at 820MHz.
It was a very high value of -0.9 dB at 875 MHz. As described above, even when the number of the ground metal plates 5 is one, the present antenna device is a very small antenna, yet it can resonate at any two frequencies and has a high gain. Was confirmed by experiments. Third Embodiment FIG. 7 shows a third embodiment of the present invention in which right-angled quadrangular radiating conductor plates 1A and 1B are miniaturized, and the opposing sides thereof are short-circuited metal plates 1C over the entire length thereof. This is the case when connected. The short-circuit metal plate 1C is connected to the base plate 6 by a ground metal wire 5 at the center in the length direction, and the coaxial power supply line 3 is connected to the short-circuit metal plate 1C. The resonance control capacitors 4A and 4B are open end sides 1 facing the short-circuit metal plate 1C.
The coupling control capacitance element 2 is connected to the opposite ends of a and 1b, and to the midpoint between the open end sides 1a and 1b. With such a configuration, it is possible to realize a more compact and wideband dual-frequency resonant antenna device.

FIG. 8 shows the return loss frequency characteristic of the antenna device of FIG. The dimensions of each part of this antenna device and the capacitance of the capacitive element are L ₁ = L ₂ = 25mm, L ₃ = 0.6mm, L ₄ = 5mm, C ₀ = 2
pF, C ₁ = 0.4pF, C ₂ = 0.3pF, and the relative permittivity of the dielectric plate 20 is ε _r = 2.6. Also in this case, it is installed on the same rectangular metal housing as in the previous embodiment. Although it is very small, it obviously resonates at two points of about 818MHz and 875MHz. However, each bandwidth is rather narrow. The effect in this case is similar to that of the above embodiment. Fourth Embodiment FIG. 9 shows a fourth embodiment of the present invention, which corresponds to the third embodiment of FIG.
In the embodiment, on the lower side of the short-circuit metal plate 1C, a triangular taper metal plate 7 connected from one end thereof to the connection point of the ground metal wire 5 as one side is arranged vertically extending toward the main plate 6, This is a case where the lower end apex of the triangle is configured to face the base plate 6 with a space therebetween, and the coaxial feed line 3 is connected to the lower end apex of the triangular metal plate 7 via the impedance adjusting capacitor 8. By feeding power from the apex of such a triangular metal plate 7, resonance characteristics with a wide band can be obtained. Furthermore, it is possible to realize a compact and wideband dual-frequency resonant antenna device.

The return loss and VSWR measurement results in this case are shown in FIGS. 10A and 10B, respectively. The dimension parameter of the antenna is the same as that of the third embodiment shown in FIG. As you can see in the figure, although it is very small, it is clearly about 818 MHz.
And resonate at two points of 875MHz. Characteristics of Example 3 (FIG. 7)
Compared with, the resonance band of 818MHz is a little narrower, and the resonance band of 875MHz is considerably wider. In this case, VSWR <2.5 at each marker point. Fifth Embodiment FIG. 11 shows a fifth embodiment of the present invention in which each capacitive element is arranged on the ground plane 6 and these capacitive elements are connected to each radiation plate by a metal wire. The short-circuit metal plate 1C connects the two radiation conductor plates 1A and 1B to each other over the entire lengths of the corresponding one side, and the short-circuit metal plate 1C and the ground plate 6 are connected to the central conductor and the outer conductor of the coaxial feeder line 3, Further, the point that the short-circuit metal plate 1C and the ground plate 6 are connected by the ground metal wire 5 is similar to the embodiment of FIG. In this embodiment, the radiation conductor plates 1A and 1B are used.
Metal lead wires 9A and 9B respectively connected to opposite ends of the open end sides 1a and 1b of the are provided to extend toward the base plate 6, and the open end side 1a of the radiation conductor plate is provided on the upper surface of the base plate 6. 1b is bent at a right angle on a rectangular insulating spacer 11 provided so as to face the metal lead wires 10A, 10b.
As B, they are further extended on the spacer 11 so as to approach each other. Resonance control capacitive elements 4A and 4B have one terminal connected to each of the bending points from metal lead wires 9A and 9B to 10A and 10B, and the other terminal connected to the ground plane. The ends of the metal lead wires 10A and 10B are opposed to each other with a space therebetween, and one end and the other terminal of the coupling control capacitive element 2 are connected to these ends.

Thus, the metal lead wires 9A, 9B, 10
By using A and 10B, the capacitive elements 2 and 4A and 4
Since B can be mounted on the main plate 6 via the spacer 11 or directly on the main plate 6 together with other components (not shown) of the radio in the same step, the manufacturing efficiency is improved, which is convenient. FIG. 12 shows the measurement result of the return loss of the antenna device according to the embodiment of FIG. The dimensions of each part of the antenna device are L ₁ = L ₂ = 30 mm, L ₃ = 1.6 mm, L ₄ = 5 mm. The capacitance of each capacitor is C ₀ = 1.5pF, C ₁ = 0.3pF, C ₂ = 0.8pF. As is clear from this figure, even if the capacitive element is arranged on the ground plane, the two-resonance characteristic is clearly shown as in the above-mentioned embodiment. Sixth Embodiment FIG. 13 shows a sixth embodiment of the present invention. In this embodiment, two radiation conductor plates 1A and 1B are formed on the same surface of a rectangular quadrilateral dielectric plate 20 with a distance D therebetween. The ground metal plate 5 extending over the entire length of one side wall surface of the dielectric plate 20 extending in the arrangement direction of the two radiation conductor plates 1A and 1B.
Is provided, the upper side of which is two radiation conductor plates 1A and 1B.
Is connected to the entire length of one side, and the lower side is connected to the main plate 6. Further, a metal plate 1C having a width W for connecting the two radiation conductor plates 1A and 1B is formed by connecting the ground metal wire 5 and the side edge in the same plane as those. The resonance controlling capacitive elements 4A and 4B are connected between the grounded plate 6 and one ends of the open end sides 1a and 1b of the radiation conductor plates 1A and 1B, which are separated from each other. On the other hand, the coupling control capacitive element 2 has 2
It is connected between the open ends 1a and 1b of the two radiation conductor plates 1A and 1B in the vicinity of one ends which are close to each other. The center conductor of the coaxial feeder 3 is connected to the outer side of one radiation conductor plate, here, 1B, but may be connected to the inner side. Also with this configuration, it is possible to realize a dual-frequency resonant antenna device that is a flat plate and has a wide band.

FIG. 14 shows the return loss measured for the antenna device of the embodiment shown in FIG. The dimensions of each part are L ₁ = L
_{2 = 30mm, L 3 = 4.8mm} , D = 1mm, a W = 3 mm. The capacitance of each capacitor is C ₀ = 2.0pF, C ₁ = 0.8pF, C ₂ = 1.1pF. As is clear from this figure, resonance is shown at 820 MHz and 875 MHz. In this way, the two radiation conductor plates 1A and 1B are only 1 mm
Even in the case of the antenna devices arranged in parallel on the same plane at intervals of, it is possible to resonate at two frequencies close to each other as in the above embodiment, and a small-sized and high-gain antenna can be obtained.

The radiation conductor plates 1A and 1B in the embodiments of FIGS. 3, 5, 7, 9 and 11 may be arranged in parallel on the same plane as in FIG. Seventh Embodiment FIG. 15 shows a seventh embodiment of the present invention, which is a case where a whip antenna and the antenna of the present invention constitute a diversity. The antenna 50 according to the present invention and the whip antenna 12 are installed so that the polarization directions 50A and 12A at which the respective gains are maximum are orthogonal to each other. Here, 1 to 10 are the same as in the above embodiment,
Reference numeral 2 is a whip antenna, 13 is a radio housing, 14 is a feed wire for the whip antenna, and 15 is an internal radio circuit.
By arranging the two antennas in this way, the coupling between the whip antenna 12 and the antenna 50 of the present invention is reduced and the mutual gain is increased as a whole, while maintaining the wide band characteristic of the antenna 50 of the present invention. . This is because the polarized waves of the whip antenna and the built-in antenna are orthogonal to each other.

In other words, this example is also a small-sized and high-gain antenna that can resonate at any two frequencies, and is also high when another antenna is used in combination such as a diversity structure. Gain is obtained.

[0021]

As described above, in the present antenna device, the capacitive element 2 is connected between the two radiating conductor plates 1A and 1B for controlling their coupling, and the radiating conductor plates and the ground plate are connected to each other. By connecting the capacitive elements 4A and 4B for resonance control as needed, it is possible to resonate at any two frequencies, and even when resonating at two frequencies very close to each other, the spacing between the radiation conductor plates is Since it can be narrowed, the antenna does not become large, and it is possible to provide a small-sized and wideband or two-resonant antenna device.

[Brief description of drawings]

FIG. 1 is a perspective view of a conventional antenna device.

FIG. 2 is a perspective view showing another example of a conventional antenna device.

FIG. 3 is a perspective view showing a first embodiment of the present invention together with a metal housing.

4 is a diagram showing a return loss frequency characteristic of the antenna device of FIG.

FIG. 5 is a perspective view showing a second embodiment of the present invention.

6 is a diagram showing a return loss frequency characteristic of the antenna device of FIG.

FIG. 7 is a perspective view showing a third embodiment of the present invention.

8 is a diagram showing a return loss frequency characteristic of the antenna device of FIG.

FIG. 9 is a perspective view showing a fourth embodiment of the present invention.

10A is a diagram showing a return loss frequency characteristic of the antenna device of FIG. 9, and FIG. 10B is a diagram showing a VSWR frequency characteristic of the antenna device of FIG.

FIG. 11 is a perspective view showing a fifth embodiment of the present invention.

12 is a diagram showing a return loss frequency characteristic of the antenna device of FIG.

FIG. 13 is a perspective view showing a sixth embodiment of the present invention.

14 is a diagram showing a return loss frequency characteristic of the antenna device of FIG.

FIG. 15 is a perspective view showing a seventh embodiment of the present invention.

Claims (18)

[Claims] 1. A ground plane, a dielectric plate arranged parallel to the ground plane, and a dielectric plate disposed on the dielectric plane parallel to the ground plane with a space therebetween, and one end of each of which is electrically grounded to the ground plane. At least two radiating conductor plates, a feed line having a central conductor and an outer conductor, which are substantially connected to at least one of the two radiating conductor plates and the ground plate, respectively, and the two radiating conductors A coupling control capacitive element connected between the plates, wherein the capacitance of the coupling control capacitive element is a current coupled from one of the two radiation conductor plates to the other;
A dual-frequency resonant antenna device in which currents supplied from the one radiation conductor plate to the other radiation conductor plate via the coupling control capacitive element are selected so as to have mutually opposite phases in the other radiation conductor plate. . 2. The dual-frequency resonant antenna device according to claim 1, wherein the two radiating conductor plates are provided on one surface and the other surface of the dielectric plate that face each other, and the dielectric plate is the ground plate. And are arranged in parallel at intervals. 3. The dual-frequency resonant antenna device according to claim 1, wherein the two radiating conductor plates are arranged at intervals on the same plane of the upper surface of the dielectric plate arranged on the base plate. . 4. The dual-frequency resonant antenna device according to claim 1, 2 or 3, wherein at least one of the two radiation conductor plates and the ground plate are provided with a first one for resonance control of the one radiation conductor plate. Is connected to the resonance controlling capacitive element. 5. The two-frequency resonance antenna device according to claim 4, wherein a second resonance control capacitor is provided between the other of the two radiation conductor plates and the ground plate for resonance control of the other radiation conductor plate. The elements are connected. 6. The dual-frequency resonant antenna device according to claim 1, 2 or 3, wherein the metal lead wires respectively connected to the two radiating conductor plates are close to the ground plate and the tips are close to each other. The capacitive element for coupling control is extended and connected between the tip portions of the metal lead wires. 7. The dual-frequency resonant antenna device according to claim 6, wherein the metal lead wires are wired such that the upper surfaces of the insulating spacers provided on the ground plane are extended so as to be close to each other, and the metal spacers are provided on the insulating spacers. A resonance controlling capacitance element is connected between at least one of the metal lead wires wired to the base plate and the ground plane. 8. The dual-frequency resonant antenna device according to claim 1, 2 or 3, wherein the two radiating conductor plates are quadrilaterals in which at least one side is parallel to each other, and the parallel sides are respectively the ground plane. Metal grounding means for grounding is provided. 9. The dual-frequency resonant antenna apparatus according to claim 8, wherein the metal grounding means connects at least a part of each of the two parallel sides of the two radiation conductor plates to the ground plane. Includes a ground metal plate. 10. The dual-frequency resonant antenna device according to claim 8, wherein the metal grounding means short-circuits metal plates that short-circuit the parallel sides of the two radiating conductor plates over the entire length, and the short-circuit metal. It includes a plate and a ground metal wire connecting the ground plate. 11. The dual-frequency resonant antenna device according to claim 8, wherein the metal grounding means includes a short-circuit metal plate that short-circuits the parallel sides of the two radiating conductor plates to each other over the entire length. One side of the metal plate is connected to the base plate. 12. The dual-frequency resonant antenna device according to claim 2, wherein the two radiating conductor plates are quadrilaterals having at least one side parallel to each other, and face the mutually parallel sides of the two radiating conductor plates. The sides to be done are not parallel to each other. 13. The dual-frequency resonant antenna device according to claim 12, wherein the non-parallel sides have inclinations opposite to each other with respect to the parallel sides and intersect each other. 14. The dual-frequency resonant antenna device according to claim 10, wherein the center conductor of the feed line is electrically connected to the short-circuit metal plate. 15. The dual-frequency resonant antenna device according to claim 13, wherein a triangular taper metal plate having one side connected to the short-circuit metal plate and having a vertex opposite to the one side and closely facing the ground plate is provided. A central conductor of the power supply line is electrically connected to the apex of the tapered metal plate. 16. The dual-frequency resonant antenna device according to claim 15, wherein the center conductor of the feed line is connected to the apex of the tapered metal plate via an impedance control capacitive element. 17. The dual-frequency resonant antenna device according to claim 10, wherein the coupling control capacitive element is connected between sides of the two radiating conductor plates that face the mutually parallel sides, respectively. 18. The dual-frequency resonant antenna device according to claim 1, 2 or 3, which is used in combination with a whip antenna and is arranged such that the polarization direction is orthogonal to the polarization direction of the whip antenna. An antenna device characterized by the above.