JPH05315828A - Microstrip antenna - Google Patents

Abstract

PURPOSE:To realize the microstrip antenna capable of receiving plural frequencies close to each other having small sized and simple structure. CONSTITUTION:A 2nd radiation conductor 24 having an open ring formed by truncating part of a torus is arranged in the inside of a torus of a 1st radiation conductor 22 shaped to be the torus. It is possible to decrease the resonance frequency of the torus having the same inner and outer diameter to nearly a half and the resonance frequency is approached to that of the 1st radiation conductor 22 by the decrease.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to microstrip antennas, and more particularly to microstrip antennas operating at different frequencies.

[0002]

2. Description of the Related Art Microstrip antennas (hereinafter referred to as MS
The abbreviation "A") has recently been utilized as an antenna for sanitary communication or a global positioning system (GPS) because of its characteristic that it can be miniaturized. Furthermore, an MSA having a plurality of frequency characteristics according to the intended use for use for a plurality of purposes
Is being developed.

One of them is a method of laminating MSA as shown in FIG. Substrate 1 formed of dielectric
A first radiation conductor 12 is provided on the surface of No. 1, and a dielectric 13 and a second radiation conductor 14 are further provided on this first radiation conductor 12. Further, the ground conductor plate 15 is provided on the back surface of the substrate 11.
Is provided. These two radiation conductors 12, 14
The respective frequencies are set to different frequencies, and by supplying microwaves to each, MSAs having different resonance frequencies are obtained. However, in this MSA, the structure is complicated because two radiation conductors are laminated.

Also, the second radiation conductor 14 is the first radiation conductor 1.
The directivity of the first radiation conductor 12 in order to cover a part of 2
It may affect characteristics such as output. In order to reduce this effect, the second radiation conductor 14 is provided with the first radiation conductor 12
Can not take more than a certain size.
Therefore, the frequency that depends on the dimensions of the radiating conductor is
The two radiating conductors can only be set to some distance apart. That is, such a stacked MSA has a problem that it cannot transmit or receive frequencies close to each other.

Further, as the MSA having a plurality of frequency characteristics, the stub 12a and the short pin 16 shown in FIGS.
There is a method of additionally obtaining a plurality of resonance frequencies.
However, the newly provided stub 12a and the short pin 16 may affect the original fundamental resonance mode and disturb the radiation characteristics such as the resonance frequency and the directivity and the axial ratio. Further, since the shape of the radiation conductor is complicated, the analysis of the electromagnetic resonance mode is very complicated, and it is difficult to predict its performance at the design stage. Therefore, we have to rely on tests to make decisions such as setting frequencies.
Further, even when it is mass-produced, problems such as its quality control are included.

In contrast to the above method, by providing another radiation conductor in the hole portion of the ring-shaped radiation conductor and changing the setting of each frequency, it is possible to receive a plurality of frequencies.
A method for obtaining SA is disclosed in JP-A-1-189208. As shown in FIG. 9, a ring-shaped first radiation conductor 17 and a circular second radiation conductor 18 are provided inside the first radiation conductor 17. Since each radiating conductor has a different shape and size, a plurality of frequencies can be set by selecting them, and a simple structure can be achieved.

[0007]

However, in the conventional method of providing another patch inside the ring-shaped radiation conductor, there are the following restrictions on the frequency setting of each of the two radiation conductors. There was a problem that the degree of freedom was low.

It is necessary for the first radiation conductor 17 to match the impedance of the fundamental resonance mode with the impedance of the feeding circuit, and if this is set, the inner diameter of the ring will be determined. Therefore, the second provided inside the ring
The radiation conductor 18 must be set to a size equal to or smaller than the inner diameter of the ring. Therefore, the resonance frequency of the second radiation conductor 18 is considerably higher than that of the first radiation conductor 17. It is possible to increase the inner diameter of the ring while matching the impedance by using the short pin, but as described above, the design of the setting of the short pin is not easy, and the structure becomes complicated in the end. In addition, by setting the resonance mode of the first radiation conductor to the TM ₂₁ mode,
The ring can be made larger than in the case of the M ₁₁ mode, but in this case, the outer diameter of the ring becomes about twice and the apparatus becomes large.

As described above, the conventional apparatus has a low degree of freedom in setting the frequency of the radiation conductor, and this cannot be realized by a simple structure, especially when the two frequencies to be set are close to each other. There was a problem.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to realize an MSA having two frequencies with a small and simple structure and to provide it.

[0011]

In order to achieve the above-mentioned object, a microstrip antenna according to the present invention comprises:
A substrate formed of a dielectric material, a ground conductor plate formed on the back surface of the substrate, a first radiation conductor having an annular shape provided on the surface of the substrate, and a surface of the substrate, It has a second radiating conductor which is provided in a portion surrounded by one radiating conductor and has a shape in which a part of a circular ring is cut out, and a feeding circuit which supplies electric power to the two radiating conductors.

[0012]

The present invention has the above-mentioned configuration, and
It is possible to set the set frequencies of the radiation conductor and the second radiation conductor separately, and in particular, by making the second radiation conductor a shape in which a part of the ring is cut out, the frequency of the second radiation conductor becomes lower, The frequency can be set close to the frequency of the first radiation conductor.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the MSA according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of the embodiment, and FIG. 2 is a partially cutaway perspective view. The first radiation conductor 2 is formed on a part of the surface of the substrate 21 made of a dielectric material.
2 and the second radiation conductor 24 are provided. That is, the area of the substrate 21 is larger than the total area of the two radiation conductors 22 and 24. Further, the ground conductor 20 is provided on the back surface of the substrate 21, that is, the surface on the half body side of the surface provided with the radiation conductors 22 and 24. The ground conductor 20 covers the entire back surface of the substrate 21, and a through hole 20a through which the power supply pin 25 penetrates is provided in a part of the ground conductor 20. The first radiating conductor 22 has an annular shape.
Two power supply pins 25 are connected to each other, and electric power is supplied from the first power supply 27 through the duplexer 26 with a phase difference of 90 °. As a result, the first radiation conductor 2
2 can radiate circularly polarized waves. Second radiation conductor 24
Is a shape having a cutout portion 24a in a part of the ring, a power supply pin 28 is provided at a position facing the cutout portion 24a, and power is supplied by a second power feeder 29.

The inner diameter of the first radiation conductor has a fixed value because it is necessary to match the impedance in the resonance mode desired to be used with the impedance of the feeding circuit, which is extremely low in design freedom. Also in the second radiation conductor 24 arranged inside the first radiation conductor 22, the outer diameter thereof is restricted and the degree of freedom in design is low. Therefore, in the present invention, the second radiation conductor 24 has an open ring shape in which a part of the circular ring is cut out. This makes it possible to obtain a lower resonance frequency for an antenna having an annular shape having the same outer diameter and inner diameter. For example, as shown in FIG. 3, the central angle is αrad
The resonance frequency f of the open-ring-shaped radiation conductor in the TM ₁₁ mode is related to the resonance frequency f _c of the ring-shaped radiation conductor having the same outer diameter and inner diameter as shown in the following equation. f = (π / α) f c

Therefore, the central angle α as shown in FIG. 3 is 2
When the open ring type is close to π, the resonance frequency is about 1 /
It can be 2. That is, since the shape is large, the first radiation conductor 24 having the lower resonance frequency
It is possible to set a resonance frequency closer to the resonance frequency of the radiation conductor 22.

The directional characteristic of such an open ring type radiation conductor is in the direction of arrow A in the figure on the opposite side of the notch 24a as shown in FIG. Since this open-ring type antenna has such directional characteristics,
It is particularly suitable for receiving radio waves from a sign post installed along the road and receiving beacons.
On the other hand, the first radiation conductor 22 has a maximum gain in the zenith direction in the TM ₁₁ mode and has a relatively wide directional characteristic, and therefore is suitable for a satellite antenna such as GPS.

From such characteristics, M shown in this embodiment
The SA can receive GPS of 1.5 GHz by the first radiation conductor 22 and can receive the beacon of 2.5 GHz installed along the road by the second radiation conductor 24. Thus, even when the two frequencies to be received are relatively close to each other, it is possible to arrange the second radiating conductor inside the first radiating conductor by using the open ring type, and to arrange a plurality of small and simple structures. An MSA having a reception frequency can be realized.

Next, a second embodiment will be described with reference to FIG. The present embodiment differs from the first embodiment in that the first radiation conductor 31 has a degenerate separation element 31a, and the feed pin 32 is provided at a position separated by 45 ° from the degenerate separation element 31a. Then, from the power feeder 27, the power feeding pin 32
Power is supplied to the first radiating conductor via. This allows the first radiation conductor 31 to transmit and receive circularly polarized waves as in the first embodiment. Further, two second radiating conductors 33 are provided, and the electric power distributed from the power feeder 36 by the distributor 35 is supplied to the two second radiating conductors via the power feeding pin 34, and the two radiating conductors are not unidirectional. It is possible to construct an MSA having directional characteristics in the vertical direction in the figure.

Further, in the above-mentioned embodiments, the method of feeding the electric power by the feeding pin is shown, but it is of course possible to feed the electric power by using the electromagnetic coupling.

[0020]

As described above, by arranging the open ring type MSA inside the annular MSA, two radiating conductors having a relatively close resonance frequency can be arranged in a small size, which is simple and easy. MSA with a simple structure
Can be configured.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a microstrip antenna according to the present invention.

FIG. 2 is a diagram showing an embodiment of a microstrip antenna according to the present invention, and is a partially cutaway perspective view.

FIG. 3 is a diagram for explaining characteristics of an open ring type microstrip antenna.

FIG. 4 is a diagram showing directional characteristics of an open ring type microstrip antenna.

FIG. 5 is a diagram showing a configuration of a second exemplary embodiment according to the present invention.

FIG. 6 shows a conventional microstrip antenna, particularly a stacked antenna.

FIG. 7 shows a conventional microstrip antenna, particularly an antenna using a stub.

FIG. 8 shows a conventional microstrip antenna, particularly an antenna using a short pin.

FIG. 9 shows a conventional microstrip antenna, in particular, an antenna in which a second radiation conductor is arranged inside a circular ring-shaped first radiation conductor.

[Explanation of symbols]

 21 substrate 22 first radiation conductor 24 second radiation conductor

Claims (1)

[Claims] 1. A substrate formed of a dielectric material, a ground conductor plate formed on the back surface of the substrate, a first radiation conductor having an annular shape provided on the front surface of the substrate, and a front surface of the substrate. And a second radiation conductor provided in a portion surrounded by the first radiation conductor, the second radiation conductor having a shape in which a part of a ring is cut out, and a power supply circuit that supplies power to the two radiation conductors. A microstrip antenna having.