JPH0770888B2 - Micro strip antenna - Google Patents

Description

The present invention relates to a microstrip antenna, and more particularly to a microstrip antenna that can be shared by two frequencies.

[Conventional technology]

A microstrip antenna in which a radiating element is composed of a microstrip consisting of a ground conductor plate and a radiating conductor plate arranged in parallel with the ground conductor plate via a dielectric layer or an air layer, has a flat radiating element. -Suitable for attaching a radiating element to the outer surface of a satellite or the like.

[Problems to be Solved by the Invention] Since a conventional microstrip antenna has a high Q and a narrow bandwidth, it cannot be shared by two frequencies such as a transmission frequency and a reception frequency of a wireless communication device. There are drawbacks.

It is an object of the present invention to provide a microstrip antenna that solves the above drawbacks and can be shared by two frequencies.

[Means for solving problems]

The microstrip antenna of the present invention includes a ground conductor plate,
A radiating element comprising a radiating conductor plate arranged in parallel to this ground conductor plate, and a first end is connected to the feeding end of this radiating element, and the admittance of the radiating element side seen from the second end. , A first transmission line of a length such that the conductance component is equal at two predetermined frequencies and the susceptance component is greater at the lower frequency of the two frequencies and at the higher frequency, and at one end Open or short-circuited, the other end is connected in parallel to the second end of the first transmission line, from this parallel connection point, the susceptance looking at the open or shorted end side, and the radiation A second transmission line having a length such that a combined admittance with the admittance seen from the element side is equal at the two frequencies.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating an embodiment.

FIG. 1 is a perspective view showing a first embodiment of the microstrip antenna of the present invention.

The embodiment shown in FIG. 1 includes a radiating element 1, a coaxial line 2,
The tuning circuit 3 is provided.

The radiating element 1 is configured as a microstrip including a dielectric plate 11, and a ground conductor plate 12 and a radiating conductor plate 13 attached to both surfaces of the dielectric plate 11.

The coaxial line 2 has a connector 21 at one end, and the other end is connected to the feeding end 14 of the radiating element 1.

The tuning circuit 3 includes a dielectric plate 31, a ground conductor plate 32 attached to one surface of the dielectric plate 31, a line conductor 33, a line conductor 34, and an impedance attached to the other surface of the dielectric plate 31. A microstrip having a converter 35 and a stub 36, and connectors 37 and 38 are provided. One end of the line conductor 33 is connected to the connector 37, and the other end (hereinafter, this end is referred to as a connection point A) has an impedance converter 35 and a stub 36.
Is connected to one end of. The other end of the impedance converter 35 is connected to the connector 38 via the line conductor 34, and
The other end of 36 is open. The tuning circuit 3 and the coaxial line 2 are connected by connectors 37 and 21. Tuning circuit 3
Connector 38 is connected to a power supply line (not shown).

2 and 3 are Smith charts for explaining the operation of the embodiment shown in FIG. Curves a, c, d and arc b in the figure are loci with the frequency as a parameter of the admittance of each part normalized by the characteristic admittance of the feeder.

Two frequencies embodiment shown in Figure 1 is used _1-
2 ( ₁ < ₂ ). Radiating element 1 has frequency _1
The dimensions of each part of the radiating element 1 are set so as to resonate at a frequency approximately at the center of ₂ . With this setting, the radiating element 1 can be regarded as a parallel resonant circuit that resonates at this resonant frequency when viewed from the feeding end 14.

The characteristic admittance of the transmission line by the line conductors 33 and 34 and the coaxial line 2 is made equal to the characteristic admittance of the feeder line. As viewed radiating element 1 side from the connection point A admittance becomes as curve a shown in FIG. 2, i.e., G-jB ₂ at the frequency ₁ G + jB _1, the frequency ₂
The distance l ₁ from the feeding end 14 to the connection point A is set so that (B ₁ > −B ₂ ).

As admittance viewed stub 36 from the connection point A becomes as arc b illustrated in FIG. 2, i.e., frequency ₁
At −jB ₁ and at frequency ₂ jB ₂ ,
The length l ₂ of the stub 36 and the characteristic admittance of the stub 36 transmission line are set.

By setting the dimensions of each part of the radiating element 1, the length of the coaxial line 2 and the line conductor 33 (that is, the distance l ₁ ) and the length l _{2 of the} stub 36 and the characteristic admittance as described above, the radiating element from the connection point A The combined admittance of the admittance as seen on the 1st side and the stub 36 is as shown by the curve C in FIG. 3, and has the same value G at frequencies ₁ and ₂ .

The impedance converter 35 is a known λ / 4 impedance converter and converts the admittance locus of the curve C into the admittance locus of the curve d. As a result of this conversion, the connector
Since the admittance when viewed from the inside from 38 becomes 1 at frequencies ₁ and ₂ , the embodiment shown in FIG.
It is matched to the feed line in _one-2.

The length and characteristic admittance of the stub whose tip is short-circuited to the ground conductor plate 32 are set so that the admittance locus thereof matches the arc b shown in FIG.
It can be used instead of 36. Although the coaxial circuit 3 is configured as a microstrip, a tuning circuit having the same function as this can be configured by combining coaxial lines.

In the embodiment shown in FIG. 1, the combined admittance at the connection point A (curve C in FIG. 3) has a conductance G at frequencies ₁ and ₂ , and the susceptance component is 0. However, at both frequencies, the combined admittance is Equalization is essential to the invention, and elimination of the susceptance component is not necessary. The length and characteristic admittance of the stub 36 may be different from those described above as long as the combined admittance is the same at both frequencies. When the susceptance component of the combined admittance remains in this way, a line conductor of a certain length is inserted between the connection point A and the impedance converter 35 so that the connection point A side is seen through this line conductor. The admittance can be equal at both frequencies and the susceptance component can be zero. It goes without saying that the impedance converter 35 is unnecessary when the combined admittance is equal to the characteristic admittance of the feeder.

FIG. 4 is a vertical sectional view showing a second embodiment of the microstrip antenna of the present invention.

In the embodiment shown in FIG. 4, the ground conductor plate 4, the dielectric plates 5 and 6 attached to both surfaces of the ground conductor plate 4, and the radiation conductor plate 7 attached to the outer surfaces of the dielectric plates 5 and 6. -Circuit conductor 8 and center conductor 9 that connects radiation conductor plate 7 and circuit conductor 8;
And a connector 10 connected to the circuit conductor 8.

A microstrip composed of the ground conductor plate 4, the dielectric plate 5, and the radiation conductor plate 7 constitutes a radiation element. One end of the center conductor 9 is connected to the feeding end of this radiating element.

The circuit conductor 8 is the coaxial line 2 in the embodiment shown in FIG.
-Line conductor 33-Line conductor 34-Impedance converter 35-
It has parts corresponding to the stubs 36, respectively. The microstrip consisting of the ground conductor plate 4, the dielectric plate 6, and the circuit conductor 8 is connected to the radiation conductor plate 7 by the central conductor 9, and is the same as the coaxial line 2 and the tuning circuit 3 in the embodiment shown in FIG. It operates and is connected to a power supply line (not shown) by the connector 10. It is the same as in the embodiment shown in FIG. 1 that the embodiment shown in FIG. 4 is matched to the feed line at two working frequencies.

〔The invention's effect〕

As described in detail above, the microstrip antenna of the present invention includes a radiating element composed of microstrip, a second transmission line, and a first transmission line inserted between the radiating element and the second transmission line. And by setting the lengths of these first and second transmission lines to equalize the combined admittance at the parallel connection points of these first and second transmission lines at two operating frequencies, Since it is possible to match the feed line at these two operating frequencies, there is an effect that it can be shared by these two operating frequencies, and since it can be configured with microstrips or coaxial lines without using lumped constant elements, the microstrip antenna can be used. It has the effect that matching can be easily achieved even at high frequencies used, and that it can be made compact and lightweight. There is.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of the microstrip antenna of the present invention, FIGS. 2 and 3 are Smith diagrams for explaining the operation of the embodiment shown in FIG. 1, and FIG. The drawing is a longitudinal sectional view showing a second embodiment of the microstrip antenna of the present invention. 1 ... Radiating element, 2 ... Coaxial line, 3 ... Tuning circuit, 11
・ 31 …… dielectric plate, 12 ・ 32 …… ground conductor plate, 13 …… radiating conductor plate, 14 …… feeding end, 33 …… line conductor, 36 …… stub,
A: Connection point.

Claims (1)

[Claims] 1. A radiating element comprising a ground conductor plate and a radiating conductor plate arranged parallel to the ground conductor plate; a first end connected to a feeding end of the radiating element; and a second end. From the radiating element side, the conductance component becomes equal at two predetermined frequencies, and the susceptance component becomes larger at a lower frequency of the two frequencies than at a higher frequency. One transmission line and one end thereof is opened or short-circuited, the other end is connected in parallel to the second end of the first transmission line, and the parallel connection point is opened or short-circuited. A second transmission line having a length such that a combined admittance of the susceptance viewed from the end side and the admittance viewed from the radiating element side is equal at the two frequencies; Microstrip antenna and butterflies.