JPH0349404A - Microstrip antenna - Google Patents

Abstract

PURPOSE:To obtain a microstrip antenna for circular polarization with a wide and satisfactory elliptical polarization rate by forming a radiation conductor board in a shape for which recessed and projecting parts are provided on the circumference of a disk. CONSTITUTION:For the shape of a radiation conductor board 2, recessed parts 5 are provided on the circumference of parts, where the first straight line A-A' passing through the center of the disk crosses the circumference on this disk and projecting parts 6 are provided on the circumference of parts, where the second straight line B-B' orthogonally crossing with the line A-A' and passing through the center of the disk crosses the circumference of this disk. Such a radiation conductor board 2 is insulated from a ground conductor board 3, faced each other and almost parallelly arranged and prescribed angles are respectively formed to the two straight lines. Then, a feeding circuit 4 is provided with feeding points on the straight lines passing through the center of the disk. Accordingly, displacement from a resonance frequency f0, which is provided before the recessed parts 5 and projecting parts 6 with respective resonance frequencies fa and fb in two modes to be spatially orthogonal, can be made equal and small and the deviation of a frequency characteristic can be reduced for the amplitude and phase of radiative electric fields in two modes. Thus, the microstrip antenna can be obtained with the wide-band elliptical polarization rate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a microstrip antenna for circularly polarized waves.

[Conventional technology]

Conventionally, there has been a device of this type as shown in FIG. This figure is JP-A-6L-281704R 8HF
This figure is shown in the band planar antenna J, and FIG. 11A is a front view, and FIG. In the figure, (1) is a dielectric substrate, (2) is a dielectric substrate (
(1) is a radiation conductor plate formed on one side of the dielectric substrate (1), and (3) is a ground conductor plate formed on the other side of the dielectric substrate (1).

(4) is the feed strip conductor, (5) is the radiation conductor plate (
2). Here, the radiation conductor plate (2
) is provided on the circumference of the portion where the circumference intersects the straight line A+A/ on this disk passing through the center 0 of the disk. Further, the power feeding strip conductor (4) forms an angle of 45° with the straight line A-A', and is arranged on the radiation conductor plate so that power is supplied from a point F on the straight line passing through 0 on the radiation conductor plate (2). (2) is connected. Note that the power feeding strip conductor (4) constitutes a microstrip line together with the ground conductor plate (3).

Now, the operation of a microstrip antenna that excites normal linearly polarized waves will be explained.

Figure 9 is a diagram to clarify the operation of the microstrip antenna! I, (21 is a radiating conductor plate made of a disc with no directionality, (4) is a power feeding space) IJ tube conductor. The radio waves propagating through the microstrip line excites the microstrip antenna.

Figure (a) shows the direction of the main resonant current flowing on the radiation conductor plate (4) of the microstrip antenna with arrows.
It has an input impedance characteristic as shown in b), and is represented by an equivalent circuit as shown in FIG. Than this,
As shown in the figure (kl), the resonance frequency f.

It exhibits inductive impedance characteristics at frequencies lower than , and capacitive impedance characteristics at frequencies higher than FO. Also.

In the same figure (c), the current flowing through the radiation resistor H advances because the inductance L is connected in parallel at frequencies lower than the resonant frequency, and the capacitance C is connected in parallel at frequencies higher than the resonant frequency. I'm late because of this. Therefore,
When this microstrip antenna is excited at frequency f0, linearly polarized waves are radiated from the radiation conductor plate (2).

Next, the operation of the circularly polarized wave microstrip antenna shown in FIG. 8 related to circularly polarized wave generation will be explained.

FIG. 10 is a diagram showing the direction of current flowing on the radiation conductor plate (2) when power is supplied from point F in FIG. 8.

(21, (4), (51 indicates the same thing as in Figure 8.

The direction of current flow is indicated by an arrow. Note that the straight line B-zo passes through the center 0 and is orthogonal to the straight line A-A'. Figure (a) shows the direction of the main current flowing on the radiation conductor plate (2). This first flow consists of two spatially orthogonal modes a
(b) and (c) in the same figure are the main current directions of mode a and mode b, respectively.
Mode a is in the straight line A-A' direction, mode b is in the straight line B-
B'There is a force direction. Considering mode a and mode b separately as above, the resonant frequency fa of mode a is higher than the resonant frequency fb of mode b because the recess (5) is provided in the radiation conductor plate (2). Become. Note that the resonance frequency of mode b is the same as in the case of the disc-shaped radiation conductor plate (2) before the recess is provided, and here it is assumed that fb=f□.

FIG. 11 shows the input impedance characteristics of the circularly polarized microstrip antenna when it resonates at the above-mentioned resonant frequency fa and resonant frequency fb.

In the figure, the broken line shows the characteristics of mode a of the resonant frequency fa, and the solid line shows the characteristics of the mode b of the resonant frequency f1). At a frequency f such that p, fl) < f < fa, the phase of mode a advances and the phase of mode b lags. Here, the recess (
5) By appropriately designing the area of
The displacement from fb (= fo) can be adjusted, and the phases of the radiated electric fields of mode a and mode b at frequency fg, where the amplitudes of the radiated electric fields of mode a and mode b are equal, are adjusted to +45° and -45°, respectively. It can be done. That is, in FIG. 11, a frequency tl is obtained in which the real parts of mode a and mode b are equal and the imaginary parts of mode a and mode b are +7 and -7, respectively. In the microstrip antenna with the recess (5) designed in this way, the amplitudes of the radiated electric fields of mode a and mode b are equal, and there is a phase difference of 90° between the radiated electric fields of mode a and mode b. Therefore, in the circularly polarized microstrip antenna shown in Fig. 8, the straight line A-A'
makes an angle of 45° with straight line B, and when power is supplied at frequency fg from point F on the straight line passing through center 0, it emits circularly polarized waves.

[Problem to be solved by the invention]

In the circularly polarized microstrip antenna described above, in order to widen the input impedance band and improve radiation efficiency, the dielectric substrate (1) is made thicker,
When a dielectric substrate with a low dielectric constant is used, the frequency characteristics of the amplitude and phase of the radiated electric fields in mode a and mode b become small. That is, in the input impedance characteristic shown in FIG. 11 above, the peak of the real part curve becomes gentle, and the slope of the imaginary part curve becomes flat. Therefore, in order to set the frequency fo' for radiating the above-mentioned circularly polarized waves, the area of the recess (5) provided in the radiation conductor plate (2) should be made large, and the area of the recess (5) should be made large.
at the resonant frequency of. It is necessary to increase the displacement of fb (=fo). For this reason, the symmetry of the frequency characteristics of the amplitude and phase of the radiation '1 field of mode a and mode b is greatly shifted, and the frequency characteristics of the elliptical polarization are narrowband. There was a problem in that it was not possible to obtain

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain a microstrip antenna for circularly polarized waves having a broadband elliptically polarized wave ratio.

[Means to solve the problem]

The microstrip antenna according to the present invention has a recessed portion on the circumference of the portion where the circumference intersects the first straight line on the disk passing through the center of the nine disks.

A radiation conductor plate and a ground conductor plate each having a shape in which a convex portion is provided on the circumference of a portion where the circumference intersects with a second straight line on this disk that is orthogonal to the first straight line and passes through the center of the disk. a power feeding circuit which is insulated and opposed to each other and arranged substantially parallel, each forming a predetermined angle with respect to the first straight line and the second straight line, and having a feeding point on a straight line passing through the center of the disk; It has been established.

[Effect]

In this invention, by providing a concave portion and a convex portion in the radiation conductor plate, the concave portion and the convex portion are provided in the radiation conductor plate for the resonance frequencies fa+'l) of the two spatially orthogonal modes a and b. The resonant frequency fo before the
Equal displacement from and.

This reduces the symmetry deviation of the frequency characteristics of the amplitude and phase of the radiated electric fields of mode a and mode b.

〔Example〕

FIG. 1 is a diagram showing the configuration of a circularly polarized microstrip antenna according to an embodiment of the present invention), FIG. 1(a) is a front view, and FIG. 1(b) is an X- It is a cross-sectional view at X〆. In the figure, (1) to (5) are the same as in FIG. This is a convex portion provided on the circumference of the portion where the circumferences intersect.

Next, the operation will be explained.

The point in Figure 1(a)? When power is supplied from the radiating conductor plate (2), the operation can be considered in the same manner as the conventional example shown in FIG. 6, and the direction of the flow of # flowing on the radiation conductor plate (2) becomes K as shown in FIG. FIG. 2(a) is a diagram showing by arrows the direction of the main current flowing on the radiation conductor plate (2).

Figures (b) and (c) are diagrams in which arrows indicate the main current directions of mode a and mode b, which are spatially orthogonal. here,
If the resonant frequency before the recess (5) and the protrusion (6) are provided on the radiation conductor plate (2) is fo, then the resonant frequency fa of mode a is The resonant frequency fb of mode b is also lower than fo because the projection (6) is provided on the radiation conductor plate (2). Therefore, if the areas of the concave portion (5) and convex portion (6) of the radiation conductor plate (2) are designed appropriately, mode a and mode In the input impedance characteristic of b, the real parts of mode a and mode b at the frequency f which becomes fl) The microstrip antenna for circularly polarized waves shown in Figure 3 radiates circularly polarized waves when fed at the above frequency f.The input impedance characteristics in such a state are shown in Figure 3.In the above case.

Furthermore, by setting the areas of the concave part (5) and the convex part (6) of the radiation conductor plate (2) to be approximately equal, the resonant frequency fa
The displacements of and fb from fo can be made almost equal, and a highly symmetrical input impedance characteristic as shown in FIG. 4 can be realized. In addition, the radiation conductor plate (2
) is circular, resulting in good symmetry.

Therefore, in this circularly polarized wave microstrip antenna, when widening the input impedance band and improving radiation efficiency, the recess (5) of the radiation conductor plate (2)
By adjusting not only the area of the convex portion (6) but also the area of the convex portion (6), the degree of freedom is increased, and the f of the resonance frequencies fa and fb is adjusted.
Since the displacement from o can be made equal and small, and the deviation in the symmetry of the frequency characteristics of the amplitude and phase of the radiated electric fields of mode a and mode b can be reduced, it is possible to achieve a good elliptical polarization ratio over a wide frequency band. It has the effect of having

In the above embodiment, the power supply 1 is placed on the same surface of the dielectric substrate (1) as the radiation conductor plate (2).
Although a configuration is shown in which the power supply is performed from a microstrip line formed by providing a power supply, the structure for power supply is not limited to this, and the power supply from a triplate type strip line '1. It is also possible to have a structure in which power is fed by pin connection from a coaxial line or by slot coupling from a microstrip line, and a microstrip antenna for circularly polarized waves that emits circularly polarized waves can be realized in the same way as the operation explanation above. and has the same effect as above. Examples of the above structure will be described below with reference to the drawings. Note that each operation is redundant and will therefore be omitted.

FIG. 5 is a diagram showing the configuration of a circularly polarized microstrip antenna according to a second embodiment of the present invention.

Figure (a) is a front view, and figure (1)) is a sectional view taken along line XX'. In the figure, (2) and (4) to (6)
is the same as in Fig. 1, (Ia) is the first thin film substrate,
(1b) is the first foam dielectric substrate, (1c) is the second thin film substrate* (1d) is the second foam dielectric substrate* (”
) is the first ground conductor plate.

(3b) is the second ground conductor plate, (7) is the first ground conductor plate (
3a) is a radiation hole provided to take out radiated radio waves from the radiation conductor plate (2). Here, as shown in the same figure (b), the radiation conductor plate (2) is provided on one surface of the second thin film substrate (1C), and the power supply strip conductor (4) is also provided on the same surface. It is being Further, the first thin film substrate (1a) has a first thin film substrate (1a) provided with a radiation hole (7) on one surface.
A ground conductor plate (3a) is provided, and a first thin film substrate (1a) is provided.
) and the second thin film substrate (1C) are the first foam dielectric substrate (
1b), and are stacked as shown in FIG. 1(b). Furthermore, a second foamed dielectric substrate (1d) is
A second ground conductor plate (3b) is placed approximately parallel to the thin film substrate (1c).
is provided. In this example.

The feed strip conductor (4) is combined with the first and second ground conductor plates (3a) (3b) to form a triplate strip line. Therefore, the microstrip antenna can be configured in a planar manner, and there is an effect that unnecessary radiation from the power feeding strip conductor (4) can be suppressed, and loss and disturbance of the radiation pattern can be reduced. In addition, the power supply strip conductor and the first and second ground conductor plates (3a) (3b
) between the first and second foam dielectric substrates (1b) (1d)
Therefore, it is possible to form a low-loss triplate strip line.

Furthermore, since thin film substrates (1a) (1c) and foamed dielectric substrates (1b) (1a) are used as dielectric bodies,
It has the effect of being extremely inexpensive. Note that an air layer may be used instead of the foamed dielectric substrates (1b) and (1d).

FIG. 6 is a diagram showing the configuration of a circularly polarized microstrip antenna according to a third embodiment of the present invention.

Figure (a) is a front view, and figure (b) is a sectional view taken along line X-1'. In the figure, (1) to (3) and +51
, +61 are the same as in Figure 1, (8) is the coaxial line for power feeding, (9) is the inner conductor of the coaxial line for power feeding (8),
α1 is an outer conductor.

Here, the power feeding coaxial line (8) passes through the dielectric substrate (1) from the ground conductor plate (3) side, and the inner conductor (9) connects to the radiation conductor plate (2) at point F inside the radiation conductor plate (2). 2), and the outer conductor a is connected to the ground conductor plate (3). In addition, 2 points F
are the straight line A-A' and the straight line B-B' on the radiation conductor plate (2)
and 45 degrees, respectively, and are points on a straight line passing through the center 0. In this embodiment, since power can be fed from a point P inside the radiation conductor plate (2), impedance matching between the feed circuit and the microstrip antenna is facilitated.

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

Figure (a) is a front view, and figure (1)) is a sectional view taken along line X-X'. In the figure, (1) to (3) and (5
1 and +61 are the same as in Fig. 1, and αυ is the axis of symmetry of the straight line a-c' which makes an angle of 45° with the straight line Mu' and the straight line B-B' on the radiation conductor plate (2). slot provided on the ground conductor plate (3), Q3 is the slot provided on the ground conductor plate (3)
), αj is a strip conductor provided on the second dielectric substrate aa, α
Number 1 is a microstrip line formed by a strip conductor 0, a second dielectric substrate α, and a ground conductor plate (3).

Here, this microstrip line I has a slot 0υ
The radio wave fed from the microstrip line I excites the radiating element consisting of the radiating conductor plate (2) and the ground conductor plate (3) through the slot αυ to generate 1 circularly polarized wave. Let it radiate. In this example,
Since the IJ tube conductor α difference is shielded from the radiation conductor plate (2) by the ground conductor plate (3), there is an advantage that the influence of unnecessary radiation from the strip conductor 0 can be suppressed and a planar configuration can be achieved. Note that it is obvious that a structure using a triplate strip line may be used instead of the IJ tube line 04 (Micros).

〔Effect of the invention〕

As described above, according to the present invention, the radiation conductor plate of the microstrip antenna for circularly polarized waves is placed on the circumference of the part where the circumference intersects the first straight line on this disk passing through the center of the disk. A concave portion is provided, and a convex portion is provided on the circumference of a portion where the circumference intersects with a second straight line on this disk that is orthogonal to the first straight line and passes through the center of the disk. In particular, the input impedance characteristics of the two spatially orthogonal modes a and b corresponding to the direction along the first straight line and the direction along the second straight line can be made symmetrical.

Equal the displacement from the resonant frequency fO before providing the recesses and protrusions on the radiation conductor plate, which is necessary to obtain the one-day polarization of the resonant frequency 'aeft) of modes a and b.

In addition, there is an effect that it is possible to obtain a circularly polarized microstrip antenna that can be made small and has a wide band and a good elliptically polarized wave ratio.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a circularly polarized microstrip antenna showing an embodiment of the present invention, and Fig. 2 is an explanation showing the direction of the main resonant current flowing on the radiation conductor plate of the circularly polarized microstrip antenna. figure. Figures 3 and 4 are characteristic diagrams showing the frequency characteristics of the input impedance of a circularly polarized microstrip antenna;
FIG. 5 is a block diagram of a circularly polarized microstrip antenna showing a second embodiment of the present invention, and FIG. 6 is a block diagram of a circularly polarized microstrip antenna showing a third embodiment of the present invention. FIG. 7 is a configuration diagram of a microstrip antenna for circularly polarized waves showing a fourth embodiment of the present invention, FIG. 8 is a configuration diagram of a conventional microstrip antenna for circularly polarized waves, and FIG. 9 is a configuration diagram of a microstrip antenna for circularly polarized waves. Figure 10 is an explanatory diagram showing the direction of the main resonant current flowing on the radiation conductor plate of a circularly polarized microstrip antenna. Figure 11 is a circularly polarized microstrip antenna. FIG. 3 is a characteristic diagram showing the frequency characteristics of the input impedance. In the figure, (1) is a dielectric substrate 1 (Ia) is a first thin film substrate, (1b) is a first foamed dielectric substrate # (1
c) is the second thin film substrate I (Id) is the second foamed dielectric substrate, (2) is the radiation conductor plate, (3) is the ground conductor plate, (
3a) is the first ground conductor plate* (3b) is the second ground conductor plate, (4) is the power feeding strip conductor, and [5] is the recess provided in the radiation conductor plate (2). (6) is a convex portion provided on the radiation conductor plate (2), (7) is a radiation hole, (8) is a coaxial line for power feeding, (9) is an inner conductor,
α[ is an outer conductor, (Ill is a slot), H is a second dielectric substrate, 01 is a strip conductor, and α is a microstrip line. In each figure, the same reference numerals indicate the same or corresponding parts. Figure 1(a)

Claims (1)

[Claims] A recess is provided on the circumference of a portion where the circumference intersects a first straight line on the disc passing through the center of the disc, and a recess is provided on the circumference of the part where the circumference intersects with a first straight line on the disc passing through the center of the disc, and a radiation conductor plate having a shape in which a convex portion is provided on the circumference of a portion where the second straight line on the disk intersects with the circumference, and the radiation conductor plate is insulated from the radiation conductor plate, and
ground conductor plates arranged facing each other and substantially parallel, each forming a predetermined angle with respect to the first straight line and the second straight line;
A microstrip antenna including a feeding circuit having a feeding point on a straight line passing through the center of the disk.