JPH10209743A - Slot-coupling type microstrip antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate mutual coupling and to obtain good circular polarization axis ratio characteristics and two-frequency sharing characteristics by arranging two coupling slots and a radiation conductor in a prescribed shape at specific positions of a radiation conductor respectively. SOLUTION: Coupling rectangular slots 14a and 15a are formed at mutually symmetrical positions which are parallel to the sides of a rectangular radiation conductor 11 about the intersection of the diagonals of the rectangular radiation conductor 11 as an axis, so that their length directions cross each other at right angles. At this time, the centers of the slots 14a and 15a and the center of the radiation conductor 11 are on a straight line along the length of the slot 15a. Further, feeding microstrip conductors 16a and 17a pass the centers at right angles to the length directions of the slots 14a and 15a, and the tip of the conductor 16a is bent in parallel with the conductor 17a. When a circular polarized wave is radiated by feeding microwaves which are 90 deg. out of phase with each other from feed terminals T1 and T2 and then exciting the radiation conductor 11, the directions of respective frequency currents do not become parallel to each other, so that the coefficient of mutual coupling between T1 and T2 becomes small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slot-coupled microstrip antenna used as, for example, an array antenna mounted on a satellite.

[0002]

2. Description of the Related Art As a conventional antenna of this type, a dual-frequency linearly polarized microstrip antenna (hereinafter referred to as a first conventional example) shown in FIG. 5 is known. (A)
Shows a plane, and (b) shows a vertical section taken along line CC ′ shown in (a). In the figure, 51 is a radiation conductor, 52, 58
Is a dielectric substrate, 53 is a ground conductor plate, 54b and 55b are coupling slots, 56b and 57b are power supply microstrip conductors, and T1 and T2 are power supply terminals. In the antenna shown in FIG. 5 as a conventional example, two rectangular slots 54b and 55b located immediately below the rectangular radiation conductor 51 are provided at positions orthogonal to each other with a diagonal intersection of the rectangular radiation conductor 1 as a center.

By making the rectangular slots 54b and 55b in the first conventional example have the same shape, the resonance frequencies when viewed from the antenna side from the two power supply terminals T1 and T2 are matched, and both power supply terminals T1 and T2 are used. , T2, the excitation phase difference of each microwave signal is set to 90 degrees. As a result, it is possible to excite the radiated radio waves so as to be circularly polarized waves.

On the other hand, a microstrip antenna shown in FIG. 7 (hereinafter referred to as a second conventional example) is also known as a circularly polarized microstrip antenna or a dual-frequency linearly polarized microstrip antenna. (A)
Is a plane, and (b) is a longitudinal sectional view taken along line DD ′.

In these conventional microstrip antennas, the two feeding microstrip conductors 6b, 7
b or 6c, 7c and two coupling rectangular slots 54b, 5 provided for coupling the rectangular radiation conductor 51.
In the first conventional example shown in FIG. 6, 5b or 54c and 55c are rectangular radiation conductors 51 each having a longitudinal direction.
Are formed so as to be parallel to one side of the radiating conductor 51 from the center of the radiating conductor 51. On the other hand, in the second conventional example shown in FIG. Is formed.

In the conventional example described above, two power supply terminals T
1, T2, these feed terminals T1, T2
The amount of mutual coupling between the two, that is, isolation, becomes a problem. If the amount of this coupling is large, the following problem occurs.

First, when two microwave signals having a phase difference of 90 degrees from each other are excited to emit a circularly polarized radio wave, these power supply terminals T1, T
There is a problem that the axial ratio characteristic of the circularly polarized wave of the radiated radio wave is deteriorated due to mutual coupling between the two. Second, each power supply terminal T
When the above-mentioned microstrip antenna is operated as a dual-frequency antenna by making the respective resonance frequencies measured at T1 and T2 inconsistent with the transmission frequency and the reception frequency, respectively, the large power on the transmission side causes mutual coupling. May leak to the receiving circuit side, causing the receiving circuit to malfunction or, in the worst case, to damage the receiving circuit. Therefore,
It is desirable to reduce the coupling as much as possible. The greatest factor of this mutual coupling is the TM11 mode caused by the fact that the coupling rectangular slot is offset from the center of the radiation conductor and excited, as described later.

FIG. 6 is a diagram showing the flow of a high-frequency current in the TM11 mode when a microwave signal is input and excited via the feed terminal T1 or T2 in the first conventional microstrip antenna. As is clear from the figure, the longitudinal directions of the coupling rectangular slots 54b and 55b are respectively set so that the longitudinal direction of the rectangular
In the configuration formed so as to be parallel to one side, the high-frequency current flowing directly above both of the coupling slots 54b and 55b is orthogonal to the longitudinal direction of each of the slots 54b and 55b. It can be seen that coupling occurs between the slots 54b, 55b and the mode current. Therefore, FIG.
In the configuration shown in the first conventional example shown in FIG. 1, it can be seen that mutual coupling occurs between the two power supply terminals T1 and T2 via the TM11 mode.

FIG. 8 is a diagram showing the flow of a high-frequency current when a microwave signal is input through a feed terminal T1 or T2 and vibrated in the second conventional microstrip antenna. As can be seen from the figure, the longitudinal direction of the coupling rectangular slots 54c and 55c is parallel to one side of each rectangular radiation conductor 51, and the coupling slot position is offset in the short direction from the center of the radiation conductor 51. In the configuration, since the high-frequency current flowing directly above both the slots 54c and 55c is parallel to the slots 54c and 55c, the coupling slots 54c and 55c
No coupling occurs between the current and the mode current. However, in the second conventional example shown in FIG. 7, when the amount of offset in the slot short direction from the center of the rectangular radiation conductor 51 is large and the dielectric constant of the antenna substrate is low, the size of the slot becomes large. However, there is a problem that the coupling of

[0010]

As described above, according to the conventional microstrip antenna, the mutual coupling between the two feeding terminals is relatively large, and as a result, the circularly polarized light radiated when the circularly polarized wave is excited. There is a problem in that the axial ratio characteristics of the waves are deteriorated, and when two frequencies are shared, the reception characteristics are deteriorated due to leakage of power from the transmission side to the reception side.

The present invention has been made in view of the above circumstances, and there is no mutual coupling between two power supply terminals, so that better axial ratio characteristics of circularly polarized waves or better two-frequency sharing can be obtained as compared with the conventional example. An object of the present invention is to provide a slot-coupled microstrip antenna having characteristics.

[0012]

According to the present invention, there is provided a slot-coupled microstrip antenna, comprising: a first dielectric substrate on which a radiating conductor having a rectangular or square shape is formed;
And a second dielectric substrate on which the second power supply line is formed. The microwave signal input to each power supply line via the first and second coupling slots provided between the first and second coupling slots. The first and second radiating conductors are excited.
The coupling slots are formed at positions facing each other with the intersection of diagonal lines of the radiation conductor as an axis,
A longitudinal direction of the first coupling slot is parallel to one side of the radiation conductor, and a longitudinal direction of the second coupling slot is parallel to the other side of the radiation conductor; The longitudinal direction of the connecting slot and the longitudinal direction of the second coupling slot are formed so as to be orthogonal to each other. In addition, each of the power supply lines passes directly below a longitudinal center of each of the coupling slots, and
The longitudinal direction of each power supply line is formed so as to be orthogonal to the longitudinal direction of each coupling slot, and the tip of one power supply line is bent at a right angle so as to be parallel to the longitudinal direction of the other power supply line. It is also characterized by being formed.

Further, a rectangular radiation conductor is formed on the first dielectric substrate, and the first dielectric substrate is provided between the second dielectric substrate on which the feeder line is formed and the first dielectric substrate. A ground conductor in which first and second coupling slots are formed such that the longitudinal direction of the slot is parallel to one side of the rectangular radiating conductor and the longitudinal direction of the second slot is parallel to one side of the rectangular radiating conductor A plate is sandwiched between the first slot, the rectangular radiating conductor, and the second slot. The centers of the respective slots are arranged on a straight line parallel to the longitudinal direction of the second rectangular slot.

As a result, there is no mutual coupling between the two feeding terminals, and a slot-coupled microstrip antenna having better circular polarization axial ratio characteristics or better dual-frequency sharing characteristics than the prior art is provided. it can.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention.
A linearly polarized microstrip antenna is illustrated. (A) is a figure which shows a plane, (b) is a figure which shows the vertical cross section of the AA 'line. Linearly polarized microstrip antenna
The dielectric substrate 12 is sandwiched between the rectangular radiation conductor 11 and the ground conductor plate 13, and the coupling rectangular slots 14 and 15 are provided on the ground conductor plate 13. This coupling rectangular slot 14,
15 are formed at positions symmetrical to each other about an intersection of diagonal lines of the rectangular radiation conductor 11 and
4, the longitudinal direction is parallel to one side of the rectangular radiation conductor 11,
The longitudinal direction of the slot 15 is parallel to one of the rectangular radiation conductors 11, and the longitudinal direction of the slot 14 and the
Are formed so that their longitudinal directions are orthogonal to each other.

As shown in the figure, a rectangular radiating conductor 11 is formed at a central position on the surface of a dielectric substrate 12, and a slot is provided between the back surface of the dielectric substrate 12 and the surface of the dielectric substrate 18. A ground conductor plate 13 in which a coupling slot 15 is formed so that the longitudinal direction of 14 is formed on one side of the rectangular radiation conductor 11 and the longitudinal direction of the slot 15 is parallel to one side of the rectangular radiation conductor 11. You. Here, the rectangular slots 14 and 15 are provided at point symmetrical angles, which are 180 degrees from each other, about the diagonal intersection of the rectangular radiation conductor 11, and the longitudinal direction of the rectangular slot 15 is It is formed so as to be orthogonal to the longitudinal direction. Thus, the center of the rectangular slot 14, the center of the rectangular radiating conductor 11, and the center of the rectangular slot 15 are on a straight line parallel to the longitudinal direction of the rectangular slot 15.

Further, on the back surface of the dielectric substrate 18, the power supply microstrip conductor 16 passes just below the central portion in the longitudinal direction of the slot 14, and the longitudinal direction of the conductor 16 is orthogonal to the longitudinal direction. In addition, the power supply microstrip conductor 17 is formed so as to pass right below a central portion of the slot 15 in the longitudinal direction, and the longitudinal direction of the conductor 17 is orthogonal to the longitudinal direction. Further, the tip of one power supply microstrip conductor 6a is bent at a right angle so as to be parallel to the longitudinal direction of the other power supply microstrip conductor 7a. Here, the microstrip conductor 16 and the ground conductor plate 13 form a first power supply microstrip line, while the microstrip conductor 17 and the ground conductor 13 form a second power supply microstrip line. Feed terminals T1 and T2 are provided at the respective edge portions of the dielectric substrate 18 of the microstrip conductors 16 and 17, respectively.

The materials of the dielectric substrates 12 and 18 are as follows:
Air, a foam material, and a honeycomb material are used, but these may be used in combination.

In the configuration described above, the first and second power supply microstrip lines 16a and 17a are electromagnetically coupled to the radiation conductor 11 via coupling rectangular slots 14a and 15a, respectively. Also, a linear knitted wave electromagnetic wave excited when a microwave signal is input to the first microstrip line via the first power supply terminal T1, and a second microstrip via the second power supply terminal T2. Coupling rectangular slots 14 and 15 are formed so that electromagnetic waves of linear braided waves excited when a microwave signal is input to the line are orthogonal to each other.

The impedance matching between each feeding microstrip line and the antenna is based on the arrangement of the coupling rectangular slots 14 and 15, the length in the longitudinal direction, and the coupling micro slots 14 and 15. It is obtained by adjusting the length of each matching stub formed by the lines up to the respective open ends which are the feed terminals T1 and T2 of the strip line. In the microstrip antenna, the impedance when viewed from the power supply terminal T1 on the antenna side is set to match the impedance when viewed from the power supply terminal T2 on the antenna side.

Now, each microwave signal having the same frequency and having a phase difference of 90 degrees is fed to the antenna via feed terminals T1 and T2, so that each of the microwave signals has a rectangular shape. The rectangular radiating conductor 11 is excited through the slots 14 and 15, whereby the direction perpendicular to the rectangular radiating conductor 11 from the microstrip antenna is applied to the ground conductor plate 1.
Circularly polarized electromagnetic waves are radiated toward free space in the direction from 3 to the rectangular radiation conductor 11. Here, the power supply terminal T1
The phase of the microwave signal fed through the feed terminal T2 is advanced by 90 degrees compared to the phase of the fed microwave signal fed through the feed terminal T2, thereby radiating a left-handed circularly polarized electromagnetic wave. be able to. Also, by delaying by 90 degrees, a right-handed circularly polarized electromagnetic wave can be emitted.

The applicant prototyped the microstrip antenna and obtained a reflection coefficient S at each of the feed terminals T1 and T2.
11, S22 and each frequency characteristic of the mutual coupling coefficient S12 were measured. The parameters of the prototype microstrip antenna are as listed below.

(A) The relative permittivity of the dielectric substrate 12: 2.60, its thickness: 3.2 mm (b) The relative permittivity of the dielectric substrate 18: 2.60, its thickness: 3.2 mm ( c) One side of the rectangular radiation conductor 11: 60.0 mm (d) Rectangular slot 14 for coupling: 25.0 mm length * 1.0 mm width (e) Rectangular slot 14 for coupling: 20.0 mm length * 1.0 mm width (f ) Distance between the center of the rectangular slot 14 and the center of the radiation conductor 11: 25.0 mm (g) Distance between the center of the rectangular slot 15 and the center of the radiation conductor 11: 20.0 mm (h) First and second microstrip lines FIG. 2 is a graph showing frequency characteristics of reflection coefficients S11 and S22 of the microstrip antenna shown in FIG.
As is clear from FIG. 2, the resonance frequency of the antenna measured at both the power supply terminals T1 and T2 is about 1.50 GHZ, and it can be seen that they match each other.

FIG. 3 is a graph showing the frequency characteristic of the mutual coupling coefficient S12 of the microstrip antenna shown in FIG. In the case of the conventional example, the mutual coupling coefficient S12 is -20 dB.
In contrast, in the case of the embodiment of the present invention, FIG.
As is clear from FIG. 5, the mutual coupling coefficient S12 indicating leakage from one power supply terminal T1 to the other power supply terminal T2 is −
It turns out that it is suppressed to 30 dB or less. The reason why the mutual coupling coefficient is reduced in the embodiment of the present invention will be described below.

FIG. 4 is a diagram showing the flow of a high-frequency current in the TM11 mode when a microwave signal is input and excited via the feed terminal T2 in the microstrip antenna of the present invention. As is clear from the figure, the direction of the high-frequency current depends on the rectangular slot 15 used for excitation.
Of the rectangular slot 14
Are parallel to the longitudinal direction.

Therefore, unlike the conventional example, the directions of the respective frequency currents in the TM11 mode are not parallel to each other when the excitation is performed via the power supply terminal T1 and when the excitation is performed via the power supply terminal T2. The mutual coupling coefficient between T1 and T2 can be reduced as compared with the related art. As a result, in the present invention, the power sneak from the transmitting side to the receiving side in the dual-strip linearly polarized microstrip antenna can be significantly suppressed. Therefore, for example, it is possible to reduce the load capability of unnecessary band suppression in the band-pass characteristics of the band-pass filter in the duplexer connected to the power supply line of the ACATENA, so that the band-pass filter can be reduced in size and weight. Thereby, the whole antenna device including the duplexer can be reduced in size and weight.

In the embodiment of the present invention, a microstrip line is used as a power supply line. However, the present invention is not limited to this, and a triplate line, a coplanar line, or a slot line may be used. Also,
Although a square radiation conductor was used, there is no problem as long as the radiation conductor has a rectangular shape such as a rectangle. Furthermore, although a rectangular slot is used as a power supply slot, the present invention is not limited to this, and a rectangular slot called a “dog horn type” in which both ends of a rectangular slot, an elliptical slot, and a rectangular slot are vertically extended may be used.

As described above, according to the present invention, the first dielectric substrate on which the radiation conductor having a rectangular or square shape is formed, and the second dielectric substrate on which the first and second power supply lines are formed. The radiation conductor is excited by a microwave signal input to each feed line via first and second coupling slots interposed between the substrate and the first and second coupling slots. The coupling slots are formed at positions facing each other around an intersection of diagonal lines of the radiation conductor, and the longitudinal direction of the first coupling slot is parallel to one side of the radiation conductor, and The longitudinal direction of the second coupling slot is formed so that the longitudinal direction of the second coupling slot is parallel to the other side of the radiation conductor, and the longitudinal direction of the first coupling slot is orthogonal to the longitudinal direction of the second coupling slot. Also characterized by , And the like in the conventional example Thus, the case of excitation through a first feeding line second
Since the directions of the high-frequency currents in the TM11 mode are not parallel to each other when excited through the feed line of
The mutual coupling coefficient between the antennas connected to one feeding line can be made extremely small as compared with the conventional example.

[0030]

As described above, according to the present invention, when the microstrip antenna is used as a circularly polarized microstrip antenna, deterioration of the axial ratio of circularly polarized waves can be prevented. On the other hand, the microstrip antenna is
When used as a frequency-shared linearly polarized microstrip antenna, it is possible to greatly suppress the sneak from the transmission side to the reception side. For example, the band width of a band-pass filter in a duplexer connected to a feed line of the antenna It is possible to reduce the load capability of unnecessary wave suppression in the pass characteristic, and to reduce the size and weight of the band-pass filter. Thus, there is an advantage that the entire antenna device including the duplexer can be reduced in size and weight.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of the present invention, in which (a) shows a plane and (b) shows an AA ′ section.

FIG. 2 is a graph showing frequency characteristics of reflection coefficients S11 and S22 of the microstrip antenna of FIG.

FIG. 3 is a graph showing a frequency characteristic of a mutual coupling coefficient S12 of the microstrip antenna of FIG. 1;

FIG. 4 shows the microstrip antenna of FIG.
The figure which shows the flow of the high frequency electric current of TM11 mode at the time of inputting and exciting a microwave signal via the power supply terminal T2.

FIGS. 5A and 5B are diagrams showing a first conventional microstrip antenna, in which FIG. 5A is a plan view and FIG. 5B is a cross-sectional view taken along the line CC ′.

FIG. 6 shows the microstrip antenna of FIG.
The figure which shows the flow of the high frequency electric current of TM11 mode at the time of inputting and exciting a microwave signal via feed terminal T1 or T2.

7A and 7B are diagrams showing a second conventional microstrip antenna, wherein FIG. 7A is a plan view and FIG. 7B is a cross-sectional view taken along the line DD ′.

FIG. 8 shows the microstrip antenna of FIG.
The figure which shows the flow of the high frequency current of TM11 mode at the time of inputting and exciting a microwave signal via feed terminals T1 (a) and T2 (b).

[Explanation of symbols]

11 ... rectangular radiation conductor, 12, 18 ... dielectric substrate, 13 ...
Ground conductor plate, 14a, 15a ... rectangular slot, 16a,
17a: power supply microstrip conductor, T1, T2 ...
Power supply terminal.

Claims (3)

[Claims] 1. A first dielectric substrate on which a radiating conductor having a rectangular or square shape is formed, and a second dielectric substrate on which first and second feeding lines are formed. The radiation conductors are excited by microwave signals input to the respective feeder lines via the first and second coupling slots, wherein the first and second coupling slots are The radiating conductors are formed at positions facing each other around an intersection of diagonal lines, and the longitudinal direction of the first coupling slot is parallel to one side of the radiating conductor, and the second coupling slot is A slot whose longitudinal direction is parallel to the other side of the radiating conductor, and wherein the longitudinal direction of the first coupling slot and the longitudinal direction of the second coupling slot are orthogonal to each other; Combined microstory Antenna. 2. The power supply line passes immediately below a central portion of each of the coupling slots in the longitudinal direction, and
The longitudinal direction of each power supply line is formed so as to be orthogonal to the longitudinal direction of each coupling slot, and the tip of one power supply line is bent at a right angle so as to be parallel to the longitudinal direction of the other power supply line. The slot-coupled microstrip antenna according to claim 1, wherein the antenna is formed. 3. A first radiating conductor is formed on a first dielectric substrate, and a first dielectric substrate is provided between the second dielectric substrate on which a feed line is formed and the first dielectric substrate. The longitudinal direction of the slot is formed parallel to one side of the rectangular radiation conductor,
A ground conductor plate on which first and second coupling slots are formed is sandwiched so that the longitudinal direction of the second slot is parallel to one side of the rectangular radiating conductor. A slot-coupled microstrip antenna, wherein the center of each of the two slots is arranged and formed on a straight line parallel to the longitudinal direction of the second rectangular slot.