JP2014090500A - Waveguide slot antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem of a conventional waveguide slot antenna radiating circularly polarized waves that complex calculation is required in design, and a circular polarized antenna obtained can ensure an excellent axial ratio only in a narrow band.SOLUTION: A waveguide slot antenna consists of a waveguide slot antenna having a waveguide as a feeder line and provided with a linear slot in the wall face of the waveguide, and a planar conductor plate provided with a first through hole of substantially same shape as the slot and a second through hole crossing the first through hole, in which the slot and the first through hole are arranged so as to overlap while facing each other thus radiating circularly polarized waves. A waveguide slot antenna radiating circularly polarized waves having excellent axial ratio characteristics over a wide band can be obtained by adding a simple structure to a conventional waveguide slot antenna.

Description

  The present invention relates to a waveguide slot antenna, and more particularly to a structure capable of generating circularly polarized waves.

In a base station of a wireless communication terminal or the like, a waveguide slot antenna using a waveguide as a feed line has been used as an antenna element useful in a microwave band and a millimeter wave band.
In addition, there are cases where circular polarization with less fading influence than linear polarization is desired for use in wireless communication terminals, and circular polarization antennas using various waveguide slot antennas have been proposed. Therefore, a waveguide slot antenna that radiates circularly polarized waves is desired.

Basically, an electromagnetic wave radiated from a linear slot becomes a linearly polarized wave.
Therefore, Non-Patent Documents 1 to 5 describe a method of converting a linearly polarized wave into a circularly polarized wave by combining a pair of linear slots so that polarized waves orthogonal to each other are generated. Patent Document 4 describes a method of converting a linearly polarized wave into a circularly polarized wave by coupling a parasitic element to a linear slot to generate orthogonal polarization components.

  FIG. 11 is a perspective view of a waveguide slot antenna that radiates circularly polarized waves described in Non-Patent Document 1. As shown in FIG. 11, a cross slot 59 composed of two straight slots 79, 79 moves from the center line CL of the tube axis of the cavity waveguide 89 on one wall surface of the cavity waveguide 89. , Provided.

US Pat. No. 6,028,562 JP 2003-37432 A JP 2000-34130 A Japanese Patent Application No. 2011-202765 Specification

A.J. Simmons, "Circularly polarized slot radiators," IRE Trans. Antennas Propag., Vol. 5, pp. 31-36, Jan. 1957. W.J. Getsinger, “Elliptically polarized leaky-wave array,” IRE Trans. Antennas Propag., Vol.10, pp.165-171, Mar. 1957. T. Hirano, J. Hirokawa and M. Ando, "A design of a leaky waveguide crossed-slot linear array with a matching element by the method of moments with numerical-eigenmode basis functions," IEICE Transactions on Communication, vol. E88- B, No. 3, pp. 1219-1226, Sep. 2004. G. Montisci, M. Musa and G. Mazzarella "Waveguide slot antennas for circularly polarized radiated field", IEEE Trans. Antennas Propag., Vol. 52, pp. 619-623, 2004. K. Min, J. Hirokawa, K. Sakurai, M. Ando, N. Goto and Y. Hara, "A Circularly Polarized Waveguide Narrow-wall Slot Array using a Single Layer Polarization Converter," IEEE AP-S International Symposium 1996, pp.1004-1007.

  The design of the conventional waveguide slot antenna that radiates circularly polarized waves described in Non-Patent Documents 1 to 5 and Patent Document 4 requires complicated calculations. A good axial ratio could be obtained only in a narrow band.

In order to solve the above-mentioned problem, a waveguide slot antenna according to claim 1,
A waveguide slot antenna having a waveguide as a feed line and a linear slot provided on the wall surface of the waveguide; a first through-hole having substantially the same shape as the slot; and the first through-hole intersecting And the waveguide slot antenna and the conductor plate are arranged such that the slot and the first through hole are stacked so as to face each other. It is characterized by radiating circularly polarized waves.

  By adding a simple structure to the conventional waveguide slot antenna, it is possible to obtain a waveguide slot antenna that radiates circularly polarized waves having good axial ratio characteristics over a wide band.

1 is a perspective view of a waveguide slot antenna according to a first embodiment of the present invention. FIG. 2 is an exploded perspective view of the waveguide slot antenna of FIG. 1. It is a figure explaining the dielectric waveguide of FIG. 1 in detail. It is a perspective view of the waveguide slot antenna which concerns on the 2nd Example of this invention. It is a perspective view of the waveguide slot antenna which concerns on the 3rd Example of this invention. It is a perspective view of the waveguide slot antenna which concerns on the 4th Example of this invention. It is a graph which shows the gain of the 1st example and the 4th example It is a disassembled perspective view at the time of applying a 4th Example to a dielectric waveguide. It is a graph which shows the return loss of the dielectric waveguide slot antenna of FIG. It is a graph which shows the axial ratio characteristic of the dielectric waveguide slot antenna of FIG. It is a perspective view of the conventional waveguide slot antenna.

Example 1
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a perspective view showing a first embodiment of the present invention, and FIG. 2 is an exploded perspective view of FIG.
As shown in FIGS. 1 and 2, the waveguide slot antenna 11 of the present invention includes:
On the opening surface of the waveguide member 81 made of a U-shaped conductor having an open side surface,
A plate-like slot plate 61 made of a conductor having a linear slot 71 is disposed,
A first through hole 31 having the same shape as the slot 71 at a position facing the slot 71;
A plate-shaped polarization conversion radiation plate 21 made of a conductor provided with a cross slot 51 formed by a linear second through hole 41 at a position intersecting the first through hole 31 is superimposed on the slot plate 61. Are arranged.

3 is a plan view for explaining in detail the polarization converting radiation plate 21 and the slot plate 61, FIG. 3 (a) is a plan view of the polarization converting radiation plate 21, and FIG. 3 (b) is a slot diagram. FIG. 6 is a plan view of a plate 61.
As shown in FIG. 3 (a), the polarization conversion radiation plate 21 has a length in the longitudinal direction of the first through-hole 31 of the L _1, intersecting the first through hole 31 and a predetermined crossing angle θ length in the longitudinal direction is provided and a second through-hole 41 of the L _2, as shown in FIG. 3 (b), the slot plate 61, the length of the longitudinal direction the slot 71 of the L ₁ provided that It has been.
The slot 71 and the first through hole 31 have substantially the same shape, and both the slot 71 and the first through hole 31 are rotated by θ _{0 with} respect to the direction perpendicular to the tube axis of the waveguide.
The length L ₂ in the longitudinal direction of the second through hole 41 is longer than the length L ₁ in the longitudinal direction of the first through hole 31.
An angle θ between the first through hole 31 and the second through hole 41 is −90 ° <θ <90 ° (where θ ≠ 0).
The thickness t of the polarization conversion radiation plate 61 is 0.2 to 0.3 times the wavelength length.

An electric field orthogonal to the electric field generated by the slot 71 is generated by the cross slot 51 where the first through hole 31 and the second through hole 41 intersect.
When this electric field and the electric field generated by the slot 71 are orthogonal to each other and the phase difference is 90 °, the combined wave becomes a circularly polarized wave.

The direction of rotation of the circularly polarized wave is determined by the crossing angle θ.
When the second slot 41 is arranged to rotate counterclockwise (θ> 0) with respect to the first slot 31, it becomes a left-handed circularly polarized wave, and the second slot is arranged to rotate right (θ <0). Then, it becomes a right-handed circularly polarized antenna.

The crossing angle θ is selected so that the axial ratio characteristic is good, for example, in a range of 30 ° ≦ θ <90 °.
The angle θ ₀ with respect to the direction perpendicular to the waveguide axis of the slot 71 is arbitrary, and can be arranged at any angle so as to facilitate impedance matching.

(Example 2)
The circularly polarized waveguide slot antenna shown in FIG. 1 has a significant increase in weight as compared to a linearly polarized waveguide slot antenna because the polarization conversion radiation plate is thick.
As a result of the experiment, the waveguide slot antenna is spread over a wide band that radiates circularly polarized waves, even if it has a structure in which only the vicinity of the periphery of the slot is left for weight reduction and most of the polarization conversion radiation plate is removed. It was found that the antenna can be operated as a good axial ratio characteristic.

  FIG. 4 is a diagram for explaining a second embodiment of the waveguide slot antenna of the present invention, and FIG. 4 (a) explains the second embodiment for the first waveguide slot. FIG. 4B is a perspective view of a second embodiment of the waveguide slot antenna of the present invention.

As shown in FIG. 4A, when the polarization converting radiation plate of the waveguide slot antenna of FIG. 1 is cut out leaving a range surrounded by a dotted line in the figure, the present invention shown in FIG. A waveguide slot antenna 12 is obtained.
As shown in FIG. 4B, the waveguide slot antenna 12 of the present invention is formed on the opening surface of a waveguide member 82 made of a U-shaped conductor having an open side surface.
Arranged on a plate-like slot plate 62 made of a conductor having a linear slot 72 inside the opening surface of the waveguide member 82,
A pair of polarization conversion structures 22, 22 is provided that surrounds the outer periphery of the slot 72 and is divided into two by a linear cut 42 that intersects the slot 72. The polarization conversion structures 22 and 22 are arranged point-symmetrically with respect to the center point of the slot 72.
The height of the polarization conversion structure 22 is h, and the polarization conversion structure 22 is preferably arranged at a distance within half a wavelength from the center of the slot 72.

  In the waveguide slot antenna 12, the combination of the first slot 72 and the cuts 42 and 42 can be regarded as a pseudo cross slot, so that the circularly polarized wave can be radiated as in the first embodiment. it can.

(Examples 3 to 4)
FIG. 5 is a perspective view showing a third embodiment of the waveguide slot antenna of the present invention. As shown in FIG. 5, the notch 43 may not be on a straight line. The cuts 43 may extend radially from the center of the first through hole in order to perform impedance matching. Return loss can be reduced by changing the shape of the cut.

  FIG. 6 is a perspective view showing a fourth embodiment of the waveguide slot antenna of the present invention. As shown in FIG. 6, the corners of the polarization conversion structures 24, 24 may be chamfered in order to perform impedance matching. By chamfering the corners of the polarization conversion structure, the return loss can be reduced.

FIG. 7 is a graph showing a comparison between the results obtained by calculating the gains of the waveguide slot antenna of the first embodiment and the waveguide slot antenna of the fourth embodiment using an electromagnetic field simulator.
In FIG. 7, the vertical axis represents gain [dBi], the horizontal axis represents frequency [GHz], the dotted line represents the waveguide slot antenna of the first embodiment, and the solid line represents the waveguide slot of the fourth embodiment. Indicates an antenna.
Both the waveguide slot antenna of the first embodiment and the waveguide slot antenna of the fourth embodiment are configured as single-element antennas in the 60 GHz band.

From FIG. 7, when the frequency is 60 GHz, the gain of the waveguide slot antenna of the first example is 6.1 dBi, whereas that of the waveguide slot antenna of the fourth example is 9.4 dBi. Gain was obtained.
Therefore, it can be seen that the structure of the waveguide slot antenna shown in the fourth embodiment has an effect of not only reducing the weight of the antenna but also significantly improving the gain.

The waveguide slot antenna of the present invention can be applied not only to a hollow waveguide but also to a dielectric waveguide. FIG. 8 is a perspective view showing a fifth embodiment of the waveguide slot antenna of the present invention.
As shown in FIG. 8, the waveguide slot antenna 15 is
A dielectric waveguide 85 in which the surface of a rectangular parallelepiped dielectric is covered with a conductor film and a linear dielectric exposed portion 95 is provided on a part of the upper surface to expose the dielectric.
It is arranged in a plate-like slot plate 65 having a linear slot 75 having substantially the same shape as the dielectric exposed portion 95 at a position facing the dielectric exposed portion 95,
A first through hole 35 having the same shape as the slot 75 at a position facing the slot 75;
A pair of polarization conversion structures 25, 25 that surround the outer periphery of the first through hole 75 and are divided into two by a notch 45 that intersects the slot 75 are provided.

FIG. 9 shows the result of calculating the return loss characteristic of the waveguide slot antenna of Example 5 using an electromagnetic field simulator. In the figure, the vertical axis represents return loss [dB], and the horizontal axis represents frequency [GHz].
From FIG. 9, it can be seen that the specific bandwidth at which the return loss is 20 dB or more is about 18% at 55 GHz to 70 GHz.

FIG. 10 shows the result of calculating the axial ratio characteristic of the waveguide slot antenna of the fifth embodiment by an electromagnetic field simulator. In the figure, the vertical axis represents the axial ratio [dB], and the horizontal axis represents the frequency [GHz].
From FIG. 10, it can be seen that the specific bandwidth at which the axial ratio characteristic is 2 dB or less is about 17% at 55 GHz to 70 GHz.

  From the results of FIGS. 9 and 10, it can be seen that in the range where the return loss is 20 dB or less, the axial ratio is 2 dB or less, and an extremely wide band characteristic is obtained.

  From the above-described embodiment, the waveguide slot antenna in which a straight slot is provided on the tube wall of the waveguide is further provided with a cross slot in which the first through hole and the second through hole are provided. By adding a wave conversion radiation plate or simply providing a pair of polarization conversion structures on the outer periphery of the slot of a waveguide slot antenna in which a straight slot is provided on the tube wall of the waveguide, It can be a waveguide slot antenna that radiates waves.

  The waveguide slot antenna of the present invention is applicable not only to a single antenna but also to an array antenna.

11, 12, 13, 14, 15, 19 Waveguide slot antenna 21 Polarization conversion radiation plates 22, 23, 24, 25 Polarization conversion structures 31, 41, 71, 75 Through holes 42, 43, 44, 45 Notches 51, 59 Cross slots 61, 62, 63, 64, 65 Slot plates 71, 75, 79 Slots 81, 82, 83, 84, 89 Cavity waveguide 85 Dielectric waveguide 95 Dielectric exposed portion

Claims (5)

A waveguide slot antenna having a waveguide as a feed line and a linear slot provided on the wall surface of the waveguide;
A plate-like conductor plate provided with a first through hole having substantially the same shape as the slot and a second through hole intersecting the first through hole;
The waveguide slot antenna and the conductor plate are:
A waveguide slot antenna, wherein the slot and the first through hole are arranged to face each other and radiate circularly polarized waves. The thickness of the conductor plate is
2. The waveguide slot antenna according to claim 1, wherein the waveguide slot antenna has a wavelength length of 0.2 to 0.3 times. 3. The waveguide slot antenna according to claim 1, wherein a length of the second through hole in a longitudinal direction is longer than a length of the first through hole in a longitudinal direction. 4. . 4. The waveguide slot antenna according to claim 1, wherein the waveguide is a cavity waveguide or a dielectric waveguide. An array antenna using the waveguide slot antenna according to any one of claims 1 to 7.

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