JPH0449705A - Waveguide slot antenna - Google Patents

Abstract

PURPOSE:To improve omni directivity by improving perpendicular plane directivity by stacking two waveguide slot antennas in a perpendicular direction. CONSTITUTION:A waveguide slot antenna unit 1 and a waveguide slot antenna unit 2 are stacked by arranging their slot planes 11 and 12 in the same direction, and a feed probe with 3/4-wave is provided by piercing through the antenna units 1 and 2. Since the feed probe 3 is of 3/4-wave, current distribution on the feed probe 3 goes to the one nearly as shown in dotted line, and an excitation phase in each antenna unit shows a negative phase as shown in arrow head. The phases of electromagnetic waves radiated from all the slots can easily be arranged equally by setting the inclining directions of slots (for example, slots 12a and 22a, or slots 11n and 22n) located at the same distance from the feed probe 3 reversely.

Description

[Detailed Description of the Invention] [Industrial Application Field] The waveguide slot antenna of the present invention is suitable for antennas used in marine radars in 1% and 5HF (very high frequency)
This is a book that is expected to have expanded use in the future as it is used for wireless communications in the band.

[Conventional technology]

Waveguide slot antennas have traditionally been used as rotating antennas in some marine radar equipment, but they are rarely seen by the general public, and many are not even listed in antenna-related manuals, making them little-known. Since this is an antenna in a format that is not
Institute of Electronics and Communication Engineers line.

This is an excerpt from the book (Published by Ohmsha, first edition, October 30, 1980).

Reprinted from page 223 of the Antenna Engineering Handbook [Fig.
2 (omitted) is a waveguide slot antenna which is an example of the simplest configuration of a series feeding circuit.

The power coupling portion from the waveguide, which is the main line, forms the element antenna as it is, and the degree of coupling is determined by the inclination angle of the slot. Note that the spacing between the slots is set to % of the wavelength in the waveguide, and the conditions for co-phase excitation are satisfied by reversing the inclination direction to each element. ” Antenna Engineering Handbook, page 249” - reprinted [7.6
・3 Navigation Radar Antenna [1] Ship-mounted Radar Antenna (b) Slot-type radar antenna (above omitted) Currently, slot antennas with small apertures are used for navigation radar. The slot antenna is a PT (slot) on the waveguide wall as shown in the figure (omitted).
2, and the radio waves emitted from the slot are arrayed.
It has the advantages of being light in weight, having little wind resistance, and making it easy to arbitrarily select the current distribution on the antenna. The current distribution and I2 to be used are either the Tievisiev distribution that minimizes both the beam width and sidelobe level for a given antenna length, or the beamwidth is slightly wider, but the sidelobes are low and high gain and seven turns can be obtained. Tiller distribution is used. The slot length is slightly shorter or longer than λj/2 as a non-resonant slot to provide broadband properties. The direction of the ninth beam deviates slightly from the broadside direction.

(The following is omitted)" The citation is omitted in the above text, and the drawing is almost the same as Figure 4 of this specification. As is clear from this figure, the main body of the waveguide slot antenna is a rectangular waveguide element, and it has a structure with slots) a-n on one side wall of the element, so it is different from other SHF band O7 Compared to antennas, they have the advantage of having greater mechanical strength and occupying a smaller volume.

[Problem to be solved by the invention]

Guide 9! In a slot antenna, each slot acts as a radiating element, so it can be thought of as an array antenna with as many elements as r3 slots lined up toward the center of the waveguide. By increasing the number of planes that include the center line of the waveguide and are perpendicular to the slot plane (
The radiation directivity in the plane (hereinafter referred to as the horizontal radiation plane for convenience) becomes sharper and the center gain also increases, but the radiation directivity in the plane perpendicular to both the slot plane and the horizontal radiation plane (hereinafter referred to as the vertical radiation plane for convenience) increases. The radiation directivity of B can only be expected to be comparable to that of a single dipole element.

It is good as a ship radar antenna whose purpose is to display the position of an object on the water surface by rotating the antenna along the Y surface of the water and measuring the intensity and reflection time of reflected radio waves in the horizontal direction. For general wireless communication applications, it is desirable to have good omnidirectional directivity like other SHF band antennas such as parallax antennas and horn antennas2).

Since the waveguide slot antenna has satisfactory directivity in the water plane, improving the directivity in the vertical plane will improve the directivity in all directions.

Further, improvement in vertical directivity is desirable for ship radar applications because it can reduce water surface reflections and aircraft reflections.

(Means for solving the !Itj order) In order to improve the vertical directivity of the waveguide slot antenna, two waveguide slot antennas are vertically stacked in the present invention.

In many directional antennas, it is well known that the directional J gain in the stacking direction is improved by stacking antenna units, and this is also put into practice. However, the reason why there are no examples of stack use in waveguide slot antennas is a guess because there is no documentation, but the conventional use was limited to ship radar, so there was no problem with the intended use. In addition, in a stack antenna, it is necessary to feed power so that each antenna unit is excited in the same phase, but it is possible to connect the feeding waveguide to one end of the antenna unit shown in Figure 4, which is the basic form of a waveguide slot antenna. In this structure, the method of feeding power to each unit from the main waveguide through the bifurcated waveguide goes against the simplicity of the antenna unit, and is completely inappropriate for use as a rotating antenna for radar.

In addition, as shown in Figure 5, as a rotary antenna for radar, a structure in which a feeding globe is installed through the center of rotation f1 (1) of the antenna unit is often used, but in the case of a stacked antenna, a feeding globe of two units each is used. This is also due to the development of a power supply system in which the globe is the central axis of rotation and is excited in the same phase.

In order to solve the above-mentioned problems, in the present invention, as shown in a partial cross-sectional diagram in FIG. A three-quarter wavelength feeding probe is provided by stacking them in alignment in the same direction and penetrating the antenna units 1 and 2.

FIG. 2 is a longitudinal cross-sectional view for explaining the mechanical relationship and operation of the stacked antenna unit 2 and power feeding globe 3.

Antenna units 1 and 2 are stacked so that the center distance is approximately 1/2 wavelength, so depending on the dimensions of the rectangular waveguide that makes up the unit, both units may be in close contact or may be spaced apart. .

The excitation of this antenna system passes through each antenna unit.
Since this is carried out using a three-quarter wavelength power supply globe 3 provided at the same location, necessary holes are provided in the waveguide wall passing through the globe. Furthermore, if there is a gap between the antenna units 1 and 2, there is a shielding effect that prevents direct radiation from that gap. 1. It is appropriate to provide J-r4.

In the structure shown above, the feeding globe 3 has a length of three-quarters of a wavelength, so the current distribution on the feeding probe 3 is approximately as shown by the dotted line, and the excitation phase within each antenna unit is indicated by the arrow. As shown in Figure 9, the phase is reversed. In order to improve directivity and gain with a stacked antenna, the radiated electromagnetic waves of each antenna unit must be in phase. In the present invention, the throwers of antenna units 1 and 2)
KJ? slots (e.g. throwers) 12a and 221 or slots (thrower) l located at the same distance from the feeding probe 3.
By reversing the inclination directions of ln and 22n, it is easy to align the phases of the electromagnetic waves radiated from all the slots to the same level. Details of the structure will be described in Examples below.

The reason why the center distance of the stacked antenna units is set to approximately 1/2 wavelength is because in stacked antennas, due to mutual interference between antenna units, the directional characteristics of one composite is a simple numerical combination of the directional characteristics of individual units as shown in Figure 3. Unlike,
Since side ropes may occur, it is common knowledge for those skilled in the art to determine the optimum dimensions for the purpose of use through actual measurements. It must also be taken into account that the current distribution on the feeding globe is different from the distribution in free space.

A converter is provided at the base of the feeding probe to convert the TE mode of the feeding waveguide into the TEM mode of the globe. In the case of coaxial power feeding, mode conversion is not necessary, but an impedance matching section is provided. In this case, in the present invention, a three-quarter wavelength globe is used and power is supplied at the antinode of the current, so the impedance is low and matching is easy.

〔Example〕

FIG. 6 is a front view of a two-stage stacked waveguide slot antenna for horizontally polarized waves for marine vessels to which the present invention is applied.

Slots 121 to 12n of length approximately λg/2 are provided at intervals of λ/2 for both antennas 1 and 2Vi, and each slot alternately reverses the inclination direction by 1-2 and then reverses the inclination direction by λ・,/2 difference. The phase excitation wave is inverted and radiated in the same phase. Also, in units 1 and 2, the slots at the same distance from the power supply probe 3 have opposite inclination directions.

All radiated waves are aligned in the same phase by correcting the phase caused by anti-phase excitation. Further, a spacer 4 which also serves as a shield is provided around the feeding probe 3, and auxiliary spacers 5A and 5B are provided between both ends of the antenna unit 20 to ensure stack spacing. Here, λ is the wavelength within the waveguide, and is slightly shorter than the wavelength λ at the 5-free middle.

FIG. 7 is a longitudinal cross-sectional view of the feed section of the two-stage stacked waveguide slot antenna of FIG.

Antenna Unique) I and 2 are slots 12a in the waveguide ~
12r+, 22a to 22n and power supply globe through holes are processed and used, and spacers 4 are inserted and stacked.

The feeding probe 3 is vertically supported by a ridge 7 with a chain for mode and impedance conversion attached to the inner wall of the feeding waveguide 6, and the antenna unit 2 is rotated about the feeding probe 3 by a horizontal axis. To, abutment 8
Attach via bearing 9 to.

The power supply globe 3 and the ridge 7 with a tensioner are shown in FIG. 8. The ridge 7 is usually made of the same material as the waveguide 6, and
Part f may be a straight line.

A power supply globe 3 is installed vertically on the upper end surface of the ridge 7, and the probe 3 is usually made of silver-plated hard copper wire.

In this structure, up to the feeding probe 3 is fixed, and only the antenna units 1 and 2 rotate, so there is an advantage that a rotating joint is not required in the feeding circuit.

〔Effect of the invention〕

The waveguide slot antenna of the present invention takes advantage of the narrow directivity in the horizontal plane, which is an advantage of conventional waveguide slot antennas, and improves the directivity in the vertical plane, which was the weak point. As a conventional radar antenna for ships, it not only reduces unnecessary reflections from water surfaces and flying objects and reduces false images on radar display drawings, but also improves vertical directivity and gain. As the technology improves, it is expected that the applications for general communications and satellite broadcast reception will expand.

Mechanically, by stacking two antenna units closely or at a relatively narrow interval with a spacer interposed therebetween, there is an effect that the strength is increased compared to the antenna unit alone.

Furthermore, since the structure is such that only one three-quarter wavelength glow 1 is held through both stacked antenna units for power feeding, it is extremely simple and can also be used as a radar antenna. As shown in the figure, since only the antenna unit is rotated around the fixed feeding globe as the central axis, it is convenient that the conventional radar antenna rotation mechanism can be used almost as is.

[Brief explanation of the drawing]

Fig. 1 is a partial cross-sectional diagram of the waveguide slot antenna of the present invention, Fig. 2 is a vertical cross-sectional view of Fig. 1, Fig. 3 is a composite radiation characteristic diagram of the stack antenna, and Fig. 4 is a waveguide @ FIG. 5 is a shape diagram of a ground-fed waveguide slot antenna, FIG. 5 is a shape diagram of a globe-fed waveguide slot antenna, and FIG. 6 is a front view of an embodiment of the present invention. FIG. 7 is a longitudinal cross-sectional view of a power feeding section showing an embodiment of the present invention, and FIG. 8 is an external view of a power feeding rope and a tapered ridge. 1ψ2... Waveguide slot antenna unit, 11.
21...Slot surface, 12 gourd-12n, 22-22n...slot, 3...Power supply glove, 4...
5A・5B... Spacer, 6... Power supply waveguide, 7.
...Taper ridge, 8...Abutment, 9...Bearing. s 1 Country No. 3

Claims (1)

[Claims] Align the slot surfaces of one or two waveguide slot antenna units, stack them so that the center distance is approximately 1/2 wavelength, and insert a 3/4 wavelength feeding probe through each antenna unit. A waveguide slot antenna is provided, and the slots located at the same distance from the feeding probe of each antenna unit have opposite inclination directions.