JPH0614603B2 - Antenna system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention provides a void lens antenna composed of two parallel curved surface conductors with a small hole formed in the vicinity of the focal point of any one of the curved surface conductors. Alternatively, by projecting a short central conductor to the center of the small hole so that the electric field of the electromagnetic wave of the TEM mode propagating in the air gap lens is not significantly disturbed, electromagnetic coupling is performed and the electromagnetic wave supplied from the power supply line is transferred. A plurality of high-power devices for feeding into the air gap lens are mounted, and a plurality of high-quality fan beams with low distortion corresponding to the respective power feeders are generated over a wide frequency band in all directions in any direction, and The present invention relates to an antenna device that can accurately set the angle.

(Prior Art and Problems Thereof) There is a patent application (Japanese Patent Application Laid-Open No. 58-123207) of the present applicant as an antenna device using a void lens.
In this case, since the power feeders that occupy the entire width of the air gap are arranged and fed in the air gap of the air gap lens, the electromagnetic waves in the TEM mode propagating in the air gap lens when power is supplied from the opposite side are supplied to the power feeder. Block, so that the azimuth angle of the fan beam emitted from the air gap lens aperture is 1
It was limited to the quadrant (0 to 90 degrees). Therefore, in order to generate a fan beam in all directions using the conventional air gap lens antenna, four air gap lens antennas are required.

Further, as a prior art having the same purpose as the present invention, "a high gain antenna structure having an effective range of 360 °" (Japanese Patent Publication No. 44-4).
372). The gist of this Japanese Patent Publication No. 44372 is that "a radio wave lens is divided into two in the thickness direction, a power feeder is connected to the focal position of the first half, and the focal position on the opposite side in the diametrical direction. The radiator is connected to the second half and the appropriate electromagnetic energy is coupled between the first half and the second half. " But with this configuration,
Since the electromagnetic lens is divided into two in the thickness direction and the radio waves propagate separately in the upper and lower layers, they are combined, so irregularities in the directivity are likely to occur due to interference between the two, and the directivity is distorted like a worm. It is easy to become. When used for direction finding, directional eclipse-like collapse directly affects azimuth measurement error, so it was especially necessary to invent a separate antenna configuration that does not cause eclipse-like distortion in the beam pattern. . Further, in the structure of JP-B-44-4372, the mechanism of the power feeding portion is likely to have frequency characteristics, and the band is narrow as a whole, and there is a restriction that the wide band characteristics of the radio wave lens cannot be fully utilized. Further, in the structure of Japanese Patent Publication No. 44372/1969, a fixed internal loss of 6 dB is constantly generated in the lens. If the loss of 6 dB is converted into a detection distance, the detection distance is reduced to about 1/2 in the case of an antenna for direction detection. On the contrary, if the detection distance needs to be constant,
To compensate for the 6 dB loss, the diameter of the radio wave lens must be increased by about 4 times. As described above, the internal loss of 6 dB has a great influence, and there is a possibility that it may become a serious weak point that the utility as an antenna for direction finding is lost. The present invention has been made in view of such circumstances.

(Means and Actions for Solving Problems) The present invention is capable of generating a multi-beam composed of fan beams in all directions in a wide frequency band by using one air gap lens, and is easy to design and adjust. It is intended to provide a simple antenna device.

The present invention relates to a TEM mode electromagnetic wave propagating in a void lens via a void lens and a small hole formed in the vicinity of the focal point of one parallel curved surface conductor of the void lens or a short center conductor arranged at the center of the small hole. Has a plurality of feeders that are electromagnetically coupled to feed the electromagnetic waves supplied from a feeder line to the air gap lens, whereby a plurality of fan beams are arbitrarily distributed in all directions in a plane including the lens aperture. Can be generated. At that time, the directivity can be improved by disposing an annular electromagnetic wave absorber concentric with the center of the air gap lens in the vicinity of the small hole.

Another feature is that the usable frequency band is wide.

(Embodiment) An embodiment of an antenna apparatus according to the present invention will be described below with reference to the drawings.

1 and 2 show a reference example showing a structure on which the present invention is based, FIG. 1 shows a structure of a feeder portion, and FIG. 2 shows an entire structure. In these drawings, the air gap lens is composed of two parallel curved surface conductors A and A'and matching flares attached to their peripheral portions, and in this reference example, power is supplied from the lower curved surface conductor A. Therefore, the feeder of FIG. 1 is provided on the curved conductor A. That is, through the small hole 2 formed in the curved surface conductor A at or near the focal point of the air gap lens, the coaxial core wire 1 is projected into the air gap lens by about 2 mm (the air gap between the curved surface conductors A and A '), Electromagnetic coupling is made to TEM mode electromagnetic waves propagating in the space between the parallel curved surface conductors. The protruding length of the core wire 1 is set to be 1/2 or less of the gap width. The other end C of the coaxial line is a terminal for connecting to an external power supply line. B, which encloses the short core wire 1, is an insulator of coaxial wires of Teflon. The outer conductor of the coaxial wire is connected to the curved conductor A. In this reference example, the number of power feeders is 60.
And are arranged at intervals of 6 degrees with respect to the center of the air gap lens.

In the above configuration, if a predetermined electromagnetic wave is fed to the air gap lens by using each feeder having the coupling portion made of the core wire 1, the electromagnetic wave in the TEM mode propagating in the coaxial feeder will be the two parallel curved surface conductors. The TEM mode electromagnetic wave propagating through the air gap between A and A'is converted into a TEM mode electromagnetic wave and sent out into the lens, and a fan beam is radiated into the space from the flare 4 at the lens peripheral edge in the direction corresponding to each feeder. .
That is, one fan beam is formed for one feeder, and a plurality of fan beams can be simultaneously obtained by exciting a plurality of feeders at the same time.

In addition, if the small hole 2 is made slightly larger so that the core wire 1 can be slightly moved in the circumferential direction of the air gap lens, the tip of the fan beam can be accurately set in direction.

3 and 4 show another reference example of the present invention, FIG. 3 shows the configuration of the power feeder portion, and FIG. 4 shows the overall configuration. In these figures, two small holes 2 are formed close to the curved surface conductor A at or near the focal point of the air gap lens, and an array of the two small holes is set in the lens radial direction. And
2 mm through the core wires 1 and 1'of the coaxial wire through the two small holes 2.
To the extent that it projects into the air gap lens (the air gap between the curved surface conductors A and A '), it is electromagnetically coupled. B that wraps the core wire 1 is an insulator of a coaxial wire such as Teflon. Close to each other (about 12 to 13 mm)
The two core wires 1, 1'arranged are connected to the other terminal C of the coaxial wire via a 3 dB coupler (directional coupler) 3. Third
Of the core wires 1 and 1'in the figure, the one closer to the central portion of the air gap lens is connected so as to delay the phase angle of the electromagnetic wave by 90 degrees. When the connection is made in this way, directivity is generated toward the center of the air gap lens due to phase interference between the coupling portion on the core wire 1 side and the coupling portion on the core wire 1'side. Also in the case of this reference example, the number of power feeders was 60, and they were arranged at an interval of 6 degrees with respect to the center of the air gap lens.

In the above configuration, if a predetermined electromagnetic wave is fed to the air gap lens by using the feeder having the core wires 1 and 1 ', the TEM mode electromagnetic wave propagating in the coaxial feeder line will be the two parallel curved surface conductors A and A. Are converted into electromagnetic waves in the TEM mode propagating in the space between the ‘′’ and transmitted into the lens, and the fan beams are radiated into the space from the flare 4 on the peripheral edge of the lens in the direction corresponding to each feeder. . in this case,
There is an advantage that the back lobe can be reduced because the directivity is generated toward the central portion of the air gap lens due to the phase interference between the coupling portion on the side of the core wire 1 and the coupling portion on the side of the core wire 1 '. Small hole 2
If the core wires 1 and 1'are made to be slightly movable in the circumferential direction of the air gap lens by making them slightly larger, the tip of the fan beam can be accurately set in direction.

5 and 6 show an embodiment of an antenna device according to the present invention, in which a radio wave absorber is added to the structure of the reference example to further improve the characteristics. FIG. 6 is for explaining the operation of FIG. In this embodiment, in order to reduce the side lobe, a ring shape is formed in the vicinity of the coupling portion (small hole 2) in which the core wire 1 of the air gap lens shown in FIG. 2 is arranged so as to share the center of the air gap lens. It has a structure in which the radio wave absorber 5 is arranged. In FIG. 6, for example, the electromagnetic wave fed from the feeder at point F propagates while refracting through the air gap lens as shown in F → G and F → H in FIG. 6, but corresponds to the feeder at point F. The main beam of the fan beam of the air gap lens is formed by each component of the electromagnetic waves that reach the opening on the opposite side as in F → G, and these electromagnetic waves are transmitted through the ring-shaped electromagnetic wave absorber 5 substantially vertically, and relatively. Propagate across short distances. On the other hand, F → H that affects the sidelobe level
Since the electromagnetic wave diffused and propagating to the side crosses the annular electromagnetic wave absorber 5 obliquely as shown in the figure, it is attenuated by the electromagnetic wave absorber over a relatively long distance.

As a result, the electromagnetic waves propagated from F to H are relatively weakened,
Therefore, the level of the side lobe in that direction also decreases accordingly.

The above is the configuration and the operating principle of the embodiment of the present invention, and the actual measurement results will be described below.

In the actual measurement example, the radius of the air gap lens is 259 mm, the length of the generatrix of the mirror surface portion of the flare 4 is 70 mm, and the inclination angle of the flare 4 with respect to the horizontal plane is 26 degrees.

FIG. 7 is a result of actually measuring the horizontal plane directivity of three adjacent fan beams in the case of the reference example shown in FIGS. 1 and 2. Although there are 60 feeding points, since the antenna system is completely axisymmetric with respect to the center of the air gap lens, the adjacent 3
If the beam of the book is shown, the others are exactly the same. Actual measurement result is 3
It is shown that a good beam pattern can be obtained from GHz to 16 GHz, and it can be said that the directional frequency band is extremely wide.

FIG. 8 (B) is an actual measurement result showing that the back lobe can be reduced in the case of another reference example shown in FIGS. 3 and 4. The frequency was 7 GHz, and the position of the feeding point (small hole 2) was located 40 mm inside from the circumference of the air gap lens toward the center as measured on the curved conductor. FIG. 8 (A) is the directivity in the case of the reference example in which the air gap lens antenna of FIG. 2 is constructed using the power feeder of FIG. 1, and FIG. 8 (B) is the power feeder of FIG. It is the directivity in the case of another reference example in which the air gap lens antenna of FIG. By comparing (A) and (B) of the same figure, the back lobe {P part of (B) of the figure} is significantly lower than the level of the corresponding part of (A) of the figure, and the level of the back lobe is reduced. It shows that reduction is possible.

FIG. 9 (B) shows the measurement results in the case of the embodiment in which the radio wave absorber 5 is loaded as shown in FIG. 5 using the power feeder shown in FIG. The frequency was 10 GHz. The feeding point is the same as in the case of FIG. Comparing this with the directivity in the same figure (A) when the electromagnetic wave absorber is not loaded, in the directivity in the same figure (B), the peak portion of the side lobe indicated by Q in the same figure (A) is 3 ~ 4d
B It can be confirmed that it is decreasing. That is, the side lobe level when the radio wave absorber is loaded is given by the level difference indicated by R in the figure (B), and is clearly improved from the side lobe level in the figure (A). The fifth
In the illustrated embodiment, the feeding structure shown in FIGS. 1 and 2 using the small hole 2 is used, but the feeding structure shown in FIGS. 3 and 4 may be adopted.

(Effects of the Invention) As described above, the antenna apparatus of the present invention is capable of generating multi-beams over an extremely wide frequency band, and is a high-quality antenna that does not cause worm-like distortion in the beam pattern in all bands. Directivity can be achieved, and fixed internal loss does not occur,
Fine adjustment of the beam direction is easy, and the side lobe level can be improved, which is a great practical effect.

[Brief description of drawings]

FIG. 1 is a perspective view of a power feeder which feeds power through one small hole used in a reference example of an antenna device which is a premise of the present invention, and FIG. 2 omits a cross section and an upper curved conductor of the entire configuration of the reference example. FIG. 3 is a configuration diagram showing a plane, FIG. 3 is a perspective view of a power feeder for supplying electricity by two small holes used in another reference example which is a premise of the present invention, and FIG. FIG. 5 is a block diagram showing a plane without the upper curved conductor, FIG. 5 is a block diagram showing the loading position of the electromagnetic wave absorber effective for side lobe reduction, which is an embodiment of the antenna device according to the present invention, and FIG. FIGS. 7 to 9 are graphs showing an example of directivity measurement according to the reference example and the embodiment of the present invention, for explaining the principle of reducing the side lobe by loading the radio wave absorber. 1 ... Core wire, 2 ... small hole, 3 ... 3 dB coupler, 4 ...
… Flare, 5 …… Radio wave absorber.

Claims (2)

[Claims] 1. An air gap lens composed of two parallel curved surface conductors, and a small hole formed in the vicinity of the focal point of any one curved surface conductor of the two parallel curved surface conductors, or through a small hole. A TEM mode electromagnetic wave propagating in the gap between the parallel curved surface conductors via a short center conductor arranged at the center of the hole and having a length of 1/2 or less of the gap width between the parallel curved surface conductors. An antenna that is electromagnetically coupled to the power supply line and that sends the electromagnetic wave supplied from the power supply line to the air gap lens between the parallel curved surface conductors, and that generates a fan beam corresponding to each power supply line from the lens aperture. In the device, an annular electromagnetic wave absorber concentric with the center of the air gap lens is arranged in the vicinity of the small hole of the air gap lens, and a directional side lobe of a fan beam emitted from the opening of the air gap lens. Reduced Antenna device according to claim Rukoto. 2. The number of small holes provided in the vicinity of the focal point of the air gap lens is one or more for the one feeder, and the feeder lines are electromagnetically coupled to these small holes via a directional coupler. By generating directivity in the lens from the position of these small holes toward the center of the air gap lens,
The antenna device according to claim 1, wherein a directivity back lobe or side lobe of a fan beam emitted from the air gap lens aperture is reduced.