JPS6036643B2 - Multi-horn fed offset parabolic antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an offset parabolic antenna that has good antenna efficiency and cross-polarization characteristics among open square antennas used for wireless communication.

Offset parabolic antennas have the advantage of being small, lightweight, and having good wide-angle directivity characteristics.

However, since the reflective mirror surface is asymmetrical, a high cross-polarized component is generated on the mirror surface, and the efficiency is significantly reduced due to the reduction in side lobes. Among these two drawbacks, it has been proposed to use a horn called a trimode horn as the primary radiator as a method to improve the cross-polarization characteristics. This is TE... TE2
,,TM,. By appropriately controlling the phase and amplitude of the three waveguide modes, radiation characteristics of the horn can be obtained that cancel out the cross-polarized components generated on the mirror surface. However, since three waveguide modes are used, it is difficult to align the phases over a wide frequency band. Therefore, when this type of horn is used, there is a drawback that the frequency range in which cross-polarized waves can be suppressed becomes narrow. It is known that in order to increase the efficiency of an antenna while having low sidelobe characteristics, it is sufficient to lower the peripheral level of the antenna closed-plane electric field distribution and widen the flat region in the central portion.

However, the various horns that have been used as primary radiators so far all have unimodal radiation characteristics centered around the horn axis, so if the peripheral level is kept low, a flat distribution can be achieved in the center. This resulted in a sloped distribution, which had the disadvantage of low efficiency. The present invention provides a multi-horn-fed offset parabolic parabolic antenna that has low cross-polarization components and high efficiency over a wide frequency range by using a plurality of appropriately placed horns in a primary radiator system. It is.

The present invention will be explained in detail below using the drawings. FIG. 1 shows an embodiment of the present invention, and to simplify the explanation, a case is shown in which the horn is composed of two horns. In Figure 1,
1 is a reflecting mirror, and 2 and 3 are horns constituting the primary radiator system, in which a conical horn is used. 4 and 5 are central axes of the conical horns 2 and 3, respectively, 6 is a symmetry plane, 7 is an antenna closing plane, and 8 is a radio wave path.

The central axis 4 of the conical horn 2 faces the right half surface of the reflecting mirror 1 when viewed from the front, and mainly irradiates this right half surface.
The central axis 5 of the conical horn 3 faces the left half surface, and mainly irradiates the left half surface. The radiation characteristics of the primary radiator system are
It is given as the sum of the radiated electric fields of these two horns.
Figure 2 schematically shows the radiation characteristics of the primary radiator system in a plane containing the central axes of the two horns, 9 is the radiation characteristic of conical horn 2, and 1 is the radiation characteristic of conical horn 3. , 11
represents the radiation characteristic of the primary radiator system given as the sum of 9 and 10.

For reference, 12 shows the radiation characteristics when power is supplied by a single conical horn with a beam width. As is clear from FIG. 2, by appropriately selecting the center direction and radiation characteristics of each horn, it is possible to widen the flat region in the central portion of the radiation electric field distribution of the primary radiator system. Therefore, if the reflector shape and the installation situation of the primary radiator system are properly designed, the closed-plane electric field distribution can be made flat in the center, and efficiency can be improved. Since we are talking about the case where there are two horns, we have described a method to create a flat part at the center of the aperture field distribution within the cross section perpendicular to the plane of symmetry 6. However, by increasing the number of horns, Similarly, a flat portion can be created in the center of other cross sections.

Next, the effect of improving cross-polarization characteristics will be explained.

FIG. 3 is a detailed view of the primary radiator system, where 13 shows the open field polarization plane of the conical horn 2, and 14 shows the tortoise field polarization plane of the conical horn 3. When power is fed with a polarization plane parallel to the plane of symmetry 6 of the reflecting mirror as in the conventional case, the Sekiguchi plane electric field distribution tilts to the right on the right half plane and tilts to the right on the left half plane, as shown in the electric field direction 15 indicated by the chain line in Fig. 4. It will be the opposite. Therefore, as shown in Figure 3, by tilting the plane of polarization of the electric field in the conical horn 2 that irradiates the right half plane counterclockwise, and in the conical horn 3 that irradiates the left half plane clockwise, the polarization plane of the electric field is tilted in the open □ plane. The electric field distribution can be approximately parallel, such as the electric field orientation 16. Therefore, it is possible to reduce the peak of cross-polarized waves. Although the case of vertically polarized waves has been described above, the peak of cross-polarized waves can be similarly reduced in the case of horizontally polarized waves.

In order to reduce the cross-polarized wave component in the front direction, which is a problem when the antenna faces directly, the antenna closed-plane electric field distribution needs to be plane symmetric with respect to the plane of symmetry 6, so the phase center of the horn must be The position, direction of the central axis, and inclination of the plane of polarization of the electric field must be plane symmetric. However, the direction of the phase center and central axis of at least one horn may be arranged on the plane of symmetry 6. The above description has been made using conical horns as the horns constituting the primary radiator system, but the present invention can also be applied to other horns such as corrugated horns, dual mode horns, converging body horns, etc. Can be configured.

In order to improve efficiency and suppress cross-polarized components, it is more effective if the radiation characteristics of the primary radiator system do not have a phase distribution. There is a need.

As shown in FIG. 5, the central axes 4, 5 of the conical horns 2, 3
The conical horns have conical rods 17, 18 extending outward from the throats of the conical horns 2, 3 through the opening □, and the phase centers 19, 20 of the radiated electric field protrude outside the conical horns. When the primary radiation system is composed of a dielectric horn shaped like the dielectric bars 17 and 18 that exist in the silkworm body, the phase centers 19 and 2 of the dielectric horn are
0 can be brought closer than in the case of a conical horn, etc., so the effect of the present invention is particularly large. As described above, according to the present invention, it is possible to realize an offset parabolic antenna with high efficiency and good crossed polarization characteristics.

If the efficiency of the antenna improves, it will be possible to lower the output power of the transmitter, extend the distance between relays, and make the antenna smaller.
It has the advantage that wireless communication lines can be constructed at low cost. Furthermore, if the cross-polarized wave characteristics are improved, there is an advantage that frequencies can be used more effectively by sharing polarized waves.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an embodiment of the offset parabolic antenna of the present invention, Fig. 2 is a radiation characteristic diagram showing the primary radiator system used in the present invention in comparison with a conventional example, and Fig. 3 is an implementation of Fig. 1. FIG. 4 is an enlarged view of the primary radiator system part in the example, FIG. 4 is a diagram showing the direction of the electric field at the antenna closing surface, and FIG. 5 is a side view of the primary radiator system constructed of a dielectric concentrated horn. 1... Reflector, 2, 3... Horn, 4
, 5...Horn center axis, 6...Symmetry plane of reflecting mirror, 7...Antenna opening □ plane, 8...
Radio wave path, 9, 10...Radiation characteristics of each horn, 11...Primary radiator system radiation characteristics, 12...
...Primary radiator radiation characteristics of the subordinate, 13, 14...
... Polarization plane of electric field, 15 ... ... Direction of open field electric field of secondary column, 16 ... ... Direction of closed surface electric field in the present invention, 17, 18 ... ... Electromagnetic body Bar, 19, 20...
...The phase center of the electrical power collection east type horn. Large 1 figure, Ice 2, Ice 3, Ice 4, Year 5

Claims (1)

[Scope of Claims] 1. In an offset parabolic antenna equipped with a primary radiator system and a single reflecting mirror, the primary radiator system has a configuration consisting of a plurality of horns, and each horn is symmetrical with respect to the reflecting mirror. At least one pair of horns are arranged in a plane symmetrical position with respect to a plane or on the target plane so that the central axes of the horns substantially intersect at a point near the focal point of the reflecting mirror, and are in a plane symmetrical position. is a multi-horn power feed off, characterized in that the feed polarization plane forms an angle other than 0° or 90° with the plane of symmetry, and the inclinations of the feed polarization planes are set to be plane symmetrical to each other. Set parabolic antenna. 2. The horn of the primary radiation system has a dielectric rod extending from the throat of the conical horn to the outside through the opening on the central axis of the conical horn, and the phase center of the radiated electric field protrudes outside the conical horn. 2. A multi-horn fed offset parabolic antenna according to claim 1, characterized in that a dielectric focusing type horn is used which is formed in the shape of said dielectric rod so as to exist in a dielectric rod portion.