JPS5875904A - Conical beam scanning antenna - Google Patents

Abstract

PURPOSE:To reduce adjustment of mass balance and an increase in weight, and to rotate two split hyperboloidal subordinate reflectors by moving forth and back those reflectors in antenna axial directions, and thus rotating them. CONSTITUTION:A hyperboloidal subordinate reflector 2 is divided into two by a plane including an antenna axis 7, and those two split subordinate reflectors 2 are arranged in such a way that their focuses deviate from an optimum position coincident with the focus of a parabolic main reflector 3 and the phase center of a primary radiator 1 forward and backward in directions of the antenna axis 7; and the subordinate reflector axis coincides with the antenna axis 7. A spherical wave from the primary radiator 1 is radiated by an antenna opening surface 12 in the form of a plane wave, but its phase distribution shows phase leading in the upper half and phase lagging in the lower half. The antenna pattern of the wave surface corresponds equivalently to that a beam axis 13 deviates from the antenna axis 7 in a phase lagging direction, and the subordinate reflectors 2 are turned by a motor 8 to obtain a conical scanning beam.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a conical scanning beam antenna device, which is a type of automatic tracking antenna.

Conventionally, in an automatic tracking antenna using two reflecting beams, a device as shown in FIG. 1 is known as a device that performs conical scanning. That is, as shown in FIG.
, hyperboloid sub-reflector (hereinafter simply referred to as "sub-reflector")
2. Parabolic main reflector (hereinafter simply referred to as "main reflector").

)3 constitutes a Cassegrain antenna system. Further, in FIG. 1, 4.5 is the focal point of the sub-reflecting steel 2 indicated by a broken line, the focal point 4 coincides with the focal point of the main reflecting mirror 3, and the focal point 5 coincides with the phase center of the primary radiator 1. In the conventional device, the electric motor 8 is operated with the antenna axis 7 as the rotation axis for the sub-reflector 2 which is eccentric within the focal plane of the main reflector 4, that is, the sub-reflector 2 whose sub-reflector axis 6 is offset from the antenna axis 7. It rotates at 1 and emits a conical scanning beam.

However, in this device, in order to smoothly rotate the hyperboloid sub-reflector 2 whose center of gravity has been largely displaced due to eccentricity, it is necessary to adjust the mass balance by attaching a counterbalance 9 to the hyperboloid reflector 2. . Furthermore, adding it increases the weight of the sub-reflector, which has the disadvantage of making high-speed rotation difficult.

The present invention improves this point, and is an antenna device that can greatly reduce mass balance adjustment and weight increase, and can radiate a conical scanning beam by smoothly rotating a hyperboloid sub-reflector. The purpose is to provide

The present invention provides a two-plate reflector (caseplane) antenna in which the sub-reflector (hyperboloid) has two planes including the antenna axis.
The configuration is such that the two semi-hyperboloids are each deflected back and forth in the direction of the antenna axis from the optimal position of the sub-reflector, and rotated so that the center axis of the sub-reflector is aligned with the antenna axis. It is characterized by what it did.

An embodiment of the present invention will be described based on the drawings.

FIG. 2 is a block diagram of main parts of an embodiment of the present invention.

Compared to the conventional device shown in No. 1M, the sub-reflector 2 is divided into two along the plane including the antenna axis 7, and each of the sub-reflectors 2 is divided into two, with each focal point indicated by the broken line in FIG. Reflector 3
It is arranged to be displaced back and forth in the direction of the antenna axis 7 from the optimal position coinciding with the focal point of It has characteristics.

Other points are similar to the conventional example shown in FIG. 1, and the same reference numerals indicate the same parts.

If the sub-reflector 2 is now at the optimal position shown by the broken line, the spherical wave emitted from the -order radiator 1 will be radiated as a plane wave on the antenna aperture 12 when considered from a geometric optics perspective. Here, as in the present invention, instead of dividing the sub-reflector 2 into two and displacing each sub-reflector from its optimum position, the rotation axis of the sub-reflector 2 (which coincides with the antenna axis) is mechanically adjusted. This means that the phase center has moved relatively back and forth while maintaining balance.

As a result, in terms of geometric optics, the phase distribution of the reflected wave aperture 12 of this antenna system is as shown in FIG. 3 when compared with the phase distribution of the Cassegrain antenna system.
A distribution 14 is obtained in which the upper half leads and the lower half lags. Such a wavefront antenna pattern is equivalent to the beam axis 13 being shifted in a direction in which the phase lags with respect to the antenna axis 7. Therefore, in this state, by rotating the sub-reflector 2 around the antenna axis 7 using the electric motor 8, it is possible to obtain a conical scanning beam.

In this structure, since the sub-reflector 2 always has an equal mass distribution around its axis of rotation 6, there is no need for extra mass balancing.

As described above, according to the present invention, each of the sub-reflecting mirrors divided into two parts is moved and rotated in the direction of the antenna axis in accordance with the desired beam deviation angle. therefore,
When obtaining a conical scanning beam, balance adjustment and weight increase can be significantly reduced, and high-speed rotation can be performed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the main parts of a conventional device. FIG. 2 is a diagram showing the main part of an embodiment of the present invention. FIG. 3 is an aperture surface phase distribution diagram of the embodiment described above. 1... -order radiator, 2... sub-reflector, 3... main reflector, 6... sub-reflector axis, 7... antenna axis, 8...
...Electric motor, 9...Counter balance, 12...Antenna aperture surface. Patent Applicant NEC Corporation Agent Patent Attorney Nao Ide Takasouri 1 Zusuke 2 Kaiji 3 Dias

Claims (1)

[Claims] (1) A primary radiator that generates a beam of electromagnetic waves, a hyperbolic secondary reflecting steel that reflects this beam, and a parabolic primary reflecting mirror that converts the spherical wave reflected from the secondary reflecting steel into a plane wave. In the antenna, the sub-reflector is divided into two parts along a plane including the antenna axis, and each of the two divided parts can be deflected back and forth along the direction of the antenna axis of the main reflector. 4. A conical beam scanning antenna, comprising means for rotating the sub-reflector about the antenna axis.