JPH02179001A - Circularly versus linearly polarized wave converter - Google Patents

Abstract

PURPOSE:To decrease the length of a dielectric plate further in the direction of waveguide axis and to obtain the excellent matching of input and output impedances by providing a hole perpendicularly to a plate face in the vicinity of the end of the dielectric plate. CONSTITUTION:A thick dielectric plate 2 is inserted so as to be in contact with the diameter of a circular waveguide 1. Holes 4a, 4b are provided in the vicinity of end faces 3a, 3b of the plate 2 thereby preventing discontinuous capacitance at the end faces 3a, 3b near the waveguide axis in the circular TE11 mode having an electric field component En perpendicular to the plate 2. The size of the holes 4a, 4b and the distance from the end face are decided so that the plate 2 is acquired of the impedance matching in the circular TE11 mode. Thus, attended with the arrangement of the circular holes 4a, 4b, the size of a stepwise impedance conversion section at both ends of the plate in the waveguide axis direction is slightly corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a circular linear polarization converter attached to a primary radiator of a parabolic antenna for receiving satellite broadcasting.

Conventional technology A circular linear polarization converter generally has a structure in which a dielectric thin plate of an appropriate length is inserted in the axial direction of a circular waveguide so as to be in contact with the diametrically inner wall of the waveguide. .

The operating principle of this type of circular linear polarization converter will be briefly explained below with reference to FIG. The thin dielectric plate 32 has the effect of retarding the phase for the circular TIE configuration 34, which has an electric field component parallel to it, and almost delays the phase for the circular TIE configuration 33, which has an electric field component perpendicular to it. No change.Two circular TKs.

One of the positions is parallel to the dielectric thin plate 32 and the other is perpendicular to the dielectric thin plate 32, and the dielectric is adjusted so that the phase difference between the two positions after passing through the dielectric thin plate 32 is 90 degrees. The length of the thin body plate 32 in the waveguide axis direction is determined experimentally.

On the other hand, the circularly polarized wave propagating inside the circular waveguide 31 is as follows.

Two orthogonal circles with a phase difference of 90 degrees T i! 1. It can be thought of as a vector composition of postures. Therefore, if one of the circular polarized waves is considered to be parallel to the dielectric thin plate 32, then two orthogonal circular circles τ”i
The phase difference after passing through the dielectric thin plate 3'2 in the j-shape becomes 0 or 180 degrees, and the combined wave becomes a linearly polarized wave.

As the performance required for this type of circular linear polarization converter, the dielectric thin plate 32
impedance matching is achieved, and the phase difference between the two circular T Els and the shapes formed by the dielectric thin plate 32 is exactly 90 degrees.

In the conventional circular linear polarization converter having the above structure, the thickness of the dielectric plate is made sufficiently thin so that the dielectric plate has a circular T E shape with an electric field component perpendicular to the dielectric plate. Impedance matching is achieved by making the impedance mismatch sufficiently small and tapering or stepping both ends of the dielectric plate in the waveguide axis direction only for the circular T E11 configuration with an electric field component parallel to the dielectric plate. It was something like that.

Problems to be Solved by the Invention Conventionally, a thin dielectric plate was often used as a dielectric plate inserted into a circular waveguide. Circular T E with an electric field component, , Circular T K with an electric field component perpendicular to the pose
, 1 configuration), the phase difference after passing through the dielectric plate could not be large, and it was necessary to make the dielectric plate longer in the tube axis direction in order to obtain the desired 90 degree phase difference. If a thick dielectric plate is used to shorten this, the phase difference will increase, but for a circular TK shape with an electric field component perpendicular to the dielectric plate,
Discontinuities in impedance, which can be ignored when the dielectric plate is thin, can no longer be ignored when the dielectric plate is thick. That is, there is a problem in that the input (or output) 'l/SWR of the dielectric plate deteriorates for the circular TK shape having an electric field component perpendicular to the dielectric plate.

An object of the present invention is to solve the above-mentioned problems that a thick dielectric plate has.

Means for Solving the Problems The present invention provides a circular TE having an electric field component perpendicular to the dielectric plate.
1. By providing a hole perpendicular to the plate surface near the end of the dielectric plate in the vicinity of the tube axis, where the dielectric plate has a strong electromagnetic influence on the above-mentioned condition, We tried to solve the above problem by performing impedance matching.

When the dielectric plate inserted into the working circular waveguide is thick, for a circular TE configuration with an electric field component perpendicular to the dielectric plate,
Circular TE1 due to the dielectric plate, which was small when the dielectric plate was thin. Postural impedance mismatch increases. In particular, the influence of the dielectric plate portion near the axis of the circular waveguide becomes large. This is 1 circular TK1. This is because the electric field energy of the shape is large near the tube axis.

When the dielectric plate is thick, both ends of the dielectric plate become capacitive discontinuities, resulting in impedance mismatching, compared to the circular TE having an electric field component perpendicular to the dielectric plate. By providing a hole of an appropriate size on the dielectric plate in the vicinity of the capacitive discontinuity, the degree of the capacitive discontinuity occurring in the τ''+1 configuration can be reduced.

In other words, consider that both ends of the dielectric part and the hole form an impedance conversion part between a circular waveguide part that does not include the dielectric plate and a circular waveguide part that includes the wide part at the center of the dielectric plate. be able to.

Embodiment FIG. 1 shows an embodiment of the present invention. This will be explained below based on the drawings. In FIG. 1, 1 is a C-120 standard circular waveguide (inner diameter 17.5 m), and 2 is a thick dielectric plate (thickness s, om) inserted so as to be in contact with the inner diameter.

The circular holes 4a and 4b are connected to the end surfaces 3a and 3b of the dielectric plate 2.
This is a hollow hole provided at the position shown in the figure near the hole. The operating state of the circular waveguide 1 is the circular TK state, as shown in Fig. 1 (aJ
From the left end of the circle TK1. A circularly polarized wave having a configuration 23 is incident, and is converted into a circular TK by the dielectric plate 2.

The component of the electric field vector component parallel to the dielectric plate Ict
A phase difference of 90 degrees occurs between the component In and the component In perpendicular to it, but originally these components were circularly polarized components with a phase difference of 90 degrees at the left end of ILI (Figure 1). Therefore, at the right end of FIG. 1 (IL), the phase difference between these two components is 0 or 180 degrees, and their combined wave is output as a linearly polarized wave.

The dielectric plate 2 is provided with step-shaped impedance conversion portions at both ends in the tube axis direction, so that impedance matching is achieved for the shape of a circular T I having an electric field component Σt parallel to the dielectric plate 2. There is. The dimensions of this stepped portion are determined experimentally. However, this dimension needs to be slightly corrected by providing circular holes 4a and 4b, which will be described later.

On the other hand, when the thickness of the dielectric plate 2 is relatively large as in this embodiment, a circular shape TX having an electric field component In perpendicular to the dielectric plate, end faces 3a and 3b near the tube axis with respect to the shape
In order to eliminate this, circular holes 4& and 4b of appropriate size are provided on the tube axis near each end face. The size of the circular holes 4N, 4b and the distance from the end face are the circular TI! ,,
It is determined experimentally to achieve impedance matching for the posture. As described above, for the circular shape Tl having electric field components parallel and perpendicular to the dielectric plate 2,
A state in which the impedance of the dielectric plate 2 is matched is obtained. However, the above-mentioned method of impedance matching is performed when the lengths 3&-3b of the main portions of the dielectric plates that are dominant in determining the phase difference caused by the dielectric plates 2 in both configurations have a certain value; The phase difference is not necessarily 90 degrees. Actually, the length of the main part of the dielectric plate is 3 &-
By changing 3b and repeating the impedance matching method described above, a desired circular-linear polarization converter can be obtained.

Effects of the Invention The dielectric plate inserted so as to be in contact with the inner diameter of the circular waveguide has a thickness such that it acts as a non-negligible discontinuity with respect to the circular τ”++ shape having an electric field component perpendicular to the plate surface. In the case of a circular linear polarization converter, a circular TE having an electric field component parallel to the dielectric plate, a circular Tic having an electric field component perpendicular to the orientation, a circular T K having an electric field component perpendicular to the orientation, , since the phase difference between the two forms after the form passes through the dielectric plate is larger than when the dielectric plate is thin (when the length of the main part of the dielectric plate is thick and thin), The dimension (length) of the dielectric plate in the tube axis direction (assumed to be equal) is relatively short, making it possible to obtain a phase difference of 90 degrees.

That is, it is possible to realize a circular linear polarization converter that is shorter in the tube axis direction of a circular waveguide and has good input/output impedance matching, which has great industrial value.

[Brief explanation of the drawing]

Figures 1a and 1b are front sectional views and side sectional views showing an embodiment of the circular linear polarization converter of the present invention, and Figures 2a and 2b are views of an example of a conventional circular linear polarization converter. They are a front sectional view and a partial side sectional view. 1... Circular waveguide, 2... Dielectric plate,
4IL, 4b... hole. Name of agent: Patent attorney Shigetaka Awano 1 person II
Figure I (b)

Claims (1)

[Claims] In a circular linear polarization converter configured with a plate-shaped dielectric inserted into a circular waveguide, a tapered or stepped impedance conversion section is provided at both ends of the dielectric in the tube axis direction of the waveguide. and having one or more holes in the plate surface of the dielectric near the tube axis of the circular waveguide in the dielectric portion other than the impedance conversion section. converter.