JPS6319083B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a polarization splitter that separates two radio waves having mutually orthogonal polarization planes and different frequencies according to the polarization plane.

In satellite communications, etc., in order to maintain good communication line quality, the transmitted wave sent from the satellite to the ground and the received wave received by the satellite from the ground use radio waves with orthogonal polarization planes and different frequencies, and the isometry between transmitter and receiver is I try to take good care of myself. Furthermore, communication antennas used for such communications are generally used for both transmission and reception, both onboard satellites and at ground stations, and the transmitted and received waves are separated by the antenna feeding system, but this separation means A polarization splitter is used as one of the methods.

When using such a polarization splitter, since the polarizations are orthogonal and the frequencies are different, the transmission system for low frequency waves is generally oversized for the high frequency waves, and the high frequency waves are In addition to the generation and propagation of modes other than the fundamental mode, the isolation between transmission and reception deteriorates, and the characteristics of the demultiplexing terminal for high frequency waves, such as group delay characteristics, may deteriorate.

This invention improves the polarization splitter by connecting a spacer that blocks high frequency waves and acts as a matching element for low frequency waves to the coupling hole that splits low frequency waves. It is something that

This will be explained below with reference to the drawings.

Figure 1 shows an example of a conventional polarization demultiplexer.
are the main waveguides in which waves of mutually orthogonal polarization propagate, 2
a, 2b are coupling holes, 3a, 3b are short circuit plates, 4a,
4b is a connecting waveguide, and 5a and 5b are electric fields of waves that pass through the main waveguide and propagate through the connecting waveguide 4, respectively.

Now, in FIG. 1, of the two mutually orthogonal waves propagating through the main waveguide 1, the wave of the electric field 5a is reflected by the shorting plate 3a and guided to the connecting waveguide 4a by magnetic coupling through the coupling hole 2a. Similarly, the wave of the electric field 5b is guided to the connecting waveguide 4b, and the two orthogonal radio waves are separated by polarization.

In FIG. 1, for the sake of simplicity, it is assumed that the electric field of the low frequency wave is 5a, that of the high frequency wave is 5b, and the main waveguide 1 is a circular waveguide.

Therefore, if the system for splitting low frequency waves, that is, the main waveguide 1, coupling hole 2a, shorting plate 3a, and connecting waveguide 4a, is oversized for high frequency waves, the connecting waveguide Due to the asymmetry of the main waveguide 1, the coupling hole 2a, and the shorting plate 3a, the wave incident from the wave 4b has the oversized portion, in addition to the electric field 5b which is the fundamental mode, its cross polarization,
Other modes such as TMo ₁ mode are generated and propagated.

Now, if a high frequency wave can propagate orthogonally to the electric field 5a in the connecting waveguide 4a for low frequency waves, when the TM mode occurs, the coupling hole 2a will be caused by the circumferential magnetic field of the main waveguide 1. A wave perpendicular to the electric field 5a propagates through the waveguide 4a, and the two waves cannot be separated.

In addition, due to the line design of the communication system including antennas and repeaters, if the transmission system is connected to the waveguide 4a with a low-pass filter that blocks the propagation of high-frequency waves, the connection waveguide 4a The wave propagating perpendicularly to the electric field 5a is reflected by the low-pass filter to generate a standing wave. In this case, the group delay characteristic seen from the connecting waveguide 4b that separates high frequency waves will be degraded due to the generation of the standing waves.

In order to eliminate such drawbacks, this invention
A spacer that blocks high frequency waves is inserted between the coupling hole 2a, which demultiplexes low frequency waves, and the connecting waveguide 4a, and waves perpendicular to the electric field 5a propagate within the connecting waveguide 4a. In addition to preventing this, impedance matching as seen from the connecting waveguide 4a is achieved.

This will be explained below with reference to the drawings.

FIG. 2 shows one embodiment of this invention, and 1 in the figure
5 are the same as those shown in FIG. 1, and 6 is a spacer.

When the electric field 5b propagates through the main waveguide 1, the coupling hole 2a
Also, the TM mode occurs due to the shorting plate 3a.

Since the TM mode has a magnetic field component in the circumferential direction of the main waveguide 1, waves in a direction perpendicular to the electric field 5a are excited and propagated in the connecting waveguide 4a through the coupling hole 2a.

On the other hand, the condition for blocking radio waves in the waveguide is given by the following equation (1) in the case of the fundamental mode.

λc=2×a (1) where λc: Cutoff wavelength a: Waveguide dimension in the direction perpendicular to the electric field of the fundamental mode Therefore, the waveguide dimension in the direction of the electric field 5a of the spacer 6 is set as By selecting 1/2 or less of the wavelength, high frequency waves are blocked in the direction orthogonal to the electric field 5a according to the above equation (1). Also,
By selecting the waveguide dimension of the spacer 6 in the propagation direction of the electric field 5a to be 1/4 or more of the wavelength of the high frequency wave, the blocked waves are sufficiently attenuated, and the high frequency waves are transferred to the connecting waveguide 4a. is not propagated to

Further, by appropriately selecting the dimensions of the spacer, there is an advantage that it can be used as an impedance matching device between the connecting waveguide 4a and the main waveguide 1.

Note that although the case where the main waveguide 1 is a circular waveguide has been described above, the same applies to a rectangular waveguide.

Moreover, although the orthogonal branching type polarization splitter has been described, the same applies to the case where the branching terminal for high frequency waves is located in the tube axis direction of the main wave tube.

As described above, in the polarization demultiplexer according to the present invention,
The degree of separation between the two waves is increased by inserting a waveguide whose electric field direction is orthogonal to the low frequency waves and which blocks the high frequency waves into the coupling hole that separates the low frequency waves, and This has the advantage of improving the group delay characteristics of high frequency waves and also improving the impedance of low frequency waves.

[Brief explanation of the drawing]

Figure 1 shows an example of a conventional polarization splitter, Figure 2 shows an example of a conventional polarization splitter.
The figure shows an embodiment of a polarization splitter according to the present invention, in which 1 is a main waveguide, 2 is a coupling hole, 3 is a short circuit plate, 4 is a connecting waveguide, and 6 is a spacer. In the drawings, the same or corresponding parts are designated by the same reference numerals.

Claims (1)

[Claims] 1 Consists of a main waveguide having a coupling hole provided on the pipe wall and a shorting plate provided parallel to the coupling hole, and a connecting waveguide connected to the coupling hole, with planes of polarization perpendicular to each other. In a polarization demultiplexer, which separates two waves with different frequencies according to the plane of polarization, and in which a wave with a higher frequency plate number among the two waves can propagate in modes other than the fundamental mode, Between the coupling hole that demultiplexes low frequency waves and the connection waveguide connected to the coupling hole, the dimension in the direction of the electric field in which the low frequency waves propagate should be 1/2 or less of the wavelength of the high frequency waves. What is claimed is: 1. A polarization demultiplexer characterized in that a waveguide having a length of 1/4 or more in the tube axis direction is connected thereto.