JPS6036142B2 - Branching circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a branching circuit used in satellite communications, etc., which uses two circularly polarized waves having anti-rotation relationships, and in particular aims at improving response characteristics. .

In a wireless communication system that uses two circularly polarized waves that are in a counter-rotating relationship with each other, the limited frequency band can be doubled by placing a separate communication signal on each circularly polarized wave. Can be done.

In this wireless communication system, two orthogonal linearly polarized waves are converted into two circularly polarized waves having an antirotating relationship with each other via a 90o phase difference plate (circularly polarized wave generator) on the transmitting side, and then transmitted. On the receiving side, the signal is again converted into two orthogonal linearly polarized waves via a 90° phase difference plate, and then the two polarized waves are separated into separate terminals using a polarization splitter or the like. However, when heterogeneity occurs in the propagation space due to rain, etc., circularly polarized waves become elliptical polarized waves that include anti-rotating polarization components. Rather, the outputs separated by the polarization demultiplexer contain interference waves of the other polarization.

Therefore, the branching circuit on at least one of the transmitting side and the receiving side used in wireless communication using two circularly polarized waves having an anti-rotating relationship with each other has the function of reducing the above-mentioned interference. It is necessary to have As one of the branching circuits that have such a function in the microwave band, the 90o
The first component consists of a retardation plate (circularly polarized wave generator), a 180o retardation plate (polarization plane rotator), a variable phase shifter, a variable attenuator, etc.
There is a branching circuit as shown in the figure.

Note that since the transmitting side branching circuit and the receiving side branching circuit are basically the same due to reversibility, the receiving side branching circuit will be explained here. In Fig. 1, 1 is an antenna, 2 is a circular waveguide that propagates two orthogonal polarized waves, and 3 is a circular waveguide that transmits the phase of one of the two orthogonal polarized waves that propagate inside the circular waveguide 2. 4 is a 90o retarder with a 90o phase front that retards the phase by 90o compared to the other.
1800 retardation plate with 0 retardation and 180o retardation surface;
5 is a polarization splitter, 6 and 7 are branch terminals that respectively couple to the two mutually orthogonal polarized waves in the polarization splitter 5, and 8 is the slow surface of the 90o retardation plate 3 and the 180o retardation plate 4. rotary joint to allow rotation around the tube axis; 9;
10 is a directional coupler, 11 to 18 are directional couplers 9, 1
0 terminal, 19 is a variable phase shifter, 20 is a variable attenuator, 21
is a non-reflection terminator, and 22 and 23 are output terminals. Next, the operation of such a branching circuit during rain will be explained.

During rain, the two signals are in a counter-rotating relationship with each other on the transmitting side.
The signal waves Ea and Eb transmitted as two circularly polarized waves arrive at the antenna 1 as non-orthogonal elliptically polarized waves after passing through Ameshiro.

First, the phase difference between the component in the long axis direction and the component in the short direction perpendicular to this in the bridge circularly polarized wave is 900, so by rotating the slow phase plane of the 90o retardation plate, the phase difference between Ea and Eb is On the other hand, for example, by matching the major or minor axis of Ea, it is possible to make the phase relationship between the most axial component and the minor axis component the same or opposite, and convert the elliptically polarized wave of Ea into a linearly polarized wave. can be converted. Next, the false wavefront converted into linearly polarized wave can be rotated by rotating the 180° phase difference plate, and is coupled only to the branch terminal 7 of the polarization splitter 5, and is coupled to the branch terminal 7 of the polarization splitter 5.
It is possible to avoid binding to .

At this time, Eb generally becomes a camellia circularly polarized wave that is not orthogonal to the linearly polarized wave of Ea, and since Eb is coupled to both branch terminals 6 and 7, Eb is an interference wave along with the signal wave of Ea at branch terminal 6. combined as

However, the Eb interference wave coupled to this branch terminal 7 is
A part of the Eb signal wave coupled to the branch terminal 6 is taken out to the terminal 13 in the directional coupler 9, the variable phase shifter 19 and the variable attenuator 20 are adjusted, and the signal wave is branched through the directional coupler 1. It can be canceled by combining the Eb interference wave coupled to the terminal 7 so that it has an opposite phase and equal amplitude.
Therefore, in the above-mentioned conventional demultiplexing circuit, the slow phase surface of the 900 phase difference plate 3 is made to coincide with the long axis of the elliptically polarized wave of Ea after passing through Ameshiro, and the slow phase surface of the 1800 phase difference plate 4 is set to be a straight line. Ea and Eb are outputted by controlling the variable phase shifter 19 and the variable attenuator 20 so that Ea converted to polarized wave is no longer coupled to the branch terminal 6 and Eb at the output terminal 23 is eliminated. terminals 22 and 23
It is possible to separate the waves without interference. here,
The angle of the long rib of the ellipse of Ea after passing through the rain zone is controlled by the inclination angle of the raindrop of the spheroid and does not vary greatly if the rainfall intensity is strong to a certain extent.

Therefore, the 900 retardation plate 3, which rotates following the angle of the long axis of the ellipse, is not required to rotate rapidly and greatly. However, in the Haruo mode, the Ea incident on the 900 retardation plate 3 has a circular polarization (having a bridge circular polarization rate unique to the transmitting and receiving stations) whose Nagato angle is dominated by the power supply device and antenna on the transmitting side. ), and the angle of this long axis does not necessarily match the angle when the rainfall intensity is strong, and may differ greatly. Therefore, in the above-mentioned conventional branch circuit, in a transient state from a clear sky to a certain degree of rainfall intensity, the angle of the long axis of the bridge circularly polarized wave of Ea is controlled by the power supply device and antenna on the transmitting side. Since the angle suddenly changes from the angle to the angle controlled by the inclination of the raindrop, there is a drawback that the rotation of the 900 retardation plate 3 cannot be sufficiently followed. In order to eliminate these drawbacks, the present invention provides a fixed retardation plate in the circular waveguide 2, and will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention, in which numerals 1, 3 to 23 are the same as in FIG.

A fixed phase difference plate 24 is inserted after the antenna 1 and has a slow phase surface that delays the phase of one of the two polarized waves propagating in the circular waveguide by a certain amount compared to the other.

Next, regarding the effect of this fixed retardation plate 24, the circularly polarized wave at the time of Haruo has a long axis of x as shown by F in FIG.
An example will be explained in which the angle made with the axis is -450 and the wave is elliptically polarized wave rotating in the direction of the arrow.

Here, the X-axis is the direction of the equivalent slow phase surface of the propagation space caused by rain. In FIG. 3, the x component and the Y component of the bridge circularly polarized wave have the same amplitude, but the phase of the Y component lags the x component by more than 900 degrees. This phase lag is expressed by the following equation, where R is the circular polarization coefficient (ratio of the most axis to the shortest axis). ○=22n-1(R)...
[11 Here, in a transient state where the rainfall intensity gradually increases from clear skies, the amount of phase of the equivalent slow surface generated in the X-axis direction due to rain increases, and the phase of the x component of the spear circularly polarized wave Because of the delay, is the phase delay mentioned above? gradually decreases.

At this time, the circular polarization coefficient of the circularly polarized wave decreases at the same long axis angle, and when the angle reaches 900, it becomes a completely circularly polarized wave. Furthermore, when A becomes 900 or less, as shown by A in FIG. 3, the light becomes an elliptically polarized wave whose long axis makes an angle of 450 with respect to the X axis, and the elliptical polarization rate increases. Therefore, in a transitional state from a clear day to a certain degree of rainfall intensity, the angle of the long axis changes rapidly.

However, in the duplexer of the present invention, at least the m-th
A fixed retardation plate 24 having a larger phase amount than the small phase lag in the equation is provided so that its slow phase surface is in the X-axis direction.

Therefore, in clear weather, the bridge circularly polarized wave is
4, the beam is always incident on the 90o retardation plate 3 as a camellia circularly polarized wave such as a bridge circularly polarized wave A. The angle of the most axis of this bridge circularly polarized wave A does not change even when it rains, and the bridge circular polarization rate only increases, so it is
There is no need for the 0o retardation plate to rotate rapidly, and the disadvantage of not being able to sufficiently follow changes due to rainfall is eliminated. Note that although the case where the 90o retardation plate is located closer to the antenna than the 180o retardation plate has been described above, the connection order may be reversed.

In addition, although the case where the demultiplexer circuit is used on the receiving side has been described above, it is also possible to use it on the transmitting side.
This is clear from the reversibility.

Furthermore, although the above description has been made for the case where one of the two non-orthogonal incident ellipses is a linearly polarized wave, it is also possible to
It may be used when controlling a 0 retardation plate or an 1800 retardation plate.

As described above, in the branching circuit according to the present invention, 9
By providing a fixed retardation plate closer to the antenna than the 0o retardation plate and the 1800o retardation plate, the long angle of the incident ellipse to the 90o retardation plate or the 180o retardation plate can be adjusted at an angle both on a sunny day and on rainy days. It is possible to eliminate sudden large changes, and 90o retardation plate and 180o retardation plate
o There is an advantage that interference waves can be canceled out within a rotation range that can be sufficiently tracked by the retardation plate.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional branching circuit, FIG. 2 is a block diagram of a branching circuit according to an embodiment of the present invention, and FIG. 3 illustrates the operating principle of the branching circuit shown in FIG. FIG. In the figure, 3 is a 90oo retardation plate (conversion means), and 4 is a 180mm retardation plate.
o Retardation plate, 5 a polarization splitter, 8. 19 is a variable phase shifter, 20 is a variable attenuator, and 24 is a fixed phase difference plate (fixed phase shifter). In the drawings, the same or corresponding parts are denoted by the same reference numerals. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A fixed phase difference plate that delays the phase of one of two elliptically polarized waves having a counter-rotating relationship with respect to the phase of the other polarized wave by a certain amount, and this fixed phase difference plate. A 90° phase difference plate that delays the phase of one of the two elliptically polarized waves contained in the output of the plate by 90 degrees relative to the phase of the other polarized wave, and a A 180° retardation plate that delays the phase of the other polarized wave by 180°, a polarization splitter that separates both polarizations after these conversions, and a part of the output of one of the polarization splitters. A branching circuit comprising a transmission means that provides modulated attenuation and a variable phase delay, and a coupler that combines the output of this transmission means and the output of the other polarization splitter. 2. The fixed retardation plate is characterized by having a slow phase plane that prevents the polarized wave entering the polarization splitter from becoming circularly polarized with respect to the angle of the equivalent slow plane that occurs in the propagation space of polarized waves due to rain, etc. A branching circuit according to claim 1.