JPS5810001B2 - Branching circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a branching circuit that compensates for deterioration in cross-polarization discrimination due to rain or the like.

In wireless communication that uses two orthogonal polarized waves at the same frequency, cross-polarized wave components are generated due to anisotropy in the propagation space due to rain, etc., so that the degree of cross-polarized wave discrimination between the two polarized waves deteriorates.

An example of a conventional branching circuit for compensating for this deterioration in cross-polarization discrimination is a branching circuit constructed of a waveguide as shown in FIG.

This branching circuit will be briefly explained below. In FIG. 1, 1 is a circular waveguide that guides the radio waves incident on the horn of the antenna and constitutes a part of the polarization splitter, 2 is the tube axis, and 3 and 4 are the circular waveguides in the circular waveguide 1. Branch waveguides that couple to two orthogonal polarized waves, 5 and 6 are the branch waveguides 3
, 4 is a rectangular waveguide-shaped magic T for dividing the coupled radio waves into two equal parts, 7 and 8 are waveguide-shaped variable phase shifters, 9°1
0 is a waveguide-shaped variable attenuator, 11.12 is a rectangular waveguide-shaped magic T for combining two radio waves, 13, 14
15, 16, 17, 18 are the output terminals for taking out radio waves with cross polarization discrimination compensated, and 15, 16, 17, 18 are the magic T5, 6, 1
This is a waveguide type matching terminator for terminating the unused ends of 1 and 12.

Furthermore, in the figure, all lines connecting each element are coupling lines of waveguides.

Next, the operation will be explained.

Here, to simplify the explanation, it is assumed that the radio waves coupled to the branch waveguides 3 and 4 enter the H branches of the magic Ts 5 and 6 and are divided into two equal parts with the same phase.

It is also assumed that the output terminals 13 and 14 are also connected to the H branches of the magic T11 and T12.

Now, of the two orthogonal polarized waves on a clear day when cross-polarized components do not occur, let A be the polarized wave that couples to the branch waveguide 3, and let B be the polarized wave that couples to the branch waveguide 4. The main polarization component of polarization A and the cross polarization component of polarization B are coupled to the branch waveguide 3 .

When these components are expressed by complex amplitudes Ac and Bx, respectively, the complex amplitude E'1 of the electric field E1 of the branch waveguide 3 is given by the following equation.

B'1=Ac+Bx・・・・・・・・・・・・・・・
...(1) Also, if the outgoing wave component of polarized wave B and the cross-polarized wave component of polarized wave A that are coupled to branch waveguide 4 during a similar rain are expressed by complex amplitudes Bc and Ax, respectively, Branch waveguide 4
The complex amplitude E'2 of the electric field E2 is given by the following equation.

E'2=Bc0Ax・・・・・・・・・・・・・・・
(2) When the electric fields E1 and R2 containing cross-polarized components are incident on the magic T5, 6, respectively, the phase amount of the variable phase shifters 7, 8 is changed to θ1. θ2
, the electric field attenuation ratios of variable attenuators 9 and 10 are R1 and R, respectively.
g, the complex amplitudes E'3 and E'4 of the electric fields E3 and R4 taken out from the output terminals 13 and 14 are expressed by the following equations.

Therefore, the electric field attenuation ratio R1jR2 and the phase amount θ1θ
2 is adjusted to satisfy the following equation, the complex amplitudes E'3 and B/4 of the electric field become only components of polarized waves B and A, respectively, and do not include cross-polarized components.

Ax+AcR1eJθ1=O・・・・・・・・・・・・
......(5) Bx+BcR2eJθ2=O...
・・・・・・・・・・・・・・・(6) In this way, the circuit shown in FIG. 2 branch waveguides
Therefore, the polarization splitter composed of the circular waveguide 1 and the branch waveguides 3 and 4 has an asymmetric structure with respect to the tube axis 2 of the circular waveguide 1, and each The disadvantage is that a large number of magic Ts 5, 6, 11 and 12 and their associated matching terminators 15 to 18 are required.

This invention was made to eliminate these drawbacks, and consists of four branch waveguides attached to the wall of a circular waveguide at intervals of 90 degrees in the circumferential direction to construct a polarization splitter. , the Magic T and the matching terminator attached to it are each reduced in half.

This invention will be explained in detail below.

FIG. 2 shows an embodiment of the present invention, in which 3 is a first branch waveguide, 4 is a second branch waveguide, 19 is a third branch waveguide, and 20 is a fourth branch waveguide. This is a waveguide, and other symbols indicate the same parts as in FIG.

Of these four branch waveguides, the third and fourth branch waveguides 19 and 20 have the same structure as the first and second branch waveguides 3 and 4, respectively. 2
The branch waveguides 3 and 4 are provided at positions that form an angle of 180° in the circumferential direction of the circular waveguide 1, and are installed at an angle of 90° in the circumferential direction of the circular waveguide 1 as a whole. It is being

Further, terminals of the first branch waveguide 3 and the second branch waveguide 4 that are not coupled to each other are connected to the magic T11, and a variable phase filter is provided between the first branch waveguide 3 and the magic T11. 7 and variable attenuator 9 are connected in sequence.

Further, the terminals of the third branch waveguide 19 and the fourth branch waveguide 20 that are not coupled to each other are connected to the magic T12, and a variable phase shifter is provided between the fourth branch waveguide 20 and the magic T12. 8 and variable attenuator 10 are connected in sequence.

Furthermore, matching terminators 17 and 1B for termination are connected to one end of the magic Tll and 12, respectively, thereby forming a branching circuit of the present invention.

In the branching circuit of the present invention, during rain, the complex amplitude Ac of the main polarization component of polarization A and the complex amplitude Bx of the cross polarization component of polarization B are different between the first branch waveguide 3 and the third branch waveguide 3. Branch waveguide 19
It is divided into two equal parts and combined.

Therefore, the electric field E of the first branch waveguide 3 and the third branch waveguide 19, and the complex amplitudes B/1 and E'5 of R5 are expressed by the following equations.

Similarly, one complex amplitude Bc of the main polarization component of the polarization B and the complex amplitude Ax of the cross polarization component of the polarization A are different from each other in the second branch waveguide 4.
is divided into two equal parts and coupled to the fourth branch waveguide 20, so the complex amplitudes E'2 and E'6 of the electric fields of the second branch waveguide 4 and the fourth branch waveguide 20 are The following formula % formula % The phase amount of the variable phase shifters 7 and 8 is set to θ1. θ2, and the electric field attenuation ratio of the variable attenuators 9 and 10 is R1>R2, then the complex amplitudes E'3 and E'4 of the electric fields E3 and R4 taken out from the output terminals 13 and 14 are expressed by equations (3) and It is expressed by equation (4) and completely matches the case of the conventional branching circuit.

Therefore, it is clear that this branching circuit can compensate for cross-polarization discrimination in exactly the same manner as the conventional branching circuit.

In the branching circuit of the present invention, as is clear from FIG. Since these first to fourth branch waveguides 3, 4,
The polarization splitter composed of 19 and 20 and the circular waveguide 1 has a symmetrical structure with respect to the tube axis 2, and is easy to handle.

Further, the branching circuit of the present invention requires only two magic tees and matching terminators attached thereto, whereas the conventional branching circuit requires four magic tees and matching terminators, thereby simplifying the structure.

In addition, in the above explanation, the first branch waveguide 3 and the third branch waveguide
The branch waveguide 19, the second branch waveguide 4, and the fourth branch waveguide 20 are each coupled in phase with the electric field in the circular waveguide 1, and the output terminals 13 and 14 are respectively connected to the magic Ill.
, 12, but the coupling is in reverse phase, and the output terminals 13 and 14 are connected to the E of magic T11 and 12, respectively.
May be connected to a branch.

Further, the circular waveguide 1 may be a square waveguide.

As explained above, in the branching circuit according to the present invention, four branching waveguides are provided at intervals of 90° in the circumferential direction of the circular waveguide. By coupling the electric fields in the waveguide, the structure of the polarization splitter can be made symmetrical with respect to the tube axis of the circular waveguide.

Furthermore, compared to conventional branching circuits, there is an advantage that the required number of magic tees and matching terminators attached thereto can be halved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional branching circuit, and FIG. 2 is a block diagram of a branching circuit of the present invention. In the figure, 1 is a circular waveguide, 3 is a first branch waveguide, 4 is a second branch waveguide, 19 is a third branch waveguide, and 20 is a fourth branch waveguide.
, 7 and 8 are variable phase shifters, 9 and 10 are variable attenuators, 11 and 12 are magic tees, 13 and 14 are output terminals, and 17 and 18 are matching terminators. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. 1st, 2nd, 2nd, 3rd, 4th, 4th, etc. are provided in the circumferential direction at angular intervals of 90 degrees on the tube wall of a waveguide constituting a part of a polarization splitter. A first waveguide-shaped magic in which two terminals that are not coupled to each other are connected to third and fourth branch waveguides, and the first branch waveguide and the second branch waveguide. T, a waveguide-type variable phase shifter and a waveguide-type variable attenuator sequentially connected between the first branch waveguide and the first waveguide-type magic T; A second branched waveguide in which two terminals that are not coupled to each other are connected to the third branched waveguide and the fourth branched waveguide.
a waveguide-shaped magic T, a waveguide-shaped variable phase shifter, and a waveguide-shaped variable attenuator connected in sequence between the fourth branch waveguide and the second magic T; and two matching terminators that respectively terminate one end of the first and second magic tees.