JPS5810005B2 - antenna feeding circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antenna feeding circuit that shares two orthogonal polarized waves with low noise temperature and high performance demultiplexing characteristics.

In microwave wireless communications that share two orthogonal polarized waves at the same frequency, that is, two orthogonal linear polarized waves or two polarized waves that are antirotating to each other, depending on the state of the propagation space, orthogonality between the two waves may occur. Therefore, a cross-polarization compensation circuit is required to completely separate the two polarized waves in the antenna feeding circuit.

However, since the cross-polarization compensation circuit has a large loss, it is necessary to provide a low-noise amplifier between the antenna and the cross-polarization compensation circuit.

A conventional antenna feeding circuit provided with this type of low-noise amplifier was constructed as shown in FIG.

That is, in FIG. 1, 1 is an antenna, 2 is a polarization converter that can be rotated around the tube axis, 3 is a polarization plane rotator that is rotatable around the tube axis, 4 is a polarization splitter, and 5 is a polarization splitter. 6 is a transmitting wave terminal, and 7 is a receiving wave terminal in the form of a branched rectangular waveguide provided in the polarization splitter 4.

Note that each connection portion of the antenna 1, polarization converter 2, polarization plane rotator 3, and polarization splitter 4 is constructed of a circular waveguide so as to be rotatable around the tube axis.

The operating principle will be explained using FIG.

For convenience of explanation, first, a case will be described in which the antenna 1 receives two circularly polarized waves having a counter-rotating relationship with each other.

The two circularly polarized waves received by the antenna 1 have the electrical characteristics of the two circularly polarized waves at the antenna 1, that is, the elliptical polarization coefficient,
The light is propagated to the polarization converter 2 without changing the mutual relationships such as tilt angle and rotation direction.

As is well known, the polarization converter 2 has a phase difference of 90 degrees with respect to orthogonal polarized waves, so when passing through the polarization converter 2, the two received circularly polarized waves become two orthogonal straight lines. converted into polarized waves.

The polarization planes of these two linearly polarized waves are rotated by a polarization plane rotator 3 so as to be optimal for two orthogonal receiving wave terminals 7, and each polarized wave is sent to two receiving wave terminals by a polarization splitter 4. It is split into 7 waves.

However, depending on the state of the propagation space, the waves received by the antenna 1 are not necessarily two circularly polarized waves, but are generally two elliptically polarized waves whose long axes are not perpendicular to each other.

In this case, even if the polarization converter 2 and the polarization plane rotator 3 are rotated, the two elliptically polarized waves cannot be converted into two orthogonal linearly polarized waves, and the received waves of the polarization splitter 4 cannot be converted into two orthogonal linearly polarized waves. Each component of the two elliptically polarized waves is simultaneously taken out at the terminal 7.

That is, each receiving wave terminal 7 has cross-polarized components.

Therefore, it is necessary to remove this cross-polarization component, and a cross-polarization compensation circuit, although not shown in FIG. 1, is required.

However, since the cross-polarization compensation circuit has a large loss and a high noise temperature, in the antenna feeding circuit shown in FIG. After each noise amplifier 5 is provided and amplified once,
By guiding the received wave to the cross-polarization compensation circuit, a rise in noise temperature is prevented.

However, in such a conventional antenna feeding system circuit configuration, a polarization converter 2 is installed between the antenna 1 and the polarization splitter 4.
Because of the presence of the polarization plane rotator 3 and the polarization plane rotator 3, it is required that their circuit losses be minimized.

Therefore, since the polarization converter 2 and the polarization plane rotator 3 are limited in their tube axis lengths, it has been difficult to obtain broadband and high performance characteristics.

This invention was made to eliminate these drawbacks, and by configuring a polarization demultiplexer and a low-noise amplifier closer to the antenna than the polarization converter and polarization plane rotator, the noise temperature can be reduced. This makes it possible to obtain high-performance demultiplexing characteristics with low oscillation.

This invention will be explained in detail below. FIG. 2 shows one embodiment of the present invention, and numerals 1 to 7 indicate the same parts as in FIG. 1.

8 is a polarization splitter for the reception frequency band, 9 is a rectangular waveguide, 10 is a polarization combiner having the same electrical characteristics as the reception frequency band electrical characteristics of the polarization splitter 4, and 11 is the square waveguide. This is a branch waveguide consisting of a wave tube 9 and a low noise amplifier 5.

Note that the two low-noise amplifiers 5 have the same electrical characteristics as in the conventional case, and the electrical characteristics of the two branch waveguides 11 consisting of the low-noise amplifier 5 and the rectangular waveguide 9 are as follows. designed to be the same.

Now, if we consider the case where two arbitrary elliptically polarized waves having a counter-rotating relationship are received by the antenna 1, the two received elliptically polarized waves are sent to the polarization splitter 4 while maintaining the mutual relationship of their electrical characteristics. reach.

The two received elliptically polarized waves are divided into two orthogonal components by a polarization demultiplexer 4, each amplified by a low noise amplifier 5 having the same electrical characteristics, and then a polarization combiner 10 having the above-mentioned characteristics. is synthesized with

However, after passing through the polarization combiner 10, the two elliptically polarized waves received by the antenna 1 are amplified, but the electrical relationship between the two elliptically polarized waves is different from that of the antenna 1. The two elliptical polarizations have the same relationship as the mutual relationship between the two polarizations.

This means that the polarization splitter 4 and the polarization combiner 10 have the same electrical characteristics in the reception frequency band, the two branch waveguides 11 have the same electrical characteristics, and excluding the low noise amplifier 5, This can be easily understood because the circuit is reversible.

Therefore, in the antenna feed circuit according to the present invention as shown in FIG. 2, after being amplified by the low noise amplifier 5, Although not shown, since a cross-polarization compensation circuit is connected, the polarization converter 2 and polarization plane rotator 3 are different from the conventional example.
The circuit loss does not become a problem, the degree of freedom in designing the polarization converter 2 and the polarization plane rotator 3 increases, and a broadband and high-performance antenna feeding circuit can be realized.

In addition, in the above embodiment, when transferring the wave received by the antenna 1 to a circuit dedicated to the received wave, a polarization demultiplexer 4 and a polarization combiner 10 having two orthogonal branch waveguides 11 are used. However, the number of branch waveguides 11 is not limited to two; for example, a polarization splitter 4 and a polarization combiner 10 using four branch waveguides orthogonal to each other may be used.

As explained above, this invention places a low-noise amplifier that amplifies the received waves at the position closest to the antenna.
The loss of the various circuits required to separate two orthogonal waves does not become a problem, and the effect is that low noise and wideband electrical characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of a conventional antenna feeding circuit.
FIG. 2 is a perspective view showing an embodiment of the present invention. In the figure, 1 is an antenna, 2 is a polarization converter, 3 is a polarization plane rotator, 4 is a polarization splitter, 5 is a low noise amplifier, 6 is a transmitting wave terminal, 7 is a receiving wave terminal, and 8 is a receiving frequency 9 is a rectangular waveguide, 10 is a polarization combiner, and 11 is a branching waveguide. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1 In an antenna feeding circuit for a communication system that uses two polarized waves that are orthogonal to each other in the reception frequency band, after receiving them with an antenna, convert them into linearly polarized waves with a side wave converter, and then split the waves with a polarization splitter. , the received dual polarized waves are transmitted between the antenna and the received polarized wave converter through a circular waveguide section through which the received dual polarized waves propagate while maintaining the electrical characteristics of the dual polarized waves in the antenna. Two or more branching waveguides are provided to split the waves, and after amplifying the two received polarized waves in each branching waveguide, the electrical correlation between the two received side waves is determined between the two received side waves in the antenna. What is claimed is: 1. An antenna feeding circuit comprising: low-noise amplifiers having the same electrical characteristics that amplify while maintaining the electrical relationship between the antennas; and a polarization synthesizer that combines the outputs of these low-noise amplifiers.