JPH06291503A - Axial ratio compensating circuit - Google Patents

Abstract

PURPOSE:To improve the degree of cross polarized wave discrimination, in the case of receiving simultaneously two orthogonal polarized waves. CONSTITUTION:The circuit 20 is provided with a first input part (a) to which a cross polarized wave signal is inputted from a probe 40V, a second input part (b) to which a signal is inputted from a probe 40H, and a first and a second outputs (c), (d) connected to a circuit of a low noise block converter, and in a first output part (c), a first output signal corresponding to a cross polarized wave component, and a second output signal corresponding to the signal from the probe 40H are generated. In this circuit 20, transmission lines 22-34 are provided extending from a first and a second input parts (a), (b) to a first and a second outputs (c), (d) so that a first and a second output signals become an opposite phase, and also, the impedance of the transmission lines 22-34 is determined in advance so as to be in a state that absolute values of amplitude values of a first output signal and a second output signal are equal to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, in satellite broadcasting and satellite communication, of two polarization components orthogonal to each other,
The present invention relates to a cross polarization compensating circuit for removing cross polarization in which one polarization to be received includes the other polarization component.

[0002]

2. Description of the Related Art For example, in satellite broadcasting and satellite communication, in a vertically polarized wave and a horizontally polarized wave which are orthogonal to each other at the same frequency,
It is common to transmit different information. When receiving such satellite broadcasting or satellite communication, these two orthogonal
The two polarized waves may be simultaneously supplied to the low noise block converter, and the two polarized waves may be frequency-converted into low frequencies.

FIG. 5 shows a portion for inputting two such orthogonal linearly polarized waves to a low noise block converter. For example, a primary reflected by a parabolic reflector and placed at the focal position of the reflector. From the radiator to the waveguide 1
Two orthogonal linearly polarized waves introduced in 0, for example, a vertically polarized wave and a horizontally polarized wave, are received by the probes 12V and 12H arranged so as to be orthogonal to each other. Of course,
As shown in FIG. 6, these probes 12V and 12H are arranged at a position of about λg / 4 (where λg is a wavelength in the waveguide of vertically and horizontally polarized radio waves to be received) from the end of the waveguide 10. ing.

The vertically polarized waves and the horizontally polarized waves received by the probes 12V and 12H are supplied to the first-stage amplifying elements 16H and 16V of the low noise block converter through the microstrip lines 14V and 14H, and then the vertically polarized waves. Is processed by a high frequency amplification circuit for vertical polarization, a frequency conversion circuit and an intermediate frequency amplification circuit, and horizontal polarization is processed by a high frequency amplification circuit for horizontal polarization, a frequency conversion circuit and an intermediate frequency amplification circuit, respectively. The polarized waves and the vertically polarized waves are independently converted into low frequencies and extracted from the low noise block converter. In addition,
18 and 20 are ground, 22H and 22V are microstrip lines, and amplification elements 16H and 16
It is for supplying the output of V.

Alternatively, a high-frequency switching element is provided in the power supply line of the amplifying elements 16H and 16V, and one of the amplifying elements 16H and 16V is operated by these switching elements to select vertical polarization and horizontal polarization. One is supplied to the high frequency amplifier circuit, and thereafter
It is supplied to the frequency conversion circuit and the intermediate frequency amplification circuit, and only one of the horizontally and vertically polarized waves selected is converted to a low frequency and taken out from the low noise block converter.

[0006]

The apparatus as described above has a simple structure, but since no measure is taken to remove the cross polarization component, the cross polarization discrimination degree is the same as that of the probes 12H and 12V. About 10 to 20d depending on performance
Only B can be taken, which is not enough. For reception of only one polarization, the cross polarization discrimination degree can be improved by providing a cross polarization suppression element such as an absorption resistance for absorbing an unnecessary component. Since it is for receiving waves, a cross polarization suppression element cannot be provided. Therefore, the cross polarization component, along with the desired polarization component,
Since the signal is amplified and frequency-converted, there is a problem that the quality of the received satellite signal deteriorates.

[0007]

In order to solve the above-mentioned problems, the present invention provides a circuit having first and second input sections and first and second output sections. . This circuit includes first and second in-phase to the first and second inputs.
The first output signal corresponding to the first input signal, the amplitude of which is the first amplitude value, and the amplitude of which is the second amplitude value. , And a second output signal corresponding to the second input signal. Also, the second
A third output signal corresponding to the first input signal whose amplitude is the third amplitude value and a fourth output signal corresponding to the second input signal whose amplitude is the fourth amplitude value. Generate an output signal of. This circuit is provided with a transmission line from the first and second input parts to the first and second output parts in a state where the first and second output signals are in opposite phase to each other, and has a first amplitude value. The impedance of the transmission line is set so that the absolute values of the first and second amplitude values are equal. The first input signal to the first input section is a cross polarization component generated based on the second input signal to the second input section.

Further, the above circuit can be configured symmetrically when viewed from the first and second input sections and the first and second output sections.

[0009]

According to the present invention, the first output signal is generated at the first output section by the first input signal which is the cross polarization component based on the second input signal. In addition, the second output signal is generated at the first output portion based on the second input signal. The first and second output signals have opposite phases, and the first and second amplitude values, which are the amplitude values, have the same absolute value. Therefore, in the first output section, the added value of the first output signal and the second output signal becomes zero, and the cross polarization component is removed. Further, when the above circuit is configured symmetrically with respect to the first and second input sections and the first and second output sections, the symmetry causes the second input section to generate The cross-polarized component based on the signal supplied to the first input is also removed at the second output.

[0010]

EXAMPLE A cross polarization compensation circuit 20 of this example is shown in FIG.
Shown in. The cross polarization compensation circuit 20 includes a first input section a, a second input section b, a first output section c, and a second output section d.
With transmission lines 22, 24, 26, 2 between them.
8, 30, 32, and 34 are connected in a ladder shape by a microstrip line having a predetermined width.

That is, the transmission line 22 is connected between the first input section a and the first output section c, and the second input section b is connected.
A transmission line 24 is connected between the second output section d and the second output section d. Transmission lines 26 and 28 are connected between the first input section a and the second input section b, and transmission lines 30 and 32 are connected between the first output section c and the second output section d. Are connected. The transmission line 34 connects the connection point e of the transmission lines 26 and 28 and the connection point f of the transmission lines 30 and 32.

These transmission lines 22, 24, 26, 2
8, 30, 32, and 34 all have a length of λg /
4 (λg is the transmission wavelength on the strip line of the vertically and horizontally polarized radio waves to be received).
The impedances of the transmission lines 22 and 24 are both set to Z1, and the transmission lines 26, 28, 30, 32
Has an impedance of Z2, and the transmission line 34 has an impedance of Z3.

Therefore, the cross polarization compensating circuit 20 is configured symmetrically when viewed from the first and second input parts a and b sides and the first and second output parts c and d sides. There is.

When a second input signal B, for example, a power having a value of "1" is supplied to the second input section b of the cross polarization compensation circuit 20, the first output section c mainly receives the following signals. The signals B1 to B4 are generated through the four paths of That is, 1) second input part b-connection point e-first input part a-first output part c,
2) second input part b-second output part d-connection point f-first
Output part c, 3) second input part b-connection point e-connection point f
-First output part c, 4) second input part b-second output part d-connection point f-connection point e-first input part a-first output part c. In this case, the line lengths of 1), 2) and 3) are all (3/4) λg, and the line length of (4) is (5).
/ 4) λg. In addition to these, there are various transmission paths from the second input part b to the first output part c, but in each case, the line length is the same as the above 1) to 4). The length will be an integral multiple of λg.

Further, in the cases 1) to 4), the absolute values | B1 | of the amplitudes of the signals B1 to B4 generated at the first output section c.
Through | B4 |, | B1 | through | B3 | are almost equal because the line lengths are all equal to (3/4) λg.
Since B4 | is longer than (5/4) λg and | B1 | to | B3 |, the power is smaller than that of | B1 | to | B3 |.

FIG. 3 shows waveforms where the phase position b of each part in the cases of 1) to 4) is 0 degree. The output signal Bc generated at the first output section c is a combination of the above B1 to B4, and therefore becomes | B1 | + | B2 | + | B3 |-| B4 |, and its phase is the second Than input signal B (3/4)
It will be λg advanced.

When the second input signal B is supplied to the second input section b of the cross polarization compensating circuit 20, the second output section d mainly passes through the following four paths. The signals B5 to B8 are generated. That is, 5) second input part b-second output part d, 6) second input part b-connection point e-connection point f-second
Output section d, 7) second input section b-connection point e-first input section a-first output section c-connection point f-second output section d,
8) Second input section b-connection point e-connection point f-first output section c-first input section a-connection point e-connection point f-second output section d. In this case, in 5), the line length is λg / 4,
In 6), the line length is (3/4) λg, in 7) the line length is (5/4) λg, and in 8), the line length is (7/4) λg. In addition to these, there are various transmission paths from the second input section b to the second output section d, but in all cases, the line length is the transmission wavelength within the line lengths of 7) to 8) above. The length will be an integral multiple of λg.

Further, in the cases 7) to 8), the absolute values | B5 | of the amplitudes of the signals B5 to B8 generated at the second output section b.
Through | B8 | have different line lengths, | B5 |
|> | B6 |> | B7 |> | B8 |.

FIG. 4 shows waveforms in which the phase position b of each part in the cases 5) to 8) is 0 degree. The output signal Bd generated at the second output section d is a composite of B5 to B8 described above, and therefore becomes | B5 |-| B6 | + | B7 |-| B8 |, and its phase is the second The input signal B is advanced by λg / 4.

When the same signal A as the second input signal B is supplied to the first input section a, the output signal Ac generated at the first output section c and the output signal Ad generated at the second output section d Means that from the symmetry of the circuit 20, | Ac | = | Bd |, | A
d | = | Bc |, and the phase of Ac is λ from the output signal A.
Advancing by g / 4, the phase of Ad is (3 /
4) λg ahead.

Assuming that the vertically polarized wave is the signal A of power 1,
Consider the case in which the horizontal polarized wave is supplied as the signal B of power 1 to the second input section b. Here, it is assumed that the signal A includes 1/100 of the vertically polarized component as a cross polarized component. Due to the cross polarization component of the signal A, the absolute value of the amplitude is | Ac
At | / 100, a cross-polarized signal Aα whose phase is advanced by λg / 4 is generated. In addition, the first output portion c is generated by the signal B.
, The absolute value of the amplitude is | Bc |, and the phase is (3/4) λ
A signal Bα advanced by g is generated.

Here, the transmission line 36 from the signal source of the signal A to the first input portion a and the transmission line 38 from the signal source of the signal B to the second input portion b are both equal in length,
Moreover, if the impedance of both transmission lines 36 and 38 is Z0, the signal A at the first input part a and the signal at the second input part b,
Both B are in phase. Then, from the above-mentioned symmetry of the cross polarization compensation circuit 20, | Ac | = | Bd |. Therefore, if the impedances Z1, Z2, and Z3 of the transmission lines 22 to 34 are selected so that | Bd | / 100 = | Bc |, the absolute value of Aα generated at the first output section c | Ac | / 100 is equal to | Bd | / 100, which is equal to the absolute value | Bc | of Bα occurring at the first output c. The phase of Aα is advanced from point a by λg / 4, and the phase of Bα is advanced from point b by (3/4) λg, which is the opposite phase. Therefore, the first output, which is the sum of Aα and Bα, is output. No cross polarization component is generated in the output signal of the section c.

The signal B supplied to the second input section b causes signals to be generated not only at the signal Bα but also at the second output section d and the first input section a. However, since the signal generated at the second output section d is originally intended to be transmitted, there is no problem.

The signal Bβ generated at the first input portion a reaches the signal source of the signal A via the transmission line 36, is partially reflected here, and returns to the first input portion a again. The amplitude of this is very weak, but when transmitted to the first output c,
Since it is reflected by the signal source of the signal A, it becomes out of phase with Bα and deteriorates the performance of removing cross-polarized waves. When it is necessary to compensate for this deterioration, the transmission lines 22 to 34 are used.
Impedances Z1, Z2 and Z3 of | Bd | / 10
Instead of selecting 0 = | Bc |
Impedances Z1, Z2, Z of the transmission lines 22 to 34 such that | = | Bd | / 100 + | Bβ | / γ
3 may be selected. However, | Bβ | / γ is the absolute value of the amplitude when Bβ is reflected and generated at the first output portion c.

The above description is for the case where a cross polarization component occurs in the first input section a, but the cross polarization compensation circuit 2
Due to the symmetry of 0, even when a cross polarization component is generated in the second input part b, the cross polarization component can be similarly removed.

FIG. 1 shows the cross polarization compensation circuit 20 described above.
1 shows an embodiment implemented in a low noise block converter for receiving vertically polarized waves and horizontally polarized waves, in which a cross polarization compensation circuit 20 is composed of a microstrip line, and its first input part a is The probe 40V for vertical polarization reception is connected via a transmission line 36 constituted by a microstrip line. Similarly,
The second input section b is connected to the probe 40H for receiving horizontal polarization via the microstrip line 38. Both of the probes 40H and 40V are arranged in the waveguide 42 so as to be orthogonal to each other. Of course, both the probes 40H and 40V are the same as the probe 12H shown in FIG.
Like 12 V, it is arranged at a position of λg / 4 from the closed end of the waveguide 42.

First output section c of cross polarization compensation circuit 20
Is input to the first-stage amplification element 46V of the circuit for vertical polarization reception of the low noise block converter via the transmission line 44V having an impedance of Z0 and configured by a microstrip line. Similarly, the second output section d of the cross polarization compensation circuit 20 has an amplification element at the first stage of the circuit for horizontal polarization reception of the low noise block converter via the transmission line 44H having an impedance of Z0 and formed by a microstrip line. It is input to 46H. 48 and 50 are earth.

In the above embodiment, the cross polarization component is 1/1
00, and explained to remove this,
This is for convenience of description, and the magnitude of the cross polarization component can be set according to the antenna (probe) used, and the value to be compensated is also the antenna (probe).
The required value can be selected depending on the performance of.

Further, although the probes 40V and 40H are used as the signal sources in the above embodiment, a resonance element such as a patch may be used. Further, in the above embodiment, the probes 40V and 40H are provided in the common waveguide 42. However, one probe is provided in each of the two waveguides, and the signals from these probes are cross-polarized. Compensation circuit 20
May be supplied to the first input section a and the second input section b.

Further, in the above embodiment, the low noise block converter provided with the circuit for horizontal polarization and the circuit for vertical polarization was used. However, a circuit for both horizontal polarization and vertical polarization is provided for amplification. Switching elements are provided on the power supply lines of the elements 46H and 46V, and by using these, selected ones of the outputs of the first output section c and the second output section d are used for both horizontal polarization and vertical polarization. May be supplied to the circuit.

In the above embodiment, the case of receiving the vertically polarized wave and the horizontally polarized wave has been described, but the cross polarization compensation is also performed when receiving both or one of the right-handed and left-handed circularly polarized waves. The circuit 20 can be used.

[0032]

As described above, according to the present invention, the first output signal based on the first input signal supplied to the first input section and the second output signal supplied to the second input section. The second output signal based on the input signal of
And a transmission line is provided from the second input section to the first and second output sections, and the transmission is performed in a state in which the absolute value of the amplitude value of the first output signal is equal to the absolute value of the amplitude value of the second output signal. Since the impedance of the line is defined, even if the first input signal is a cross polarization component generated based on the second input signal to the second input section, It is possible to prevent generation of cross polarization components. Further, since the above circuits are symmetrically configured when viewed from the first and second input sections and the first and second output sections, the cross-polarized component generated at the second output section is also the same. Can be removed.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a low noise block converter in which a cross polarization compensation circuit according to the present invention is implemented.

FIG. 2 is a plan view of a cross polarization compensation circuit according to the embodiment.

3 is a diagram showing each signal transmitted to a first output section c by a signal applied to a second input section in the circuit of FIG. 2;

4 is a diagram showing each signal transmitted to a second output part d by a signal applied to a second input part in the circuit of FIG. 2;

FIG. 5 is a diagram showing a configuration of a conventional low noise block converter.

6 is a vertical cross-sectional view of a waveguide connected to the low noise block converter of FIG.

[Explanation of symbols]

 a first input section b second input section c first output section d second output section 20 cross polarization compensation circuit 22-34 transmission line

Claims (2)

[Claims] 1. A first and second input section, and a first and second input section.
And an output having a first amplitude value at the first output in response to the supply of the in-phase first and second input signals to the first and second input. , A first output signal corresponding to the first input signal and a second output signal corresponding to the second input signal, the amplitude of which is the second amplitude value,
And at the second output, the amplitude is the third amplitude value, the first
A third output signal corresponding to the input signal and a fourth output signal corresponding to the second input signal, the amplitude of which is the fourth amplitude value, the circuit comprising: When the first and second output signals are in opposite phases to each other, the first and second output signals
A transmission line is provided from the input part to the first and second output parts, and the impedance of the transmission line is determined such that the absolute values of the first amplitude value and the second amplitude value are equal. A cross polarization compensating circuit in which the first input signal of the first input unit is a cross polarization component generated based on the second input signal to the second input unit. 2. The cross-polarization compensating circuit according to claim 1, wherein the cross-polarization is configured symmetrically when viewed from the first and second input parts and the first and second output parts. Compensation circuit.