JP3021776B2 - Tracking receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking receiver for generating an angle error signal which is an antenna control signal required for automatically tracking a moving object which radiates radio waves such as an artificial satellite. More particularly, the present invention relates to a tracking receiver that generates an angle error signal from a PSK signal as a communication signal.

[0002]

2. Description of the Related Art As is well known, a conventional antenna automatic tracking system for pointing an antenna to a moving artificial satellite includes:
It utilizes an unmodulated beacon signal transmitted by an artificial satellite.

[0003]

Therefore, conventionally, it is necessary to mount a beacon transmitter in addition to the equipment necessary for the original communication, so that an automatic antenna tracking system is constructed using the PSK signal which is a communication signal. There is a request that the beacon transmitter should be deleted. However, for that purpose, there are the following difficult problems to be solved.

That is, the carrier-to-noise ratio (C / N) of a communication line enabling data transmission by a PSK signal is 5 to 6 d.
Although it is B or more, in the tracking of a moving artificial satellite or the like, it is desired that the capturing operation be started from the stage of rising from the horizon, and that the device be already captured and be in the tracking state at the stage of performing communication. Therefore, in the automatic tracking of the antenna, it is necessary to be able to track even if the intensity of the arriving radio wave, that is, the C / N is as weak as about 0 dB. Since the beacon signal is an unmodulated signal, the band was narrow and tracking was possible even under low C / N.
Since the bandwidth of the PSK signal is wide, the circuit configuration poses a problem. Hereinafter, a specific description will be given.

[0005] The tracking receiver is provided with a sum signal channel receiving section and a difference signal channel receiving section after the IF stage, and the angular error voltage output from the tracking receiver is A of the difference signal channel receiving section.
It is generated by detecting the signal output level of the GC amplifier circuit.
At this time, gain control of the AGC amplifier generally employs a method of detecting an input signal level of a tracking receiver and using it as a control voltage. Then, the C / N of the input signal is 0 dB
When the noise level is reduced to the extent, the noise component is added to the AGC control voltage generated by detecting the input signal level.
There is a problem that the gain of the C amplifier is suppressed, and as a result, the angle error detection sensitivity is reduced.

Also, under low C / N, the input signal of the difference signal channel receiving section contains many noise components,
There is also a problem that the angle error voltage includes not only a voltage due to the angle error but also a voltage due to noise.

An object of the present invention is to provide a tracking receiver capable of generating an angle error signal from a PSK signal without lowering the angle detection sensitivity under low C / N and without changing the angle error voltage due to noise. Is to do.

[0008]

In order to achieve the above object, a tracking receiver according to the present invention has the following configuration. That is, the tracking receiver of the present invention is a tracking receiver that generates an angle error signal as an antenna control signal necessary for automatically tracking the transmitting station from the received PSK signal; The signal channel receiving unit is configured to perform
Means for reproducing a carrier orthogonal to the carrier of the PSK sum signal output from the amplifier;
Means for synchronously detecting the quadrature component of the SK sum signal; means for detecting a noise voltage from the synchronously detected signal; Means for compensating for: the difference signal channel receiving unit comprises:
The PSK difference signal output from the second AGC amplifier and the PSK difference signal;
Means for detecting an angle error voltage from the SK sum signal; and means for subtracting said angle error voltage or al the noise voltage;
It is characterized by having.

[0009]

Next, the operation of the tracking receiver of the present invention configured as described above will be described. In the tracking receiver of the present invention, the sum signal channel receiving section reproduces a carrier orthogonal to the carrier of the PSK sum signal, and the quadrature reproduced carrier reproduces the PS.
The quadrature component of the K sum signal is synchronously detected to detect a noise voltage,
The AGC control voltages of the first AGC amplifier and the second AGC amplifier of the difference signal channel receiver are corrected according to the detected noise voltage. As a result, both AGC amplifiers are controlled at a voltage close to the true AGC control voltage when no noise is added. The difference signal channel receiving unit detects an angle error voltage from the PSK difference signal output from the second AGC amplifier and the PSK sum signal, and subtracts the noise voltage from the detected angle error voltage to determine the tracking error. Generated as receiver output.

As described above, according to the present invention, tracking that can generate an angle error signal from a PSK signal without lowering the angle detection sensitivity under low C / N and without changing the angle error voltage due to noise. There is an effect that a receiver can be provided.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a tracking receiver according to one embodiment of the present invention. FIG. 1 shows a portion of the tracking receiver according to the present invention, that is, a sum signal channel receiving section 27 and a difference signal channel receiving section 28 which are circuits after the IF stage. Therefore, the received PSK signal to be tracked is converted into a PSK sum signal, an AZ (or X-axis) PSK difference signal and an EL (or Y-axis) PSK difference signal by an antenna circuit (not shown),
The reception frequency conversion unit converts the PSK sum signal (IF) into an IF signal, inputs the converted PSK sum signal (IF) to the sum signal channel reception unit 27, and converts the converted PSK difference signal (I
F) is input to the difference signal channel receiving unit 28. In the present embodiment, the difference signal channel receiving unit 28 is constituted by two systems of an AZ (azimuth) channel and an EL (elevation angle) channel, but may be constituted by one of the two systems.

The P signal input to the sum signal channel receiving section 27
The SK sum signal is subjected to unnecessary wave removal processing by the bandpass filter 1 and is subjected to amplification processing by the (first) AGC amplifier 2.
It becomes one of the inputs of the phase detectors 3 and 4, and also becomes the input of the difference signal channel receiver 28 via the phase shifters 23 and 24. The AGC amplifier 2 performs gain control by obtaining an AGC control voltage from the AGC voltage correction circuit 12.

Reference numeral 13 denotes a carrier recovery circuit for recovering a carrier signal of the same phase synchronized with the carrier of the PSK sum signal.
This reproduced carrier signal is directly input to the other input of the phase detector 3 and is also shifted by 90 ° in the π / 2 phase shifter 5 to become a quadrature reproduced carrier signal, which is the other input of the phase detector 4. FIG. 2 shows both input signals PS of these phase detectors.
The relationship between the K signal and the reproduced carrier signal is shown in a vector diagram.

In FIG. 2, (a) is a vector diagram of the PSK sum signal, in which no noise is added (C /
N = ∞). A solid line 41 is a zero-phase vector, and a dotted line 42 is a π-phase vector whose phase is inverted by the modulation data. FIG. 2B is a vector diagram of the reproduced carrier signal. A solid line 43 is a signal vector in phase with the PSK sum signal, and a dotted line 44 is a signal vector orthogonal to the PSK sum signal. Also, FIG.
(C) is a vector diagram when noise is added to the PSK sum signal, where 45 is a noise vector, and 46 is a composite vector of the zero-phase vector 41 and the noise vector 45 of the PSK sum signal. Here, A is the signal amplitude, and n is the effective value of the noise.

Here, it is known that the effective value of the noise component in phase with the carrier and the effective value of the noise component orthogonal to the carrier are both n as the nature of the band-limited noise. Therefore, if the C / N is low and noise is added to the PSK signal,
The composite amplitude in phase with the carrier of the PSK signal is A + n,
The component orthogonal to the carrier of the PSK signal is only noise and its amplitude is n.

Therefore, the phase detector 3 performs synchronous detection using the reproduced carrier signal in phase with the carrier of the PSK sum signal, and detects a signal having an amplitude corresponding to A + n in FIG. 2C. This is subjected to signal removal processing of the IF frequency band and its high frequency component by the low-pass filter 6, and is input to the carrier recovery circuit 13 and the amplitude detector 8.

The amplitude detector 8 detects the amplitude of A + n of the input signal and generates a voltage | A + n | proportional to the amplitude of A + n. This output voltage is smoothed by the low-pass filter 10 and input to the AGC voltage correction circuit 12.

On the other hand, the phase detector 4 performs synchronous detection using a reproduced carrier signal orthogonal to the carrier of the PSK sum signal, and detects a signal having an amplitude corresponding to n in FIG. 2C.
This is processed by the low-pass filter 6 to remove the IF frequency band and its high-frequency components, and becomes a baseband signal.
The signal is input to the carrier recovery circuit 13 and the amplitude detector 9.

The amplitude detector 9 detects the amplitude of n of the input signal and generates a voltage | n | proportional to the amplitude of n. This output voltage is smoothed by the low-pass filter 11 and
The signal is input to the GC voltage correction circuit 12 and is also supplied to the correction voltage generation circuit 14 of the difference signal channel receiving unit 28.

The AGC voltage correction circuit 12 generates a voltage closest to | A | from two voltages | A + n | and | n |. At this time, | A +
When there is a difference between n of n | and | n | output from the low-pass filter 11, the difference is corrected together. That is, the AGC voltage correction circuit 12 can output a voltage signal that is less affected by noise even in a low C / N state in which noise is added to the PSK signal.

The output voltage of the AGC voltage correction circuit 12 is used as an AGC control voltage for the AGC amplifier 2.
The AGC control voltage is supplied to the (second) AGC amplifiers 17 and 18 of the difference signal channel receiving section 28. Since the AGC control voltage is not affected by the noise, the low C / Even in the N state, the gain of these AGC amplifiers is not suppressed by noise. Therefore, when the input signal level is within the allowable operation range, these AGC amplifiers perform the operation of controlling the output signal level to a constant level regardless of the input signal level at a low C / A level.
It can be executed even under N.

Next, the PSK difference signal AZ (EL) input to the difference signal channel receiving section 28 is
At (16), the AGC amplifier 1
7 (18) undergoes amplification processing, and the phase detector 19 (2
0).

The output of the AGC amplifier 2 is supplied to the other input of the phase detector 19 (20) via the phase shifter 23 (24) and the delay line 21 (22). , The phase detector 19 detects the AZ (or X-axis) angle error voltage, and
0 detects the EL (or Y-axis) angle error voltage. In addition,
As another method of detecting the angle error signal, there is a method of performing synchronous detection using, for example, a remodulated wave. The delay line 21
(22) and the phase shifter 23 (24) are provided to match the delay and phase of the envelope of the sum signal with those of the difference signal in order to perform correlation detection.

The low-pass filter 25 (26) outputs the I signal included in the angle error voltage which is the output signal of the phase detector 19 (20).
The F component, its harmonic components and noise are removed. this is,
This is one input of the subtractor 29 (30). Subtractor 29
The other input of (30) is the output of the correction voltage generation circuit 14.

That is, under low C / N, the phase detector 19
A component due to noise is mixed into the angle error voltage, which is the output signal of (20), in the course of the above-described correlation processing. Since the mixed noise component is a DC voltage, it is applied to the low-pass filter 25.
It is impossible to remove by (26). Therefore,
A subtractor 29 (30) and a correction voltage generating circuit 14 are provided;
A noise voltage component included in the angle error voltage is removed using a voltage | n | that is proportional to the noise level generated by the amplitude detector 9.

That is, the correction voltage generation circuit 14 outputs the voltage | n |
A ₁ │n│ + a ₂ │n│ ² + a ₃ │n│ which is a voltage equal to the noise voltage component included in the angle error voltage.
³ + ... is generated. The subtracter 29 (30) subtracts this voltage from the angle error voltage output from the low-pass filter 25 (26).

Thus, under a low C / N, it is possible to suppress the angle error voltage from being changed by noise. The angle error voltage from which the influence of the noise has been removed is applied to the DC amplifier 3
1 (32).

[0028]

As described above, according to the tracking receiver of the present invention, a carrier orthogonal to the carrier of the PSK sum signal is reproduced in the sum signal channel receiving section, and the quadrature reproduced carrier is used to reproduce the carrier of the PSK sum signal. A noise voltage is detected by synchronously detecting the orthogonal component. Then, the first AGC amplifier and the second A of the difference signal channel receiving unit are detected according to the detected noise voltage.
The AGC control voltage of the GC amplifier is corrected so that both the AGC amplifiers are controlled at a voltage close to the true AGC control voltage when no noise is added. 2 The angle error voltage is detected from the PSK difference signal output from the AGC amplifier and the PSK sum signal, and the noise voltage is subtracted from the detected angle error voltage to suppress the influence of noise.
There is an effect that a tracking receiver that can generate an angle error signal from a PSK signal without lowering the angle detection sensitivity under / N and without changing the angle error voltage due to noise is provided.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a tracking receiver according to one embodiment of the present invention.

FIG. 2 is a relational vector diagram of a PSK signal and a reproduced carrier.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 band filter 2 AGC amplifier 3 phase detector 4 phase detector 5 π / 2 phase shifter 6 low-pass filter 7 low-pass filter 8 amplitude detector 9 amplitude detector 10 low-pass filter 11 low-pass filter 12 AGC voltage correction circuit Reference Signs List 13 carrier recovery circuit 14 correction voltage generation circuit 15 band filter 16 band filter 17 AGC amplifier 18 AGC amplifier 19 phase detector 20 phase detector 21 delay line 22 delay line 23 phase shifter 24 phase shifter 25 low-pass filter 26 low-pass Filter 27 Sum signal channel receiving unit 28 Difference signal channel receiving unit 29 Subtractor 30 Subtractor 31 DC amplifier 32 DC amplifier

Claims (1)

(57) [Claims] 1. A tracking receiver for generating an angle error signal as an antenna control signal required for automatically tracking a transmitting station from a received PSK signal; the tracking receiver includes a sum signal channel receiving unit. , 1st AG
Means for reproducing a carrier orthogonal to the carrier of the PSK sum signal output from the C amplifier; means for synchronously detecting the quadrature component of the PSK sum signal by the orthogonal reproduced carrier; means for detecting a noise voltage from the synchronous detection signal. Means for correcting the AGC control voltage of the first AGC amplifier and the second AGC amplifier of the difference signal channel receiving unit according to the detected noise voltage; and wherein the difference signal channel receiving unit outputs the PSK difference output from the second AGC amplifier. Means for detecting an angle error voltage from a signal and the PSK sum signal;
Tracking receiver comprising the; and means subtracting the angular error voltage or al the noise voltage.