JP2022181637A - Angle error detection device - Google Patents

Abstract

To provide an angle error detection device capable of grasping and correcting a change in a phase following passage of a sum signal and a differential signal through a signal path in real time when performing angle error detection of an antenna used for tracking reception.SOLUTION: In an angle error detection device 12 for detecting an angle error of a reception direction of a frequency signal from a tracked object, an angle error detection part 42 detects an angle error on the basis of a value of an imaginary part of a multiplication vector of a vector of a differential signal obtained by performing quadrature demodulation of a sum signal and a differential signal of a frequency signal received at a different position of an antenna, and a conjugated vector of a vector of the sum signal. A correction value acquisition part 44 acquires a correction value for setting a value of a real part to zero by correcting a phase of the differential signal on the basis of a value of the real part of the multiplication vector, and a phase correction part 45 corrects a phase of the differential signal on the basis of the correction value.SELECTED DRAWING: Figure 6

Description

The present invention relates to a technology for detecting angular error of an antenna with respect to a tracked object.

Receiving systems that receive communication signals, which are frequency signals output from tracking targets such as communication satellites and aircraft, are equipped with the There is a system (tracking reception system) that can change the orientation of the antenna so that the reception direction of the communication signal is aligned with the front direction of the antenna.

As a method for detecting the angle error, the amplitude difference between the communication signals received by two openings (first receiving section and second receiving section) arranged in different positions in the antenna is obtained. , a method of obtaining an angle error based on this amplitude difference is known.
In this method, the angle error is obtained using the sum signal A+B and the difference signal AB of the communication signal A received by the first receiving unit and the communication signal B received by the second receiving unit. Calculations are made.

On the other hand, in a tracking reception system, it is not always possible to place the calculator that calculates the angle error near the antenna. may not be.
In this case, the sum signal and the difference signal obtained on the antenna side are supplied to the calculator side via signal paths (sum signal path and difference signal path) including communication cables.

However, if the lengths of these signal paths are not strictly the same, a phase difference is formed between the sum signal and the difference signal, which becomes a factor that hinders accurate calculation of the angular error. In addition, the difference in the degree of deterioration of the communication cable and the difference in temperature of the space in which the communication cable is arranged also cause the phase difference between the sum signal and the difference signal.

Here, Patent Documents 1 and 2 describe each signal path through which a sum signal and a difference signal are transmitted (referred to as "receiving channel" in Patent Document 1 and "system" in Patent Document 2). However, a technique is described in which a pilot signal is supplied by switching from the sum signal or difference signal, and the sum signal or difference signal is corrected based on the result of detecting the phase difference between the pilot signals that have passed through different signal paths. there is
However, these Patent Documents 1 and 2 do not describe a technique of detecting the phase difference caused by each signal path in real time without switching between the sum signal/difference signal and the pilot signal and utilizing it for correction. do not have.

Japanese Patent Publication No. 56-500394 JP 2010-66069 A

The present invention has been made under such circumstances. Provided is an angle error detection device capable of grasping and correcting in real time the change in phase that accompanies passage through a path.

This angle error detection device is an angle error detection device that detects an angle error in a receiving direction of a frequency signal from a tracking target with respect to a front direction of an antenna,
A first receiving section provided in the antenna for receiving the frequency signal modulated by the carrier wave and outputting it as a first received signal, and at a position different from the frequency signal received by the first receiving section. The frequency signal is received as a second received signal, and the sum signal obtained from the first received signal and the second received signal is arranged at a position where the difference signal is out of phase with the phase of the sum signal by 90°. a second receiving unit configured to
a received signal output unit that obtains a sum signal and a difference signal based on the first received signal and the second received signal, and outputs the signals to a sum signal path and a difference signal path, respectively;
The sum signal obtained through the sum signal path and the difference signal obtained through the difference signal path are orthogonally demodulated using the carrier wave, and the sum signal and the difference signal are a demodulator that obtains an in-phase component (I component) and a quadrature component (Q component) for each signal;
When the in-phase component is expressed as a real part on the complex plane and the quadrature component is expressed as an imaginary part as a complex vector, the imaginary vector obtained by multiplying the difference signal vector and the conjugate vector of the sum signal vector is obtained. an angle error detection unit that detects the angle error based on the value of the part;
a correction value obtaining unit that obtains a correction value for correcting the phase of the difference signal and setting the value of the real part to zero based on the value of the real part of the multiplication vector;
and a phase correction unit that corrects the phase of the difference signal based on the correction value corrected by the correction value acquisition unit.

The angular error detection device described above may have the following configuration.
(a) The phase correction section corrects the phase of the difference signal at a position where the difference signal that has passed through the difference signal path is input to the demodulation section.

According to the present invention, when the sum signal and the difference signal used for angular error detection are orthogonally demodulated and displayed as a complex vector, the difference signal before demodulation is feedback-corrected so as to maintain the orthogonal state of these vectors. , the change in phase between the sum signal and the difference signal caused by passing through the signal path can be grasped in real time and corrected.

1 is a configuration diagram of a tracking reception system provided with an angle error detection device; FIG. 1 is a block diagram showing a schematic configuration of an angle error detection device; FIG. FIG. 11 is a block diagram of an angle error detection device according to a comparative embodiment; FIG. 4 is an explanatory diagram relating to a method of obtaining an angle error using a quadrature-demodulated sum signal and a difference signal; FIG. 10 is an explanatory diagram showing the influence of the phase shift between the sum signal and the difference signal on the detection result of the angle error; 1 is a block diagram of an angular error detection device according to an embodiment; FIG. 4 is a configuration diagram of a circuit included in the angle error detection device according to the embodiment; FIG.

FIG. 1 shows a configuration example of a tracking reception system 1 equipped with an angular error detection device according to an embodiment of the present invention.
The tracking reception system 1 includes an antenna 11 that receives a communication signal (frequency signal) output from a tracking target, an antenna driving mechanism 15 that changes the direction of the antenna 11, and a sum signal of the communication signal acquired from the antenna 11. and an angle error detection device 12 for detecting a deviation (angle error) of the reception direction of the communication signal with respect to the front direction of the antenna 11 based on the difference signal; and an antenna driving unit 14 for driving and controlling the antenna driving mechanism 15 based on the driving direction and driving amount determined by the tracking control unit 13 .

FIG. 2 is a block diagram showing the antenna 11 and the angle error detection device 12 included in the tracking reception system 1 described above.
For example, the tracking target 8 shown in FIG. 2 outputs a communication signal with a preset frequency. The communication signal includes a baseband signal modulated by a carrier having the preset frequency.

The antenna 11 includes a first receiving section 2a and a second receiving section 2b whose receiving positions are different from each other. When performing angle measurement in the azimuth direction, the first receiving unit 2a and the second receiving unit 2b are arranged at different positions in the horizontal direction, and when performing angle measurement in the height direction, the first receiving unit 2a , and the second receiver 2b are arranged at different positions in the height direction.

The communication signals A and B received by the first and second receivers 2a and 2b are passed through adders 21 and 22 provided on the side of the antenna 11, for example, to obtain a sum signal A+B and a difference signal A-, respectively. Output as B.
In the example shown in FIG. 2, the case where the sum signal and the difference signal are obtained on the antenna 11 side has been described, but the adders 21 and 22 for obtaining these signals may be provided on the angle error detection device 12 side. good.

FIG. 3 shows a block diagram of an angular error detection device 12a according to a comparison form before applying the present invention. The angular error detection device 12a includes a reception processing unit 3 provided with reception filters 31a and 31b for filtering unnecessary components, variable amplifiers 32a and 32b for amplifying the filtered sum signal and difference signal, and a signal processing unit 3. a block 4; The reception processing unit 3 and the signal processing block 4 are connected by a sum signal path 33a through which the sum signal passes and a difference signal path 33b through which the difference signal passes.
The adders 21 and 22 provided in the antenna 11 and the reception processing section 3 constitute a reception signal output section of this example.

The signal processing block 4 includes an A/D conversion unit 43 that performs A/D conversion of the sum signal and difference signal amplified by the reception processing unit 3, and a demodulation unit 41 that demodulates the digitally converted sum signal and difference signal. and an angle error detector 42 for obtaining an angle error based on the signal level of the difference signal.
Here, the variable amplifiers 32a and 32b provided on the reception processing section 3 side constitute an AGC (automatic gain control section) that operates in combination with an AGC control section 432 provided on the A/D conversion section 43 side. is doing.

Next, referring to FIGS. 4 and 5, an example of a method of detecting an angle error using a sum signal and a difference signal by the angle error detection device 12a having the above configuration, and a comparative example shown in FIG. Problems of the angle error detection device 12a will be described.

FIG. 4A shows the quadrature component (Q component) obtained by quadrature demodulation of the sum signal and difference signal output from the adders 21 and 22 on the real axis (Re axis), and the in-phase component (I component) on the real axis (Re axis). It is the figure which plotted on the imaginary axis (Im) axis, and represented the vector. As shown in FIG. 4(a), the sum signal and the difference signal usually have different signal levels, and the sum signal vector and the difference signal vector may have different lengths.

Further, the signal levels of the sum signal and the difference signal shown in FIG. 4(a) also change according to the angle error (deviation of the reception direction of the communication signal with respect to the front direction of the antenna 11). At this time, in the range where the angle error is small, the ratio of the signal level of the difference signal (Δ) to the sum signal (Σ) has a relationship (θ∝Δ/Σ) that approximately corresponds to the angle error (θ). to detect the angle error.

On the other hand, in a communication facility where the tracking reception system 1 is installed, the sum signal is demodulated by a main demodulation system (not shown), and subsequent processing is performed, so the signal level of the demodulated sum signal is It is required to be constant.

Therefore, in the variable amplifiers 32a and 32b that amplify the sum signal and the difference signal, the variable amplifier 32a on the sum signal side amplifies the sum signal so that the output signal level becomes constant. On the other hand, the variable amplifier 32b on the difference signal side amplifies with the same gain as the variable amplifier 32a on the sum signal side.
As a result, the signal level of the difference signal output from the variable amplifier 32b (the vector length of the difference signal expressed as a complex vector) is standardized by the signal level (constant value) of the sum signal output from the variable amplifier 32a. (Fig. 4(c)).

Here, the first receiving section 2a and the second receiving section 2b are orthogonally demodulated, and the vector of the sum signal represented by the complex vector and the vector of the difference signal are orthogonal to each other, that is, the sum signal and the difference signal. are arranged at positions that are 90° out of phase with each other. Using this orthogonal relationship, as shown in FIG. 4B, by rotating the vector so that the vector of the difference signal is oriented along the imaginary axis, the value of the imaginary part of the vector of the difference signal after calculation is It becomes a value corresponding to "Δ/Σ".

As a method for rotating the vector of the difference signal, the demodulator 41 of this example multiplies the vector of the difference signal by a vector conjugate to the vector of the sum signal (indicated by the dashed line in FIG. 4(a)). perform calculations. By reading the value corresponding to the imaginary part of the multiplication vector obtained as a result of this calculation, the value of "Δ/Σ" corresponding to the angle error can be obtained.

4(a) to 4(c), the phase relationship between the sum signal and the difference signal acquired through the signal path 33a for the sum signal and the signal path 33b for the difference signal is orthogonal. A correct angle error can be obtained when these signals are input to the demodulator 41 while maintaining the state.

On the other hand, as already mentioned, these signal paths 33a, 33b may comprise, for example, communication cables with lengths of tens to hundreds of meters. At this time, if the lengths of both communication cables are not exactly the same, or the degree of deterioration or the temperature of the installation environment is different, the sum signal-difference difference may occur when passing through these signal paths 33a and 33b. A signal phase shift may occur.

FIG. 5(a) shows a state in which the vector of the sum signal and the vector of the difference signal are no longer orthogonal to each other due to the phase shift. In the figure, the vector of the true difference signal (corresponding to the vector of the difference signal shown in FIG. 4A) before passing through the difference signal path 33b is indicated by a broken line.

If the orthogonal relationship between the sum signal vector and the difference signal vector is lost, even if the difference signal vector is rotated by a vector conjugate with the sum signal, the multiplied vector after the calculation will deviate from the imaginary axis direction. . For this reason, the length of the vector cannot be read correctly by simply reading the value of the imaginary part of the multiplication vector, and a deviation (detection error) occurs in the detection result of the angular error.
For convenience of illustration, FIG. 5 illustrates the case where the phase shift occurs in the difference signal and the orthogonal relationship between the sum signal and the difference signal is lost. Also, the same problem occurs when there is a phase shift between both the difference signal and the sum signal.

In order to cope with the problems described above, as shown in FIG. 6, the angle error detection device 12 of the present example has a vector of the difference signal with respect to the vector of the sum signal described with reference to FIGS. A correction value acquisition unit 44 is provided for detecting the magnitude of the deviation of the orthogonal relationship between the two and acquiring a correction value based on the detection result. have the function of

FIG. 7 shows a circuit configuration example of the demodulator 41, the angle error detector 42, and the A/D converter 43. As shown in FIG.
The demodulator 41 in FIG. 7 includes a frequency oscillator 411 that outputs a frequency signal (eg, cosine wave) corresponding to the frequency of the carrier wave, and a frequency signal (eg, sine wave) obtained by advancing the phase of the frequency signal by 90°. and a rotator 412 .

The multiplier 413a multiplies the digitally converted sum signal by the frequency signal from the frequency oscillator 411, which is supplied to the A/D converter 43 via the sum signal path 33a. Then, the I component (I1) is extracted by removing unnecessary components with a low-pass filter (LPF) 414a. Further, the multiplier 413b multiplies the digitally converted sum signal by the frequency signal whose phase is advanced by 90° by the phase rotator 412, and extracts the Q component (Q1) by removing unnecessary components in the LPF 414b. .

Similarly, the multiplier 413c multiplies the frequency signal from the frequency oscillator 411 by the difference signal which is supplied to the A/D converter 43 via the signal path 33b for the difference signal and digitally converted. Then, the I component (I2) is taken out by removing unnecessary components in the LPF 414c. Further, the multiplier 413d multiplies the digitally converted difference signal by the frequency signal whose phase is advanced by 90° in the phase rotator 412, and extracts the Q component (Q2) by removing unnecessary components in the LPF 414d. .

The angle error detection unit 42 uses sum signals I1 and Q1 and difference signals I2 and Q2 to rotate the vector of the difference signal based on the concept described with reference to FIGS. That is, the vector (I2, Q2) of the difference signal expressed as a complex vector is multiplied by the sum signal and the conjugate vector (I1, -Q1), and the imaginary part of the multiplied vector (I1I2+Q1Q2,I1Q2-I2Q1) after the calculation is obtained. 'I1Q2-I2Q1', which is the value of Specifically, the adder 422 outputs the difference value between “I1Q2” obtained by the multiplier 421b and “I2Q1” obtained by the multiplier 421a.

Then, in the coefficient multiplier 423, when the difference value is multiplied by a preset conversion coefficient for converting the difference into an actual angle error, the angle error can be obtained.

As described with reference to FIGS. 5A and 5B, when the orthogonal relationship between the sum signal vector and the difference signal vector is lost, the real part value occurs (FIG. 5(b)). If the angle φ between the multiplication vector and the imaginary axis is sufficiently small, said angle φ is approximately equal to the value of the real part of the multiplication vector.

Therefore, the correction value acquiring unit 44 obtains the real part value "I1I2+Q1Q2" based on the result of multiplication of the vector of the difference signal and the conjugate vector of the sum signal. Specifically, the adder 442 outputs the added value of “I1I2” obtained by the multiplier 441a and “Q1Q2” obtained by the multiplier 441b.

After the digital conversion, the correction value calculator 443 performs the above-described Obtain a correction value to offset the angle φ. For example, the correction value calculator 443 multiplies the value of the real part of the vector of the difference signal by a predetermined coefficient, and inverts the sign of the multiplication result.

After that, the correction value obtained by the correction value calculation unit 443 is input to the phase correction unit 45 arranged before the position where the difference signal is input to the demodulation unit 41 . Based on the correction value obtained from the correction value calculation unit 443, the phase correction unit 45 performs phase correction to delay or advance the phase of the difference signal. Inversion of the sign of the correction value may be performed on the phase correction unit 45 side.

By using the correction value acquiring unit 44 and the phase correcting unit 45 having the above-described configurations, even when there is a phase shift with the sum signal, the demodulating unit 41 and the correction value acquiring unit 44 are used. By performing various calculations, a value corresponding to the phase shift (value of the real part of the multiplication vector described above) can be obtained.

By obtaining a correction value based on this value and using it for feedback correction of the phase of the difference signal, it is possible to reduce the phase shift between the difference signal and the sum signal. As a result, the value of the imaginary part of the multiplication vector obtained by the angle error detection unit 42 can be brought closer to the actual value of "Δ/Σ", and a more accurate angle error can be detected.

Also, the angle φ between the multiplication vector and the imaginary axis shown in FIG. 5(b) is the amount of relative deviation from the state where the vector of the difference signal and the vector of the sum signal are orthogonal to each other. Therefore, even if a phase shift occurs in the course of the sum signal passing through the sum signal signal path 33a, or even if a phase shift occurs in both the sum signal and the difference signal, the difference signal side phase These deviations can be corrected by correcting .

The angle error detection device 12 according to this embodiment has the following effects. When the sum signal and the difference signal used for angle error detection are orthogonally demodulated and displayed as a complex vector, the difference signal before demodulation is feedback-corrected so as to maintain the orthogonal state of these vectors. A change in phase between the sum signal and the difference signal due to passing through can be grasped in real time and corrected.

The correction of the phase of the difference signal using the correction value acquisition unit 44 is not limited to the case of performing the difference signal after digital conversion. For example, the phase of the analog difference signal before digital conversion may be corrected.

Further, the application of the angular error detection device of the present invention is not limited to a tracking reception system for communication. For example, the angular error detection device of the present invention may be provided within a radar system. In this case, the tracking target becomes a detection target, and the frequency signal from the tracking target radiates the frequency signal to the detection target and becomes a reflected signal.

1 tracking reception system 2a, 2b receivers 21, 22 adder 3 reception processor 33a sum signal signal path 33b difference signal signal path 41 demodulator 42 angle error detector 44 correction value acquirer 8 tracking target 11 antenna 12, 12a
Angle error detector

Claims (2)

In an angle error detection device that detects an angle error in a receiving direction of a frequency signal from a tracking target with respect to the front direction of an antenna,
A first receiving section provided in the antenna for receiving the frequency signal modulated by the carrier wave and outputting it as a first received signal, and at a position different from the frequency signal received by the first receiving section. The frequency signal is received as a second received signal, and the sum signal obtained from the first received signal and the second received signal is arranged at a position where the difference signal is out of phase with the phase of the sum signal by 90°. a second receiving unit configured to
a received signal output unit that obtains a sum signal and a difference signal based on the first received signal and the second received signal, and outputs the signals to a sum signal path and a difference signal path, respectively;
The sum signal obtained through the sum signal path and the difference signal obtained through the difference signal path are orthogonally demodulated using the carrier wave, and the sum signal and the difference signal are a demodulator that obtains an in-phase component (I component) and a quadrature component (Q component) for each signal;
When the in-phase component is expressed as a real part on the complex plane and the quadrature component is expressed as an imaginary part as a complex vector, the imaginary vector obtained by multiplying the difference signal vector and the conjugate vector of the sum signal vector is obtained. an angle error detection unit that detects the angle error based on the value of the part;
a correction value obtaining unit that obtains a correction value for correcting the phase of the difference signal and setting the value of the real part to zero based on the value of the real part of the multiplication vector;
and a phase correction unit that corrects the phase of the difference signal based on the correction value corrected by the correction value acquisition unit. 2. The angle according to claim 1, wherein the phase correction section corrects the phase of the difference signal at a position where the difference signal that has passed through the difference signal path is input to the demodulation section. Error detection device.

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