Angle error detection device

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

[Technical field]

[0001] The present invention relates to a technique for detecting an angle error of an antenna relative to a tracking target. [Background technology]

[0002] Among receiving systems that receive communication signals, which are frequency signals output from tracked targets such as communication satellites and aircraft, there are some that can change the orientation of the antenna so that the receiving direction of the communication signal aligns with the front direction of the antenna based on the detected deviation (angular error) of the receiving direction of the communication signal relative to the front direction of the antenna (tracking receiving systems).

[0003] A known method for detecting angle errors involves calculating the amplitude difference between communication signals received at two different openings (a first receiving unit and a second receiving unit) located within the antenna, and then calculating the angle error based on this amplitude difference. In this method, a calculation is performed to obtain an angle error using a sum signal A+B of a communication signal A received by a first receiving unit and a communication signal B received by a second receiving unit, and a difference signal AB.

[0004] On the other hand, in a tracking reception system, it is not always possible to place a computer that calculates the angle error in the vicinity of the antenna. For example, there are cases where the antenna and the computer must be placed tens to hundreds of meters apart. In this case, the sum signal and difference signal obtained on the antenna side are supplied to the computer side via a signal path (a signal path for the sum signal and a signal path for the difference signal) including a communication cable or the like.

[0005] However, if the lengths of these signal paths are not exactly the same, a phase difference will be generated between the sum signal and the difference signal, which will prevent accurate calculation of the angle error. In addition, differences in the degree of deterioration of the communication cables and differences in the temperature of the space in which the communication cables are placed will also cause a phase difference to be generated between the sum signal and the difference signal.

[0006] Here, Patent Documents 1 and 2 describe a technology in which a pilot signal is supplied in place of the sum signal or difference signal for each signal path (referred to as a "receiving channel" in Patent Document 1 and as a "system" in Patent Document 2) along which the sum signal or difference signal is transmitted, and the sum signal or difference signal is corrected based on the results of detecting the phase difference between pilot signals that have passed through different signal paths. However, Patent Documents 1 and 2 do not disclose a technique for detecting the phase difference caused by each signal path in real time and using it for correction without switching between the sum signal / difference signal and the pilot signal. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 56-500394 [Patent Document 2] JP 2010-66069 A Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made under these circumstances, and provides an angle error detection device that is capable of grasping and correcting in real time the phase change that occurs when a sum signal and a difference signal pass through a signal path (a signal path for a sum signal, a signal path for a difference signal) when detecting an angle error in an antenna used for tracking reception. [Means for solving the problem]

[0009] The present angle error detection device detects an angle error in a receiving direction of a frequency signal from a tracking target relative to a front direction of an antenna, a first receiving unit provided on the antenna, receiving the frequency signal modulated by a carrier wave and outputting it as a first receiving signal; and a second receiving unit receiving the frequency signal as a second receiving signal at a position different from the position of the frequency signal received by the first receiving unit, the second receiving unit being disposed at a position where a sum signal and a difference signal obtained from the first receiving signal and the second receiving signal are out of phase with each other by 90°; a reception signal output unit that obtains a sum signal and a difference signal based on the first reception signal and the second reception signal, and outputs the sum signal and difference signal to a signal path for the sum signal and a signal path for the difference signal, respectively; a demodulation unit that performs quadrature demodulation using the carrier wave on the sum signal obtained via the sum signal signal path and the difference signal obtained via the difference signal signal path, and acquires an in-phase component (I component) and a quadrature component (Q component) for each of the sum signal and difference signal; an angular error detection unit that detects the angular error based on the value of the imaginary part of a multiplication vector obtained by multiplying the vector of the difference signal by a conjugate vector of the vector of the sum signal when the in-phase component is expressed as a complex vector with the real part on a complex plane and the quadrature component being expressed as an imaginary part; a correction value acquisition unit that acquires a correction value for correcting the phase of the difference signal based on a value of the real part of the multiplication vector to make the value of the real part zero; The image forming apparatus further includes a phase correction unit that corrects the phase of the difference signal based on the correction value obtained by the correction value acquisition unit.

[0010] The above-mentioned angle error detection device may have the following configuration. (a) The phase correction unit corrects the phase of the difference signal that has passed through the difference signal signal path at a position where the difference signal is input to the demodulation unit. Effect of the Invention

[0011] According to the present invention, when the sum signal and difference signal used for angle error detection are orthogonally demodulated and displayed as complex vectors, the difference signal before demodulation is feedback corrected so that these vectors maintain an orthogonal state. This makes it possible to grasp and correct in real time any change in the phase between the sum signal and the difference signal caused by passing through a signal path. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a configuration diagram of a tracking and receiving system equipped with an angle error detection device. [Diagram 2] 1 is a block diagram showing a schematic configuration of an angle error detection device; [Diagram 3] FIG. 11 is a block diagram of an angle error detecting device according to a comparative example. [Figure 4] 10 is an explanatory diagram relating to a technique for calculating an angle error using a quadrature demodulated sum signal and difference signal. FIG. [Diagram 5] 5 is an explanatory diagram showing the effect of a phase shift between the sum signal and the difference signal on the detection result of the angle error. FIG. [Figure 6] 1 is a block diagram of an angle error detection device according to an embodiment. [Figure 7] FIG. 2 is a diagram showing the configuration of a circuit included in the angle error detection device according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] FIG. 1 shows an example of the configuration of a tracking and receiving system 1 equipped with an angle 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 target to be tracked, an antenna driving mechanism 15 that changes the orientation of the antenna 11, an angle error detection device 12 that detects a deviation (angle error) in the receiving direction of the communication signal relative to the front direction of the antenna 11 based on a sum signal and a difference signal of the communication signal acquired from the antenna 11, a tracking control unit 13 that determines the driving direction and driving amount of the antenna 11 based on the angle error detected by the angle error detection device 12, and an antenna driving unit 14 that controls the driving of the antenna driving mechanism 15 based on the driving direction and driving amount determined by the tracking control unit 13.

[0014] FIG. 2 is a block diagram showing the antenna 11 and the angle error detection device 12 included in the above-mentioned tracking and receiving system 1. For example, the tracked target 8 shown in Fig. 2 outputs a communication signal of a preset frequency. This communication signal includes a baseband signal modulated by a carrier wave having the preset frequency.

[0015] The antenna 11 includes a first receiving unit 2a and a second receiving unit 2b that are located at different receiving positions. When measuring an angle in the azimuth direction, the first receiving unit 2a and the second receiving unit 2b are located at different positions in the horizontal direction, and when measuring an angle in the height direction, the first receiving unit 2a and the second receiving unit 2b are located at different positions in the height direction.

[0016] The communication signals A and B received by the first and second receiving sections 2a and 2b are output as a sum signal A+B and a difference signal AB, respectively, via adders 21 and 22 provided on the antenna 11 side, for example. 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 that obtain these signals may be provided on the angle error detection device 12 side.

[0017] 3 is a block diagram of an angle error detection device 12a according to a comparative embodiment before the application of the present invention. The angle error detection device 12a comprises a reception processing section 3 provided with reception filters 31a, 31b that filter out unnecessary components and variable amplifiers 32a, 32b that amplify the filtered sum signal and difference signal, and a signal processing block 4. The reception processing section 3 and the signal processing block 4 are connected by a sum signal signal path 33a through which the sum signal passes, and a difference signal signal path 33b through which the difference signal passes. The adders 21 and 22 provided in the antenna 11 and the reception processing unit 3 constitute a reception signal output unit of this example.

[0018] The signal processing block 4 includes an A / D conversion unit 43 that performs A / D conversion on the sum signal and difference signal amplified by the reception processing unit 3, a demodulation unit 41 that demodulates the digitally converted sum signal and difference signal, and an angle error detection unit 42 that determines the angle error based on the signal level of the difference signal. Here, the above-mentioned variable amplifiers 32a and 32b provided on the reception processing unit 3 side constitute an AGC (automatic gain control unit) that operates in combination with an AGC control unit 432 provided on the A / D conversion unit 43 side.

[0019] Next, with reference to FIGS. 4 and 5, an example of a technique for detecting an angular error using the sum signal and the difference signal by using the angular error detection device 12a having the above-mentioned configuration, as well as problems with the angular error detection device 12a of the comparative example shown in FIG. 3 will be described.

[0020] 4(a) is a vector diagram in which the quadrature component (Q component) obtained by quadrature demodulation of the sum signal and difference signal output from the adders 21 and 22 is plotted on the real axis (Re axis) and the in-phase component (I component) is plotted on the imaginary axis (Im axis). As shown in FIG. 4(a), the sum signal and the difference signal usually have different signal levels, and the lengths of the sum signal vector and the difference signal vector may be different.

[0021] 4(a) also change according to the angle error (the deviation of the receiving direction of the communication signal from the front direction of antenna 11). In this case, in a 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 roughly corresponds to the angle error (θ), and this is used to detect the angle error.

[0022] On the other hand, in communication facilities where the tracking reception system 1 is installed, the sum signal is demodulated in a main demodulation system (not shown) and then processed in subsequent stages, so the signal level of the demodulated sum signal is required to be constant.

[0023] 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 is constant, while 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 variable amplifier 32b (the length of the vector of the difference signal expressed as a complex vector) becomes a value (a value corresponding to "Δ / Σ") normalized by the signal level (a constant value) of the sum signal output from variable amplifier 32a (Figure 4(c)).

[0024] Moreover, the first receiving unit 2a and the second receiving unit 2b are disposed in positions where the vector of the sum signal and the vector of the difference signal, which are orthogonally demodulated and expressed as complex vectors, are in an orthogonal relationship, that is, the sum signal and the difference signal are out of phase with each other by 90°. By utilizing this orthogonal relationship and rotating the vector of the difference signal so that it faces the imaginary axis direction as shown in Fig. 4(b), the value of the imaginary part of the vector of the difference signal after calculation becomes a value corresponding to "Δ / Σ".

[0025] As a method for rotating the vector of the difference signal, the demodulation unit 41 of this embodiment performs an operation of multiplying the vector of the difference signal by a vector conjugate with the vector of the sum signal (shown by a dashed line in FIG. 4(a)). By reading the value corresponding to the imaginary part of the multiplied vector obtained as a result of this operation, the value of "Δ / Σ" corresponding to the angle error can be obtained.

[0026] The method described above using Figures 4(a) to (c) can obtain a correct angle error when the sum signal and difference signal acquired via the sum signal signal path 33a and the difference signal signal path 33b are input to demodulation unit 41 while maintaining the orthogonal phase relationship between these signals.

[0027] On the other hand, as described above, these signal paths 33a, 33b may include communication cables having lengths of, for example, several tens to several hundreds of meters. In this case, if the lengths of both communication cables are not strictly the same, or if the degree of deterioration or the temperature of the installation environment differs, a phase shift may occur between the sum signal and the difference signal when passing through these signal paths 33a, 33b.

[0028] 5(a) shows a state in which the sum signal vector and the difference signal vector are no longer orthogonal to each other due to the phase shift. In the figure, the true difference signal vector (corresponding to the difference signal vector shown in FIG. 4(a)) before passing through the difference signal signal path 33b is shown by a dashed line.

[0029] 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 to the sum signal, the multiplied vector after the operation will deviate from the imaginary axis direction. Therefore, simply reading the value of the imaginary part of the multiplied vector will not allow the correct vector length to be read, resulting in a deviation (detection error) in the detection result of the angle error. For ease of illustration, FIG. 5 illustrates a case in which a phase shift occurs in the difference signal, destroying the orthogonal relationship between the sum signal and the difference signal. However, the same problem can occur if a phase shift occurs in the sum signal, or if a phase shift occurs in both the difference signal and the sum signal.

[0030] In order to address the issues described above, as shown in FIG. 6, the angle error detection device 12 of this example is provided with a correction value acquisition unit 44 that detects the magnitude of deviation in the orthogonal relationship between the difference signal vector and the sum signal vector described using FIGS. 5(a) and 5(b) and acquires a correction value based on the detection result, and has a function of correcting the phase of the difference signal input to the demodulation unit 41 based on this correction value.

[0031] FIG. 7 shows an example of the circuit configuration of the demodulation unit 41, the angle error detection unit 42, and the A / D conversion unit 43. The demodulation unit 41 in FIG. 7 includes a frequency oscillator 411 that outputs a frequency signal (e.g., a cosine wave) corresponding to the frequency of the carrier wave, and a phase rotator 412 that obtains a frequency signal (e.g., a sine wave) with the phase of the frequency signal advanced by 90°.

[0032] Multiplier 413a multiplies the sum signal, which has been supplied to A / D conversion unit 43 via sum signal path 33a and has been digitally converted, by the frequency signal from frequency oscillation unit 411. Then, low pass filter (LPF) 414a removes unnecessary components to extract the I component (I1). Multiplier 413b multiplies the digitally converted sum signal by a frequency signal whose phase has been advanced by 90° by phase rotator 412, and removes unnecessary components by LPF 414b to extract the Q component (Q1).

[0033] Similarly, multiplier 413c multiplies the difference signal, which has been supplied to A / D conversion unit 43 via difference signal signal path 33b and has been digitally converted, with the frequency signal from frequency oscillation unit 411. Then, LPF 414c removes unnecessary components to extract the I component (I2). Multiplier 413d multiplies the digitally converted difference signal with a frequency signal whose phase has been advanced by 90° by phase rotator 412, and removes unnecessary components with LPF 414d to extract the Q component (Q2).

[0034] The angle error detection unit 42 rotates the vector of the difference signal using I1, Q1 of the sum signal and I2, Q2 of the difference signal based on the concept explained with reference to Fig. 4(a) and (b). That is, the vector (I2, Q2) of the difference signal expressed as a complex vector is multiplied by the vector (I1, -Q1) conjugate with the sum signal, and obtains "I1Q2-I2Q1", which is the value of the imaginary part of the multiplied vector (I1I2+Q1Q2, I1Q2-I2Q1) after the calculation. Specifically, the difference value between "I1Q2" obtained by the multiplier 421b and "I2Q1" obtained by the multiplier 421a is output from the adder 422.

[0035] Then, in coefficient multiplier 423, the difference value is multiplied by a preset conversion coefficient to convert it into an actual angle error, thereby obtaining an angle error, which is the amount of deviation of the receiving direction of the communication signal relative to the front direction of antenna 11.

[0036] As explained with reference to Figures 5(a) and (b), if the orthogonal relationship between the sum signal vector and the difference signal vector is lost, a real part value is generated in the multiplication vector after the operation (Figure 5(b)). If the angle φ between the multiplication vector and the imaginary axis is sufficiently small, the angle φ is approximately equal to the real part value of the multiplication vector.

[0037] Therefore, the correction value acquisition unit 44 obtains the real part value "I1I2+Q1Q2" based on the multiplication result of the vector of the difference signal and the vector conjugate to the sum signal. Specifically, the sum of "I1I2" obtained by the multiplier 441a and "Q1Q2" obtained by the multiplier 441b is output from the adder 442.

[0038] After digital conversion, the correction value calculation unit 443 obtains a correction value for offsetting the angle φ so that the difference signal before being input to the demodulation unit 41 maintains a state where it is orthogonal to the sum signal before being input to the demodulation unit 41. For example, the correction value calculation unit 443 multiplies the value of the real part of the vector of the difference signal by a predetermined coefficient and inverts the positive or negative sign of the multiplication result.

[0039] Thereafter, the correction value acquired by the correction value calculation unit 443 is input to the phase correction unit 45 disposed before the position where the difference signal is input to the demodulation unit 41. The phase correction unit 45 performs phase correction to delay or advance the phase of the difference signal based on the correction value acquired from the correction value calculation unit 443. Note that the sign of the correction value may be inverted on the phase correction unit 45 side.

[0040] By using the correction value acquisition unit 44 and phase correction unit 45 having the above-mentioned configuration, even if a phase shift occurs with the sum signal, a value corresponding to the phase shift (the value of the real part of the multiplication vector described above) can be obtained by performing various calculations using the demodulation unit 41 and the correction value acquisition unit 44.

[0041] Then, a correction value is obtained based on this value and used for feedback correction of the phase of the difference signal, thereby making it possible to reduce the phase shift with the sum signal. As a result, the value of the imaginary part of the multiplication vector obtained by the angle error detection unit 42 approaches the actual "Δ / Σ" value, making it possible to detect a more accurate angle error.

[0042] 5(b) is the relative deviation from the state in which the difference signal vector and the sum signal vector are orthogonal. Therefore, even if a phase shift occurs when the sum signal passes through sum signal path 33a, or if a phase shift occurs in both the sum signal and the difference signal, the deviation can be corrected by correcting the phase of the difference signal.

[0043] The angle error detecting device 12 according to this embodiment has the following advantages: When the sum signal and difference signal used for angle error detection are orthogonally demodulated and displayed as complex vectors, the difference signal before demodulation is feedback corrected so that these vectors remain orthogonal, so that changes in the phase between the sum signal and the difference signal caused by passing through the signal paths 33a, 33b can be grasped and corrected in real time.

[0044] The correction of the phase of the difference signal using the correction value acquisition unit 44 is not limited to the case where it is performed on the difference signal after digital conversion. For example, the phase of the analog difference signal before digital conversion may be corrected.

[0045] Furthermore, the application of the angle error detection device of the present invention is not limited to a tracking and receiving system for communication. For example, the angle error detection device of the present invention may be installed in a radar system. In this case, the tracking target is a detection target, and a frequency signal from the tracking target is irradiated to the detection target and becomes a reflected signal. [Explanation of symbols]

[0046] 1. Tracking and receiving system 2a, 2b Receiver 21, 22 Addition section 3 Receiving Processing Section 33a Signal path for sum signal 33b Signal path for difference signal 41 Demodulation section 42 Angle error detection unit 44 Correction value acquisition section 8 Tracking Target 11 Antenna 12, 12a Angle error detection device

Claims

1. An angle error detection device for detecting an angle error of a receiving direction of a frequency signal from a tracking target relative to a front direction of an antenna, a first receiving section provided on the antenna, receiving the frequency signal modulated by a carrier wave and outputting it as a first receiving signal; and a second receiving section, which receives the frequency signal as a second receiving signal at a position different from the position of the frequency signal received by the first receiving section, and is disposed at a position where a sum signal and a difference signal obtained from the first receiving signal and the second receiving signal are out of phase with each other by 90°; a reception signal output unit that obtains a sum signal and a difference signal based on the first reception signal and the second reception signal, and outputs the sum signal and difference signal to a signal path for the sum signal and a signal path for the difference signal, respectively; a demodulation unit that performs quadrature demodulation using the carrier wave on the sum signal obtained via the sum signal signal path and the difference signal obtained via the difference signal signal path, and acquires an in-phase component (I component) and a quadrature component (Q component) for each of the sum signal and difference signal; an angular error detection unit that detects the angular error based on the value of the imaginary part of a multiplication vector obtained by multiplying the vector of the difference signal by a conjugate vector of the vector of the sum signal when the in-phase component is expressed as a complex vector with the real part on a complex plane and the quadrature component being expressed as an imaginary part; a correction value acquisition unit that acquires a correction value for correcting the phase of the difference signal based on a value of the real part of the multiplication vector to make the value of the real part zero; and a phase correction unit that corrects the phase of the difference signal based on the correction value obtained by the correction value acquisition unit.

2. 2. The angle error detection device according to claim 1, wherein the phase correction section corrects the phase of the difference signal that has passed through the difference signal signal path at a position where the difference signal is input to the demodulation section.

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