Angle Error Detection Device

Abstract

To provide an angle error detection device capable of more accurately detecting an angle error of an antenna used for tracking reception.SOLUTION: In an angle error detection device 12a, a first automatic gain control part 32a amplifies a sum signal of first and second reception signals to a predetermined signal level when detecting an angle error of a reception direction of frequency signals by using first and second reception signals obtained by receiving frequency signals from a tracked object at different places of an antenna 11, and a second automatic gain control part 32b amplifies a differential signal by a common gain. An angle error detection part 12 detects an angle error on the basis of the amplified differential signal, and a correction part 42 corrects deviation of the angle error following a change corresponding to the gain in a C / N ratio as a ratio of signal power of a differential signal relative to noise power included in a frequency component outputted from the second automatic gain control part 32b.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Some receiving facilities that receive communication signals, which are frequency signals output from tracking targets such as flying objects, can change the orientation of the antenna so that the receiving direction of the communication signal is aligned with the front direction of the antenna based on the results of detecting the deviation (angular error) of the receiving direction of the communication signal relative to the front direction of the antenna (tracking receiving system).

[0003] A known method for detecting angle errors is the monopulse angle measurement method, which determines the angle error based on the signal level (amplitude) of the communication signal received at each of two openings (first receiving unit, second receiving unit) located at different positions within the antenna. In this monopulse angle measurement method, a calculation is performed to determine the angle error using the sum signal A+B of communication signal A received by the first receiving unit and communication signal B received by the second receiving unit, and the difference signal AB.

[0004] On the other hand, the signal level received by the antenna changes depending on the magnitude of the angle error, weather conditions, etc. For this reason, the sum signal and difference signal are amplified using an automatic gain controller (AGC) before being used to detect the angle error.

[0005] However, because the frequency components received by the antenna contain noise, when the sum signal or difference signal is amplified, the noise is also amplified along with the signal. As a result, it becomes difficult to accurately amplify the signal levels of the amplified sum signal or difference signal to the target value, and there is a risk that the correct angle error will not be detected.

[0006] Patent Documents 1 and 2 describe a radar device, a monopulse radar, that uses a sum signal or a difference signal obtained from signals received from a target or object to determine the direction in which a signal is received. However, Patent Documents 1 and 2 do not mention at all the influence that noise has on the detection result of the angle error when amplifying the sum signal and difference signal, or how to deal with this. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 56-500394: Claims 1 and 8, Column 3, line 12 to Column 4, line 15, Figure 1 [Patent Document 2] JP 2010-66069 A: Claim 1, paragraphs 0013 to 0015 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 can more accurately detect the angle error of an antenna used for tracking reception. [Means for solving the problem]

[0009] The angular error detection device according to the present invention detects an angular error in the receiving direction of a frequency signal from a tracking target relative to a front direction of the antenna, based on a first received signal received by a first receiving section of the antenna and a second received signal received by a second receiving section that is located at a different receiving position within the antenna from the first receiving section, the angular error detection device comprising: A sum signal obtained from the first received signal and the second received signal is amplified to a preset signal level. and output to the detector a first automatic gain control unit; a differential signal obtained from the first received signal and the second received signal is amplified by a gain common to the first automatic gain control unit; and output to the detection unita second automatic gain control unit; amplified by the common gain in the second automatic gain control section relative to the signal level (Σ) of the sum signal Difference Signal Ratio (Δ / Σ) of signal levels (Δ) an angle error detection unit that detects the angle error based on When the angular error has a deviation that changes according to a correspondence relationship between the common gain and a C / N ratio of a difference signal, which is a ratio of signal power of the difference signal to noise power included in the frequency component output from the second automatic gain control unit, the correspondence relationship between the common gain and the C / N ratio of the difference signal is considered to be the same as the correspondence relationship between the common gain and the C / N ratio of the sum signal, and the C / N ratio of the sum signal is calculated from the common gain when the difference signal from which the angular error is detected is obtained; (i) C / N ratio of the sum signal and the amount of correction of the angle error, or (ii) a difference between a reference C / N ratio previously determined based on the common gain at which the predetermined signal level is obtained and the C / N ratio of the sum signal, and multiplying this difference by a proportional coefficient to obtain the amount of correction of the angle error. a correction unit that corrects the deviation of the angle error based on The common gain is determined based on the sum signal before being input to the detection unit. It is characterized by:

[0010] The above-described angle error detection device may have the following configuration. (a) a bandpass filter is provided downstream of the first and second automatic gain control units and has a passband width narrower than the frequency bandwidth of the frequency components output from the first and second automatic gain control units, and the correction unit uses a result of adding together a correspondence relationship between the common gain and the C / N ratio of the sum signal and a correspondence relationship between a ratio of signal levels before and after the amplified sum signal passes through the bandpass filter and the C / N ratio of the sum signal to calculate the C / N ratio of the sum signal from the common gain when the difference signal that detects the angle error is obtained, The amount of correction for the angle error obtained using the method (i) or (ii) and correcting the deviation of the angle error based on the above. [Effects of the Invention]

[0011] According to the present invention, the influence of noise power output from an automatic gain controller (AGC) on angle error detection is reduced by correcting the deviation of the angle error using the gain of the AGC, which has a correspondence relationship with the C / N ratio of the signal, thereby making it possible to detect angle errors more accurately with the influence of noise suppressed. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a configuration diagram of a tracking and receiving system including an angle error detection device according to an embodiment. [Figure 2] FIG. 1 is a schematic block diagram showing an example of the configuration of an angle error detection device. [Figure 3] The sum signal and the difference signal are expressed as complex vectors. [Figure 4] FIG. 10 is an explanatory diagram showing the relationship between the normalized difference signal level and the angle error. [Figure 5] FIG. 2 is a first explanatory diagram relating to amplification of a signal level by AGC. [Figure 6] FIG. 2 is a second explanatory diagram relating to the amplification of a signal level by AGC. [Figure 7] 1 is a block diagram of an angle error detection device according to a first embodiment. [Figure 8] 10 is an explanatory diagram showing the C / N ratio-AGC gain characteristics of the sum signal after amplification. FIG. [Figure 9] FIG. 10 is a third explanatory diagram relating to the amplification of a signal level by AGC. [Figure 10] FIG. 10 is a block diagram of an angle error detection device according to a second embodiment. [Figure 11] 10A and 10B are explanatory diagrams relating to changes in signal level before and after passing through a digital filter. [Figure 12] 10 is an explanatory diagram showing the characteristics of the C / N ratio of the amplified sum signal - the AGC gain and the sum of the signal level ratio before and after the digital filter. FIG. [Figure 13] FIG. 10 is an explanatory diagram showing the relationship between the C / N ratio and the detection error of the angle error in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] FIG. 1 shows an example of the configuration of a tracking and receiving system 1 equipped with an angle error detecting device according to an embodiment of the present invention. The tracking and receiving 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 the deviation (angle error: θ) of the receiving direction of the communication signal relative to the front direction of the antenna 11 based on the sum signal and difference signal of the communication signal (received 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 shows an example of the configuration of the angle error detection device 12 according to the embodiment. For example, the tracked target 8 shown in Figure 2 outputs a communication signal in a predetermined frequency range, which includes a baseband signal modulated by a carrier wave having a frequency within the frequency range. The antenna 11 includes a first receiving unit 2a and a second receiving unit 2b, which 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.

[0015] The communication signals A (first received signal) and B (second received signal) received by these first and second receiving units 2a and 2b are output as a sum signal A+B and a difference signal AB, respectively, via adding units 21 and 22 provided, for example, on the antenna 11 side. In the example shown in FIG. 2, the case where the sum signal and 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.

[0016] The angle error detection device 12 includes a reception processing unit 3 provided with reception filters 31a and 31b, which are bandpass filters that remove unnecessary components, and variable amplifiers 32a and 32b that amplify the sum and difference signals that have passed through the reception filters 31a and 31b, and a signal processing block 4 provided with a detection unit 41 that demodulates communication signals and detects angle errors.

[0017] Variable amplifiers 32a and 32b constitute an AGC (automatic gain control unit) that operates in combination with AGC control unit 432, which will be described later. Variable amplifier 32a and AGC control unit 432 correspond to a first automatic gain control unit, and variable amplifier 32b and AGC control unit 432 correspond to a second automatic gain control unit. Before describing the specific configuration of the angle error detection device 12 of this embodiment, an example of a method for detecting an angle error using a sum signal and a difference signal, and the effect of amplifying these signals using AGC on the detection result of the angle error will be described with reference to FIGS. 3 to 6.

[0018] 3 is a vector diagram in which the quadrature component (Q component) obtained by quadrature detection of the sum signal and difference signal output from 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. 3, the sum signal and difference signal usually have different signal levels (the sum signal vector and difference signal vector in Fig. 3 have different lengths).

[0019] The signal levels of the sum signal and difference signal shown in Figure 3 change depending on the angle error. 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) roughly corresponds to the angle error (θ), and this relationship is used to detect the angle error (θ ≒ Δ / Σ).

[0020] 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.

[0021] Therefore, among variable amplifiers 32a and 32b that amplify the sum signal and difference signal, variable amplifier 32a on the sum signal side amplifies the sum signal so that the output signal level is constant. On the other hand, variable amplifier 32b on the difference signal side amplifies the sum signal with the same gain as variable amplifier 32a on the sum signal side. As a result, the signal level of the difference signal output from variable amplifier 32b becomes a value (a value corresponding to "Δ / Σ") normalized by the signal level (constant value) of the sum signal output from variable amplifier 32a (FIG. 4).

[0022] On the other hand, the signal amplification by the variable amplifiers 32a and 32b has the following characteristics. 5(a) and (b) show a schematic diagram of the change in signal level before and after amplification in a strong electric field where the signal level is relatively high compared to the noise level.

[0023] As explained with reference to FIG. 2, the receiving filters 31a and 31b are provided in front of the variable amplifiers 32a and 32b, and therefore the pass bandwidth W of the receiving filters 31a and 31b is set to each of the variable amplifiers 32a and 32b. a The frequency components corresponding to are input. These frequency components include the sum signal / difference signal (hereinafter simply referred to as "signal S") as well as noise N (Fig. 5(a)).

[0024] Here, for example, if the AGC control level (output level) set in the variable amplifiers 32a and 32b is L A In this case, the variable amplifiers 32a and 32b have the above-mentioned bandwidth W a The average level of the frequency component is L A The signal S and noise N are amplified so that

[0025] To explain this graphically, as shown in Figure 5(b), the control level L A The area of ​​the signal level part higher than the control level L (the area of ​​the solid hatched area) and the area where the signal S or noise N is higher than the control level L A The signal S and noise N are amplified so that the area of ​​the part that does not reach the target (the area of ​​the region hatched with dashed lines) is approximately the same. As a result, the signal level of the signal S becomes L1.

[0026] In contrast, in Fig. 6(a) and (b), the noise level is the same as in Fig. 5(a), but the level of the signal S before amplification is at the control level L A 10 shows the state before and after amplification in a weak electric field, which is smaller than the As in the case of FIG. 5(b), the bandwidth W a The average level of the frequency component is L A When the signal S and noise N are amplified so that the signal level of the signal S is amplified to L2, the bandwidth W including the noise N is a As a result, the signal level (L2) after amplification in a weak electric field is smaller than the signal level (L1) after amplification in a strong electric field (L2 <L1)。

[0027] In this way, the signal level of the difference signal amplified by the variable amplifier 32b changes depending on the electric field state at the time of reception, which may cause an error in the detection result of the angle error. Therefore, the angular error detection device 12 according to this embodiment has a function to correct the above-mentioned angular error that occurs due to differences in electric field conditions. Below, the configuration of the angular error detection device 12, including the angular error correction function, will be described with reference to Figures 7 and 8.

[0028] To explain the configuration of the subsequent stages of the reception processing unit 3 already explained, the angle error detection device 12 is equipped with an A / D conversion unit 43 that performs A / D conversion of the sum signal and difference signal amplified by variable amplifiers 32a, 32b, a detection unit 41 that demodulates the digitally converted sum signal to obtain a demodulated signal and determines the angle error based on the signal level of the difference signal, and a correction unit 42 that corrects the angle error determined by the detection unit 41.

[0029] A / D conversion unit 43 includes A / D converters 431a and 431b that perform A / D conversion on the sum signal and difference signal amplified by variable amplifiers 32a and 32b, and digital filters 433a and 433b that are bandpass filters that have a passband width narrower than the frequency bandwidth of the frequency components contained in the sum signal and difference signal converted into digital signals and that remove unnecessary frequency components.

[0030] AGC control unit 432 detects the signal level of the amplified sum signal (sum signal level) and outputs a control voltage that adjusts the gain of variable amplifier 32a so that the signal level of the sum signal output from variable amplifier 32a approaches a target signal level. AGC control unit 432 outputs the same control voltage to variable amplifier 32a on the sum signal side as to variable amplifier 32b on the difference signal side. With this configuration, a difference signal having a signal level normalized with respect to the signal level of the sum signal (the target signal level of the sum signal set in AGC control unit 432) is output from variable amplifier 32b.

[0031] The detector 41 demodulates the digitally converted sum signal and outputs the resulting demodulated signal to a downstream communication signal processor. Regarding the detection of the angle error, based on the relationship between the signal level of the difference signal (difference signal level) and the angle error explained with reference to FIG. 4, for example, the angle error (angle error amount and direction) is calculated from the signal level of the digitally converted difference signal and the rotation angle of the difference signal vector obtained by quadrature detection of the difference signal.

[0032] On the other hand, as explained using FIGS. 5(b) and 6(b), the signal level of the amplified difference signal may change depending on the electric field state at the time of reception. Therefore, the angle error detection device 12 of this example corrects the angle error obtained by the detection unit 41 by taking advantage of the correspondence between the gain (AGC gain) of the variable amplifiers 32a and 32b, which is adjusted to keep the signal level of the sum signal constant when the noise level received by the antenna 11 is approximately constant, and the C / N ratio, which indicates the ratio of the signal power to the noise power of the sum signal.

[0033] Fig. 8 shows an example of the correspondence relationship (C / N ratio-AGC gain characteristics) between the C / N ratio of the sum signal and the AGC gain (average level before amplification / average level after amplification). When variable amplifiers 32a and 32b having a common configuration are used, the C / N ratio-AGC gain characteristics of the difference signal will also be the same as those shown in Fig. 8. Therefore, Fig. 8 also corresponds to the relationship between the C / N ratio of the difference signal and the AGC gain.

[0034] The AGC gain is controlled by the control voltage output from the AGC control unit 432 to the variable amplifiers 32a and 32b, so if this control voltage is used in the correction unit 42, the amount of correction for the angle error can be determined using the characteristics in Fig. 8. The correction unit 42 corrects the angle error based on the above characteristics.

[0035] For example, the correction unit 42 has a correction table that associates the C / N ratio specified according to the characteristics in Fig. 8 with the amount of angle error. The C / N ratio is associated with the control voltage acquired from the AGC control unit 432, and based on the control voltage, a correction value is read from the correction table to correct the angle error determined by the detection unit 41. The method for calculating the amount of correction for the angle error is not limited to the above example. For example, the AGC gain at which the actual signal level of the amplified sum signal (for example, L1 in FIG. 5B) matches the target signal level may be used as a reference, and a difference between the reference C / N ratio and the C / N ratio specified by the AGC gain (control voltage) obtained from the AGC control unit 432 may be calculated, and this difference may be multiplied by a proportional coefficient to obtain the amount of correction for the angle error, which may then be added to the angle error calculated by the detection unit 41.

[0036] According to the angle error detection device 12 of this embodiment, the deviation of the angle error is corrected using the AGC gain, which has a correspondence relationship with the C / N ratio of the sum signal or difference signal relative to the noise power output from the variable amplifiers 32 a, 32 b that constitute the AGC. This makes it possible to reduce deviations in the angle error identification results that occur due to differences in the electric field state when receiving a communication signal.

[0037] Next, the configuration of an angular error detection device 12a, which is a further improvement over the angular error detection device 12 according to the first embodiment, will be described with reference to FIG. 10, components common to the angular error detection device 12 described with reference to FIG. 7 are denoted by the same reference numerals as those shown in FIG.

[0038] As shown in Fig. 8, the C / N ratio-AGC gain characteristic of the sum signal (or difference signal) becomes saturated as the C / N ratio approaches zero. Therefore, if the correction amount is calculated based on this characteristic, a slight change in the AGC gain can result in a large change in the angle error correction amount, making it difficult to achieve more accurate correction.

[0039] The above-mentioned phenomenon is caused by the difficulty of sufficiently increasing the effective gain when focusing on the signal (e.g., sum signal) S before and after amplification in the presence of a weak electric field, as shown in Figures 6(a) and 6(b) and newly in Figures 9(a) and 9(b).

[0040] Therefore, in the angle error detection device 12a according to the second embodiment shown in FIG. 10, the correction amount is calculated using the AGC gain (control voltage) acquired from the AGC control unit 432, as well as the average level ratio of the sum signal and noise in the frequency band input to the digital filter 433a and the frequency band output from the digital filter 433a.

[0041] The bandwidth W of the frequency components input to the digital filter 433a a (FIG. 11(a)), after being processed by the digital filter 433a, the bandwidth W b becomes narrower (Fig. 11(b)). As a result, the influence of the noise level becomes relatively small, and the average level before processing by the digital filter 433a (control level L A the average level after treatment, L A ' has a larger value. In the area where the C / N ratio is close to zero, the average level after processing L A' is closer to the signal level of the actual signal (sum signal in this example) S.

[0042] Furthermore, it was found that there is a correspondence relationship shown in FIG. 12(b) between the C / N ratio of the sum signal and the ratio of the levels before and after processing by the digital filter 433a. Here, the level ratio before and after the digital filter 433a is calculated by the average level of the frequency components output from the digital filter 433a (L in FIG. 11(b)). A 11(a) for the average level of the frequency components input to the digital filter 433a (L A ) ratio (L A / L A ').

[0043] According to the correspondence relationship between the C / N ratio and the level ratio before and after the digital filter 433a (C / N ratio-level ratio characteristics before and after the filter) shown in FIG. 12(b), the sensitivity of the level ratio to the C / N ratio is high (the slope is steep) in the region where the C / N ratio is close to zero. Therefore, in the region where the C / N ratio is close to zero, accurate correction is possible by determining the amount of correction for the angle error based on this level ratio.

[0044] On the other hand, the level ratio before and after digital filter 433a tends to saturate as the C / N ratio increases, making it difficult to use it to correct angle errors in areas with a large C / N ratio.

[0045] To summarize the features confirmed above, the C / N ratio-AGC gain characteristics confirmed using Figure 8 (transcribed in Figure 12(a)) can be said to be more suitable for determining the amount of correction for angle error in areas where the C / N ratio is large. Furthermore, the C / N ratio vs. pre- and post-filter level ratio characteristics confirmed using FIG. 12(b) can be said to be more suitable for correcting angle errors in the region where the C / N ratio is near zero.

[0046] Therefore, the angle error detection device 12a according to the second embodiment calculates the amount of correction for the angle error by using the sum (FIG. 12(c)) of the C / N ratio-AGC gain characteristic (FIG. 12(a)) and the C / N ratio-level ratio characteristic before and after the filter (FIG. 12(b)).

[0047] 10, the calculation unit 44 provided in the angle error detection device 12a receives the control voltages of the A / D converters 431a and 431b from the AGC control unit 432 and calculates the AGC gain value. a , W b The level ratio is calculated based on the average levels of the frequency components in the frequency domain and the sum of these values ​​is output to the correction unit 42. The calculation unit 44 also constitutes a part of the correction unit of this embodiment.

[0048] 12(c), and the sum of the level ratios before and after the digital filter 433a ("AGC gain + level ratio"), the correction unit 42 calculates the sum based on the control voltage acquired from the AGC control unit 432 and the level ratio acquired from the calculation unit 44, reads out a correction value corresponding to the sum from the correction table, and corrects the angle error determined by the detection unit 41. As another example, the sum value at which the actual signal level of the amplified sum signal (for example, L1 in FIG. 5(b)) coincides with the target signal level may be used as a reference, and the difference between the reference C / N ratio and the C / N ratio determined by the "AGC gain + level ratio" may be calculated, and this difference may be multiplied by a proportional coefficient to obtain the amount of correction for the angle error, which may then be added to the angle error calculated by the detection unit 41.

[0049] According to the angle error detecting device 12a according to the second embodiment described with reference to FIGS. 10 to 12, it is possible to correct angle errors with higher accuracy over a wide range of signal levels. [Example]

[0050] (experiment) Using the angle error detection devices 12 and 12a according to the first and second embodiments, the difference (detection error [°]) between the detected angle error and the actual angle error when the electric field state changes was determined. A. Experimental Conditions Example 1 A communication signal was input via antenna 11 so that the C / N ratio of the sum signal was -10, -5, 0, 5, 10, 20, or 30 dB, and the angle error was detected by angle error detection device 12 according to the first embodiment described with reference to Fig. 7, and the detection error from the actual angle error was calculated. The detection error value was found by calculating the root mean square (RMS) of the detection error over a predetermined period for each C / N ratio. Example 2 An experiment similar to that of Example 1 was carried out, except that the angular error was determined using the angular error detection device 12a according to the second embodiment described with reference to FIG.

[0051] B. Simulation Results The results of Examples 1 and 2 are shown in Figure 13. The horizontal axis of Figure 13 represents the C / N ratio of the sum signal, and the vertical axis represents the detection error. The results of Example 1 are shown by the dashed dotted line, and the results of Example 2 are shown by the solid line.

[0052] According to the results shown in FIG. 13, in both the angle error detection devices 12 and 12a according to the first and second embodiments, the detection error was less than 1° in the range where the C / N ratio was 0 dB or more. In particular, in the angle error detection device 12a according to the second embodiment, which utilizes both the characteristics of the AGC gain relative to the C / N ratio and the level ratio before and after the digital filter 433a (FIG. 12(c)), a 5 dB improvement in sensitivity was observed in the C / N ratio at a point where the angle error was 1°. [Explanation of symbols]

[0053] 11 Antenna 12, 12a Angle error detection device 2a First receiving unit 2b Second receiver 32a, 32b Variable Amplifier 41 Detector 42 Correction unit 432 AGC control section 433a, 433b Digital Filter 44 Arithmetic section 8 Tracking target

Claims

1. An angular error detection device detects an angular error of a receiving direction of a frequency signal from a tracking target with respect to a front direction of the antenna, based on a first received signal received by a first receiving unit of the antenna and a second received signal received by a second receiving unit that is located at a different receiving position within the antenna from the first receiving unit, a first automatic gain control unit that amplifies a sum signal obtained from the first received signal and the second received signal to a preset signal level and outputs the amplified sum signal to a detection unit; a second automatic gain control unit that amplifies a difference signal obtained from the first received signal and the second received signal by a gain common to that of the first automatic gain control unit and outputs the amplified difference signal to the detection unit; an angle error detection unit that detects the angle error based on a ratio (Δ / Σ) of a signal level (Δ) of a difference signal to a signal level (Σ) of a sum signal amplified by the common gain in the second automatic gain control unit; and (ii) a correction unit that, when the angular error has a deviation that changes in accordance with a corresponding relationship between the common gain and a C / N ratio of a difference signal, which is a ratio of signal power of the difference signal to noise power included in the frequency components output from the second automatic gain control unit, determines the C / N ratio of the sum signal from the common gain when the difference signal from which the angular error is detected is obtained, by regarding the corresponding relationship between the common gain and the C / N ratio as being common to the corresponding relationship between the common gain and the C / N ratio of the sum signal, and corrects the deviation of the angular error based on the correction amount of the angular error obtained by multiplying the difference value by a proportional coefficient, The angle error detection device according to claim 1, wherein the common gain is determined based on the sum signal before being input to the detection unit.

2. a bandpass filter provided downstream of the first and second automatic gain control units and having a passband width narrower than the frequency bandwidth of the frequency components output from the first and second automatic gain control units; 2. The angular error detection device according to claim 1, wherein the correction unit uses a result of adding together a correspondence relationship between the common gain and the C / N ratio of the sum signal and a correspondence relationship between a ratio of signal levels before and after the amplified sum signal passes through the band-pass filter and the C / N ratio of the sum signal to calculate the C / N ratio of the sum signal from the common gain when the difference signal from which the angular error is detected is obtained, and corrects a deviation of the angular error based on the amount of correction for the angular error obtained using method (i) or (ii).

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