JP2007033326A - Angle measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an angle measuring device capable of measuring the direction where a target exists within a beam width even with a radar device using wavelet transformation. <P>SOLUTION: The angle measuring device comprises a target detector 20 for detecting the target based on a wavelet expansion coefficient obtained by applying wavelet transformation to an input signal, and an angle measuring section 30 for performing mono-pulse angle measurement by transmitting and receiving a mono-pulse beam to/from a beam position at which the target is detected by the target detector 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an angle measuring device that is applied to a radar device that performs search, tracking, and the like, and measures an angle of a target, and more particularly to an angle measuring technique in the case of detecting a target using discrete wavelet transform.

  In the recent signal processing field, wavelet transform processing is often used instead of Fourier transform or discrete cosine transform (DCT) processing. Details of the wavelet transform processing are described in Non-Patent Document 1, for example. Since the wavelet transform can efficiently process a signal whose intensity is locally distributed, it is applied in various fields such as image processing, audio signal processing, and video signal processing in a radar apparatus.

  In a radar apparatus, a video signal based on a reflected echo from a target is Fourier-transformed to obtain a spectrum on the frequency axis, and this is filtered to extract a target component. However, in the Fourier transform process, information about time is lost and the processing efficiency is poor. On the other hand, if wavelet transform is used, efficient processing can be performed while leaving information about time.

FIG. 14 is a functional block diagram showing an existing radar apparatus using such wavelet transform. In this radar apparatus, the expansion coefficients W1 to Wj generated by the wavelet conversion in the wavelet conversion circuit 3 are first input to the expansion coefficient selection circuit 4. The expansion coefficient selection circuit 4 inputs the expansion coefficient obtained by removing the expansion coefficient component that is expected to contain noise to the inverse wavelet transform circuit 50. The inverse wavelet transform circuit 50 returns the given expansion coefficient component to the frequency component again, the CFAR process in the CFAR circuit 5 is performed using the data after the retransformation, and the target detection process is performed in the detector 51. Is done.
Nakano et al., “Signal processing and image processing using wavelets”, Kyoritsu Publishing Co., Ltd. 49-70 (1999)

  By the way, in the conventional radar apparatus, the video signal is wavelet transformed, unnecessary components are removed on the wavelet axis, and then recombined to return to the signal on the time axis. Then, threshold detection is performed on the signal on the time axis to determine the presence or absence of the target. Therefore, the re-synthesis process after the wavelet transform is essential, and there is a problem that the circuit configuration and the scale of signal processing increase.

  In addition, the radar apparatus using the wavelet transform has a problem that even if the target can be detected, the direction in which the target exists is known only within the beam width, and thus the direction in which the target exists within the beam width cannot be measured.

  It is an object of the present invention to provide an angle measuring device that can measure the direction in which a target exists within a beam width even if it is a radar device using wavelet transform.

  In order to solve the above problems, the first invention is a target detection unit that detects a target based on a wavelet expansion coefficient obtained by performing wavelet transform on an input signal, and a target is detected by the target detection unit. And an angle measuring unit that performs monopulse angle measurement by transmitting and receiving a mono pulse beam at the selected beam position.

  The second invention is based on a wavelet transform circuit for wavelet transforming an input signal obtained from a reference beam and a sub beam of a squint beam, and a target based on a first wavelet expansion coefficient obtained from the wavelet transform circuit for the reference beam. A wavelet transform angle measurement circuit that measures angles based on a ratio between the first wavelet expansion coefficient and the second wavelet expansion coefficient obtained from the wavelet conversion circuit with respect to the sub beam when It is characterized by that.

  According to a third aspect of the present invention, there is provided a target based on a wavelet transform circuit for wavelet transforming an input signal obtained from a reference beam and a sub beam of a squint beam, and a first wavelet expansion coefficient obtained from the wavelet transform circuit for the reference beam. Is detected, the determination processing circuit determines whether the value based on the first wavelet expansion coefficient is equal to or less than a predetermined threshold value, and the determination processing circuit determines that the value is not smaller than the predetermined threshold value. The wavelet transform angle measuring circuit for measuring the angle based on the ratio between the first wavelet expansion coefficient and the second wavelet expansion coefficient obtained from the wavelet conversion circuit with respect to the sub beam, and a determination processing circuit. If it is determined that it is less than or equal to the threshold value of There is characterized in that a measuring corners perform monopulse angle measurement by transmitting and receiving monopulse beam to the detection beam position.

  According to a fourth aspect, in the third aspect, the determination processing circuit detects the first wavelet expansion coefficient when the target is detected based on the first wavelet expansion coefficient obtained from the wavelet conversion circuit with respect to the reference beam. It is characterized in that it is determined whether or not a value based on at least one of the second wavelet expansion coefficients is equal to or less than a predetermined threshold value.

  According to the angle measuring device according to the present invention, even a radar device using wavelet transform can measure the direction in which the target exists within the beam width.

  That is, according to the first invention, since the monopulse beam is transmitted / received to / from the target beam position detected by the wavelet transform and the monopulse angle measurement is performed, the target direction within the beam width can be measured.

  According to the second aspect of the invention, since the angle is measured based on the ratio of each wavelet expansion coefficient of the squint beam, the target is detected by the wavelet transform, and at the same time, the target within the beam width is determined by the ratio of the wavelet expansion coefficient. The direction can be measured.

  Further, according to the third invention, wavelet transform is performed on each of the squinted beams, and when the value of the wavelet expansion coefficient of the reference beam is larger than a predetermined threshold value, the angle is measured by the ratio of the wavelet expansion coefficients, If it is less than the threshold value, a monopulse beam is transmitted and received in the direction in which the target is detected, and monopulse angle measurement is performed, so the angle measurement accuracy can be determined by checking the level of the wavelet expansion coefficient, and if it is greater than the predetermined threshold value The angle can be measured in a short time using the angle measurement by the wavelet transform, and the angle measurement accuracy can be improved by applying the monopulse angle measurement if the angle is equal to or less than a predetermined threshold value.

  Further, according to the fourth invention, each wavelet transform is performed with the squinted beam, and when the value of each wavelet expansion coefficient of the squint beam is larger than a predetermined threshold value, the angle is measured by the ratio of the wavelet expansion coefficient, Since the monopulse beam is transmitted and received in the direction in which the target is detected and the monopulse angle measurement is performed if the threshold value is less than or equal to the predetermined threshold value, the same effect as the third invention can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the same or corresponding components will be described with the same reference numerals.

  FIG. 1 is a block diagram illustrating a configuration of a radar apparatus to which the angle measuring device according to the first embodiment of the present invention is applied. The radar apparatus includes an antenna 1, a PC (Pulse Compression) circuit 2, a selection circuit 7, a target detection unit 20, and an angle measurement unit 30.

  The antenna 1 converts a transmission signal into a radio wave and transmits it as a beam to the outside, and also receives a reflected wave of the transmitted beam and sends it to the PC circuit 2 as a reception signal. The beam transmission / reception direction of the antenna 1 is controlled by a control signal sent from the target detection unit 20.

  The PC circuit 2 applies pulse compression to the reception signal sent from the antenna 1 and sends it to the selection circuit 7. Details of pulse compression performed in the PC circuit 2 are described in, for example, “Yoshida et al.,“ Revised Radar Technology ”, IEICE, pp. 275-278 (1996)”.

  The selection circuit 7 selects whether the signal sent from the PC circuit 2 is sent to the target detection unit 20 or the angle measurement unit 30. Specifically, when the target is detected, the selection circuit 7 sends a signal sent from the PC circuit 2 to the target detection unit 20 and transmits / receives a monopulse beam to / from the target detected by the target detection unit 20. When angle measurement is performed, a signal transmitted from the PC circuit 2 is transmitted to the angle measurement unit 30.

  The target detection unit 20 executes processing for detecting a target using wavelet transform. The target detection unit 20 includes a wavelet transform (DWT) circuit 3, a development coefficient selection circuit 4, a CFAR (Constant False Alarm Rate) circuit 5, and a correlation processing circuit 6.

The wavelet transform circuit 3 uses the received signal sent from the antenna 1 via the PC circuit 2 and the selection circuit 7 as input data, and performs discrete wavelet transform on this input data. Here, when the input data to the wavelet transform circuit 3 is represented by a complex signal f0 (I + jQ), the signal f to be subjected to discrete wavelet transform includes four types shown in the following equations (1) to (4). Can think.

here,
I: Real part Q: Imaginary part j: Imaginary unit The wavelet transform circuit 3 performs discrete wavelet transform using such a signal f as input data to obtain a plurality of wavelet expansion coefficients. In the discrete wavelet transform, an input / output signal (original waveform) as shown in FIG. 3A is approximated by a scaling coefficient and a wavelet expansion coefficient. The scaling factor has a plurality of levels 1 to j, and the degree of approximation differs depending on each level. The wavelet expansion coefficient corresponds to the difference between the levels of the scaling coefficient.

Such a discrete wavelet transform can be represented by a filter. FIG. 2 is a diagram illustrating filter characteristics of the discrete wavelet transform. In order of level, the frequency domain transitions from wide to low. That is, it has a filter characteristic for a short time in the high band, and has a filter characteristic for a long time as it goes to the low band. This filter characteristic can be expressed by the following equations (5) to (10).

here,
fj: j-level approximation function (j = 1 to J)
gj: j level expansion function sk: scaling expansion coefficient (k = 1 to K)
wk: Wavelet expansion coefficient φ: Scaling function ψ: Mother wavelet function pk: Sequence determined by the mother wavelet function *: Complex conjugate Here, w shown in Equation (9) is an approximate function and an actual waveform at level j And a wavelet expansion coefficient. FIG. 3 shows how the wavelet expansion coefficient is calculated.

  In other words, the wavelet transform used for target detection changes the parameters (shift R and scale f) of the wavelet transform kernel (for example, Mexican hat) with respect to the input data as shown in FIG. It can be said that fitting is performed by performing correlation processing while performing processing to obtain high wavelet transform data output as shown in FIG. Using this wavelet expansion has the advantage that signals can be detected with a small number of hits. The wavelet expansion coefficient obtained in the wavelet transform circuit 3 is sent to the expansion coefficient selection circuit 4.

  The expansion coefficient selection circuit 4 selects expansion coefficients W1 to Wm from the wavelet expansion coefficients sent from the wavelet transform circuit 3 and sends them to the CFAR circuit 5.

  The CFAR circuit 5 generates a signal in which the false alarm probability is suppressed to a certain low for each of the expansion coefficients W1 to Wm sent from the expansion coefficient selection circuit 4, and sends the signal to the correlation processing circuit 6.

  FIG. 5 is a block diagram showing a configuration of a linear CFAR circuit that performs normalization by arithmetic mean as an example of the CFAR circuit 5. The CFAR circuit 5 includes a delay circuit 51, an adder circuit 52, an averaging processing circuit 53, a divider circuit 54, and a threshold detection circuit 55.

  The delay circuit 51 delays the input signal xi and then sends it to the adder circuit 52 and the divider circuit 54. The adder circuit 52 adds the N pieces of data sent from the delay circuit 51 during a certain period, and sends it to the averaging processing circuit 53. The averaging processing circuit 53 calculates the average value of the N pieces of data sent from the adding circuit 52 and sends it to the dividing circuit 54. The division circuit 54 divides the data sent from the delay circuit 51 by the average value, and sends the division result to the threshold detection circuit 55. The threshold detection circuit 55 compares the signal sent from the division circuit 54 with a predetermined threshold level, and sends a signal representing the comparison result to the correlation processing circuit 6 as a detection signal. The CFAR circuit 5 can also be realized by a logarithmic CFAR unit that performs normalization with a geometric mean.

  The correlation processing circuit 6 performs correlation processing on the detection signal sent from the CFAR circuit 5 and integrates the detection signal to reduce false alarms and outputs the detection information as target detection information. A signal representing the target beam position represented by the detection information generated in the correlation processing circuit 6 is sent to the antenna 1. As a result, transmission / reception of the monopulse beam to the beam position where the target is detected is subsequently performed.

  The angle measuring unit 30 includes an MTI (Moving Target Indicator) circuit 8, a DFT (Discreet Fourier Transform) circuit 9, a CFAR circuit 10, and a monopulse angle measuring circuit 11.

  The MTI circuit 8 suppresses the clutter contained in the received signal received from the antenna 1 via the PC circuit 2 and the selection circuit 7 and sends it to the DFT circuit 9.

  The DFT circuit 9 converts the clutter-suppressed signal sent from the MTI circuit 8 into a signal on the time-frequency axis by discrete Fourier transform, and sends the signal to the CFAR circuit 10. The CFAR circuit 10 is the same as the CFAR circuit 5 of the target detection unit 20 described above, performs CFAR processing on the signal sent from the DFT circuit 9 and sends the signal to the monopulse angle measurement circuit 11.

  The monopulse angle measurement circuit 11 performs monopulse angle measurement using an error curve prepared in advance. Monopulse angle measurement includes squint angle measurement (amplitude comparison monopulse) using a squinted Σ beam and phase monopulse angle measurement (phase comparison monopulse) using a Σ beam and a Δ beam.

In the case of squint angle measurement, the error voltage ε is obtained by taking the ratio of two beams such as the ΣA beam and the ΣB beam as shown in FIG. 6A, and an error curve as shown in FIG. 6B prepared in advance. The angle corresponding to the error voltage ε is obtained. The error voltage ε is obtained by the following equation (11).

here,
ΣA; ΣA beam ΣB; ΣB beam *; complex conjugate In the case of phase monopulse, the error voltage ε is obtained by taking the ratio of two beams such as Σ beam and Δ beam as shown in FIG. With reference to an error curve table as shown in FIG. 7B, an angle corresponding to the error voltage ε is obtained. The error voltage ε is obtained by the following equation (11).

here,
Σ; Σ beam Δ; Δ beam In this way, the angle calculated in the monopulse angle measuring circuit 11 is output to the outside as an angle value representing the target angle.

  Next, the operation of the radar apparatus to which the angle measuring apparatus according to the first embodiment of the present invention configured as described above is applied will be described with reference to the flowchart shown in FIG.

  When the search by the radar device is started, first, a target detection process by discrete wavelet transform (DWT) is performed (step S1), and it is checked whether or not the target is detected (step S2). If it is determined in step S2 that the target has not been detected, the sequence proceeds to step S5.

  On the other hand, when it is determined in step S2 that the target has been detected, transmission / reception of a monopulse beam is then performed (step S3). Next, monopulse angle measurement is performed (step S4). Thereby, the direction (angle) in which the target exists within the beam width is acquired.

  Next, it is checked whether or not the search for the entire space has been completed (step S5). If it is determined in step S5 that the search of the entire space has not been completed, the sequence returns to step S1, the beam direction is changed to the next direction, and the above-described processing is repeated. On the other hand, if it is determined in step S5 that the search of the entire space has been completed, the beam direction is returned to the initial position of the search space (step S6). Thereafter, the sequence returns to step S1, and the above-described processing is repeated.

  The angle measuring device according to the first embodiment described above is configured to perform angle measurement by transmitting and receiving a monopulse beam to the beam position where the target detected by the discrete wavelet transform exists, but the angle measuring device according to the second embodiment. The angle device performs transmission / reception of the squint beam ΣA and reception of ΣB in order to perform angle measurement using the expansion coefficient of the discrete wavelet transform.

  FIG. 9 is a block diagram illustrating a configuration of a radar apparatus to which the angle measuring device according to the second embodiment of the present invention is applied. This radar apparatus includes an antenna 1, a PC circuit 2, a wavelet transform circuit 3, a expansion coefficient selection circuit 4, a CFAR circuit 5, a correlation processing circuit 6, and a wavelet transform angle measurement circuit (hereinafter referred to as “DWT angle measurement circuit”) 12. Has been.

  A reception signal received by the antenna 1 is sent to the PC circuit 2. The PC circuit 2 performs pulse compression on the received signal sent from the antenna 1 and sends it to the wavelet transform circuit 3. The wavelet transform circuit 3 performs discrete wavelet transform on the signal sent from the PC circuit 2 and sends it to the expansion coefficient selection circuit 4. The expansion coefficient selection circuit 4 selects expansion coefficients W1 to Wm from the signal sent from the wavelet transform circuit 3 and sends them to the CFAR circuit 5.

  The CFAR circuit 5 generates, for each of the expansion coefficients W1 to Wm sent from the expansion coefficient selection circuit 4, a signal in which the false alarm probability is suppressed to a certain low level, and sends it to the correlation processing circuit 6 as a detection signal. send. The correlation processing circuit 6 performs correlation processing on the detection signal sent from the CFAR circuit 5 and integrates the detection signal to reduce false alarms and send it to the DWT angle measuring circuit 12 as detection information. .

The DWT angle measurement circuit 12 performs angle measurement using a squinted Σ beam, more specifically, a ΣA beam (reference beam) used for transmission and reception and a ΣB beam (sub beam) used only for reception. Specifically, the DWT angle measurement circuit 12 performs the discrete wavelet transform on the ΣB beam when the target can be detected by the discrete wavelet transform in the ΣA beam, and each wavelet expansion coefficient of the ΣA beam and the ΣB beam. The DWT angle measurement is carried out using the following equation (13).

here,
WA: ΣA wavelet expansion coefficient WB: ΣB wavelet expansion coefficient In other words, the DWT angle measurement circuit 12 has two wavelet expansions such as a ΣA wavelet expansion coefficient WA and a ΣB wavelet expansion coefficient WB as shown in FIG. The error voltage ε is obtained by taking the ratio of the coefficients, and an angle corresponding to the error voltage ε is obtained by referring to a previously prepared error curve table as shown in FIG. Thereby, the target angle measurement value within the beam width can be obtained.

  Next, the operation of the radar apparatus to which the angle measuring apparatus according to the second embodiment of the present invention configured as described above is applied will be described with reference to the flowchart shown in FIG.

  When the search by the radar apparatus is started, first, a target is detected by discrete wavelet transform (DWT) (step S11), and it is checked whether the target is detected (step S12). If it is determined in step S12 that the target has not been detected, the sequence proceeds to step S14. On the other hand, if it is determined in step S12 that the target has been detected, then angle measurement is performed by discrete wavelet transform (DWT) (step S13).

  Next, it is checked whether or not the search for the entire space has been completed (step S14). If it is determined in step S14 that the search for the entire space has not been completed, the sequence returns to step S11, the beam direction is changed to the next direction, and the above-described processing is repeated. On the other hand, if it is determined in step S14 that the search of the entire space has been completed, the beam direction is returned to the initial position of the search space (step S15). Thereafter, the sequence returns to step S11, and the above-described processing is repeated.

  In the DWT angle measurement in the angle measuring device according to the second embodiment described above, when the value is equal to or less than the value of the DWT expansion coefficient, the DWT expansion coefficient and the target signal level are not necessarily proportional, and there is a possibility that an angle measurement error may occur. is there. As a countermeasure, in the angle measuring device according to the third embodiment, the DWT expansion coefficient is compared with a predetermined threshold value, and if the DWT expansion coefficient is larger than the predetermined threshold value, the DWT angle measurement is performed, and the predetermined threshold value Below, as in the first embodiment, the monopulse beam is transmitted / received to / from the beam position where the target is detected, and the monopulse angle measurement is performed.

  FIG. 12 is a block diagram illustrating a configuration of a radar apparatus to which the angle measuring device according to the third embodiment of the present invention is applied. This radar apparatus is configured by adding a determination processing circuit 13, a selection circuit 14, and an angle measuring unit 30 to a radar apparatus to which the angle measuring apparatus according to the second embodiment is applied.

  The determination processing circuit 13 determines whether or not the detection information output from the correlation processing circuit 6 is less than or equal to a predetermined threshold value. Then, the determination result is sent to the selection circuit 14, and when the detection information is not more than a predetermined threshold value, a control signal is sent to the antenna 1. Thereby, transmission / reception of the monopulse beam is performed with respect to the beam position where the target is detected. In this case, a signal obtained from the PC circuit 2 is sent to the angle measuring unit 30.

  The angle measuring unit 30 is the same as that of the first embodiment. The angle measurement value obtained by the monopulse angle measurement in the angle measurement unit 30 is sent to the selection circuit 14.

  The selection circuit 14 selects either the angle measurement value transmitted from the DWT angle measurement circuit 12 or the angle measurement value transmitted from the angle measurement unit 30 according to the determination result transmitted from the determination processing circuit 13. Select and output. Therefore, if the DWT expansion coefficient is larger than the predetermined threshold value, the angle measurement value obtained by DWT angle measurement is output, and if it is equal to or less than the predetermined threshold value, the angle measurement value obtained by monopulse angle measurement is output. .

  Note that the threshold value may be set to both ΣA and ΣB, or may be set only to the value of ΣA.

  Next, the operation of the radar apparatus to which the angle measuring apparatus according to the third embodiment of the present invention configured as described above is applied will be described with reference to the flowchart shown in FIG.

  When the search by the radar apparatus is started, first, a target is detected by discrete wavelet transform (DWT) (step S21), and it is checked whether the target is detected (step S22). If it is determined in step S22 that the target has not been detected, the sequence proceeds to step S27. On the other hand, if it is determined in step S22 that the target has been detected, it is then checked whether or not the detected information is greater than a predetermined threshold value (step S23).

  If it is determined in step S23 that the detection information is greater than the predetermined threshold value, angle measurement is performed by discrete wavelet transform (DWT) (step S24). Thereafter, the sequence proceeds to step S27. On the other hand, if it is determined in step S23 that the detection information is not greater than the predetermined threshold value, then transmission / reception of a monopulse beam is performed (step S25). Next, monopulse angle measurement is performed (step S26). Thereafter, the sequence proceeds to step S27.

  In step S27, it is checked whether or not the entire space has been searched. If it is determined in step S27 that the search of the entire space has not been completed, the sequence returns to step S21, the beam direction is changed to the next direction, and the above-described processing is repeated. On the other hand, if it is determined in step S27 that the search of the entire space has been completed, the beam direction is returned to the initial position of the search space (step S28). Thereafter, the sequence returns to step S21, and the above-described processing is repeated.

  In the present invention, the order of signal processing can be changed if angle measurement can be performed using wavelet transform. For example, before the wavelet transform, it is possible to configure so that the wavelet transform is applied after suppressing the clutter including the MTI processing.

  The angle measuring device according to the present invention can be used for a radar device or a receiving device.

It is a block diagram which shows the structure of the radar apparatus to which the angle measuring device which concerns on Example 1 of this invention was applied. It is a figure which shows the filter characteristic of discrete wavelet transform. It is a figure which shows a mode that a wavelet expansion coefficient is calculated in discrete wavelet transformation. It is a figure for demonstrating the principle of a discrete wavelet transform. It is a block diagram which shows the structure of the CFAR circuit in the radar apparatus to which the angle measuring device which concerns on Example 1 of this invention was applied. It is a figure which shows the principle of a squint angle measurement. It is a figure which shows the principle of a phase monopulse angle measurement. It is a flowchart which shows operation | movement of the radar apparatus to which the angle measuring device which concerns on Example 1 of this invention was applied. It is a block diagram which shows the structure of the radar apparatus with which the angle measuring device which concerns on Example 2 of this invention was applied. It is a figure which shows the principle of the angle measurement by a wavelet. It is a flowchart which shows operation | movement of the radar apparatus to which the angle measuring device which concerns on Example 2 of this invention was applied. It is a block diagram which shows the structure of the radar apparatus with which the angle measuring device which concerns on Example 3 of this invention was applied. It is a flowchart which shows operation | movement of the radar apparatus to which the angle measuring device which concerns on Example 3 of this invention was applied. It is a figure for demonstrating the radar apparatus using the conventional wavelet transform.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 PC circuit 3 Wavelet transformation circuit 4 Expansion coefficient selection circuit 5 CFAR circuit 6 Correlation processing circuit 7 DWT angle measurement circuit 8 MTI circuit 9 DFT circuit 10 CFAR circuit 11 Monopulse angle measurement circuit 12 DWT angle measurement circuit 13 Determination processing circuit 14 Selection circuit 20 Target detection unit 30 Angle measurement unit

Claims (4)

A target detection unit for detecting a target based on a wavelet expansion coefficient obtained by performing wavelet transform on the input signal;
An angle measuring unit that performs monopulse angle measurement by transmitting and receiving a mono pulse beam to the beam position where the target is detected by the target detection unit;
An angle measuring device comprising: A wavelet transform circuit for wavelet transforming an input signal obtained by a reference beam and a sub beam of a squint beam;
When the target is detected based on the first wavelet expansion coefficient obtained from the wavelet transform circuit with respect to the reference beam, the first wavelet expansion coefficient and the sub beam are obtained from the wavelet transform circuit. A wavelet transform angle measuring circuit for measuring an angle based on a ratio with the second wavelet expansion coefficient;
An angle measuring device comprising: A wavelet transform circuit for wavelet transforming an input signal obtained by a reference beam and a sub beam of a squint beam;
When a target is detected based on the first wavelet expansion coefficient obtained from the wavelet transform circuit with respect to the reference beam, it is determined whether the value based on the first wavelet expansion coefficient is equal to or less than a predetermined threshold value. A determination processing circuit to perform,
In the determination processing circuit, when it is determined that it is not smaller than the predetermined threshold value, the first wavelet expansion coefficient and the second wavelet expansion coefficient obtained from the wavelet transform circuit for the sub beam, A wavelet transform angle measuring circuit that measures angles based on the ratio of
In the determination processing circuit, when it is determined that the value is equal to or less than the predetermined threshold value, an angle measuring unit that performs monopulse angle measurement by transmitting and receiving a monopulse beam to the beam position where the target is detected;
An angle measuring device comprising:   When the target is detected based on the first wavelet expansion coefficient obtained from the wavelet transform circuit with respect to the reference beam, the determination processing circuit calculates the first wavelet expansion coefficient and the second wavelet expansion coefficient. 4. The angle measuring device according to claim 3, wherein it is determined whether or not a value based on at least one is equal to or less than a predetermined threshold value.

Images