JP2015230284A - Radar apparatus and radar signal processing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulse compression radar apparatus reducing a loss even at the time of long time integration, suppressing fixed clutter and enhancing target detection capability.SOLUTION: A radar apparatus identifies a substantial range of a target position by inputting a radar pulse reception signal and applying coherent integration processing of a temporal axis to individual range axes of a Σ beam and a Δ beam, focuses on the substantial range of the target position, performs integration processing of coherent integration processing results of the temporal axis in a frequency domain, acquires individual range-Doppler images of the Σ beam and the Δ beam by bringing back to a time domain, detects a target cell by CFAR processing with respect to the range-Doppler image of the Σ beam and performs distance measurement, and performs angle measurement by using a signal of a cell corresponding to the target cell detected by the Σ beam from the range-Doppler image of the Δ beam.

Description

  The present embodiment relates to a radar apparatus that is mounted on, for example, an aircraft and detects a small target at a long distance, and a radar signal processing method thereof.

  A conventional aircraft-mounted radar device has a problem that integration loss occurs due to the non-linearity of the phase due to the range walk and the motion of the mounted device when long-time integration with a large number of integration hits is performed. Further, when the main lobe faces the ground surface, the sea surface, or the like, the fixed clutter is received, and thus there is a problem that the target detection performance deteriorates.

SAR method (range compression), Ouchi, “Basics of Synthetic Aperture Radar for Remote Sensing”, Tokyo Denki University Press, pp.131-149 (2003) SAR method (Az compression), Ouchi, “Basics of Synthetic Aperture Radar for Remote Sensing”, Tokyo Denki University Press, pp.171-178 (2003) CFAR (Constant False Alarm Rate), Yoshida, “Revised Radar Technology”, IEICE, pp.87-89 (1996) 2D CFAR, Guy Morris, "AIRBORNE PULSE DOPPLER RADAR 2nd edition", pp.399-404 (1996) Phase monopulse angle measurement, Yoshida, “Revised radar technology”, IEICE, pp. 260-264 (1996) MPRF, Guy Morris, "AIRBORNE PULSE DOPPLER RADAR 2nd edition", pp.264-270 (1996) HPRF system, George W. Stimson, "INTRODUCTION TO AIRBORN RADAR", HEGHES, pp231-239 (1983) FM-CW radar, Yoshida, "Revised radar technology", IEICE, pp.274-275 (1996) PGA, Charles V. Jakowatz, "Spotlight-Mode Synthetic Aperture Radar: A Signal Processing Approach", Springer, pp.251-256 (1996)

  As described above, the conventional radar apparatus has a problem in that when long-time integration with a large number of integration hits is performed, an integration loss occurs due to phase nonlinearity due to the range walk and the motion of the mounted machine. Further, when the main lobe faces the ground surface, the sea surface, or the like, the fixed clutter is received, and thus there is a problem that the target detection performance deteriorates.

  The present embodiment has been made in view of the above problems, and provides a radar apparatus and a radar signal processing method thereof that can reduce loss even during long-time integration, suppress fixed clutter, and increase target detection capability. With the goal.

  In order to solve the above-described problems, the radar apparatus according to the present embodiment includes a Σ beam image acquisition unit, a Δ beam image acquisition unit, and a distance measurement / angle measurement unit. The Σ-beam image acquisition means inputs a radar pulse reception signal, performs a time-axis coherent integration process with respect to the Σ-beam range axis, identifies an approximate range of the target position, and focuses on the approximate range of the target position. The time-axis coherent integration processing result is integrated in the frequency domain and returned to the time domain to obtain a range-Doppler image of the Σ beam. The Δ beam image acquisition means inputs the radar pulse reception signal, performs a time-axis coherent integration process with respect to the Δ beam range axis, identifies the approximate range of the target position, and focuses on the approximate range of the target position. In addition, a range-Doppler image of Δ beam is acquired by integrating the time-axis coherent integration processing result in the frequency domain and returning it to the time domain. The distance measuring / angle measuring means detects a target cell by CFAR (Constant False Alarm Rate) processing for the Σ beam range-Doppler image acquired by the Σ beam image acquiring means, and measures the distance. The angle is measured using the signal of the cell corresponding to the target cell detected by the Σ beam from the range-Doppler image of the Δ beam acquired by the image acquisition means.

1 is a block diagram showing a configuration of a radar apparatus according to a first embodiment. 2 is a flowchart showing a flow of processing of a signal processing unit in the radar apparatus shown in FIG. The conceptual diagram which shows the positional relationship of a body flight axis | shaft and a target in the radar apparatus shown in FIG. The block diagram which shows the structure of the radar apparatus which concerns on 2nd Embodiment. 5 is a flowchart showing a processing flow of a signal processing unit in the radar apparatus shown in FIG. The conceptual diagram for demonstrating the phase correction of a signal processing part in the radar apparatus shown in FIG. 5 is a flowchart showing a flow of phase correction processing of a signal processing unit in the radar apparatus shown in FIG. 4. The block diagram which shows the structure of the radar apparatus which concerns on 3rd Embodiment. 9 is a flowchart showing a flow of processing of a signal processing unit in the radar apparatus shown in FIG. The figure which shows the relationship between the division of LPRF in a radar apparatus, and ambiguity. The figure which shows the relationship between the division of HPRF in a radar apparatus, and ambiguity. The figure which shows the relationship between the division of MPRF in a radar apparatus, and ambiguity. The figure which shows the role of a frequency filter in the radar apparatus shown in FIG. The figure which shows description of two-dimensional CFAR in the radar apparatus shown in FIG. The figure for demonstrating the ranging process in the radar apparatus shown in FIG. The figure for demonstrating the speed measurement process in the radar apparatus shown in FIG. The block diagram which shows the structure of the radar apparatus which concerns on 4th Embodiment. The flowchart which shows the flow of a process of a signal processing part in the apparatus shown in FIG. The figure which shows description of the ranging of HPRF in the apparatus shown in FIG.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
The radar apparatus according to the first embodiment will be described below with reference to FIGS. 1 to 3.

  FIG. 1 is a block diagram showing a system configuration of the radar apparatus, FIG. 2 is a flowchart showing a specific processing flow thereof, and FIG. 3 shows a positional relationship between a fuselage flight axis of an aircraft on which the radar apparatus is mounted and a target. FIG.

  In FIG. 1, an antenna 1 is a phased array antenna in which a plurality of antenna elements are arranged to form a large aperture array. A PRF (Pulse Repetition Frequency) signal) is transmitted in a designated direction and the reflected wave is received. The transmission / reception unit 21 forms a reception beam in an arbitrary direction to obtain a PRF reception signal by performing phase control and combining the signals respectively received by the plurality of antenna elements of the antenna 1 according to an instruction from the beam control unit 22 (FIG. 2: Step S11). The PRF reception signal obtained by the reception beam is sent to the signal processor 3.

  The signal processor 3 distributes the PRF received signal from the transceiver 2 into two systems for Σ beam and Δ beam. The Σ beam system includes an AD (Analog-Digital) conversion unit 311, a range axis FFT (Fast Fourier Transformation) unit (FFTx) 321, a range reference signal multiplication unit 331, a data storage unit 341, and a cross range reference signal multiplication unit 351. , A cross range axis FFT unit (FFTy) 361, a range axis inverse FFT unit (inverse FFTx) 371, a CFAR processing unit 38, a distance measuring unit 39, and an angle measuring unit 3A. The Δ beam system includes an AD (Analog-Digital) converter 312, a range axis FFT unit (FFTx) 322, a range reference signal multiplier 332, a data storage unit 342, a cross range reference signal multiplier 352, and a cross range axis FFT. Unit (FFTy) 362, a range axis inverse FFT unit (inverse FFTx) 372, and a cell extraction unit 3B.

  In the Σ beam system, the PRF reception signal supplied from the transceiver 2 is converted into a digital signal by the AD converter 311 (FIG. 2: step S12). The conversion result is FFT processed in the range axis direction by the range axis FFT unit 321 (FIG. 2: step S13), and the range reference signal multiplication unit 331 multiplies the range reference signal by the linear chirp in the range axis direction to compress the range. (FIG. 2: Step S14). The range-compressed PRF reception signal is stored in the data storage unit 341 (FIG. 2: step S15) and used for long-time coherent integration.

  The PRF received signal subjected to the range compression is subjected to FFT processing in the cross range axis (PRI axis) direction by the cross range axis FFT unit 361 when the processing selection unit 3C1 receives a processing selection (FIG. 2: In step S16), the range axis inverse FFT unit 371 performs inverse FFT processing in the range axis direction (FIG. 2: step S17). The target cell in the range-Doppler axis is detected by the CFAR processing unit 38 for the pulse-compressed signal in this way (FIG. 2: step S18), and the distance measuring unit 39 and the angle measuring unit 3A respectively. The distance of the detection target cell and the angle in the range direction are detected (FIG. 2: steps S19 and S20).

  On the other hand, in the Δ beam system, the PRF reception signal supplied from the transceiver 2 is converted into a digital signal by the AD converter 312 (FIG. 2: step S21). The conversion result is FFT processed in the range axis direction by the range axis FFT unit 322 (FIG. 2: step S22), and the range reference signal multiplication unit 332 multiplies the reference signal by the linear chirp in the range axis direction to perform range compression. (FIG. 2: Step S23). The range-compressed PRF reception signal is stored in the data storage unit 342 (FIG. 2: step S24) and used for long-time coherent integration.

  Further, the PRF received signal subjected to the range compression is subjected to FFT processing in the cross range axis (PRI axis) direction by the cross range axis FFT unit 362 when the processing selection unit 3C2 receives the processing selection (FIG. 2: In step S25), the range axis inverse FFT unit 372 performs inverse FFT processing in the range axis direction (FIG. 2: step S26). With respect to the pulse-compressed signal in this way, the cell extraction unit 3B detects the Δ beam target similar to the target cell of the range-Doppler axis detected on the Σ beam side based on the information from the CFAR processing unit 38. A cell is extracted (FIG. 2: step S27). For the extracted target cell of the Δ beam, the angle measuring unit 3A detects the angle in the cross range direction.

  Here, the process selection units 3C1 and 3C2 determine whether or not there is an angle detection target in the angle measurement unit 3A (FIG. 2: step S28), and if no detection target is obtained, the next PRI transmission / reception is performed. A target cell detection process is performed on the obtained PRF received signal, and when a detection target is obtained, an even more efficient integration effect is obtained in consideration of a small target RCS (radar scattering cross section). For this purpose, long-time coherent integration is performed. For this purpose, the process selection units 3C1 and 3C2 read out the range compression data stored in the data storage units 341 and 342 with respect to the beam direction in which the target is detected by the angle measurement unit 3A (depending on the elapsed time). May use a signal transmitted and received again). Switch to a long-time coherent integration process.

  Specifically, in the Σ beam system, when the long-time coherent integration process is switched, the range compressed data is read from the data storage unit 341 (FIG. 2: step S29), and the cross range reference signal multiplication unit 351 is read out. 2 is multiplied by a cross range reference signal by linear chirp in the cross range axis direction (FIG. 2: step S30), and then the FFT processing in the cross range axis (PRI axis) direction by the cross range axis FFT unit 361 (FIG. 2: Step S31), reverse FFT processing in the range axis direction by the range axis inverse FFT unit 371 (FIG. 2: step S32), target cell detection in the range-Doppler axis by the CFAR processing unit 38 (FIG. 2: step S33), and distance measurement The distance of the detection target cell and the angle in the range direction are detected by the unit 39 and the angle measurement unit 3A (FIG. 2: scan). -Up S34, S35).

  On the other hand, also in the Δ beam system, when switching to the long-time coherent integration process, the range compressed data is read from the data storage unit 342 (FIG. 2: step S36), and the cross range reference signal multiplication unit 352 After the cross range reference signal by the linear chirp in the cross range axis direction is multiplied (FIG. 2: step S37), the cross range axis FFT unit 362 performs FFT processing in the cross range axis (PRI axis) direction (FIG. 2: step S38). Then, the inverse FFT process in the range axis direction (FIG. 2: step S39) is performed by the range axis inverse FFT unit 372. Subsequently, the cell extraction unit 3B extracts a target cell similar to the target cell of the range-Doppler axis detected on the Σ beam side based on the information from the CFAR processing unit 38 (FIG. 2: step S40). For the extracted target cell of the Δ beam, the angle measuring unit 3A detects the angle in the cross range direction. In this way, the angle measurement unit 3A can obtain angle measurement results in the range direction and cross range direction of the target cell.

  Here, FIG. 3 shows a case where the radar apparatus having the above configuration forms a real aperture beam and directs the beam so as to always irradiate the target detection range when mounted on a flying object. At this time, since clutter on the ground surface is also transmitted and received from the main lobe and side lobes, the coordinate system is also described. Data is acquired in units of range cells in the PRI for each pulse transmitted at a PRI (Pulse Repetition Interval) interval within the synthetic aperture time (one cycle). A long-time coherent integration process is performed using the acquired data.

Next, the long-time coherent integration process will be described in detail.
First, range compression will be described (see Non-Patent Document 1). Range compression is a correlation process between an input signal and a reference signal for range compression, and is formulated as follows in the frequency domain (321, 322, 331, 332 in FIG. 1).

  In order to convert the range compressed signal s represented by the expression (3) into a signal on the time axis, inverse Fourier transform may be performed. However, in order to perform cross range compression (cross range reference signal multipliers 351 and 352, non-patent document 2) after this, the range compressed signal s remains on the (ω, u) axis.

Next, a reference signal fs0 for cross range compression is generated.

The detection positions (Xc, Yc, Zc) are positions calculated from the distance measurement values and the angle measurement values detected by the distance measurement unit 39 and the angle measurement unit 3A. When there are a plurality of targets, a reference signal is generated for each detection target. The offset is used when the detection range is corrected using tracking information or the like. A signal cs is obtained by multiplying the above-described range compression signal s and the reference signal fs0 for cross range compression.

Using this, FFT is performed on the u-axis to obtain a signal fcs (ω, ku) (FIG. 1, cross-range axis FFT units 361 and 362).

The long-time integration output fp can be calculated by the range axis inverse FFT units 371 and 372 regarding the ω axis of fcs.

From the output of fp (t, ku), it is detected using one-dimensional or two-dimensional CFAR processing (see Non-Patent Documents 3 and 4), and the distance measurement unit 39 converts the time into a range (distance) and outputs it. .

  In the present embodiment, the processing focuses on (Xc, Yc, Zc). When the target is a sufficiently long distance, the focal point may be set at an infinite point, and the processing scale can be reduced. In addition, the influence of the phase shift can be reduced.

Next, a method for measuring the angle will be described. For the output of the Δ beam (ΔAz, ΔEL) of the antenna, a range-Doppler image is obtained in the same manner as the Σ beam. Next, a cell similar to the cell (range-Doppler axis cell) detected by the Σ beam is extracted, and an error voltage of the following equation is calculated.

  In the beam patterns of Σ and Δ, the relationship between the reference error voltage εref and the angle is tabulated based on the angle characteristics acquired in advance, ε is observed, and if the angle is extracted by quoting the table, the observation angle becomes can get. If the same processing is performed for the Az angle and the EL angle, the measured angles θAz and θEL of both axes can be implemented (see Non-Patent Document 5).

  As described above, according to the configuration of the first embodiment, the loss and phase nonlinearity due to the range walk are corrected and integrated on the frequency axis, so that the loss can be reduced. Further, since the Δ beam is used, angle measurement can be performed.

(Second Embodiment)
In the method using long-time coherent integration, there may be a phase change due to the target acceleration or the acceleration of the mounted machine during the integration. As this countermeasure method, a method similar to PGA (Phase gradient autofocus: Non-Patent Document 9), which is an autofocus method for synthetic aperture processing, can be applied. FIG. 4 is a block diagram showing a system configuration of a radar apparatus when this coping method is applied as a second embodiment, and FIG. 5 is a flowchart showing a specific processing flow when the processing method is applied. FIG. 6 is a conceptual diagram for explaining the processing of the coping method. 4 and 5, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals.

  In this embodiment, the difference from the first embodiment is that a correction signal extraction unit 3D that extracts a correction signal from a range-Doppler (cross range) image obtained by the range axis inverse FFT processing unit 371 of the Σ system, A cross range reference signal correction unit 3E that corrects the cross range reference signal of the cross range reference signal multipliers 351 and 352 based on the correction signal is added (steps S41 and S42 in FIG. 5).

First, as shown in FIG. 6A, N local maximum values exceeding a predetermined amplitude threshold are extracted from the result of the range-Doppler (cross range) image. Next, the maximum value is shifted to 0 frequency on the Doppler axis in order to extract only the phase shift due to the flight path and body motion, excluding the phase gradient with respect to the Doppler axis of the maximum value. Here, in order to remove the vibration component of the phase shift and obtain a stable correction component, as shown in FIG. 6B, a window function (window) is multiplied around it and zero-filled outside the window function. An error signal S0 shown in FIG. 6C is obtained by generating a signal s0 and performing inverse FFT on the signal.

Subsequently, as shown in FIG. 6 (d), a correction amount Wc (t) that is an inverse characteristic of the error signal S0 is obtained, and the cross-range compression signal fs0 (ω, u) (range frequency axis, flight length) is obtained. Multiply fs0 (t) converted to the time axis (PRI axis). In this way, the corrected reference signal Rc shown in FIG. 6E is obtained.

  Using this reference signal Fs0, a corrected range-Doppler image is obtained by the processing of equations (5) to (7). This processing flow is shown in FIG.

  That is, in FIG. 7, when SAR processing is instructed (step S51), the peak value of the cross-range compressed signal is extracted (step S52), ± M cells before and after the peak are extracted (step S53), and zero shift is performed. (Step S54), window multiplication is performed to perform zero padding (step S55). Next, an error signal is obtained by converting from a frequency axis signal to a time axis signal by inverse FFT (step S56), a correction value having the inverse characteristic is calculated (step S57), and the correction value is converted to the time axis. SAR processing is performed by multiplying the cross-range compressed signal converted into (step S58). It is determined whether the SAR process has been performed for all the peak values detected at this time (step S59). If there is an unprocessed peak value, the peak value is changed and the process is repeated from step S53 (step S60). When the processing is completed for all peak values, a series of processing ends. By repeating this series of processing M times (M ≧ 1) as necessary, a range-Doppler image with little integration loss can be obtained. By performing CFAR processing using this range-Doppler image, the target cell can be reliably detected, and a more accurate distance can be output.

  As described above, according to the configuration of the second embodiment, the correction signal is generated using the signal extracted from the range-Doppler image and the phase is corrected, so that the integral loss can be reduced.

(Third embodiment)
FIG. 8 is a block diagram showing a system configuration of a radar apparatus when MPRF is applied as a third embodiment, and FIG. 9 is a flowchart showing a specific processing flow when the processing method is applied. 8 and 9, the same parts as those in FIGS. 4 and 5 are denoted by the same reference numerals.

  In this embodiment, the difference from the second embodiment is that the signals obtained by the cross-range axis FFT processing units 361 and 362 of the Σ system and Δ system are passed through the frequency filters 3F1 and 3F2, respectively. And a range obtained by CFAR processing on the side of the Σ beam and a point where a specific frequency component in which is present is extracted and sent to the cross-range inverse FFT processing units 371 and 372 (steps S60, S61, S65, and S66 in FIG. 9). The target cell of the Doppler axis is input to the MPRF ranging / speed measuring unit 3G to perform distance measurement and speed measurement calculation on the target cell (steps S64 and S69 in FIG. 9).

  Here, there are three types of relationship between PRF and range-Doppler in the radar apparatus: LPRF (Low PRF), HPRF (High PRF), and MPRF (Middle PRF). The outline is shown in FIGS. As shown in FIG. 10, LPRF has no ambiguity on the range axis and ambiguity on the Doppler frequency axis. As shown in FIG. 11, HPRF has ambiguity on the range axis and no ambiguity on the Doppler frequency axis. As shown in FIG. 12, the MPRF has ambiguity on both the range axis and the Doppler frequency axis.

The range-Doppler image includes an image by a fixed clutter. When the intensity is strong, it is necessary to suppress in order to extract only the moving target. The clutter frequency for this purpose can be expressed by the following equation at the left and right ends of the main beam with reference to FIG.

  Specifically, in the range-Doppler image, a signal in this frequency range is suppressed using a frequency filter that suppresses a specific frequency including a fixed clutter as shown in FIG. CFAR detection is performed. Needless to say, this CFAR process may be applied to a one-dimensional CFAR that is divided into a time axis and a frequency axis.

  The present embodiment is a radar apparatus when MPRF is applied. That is, when the speed of the mounted machine is high and the scanning angle is large, the clutter frequency range is widened. In order to widen the clutter-free region, PRF is raised and MPRF in which folding (ambiguity) occurs in both distance and speed is applied. In the case of MPRF, transmission / reception is performed by N PRFs in order to perform distance measurement / speed measurement while avoiding frequency-principles and pulse blinds.

The range / speed measurement in MPRF is the M / N in which the ranges match in the plurality of PRI1 to PRI3 for the plurality of targets A and B on the range axis shown in FIG. 15 and the Doppler axis shown in FIG. The detection is performed by extracting the range where the detection is performed and the Doppler frequency (see Non-Patent Document 6). The relationship between the Doppler frequency fd and the velocity V is as follows.

  As described above, according to the configuration of the third embodiment, by applying MPRF, it is possible to widen the clutter-free region, reliably detect the target, and perform distance measurement / speed measurement.

(Fourth embodiment)
FIG. 17 is a block diagram showing a system configuration of a radar apparatus when HPRF is applied as the fourth embodiment, and FIG. 18 is a flowchart showing a specific processing flow when the processing method is applied. 17 and 18, the same parts as those in FIGS. 8 and 9 are denoted by the same reference numerals.

  This embodiment is different from the third embodiment in that a target cell of the range-Doppler axis obtained by the CFAR processing on the Σ beam side is input to the HPRF ranging / speed measuring unit 3H, and ranging with respect to the target cell is performed by HPRF. In addition, the speed measurement calculation is performed (steps S72 and S75 in FIG. 18).

  That is, when the relative speed between the mounted machine and the target is high, transmission and reception by HPRF may be applied in order to widen the clutter-free area on the Doppler frequency axis. The main lobe clutter frequency in this case can be calculated in the same manner as the equation (11), and the frequency filters 3F1 and 3F2 can be applied. Also in the case of HPRF, in order to avoid pulse blinds, transmission / reception is performed using a plurality of PRFs as necessary. The plurality of PRFs are selected such that the transmission pulses of the transmission / reception signals of each PRF do not overlap as much as possible. If ranging / speed measurement is required after detection, ranging is performed by FMCW (Frequency Modulated Continuous Wave) (see Non-Patent Document 7).

First, the relationship between distance, speed and beat frequency is given by the following equation.

Substituting the observed beat frequency to create simultaneous equations and calculate distance and speed, the following equation is obtained.

  In the case of multiple targets, multiple beat frequencies can be obtained. Therefore, in the beat frequency between multiple sweeps, select the beat frequencies with similar angle values, amplitudes, etc. solve. Alternatively, N is the target number, and the target beat frequency of N + 1 sweep signals is used, the target signal is paired between each sweep, and the simultaneous equations are solved to calculate the target distance and speed. it can.

  That is, as shown in FIG. 19B, a plurality of detection banks are obtained with respect to the sweep 1 and sweep 2 of the modulation scheme shown in FIG. 19A, and banks having different frequencies for the sweep 1 and the sweep 2 are obtained. It is possible to extract a target from

  As described above, according to the configuration of the fourth embodiment, by applying HPRF, it is possible to widen the clutter-free region, thereby detecting a target and performing distance measurement / speed measurement.

  In the third and fourth embodiments, the method of suppressing clutter using a frequency filter in the case of MPRF and HPRF has been described. Needless to say, this technique can suppress clutter by a frequency filter when the spread of clutter is small even in the case of LPRF.

  Note that the present embodiment is not limited to the above-described embodiment as it is, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  DESCRIPTION OF SYMBOLS 1 ... Antenna, 2 ... Transmitter / receiver, 21 ... Transmitter / receiver, 22 ... Beam control unit, 3 ... Signal processor, 311, 312 ... AD (Analog-Digital) converter, 321, 322 ... Range axis FFT unit (FFTx) 331, 332... Range reference signal multiplier 341 342 Data storage unit 351 352 Cross range reference signal multiplier 361 362 Cross range axis FFT unit (FFTy) 371 372 Reverse range axis FFT unit (inverse FFTx), 38 ... CFAR processing unit, 39 ... ranging unit, 3A ... anging unit, 3B ... cell extracting unit, 3C1, 3C2 ... processing selecting unit, 3D ... correction signal extracting unit, 3E ... cross range Reference signal correction unit, 3F1, 3F2 ... frequency filter, 3G ... MPRF ranging / speed measuring unit, 3H ... HPRF ranging / speed measuring unit

Claims (8)

Specify the approximate range of the target position by inputting the radar pulse received signal and applying time-axis coherent integration processing to the range axis of the Σ beam, focus on the approximate range of the target position, and coherent integration of the time axis Σ beam image acquisition means for acquiring the range-Doppler image of the Σ beam by integrating in the frequency domain by FFT (Fast Fourier Transform) processing results and returning to the time domain by inverse FFT processing;
The radar pulse received signal is input and a time axis coherent integration process is performed on the range axis of the Δ beam to identify an approximate range of the target position, focusing on the approximate range of the target position, and coherent on the time axis Δ beam image acquisition means for acquiring the range-Doppler image of Δ beam by integrating in the frequency domain and returning to the time domain for the integration processing result;
The target cell is detected and measured by CFAR (Constant False Alarm Rate) processing for the range-Doppler image of the Σ beam acquired by the Σ beam image acquisition unit, and Δ acquired by the Δ beam image acquisition unit A radar apparatus comprising a range-finding means for measuring an angle using a cell signal corresponding to a target cell detected by the Σ beam from a beam range-Doppler image.   The Σ beam image acquisition means extracts a signal output of a predetermined range of a frequency axis that passes a point exceeding a predetermined amplitude threshold from the result of the range-Doppler image of the Σ beam, and shifts the Doppler frequency to 0. In other cases, the zero-padded signal is inverse FFTed and returned to the time domain, and the input signal to be subjected to the coherent integration process is corrected for each pulse repetition period using the conjugate complex value of the signal in the time domain as a correction coefficient. The radar apparatus according to claim 1, wherein a range-Doppler image is calculated again from the correction result, and this is repeated M times (M ≧ 1) to obtain a final range-Doppler image. The Σ-beam image acquisition means is centered on the Doppler frequency according to the altitude of the mounted machine, the clutter distance, and the beam scanning angle for the transmission / reception signal by MPRF (Middle Pulse Repetition Frequency) having ambiguity on the distance-frequency axis. Obtain a range-Doppler image in which the Doppler frequency range having a predetermined width is suppressed,
The radar apparatus according to claim 1, wherein the distance measurement / angle measurement means uses a plurality of PRFs performed on a target cell obtained by the CFAR process for the distance measurement and angle measurement processing. The Σ beam image acquisition means does not generate velocity axis ambiguity, and transmits and receives signals by HPRF (High Pulse Repetition Frequency) having ambiguity on the distance axis. A range-Doppler image in which a Doppler frequency range having a predetermined width around a Doppler frequency according to the angle is suppressed is acquired,
The distance measurement / angle measurement means uses FMCW (Frequency Modulated Continuous Wave) by a plurality of sweeps performed on the target cell obtained by the CFAR process for the distance measurement and angle measurement processing. Radar equipment. Specify the approximate range of the target position by inputting the radar pulse received signal and applying time-axis coherent integration processing to the range axis of the Σ beam, focus on the approximate range of the target position, and coherent integration of the time axis About the processing result, an integration process in the frequency domain is performed by FFT (Fast Fourier Transform) processing, and a range-Doppler image of Σ beam is acquired by returning to the time domain by inverse FFT processing,
The radar pulse received signal is input and a time axis coherent integration process is performed on the range axis of the Δ beam to identify an approximate range of the target position, focusing on the approximate range of the target position, and coherent on the time axis The integration process result is integrated in the frequency domain and returned to the time domain to obtain a Δ beam range-Doppler image,
The target cell is detected and measured by CFAR (Constant False Alarm Rate) processing on the range-Doppler image of the Σ beam and corresponds to the target cell detected by the Σ beam from the range-Doppler image of the Δ beam. A radar signal processing method of a radar apparatus that measures an angle using a signal of a cell to be operated.   From the result of the range-Doppler image of the Σ beam, the signal output of the frequency axis in a predetermined range passing through the point exceeding the predetermined amplitude threshold is extracted, the Doppler frequency is shifted to 0, and the others are filled with 0. The signal is inverse FFTed and returned to the time domain, and the input complex signal is corrected for each pulse repetition period using the conjugate complex value of the signal in the time domain as a correction coefficient, and the range-Doppler image is again obtained from the correction result. 6. The radar signal processing method for a radar apparatus according to claim 5, wherein the final range-Doppler image is acquired by repeating the calculation M times (M ≧ 1). The range-Doppler image of the Σ beam shows the Doppler frequency according to the altitude, clutter distance, and beam scanning angle of the mounted machine for the transmission / reception signal by MPRF (Middle Pulse Repetition Frequency) having ambiguity in the distance-frequency axis. Obtained by suppressing the Doppler frequency range with a predetermined width as the center,
The radar signal processing method of a radar apparatus according to claim 5 or 6, wherein a plurality of PRFs used for a target cell obtained by the CFAR processing are used for the ranging and angle measurement processing. The range-Doppler image of the Σ beam does not generate ambiguity of the velocity axis, and transmits and receives signals by HPRF (High Pulse Repetition Frequency) having ambiguity on the distance axis. Obtained by suppressing a Doppler frequency range having a predetermined width around the Doppler frequency according to the beam scanning angle,
7. The radar signal processing method of a radar apparatus according to claim 5, wherein FMCW (Frequency Modulated Continuous Wave) based on a plurality of sweeps performed on the target cell obtained by the CFAR process is used for the ranging and angle measurement processes.

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