JP5491877B2 - Radar apparatus, flying object guidance apparatus, and target detection method - Google Patents

Description

  The present invention relates to a radar apparatus, a flying object guidance apparatus, and a target detection method that use a plurality of different frequencies.

  As a method for improving the accuracy of radar ranging, there is a synthetic band radar (Non-Patent Document 1). The band synthesis radar is a method in which the frequency of the chirped pulse radar is discretized and the distance is measured by changing the frequency stepwise. In general, as described in Non-Patent Document 1, it is often performed by a short pulse radar. However, as described in Non-Patent Document 2 and Patent Document 1, a method of using each pulse as a chirp pulse has also been proposed. Yes. By making each pulse a chirp pulse, it is possible to lengthen the time of one pulse and increase the energy of the pulse while maintaining the bandwidth, that is, without reducing the range resolution.

  When performing multiple target separation detection in the short pulse synthesis band, the target is separated for each moving speed, that is, for each Doppler frequency, and further for each separated Doppler frequency at the stage of Fourier transforming the multiple pulses for each same frequency step. When the composite waveform range waveform is calculated and a plurality of peaks are included in the range waveform, each is detected as a different target.

  When each pulse is a chirp pulse, after separating the target for each peak of the waveform after pulse compression before the stage of separating the target for each Doppler frequency, the target separation and synthesis by the Doppler frequency is performed in the same way as for the short pulse. Performs target separation by band range waveform. That is, a plurality of targets are separated in three stages.

  Regarding detection of the Doppler frequency of a chirp pulse, for example, as described in Patent Document 2, after compressing a chirp pulse, it is known that the Doppler frequency can be calculated by Fourier transforming the compression results of a plurality of pulses for each range bin. It has been.

JP 2009-257884 Japanese Patent Laid-Open No. 4-188089 Donald R. Wehner, “High-Resolution Radar,” ch.5, Artech House Radar Library Series (1987, 1st edition, 1994, 2nd edition,) D.J. Rabideau, “Nonlinear synthetic wideband waveforms”, IEEE Radar Conference 2002, pp.212-219

  By the way, when demodulating a chirp pulse, the pulse compression waveform is not a perfect impulse, but a slightly broad waveform, so if multiple targets are mixed at a short distance, depending on the relationship between the resolution of the chirp pulse and the distance The peak may not be detected by the number of targets. Of the waveform after pulse compression, only the range bin component corresponding to the peak of the waveform is sent to the subsequent synthesis band, so the target that does not contain the component in the peak of the pulse compression waveform is also detected in the subsequent synthesis band. It is not possible to take advantage of the synthetic bandwidth.

  That is, although the synthesis band is originally a method for realizing high-range resolution, there is a problem that high-resolution multi-target separation cannot be realized due to restrictions on the resolution at the chirp pulse stage.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a radar apparatus capable of realizing a synthetic band radar using one pulse as a chirp pulse without impairing the range resolution of the step frequency synthetic band radar and the performance of separating multiple targets, and a flying object using this radar apparatus. The object is to provide a guidance device and a target detection method.

  In order to achieve the above object, a radar apparatus according to the present invention receives a reflected wave of a chirp pulse having a center frequency changed stepwise for each predetermined number of pulses arriving from a target, and converts it into a digital baseband signal. Receiver and digital baseband signal for each pulse, pulse compression is performed, the pulse compression range for each peak of the waveform after pulse compression is detected, and each pulse representative value for each peak of the waveform after pulse compression is extracted One or more relative velocities are detected from the pulse representative value extracting unit and the pulse representative value from the Doppler frequency that can be detected by the pulse representative value. The frequency step representative value extraction unit that extracts each frequency step representative value, and the synthesized band range wave from the frequency step representative value corrected using the relative speed And a synthetic band range detector that detects each target range from each peak, and the pulse representative value extractor uses n (n is a natural number) sample points as the frequency of the digital baseband signal. Fourier transform means for converting to an axis signal, compression coefficient multiplication means for multiplying the output of the Fourier transform means by a compression coefficient, and inverse Fourier transform of the output of the compression coefficient multiplication means, given by n sample points And an arithmetic means for calculating a component between signal sample points after the inverse Fourier transform.

  According to this configuration, the peak detection performance at the chirp pulse stage is improved by calculating the component between the signal sample points of the waveform after pulse compression, and the chirp pulse is generated in the synthesis band without impairing the range resolution of the synthesis band. Can be used in combination.

  In addition, when performing the inverse Fourier transform, the arithmetic means adds a plurality of zero points outside the spectrum sample after the multiplication by the pulse compression coefficient, and then calculates the component between the signal sample points by performing the inverse Fourier transform. .

  According to this configuration, the components between the signal sample points of the waveform after pulse compression can be easily performed by adding a plurality of zero points outside the spectrum sample after multiplication by the pulse compression coefficient and executing inverse Fourier transform processing. As a result, the peak detection performance at the chirp pulse stage is improved, and it is possible to use the chirp pulse in the synthesis band without impairing the range resolution of the synthesis band.

  When performing the inverse Fourier transform, the arithmetic means performs the inverse Fourier transform at the n point, and then performs the inverse Fourier transform within the range where the target peak is expected to be detected in the pulse-compressed waveform after the inverse Fourier transform. Any component between the generated signal sample points is calculated by inverse discrete Fourier transform.

  According to this configuration, when the range where the target peak exists within a relatively narrow range is limited from the beginning, it is not necessary to perform the inverse Fourier transform on all the samples at the time of pulse compression, and it is generated by the inverse Fourier transform. As described above, the peak detection performance at the chirp pulse stage is improved and the range resolution of the synthesis band is not impaired by calculating any component between the obtained signal sampling points by inverse inverse Fourier transform. It is possible to use a chirp pulse in the synthesis band.

  The computing means calculates the waveform component after pulse compression in the range where the target peak is expected to be detected by discrete inverse Fourier transform specifying the reference time.

  According to this configuration, for the specified reference time, the waveform component after pulse compression in a range where the target peak is expected to exist is calculated by discrete inverse Fourier transform, thereby reducing the number of arithmetic processing and reducing the number of chirp pulses. The peak detection performance at the stage can be improved, and a chirp pulse can be used in the synthesis band without impairing the range resolution of the synthesis band.

  According to another aspect of the present invention, there is provided a flying object guidance device including the radar device and a guidance signal generation unit that generates a guidance signal for guiding the flying object using a relative speed and a range that are output from the radar device. It is a thing.

  According to this configuration, it is possible to guide the flying object with higher accuracy by using the target detection result obtained by the radar device.

  According to the above invention, a radar apparatus capable of realizing a synthetic band radar using a single pulse as a chirp pulse without impairing the range resolution of the step frequency synthetic band radar and the performance of separating multiple targets, and a flying object guidance apparatus using this radar apparatus And a target detection method can be provided.

1 is a block diagram showing an embodiment of a radar apparatus according to the present invention. The figure which shows the structure of the pulse train of a chirp pulse. 5 is a flowchart showing a control processing procedure of a pulse compression / representative value extraction unit, a speed detection / frequency step representative value extraction unit, and a combined band range detection unit in the embodiment. The figure which shows the flow of multiple target detection in the embodiment. The figure which shows an example of the waveform after the pulse compression in the same embodiment. The figure for demonstrating a short time Fourier transform. The figure for demonstrating an example in the case of applying a window function when performing short time. The block diagram which shows the structure in the case of performing a short time inverse Fourier transform in the interpolation IFFT part shown in the said FIG. The block diagram which shows the structure of the interpolation IFFT part in the case of determining the range to interpolate from the waveform after IFFT. The block diagram which shows the structure of the interpolation IFFT part in the case of performing a discrete Fourier-transform process about the designated range. The block diagram which shows other embodiment of the radar apparatus which concerns on this invention. The block diagram which shows embodiment of the flying body guidance apparatus which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiment, only the part directly related to the operation of the present invention is described, and the rest are omitted.

  FIG. 1 is a diagram showing an embodiment of a radar apparatus according to the present invention. The radar apparatus 1 of the present embodiment is a tracking radar that has a known distance to a target, that is, a range to some extent, and tracks a detailed distance.

  The radar apparatus 1 is a synthetic band radar, and includes an antenna 2, a circulator 3, a transmission unit 4, and a reception RF (Radio Frequency) unit 5. The radar apparatus 1 transmits a chirp pulse generated by the transmitter 4 and having a center frequency changed stepwise for each predetermined number of pulses from the antenna 2 to the space via the circulator 3. The chirp pulse has a pulse train configuration as shown in FIG.

  In FIG. 2, the horizontal axis is time, and the vertical axis is frequency. Each square represents a pulse, and each pulse is a chirp pulse whose frequency changes with time in the pulse. Such pulses are transmitted in N pulses at a predetermined PRI (Pulse Repetition Interval) at the same frequency step. This is repeated for a predetermined M frequency steps while changing the frequency at a predetermined frequency step interval. One measurement period, that is, 1 CPI (Coherent Processing Interval) is configured by N × M pulses.

  The chirp pulse transmitted from the radar apparatus 1 is reflected by the target and received by the antenna 2. A signal input to the antenna 2 is supplied to the reception RF unit 5 via the circulator 3. In the reception RF unit 5, the reception signal is amplified, down-converted to baseband, converted from analog to digital, and converted into a digital signal.

  The output of the same oscillator 17 is supplied to the reception RF unit 5 and the transmission unit 4, and the local signal used when down-converting a certain pulse is a local signal synchronized with the local signal used when generating the pulse. It is. That is, pulses of different frequency steps are frequency-converted to baseband at local frequencies corresponding to the respective frequency steps.

  The received signal converted into the digital signal is supplied to the pulse compression / representative value extraction unit 14. Then, the pulse compression / representative value extraction unit 14 executes the control processing procedure shown in FIG.

  In the pulse compression / representative value extraction unit 14, first, the FFT unit 6 extracts a certain number of samples in a period in which the target reflected wave is expected to exist and performs a Fourier transform process to convert the frequency axis signal from the time axis signal. And output to the compression coefficient multiplier 7 (step ST3a). In the FFT unit 6, the number of samples in the Fourier transform is n points. The compression coefficient multiplication unit 7 calculates whether or not a compression coefficient corresponding to the chirp pulse specification of the radar apparatus 1 is prepared in advance, and multiplies the compression coefficient by necessity (step ST3b).

  The received signal multiplied by the compression coefficient is output to the interpolation IFFT unit 8. The interpolation IFFT unit 8 performs an inverse Fourier transform process on the signal multiplied by the compression coefficient and returns it to the time axis signal (step ST3c). The output of the interpolation IFFT unit 8 is not a chirp pulse having a long original pulse length but a waveform close to a pulse-compressed impulse because it is multiplied by a compression coefficient.

  In addition, the interpolation IFFT unit 8 calculates the value of the point between the sample points of the waveform obtained when the inverse Fourier transform is normally performed at n points at least in the range where the peak detection is performed at the later stage. By calculating, a detailed pulse-compressed waveform is generated. This pulse-compressed waveform is supplied to the peak detector 9.

  Subsequently, the peak detector 9 detects a peak from the pulse-compressed waveform (step ST3d). That is, a peak having a height exceeding a predetermined peak detection threshold is detected from peaks existing in a target range that is approximately known in advance.

  Although no peak may be detected at this stage, it is assumed that at least one or more peaks are detected because the radar according to the present embodiment is a following radar as described above. If no peak is detected at all, it is necessary to switch to search mode or estimate the target range using tracking from past results, but such processing is not related to the contents of this embodiment. Therefore, it is omitted.

  The peak position information detected by the peak detection unit 9 is supplied to the range detection unit 10. The range detector 10 converts the input peak position into a range (distance to the target) and outputs it (step ST3e). The range estimated here is combined with the range of the synthesis band later to estimate the total range and output as an estimation result.

  The output of the peak detection unit 9 is further input to the representative value extraction unit 11. The representative value extraction unit 11 extracts the complex value of the peak position of the compressed pulse, that is, the phase and amplitude, as a pulse representative value for one or more peaks detected by the peak detection unit 9 (step ST3f). Since the pulse representative value is used in the synthesis band, it is output to the subsequent speed detection / frequency step representative value extraction unit 15.

  Note that the pulse compression / representative value extraction unit 14 is a block that performs digital signal processing, and is mounted on a DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), ASIC, or other component that performs digital signal processing. It is implemented as a program. Therefore, each detailed block in the pulse compression / representative value extraction unit 14 is a convenience for explaining the operation, and it is not always necessary to perform the block division as described above.

In the present embodiment, since the processing of the synthesis band itself has no characteristics, the synthesis band will be briefly described below.
First, the speed detection / frequency step representative value detection unit 15 detects the target moving speed from the pulse representative value output from the pulse compression / representation value extraction unit 14. The demodulated result of a plurality of pulses of the same frequency step is Fourier transformed with the pulse representative values of the plurality of pulses of the same frequency step in this embodiment (step ST3g), and a plurality of peaks on the frequency axis after the conversion are detected ( In step ST3h), the Doppler frequency of the target reflected wave is detected from these peak values (step ST3i), and this is converted into a moving speed. At this stage, a plurality of peaks may be detected exceeding the Doppler detection threshold value. In this case, they are detected individually as individual targets. For each peak, its phase and amplitude are extracted as the frequency step representative value of that peak.

  When each frequency step representative value is extracted for each peak, these values are sent to the synthesis band range detector 16 (step ST3j). The synthesized band range detection unit 16 first corrects the frequency step representative value in accordance with the detected moving speed (step ST3k). The details of the correction are publicly known and will not be described in detail here. Simply, it is a process of correcting the change of the target range during 1 CPI.

  The corrected step representative values are arranged in the order of the frequency of the frequency step and subjected to inverse Fourier transform (step ST31). The result of the inverse Fourier transform is an impulse waveform indicating the range, and the range of the result of the synthesis band is detected from the peak (step ST3m). However, since the synthesis band is range detection based on discrete frequency information, the waveform is repeated in a range range corresponding to the frequency step interval. For example, at a frequency step interval of 10 MHz, 30 m, which is a wavelength of 10 MHz, corresponds to a round trip distance that can be measured. Accordingly, the measurable range is 15 m if it is 10 MHz, and the waveform is repeated every 15 m. In most cases, since such a distance range is too short, the total distance is determined together with the range obtained as a result of the distance measurement using the pulses before the synthesis band.

  In the present embodiment, the range is detected by the range detector 10 at the chirp pulse stage. At the chirp pulse stage, the bandwidth of individual pulses is narrower than the total bandwidth of the synthesis band, so the resolution is also proportionally coarse. Therefore, the range closest to the range detected by the chirp pulse among the repeated synthesis band ranges is output as the target total range.

  Even in the range detection process of the composite band, a plurality of peaks may be detected exceeding the range detection threshold. In such a case, each peak is detected as a separate target.

  FIG. 4 shows the flow of multi-target detection. Each peak separated by pulse compression is sent to the Doppler frequency detection step ST4a, and further separated by Doppler frequency detection into a plurality of peaks, and the separated peaks are individually detected in the range of the synthesis band. Further, it is separated into a plurality of peaks (step ST4b). In FIG. 4, n peaks are finally detected, but in some cases, the same target may appear in a different shape. In such a case, it is necessary to perform such fusion processing, which is omitted because it is not related to the contents of the present embodiment.

  Next, an operation of a part that is a feature of the present embodiment will be described. FIG. 5 is an example of a waveform after pulse compression, which is a waveform obtained as a result of pulse compression of a reception signal in which pulses having substantially the same power reflected by two point targets A and B slightly different in distance are combined. The vicinity including the peaks of the targets A and B is extracted.

  FIG. 5A shows a case where the number of points at the time of Fourier transform is n and the number of points at the time of inverse Fourier transform is also n. A peak is detected for point target A, but point target B is not detected as a peak because there is a peak between bins after inverse Fourier transform. Therefore, the peak that can be detected by performing peak detection from this waveform is only the peak indicated by the arrow of the point target A.

  Here, even if the peak of the point target A is detected, the phase and amplitude of the peak position are extracted as pulse representative values, and the speed of the combined band is detected, the point indicated by the arrow of the point target A is The component of A is included, but the component of the point target B is not sufficiently included. Therefore, there is no guarantee that the component of the point target B exceeds the detection threshold at the time of detecting the peak of the Doppler spectrum.

  On the other hand, FIG. 5B shows a waveform when a value between bins is calculated by applying a short-time inverse Fourier transform in which the sampling points are quadrupled at the time of inverse Fourier transform of pulse compression. Since the short-time inverse Fourier transform is four times the number of points, three points are calculated between the bins in FIG. As a result, in FIG. 5A, it can be seen that the peak of the point target B that has not been peaked between the bins appears and can be clearly distinguished from the peak of the point target A.

  By doing this, even if one pulse in the synthesis band is a chirp pulse, it can be detected without overlooking the peak at the stage of the chirp pulse, and the target range without compromising the high resolution of the synthesis band Detection is possible.

  Next, a method for calculating the value of a point between the range bins will be described. First, a method using short-time inverse Fourier transform will be described.

  FIG. 6 is a diagram for explaining the short-time Fourier transform. There is a section indicated by “original signal”, which is a signal composed of n samples, for example. Outside this, in many cases, multiple sample zeros are added to the back of the signal. In many cases, an integer multiple of zero is added to the original signal number. Fourier transform, and fast Fourier transform (FFT) processing is performed in some cases as a whole frame indicated by “FFT section” with zero added.

  If the total number of samples is quadrupled by adding 3n zeros, the Fourier transform score is quadrupled. Accordingly, the number of points after the Fourier transform is quadrupled. On the other hand, since the bandwidth after Fourier transform is determined by the sample interval of the signal, the bandwidth after Fourier transform is unchanged unless the sample interval is changed. Further, the sample interval after Fourier transform is determined by the frame length at the time of Fourier transform. Therefore, by performing the short time Fourier transform, it is possible to finely take the sample interval of the spectrum after the Fourier transform.

  Note that the transformation used in the interpolation IFFT according to the present embodiment is an “inverse” Fourier transformation performed by adding zero to the outside of the spectrum, and is not a Fourier transformation. However, the Fourier transform and the inverse Fourier transform are almost the same process, only the phase at the time of correlation is inverted. The short-time inverse Fourier transform adds zero to the outside of a significant spectral component and lengthens the frame length to perform the inverse Fourier transform, and the principle and operation are exactly the same for the short-time part. .

  At the time of inverse Fourier transform of pulse compression, in order to suppress spurious waveforms after compression, the inverse Fourier transform is usually performed after applying a window function to the spectrum. When a window function is applied when performing a short time, an appropriate window function waveform 13 having a corresponding length is applied to the section of the original signal 12, as shown in FIG. However, when a window function waveform having zeros at both ends is used as the window function waveform 13, a window function is generated so that the section obtained by removing the zeros at both ends coincides with the original signal section. Multiply it. This is because the zero added to perform the short time plays a role of zero at both ends of the window.

  Since the purpose is to output the value between bins, the zero score added when performing the short-time inverse Fourier transform is at least the same as the original signal score, In this example, it is desirable to calculate at least one component between bins by adding at least n zeros. Of course, zero or more n points may be added.

  FIG. 8 shows a configuration when short-time inverse Fourier transform is performed by the interpolation IFFT unit 8. The spectrum signal input to the interpolating IFFT unit 8 is zero-added with an appropriate length by the zero adding unit 18, and the spectrum with the zero added is subjected to inverse Fourier transform by the IFFT unit 19 to be pulse-compressed and output. Is done.

  As another method for calculating the component between bins, there is a method using IDFT (Discrete Inverse Fourier Transform).

  For example, the number of points before pulse compression is 256, but as can be seen from FIG. 5A, the range for detecting the range is a range of several samples at most. Compared to DFT and IDFT, FFT and IFFT are very fast in processing. However, if the number of points to interpolate between bins is at most several, the point to be interpolated The method of selecting ID and applying IDFT may have less processing.

  FIG. 9 shows the configuration of the interpolation IFFT unit 8 when applying IDFT. There are two configurations depending on which part the range range that needs to be interpolated is estimated.

  FIG. 9 shows a case where the interpolation range is determined from the waveform after IFFT. The spectrum signal input to the interpolation IFFT unit 8 is branched into two, and one is input to the IFFT unit 20. If the original signal is n points, the IFFT unit 20 executes the inverse Fourier transform process while keeping the n points.

  The result of the inverse Fourier transform is first sent to the target range detection unit 23, and the range including the peak is specified. The target range detection unit 23 further determines a point to be interpolated by applying IDFT within a range including the specified peak. The determined point is supplied to the IDFT unit 22. The input to the interpolation IFFT unit 8 is branched and input to the IDFT unit 22, and IDFT at a specified point is performed on the input and output to the synthesis unit 21. The synthesizer 21 synthesizes the output of the IDFT unit 22 and the output of the IFFT unit 20 to generate and output an interpolated pulse-compressed waveform.

An equation for applying IDFT will be briefly described. The spectrum before the inverse Fourier transform after the multiplication by the compression coefficient is expressed as the following equation.

Where N _s is the sample rate, T is the pulse round trip time in the target range and is detected after the synthesis band, and T _p is the time from the gate start time for sampling the chirp pulse to the beginning of the chirp pulse. It is a range detected at the stage of pulse compression. ω ₀ is the RF frequency at the beginning of the pulse when the pulse is transmitted, and N ₃ is the number of samples when Fourier transform is performed. A is the target amplitude. m is a frequency bin number. When this is multiplied by the inverse Fourier transform for the range bin number k, the inverse Fourier transform coefficient is as follows.

  In normal FFT, k does not take a value other than an integer. However, k does not need to be an integer as long as the calculation shown in Equation (2) is directly performed. Therefore, on the horizontal axis in FIG. 5A, the range bin number, for example, the number between bins such as 0.5, 1.5, 2.5 is designated as k, and the inverse Fourier transform coefficient is obtained from equation (2). Thus, the component between the bins can be obtained.

  If the range in which the peak exists in a relatively narrow range is limited from the beginning, it is not necessary to perform inverse Fourier transform on all points during pulse compression. Therefore, the component may be obtained by discrete inverse Fourier transform only in the range where the peak is estimated to exist.

  FIG. 10 shows the configuration of the interpolation IFFT unit 8 when the discrete Fourier transform process is executed for the designated range. A plurality of points to which IDFT within a range where it is estimated that the target exists is input from the terminal 24. The IDFT unit 22 performs IDFT on the spectrum signal input from the previous stage at a specified point, and generates and outputs a waveform in a range where a peak is estimated to exist.

  As described above, the interpolated IFFT unit 8 may calculate the waveform component after pulse compression in a range where the target peak is expected to be detected by discrete inverse Fourier transform designating the reference time.

  In this way, for the specified reference time, the waveform component after pulse compression in the range where the target peak is expected to exist is calculated by the discrete inverse Fourier transform, thereby reducing the number of arithmetic processing and reducing the chirp pulse. The peak detection performance at the stage can be improved, and a chirp pulse can be used in the synthesis band without impairing the range resolution of the synthesis band.

Note that equation (3) is an equation describing the coefficient part for obtaining the inverse Fourier transform coefficient, but the short-time inverse Fourier transform said that the value of N ₃ in equation (3) was doubled or quadrupled. This is a method of equivalently realizing the fractional k by increasing the value.

  As described above, in the above embodiment, the chirp pulse that has arrived from the target and received by the antenna 2 is Fourier-transformed by the FFT unit 6 for each pulse, the compression coefficient multiplication unit 7 multiplies the compression coefficient, and the interpolation IFFT unit. At step 8, a plurality of zero points are added outside the spectrum sample after the multiplication by the pulse compression coefficient, and the inverse Fourier transform process is executed.

  Therefore, the component between signal sample points (between bins) of the waveform after pulse compression is easily calculated, thereby improving the peak detection performance at the chirp pulse stage and impairing the range resolution of the synthesis band. It is possible to use a chirp pulse in the synthesis band without any problem.

  Further, in the above embodiment, when performing the inverse Fourier transform in the interpolation IFFT unit 8, it is expected that the target peak is detected from the pulse-compressed waveform after the inverse Fourier transform after performing the inverse Fourier transform at n points. In such a range, any component between signal sample points generated by inverse Fourier transform is calculated by discrete inverse Fourier transform.

  Therefore, when the range in which the target peak exists in a relatively narrow range is limited from the beginning, it is not necessary to perform inverse Fourier transform on all samples during pulse compression, and signal samples generated by inverse Fourier transform By calculating one of the components between the points by discrete inverse Fourier transform, the peak detection performance at the chirp pulse stage is improved and the chirp pulse in the synthesis band is not lost, without losing the range resolution of the synthesis band. Can be used in combination.

  FIG. 11 is a diagram showing another embodiment of the radar apparatus according to the present invention. Although it is almost the same as FIG. 1, it has a transmission-only form without a transmission unit. As a radar system, in addition to an active type in which a transmission unit and a reception unit are mounted on the same device, there is a bistatic type in which the transmission unit and the reception unit are mounted on different devices and arranged at different positions. FIG. 11 shows a mode when the invention of the present application is mounted on a receiver of a bistatic radar. The difference from FIG. 1 except that it does not have a transmitter is that the antenna 25 is a receiving antenna, and does not have an oscillator synchronized with the transmitter, and an oscillator (not shown) is provided in the reception RF unit 26. It is that you are. Others are the same as in FIG.

  FIG. 12 is a block diagram showing an embodiment of the flying object guiding apparatus according to the present invention. The output of the radar apparatus 1 of the present invention and the outputs of the other N sensors 26-1 to 26 -N are input to the guidance signal generator 27. The guidance signal generation unit 27 generates a guidance signal for guiding a flying object on which the radar apparatus 1 of the present invention is mounted, and outputs the guidance signal to the flying object steering apparatus 28. By mounting the radar apparatus 1 of the present invention on the flying object guiding apparatus 30, it becomes possible to perform more accurate flying object guidance.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the 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 ... Radar apparatus, 2 ... Antenna, 3 ... Circulator, 4 ... Transmission part, 5 ... Reception RF part, 6 ... FFT part, 7 ... Compression coefficient multiplication part, 8 ... Interpolation IFFT part, 9 ... Peak detection part, 10 ... Range detection unit, 11 ... representative value extraction unit, 14 ... pulse compression / representative value extraction unit, 15 ... speed detection / frequency step representative value extraction unit, 16 ... synthesized band range detection unit, 17 ... oscillator, 18 ... zero addition unit , 22 ... IDFT section, 23 ... target range detection section, 26-1 to 26 -N ... sensor, 27 ... guidance signal generation section, 28 ... steering apparatus, 30 ... flying object guidance apparatus.

Claims (8)

A receiving unit that receives a reflected wave of a chirp pulse in which the center frequency is changed stepwise for each predetermined number of pulses that have arrived from the target, and converts the received signal into a digital baseband signal;
A pulse representative value that performs pulse compression on the digital baseband signal for each pulse, detects a pulse compression range for each peak of the waveform after pulse compression, and extracts each pulse representative value for each peak of the waveform after pulse compression An extractor;
From the pulse representative value, one or more relative velocities are detected from the Doppler frequency that can be detected by the pulse representative value, and each frequency step representative value is determined for each relative speed from a plurality of pulses of the same frequency step within one measurement period. A frequency step representative value extraction unit to extract;
Calculating a combined band range waveform from the frequency step representative value corrected using the relative speed, and comprising a combined band range detecting unit that detects each target range from each peak;
The pulse representative value extraction unit includes:
Fourier transform means for transforming the digital baseband signal into a frequency axis signal at n (n is a natural number) sample points;
Compression coefficient multiplication means for multiplying the output of the Fourier transform means by a compression coefficient;
An arithmetic unit for performing an inverse Fourier transform on the output of the compression coefficient multiplying unit and calculating a component between signal sample points after the inverse Fourier transform given by the n sample points;
When the inverse Fourier transform is performed, the arithmetic means performs an inverse Fourier transform in a range where a target peak is expected to be detected in a pulse-compressed waveform after the inverse Fourier transform after performing the inverse Fourier transform at n points. A radar apparatus , wherein any component between signal sample points generated by transformation is calculated by discrete inverse Fourier inverse transformation .   The radar apparatus according to claim 1, further comprising: a transmission unit that transmits a chirp pulse by changing the center frequency stepwise for each predetermined number of pulses. A receiving unit that receives a reflected wave of a chirp pulse in which the center frequency is changed stepwise for each predetermined number of pulses that have arrived from the target, and converts the received signal into a digital baseband signal;
A pulse representative value that performs pulse compression on the digital baseband signal for each pulse, detects a pulse compression range for each peak of the waveform after pulse compression, and extracts each pulse representative value for each peak of the waveform after pulse compression An extractor;
From the pulse representative value, one or more relative velocities are detected from the Doppler frequency that can be detected by the pulse representative value, and each frequency step representative value is determined for each relative speed from a plurality of pulses of the same frequency step within one measurement period. A frequency step representative value extraction unit to extract;
Calculating a combined band range waveform from the frequency step representative value corrected using the relative speed, and comprising a combined band range detecting unit that detects each target range from each peak;
The pulse representative value extraction unit includes:
Fourier transform means for transforming the digital baseband signal into a frequency axis signal at n (n is a natural number) sample points;
Compression coefficient multiplication means for multiplying the output of the Fourier transform means by a compression coefficient;
Computation means for performing discrete inverse Fourier transform specifying a reference time on the output of the compression coefficient multiplication means to generate and output a waveform component after pulse compression in a range where a target peak is expected to be detected. Radar apparatus characterized by the above. The radar apparatus according to claim 3, further comprising: a transmission unit that transmits a chirp pulse by changing the center frequency stepwise for each predetermined number of pulses.   A flying object guidance comprising: the radar apparatus according to claim 1; and a guidance signal generation unit that generates a guidance signal for guiding the flying object using a relative speed and a range that are outputs of the radar apparatus. apparatus. 4. A flying object guidance comprising: the radar apparatus according to claim 3; and a guidance signal generation unit that generates a guidance signal for guiding the flying object using a relative speed and a range that are outputs of the radar apparatus. apparatus. In a target detection method used in a radar apparatus having a receiving unit that receives a reflected wave of a chirp pulse in which a center frequency is changed in a stepwise manner for each predetermined number of pulses that have arrived from a target, and converts the received signal into a digital baseband signal.
The digital baseband signal is converted into a frequency axis signal at n sample points (n is a natural number) in order to compress the digital baseband signal for each pulse,
Multiply this Fourier transform output by a compression factor,
Inverse Fourier transform the multiplication result to calculate a component between signal sample points after inverse Fourier transform given by the n sample points;
Detecting the pulse compression range for each peak of the calculated waveform after pulse compression, and extracting each pulse representative value for each peak of the waveform after pulse compression;
From the pulse representative value, one or more relative velocities are detected from the Doppler frequency that can be detected by the pulse representative value, and each frequency step representative value is determined for each relative speed from a plurality of pulses of the same frequency step within one measurement period. Extract and
Calculate the composite band range waveform from the frequency step representative value corrected using the relative speed, detect the range of each target from each peak ,
The calculation of the component between the signal sample points means that when performing the inverse Fourier transform, after performing the inverse Fourier transform at the n point, the target peak is detected in the pulse-compressed waveform after the inverse Fourier transform. A target detection method characterized by calculating any component between signal sample points generated by an inverse Fourier transform by an inverse discrete Fourier transform within an expected range . In a target detection method used in a radar apparatus having a receiving unit that receives a reflected wave of a chirp pulse in which a center frequency is changed in a stepwise manner for each predetermined number of pulses that have arrived from a target, and converts the received signal into a digital baseband signal
The digital baseband signal is converted into a frequency axis signal at n sample points (n is a natural number) in order to compress the digital baseband signal for each pulse,
Multiply this Fourier transform output by a compression factor,
A discrete inverse Fourier transform that designates a reference time for the multiplication result is performed, and a pulse-compressed waveform component in a range where a target peak is expected to be detected is generated and output,
Detecting the pulse compression range for each peak of the calculated waveform after pulse compression, and extracting each pulse representative value for each peak of the waveform after pulse compression;
From the pulse representative value, one or more relative velocities are detected from the Doppler frequency that can be detected by the pulse representative value, and each frequency step representative value is determined for each relative speed from a plurality of pulses of the same frequency step within one measurement period. Extract and
A target detection method of calculating a composite band range waveform from the frequency step representative value corrected using the relative speed and detecting a range of each target from each peak.

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