JP2011163962A - Pulse-doppler radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pulse-Doppler radar device for enabling target detection by a transmitted pulse of high PRF even when the frequencies of a clutter and a target overlap each other. <P>SOLUTION: This pulse-Doppler radar device includes a distance measurement section for observing first and second frequencies of the target based on the frequency transition based on distance delay, and measuring the target distance based on the observed first and second frequencies of the target by performing first frequency modulation by first linear frequency modulation in the first phase, and then performing second frequency modulation by second linear frequency modulation of a time variation rate larger than that of the first linear frequency modulation in the second phase. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pulse Doppler radar device that is mounted on a moving body such as an aircraft or a vehicle, outputs a transmission pulse having a high PRF (Pulse Repetition Frequency), and measures a distance to a target.

  In a conventional pulse Doppler radar device (hereinafter referred to as a high PRF pulse Doppler radar device) that outputs a high PRF transmission pulse, an FM (Frequency Modulation) ranging technique is used to measure the distance to a target. In this technology, after measuring the target Doppler frequency in the target search phase, the radar transmission signal is continuously linearly frequency modulated in the distance measurement phase, and the reflected signal from the target is the same frequency modulated signal as the transmission signal. Is used to extract the frequency shift based on the distance delay and calculate the distance from the frequency modulation speed (see Non-Patent Document 1, for example).

  FIG. 4 is a diagram illustrating a configuration example of a conventional high PRF pulse Doppler radar apparatus. In FIG. 4, a high PRF pulse Doppler radar apparatus includes a frequency modulation controller (1) 101, a transmitter 2, an antenna 3, a receiver 4, an A / D (Analog to Digital) converter 5, a filter. Means 6, frequency analysis means 7, target detection means 8, distance measurement means (1) 109, and phase controller (1) 110 are provided. Here, the A / D converter 5, the filter unit 6, the frequency analysis unit 7, and the target detection unit 8 constitute a target search unit 11. The A / D converter 5, the filter means 6, the frequency analysis means 7, the target detection means 8, the frequency modulation controller (1) 101, and the distance measurement means (1) 109 are included in the distance measurement unit 12. Is configured.

  In the target search phase, a transmission signal (transmission pulse) that is not subjected to frequency modulation is generated from the transmitter 2 under the control of the phase controller (1) 110, and is radiated from the antenna 3 into space. A reflected signal from the target is received by the antenna 3, and the received signal is detected by the receiver 4 by the same signal as the transmission signal and converted into a video signal. The target search unit 11 converts the video signal into a digital video signal by the A / D converter 5, performs necessary band limitation by the filter unit 6, and then performs frequency analysis by the frequency analysis unit 7. Since the target signal has only a single component in frequency, it is integrated to a specific frequency by frequency analysis. The target detection means 8 uses a method such as CFAR (Constant False Alarm Rate) shown in Non-Patent Document 2 to detect a target from the frequency analysis result and target Doppler frequency fa (Hz) in the target search phase. Is observed.

  After the target is detected in the target search phase, the distance is measured by the following method in the distance measurement phase. By the control from the phase controller (1) 110, the frequency modulation controller (1) 101 performs control for performing linear frequency modulation on the transmission signal (transmission pulse), and the frequency modulation is performed by the transmitter 2. A transmission signal is generated. Similar to the target search phase, a transmission signal is radiated from the antenna 3 into space. A reflected signal from the target is received by the antenna 3, and the received signal is detected by the receiver 4 using the same frequency modulation signal as the frequency modulation applied to the transmission signal and converted into a video signal. . In the distance measuring unit 12, the video signal is processed by the A / D converter 5 and the filter unit 6, frequency-analyzed by the frequency analyzing unit 7, and then operated until the target is detected by the target detecting unit 8. The same as the target search phase. However, since frequency modulation is applied to the transmission wave in the distance measurement phase, a frequency shift based on the target distance delay occurs, and the target frequency fb (Hz) based on the target distance delay is observed.

  5A and 5B are diagrams showing the relationship between a transmission signal and a reception signal in a conventional high PRF pulse Doppler radar device, where FIG. 5A shows frequency-time variations of the transmission signal and the reception signal in the target search phase, and FIG. And the relationship between the frequency and amplitude of the target signal. In FIG. 5A, a line 113 indicates a transmission signal and a line 114 indicates a reception signal. If the frequency modulation speed in the distance measurement phase is ΔF (Hz / s), the target Doppler frequency 115 in the target search phase and the target frequency 116 in the distance measurement phase have the relationship shown in FIG. At 109, the target distance is calculated as follows.

"AIRBORNE PULSED DOPPLER RADAR" by Guy V. Morris, published by Artech House, 1989, P77-80 "AIRBORNE PULSED DOPPLER RADAR" by Guy V. Morris, published by Artech House, 1989, P391-408

  In the conventional high PRF pulse Doppler radar apparatus, distance measurement is performed in the distance measurement phase in which frequency modulation is performed on the target detected in the target search phase in which frequency modulation is not performed. For this reason, in the target search phase in which frequency modulation is not performed, there is a problem that target detection becomes difficult when the clutter and the target frequency overlap.

  The present invention has been made to solve the above-described problem, and provides a pulse Doppler radar device that enables target detection using a high PRF transmission pulse even when the clutter and the target frequency overlap. Objective.

  A pulse Doppler radar apparatus according to the present invention outputs a transmission pulse subjected to frequency modulation with a high pulse repetition frequency, receives a reflected signal from a target and obtains a video signal, and a target from the obtained video signal. In the pulse Doppler radar apparatus that measures the distance to the first frequency modulation in the first phase by the first linear frequency modulation in the first phase, the time change rate is higher than that in the first linear frequency modulation in the second phase. A frequency modulation controller for controlling the frequency of the transmission pulse from the transceiver so as to perform the second frequency modulation by the second linear frequency modulation having a large value, and the transmission pulse subjected to the first frequency modulation. The target first frequency is observed from the video signal obtained by the transmission / reception, and the video signal obtained by the transmission / reception of the transmission pulse subjected to the second frequency modulation. A target detection processing unit for observing the second frequency of the target from the signal, and a distance measurement unit for measuring the target distance based on the first and second frequencies of the target observed by the target detection processing unit. It is equipped with.

  According to the present invention, even when the clutter and the target Doppler frequency are equal, by searching for the target while performing frequency modulation, it is possible to detect the target and measure the distance using the fact that the distance between the clutter and the target is different. The effect of becoming.

It is a figure which shows the structure of the high PRF pulse Doppler radar apparatus by Embodiment 1 which concerns on this invention. 6 is a diagram illustrating a relationship between a transmission signal and a reception signal in Embodiment 1. FIG. 6 is a diagram illustrating a method of separating a clutter and a target signal in the first embodiment. FIG. It is a figure which shows the structure of the conventional pulse Doppler radar apparatus of high PRF. It is a figure which shows the relationship between the transmission signal in the conventional pulse Doppler radar apparatus of high PRF, and a received signal.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of a high PRF pulse Doppler radar apparatus according to Embodiment 1 of the present invention. In FIG. 1, a high PRF pulse Doppler radar device includes a frequency modulation controller (2) 1, a transmitter 2, an antenna 3, a receiver 4, two A / D converters 5, and two systems. It comprises a filter means 6, two frequency analysis means 7, two target detection means 8, a distance measurement means (2) 9, and a phase controller (2) 10. The first system A / D converter 5, the first system filter means 6, the first system frequency analysis means 7, the first system target detection means 8, and the frequency modulation controller (2) 1 The target search unit 11 is configured. Further, the second system A / D converter 5, the second system filter means 6, the second system frequency analysis means 7, the second system target detection means 8, and the frequency modulation controller (1). 101 and the distance measuring means (1) 9 constitute a distance measuring unit 12. The frequency analysis means 7 and the target detection means 8 constitute a target detection processing unit.

  In the first embodiment, in both the target search phase and the distance measurement phase, linear frequency modulation control of the transmitter 2 by the frequency modulation controller (2) 1 in accordance with the switching control of the operation phase by the phase controller (2) 10. Is done. However, different frequency modulation rates are used in each phase.

First, in the high PRF pulse Doppler radar apparatus, the phase controller (2) 10 sets the operation phase to the target search phase which is the first phase, and the search for the target in the target search phase is started. The phase controller (1) 10 controls the frequency modulation controller (1) 1 so as to perform the first frequency modulation corresponding to the target search phase.
In the target search phase, by the control from the phase controller (1) 10, the frequency modulation controller (1) 1 performs control for applying the first frequency modulation to the transmission signal (transmission pulse), and the transmitter 2 A transmission signal subjected to the first frequency modulation is generated. In the first frequency modulation, linear frequency modulation is performed in which the frequency changes linearly with time. A transmission signal subjected to the first frequency modulation is radiated from the antenna 3 into space. The reflected signal from the target is received by the antenna 3, and the received signal is detected by the receiver 4 by the same frequency modulation signal as the frequency modulation applied to the transmission signal and converted into a video signal. Is done.

  The target search unit 11 converts the video signal into a digital video signal by the A / D converter 5, performs necessary band limitation by the filter unit 6, and then performs frequency analysis by the frequency analysis unit 7. Since the target signal has only a single component in frequency, it is integrated to a specific frequency by frequency analysis. The target detection means 8 detects the target from the frequency analysis result using a method such as CFAR (Constant False Alarm Rate) shown in Non-Patent Document 2. At this time, since the first frequency modulation is applied to the transmission signal in the target search phase, a frequency shift based on the target distance delay occurs, and the first frequency according to the target distance delay is obtained. A target frequency fc (Hz) is observed.

After detecting the target in the target search phase, the phase controller (1) 10 shifts the processing to the distance measurement phase which is the second phase, and performs the first frequency modulation corresponding to the distance measurement phase. Modulation controller (1) 1 is controlled.
In the distance measurement phase, by the control from the phase controller (1) 10, the frequency modulation controller (1) 1 performs control for applying the second frequency modulation to the transmission signal (transmission pulse), and the transmitter 2 A transmission signal subjected to the second frequency modulation is generated. In the second frequency modulation, linear frequency modulation in which the frequency changes linearly with time change is performed, but linear frequency modulation is performed with a larger time change rate different from the second frequency modulation. For example, the frequency modulation speed of the second frequency modulation is set to twice the frequency modulation speed of the first frequency modulation. Similar to the target search phase, the transmission signal subjected to the second frequency modulation is radiated from the antenna 3 to the space. A reflected signal from the target is received by the antenna 3, and the received signal is detected by the receiver 4 using the same frequency modulation signal as the frequency modulation applied to the transmission signal and converted into a video signal. .

  The target search unit 11 converts the video signal into a digital video signal by the A / D converter 5, performs necessary band limitation by the filter unit 6, and then performs frequency analysis by the frequency analysis unit 7. Since the target signal has only a single component in frequency, it is integrated to a specific frequency by frequency analysis. The target detection means 8 detects the target from the frequency analysis result using a method such as CFAR (Constant False Alarm Rate) shown in Non-Patent Document 2. At this time, since the second frequency modulation is applied to the transmission wave in the distance measurement phase, a frequency shift based on the target distance delay occurs, and the second frequency according to the target distance delay is obtained. A target frequency fd (Hz) is observed.

  FIG. 2 is a diagram illustrating a relationship between a transmission signal and a reception signal in the first embodiment. In the example of FIG. 2, in the target search phase, frequency modulation at a frequency modulation speed ΔF (Hz / s) is performed as the first frequency modulation, and the target frequency fc (Hz) is observed. In the distance measurement phase, frequency modulation at a frequency modulation speed of 2 × ΔF (Hz / s) is performed as the second frequency modulation, and the target frequency fd (Hz) is observed.

  FIG. 3 is a diagram illustrating a method of separating the clutter and the target signal in the first embodiment. For example, in the state shown in FIG. 3A, the target Doppler frequency and the Doppler frequency of the clutter immediately below the aircraft are both equal to “0”, so frequency modulation was not performed in the target search phase. In this case, as shown in FIG. 3B, the target 18 becomes difficult to detect due to the influence of the direct clutter 19.

  However, in the first embodiment, since frequency modulation is also performed in the target search phase, the clutter and the target frequency are observed by the following equations (2) and (3), respectively.

  Thereby, as shown in FIG. 3C, the signals of the target 20 and the direct clutter 22 are separated in the target search phase, and the signals of the target 21 and the direct clutter 23 are also separated in the distance measurement phase. For this reason, even in the presence of a direct clutter, it is possible to reliably detect a target of specifications that could not be detected in the conventional target search phase. In the target search phase, the target detection means 8 uses a method such as CFAR based on the frequency analysis result of the frequency analysis means 7 to set a frequency whose absolute value is equal to or greater than a predetermined threshold as the first target frequency. To separate. Further, in the distance measurement phase, the target detection unit 8 uses a method such as CFAR, based on the frequency analysis result of the frequency analysis unit 7, to obtain a target second value that is equal to or greater than a predetermined threshold value. Separate as frequency.

  The distance measuring means 9 calculates the target true Doppler frequency from the target frequency fc (Hz) that is the first frequency in the target search phase and the target frequency fd (Hz) that is the second frequency in the distance measurement phase. ftgt (Hz) is calculated by the following equation (4).

  Further, the distance measuring unit 9 calculates the target distance Rtgt from the target frequency fc (Hz) that is the first frequency in the target search phase and the target frequency fd (Hz) that is the second frequency in the distance measurement phase. Is calculated by the following equation (5).

  Thus, in both the target search phase and the distance measurement phase, the frequency modulation control by the frequency modulation controller (2) 1 is performed by the control from the phase controller (2) 10. Frequency modulation is performed at different frequency modulation speeds in the target search phase and the distance measurement phase, and a frequency shift based on the target distance delay occurs in both phases. Since linear frequency modulation is performed in the target search phase, it is possible to separate the target and clutter signals by using the fact that the frequency differs depending on the distance between the clutter and the target.

  As described above, the pulse Doppler radar device according to Embodiment 1 outputs a transmission pulse subjected to frequency modulation with a high pulse repetition frequency, receives a reflected signal from a target, and obtains a video signal, and In the receiver 4 and the pulse Doppler radar device that measures the distance from the obtained video signal to the target, after performing the first frequency modulation by the first linear frequency modulation in the target search phase, the distance measurement phase is started. A frequency modulation controller for controlling the frequency of the transmission pulse from the transceiver so as to perform the second frequency modulation by the second linear frequency modulation having a time change rate larger than that of the first linear frequency modulation; The target first frequency is observed by frequency analysis from the video signal obtained by transmitting and receiving the transmission pulse subjected to the first frequency modulation, A target detection processing unit for observing a target second frequency by frequency analysis from a video signal obtained by transmitting and receiving a transmission pulse subjected to second frequency modulation, and a target detected by the target detection processing unit And a distance measuring unit that measures the target distance based on the first and second frequencies.

  With this configuration, it is possible to separate the target and clutter signals by utilizing the fact that the frequency is different depending on the distance between the clutter and the target. Therefore, it is difficult to detect the target because the clutter and target Doppler frequencies are equal. Even in such a case, it is possible to detect the target and calculate the target distance and the Doppler frequency.

  1 frequency modulation controller (2), 2 transmitter, 3 antenna, 4 receiver, 5 A / D converter, 6 filter means, 7 frequency analysis means, 8 target detection means, 9 distance measurement means (2), 10 Phase controller, 11 Target search phase configuration, 12 Distance measurement phase configuration, 13 Transmit signal frequency, 14 Receive signal frequency, 15 Own device, 16 Target, 17 Direct clutter range, 18 Target signal, 19 Direct clutter signal, 20 Target search Phase target signal, 21 Distance measurement phase target signal, 22 Target search phase direct clutter signal, 23 Distance measurement phase direct clutter signal, 101 Frequency modulation controller (1), 109 Distance measurement means (1), 110 Phase controller (1 ).

Claims (1)

A transmitter / receiver that outputs a transmission pulse that is frequency-modulated with a high pulse repetition frequency and receives a reflected signal from the target to obtain a video signal, and a pulse Doppler radar that measures the distance from the obtained video signal to the target In the device
After performing the first frequency modulation by the first linear frequency modulation in the first phase, the second frequency by the second linear frequency modulation having a time change rate larger than the first linear frequency modulation in the second phase. A frequency modulation controller for controlling the frequency of the transmission pulse from the transceiver so as to perform frequency modulation;
The target first frequency is observed from the video signal obtained by transmission / reception of the transmission pulse subjected to the first frequency modulation, and the video obtained by transmission / reception of the transmission pulse subjected to the second frequency modulation. A target detection processing unit for observing a target second frequency from the signal;
A distance measuring unit that measures the distance of the target based on the first and second frequencies of the target observed by the target detection processing unit;
A pulse Doppler radar device comprising:

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