JP2014002109A - Passive radar system, passive radar receiver and target detection program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a passive radar system capable of detecting a target with high accuracy by improving suppression performance of unnecessary waves.SOLUTION: A passive radar 100 includes: an antenna 11 for receiving a reflection wave of a transmission radio wave from a transmission station which is reflected by a target; a gate 131 for opening/closing input of a signal received by the antenna and outputting it; a gate control device 132 for controlling the gate to be closed during a blanking period corresponding to a period during which a direct wave of the transmission radio wave is received synchronously with transmission timing of the transmission station; and a signal processing unit 14 for detecting a target on the basis of the signal output from the gate.

Description

  Embodiments described herein relate generally to a passive radar device, a passive radar receiving device, and a target detection program that detect a target using transmission radio waves from an existing transmitting station or the like.

  Passive radar is a technique for detecting a target by using an existing transmitting station or the like as a radar wave source without receiving a radio wave and receiving a reflected wave from the target of the transmitted radio wave. Since no radar transmission station that requires large power is provided, power consumption and cost can be reduced.

  However, in the conventional passive radar, the direct wave or multipath wave of the transmitting station becomes an unnecessary wave, which deteriorates the target detection performance. Therefore, a technique has been proposed in which these unnecessary waves are suppressed by spatial filtering processing (for example, MSN (Maximum Single-to-Noise Ratio) adaptive weights or PIAA (Power Inversion Adaptive Array)) and target reflected waves are received ( For example, see Non-Patent Documents 1 and 2.)

“Direct Path Interference Cancellation in FM Radio-Based Passive Radar”, Hong Wan, IEEE Signal Processing, 2006 8th International Conference “Research on the Interference Cancelation in SFN Based Passive Radar”, Shan Tao, IEEE Measuring Technology and Mechatronics Automation, 2011 Third International Conference

  As described above, MSN adaptive weights, PIAA, and the like are considered as conventional techniques for unnecessary waves in passive radar. However, the reception SNR (Signal to Noise Rate) of the direct wave is at a very high level, and in order to satisfy the required improvement factor by the conventional technique, further improvement of unnecessary wave suppression performance is essential.

  An object of the present embodiment is to provide a passive radar device, a passive radar receiver, and a target detection program that can improve the suppression performance of unnecessary waves and can detect a target with high accuracy.

  The passive radar device according to the present embodiment includes an antenna that receives a reflected wave according to a target of a transmission radio wave from a transmission station, a gate that opens and closes an input of a signal received by the antenna, and the transmission station. The gate control means for controlling the gate to be closed in a blanking period corresponding to a period in which the direct wave of the transmission radio wave is received in synchronization with the transmission timing of the transmission, and based on the signal output from the gate Signal processing means for detecting a target.

  A passive radar receiving apparatus according to the present embodiment is a passive radar receiving apparatus that receives a reflected wave by a target of a transmission radio wave from a transmitting station, and has a gate that opens and closes an input of the received signal, and outputs a gate. And gate control means for controlling the gate to be closed in a blanking period corresponding to a period in which a direct wave of the transmission radio wave is received in synchronization with the transmission timing of the transmitting station.

  A target detection program according to the present embodiment includes a passive antenna including an antenna that receives a reflected wave from a target of a transmission radio wave from a transmission station, and a gate that opens and closes an input of a signal received by the antenna and outputs the signal. A gate control process for controlling the gate to be closed in a blanking period corresponding to a period during which the direct wave of the transmission radio wave is received in synchronization with the transmission timing of the transmission station, and output from the gate to the radar device. Signal processing for detecting the target on the basis of the signal.

The conceptual diagram of a passive radar. The block diagram which shows the structural example of the passive radar which concerns on this embodiment. 3 is a timing chart showing a blanking process according to the first embodiment. FIG. 6 is a diagram illustrating an example of specifications of a transmission station and transmission pulse timing according to the second embodiment. The timing chart which shows the blanking process synchronizing with the transmission pulse for long distances. The timing chart which shows the blanking process synchronizing with the transmission pulse for short distances. The figure which shows the target detectable coverage in the case of Example 2. FIG. FIG. 10 is a diagram illustrating a processing system of unnecessary wave suppression operation according to the third embodiment. 9 is a timing chart showing a blanking process according to Embodiment 3. The figure which shows the target detectable coverage in the case of Example 3. FIG. The figure which shows an example of reception SNR of an unnecessary wave. The figure which shows the performance evaluation result by the conventional unnecessary wave suppression weight.

  Hereinafter, the passive radar according to the present embodiment will be described with reference to the drawings.

  FIG. 1 shows a conceptual diagram of a passive radar. As shown in FIG. 1, a passive radar uses an existing transmitting station as a radar wave source without radiating a radio wave itself, receives a reflected wave from a target of the transmitted radio wave, and detects a target. The direct wave and multipath wave of the station become unnecessary waves, and the target detection performance deteriorates. In the present embodiment, a passive radar is proposed in which the unnecessary wave suppression performance is improved and the target can be detected with high accuracy.

  FIG. 2 is a block diagram illustrating a configuration example of the passive radar according to the present embodiment. The passive radar 100 includes an antenna 11, a circulator 12, an excitation receiving unit 13, and a signal processing unit 14. The reflected wave from the target arriving at the antenna 11 is received by the excitation receiver 13 via the circulator 12. The signal processing unit 14 performs target detection processing based on the received signal output from the excitation receiving unit 13.

  The excitation receiver 13 includes a gate 131, a gate controller 132, an amplifier 133, a mixer 134, an oscillator 135, and a detector 136. The gate 131 performs a gating operation for unnecessary wave suppression according to a control signal input from the gate controller 132. The gated received signal is amplified to a predetermined level by the amplifier 133, frequency-converted by an oscillation signal having a predetermined frequency input from the oscillator 135 by the mixer 134, and then phase-detected by the detector 136.

  Hereinafter, blanking processing for the purpose of suppressing unnecessary waves in the passive radar according to the present embodiment will be described according to each example.

Example 1
FIG. 3 is a timing chart illustrating the blanking process according to the first embodiment. The gate controller 132 is a period (a period corresponding to a transmission pulse width) in which a direct wave from the transmission station is received in synchronization with a pulse repetition interval (PRI) input as a timing signal of the transmission station. Controls the gate 131 to be “closed”. On the other hand, during a period when the direct wave is not received (transmission pulse width + propagation time), the gate 131 is controlled to be “open”, the reception signal is output to the subsequent stage, and the signal processing unit 14 performs target detection processing. That is, a blanking period corresponding to the transmission pulse width is provided after the radio wave propagation time has elapsed with respect to the transmission pulse width and the distance between the transmitting station and the passive radar (R _{dir in} FIG. 1). Note that there are various methods of synchronization with the transmitting station in the passive radar, and therefore it is not limited to the method of FIG.

  By performing the blanking operation as in the first embodiment, the influence of the direct wave from the transmission station is made zero as much as possible, and the target detection can be performed with high accuracy. In addition, by including a period in which the multipath wave of the transmission radio wave is received in the blanking period, it is possible to suppress not only the direct wave from the transmission station but also the multipath wave as an unnecessary wave.

(Example 2)
The fixed-ground radar detects short-distance and long-distance targets in order to detect targets at short and long distances. It is common to distinguish between pulses for use. In the second embodiment, blanking processing is performed in synchronization with the long-distance transmission pulse or the short-distance transmission pulse.

  FIG. 4 shows an example of specifications of the transmission station and transmission pulse timing in the case of the second embodiment. As shown in the table on the left of FIG. 4, the radar frequency band is the S band (2,000 to 4,000 MHz), the number of PRI pulses is 10, and the PRI is 5.1 msec. As shown in the right of FIG. 4, the transmission pulse timing is such that a long-distance transmission pulse (p1, p2, p3) is transmitted with a transmission pulse width of 700 μsec, and then a short-distance transmission pulse (p4) is transmitted with an interval of 3650 μsec. Transmission is performed with a width of 50 μsec, and an interval of 700 μsec is provided.

  FIG. 5 is a timing chart of the blanking process synchronized with the long-distance transmission pulse. The gate controller 132 provides a blanking period corresponding to the long-distance transmission pulse width and the reception period of the multipath wave in synchronization with the PRI inputted as the timing signal of the transmitting station, and makes the gate 131 “closed”. Control. On the other hand, during a period corresponding to the transmission pulse width and propagation time, the gate 131 is controlled to be “open” to output the received signal to the subsequent stage, and the signal processing unit 14 performs target detection processing.

  FIG. 6 is a timing chart of the blanking process synchronized with the short-distance transmission pulse. The gate controller 132 provides a blanking period corresponding to the transmission pulse width for short distance and the reception period of the multipath wave in synchronization with the PRI inputted as the timing signal of the transmitting station, and makes the gate 131 “closed”. Control. On the other hand, during a period corresponding to the transmission pulse width and propagation time, the gate 131 is controlled to be “open” to output the received signal to the subsequent stage, and the signal processing unit 14 performs target detection processing.

  Here, FIG. 7 shows the target detectable coverage by the blanking process in the second embodiment. 7A and 7B, the horizontal axis represents XRange (km), the vertical axis represents YRange (km), the colored portion is a region with high radio wave reception sensitivity, and the white portion is a blind region. FIG. 7A shows a case where blanking processing is performed in synchronization with the long-distance pulse, and the long-distance range is a detectable coverage. FIG. 7B shows a case where blanking processing is performed in synchronization with the short-distance pulse, and it is understood that the short-distance range is a detectable coverage.

  Therefore, according to the second embodiment, even when the transmitting station transmits a plurality of transmission radio waves for detecting targets in a plurality of detection distance ranges, the gate is controlled to be closed during a period in which each direct wave is received. Thus, the influence of each direct wave can be reduced.

(Example 3)
According to the second embodiment, it can be seen that in FIG. 7A, the short distance range is a blind area, and in FIG. 7B, the long distance range is a blind area. That is, it is considered that the blanking process has a disadvantage that the target cannot be detected during the time period when the gate 131 is “closed”. Therefore, in the third embodiment, the passive radar side adaptively selects the data area used for the target detection process from the data received by 1PRI, respectively for the long-distance pulse reception data and the short-distance pulse reception data. Configure as follows.

  FIG. 8 shows a processing system of the unwanted wave suppression operation of the perspective hybrid according to the third embodiment. FIG. 9 is a timing chart showing the blanking process according to the third embodiment.

  The gate controller 132 performs the blanking process (Rx gating) of S1 based on the perspective pulse timing information of the transmitting station. As shown in FIG. 9, the gate controller 132 synchronizes with the PRI inputted as the timing signal of the transmitting station, and the long-distance / short-distance transmission pulse width and the reception period of the multipath wave. A long distance / short distance blanking period corresponding to is provided, and the gate 131 is controlled to be “closed”. On the other hand, the gate 131 is controlled to be “open” during a period corresponding to the long-distance transmission pulse width and the propagation time and a period corresponding to the short-distance transmission pulse width and the propagation time.

  In the long-distance pulse data detection processing system in S2, reception processing is performed at a later stage using the long-distance pulse data output from the gate 131, and the long-distance pulse data processing result in S3 is output. On the other hand, in the short distance pulse data detection processing system of S4, reception processing is performed at a later stage using the short distance pulse data output from the gate 131, and the short distance pulse data processing result of S5 is output. In the integration processing of S6, the long-distance pulse data processing result of S3 and the short-distance pulse data processing result of S5 are integrated, and the signal processing unit 14 performs target detection processing using the long-distance hybrid result.

  FIG. 10 shows the target detectable coverage in the case of the third embodiment. As in FIG. 7, the horizontal axis represents XRange (km), the vertical axis represents YRange (km), the colored portion is a region with high radio wave reception sensitivity, and the white portion is a blind region. Compared with FIG. 7, it can be seen that in FIG. 10, the blind area is reduced and the target detectable coverage area is improved.

Here, a comparative example is shown in order to explain the effect of this embodiment. First, FIG. 11 shows an example of the reception SNR of unnecessary waves. In FIG. 11, R _dir [km] is taken on the horizontal axis and SNR [dB] is taken on the vertical axis, and the reception SNR of the direct wave is shown by a solid line and the multipath wave is shown by a broken line. When these are compared with the target detection threshold indicated by the one-dot chain line in FIG. 11, the reception SNR of the direct wave is very high, and the required improvement factor for suppressing this is required to be 110 dB or more, and there is a problem in feasibility. It was.

  As a comparative example, FIG. 12A shows the MSN adaptive weight, and FIG. 12B shows the evaluation result of the unwanted wave suppression performance by PIAA. 12A and 12B, the horizontal axis represents the azimuth angle [deg] and the gain [dB]. 12A shows a suppression performance of about −90 dB in the direct wave direction, and FIG. 12B shows a suppression performance of about −100 dB in the direct wave direction. However, the suppression performance requirement value (−110 dB) is not yet satisfied. .

  On the other hand, according to the present embodiment, the direct wave is temporally suppressed by the blanking process, so that it is not affected by the direct wave, and the target detectable coverage is set as shown in FIGS. Can be widely obtained. Therefore, according to the present embodiment, it is possible to realize a passive radar that can improve the unnecessary wave suppression performance and can detect the target with high accuracy.

  Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 100 ... Passive radar, 11 ... Antenna, 12 ... Circulator, 13 ... Excitation receiving part, 14 ... Signal processing part, 131 ... Gate, 132 ... Gate controller, 133 ... Amplifier, 134 ... Mixer, 135 ... Oscillator, 136 ... Detection vessel.

Claims (9)

An antenna for receiving a reflected wave by a target of a transmission radio wave from a transmitting station;
A gate for opening / closing an input of a signal received by the antenna and outputting the signal;
In synchronization with the transmission timing of the transmitting station, gate control means for controlling the gate to be closed in a blanking period corresponding to a period in which a direct wave of the transmission radio wave is received;
A passive radar device comprising: signal processing means for detecting the target based on a signal output from the gate. When the transmitting station transmits a plurality of transmission radio waves for detecting targets in a plurality of detection distance ranges,
2. The passive radar according to claim 1, wherein the gate control unit controls the gate to be closed in a plurality of blanking periods corresponding to a period in which each direct wave of the plurality of transmission radio waves is received. apparatus.   3. The passive radar device according to claim 1, wherein the blanking period further includes a period in which a multipath wave of the transmission radio wave is received. A passive radar receiver that receives a reflected wave by a target of a transmission radio wave from a transmission station,
A gate that opens and closes the input of the received signal and outputs it;
A passive radar comprising gate control means for controlling the gate to be closed during a blanking period corresponding to a period during which a direct wave of the transmission radio wave is received in synchronization with a transmission timing of the transmission station. Receiver device. When the transmitting station transmits a plurality of transmission radio waves for detecting a target of a plurality of detection distances,
5. The passive radar according to claim 4, wherein the gate control unit controls the gate to be closed in a plurality of blanking periods corresponding to a period in which each direct wave of the plurality of transmission radio waves is received. Receiver device.   The passive radar receiver according to claim 4, wherein the blanking period further includes a period during which a multipath wave of the transmission radio wave is received. To a passive radar device comprising: an antenna that receives a reflected wave from a target of a transmission radio wave from a transmitting station; and a gate that opens and closes an input of a signal received by the antenna and outputs it.
In synchronization with the transmission timing of the transmitting station, a gate control process for controlling the gate to be closed in a blanking period corresponding to a period in which a direct wave of the transmission radio wave is received;
A target detection program for executing signal processing for detecting the target based on a signal output from the gate. When the transmitting station transmits a plurality of transmission radio waves for detecting targets in a plurality of detection distance ranges,
The target detection according to claim 7, wherein the gate control process controls the gate to be closed in a plurality of blanking periods corresponding to a period in which each direct wave of the plurality of transmission radio waves is received. program.   The target detection program according to claim 7, wherein the blanking period further includes a period during which a multipath wave of the transmission radio wave is received.

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