JP2021047106A - Passive type radar device, and passive type radar signal processing method - Google Patents

Abstract

To identify a target position even in an environment where a direct wave cannot be obtained from a transmitting station.SOLUTION: A passive type radar device according to an embodiment, in an environment where a direct wave of a radar wave transmitted from a transmitting station whose transmission sources are known cannot be obtained, receives an indirect wave in which the radar wave is reflected on a target, performs target detection through passive radar processing based on the transmission sources of the transmitting station, acquires position information and time information from a target that provides the position information through communication, takes the correlation between a result of target detection through the passive radar processing and target information obtained through the communication with the target to estimate the position of the target, acquires transmitting station position information from the transmission sources of the transmitting station, estimates the pulse transmission time of the transmitting station from the position information on the target whose position has been estimated and target detection time, manages a transmitting station pulse timing by using a result of transmission time estimation, and performs target detection during actual operation based on the timing.SELECTED DRAWING: Figure 6

Description

An embodiment of the present invention relates to a passive radar device and a passive radar signal processing method.

In a passive radar device that detects a target by radio waves using another radar as a transmitting station, the azimuth angle and elevation angle are derived by angle measurement processing for the target detection signal, and the wave and target are reflected directly from the transmitting station. By deriving the distance from the detection time difference from the indirect wave, the position with respect to the detection signal assumed to be the target is estimated.

As described above, in deriving the distance at the time of estimating the position of the passive radar device, it is necessary to grasp the time difference between the reception time of the direct wave and the detection time of the indirect wave. If the transmitting station is located outside the line of sight of the radio waves of the passive radar device, or in an environment where direct waves cannot be obtained on the passive radar device side, it becomes difficult for the passive radar device to calculate the distance. It becomes impossible to estimate the position of the target. Therefore, the passive radar device has a problem that the operating range is limited to the range where the direct wave of the transmitting station can reach (for example, Line Of Sight).

Japanese Unexamined Patent Publication No. 2016-138787 JP-A-2002-3111132

M. I. Skolnik, “Radar Handbook,” Third edition, pp. 23.1-23.13, McGraw-Hill, New York, N. J. Wills, “Bistatic Radar,” Second edition, Silver Spring, MD: Technology Service Corp., 1995. Corrected and republished by Raleigh, NC: SciTech Publishing, Inc., 2005

As described above, the conventional passive radar device has a problem that the operating range is limited to the range where the direct wave of the transmitting station can reach.

An embodiment of the present invention provides a passive radar device and a passive radar signal processing method capable of specifying a target position even in an environment where a direct wave required for synchronization with a transmitting station cannot be obtained. The purpose is.

The passive radar device according to the embodiment receives an indirect wave in which the radar wave is reflected by a target in an environment where a direct wave of a radar wave transmitted from a transmission station whose transmission specifications are known cannot be obtained. It is a device that detects the position of a target, and includes a passive radar processing unit, a target position information acquisition unit, and an information processing unit. The passive radar processing unit receives the indirect wave and performs target detection based on the transmission specifications of the transmitting station. The target position information acquisition unit acquires position information and time information from a target that provides position information by communication. The information processing unit estimates the target position by correlating the target detection result obtained by the passive radar processing unit with the target information obtained by the target position information acquisition unit, and transmits the target from the transmission specifications of the transmitting station. The station position information is acquired, the pulse transmission time of the transmitting station is estimated from the position-estimated target position information and the target detection time, the transmission station pulse timing is managed using the transmission time estimation result, and the transmission station pulse timing is managed based on the timing. , Perform target detection during actual operation.

FIG. 1 is a conceptual diagram showing a configuration of a radar system including a passive radar device to which the present embodiment is applied. FIG. 2 is a block diagram showing a configuration of a passive radar device to which the present embodiment is applied. FIG. 3 is a diagram showing a distance calculation method using a passive radar device to which the present embodiment is applied. FIG. 4 is a conceptual diagram showing a position information acquisition image of a target machine in the passive radar device according to the present embodiment. FIG. 5 is a diagram showing an image of correlation processing (time matching processing) of the passive radar device according to the present embodiment. FIG. 6 is a flowchart showing a radar signal processing procedure when a direct wave cannot be obtained in the passive radar device according to the present embodiment.

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

FIG. 1 is a conceptual diagram showing a configuration of a radar system including a passive radar device (hereinafter, passive radar) 100 to which the present embodiment is applied. In FIG. 1, the passive radar 100 receives the direct wave W1 that directly receives the transmitted wave transmitted from the transmitting station 200 and the indirect wave W2 that is reflected by the target machine T and arrives, and the angle and time difference between the received waves. The position of the target machine T is specified from.

FIG. 2 is a block diagram showing the configuration of the passive radar 100. In FIG. 2, the passive radar 100 includes a first antenna unit 101, an indirect wave signal processing unit 102, a cumulative unit 103, a synthesis unit 104, and a target machine position specifying unit 105. Further, the passive radar 100 includes a second antenna unit 106, a direct wave signal processing unit 107, and a control unit 108. The cumulative unit 103, the combining unit 104, the target machine position specifying unit 105, and the control unit 108 can be realized by a computer device having functions as an arithmetic circuit and a control circuit.

The first antenna unit 101 includes an antenna element that captures an incoming wave and obtains a received signal. Under the control of the control unit 108, the indirect wave signal processing unit 102 extracts a signal (indirect wave signal) during the period when the indirect wave W2 arrives from the received signals obtained by the first antenna unit 101. The indirect wave signal is subjected to reception processing such as limiter processing, amplification processing, filter processing, and A / D conversion processing. The indirect wave signal that has undergone reception processing is output to the cumulative unit 103.

The accumulation unit 103 is an arithmetic unit that accumulates the signal values of the indirect wave signals during the cumulative period controlled by the control unit 108, and accumulates the signal values of the input indirect wave signals.

The second antenna unit 106 includes an antenna element that captures the incoming wave and obtains a received signal, in addition to the first antenna unit 101 (which may be shared or partially used). The direct wave signal processing unit 107 extracts a signal (direct wave signal) during the period when the direct wave W1 arrives from the received signals obtained by the second antenna unit 106, and performs limiter processing on the direct wave signal. Receive processing such as amplification processing, filtering processing, and A / D conversion processing is performed. The direct wave signal that has undergone reception processing is output to the control unit 108.

The control unit 108 obtains the arrival timing of the direct wave W1 and the start timing of the interval based on the direct wave signal obtained by the direct wave signal processing unit 107, and extracts the indirect wave signal based on the arrival timing of the direct wave W1. The period (the arrival period of the indirect wave W2) is controlled. Further, the control unit 108 controls the cumulative period of the indirect wave signal in the cumulative unit 103.

The synthesis unit 104 synthesizes the results accumulated by the accumulation unit 103. The target machine position specifying unit 105 specifies the position of the target machine T based on the result synthesized by the synthesis unit 104. The position information of the target machine T specified by the target machine position specifying unit 105 is output to the outside and displayed as a detection result of the target machine T, for example.

In the passive radar 100 having the above configuration, the azimuth angle θ and the elevation angle φ are derived from the detection signal of the target machine T by angle measurement processing, and as shown in FIG. 3, the reception time t of the direct wave of the transmission station 200 By deriving the distance R _r from the time difference ΔT _rt (= t _2- t _{1 ) between 1} and the detection time t _{2 of the indirect wave, the position (R r} ,) with respect to the detection signal assumed to be the target machine T Position estimation of θ, φ). The following equation is applied to derive the distance.

Here, c is the speed of light, L is the distance between the passive radar 100 and the transmission station 200 (baseline), and α is the angle measurement angle of the passive radar 100 (the transmission station 100 and the target machine T as seen from the passive radar 100). Corner).

As a precondition of this embodiment, the passive radar 100 has known transmission specifications (transmission station position, scan rate, pulse timing (PRI (Pulse Repeat Interval), number of pulses, etc.)) of the transmission station 200. Suppose that Further, it is assumed that a friendly aircraft or a civil aviation aircraft, which is the target aircraft T, exists in the surveillance airspace of the passive radar 100.

In the radar system, the processing flow of the present embodiment will be described below with reference to FIGS. 4 and 5. FIG. 4 is a conceptual diagram showing an image of acquiring position information of the target machine T in the present embodiment, and FIG. 5 is a diagram showing an image of correlation processing (time matching processing).

First, as shown in FIG. 4A, the passive radar 100 uses the radio waves of the transmitting station 200 to establish its track by the detection signal for the target aircraft T. At that time, since the passive radar 100 cannot obtain the direct wave of the transmitting station 200, it becomes difficult to calculate the distance to the track of the target aircraft T. Therefore, in the passive radar 100 according to the present embodiment, in order to estimate the position of the distance, for example, as shown in FIG. 4B, a friendly aircraft or a civil aviation aircraft is set as the target aircraft T, and SIF / IFF (Special Identification of). Feature / Identification friend or foe) Question-How to acquire the position information of the target aircraft T with respect to the time based on the response information, for example, the target aircraft T adds the position information with respect to the time to the communication signal and notifies the passive radar 100. The position information with respect to the time of the target aircraft T is acquired by a method such as.

At this time, the position information of the target machine T with respect to the time is discrete information. Therefore, as shown in FIG. 5, the time of the track with respect to the target aircraft T is matched by using interpolation by correlation processing. As a result, a highly accurate track can be obtained from the discrete position information, and the distance can be easily calculated from the track of the target aircraft T.

When the position of the track of the target machine T can be specified by the correlation processing, the transmission time of the radar pulse transmitted from the transmission station 200 is estimated from the distance information between the target machine T and the transmission station 200. The estimation formula of the pulse transmission time t _tx by the transmission station 200 is as shown below.

Here, t _p is the target machine detection time of any of the tracks of the target machine T, R _s is the distance between the target machine T and the transmission station 200, and c is the speed of light.

After calculating the estimated value of the transmission time t _{tx , the reception time tr} x of the direct wave is calculated by the following formula.

Here, L is the distance (baseline) between the transmitting station 200 and the passive radar 100. After that, the position of the target machine T can be estimated by managing the pulse timing of the transmission station 200 with the passive radar 100 based on the transmission time t _{tx of the transmission station 200 and the PRI.}

FIG. 6 is a flowchart showing a radar signal processing procedure by the control unit 108 when the passive radar 100 is placed in an environment where the direct wave required for synchronization with the transmission station 200 cannot be obtained.

In FIG. 6, the control unit 108 of the passive radar 100 has the transmission station specifications (pulse compression coefficient, pulse repetition cycle, transmission station) of the transmission station 200 separately obtained and registered in an environment where a direct wave signal cannot be obtained. The pulse compression coefficient is input from the position information), the received radar pulse is subjected to pulse compression processing to extract the signal component (step S13), and the pulse repetition period is input from the transmission station specifications to perform pulse integration processing. (Step S14), the target machine is detected from the signal components accumulated by the signal detection process (step S15). If there is no detection, the process returns to step S11 as the transmission time cannot be estimated, and the process proceeds to the next target machine detection.

On the other hand, in the target machine position information acquisition process by SIF / IFF or the like, the target machine position information is acquired (step S15). Since the target machine position information is discrete, the target machine position information is matched so as to have a constant time interval by the time matching process (step S16). The position of the target machine T is estimated by the correlation processing with the target machine detection position obtained by the passive radar processing, and the target machine position information + the target machine information of the target machine detection time can be obtained (step). S17). Subsequently, the transmission station position information is acquired from the transmission station specifications by the transmission station transmission time estimation, and the time when the radar pulse is transmitted from the transmission station is estimated together with the target machine information obtained by the correlation processing (step). S18). The transmission time estimation result obtained in this way is placed under the control of the transmission station pulse timing (step S19), and is subsequently used for detecting the target machine during actual operation.

Therefore, according to the passive radar according to the present embodiment, the position of the target machine in actual operation can be specified even in an environment where the direct wave required for synchronization with the transmitting station cannot be obtained.

The present invention is not limited to the above-described embodiment as it is, and at the implementation stage, the components can be modified and embodied within a range that does not deviate from the gist thereof. In addition, various inventions can be formed by an appropriate combination of the plurality of components disclosed in the above-described embodiment. For example, some components may be removed from all the components shown in the embodiments. In addition, components across different embodiments may be combined as appropriate.

100 ... Passive radar, 101 ... First antenna unit, 102 ... Indirect wave signal processing unit, 103 ... Cumulative unit, 104 ... Synthesis unit, 105 ... Target machine position identification unit, 106 ... Second antenna unit, 107 ... Direct Wave signal processing unit, 108 ... Control unit. 200 ... Transmitting station.

Claims (4)

A passive radar device that detects the position of a target by receiving the indirect wave reflected by the target in an environment where the direct wave of the radar wave transmitted from a transmission station whose transmission specifications are known cannot be obtained. And
A passive radar processing unit that receives the indirect wave and detects a target based on the transmission specifications of the transmitting station.
A target location information acquisition unit that acquires location information and time information from a target that provides location information by communication,
The target position is estimated by correlating the target detection result obtained by the passive radar processing unit with the target information obtained by the target position information acquisition unit, and the transmission station position information is acquired from the transmission specifications of the transmission station. A passive radar including an information processing unit that estimates the pulse transmission time of the transmitting station from the position-estimated target position information and the target detection time, and manages the transmission station pulse timing using the transmission time estimation result. apparatus. The target position information acquisition unit targets a friendly aircraft or a civil aviation aircraft, and acquires position information with respect to the target time based on the response information of the SIF / IFF (Special Identification of Feature / Identification friend or foe) device. Passive radar device. The passive radar device according to claim 1, wherein the target position information acquisition unit adds position information with respect to the time to a communication signal and notifies the target to acquire the position information with respect to the target time. In an environment where direct waves of radar waves transmitted from transmission stations with known transmission specifications cannot be obtained.
The radar wave receives the indirect wave reflected by the target and receives the indirect wave.
Target detection is performed by passive radar processing based on the transmission specifications of the transmitting station.
Obtain location information and time information from a target that provides location information by communication,
The target position is estimated by correlating the target detection result obtained by the passive radar processing with the target information obtained by communication with the target, and the transmission station position information is acquired from the transmission specifications of the transmission station to estimate the position. A passive radar signal processing method that estimates the pulse transmission time of the transmission station from the target position information and the target detection time, and manages the transmission station pulse timing using the transmission time estimation result.

Images