JP6523982B2 - Target detection device - Google Patents

Description

  The present invention relates to an aircraft target detection apparatus for detecting a plurality of targets by receiving a reflection signal from a target by pulse radio waves radiated into space.

  In the radar, as a method of detecting a target, a low pulse repetition frequency (LPRF) radar in which a time from transmission to reception of radio waves is sufficiently secured to a round trip distance to the target is used. Medium Pulse Repetition Frequency (MPRF) radar and High Pulse Repetition (HPRF: High Pulse) that have advanced the pulse repetition period (PRI) to improve detection performance and obtain target speed information Repetition Frequency) radar is used.

  The HPRF radar has a short pulse repetition period, and the number of reception gates provided is from one to several. The HPRF radar uses a narrow band filter for each receiving gate to lower the bandwidth and extract a target Doppler frequency to detect a target. (See Non-Patent Document 1).

George W. Stimson, "INTRODUCTION TO AIRBORNE RADAR Third Edition" Scitech Pub Inc, June 2013, P 419-P 427

  In HPRF radar, it is common to increase the ratio of the transmission period to the pulse repetition period PRI so that the target can be detected at a long distance. Therefore, one to two or so reception gates are common. In the HPRF radar, the relative distance to the target is calculated by FM ranging (see Non-Patent Document 1). Since this method does not have high distance accuracy, the flying object uses phase modulation and phase demodulation for distance information obtained from the platform to obtain the relative distance to the target with high accuracy.

  When multiple targets exist at a distance close to each other, the conventional method can accurately determine only one target at a time. When the relative velocity with each target was different for each target with HPRF radar, it was possible to separate targets with a Doppler filter and could detect multiple targets, but with HPRF radar, there were multiple targets with similar relative speeds. In order to separate targets with similar relative speeds, it is necessary to repeat the process for detecting targets while changing the position of the reception gate, so processing takes time and it is difficult to separate targets. Met.

  The present invention has been made in view of the above, and is a target detection device capable of detecting a plurality of targets in a short time even when a plurality of targets having the same relative velocity exist in close positions. The aim is to get

  In order to solve the problems described above and achieve an object, the present invention is a target detection device that receives a reflected wave of a signal emitted toward a target and detects the target. The target detection device generates a signal that radiates toward the target, radiates the generated signal toward the target, and receives a reflected wave of the signal radiated toward the target. In addition, the target detection device performs gate processing by setting different reception gates for signals obtained by frequency converting the received reflected wave and converting it into digital signals, and based on a plurality of gate processing results. Determine if there is a goal.

  According to the present invention, it is possible to detect a plurality of targets in a short time even when a plurality of targets having the same relative velocity exist at close positions.

A figure showing an example of composition of a target detecting device concerning an embodiment of the invention A time chart explaining target detection operation by a target detection device according to an embodiment of the present invention Diagram for explaining the demodulation operation according to the embodiment of the present invention The figure which shows an example of the target detection result concerning embodiment of this invention. The figure which shows an example of the processing circuit which implement | achieves the target detection apparatus concerning embodiment of this invention.

  Hereinafter, a target detection device according to an embodiment of the present invention will be described in detail based on the drawings. The present invention is not limited by the embodiment.

Embodiment.
FIG. 1 is a diagram showing an example of the configuration of a target detection apparatus according to an embodiment of the present invention.
The target detection device 100 includes a transmission signal generator 1 that generates a signal to be transmitted toward a target, a pulse modulator 2 that performs pulse modulation on an input signal, and a power amplifier 3 that amplifies the power of the input signal. When a phase modulator 4 that performs phase modulation on an input signal and a transmission signal to be transmitted toward a target are input, the signal is output to an antenna 6 described later and described later when a signal received by the antenna 6 is input The transmission / reception switching unit 5 outputs the signal to the frequency converter 7, and the antenna 6 emits a radio wave toward the target and receives a reflected wave that is a radio wave reflected by the target. Further, the target detection apparatus 100 includes a frequency converter 7 for converting the frequency of the input signal, an analog-digital (A / D) converter 8 for converting the input signal as an analog signal into a digital signal, and the input signal. and a plurality of gate processing unit 9 ₁ 9 _n to perform gate process to be described later, ₁ from a 10 _n plurality of Doppler compensation unit 10 for compensating for the Doppler shift of the input signal, and a plurality of narrow-band filter 11 ₁ 11 _n and an input signal from a plurality of Doppler filters 12 ₁ decomposed into frequency components 12 _n, and a plurality of target detection unit 13 ₁ 13 _n for obtaining the Doppler frequency of the target based on the input signal, when the phase modulation of the transmission signal Modulation and demodulation code generation unit 14 for generating a modulation pattern to be used for demodulation and a demodulation pattern to be used when demodulating a received signal, and a plurality of target detection units 13 ₁ , And 13 _n to determine a target based on the target Doppler frequency determined.

The transmission signal generator 1, the pulse modulator 2, the power amplifier 3, and the phase modulator 4 are transmission signal generation units that generate a signal that emits toward a target. Further, 10 _n from the Doppler compensation unit 10 _1, the narrowband filter 11 ₁ from 11 _n, from the Doppler filter 12 ₁ 12 _n, from the target detection unit 13 ₁ 13 _n, and the target determining unit 15, a plurality of gate processing unit a determining target determining unit whether a target on the basis of the gate processing results in each of the 9 ₁ 9 _n. Further, 10 _n from the Doppler compensation unit 10 _1, the narrowband filter 11 ₁ from 11 _n, 12 _n and the target detection unit 13 ₁ from 13 _n from the Doppler filter 12 ₁ constitute a plurality of target Doppler frequency extraction unit.

Subsequently, the overall operation of the target detection device 100 according to the present embodiment will be described. The transmission signal generator 1, the pulse modulator 2, a power amplifier 3, a phase modulator 4, duplexer 5, the gate processing unit 9 ₁ from 9 _n, the Doppler compensation unit 10 ₁ 10 _n, narrow-band filter 11 ₁ from 11 _n, 12 _n from Doppler filters 12 _1, and the target detection unit 13 operation of each component of ₁ to 13 _n, since the processing unit corresponding in conventional HPRF radar is similar to the operation performed, detailed operation Some explanations are omitted.

  In the target detection apparatus 100, the transmission signal generator 1 generates a coherent transmission signal to be transmitted toward the target, and outputs the coherent transmission signal to the pulse modulator 2. The pulse modulator 2 shapes the transmission signal input from the transmission signal generator 1 into a pulse and outputs the pulse to the power amplifier 3. The power amplifier 3 amplifies the power of the pulse-shaped transmission signal input from the pulse modulator 2 and outputs the amplified signal to the phase modulator 4. The phase modulator 4 performs phase modulation on the transmission signal input from the power amplifier 3 in accordance with the modulation pattern indicated by the modulation code output from the phase modulation and demodulation code generation unit 14. The transmission signal that has been phase-modulated by the phase modulator 4 is input to the antenna 6 via the transmission / reception switching unit 5, and the antenna 6 radiates the phase-modulated transmission signal into space.

A radio wave radiated from the target detection device 100 or the antenna 6 into space is reflected by the target and then received by the antenna 6. The antenna 6 inputs the received signal to the frequency converter 7 via the transmission / reception switching unit 5. The frequency converter 7 down-converts an RF (Radio Frequency) signal, which is an input received signal, to an IF (Intermediate Frequency) band and outputs it to the A / D converter 8, and the A / D converter 8 has a frequency The received signal input from the converter 7 is converted from an analog signal to a digital signal. The received signal converted into a digital signal by the A / D converter 8 is input to each of the gate processor 9 ₁ 9 _n. The gate processor 9 ₁ from 9 _n is the received gate shifting the data acquisition position i.e. data acquisition timing slightly. The gate processor 9 ₁ from 9 _n are gated to the received signal, specifically, from the received signal converted into a digital signal by the A / D converter 8, extracts the received data according to the data acquisition position set The extracted reception data is demodulated using the demodulation pattern indicated by the demodulation code output from the phase modulation and demodulation code generation unit 14. Position for extracting the received data from the input signal of the gate processor 9 ₁ from 9 _n from the A / D converter 8 is set separately from the gate processor 9 ₁ every 9 _n, each position are different from each other . Demodulation code phase modulation and the demodulation code generating unit 14 outputs to each of the gate processor 9 ₁ 9 _n are the same. Also, the demodulation code is the same as the modulation code that the phase modulation and demodulation code generation unit 14 outputs to the phase modulator 4.

Received data signal after each gate process from the gate processor 9 ₁ 9 _n has been performed is input from the Doppler compensation unit 10 ₁ in each of the 10 _n. The relative speed between each of the Doppler compensation unit 10 ₁ 10 _n is the input signal is a reception data signal gated, the relative speed between the own apparatus and the target, i.e. the target detection apparatus 100 and the target It performs compensation for canceling the influence of outputs from the narrow band filter 11 ₁ to 11 _n. Narrow band filter 11 ₁ from 11 _n is down-converts the received data signal input from an upstream of the Doppler compensation unit 10 ₁ from 10 _n to the video signal band. 12 _n from the Doppler filter 12 ₁ outputs the received data signal after being converted into a video signal band in front of the narrow-band filter 11 ₁ from 11 _n decomposed into the frequency components from the target detection unit 13 ₁ to 13 _n . Target detecting unit 13 ₁ from 13 _n, the target detection process on the input received data signal, specifically, executes the process of extracting the Doppler frequency of the target from the received data signal. 13 _n from the target detection unit 13 ₁ outputs a Doppler frequency of the target to the target determination processing unit 15. Target determination processing unit 15 performs the determination processing of the target by arranging the Doppler frequency input from each of the target detection unit 13 ₁ 13 _n in order of distance, to detect a target. That is, the target determination processing unit 15 determines whether or not the reflected wave which is a signal reflected by the target is received, and determines that the target is present when the reflected wave is received. At this time, the target determination processing unit 15 detects a plurality of targets if a plurality of targets exist.

  FIG. 2 is a time chart explaining the target detection operation by the target detection device 100 according to the present embodiment. FIG. 2 shows, as an example, an operation in the case where a 5-bit phase modulation code is used and the sub-pulse width is set to 1/3 of 1 bit of the phase modulation code. An example is shown in the case where targets # 1 and # 2 exist as targets. In FIG. 2, i and m are integers of 3 or more and n or less, and i <m.

  In FIG. 2, “0” and “π” indicate a phase modulation code, “π” of the phase modulation code indicates that the phase of the signal is rotated 180 °, and “0” indicates that the phase is not rotated. There is. That is, the phase modulation and demodulation code generation unit 14 of the target detection apparatus 100 outputs a modulation pattern combining "0" and "π" as a modulation code to the phase modulator 4, and the phase modulator 4 outputs According to the modulation code, the phase of the pulse transmission signal input from the amplifier 3 is output without rotating the phase or rotating the phase by 180 °.

Figure 3 is a diagram for explaining the demodulation operation of the gate processor 9 ₁ 9 _n performs. As described above, the radio wave radiated from the antenna 6 to the space is reflected by the target and then received by the antenna 6, and the frequency conversion process by the frequency converter 7 and the analog-to-digital conversion process by the A / D converter 8 are performed. after passing through, inputted from the gate processor 9 ₁ to 9 _n. After being radiated from the antenna 6, it is reflected by the target, an antenna 6, duplexer unit 5, the received signal inputted from the gate processor 9 ₁ to 9 _n via the frequency converter 7 and the A / D converter 8 It is a phase-modulated signal. Demodulation of the phase-modulated signal with the demodulation code results in FIG. Incidentally, the demodulation code is demodulated code outputted from the phase modulation and demodulating the code generator 14 from the gate processor 9 ₁ to 9 _n. As shown in FIG. 3, when the signal phase-modulated with modulation code "0" is demodulated with demodulation code "0", the signal after demodulation is "0" and the signal phase-modulated with modulation code "0" The signal after demodulation in the case of demodulation with the demodulation code "π" is "π", the signal in the case of phase modulation with the modulation code "π" being demodulated with the demodulation code "0" is "π" with the modulation code The signal after demodulation when the signal phase-modulated by “π” is demodulated by the demodulation code “π” is “0”. Thus, the signal after demodulation is "0" when the modulation code and the demodulation code match, and the signal after demodulation is "π" when the modulation code and the demodulation code do not match.

In FIG. 2, the signal in which the phase modulated transmission signal 21 is reflected at the target # 1 is received as a target # 1 reception signal 22, and the signal in which the transmission signal 21 is reflected at the target # 2 is the target # 2 reception signal 23. It shall be received as. The gate processor 9 _1, using the gate processing unit 9 ₁ demodulating signals 24 _1, the result of demodulating the target # 1 received signal 22 as the target # 1 receives and demodulates after signal 25 _1, target # 2 received signal as a result of demodulating the 23 target # 2 received demodulated after signal 26 _1. The gate processor 9 ₁ for demodulating the signal 24 ₁ is demodulated code outputted from the phase modulation and demodulating the code generator 14 to the gate processor 9 _1. Target # 1 receives and demodulates after signal 25 _1, compared to the original target # 1 received signal 22, is shorter, also not aligned in phase. Similarly the target # 2 received demodulated after signal 26 _1, compared to the original target # 2 received signal 23, is shorter, also not aligned in phase. Treatment of such signals in a narrow band filter 11 ₁ and Doppler filter 12 _1, the signal level is reduced.

When the gate section 9 _i demodulates the target # 1 received signal 22 using the gate processing unit 9 _i demodulating signal 24 _i, the target # 1 receives and demodulates after signal 25 _i is equal to the target # 1 received signal 22 Length And they are in phase. This is received signal subject to gating by the gating section 9 _i, that is, because it contains the component of the reflected wave is a modulated signal reflected by the target # 1 to signal embodying the demodulation process. Signal level is high when processing the target # 1 receives and demodulates after signal 25 _i in a narrow band filters 11 _i and Doppler filter 12 _i.

In addition, when the gate processing unit 9 _m demodulates the target # 2 reception signal 23 using the gate processing unit 9 _m demodulation signal 24 _m , the target # 2 reception demodulated signal 26 _m is equal to the target # 2 reception signal 23 It is long and in phase. When the target # 2 reception and demodulation signal 26 _m is processed by the narrowband filter 11 _m and the Doppler filter 12 _m , the signal level becomes high.

FIG. 4 shows a target detection result in the case where the target # 1 and the target # 2 are separated by 15 sub-pulse widths with the sub-pulse width being 1/10 of the 1-bit phase modulation code using a 13-bit phase modulation code. It is what arranged a certain Doppler frequency in order of distance. Distance, position each of the gate processor 9 ₁ 9 _n executes the gate processing on the received signal input from the A / D converter 8, i.e. corresponding to the position of the gate. In FIG. 4, the horizontal axis indicates the range gate number, and the vertical axis indicates the amplitude value. The range gate number is a number indicating the position of the gate. Shown in FIG. 4, obtained by arranging the target detection result is equivalent to a superposition side by side target Doppler frequency outputted from each of the target detection unit 13 ₁ 13 _n in order of distance. Target determination processing section 15 determines a target detection result input from each of the target detection unit 13 ₁ 13 _n, detects two target goals # 1 and # 2. The target determination processing unit 15 detects two targets, for example, by executing processing such as maximum value detection on target detection results of a certain level or higher.

  Although the example in the case of two targets was demonstrated in this Embodiment, it is possible to detect similarly also when a target is three or more. That is, the target determination processing unit 15 determines that there are a plurality of targets corresponding to each of the detected local maximum values when a plurality of local maximum values equal to or greater than a threshold value indicating a certain level are detected.

Transmission signal generator 1, pulse modulator 2, power amplifier 3, phase modulator 4, transmission / reception switching unit 5, frequency converter 7, A / D converter 8, gate processing unit of target detection apparatus 100 shown in FIG. 9 ₁ to 9 _n , Doppler compensation unit 10 ₁ to 10 _n , narrow band filter 11 ₁ to 11 _n , Doppler filter 12 ₁ to 12 _n , target detection units 13 ₁ to 13 _n , phase modulation and demodulation code generation unit 14 and The target determination processing unit 15 is realized by a processing circuit.

  That is, the target detection device 100 generates a transmission signal, performs pulse modulation and then amplifies it, further performs phase modulation to generate a signal to be transmitted toward the target, and frequency-converts the received signal. A processing circuit is provided which performs target determination after converting into digital signals and performing demodulation processing, Doppler compensation, narrow band filtering processing, and Doppler filtering processing using a plurality of different reception gates.

  The processing circuit included in the target detection device 100 is realized by dedicated hardware. The processing circuit may be, for example, a single circuit, a complex circuit, a programmed processor, a parallel programmed processor, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or a combination thereof. The CPU (Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, DSP (Digital Signal) that executes the program stored in the memory is a partial component of the target detection apparatus 100. Processor)).

  When some components of the target detection apparatus 100 are realized by a CPU that executes a program stored in a memory, those components are realized by the processing circuit 200 shown in FIG. FIG. 5 is a diagram showing an example of a processing circuit for realizing a part of components of the target detection apparatus 100 by the CPU. The processing circuit 200 includes a processor 201, a memory 202, an input circuit 203, and an output circuit 204. The memory 202 is a nonvolatile or volatile semiconductor such as a random access memory (RAM), a read only memory (ROM), a flash memory, an erasable programmable read only memory (EPROM), and an electrically erasable programmable read only memory (EEPROM). Memory, magnetic disk, flexible disk, optical disk, compact disk, mini disk, DVD (Digital Versatile Disc), and the like.

  In the processing circuit 200, the processor 201 reads a program for operating as each unit realized by the processing circuit 200 from the memory 202 and executes the program to realize the function of each unit. The input circuit 203 is used when externally receiving a signal processed by the processor 201, and the output circuit 204 is used when outputting the processing result of the processor 201 to the outside.

As described above, the target detection device according to the present embodiment has a plurality of reception gates, performs gate processing at different timings for each reception gate, performs target detection, and generates a plurality of target detection results. , And to determine the presence or absence of a reflected signal from the target. As a result, even in the state where a plurality of targets having the same relative velocity exist at close positions, a plurality of targets can be detected in a short time. Further, since to that branches the received signal after converting the received signal to be input from a plurality of gate processor 9 ₁ to 9 _n to a digital signal, to prevent the signal-to-noise ratio is deteriorated, detection distance Performance degradation can be avoided.

Here, if, from the target detection apparatus 100 shown in FIG. 1, 9 _n gate unit 9 _2, 10 _n from the Doppler compensation unit 10 _2, the narrow band filter 11 ₂ from 11 _n, Doppler filter 12 ₂ from 12 _n and when from the target detection unit 13 ₂ and the configuration in which the 13 _n, i.e., provided with a gate unit 9 ₁ only target detection unit 13 _1, the target detection unit 13 ₁ from the set of gate processor 9 ₁ It is theoretically possible to detect multiple targets that are in close proximity and have similar relative speeds by using and repeating the process multiple times. However, detection is possible only under certain limited conditions, and even if it can be detected, the time required for detection increases, and it is difficult to improve target detection performance.

  For example, when the transmission pulse width is 1 μs, the duty is 33%, and the distance separation performance is 15 m, the reception gate needs to repeat the target detection process while shifting in 100 ns units, and 29 processes are tried to verify the entire reception area. There is a need to. If the time required for one target detection process is 100 ms, it takes 2.9 seconds to complete the process. Therefore, if the relative velocity with respect to the target is 900 m / s, it moves 2610 m in 2.9 seconds, and it exceeds the distance 450 m that can be expressed by PRI, making separation difficult.

In the case where the gate processing unit 9 ₂ 9 _n was an analog circuit, A / D converter 8 preceding the analog circuit portion is increased, the circuit scale becomes large. However, the target detection apparatus of this embodiment, by the gate processor 9 ₂ from 9 _n connected in parallel to a rear stage of the A / D converter 8 to a digital circuit, is possible to configure the circuit scale small it can.

  The configuration shown in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and one of the configurations is possible within the scope of the present invention. Parts can be omitted or changed.

1 transmit signal generator, 2 a pulse modulator, 3 a power amplifier, quadrature phase modulator, 5 reception switching section, 6 antenna, 7 a frequency converter, 8 analog to digital (A / D) converter, 9 ₁ from 9 _n gate processing unit, 10 ₁ from 10 _n Doppler compensation unit, 11 ₁ from 11 _n narrow band filters, 12 ₁ from 12 _n Doppler filter, 13 _n target detecting unit 13 _1, 14 phase modulation and demodulating code generator, 15 a target determination Processing unit, 100 Target detection device.

Claims (1)

A target detection device that receives a reflected wave of a signal emitted toward a target and detects the target,
A transmission signal generator for generating a phase modulated transmission signal that radiates toward a target;
An antenna that radiates the transmission signal generated by the transmission signal generation unit toward a target and receives a reflected wave of the transmission signal emitted toward the target;
A signal obtained by frequency-converting the reflected wave received by the antenna and converting it into a digital signal is input, and different reception gates are set for the input signal to correspond to the transmission signal. A plurality of gate processing units that perform gate processing at different data acquisition timings based on the same demodulation code ;
A target determination unit that determines the presence or absence of a target based on gate processing results in each of the plurality of gate processing units;
Equipped with
The target determination unit
Each of the plurality of gate processing units is disposed one after the other, and conversion to the video signal band and decomposition into frequency components are performed on the gate processing result in the gate processing unit of the previous stage, and further, a target Doppler A plurality of target Doppler frequency extraction units as many as the plurality of gate processing units for extracting a frequency;
A target determination processing unit that determines the presence or absence of a target by thresholding the target Doppler frequency extracted by each of the plurality of target Doppler frequency extraction units;
A target detection device comprising:

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