JP2005195339A - Radar signal processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radar signal processing apparatus capable of detecting a target which is existing in the arrival direction of interference wave, even without concentrating whole transmission energy. <P>SOLUTION: The radar signal processing apparatus comprises a transmitter 10, 11 for transmitting a pulse signal; a receiver 15 for receiving the reflected wave to the transmitted pulse signal transmitted from the transmitter and the incoming wave under the main lobe environment containing interference wave coming from nearly arrival direction of the reflected wave; a MUSIC (multiple signal classification) processor 16 for generating MUSIC spectrum by processing the received signal by the MUSIC method based on the incoming wave received by the receiver; and a target detection processor 17 for detecting the target based on the number of peaks and the peak existing angle in the MUSIC spectrum generated in the MUSIC processor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radar signal processing device, and more particularly to a radar signal processing device that detects a target in a main lobe interference environment using a MUSIC (Multiple Signal Classification) method.

  Conventionally, a radar signal processing device used in a radar device is known. This radar signal processing apparatus extracts a Doppler component due to movement of a target by processing a reception signal obtained by reflecting a transmission pulse transmitted toward the target and reflecting the target, and sets a target moving based on the Doppler component. Detected.

  The configuration of such a conventional radar signal processing apparatus is shown in FIG. This radar signal processing apparatus includes a transmitter 1, a circulator 2, an antenna 3, a receiver 4, and a signal processing unit 5. The signal processing unit 5 further includes a pulse compression processing unit 51, a discrete Fourier transform (DFT) processing unit 52, and a target detection / angle measurement / range measurement processing unit 53.

  The transmitter 1 mixes a transmission type signal (chirp signal) as a wide pulse width signal whose frequency band is expanded by modulation and a local signal, converts the signal into a high frequency signal, amplifies it to a predetermined level, and sends it to the circulator 2. .

  The circulator 2 switches whether to output the high-frequency signal from the transmitter 1 to the antenna 3 or to output the reception signal from the antenna 2 to the receiver 4. The antenna 3 is composed of an array antenna, for example, and transmits a high-frequency signal input from the transmitter 1 via the circulator 2 toward the target, receives a reflected wave from the target, and sends the received signal to the circulator 2. Output.

  The receiver 4 amplifies the received signal input from the antenna 3 via the circulator 2 with low noise, converts the amplified signal into an intermediate frequency signal, and further A / D converts the signal to generate an orthogonal digital (I, Q) signal X ( t) (hereinafter simply referred to as “signal X (t)”). The signal X (t) obtained by the receiver 4 is sent to the pulse compression processing unit 51.

The pulse compression processing unit 51 performs pulse compression processing on the signal X (t) from the receiver 4. Pulse compression is a technology that converts a wide pulse width signal whose frequency band has been expanded by modulation during transmission to a narrow pulse width signal by correlation processing in the range (distance) direction during reception, and is received after the pulse is transmitted. And the received pulse signal is a function X (t-tj) of the time t, and this is multiplied by the reference signal X ^* (-t) ( ^* : complex conjugate) in the frequency domain. By making the phase component of the spectrum constant over the entire frequency and returning it to the time domain, the signal energy is concentrated in one place and converted into a narrow pulse width signal.

A discrete Fourier transform (DFT) processing unit 52 performs discrete Fourier transform on the signal from the pulse compression processing unit 51 to convert time data into frequency data, and a target detection / angle measurement / range measurement processing unit 53. Send to. That is, in order to detect the target relative speed, the received signal is decomposed into a Doppler component which is a target speed component and sent to the target detection / angle measurement / range measurement processing unit 53. The target detection / angle measuring / ranging processing unit 53 extracts a moving target by extracting the Doppler component from the DFT processing unit 51, and performs angle measuring and ranging (see Patent Document 1).
JP-A-4-357485

  In the conventional radar signal processing apparatus described above, in a main lobe interference environment where an interference wave exists with respect to the main lobe, as shown in FIG. 5A, the reflected wave from the target is buried in the interference wave. Unable to detect the goal. Therefore, as shown in FIG. 5 (b), the signal power to jamming power ratio is increased by a burn-through method in which transmission energy is concentrated on a target in the arrival direction of the jamming wave, that is, the number of pulse hits in the target direction is increased. (S / J ratio) is improved and target detection is performed.

  However, since this method requires a large amount of transmission energy to improve the S / J ratio, in some cases, it is necessary to concentrate all the transmission energy only on the target in the direction of arrival of the jamming wave. However, there is a problem that searching in other directions becomes impossible.

  The present invention has been made to solve the above-described problem, and radar signal processing capable of detecting a target in the direction of arrival of an interference wave without concentrating all transmission energy. To provide an apparatus.

  In order to solve the above-described problem, the radar apparatus signal processing according to the present invention includes a transmitter that transmits a pulse signal, a reflected wave with respect to the pulse signal transmitted from the transmitter, and a direction close to the arrival direction of the reflected wave. A MUSIC process for generating a MUSIC spectrum by processing a receiver that receives an incoming wave in a main lobe environment including an incoming disturbing wave, and a received signal based on the incoming wave received by the receiver using the MUSIC method And a target detection processor for detecting a target based on the number of peaks of the MUSIC spectrum generated by the MUSIC processor and the angle at which the peaks exist.

  Further, the target detection processor determines that the second peak corresponds to the reflected wave when the MUSIC spectrum generated by the MUSIC processor has a second peak in addition to the first peak corresponding to the interference wave. Recognizing and estimating a target azimuth based on the angle of the second peak.

  The target detection processor detects the number of the MUSIC spectrum generated by the MUSIC processor and the angle at which the first peak and the second peak exist in a range bin unit, and based on the range bin in which the second peak is detected. The distance is calculated.

  According to the radar signal processing apparatus of the present invention, since the target is detected based on the number of peaks of the MUSIC spectrum and the angle at which the peaks exist, the total transmission energy is reduced with respect to the target in the arrival direction of the jamming wave. A radar signal processing apparatus capable of detecting the target without being concentrated can be provided.

  Hereinafter, a radar signal processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a radar signal processing apparatus according to an embodiment of the present invention. The radar signal processing apparatus includes a transmitter 10, a distributor 11, K phase shifters 12 _{1 to} 12 _K (K is a positive integer), K circulators 13 _{1 to} 13 _K , and K antenna elements 14. _It comprises an array antenna 14 consisting of _{1 to} 14 _K , a receiver 15, a MUSIC processor 16 and a target detection processor 17.

  The transmitter 10 generates a pulse signal to be transmitted toward the target. The pulse signal generated by the transmitter 10 is sent to the distributor 11.

The distributor 11 distributes the pulse signal sent from the transmitter 10 to the phase shifters 12 _{1 to} 12 _K.

The phase shifters 12 _{1 to} 12 _K adjust the phase shifts of the pulse signals distributed by the distributor 11 and send them to the circulators 13 _{1 to} 13 _K as transmission signals, respectively.

The circulators 13 _{1 to} 13 _K output transmission signals output from the phase shifters 12 _{1 to} 12 _K to the antenna elements 14 _{1 to} 14 _K constituting the array antenna 14, or output from the antenna elements 14 _{1 to} 14 _K. Whether to output the received signal to the receiver 15 is switched.

The antenna elements 14 _{1 to} 14 _K transmit the transmission signals input from the distributor 11 via the phase shifters 12 _{1 to} 12 _n and the circulators 13 _{1 to} 13 _K , respectively, toward the target, and the reflected waves from the target And the received signal is output to the receiver 15 via the circulators 13 _{1 to} 13 _K.

The receiver 15 amplifies the received signal transmitted from the antenna elements 14 _{1 to} 14 _K via the circulators 13 _{1 to} 13 _K with low noise, frequency-converts this to an intermediate frequency, and further performs A / D conversion. Thus, an orthogonal digital (I, Q) signal Xm (t) is obtained for each of the antenna elements 14 _{1 to} 14 _K. This signal Xm (t) represents a received signal from the mth antenna element at time t and is sent to the MUSIC processor 16. As Xm (t), a signal in a subarray configuration can also be used.

  The MUSIC processor 16 generates a MUSIC spectrum PMU (θ) for estimating the arrival direction of the incident wave according to the MUSIC method. Hereinafter, the MUSIC method will be briefly described. Details of the MUSIC method can be found in, for example, Nobuyoshi Kikuma, “Adaptive signal processing using an array antenna”, Science and Technology Publishing (1999) pp. Reference is made as necessary.

In this MUSIC method, eigenvalues and eigenvectors of a correlation matrix are used. The correlation matrix Rxx is expressed by the following formula (1).

  Here, E [] represents a first-order moment, Xm (t) represents a received signal from the m-th antenna element at time t, and H represents a complex conjugate transpose.

Assuming that the eigenvalue of the correlation matrix Rxx is λ _i (i = 1, 2,... K), the eigenvector corresponding to the eigenvalue is e _i, and the arrival wave (plane wave) of the L wave arrives, 2) holds.

Here, σ ² is thermal noise power.

At this time, eigenvectors {e ₁ , e ₂ ,..., E _L }, {e _{L + 1} ,..., E _K } span a signal subspace and a noise subspace. Therefore, when the MUSIC spectrum PMU (θ) is defined as the following equation (3), the arrival direction can be estimated by searching for the peak of the MUSIC spectrum PMU (θ).

Here, a (θ) is a direction vector. E _N is an eigenvector and is given by the following equation (4).

  The MUSIC processor 16 generates a MUSIC spectrum PMU (θ) in sampling time units (range bin units) in accordance with the above-described MUSIC method. Specifically, as shown in a region A surrounded by a broken line in FIG. 2A, when only a disturbing wave is received without a reflected wave from the target, FIG. As shown, a MUSIC spectrum PMU (θ) having a peak in the direction (angle) of the interference wave is generated.

  On the other hand, when both the reflected wave and the disturbing wave from the target are received as shown in the region B surrounded by the solid line in FIG. 2A, the disturbing wave is received as shown in FIG. A MUSIC spectrum PMU (θ) having a first peak in the arrival direction and a second peak in the arrival direction of the reflected wave is generated. The MUSIC spectrum PMU (θ) generated by the MUSIC processor 16 is sent to the target detection processor 17.

  The target detection processor 17 executes target detection processing based on the MUSIC spectrum PMU (θ) sent from the MUSIC processor 16 in sampling time units (range bin units). That is, the target detection processor 17 compares the value of the MUSIC spectrum PMU (θ) with a predetermined threshold value for each range bin, and the MUSIC spectrum PMU (θ) exceeding the threshold value, that is, the number of peaks, the angle, and the current time. Target detection is performed by the range bin.

  Specifically, as shown in FIG. 2B, when a MUSIC spectrum PMU (θ) having one peak is continuously obtained, only the interference wave is received from the angle of the peak. And the target detection process is not executed.

  On the other hand, as shown in FIG. 2C, when a continuous first peak and a short second peak are obtained, an interference wave is received from the angle of the first peak and the angle of the second peak. It recognizes that the reflected wave is received from, and executes target detection processing for the second peak. That is, the target direction is determined based on the angle of the second peak, and the distance to the target is determined based on the range bin where the second peak appears.

  FIG. 3 conceptually shows the determination result output by the target detection processor 17. When an interference wave exists, the arrival direction of the interference wave is indicated by the level. When the target does not exist, the fact is displayed at a predetermined level. When the target exists, the direction of the target is indicated by the level that changes according to the arrival direction of the reflected wave, and the level change point from the origin. The distance to the target indicates the distance to the target.

  As described above, the radar signal processing apparatus according to the embodiment of the present invention estimates the target arrival direction based on the number of peaks of the MUSIC spectrum PMU (θ) and the angle at which the peaks exist, Since the target is detected based on the arrival direction of the target, the target can be detected without concentrating the total transmission energy with respect to the target in the direction of arrival of the jamming wave. Etc. becomes possible.

  In the above-described embodiment, the MUSIC spectrum PMU (θ) is generated in sampling time units (range bin units). However, the average processing in the range bin direction is performed, and the MUSIC spectrum subjected to the average processing is performed. It can also be configured to detect the target based on PMU (θ). In this case, the distance to the target can be calculated based on the time from when the pulse signal is transmitted until the reflected wave is received.

  The present invention can be applied to a pulse radar apparatus that detects a target by transmitting a pulse signal.

It is a block diagram which shows the structure of the radar signal processing apparatus which concerns on embodiment of this invention. It is a figure for demonstrating operation | movement of the radar signal processing apparatus which concerns on embodiment of this invention. It is a figure for demonstrating the output of the target detection processor in the radar signal processing apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structure of the conventional radar signal processing apparatus. It is a figure for demonstrating operation | movement of the conventional radar signal processing apparatus.

Explanation of symbols

10 transmitter 11 divider ₁₂ 1 to 12 _K phase shifter ₁₃ 1 to 13 _K circulator 14 array antenna ₁₄ 1 to 14 _K antenna elements 15 receiver 16 MUSIC processor 17 target detecting processor

Claims (3)

A transmitter for transmitting a pulse signal;
A receiver for receiving an incoming wave in a main lobe environment including a reflected wave with respect to a pulse signal transmitted from the transmitter and an interference wave coming from a direction close to the arrival direction of the reflected wave;
A MUSIC processor that generates a MUSIC spectrum by processing a received signal based on an incoming wave received by the receiver using a MUSIC method;
A target detection processor for detecting a target based on the number of peaks of the MUSIC spectrum generated by the MUSIC processor and the angle at which the peaks exist;
A radar signal processing apparatus comprising:   The target detection processor determines that the second peak corresponds to the reflected wave when the MUSIC spectrum generated by the MUSIC processor includes a second peak in addition to the first peak corresponding to the interference wave. 2. The radar signal processing apparatus according to claim 1, wherein the radar signal processing apparatus recognizes and estimates a target direction based on an angle of the second peak.   The target detection processor detects the number of MUSIC spectra generated by the MUSIC processor and the angle at which the first peak and the second peak exist in a range bin unit, and sets the target based on the range bin in which the second peak is detected. The radar signal processing apparatus according to claim 2, wherein the distance to is calculated.

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