JP4879761B2 - Radar equipment - Google Patents

Description

  The present invention relates to a radar device that is installed on the ground, on board, on a ship, and the like and detects a movement target such as an aircraft or a ship.

The functions of the detection radar include normal target detection (short-range target detection) and extremely long-range target detection. As an example of a radar device for super far-range target detection, the frequency of a pulse to be transmitted repeatedly from an antenna is changed for each pulse (for each hit), and the above change is made for the reflected wave of the target received by the antenna. There is one in which a plurality of receivers corresponding to each of a plurality of frequencies are demodulated, and each demodulated signal is numerically integrated to extract reflected waves of a plurality of orders from a target (for example, see Patent Document 1). ). According to this technique, since the order of the received signal is determined, the range ambiguity can be removed, and the processing time required for determining the distance can be improved.
The above technology is intended to improve the target detection processing method in the radar device that targets only the super far-distance target detection. However, in the actual radar device, the mode is switched to switch between the normal target detection and the super-distance target detection. Both functions are performed (for example, refer to Patent Document 2).

JP 2005-91174 A JP 2003-149323 A

In such a radar device having both functions of normal target detection and ultra-long distance target detection, for normal target detection, the number of pulse hits (number of pulses at one scan) is set to be greater than that at the time of ultra-long distance target detection. The clutter suppression performance is improved by performing multiple digital beam forming. On the other hand, for super far-distance target detection, since the target whose target speed is higher than the normal target is detected, the number of pulse hits is reduced compared to the case of normal target detection, and digital beamforming is made singular and range Doppler is used. We are trying to avoid an increase in walk loss. Therefore, in the case of a radar that performs mode switching between normal target detection and super far-distance target detection, a situation has occurred in which signal processing resources used for normal target detection remain at the time of super-distance target detection.
The range Doppler walk loss is as follows. Usually, in order to increase the detection distance of the radar, a plurality of pulses having coherency maintained with respect to the target are transmitted and received, and integration processing is performed. Since a plurality of pulses are transmitted / received, the target may move in the distance direction during the transmission / reception period, which may cause a loss in the integration process as compared with a case where the target does not move. This is called range walk loss. Further, with respect to the movement of the target with acceleration, a loss may be caused by integration in the Doppler direction. This is called Doppler walk loss. Both are collectively called Range Doppler Walk Loss.

  The present invention has been made to solve the above-described problems, and obtains a radar device that improves the angle measurement accuracy with respect to a super far-distance target by utilizing surplus signal processing resources when detecting the super-distance target. With the goal.

  The radar apparatus according to the present invention transmits a radio wave having a predetermined number of pulse hits at the time of normal target detection using a phased array antenna, receives a reflected wave from the target, and receives a digital reception signal obtained for each element antenna. Thus, simultaneous multi-beams are formed by performing digital beam forming using a plurality of reception beam processing systems including a beam forming unit, a target detection unit, and angle measurement processing, and can be obtained from reception beams by each reception beam processing system. In a radar device that obtains the final detection target and angle measurement result by correlating the angle measurement information and target amplitude information with the transmission beam in the correlation processing unit, the radio wave of the pencil beam with a smaller number of pulse hits than when detecting the target When detecting a far-distance target that transmits a signal, a plurality of receive beam processing systems are used to form a receive beam. Each angle measurement information and target amplitude information are obtained, and the correlation processing unit selects angle measurement information of the reception beam having the highest S / N from each angle measurement information obtained by a plurality of reception beam processing systems. The final angle measurement value is obtained by performing correlation processing with the transmission beam on the selected angle measurement information.

  According to the present invention, by using the signal processing resources that have been surplus at the time of detecting a very far distance target, the angle measurement accuracy at the time of detecting the far distance target is improved as compared with the case of using a single received beam processing system. Can be achieved.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a functional configuration of a radar apparatus according to each embodiment of the present invention.
In the figure, each part performs a known operation except that the processing in the correlation processing unit 11 is different at the time of detecting a very long distance target. The antenna unit 4 operates as a phased array antenna, and is a transmission / reception module including a circulator 41, a power amplifier 42, a low noise amplifier 43, a phase shifter 44, a transmission / reception switch 45, etc. for each of the plurality of element antennas 40. , As well as a power distribution unit 46 for each transmission / reception module.

First, the transmission operation will be described. The number of pulse hits and the beam shape of the transmission wave are different between the normal target detection and the ultra-long distance target detection, but the general transmission operation is generally the same.
The radar control unit 1 outputs a signal having a constant frequency to the excitation unit 2 and outputs beam directivity angle information to the antenna control unit 3. The radar control unit 1 outputs mode information to the signal processing control unit 8. The excitation unit 2 multiplies a signal having a constant frequency given from the radar control unit 1 at a constant repetition time and outputs the signal to the antenna unit 4. The antenna control unit 3 calculates each set phase of a signal to be supplied for each element antenna 40 according to the beam directivity angle information given from the radar control unit 1 and outputs it to the corresponding phase shifter 44 in the antenna unit 4. . The phase shifter 44 adjusts the phase of the transmission signal provided from the excitation unit 2 based on the set phase provided from the antenna control unit 3 in order to provide a beam directing angle for each element. The power amplifier 42 amplifies the power of the transmission signal whose phase has been adjusted, and applies the amplified signal to the element antenna 40 via the circulator 41. The element antenna 40 radiates a radio wave according to the beam directivity angle set by the phase shifter 44 toward the target.

Next, the reception operation will be described. In this case, although the correspondence operation of the correlation processing unit 11 is different between the normal target detection and the ultra-long distance target detection, the operations up to the preceding stage can be regarded as substantially the same.
In the signal processing control unit 8, on / off control and processing of operations of each beam forming unit 7, target detection unit 9, angle measurement processing unit 10, and correlation processing unit 10 based on the mode information given from the radar control unit 1. Take control.
When the element antenna 40 receives a reflected radio wave from a target of the transmitted radio wave, the element antenna 40 gives the received signal to the low noise amplifier 43 via the circulator 41. The signal amplified by the low noise amplifier 43 is subjected to phase adjustment between the elements by the phase shifter 44 and then given to the corresponding receiving unit 5 via the power distributor 46. Each receiving unit 5 down-converts the reception signal corresponding to each of the element antennas 40, further A / D converts it, and outputs it to the reception signal distribution unit 6. The reception signal distribution unit 6 distributes and outputs the digital reception signal from the reception unit 5 to a plurality of (four in this example) reception beam processing systems including the beam forming unit 7, the target detection unit 9, and the angle measurement process 10.

The four receive beam processing systems operate only one system at the time of conventional super far-distance target detection. However, according to the present invention, in both cases of normal target detection and ultra-distance target detection. Operate all systems.
The beam forming unit 7 of each processing system performs a discrete Fourier transform process on the digital reception signal distributed from the reception signal distribution unit 6 to perform digital beam forming, generate a reception multi-beam, and generate the beam data. Output to the target detection unit 9. The target detection unit 9 performs S / N improvement by pulse compression, integration processing, etc. on the received beam obtained by the beam forming unit 7, compares the threshold level with the target level, detects the target, and obtains the target information. Output to the angle measurement processing unit 10. The angle measurement processing unit 10 performs a process of calculating an angle at which the target exists in the beam based on the target information given from the target detection unit 9. The angle measurement information obtained by each angle measurement processing unit 10 and the target amplitude information obtained by the target detection unit 9 are output to the correlation processing unit 11.

  In the case of normal target detection, simultaneous multi-beams are formed by digital beam forming in order to increase the number of pulse hits in order to improve the clutter suppression performance. That is, four beam forming units 7a to 7d are used. The correlation processing unit 11 performs the same correlation processing as the conventional one based on the angle measurement information obtained by each angle measurement processing unit 10 and the target amplitude information obtained by the target detection unit 9 to obtain final target detection and angle measurement. I try to get results.

On the other hand, in the case of super far-distance target detection, the target whose target speed is higher than the normal target is detected, so if the number of pulse hits is the same as in normal target detection, range Doppler walk loss increases. Resulting in. Therefore, the conventional method suppresses the number of pulse hits, reduces the number of multi-beams, for example, the beam forming unit 7a, and operates the reception beam processing system of the target detection unit 9a and the angle measurement processing unit 10a. The Doppler walk loss was reduced. For this reason, the remaining three reception beam processing systems (the beam forming units 7b to 7d, the target detection units 9b to 9d, and the angle measurement processing units 10b to 10d) are inactive, and the resources remain when detecting a very long distance target. It was in a state.
In the present invention, in the case of super far-distance target detection, the transmission beam remains a pencil beam, the reception beam is formed also in the remaining three reception beam processing systems, target detection and angle measurement processing are performed, A plurality of angle measurement information is obtained for one transmission beam. The angle measurement accuracy is approximately inversely proportional to the S / N of the target signal (reception signal) if the reception beam width is constant. For this reason, the correlation processing unit 11 selects the angle measurement information of the reception beam having the highest S / N from each angle measurement information obtained from the reception beams generated by the four reception beam processing systems, and selects the selected measurement data. The angle information is correlated with the transmission beam to obtain a final angle measurement result. As a result, it is possible to improve the angle measurement accuracy at the time of detecting a very long distance target.

FIG. 2 shows an example of angle measurement accuracy simulation. As shown in the figure, accuracy cannot be improved in the vicinity of the beam nose. However, as there is no reception beam as the distance from the beam nose increases, the S / N deteriorates and the angle measurement accuracy also deteriorates. S / N degradation can be suppressed by this, and therefore the angle measurement accuracy is also improved. The processing of the correlation processing unit 11 at the time of detecting a very long distance target is expressed as follows.
σ = σ1 (when S / N1> S / N2, S / N3, S / N4)
σ2 (when S / N2> S / N1, S / N3, S / N4)
σ3 (when S / N3> S / N1, S / N2, S / N4)
σ4 (when S / N4> S / N1, S / N2, S / N3)
here,
σ: Final angle measurement value,
σ1: Angle value of received beam 1
σ2: Angle measurement value of received beam 2,
σ3: angle measurement value of the reception beam 3,
σ4: Angle measurement value of the reception beam 4,
S / N1: S / N of receive beam 1
S / N2: S / N of reception beam 2,
S / N3: S / N of the reception beam 3,
S / N4: The S / N of the reception beam 4 is set.

  As described above, according to the first embodiment, a plurality of reception beam processes used at the time of normal target detection at the time of very long distance target detection that transmits a pencil beam radio wave with a smaller number of pulse hits than at the time of normal target detection. Each of the systems is used to form a reception beam to obtain respective angle measurement information and target amplitude information. The correlation processing unit obtains the S / N of the angle measurement information obtained from the plurality of reception beam processing systems. The angle measurement information of the highest received beam is selected, and the final angle measurement value is obtained by performing correlation processing with the transmission beam on the selected angle measurement information. In addition, it is possible to improve the angle measurement accuracy at the time of detecting a super far distance target.

Embodiment 2. FIG.
In the first embodiment, among the received beam angle measurement information generated by the four received beam processing systems at the time of detecting a very long distance target, the angle measurement information of the received beam with the highest S / N is correlated. Although the processing is adopted as the target, the following processing may be performed.
The sum of weighted results of S / N for the angle measurement results of all received beams is set as the target of correlation processing. The processing of the correlation processing unit 11 according to the second embodiment is expressed as follows. In this case, the weighting value for the angle measurement information of each received beam is the ratio of the S / N of the own beam to the sum of the S / N of all the received beams.
σ = σ1 × K1 + σ2 × K2 + σ3 × K3 + σ4 × K4
here,
σ: Final angle measurement value,
σ1: Angle value of received beam 1
σ2: Angle measurement value of received beam 2,
σ3: angle measurement value of the reception beam 3,
σ4: Angle measurement value of the reception beam 4,
K1 = (S / N1) / (S / N1 + S / N2 + S / N3 + S / N4),
K2 = (S / N2) / (S / N1 + S / N2 + S / N3 + S / N4),
K3 = (S / N3) / (S / N1 + S / N2 + S / N3 + S / N4),
K4 = (S / N4) / (S / N1 + S / N2 + S / N3 + S / N4),
S / N1: S / N of receive beam 1
S / N2: S / N of reception beam 2,
S / N3: S / N of the reception beam 3,
S / N4: The S / N of the reception beam 4 is set.
The correlation processing unit 11 performs a correlation process with the transmission beam on the sum of the angle measurement information weighted as described above to obtain a final angle measurement value. Therefore, the accuracy can be improved as compared with the case of the first embodiment.

  In each of the above embodiments, digital beam forming in one dimension (azimuth direction or elevation angle direction) has been described, but it goes without saying that it can be similarly applied even if it is expanded in two dimensions.

It is a block diagram which shows the function structure of the radar apparatus by each embodiment of this invention. It is explanatory drawing which shows an example of the angle measurement precision simulation which concerns on Embodiment 1 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Radar control part, 2 excitation part, 3 antenna control part, 4 antenna, 5 reception part, 6 reception signal distribution part, 7 beam formation part, 8 signal processing control part, 9 target detection part, 10 angle measurement processing part, 11 Correlation processing unit, 40 multiple element antennas, 41 circulator, 42 power amplifier, 43 low noise amplifier, 44 phase shifter, 45 duplexer, 46 power distributor.

Claims (3)

When a target is detected using a phased array antenna, radio waves with a predetermined number of pulse hits are transmitted, reflected waves from the target are received, and a beam forming unit and target detection are performed on the digital received signal obtained for each element antenna. A multi-beam is formed by performing digital beam forming using a plurality of reception beam processing systems consisting of a reception unit and an angle measurement processing unit, and angle measurement information and target amplitude information obtained from the reception beam in each reception beam processing system In a radar apparatus that obtains a final detection target and an angle measurement result by performing correlation processing with a transmission beam in a correlation processing unit,
At the time of very long distance target detection in which a pencil beam radio wave is transmitted with a smaller number of pulse hits than at the time of the normal target detection, each of the angle measurement information and target Amplitude information is obtained, and the correlation processing unit selects angle measurement information of the reception beam having the highest S / N from each angle measurement information obtained by the plurality of reception beam processing systems, and the selected angle measurement information A radar apparatus characterized in that a final angle measurement value is obtained by performing a correlation process with a transmission beam on the. When a target is detected using a phased array antenna, radio waves with a predetermined number of pulse hits are transmitted, reflected waves from the target are received, and a beam forming unit and target detection are performed on the digital received signal obtained for each element antenna. Multi-beams are formed by digital beam forming using a plurality of receive beam processing systems consisting of a head and angle measurement processing, and angle measurement information and target amplitude information obtained from the receive beams in each receive beam processing system In a radar apparatus that obtains a final target detection and angle measurement result by performing correlation processing with a transmission beam in a correlation processing unit,
At the time of very long distance target detection in which a pencil beam radio wave is transmitted with a smaller number of pulse hits than at the time of the normal target detection, a plurality of reception beam processing systems are used to form reception beams, and each angle measurement information and target Amplitude information is obtained, and the correlation processing unit obtains the sum of angle measurement information obtained by weighting the angle measurement information of all reception beams obtained by the plurality of reception beam processing systems with S / N. A radar apparatus, wherein a final angle measurement value is obtained by performing correlation processing with a transmission beam on a sum of weighted angle measurement information.   3. The radar apparatus according to claim 2, wherein the weighting value for the angle measurement information of each received beam is a ratio of the S / N of the own beam to the sum of the S / N of all the received beams.

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