JP6218476B2 - Radar equipment - Google Patents

Description

  The present invention relates to a radar apparatus constituting a multi-channel SAR that improves S / N by digital beam forming.

  Multi-channel SAR is a means for enhancing the functionality of a synthetic aperture radar (SAR). This multi-channel SAR realizes moving target detection (MTI), interference SAR for height estimation (InSAR), and high resolution wide-width (HRWS). ing. At this time, in the conventional multi-channel SAR, the above functions have been realized by providing a plurality of receiving devices (see, for example, Non-Patent Documents 1 to 3).

G. Krieger, N. Gebert, A. Moreira, “Unambiguous SAR signal reconstruction from nonuniform displaced phase center sampling”, IEEE Geoscience and Remote Sensing Letters, Vol. 1, issue: 4, pp. 260-264, 2004. P. Berens, ARBrenner, L. Rossing, U. Skupin, “Multi-channel SAR / MTI system development at FGAN: from AER to PAMIR”, IEEE International Geoscience and Remote Sensing Symposium, IGARSS 2002, vol. 3, pp. 1967-1701, 2002. S. Lehner, R. Bamler, J. Horstmann, “A model for ocean wave imaging by a single pass cross track interferometric SAR (InSAR) -the SINEWAVE experiment”, IEEE International Geoscience and Remote Sensing Symposium, IGARSS 2002, vol. , pp.962-964,1998. M. Younis, S. Huber, A. Patyuchenko, F. Bordoni and G. Krieger “Digital beam-forming for spaceborne reflector-and planar-antenna SAR-A system performance comparison”, IGARSS 2009, vol. 3, pp. 733 -736, July 2009. Lan G. Cumming and Frank H. Wong, “digital processing of SYNTHETIC APERTURE RA / DAR”, ARTECH HOUSE Gharles V. Jakowatz Jr., Daniel E. Wahl, Palu H. Eichel, Dennis C. Ghiglia and Paul A. Thompson, “SPOTLIGHT-MODE SYNTHETIC APERTURE RA / DAR: A SIGNAL PROCESSING APPROACH”, KLUWER ACA / DEMIC PUBLISHERS

  On the other hand, a SAR that improves S / N (Signal to Noise power ratio) by digital beam forming (DBF) in a receiving apparatus has been studied (for example, see Non-Patent Document 4). However, in this case, if a plurality of receiving apparatuses that perform DBF are provided in order to configure a multi-channel SAR, there is a problem that the cost of the entire radar apparatus increases.

  The present invention has been made to solve the above-described problems, and in a radar apparatus constituting a multi-channel SAR that improves S / N by digital beam forming, the increase in the cost of the entire apparatus can be mitigated. An object of the present invention is to provide a radar device that can be used.

The radar apparatus according to the present invention outputs a transmission pulse that is up-converted using local oscillation signals from the same local oscillator, and outputs a plurality of transmission apparatuses having different phase centers of the output transmission pulse to the received signal. Down-converting using the local oscillation signal from the local oscillator and performing digital beam formation so that the phase center of the reception beam for receiving the echo for the transmission pulse output by each transmission device is single. Device.

Further, the radar apparatus according to the present invention outputs a transmission pulse that is up-converted by using local oscillation signals from the same local oscillator, and includes a plurality of transmission apparatuses having different phase centers of output transmission pulses, and a transmission apparatus. A small number is provided, and the received signals are down-converted by using the local oscillation signal from the local oscillator so that the reception beams for receiving the echoes for the transmission pulses output by the respective transmission devices become single. And a plurality of receiving devices that perform digital beam forming.

  According to the present invention, since it is configured as described above, an increase in the cost of the entire apparatus can be mitigated in a radar apparatus that constitutes a multi-channel SAR that improves S / N by digital beam forming.

It is a figure which shows the structure of the radar apparatus of the multichannel SAR system which concerns on Embodiment 1 of this invention. It is a flowchart which shows the process sequence of the radar apparatus of the multichannel SAR system which concerns on Embodiment 1 of this invention. It is a figure explaining the formation of the beam by the DBF process of the digital beam formation part in Embodiment 1 of this invention. It is a timing chart which shows the relationship between the transmission timing of the transmission pulse by the radar apparatus of the multichannel SAR system concerning Embodiment 1 of this invention, and the observation time of a receiving beam. It is a figure which shows another structure of the radar apparatus of the multichannel SAR system which concerns on Embodiment 1 of this invention. It is a figure which shows another structure of the radar apparatus of the multichannel SAR system which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the radar apparatus of the multichannel SAR system which concerns on Embodiment 2 of this invention. It is a figure explaining the formation of the beam by the DBF process of the digital beam forming part in Embodiment 2 of this invention. It is a timing chart which shows the relationship between the transmission time of the transmission pulse by the radar apparatus of the multichannel SAR system concerning Embodiment 2 of this invention, and the observation time of a received beam. It is a figure which shows another structure of the radar apparatus of the multichannel SAR system which concerns on Embodiment 2 of this invention. It is a figure which shows another structure of the radar apparatus of the multichannel SAR system which concerns on Embodiment 2 of this invention. It is a figure which shows the structure of the radar apparatus of the multichannel SAR system which concerns on Embodiment 3 of this invention. It is a figure explaining the formation of the beam by the DBF process of the digital beam formation part in Embodiment 3 of this invention. It is a timing chart which shows the relationship between the transmission time of the transmission pulse by the radar apparatus of the multichannel SAR system concerning Embodiment 3 of this invention, and the observation time of a received beam. It is a figure which shows the structure of the radar apparatus of the multichannel SAR system which concerns on Embodiment 4 of this invention. It is a figure explaining the formation of the beam by the DBF process of the digital beam forming part in Embodiment 4 of this invention. It is a timing chart which shows the relationship between the transmission time of the transmission pulse by the radar apparatus of the multichannel SAR system which concerns on Embodiment 4 of this invention, and the observation time of a receiving beam.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
In the first embodiment, a radar apparatus of a multi-channel SAR system that includes two transmission apparatuses 2 and one reception apparatus 5 that performs DBF and performs MTI will be described. 1 is a diagram showing a configuration of a radar apparatus of a multi-channel SAR system according to Embodiment 1 of the present invention.
The radar apparatus of the multi-channel SAR system performs target observation while moving at a constant speed in order to realize a synthetic aperture. As shown in FIG. 2-2, two transmission antennas 3-1 and 3-2, N reception antennas 4-1 to 4 -N, and one reception device 5.

The local oscillator 1 outputs a local oscillation signal having a predetermined frequency.
The transmission devices 2-1 and 2-2 output transmission pulses (signals) 11-1 and 11-2. It is assumed that the transmission apparatuses 2-1 and 2-2 have different phase centers of the transmission pulses 11-1 and 11-2. The configuration of the transmission devices 2-1 and 2-2 will be described later.
The transmission antennas 3-1 and 3-2 transmit the transmission pulses 11-1 and 11-2 from the corresponding transmission apparatuses 2-1 and 2-2 to the outside (target).

The receiving antennas 4-1 to 4-N receive echoes (signals) 12-1 and 12-2 for the transmission pulses 11-1 and 11-2 transmitted from the outside by the transmitting antennas 3-1 and 3-2. Is.
The receiving device 5 processes the echoes 12-1 and 12-2 received by the receiving antennas 4-1 to 4-N. At this time, the reception device 5 receives the reception beams 13-1 and 13-2 that receive the echoes 12-1 and 12-2 with respect to the transmission pulses 11-1 and 11-2 transmitted by the transmission devices 2-1 and 2-2. DBF is performed so that the phase center of −2 becomes single. The configuration of the receiving device 5 will be described later.

Next, the configuration of the transmission devices 2-1 and 2-2 will be described. In the following, the configuration of the transmission device 2-1 will be described, but the configuration of the transmission device 2-2 is the same.
As illustrated in FIG. 1, the transmission device 2-1 includes a signal generation unit 201-1, a multiplier 202-1, and an amplifier 203-1.

The signal generation unit 201-1 generates a chirp pulse. At this time, the signal generation unit 201-1 sets the pulse repetition period (PRI) as unequal intervals, and transmits transmission pulses 11-1 and 11-2 alternately from the transmission devices 2-1 and 2-2 for each PRI. A chirp pulse is generated to
The multiplier 202-1 uses the local oscillation signal output from the local oscillator 1 to up-convert the signal generated by the signal generation unit 201-1.

  The amplifier 203-1 amplifies the signal up-converted by the multiplier 202-1. The signal (transmission pulse 11-1) amplified by the amplifier 203-1 is output to the corresponding transmission antenna 3-1.

Next, the configuration of the receiving device 5 will be described.
As illustrated in FIG. 1, the reception device 5 includes amplifiers 501-1 to 501-N, multipliers 502-1 to 502-N, A / D converters 503-1 to 503-N, and a digital beam forming unit 504. Has been. Note that although the receiving device 5 has a plurality of receiving systems, there is only one corresponding to the phase center of signals (received beams 13-1 and 13-2) obtained by combining the outputs of these systems. , One device.

The amplifiers 501-1 to 501-N amplify signals (echoes 12-1 and 12-2) received by the corresponding receiving antennas 4-1 to 4-N.
The multipliers 502-1 to 502-N downconvert the signals amplified by the amplifiers 501-1 to 501-N using the local oscillation signal output from the local oscillator 1.

  The A / D converters 503-1 to 503-N perform digitization by performing A / D conversion on the signals down-converted by the multipliers 502-1 to 502-N.

The digital beam forming unit 504 forms the reception beams 13-1 and 13-2 by performing DBF on the signals digitized by the A / D converters 503-1 to 503-N. Here, the reception beams 13-1 and 13-2 are reception beams obtained by observing the echoes 12-1 and 12-2 simultaneously. The reception beams 13-1 and 13-2 formed by the digital beam forming unit 504 are radar signals of the multi-channel SAR system as raw data 14-1 and 14-2 corresponding to the transmission antennas 3-1 and 3-2. The data is output to a processing device (not shown) and processed.
In addition, when it is not necessary to distinguish in particular, description after the hyphen which shows a system | strain among each code | symbol is abbreviate | omitted.

Next, the processing procedure of the radar apparatus of the multi-channel SAR system configured as described above will be described with reference to FIG. First, the transmission operation of the radar apparatus will be described.
In the transmission operation of the radar apparatus, as shown in FIG. 2, first, the signal generation units 201-1 and 201-2 of the transmission apparatuses 2-1 and 2-2 generate chirp pulses (step ST201). Note that the PRIs at this time are unequal intervals.

Next, multipliers 202-1 and 202-2 use the local oscillation signal output from local oscillator 1 to up-convert signals generated by signal generation units 201-1 and 201-2 (step ST202). .
Next, amplifiers 203-1 and 203-2 amplify the signals up-converted by multipliers 202-1 and 202-2 (step ST203).

  Next, the transmission antennas 3-1 and 3-2 alternately transmit the signals (transmission pulses 11-1 and 11-11) amplified by the amplifiers 203-1 and 203-2 of the corresponding transmission devices 2-1 and 2-2. 2) is sent to the outside (step ST204).

Next, the reception operation of the radar apparatus will be described.
In the receiving operation of the radar apparatus, first, the receiving antennas 4-1 to 4-N return echoes 12-1 and 12- to the transmission pulses 11-1 and 11-2 transmitted by the transmitting antennas 3-1 and 3-2. 2 is received (step ST205).

Next, amplifiers 501-1 to 501-N of receiving apparatus 5 amplify signals (echoes 12-1 and 12-2) received by corresponding receiving antennas 4-1 to 4-N (step ST206).
Next, multipliers 502-1 to 502-N downconvert the signals amplified by corresponding amplifiers 501-1 to 501-N using the local oscillation signal output from local oscillator 1 (step ST207). .

Next, A / D converters 503-1 to 503-N perform digitization by performing A / D conversion on the signals down-converted by corresponding multipliers 502-1 to 502-N (step ST208). ).
Next, digital beam forming section 504 forms received beams 13-1 and 13-2 by performing DBF on the signals digitized by A / D converters 503-1 to 503-N (step ST209). ).

  Here, the DBF processing of the digital beam forming unit 504 will be described with reference to FIGS. 3 shows transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2 and echoes 12-1 and 12 received by the reception antennas 4-1 to 4-N. 2 is a diagram illustrating a relationship between the reception beam 13-1 and the reception beam 13-2 formed by the digital beam forming unit 504 of the reception device 5. Actually, transmission of the transmission pulses 11-1 and 11-2 from the transmission antennas 3-1 and 3-2 and observation of the echoes 12-1 and 12-2 by the reception beams 13-1 and 13-2 are not performed simultaneously. Although not performed, they are shown together for convenience in this figure. FIG. 4 is a diagram showing the relationship between the transmission timings of the transmission pulses 11-1 and 11-2 and the observation times of the reception beams 13-1 and 13-2.

  In the first embodiment, as shown in FIG. 4, the transmission antennas 3-1 and 3-2 are switched for each PRI and the transmission pulses 11-1 and 11-2 are transmitted. Furthermore, it is allowed to simultaneously observe the echoes 12-1 and 12-2 with respect to the transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2. At this time, the echo 12-1 for the transmission pulse 11-1 transmitted from the transmission antenna 3-1 and the echo 12-2 for the transmission pulse 11-2 transmitted from the transmission antenna 3-2 are shown in FIG. Come from different angles. Then, these echoes 12-1 and 12-2 are separated, the nadia echo is suppressed, and the reception beam 13-1 for receiving the echo 12-1 with respect to the transmission pulse 11-1 and the transmission are transmitted so as to improve the reception sensitivity. A reception beam 13-2 for receiving the echo 12-2 with respect to the pulse 11-2 is formed. As a result, the echoes 12-1 and 12-2 for the transmission pulses 11-1 and 11-2 transmitted from the different transmission antennas 3-1 and 3-2 can be separated, and the S / N can be improved while improving the S / N. A channel SAR can be realized.

  Next, the digital beam forming unit 504 converts the formed reception beams 13-1 and 13-2 into raw data 14-1 and 14-2 corresponding to the transmission antennas 3-1 and 3-2 and the radar of the multi-channel SAR system. It outputs to a signal processing apparatus (not shown) (step ST210). Thereafter, the raw signal 14-1 and 14-2 are reproduced by the radar signal processing device, and after registration using the obtained two SAR images, MTI is performed. For image reproduction, the range Doppler method, chirp scaling method, ω-k method, polar format method, etc. disclosed in Non-Patent Documents 5 and 6 may be used.

Next, the effect of the radar apparatus according to the first embodiment will be described.
In the radar apparatus according to the first embodiment, the configuration of the multi-channel SAR when performing DBF on the receiving side is not increased by increasing the number of receiving apparatuses 5 that perform DBF, but by increasing the number of transmitting apparatuses 2 having different transmission phase centers. Realized. As a result, the increase in the cost of the entire apparatus can be mitigated.

In the radar apparatus according to the first embodiment, the transmission antennas 3-1 and 3-2 are switched for each PRI to transmit the transmission pulses 11-1 and 11-2. Therefore, at the same time, the echo 12-1 for the transmission pulse 11-1 transmitted from the transmission antenna 3-1 and the echo 12-2 for the transmission pulse 11-2 transmitted from the transmission antenna 3-2 are from different angles. To come. Therefore, signal separation can be performed by DBF, and excellent quality can be achieved.
Further, since the PRIs are set at unequal intervals, the blind range can be distributed without being concentrated at a specific range distance. Therefore, it is possible to realize a wide observation width.

  In the configuration illustrated in FIG. 1, the case where two transmission apparatuses 2 are provided is illustrated, but three or more transmission apparatuses may be provided. At this time, the number of receiving devices 5 may be increased in the same manner to form a MIMO (Multiple-Input Multiple-Output) configuration. Furthermore, it may be a formation flight by a plurality of platforms.

  In the first embodiment, the transmission antennas 3-1 and 3-2 are switched for each PRI by sending PRIs at unequal intervals, and transmission pulses 11-1 and 11-2 are transmitted. The case where the echoes 12-1 and 12-2 for each of 3-1 and 3-2 are separated is shown. On the other hand, the frequency bands of the transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2 are separated, and observation is performed in the frequency domain on the reception side, thereby transmitting antennas 3-1 and 3-1. The echoes 12-1 and 12-2 may be separated every 3-2. Further, the transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2 are multiplied by a phase code, and transmission is performed by performing observation in the Doppler frequency region corresponding to the phase code on the reception side. The echoes 12-1 and 12-2 for each of the antennas 3-1 and 3-2 may be separated. In addition, the transmission time of the transmission pulses 11-1 and 11-2 and the observed time are separated in the time domain for each of the transmission antennas 3-1 and 3-2, and the transmission antennas 3-1 and 3-2 are separated on the reception side. Separation may be performed by receiving the echoes 12-1 and 12-2 at different times. Further, a different orthogonal code or a code according to the orthogonal code is assigned to each of the transmission antennas 3-1 and 3-2 to modulate the transmission pulses 11-1 and 11-2. The codes corresponding to 2 may be multiplied and the echoes 12-1 and 12-2 may be separated using the orthogonality. Any PRI may be used when using these methods. In the present embodiment, the same chirp pulse is used for each of the transmission antennas 3-1 and 3-2, but a method of separating on the receiving side using different chirp pulses such as an up-chirp pulse and a down-chirp pulse is used. May be. Further, signal separation may be performed by combining the above-described methods.

  Further, although the MTI is performed in the multi-channel SAR system according to Embodiment 1, HRWS may be performed. Further, InSAR may be performed by changing the antenna arrangement. Further, this embodiment may be used as part of polarimetry SAR.

  Furthermore, in the first embodiment, the transmission pulses 11-1 and 11-2 are not simultaneously transmitted from the transmission antennas 3-1 and 3-2 but are switched for each PRI and transmitted. Therefore, as shown in FIG. 5, the transmission modules up to the previous stage of the switch 204 can be shared by a transmission system of two transmissions. Thereby, the increase in the cost of the whole apparatus can further be eased.

  Further, as shown in FIG. 6, a reflector antenna 6 may be added on the receiving side. In this case, M receiving systems are arranged in the orbit direction. As a result, (2 × M) pieces of raw data corresponding to the two transmission antennas 3-1 and 3-2 are obtained. The obtained (2 × M) pieces of data are given in an orthogonal relationship for each of the transmission antennas 3-1 and 3-2 and become two raw data.

  As described above, according to the first embodiment, the plurality of transmission devices 2-1 and 2-2 having different phase centers of the output transmission pulses 11-1 and 11-2, and each transmission device 2-1. , 2-2, digital beam forming so that the phase centers of the reception beams 13-1 and 13-2 that receive the echoes 12-1 and 12-2 with respect to the transmission pulses 11-1 and 11-2 output by the transmission pulse 11-1 and 11-2 are single. In the radar apparatus constituting the multi-channel SAR that improves the S / N by digital beam forming, the increase in the cost of the entire apparatus can be mitigated.

Embodiment 2. FIG.
In the second embodiment, a radar apparatus of a multi-channel SAR system that includes two transmission apparatuses 2 and one reception apparatus 5 that performs DBF and performs InSAR will be described. FIG. 7 is a diagram showing the configuration of the radar apparatus of the multi-channel SAR system according to Embodiment 2 of the present invention.
The radar apparatus according to Embodiment 2 shown in FIG. 7 changes the antenna arrangement of the radar apparatus according to Embodiment 1 shown in FIG. 201-2 is changed to signal generation units 201b-1 and 201b-2, and the digital beam forming unit 504 of the receiving device 5 is changed to a digital beam forming unit 504b. Other configurations are the same, and the same reference numerals are given and description thereof is omitted. The basic processing procedure of the radar apparatus according to the second embodiment is the same as the processing procedure of the radar apparatus according to the first embodiment shown in FIG.

  The signal generation unit 201b-1 generates a chirp pulse. At this time, the signal generation unit 201b-1 generates chirp pulses so that the PRIs are equally spaced, and transmission pulses 11-1 and 11-2 are alternately transmitted from the transmission devices 2-1 and 2-2 for each PRI. To do. The signal generation unit 201b-2 is configured in the same manner as the signal generation unit 201b-1.

  The digital beam forming unit 504b forms the reception beam 13 by performing DBF on the signals digitized by the A / D converters 503-1 to 503-N. Here, the reception beam 13 is a reception beam obtained by alternately observing the echoes 12-1 and 12-2. The reception beam 13 formed by the digital beam forming unit 504b is used as raw data 14-1 and 14-2 corresponding to the transmission antennas 3-1 and 3-2 as a radar signal processing device (not shown) of the multichannel SAR system. To be processed.

  Next, the DBF process of the digital beam forming unit 504b in the second embodiment will be described with reference to FIGS. 8 shows the transmission pulse 11-1 transmitted from the transmission antenna 3-1, the echo 12-1 received by the reception antennas 4-1 to 4-N, and the digital beam forming unit of the reception device 5. It is a figure which shows the relationship with the receiving beam 13 formed by 504b. Actually, transmission of the transmission pulse 11-1 from the transmission antenna 3-1 and observation of the echo 12-1 by the reception beam 13 are not performed at the same time, but are shown together for convenience in this figure. FIG. 9 is a diagram showing the relationship between the transmission timings of the transmission pulses 11-1 and 11-2 and the observation time of the reception beam 13.

  In the second embodiment, as shown in FIG. 9, the transmission antennas 3-1 and 3-2 are switched for each PRI and the transmission pulses 11-1 and 11-2 are transmitted. Further, the echoes 12-1 and 12-2 with respect to the transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2 are not observed at the same time but are observed alternately. When the echo 12-1 (12-2) with respect to the transmission pulse 11-1 (11-2) transmitted from one transmission antenna 3-1 (3-2) is observed, another transmission antenna 3 As shown in FIG. 8, the irradiation range of the transmission pulse 11-1 (11-2) is set so that the transmission pulse 11-2 (11-1) transmitted from the terminal -2 (3-1) does not become range ambiguity. It is narrow. Thereby, the echoes 12-1 and 12-2 for the transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2 can be observed independently in time. Then, if the reception beam 13 for receiving the echoes 12-1 and 12-2 for the transmission pulses 11-1 and 11-2 is formed so as to suppress the nadia echo and improve the reception sensitivity, the S / N is improved. However, a multi-channel SAR can be realized.

  The reception beam 13 formed by the digital beam forming unit 504b is output to a radar signal processing device (not shown) as raw data 14-1 and 14-2 corresponding to the transmission antennas 3-1 and 3-2. . Thereafter, the raw data 14-1 and 14-2 are reproduced by the radar signal processing device, registration is performed, and height estimation is performed using the two obtained SAR images. For image reproduction, the range Doppler method, chirp scaling method, ω-k method, polar format method, etc. disclosed in Non-Patent Documents 5 and 6 may be used.

Next, the effect of the radar apparatus according to the second embodiment will be described.
In the radar apparatus according to the second embodiment, the configuration of the multi-channel SAR when performing DBF on the reception side is not increased by increasing the number of receiving apparatuses 5 that perform DBF, but by increasing the number of transmitting apparatuses 2 having different transmission phase centers. Realized. As a result, the increase in the cost of the entire apparatus can be mitigated.

  In the radar apparatus according to the second embodiment, the irradiation ranges of the transmission pulses 11-1 and 11-2 are narrowed, and transmission is performed by switching the transmission antennas 3-1 and 3-2 for each PRI. Therefore, the echo 12-1 corresponding to the transmission pulse 11-1 transmitted from the transmission antenna 3-1 and the echo 12-2 corresponding to the transmission pulse 11-2 transmitted from the transmission antenna 3-2 are observed independently in time. And excellent quality in signal separation can be achieved.

  In the configuration illustrated in FIG. 7, the case where two transmission apparatuses 2 are provided is illustrated, but three or more transmission apparatuses may be provided. At this time, the number of receiving apparatuses 5 may be increased by a smaller number than that of the transmitting apparatuses 2 to form a MIMO configuration. Furthermore, it may be a formation flight by a plurality of platforms.

  In the second embodiment, the transmission time of the transmission pulses 11-1 and 11-2 and the observed time are separated in the time domain for each of the transmission antennas 3-1 and 3-2, and the transmission antenna 3 on the reception side. The case where separation is performed by receiving the echoes 12-1 and 12-2 for each of -1 and 3-2 at different times is shown. On the other hand, the frequency bands of the transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2 are separated, and observation is performed in the frequency domain on the reception side, thereby transmitting antennas 3-1 and 3-1. The echoes 12-1 and 12-2 may be separated every 3-2. Further, the transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2 are multiplied by a phase code, and transmission is performed by performing observation in the Doppler frequency region corresponding to the phase code on the reception side. The echoes 12-1 and 12-2 for each of the antennas 3-1 and 3-2 may be separated. Further, a different orthogonal code or a code according to the orthogonal code is assigned to each of the transmission antennas 3-1 and 3-2 to modulate the transmission pulses 11-1 and 11-2. The codes corresponding to 2 may be multiplied and the echoes 12-1 and 12-2 may be separated using the orthogonality. Any PRI may be used when using these methods. Further, as in the first embodiment, the transmission times of the transmission pulses 11-1 and 11-2 are shifted, and the arrival directions of the echoes 12-1 and 12-2 of the transmission antennas 3-1 and 3-2 are different. For this reason, separation may be performed by DBF. Further, signal separation may be performed by combining the above-described methods.

  In the multi-channel SAR system according to the second embodiment, InSAR is performed. However, MTI and HRWS may be performed by changing the antenna arrangement. Further, this embodiment may be used as part of polarimetry SAR.

  Furthermore, in the second embodiment, transmission pulses 11-1 and 11-2 are not transmitted from the transmission antennas 3-1, 3-2 at the same time, but are switched for each PRI and transmitted. Therefore, as shown in FIG. 10, the transmission modules up to the previous stage of the switch 204 can be shared by a transmission system of two transmissions. Thereby, the increase in the cost of the whole apparatus can further be eased.

  Further, as shown in FIG. 11, a reflector antenna 6 may be added on the receiving side. At this time, M receiving systems are arranged in the orbital direction, and (2 × M) raw data corresponding to the two transmitting antennas 3-1 and 3-2 are obtained from the output of the DBF. The obtained (2 × M) pieces of data are given in an orthogonal relationship for each of the transmission antennas 3-1 and 3-2 and become two raw data.

  As described above, according to the second embodiment, even when the present invention is applied to a multi-channel SAR system that implements InSAR, the same effect as in the first embodiment can be obtained.

Embodiment 3 FIG.
In the third embodiment, a radar apparatus of a multi-channel SAR system that includes two transmission apparatuses 2 and one reception apparatus 5 that performs DBF and performs HRWS will be described. FIG. 12 is a diagram showing the configuration of the radar apparatus of the multi-channel SAR system according to Embodiment 3 of the present invention.
The radar apparatus according to the third embodiment shown in FIG. 12 generates the signal generators 201-1 and 201-2 of the transmission apparatuses 2-1 and 2-2 of the radar apparatus according to the first embodiment shown in FIG. The digital beam forming unit 504 of the receiving device 5 is changed to a digital beam forming unit 504c. Other configurations are the same, and the same reference numerals are given and description thereof is omitted. The basic processing procedure of the radar apparatus according to the third embodiment is the same as the processing procedure of the radar apparatus according to the first embodiment shown in FIG.

  The signal generator 201c-1 generates an up chirp pulse as a chirp pulse, and the signal generator 201c-2 generates a down chirp pulse as a chirp pulse. At this time, the signal generation units 201c-1 and 201c-2 set the PRIs at equal intervals, and send chirp pulses so as to simultaneously transmit the transmission pulses 11-1 and 11-2 from the transmission devices 2-1 and 202 for each PRI. Generate.

  The digital beam forming unit 504c forms the reception beam 13 by performing DBF on the signals digitized by the A / D converters 503-1 to 503-N. Here, the reception beam 13 is a reception beam obtained by observing the echoes 12-1 and 12-2 simultaneously. The reception beam 13 formed by the digital beam forming unit 504 is converted into raw data 14-1 and 14-2 corresponding to the transmission antennas 3-1 and 3-2 as a radar signal processing device (not shown) of the multichannel SAR system. To be processed.

  Next, the DBF process of the digital beam forming unit 504c in the third embodiment will be described with reference to FIGS. Here, FIG. 13 shows transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2 and echoes 12-1 and 12 received by the reception antennas 4-1 to 4-N. FIG. 2 is a diagram illustrating a relationship between −2 and the reception beam 13 formed by the digital beam forming unit 504c of the reception device 5. Actually, transmission of the transmission pulses 11-1 and 11-2 from the transmission antennas 3-1 and 3-2 and observation of the echoes 12-1 and 12-2 by the reception beam 13 are not performed at the same time. Then, it describes together for convenience. FIG. 14 is a diagram showing the relationship between the transmission timings of the transmission pulses 11-1 and 11-2 and the observation time of the reception beam 13.

  In the third embodiment, as shown in FIG. 14, transmission pulses 11-1 and 11-2 are simultaneously transmitted from the transmission antennas 3-1 and 3-2 for each PRI, and the transmission pulses 11-1 and 11- Echoes 12-1 and 12-2 for 2 are simultaneously observed. Then, if the reception beam 13 for receiving the echoes 12-1 and 12-1 with respect to the transmission pulses 11-1 and 11-2 is formed so as to suppress the nadia echo and improve the reception sensitivity, the S / N is improved. However, a multi-channel SAR can be realized.

  The reception beam 13 formed by the digital beam forming unit 504c is output to a radar signal processing device (not shown) as raw data 14-1 and 14-2 corresponding to the transmission antennas 3-1 and 3-2. . Thereafter, the radar signal processing device performs signal separation on the raw data 14-1 and 14-2 by pulse compression of up-chirp pulses and pulse compression of down-chirp pulses, and image reproduction is performed by DBF using a restoration algorithm. Done. For image reproduction, the range Doppler method, chirp scaling method, ω-k method, polar format method, etc. disclosed in Non-Patent Documents 5 and 6 may be used.

Next, the effect of the radar apparatus according to the third embodiment will be described.
In the radar apparatus according to the third embodiment, the configuration of the multi-channel SAR when performing DBF on the receiving side is not increased by increasing the number of receiving apparatuses 5 that perform DBF, but by increasing the number of transmitting apparatuses 2 having different transmission phase centers. Realized. As a result, the increase in the cost of the entire apparatus can be mitigated.

  In the radar apparatus according to the third embodiment, a different orthogonal code or a code (up-chirp pulse, down-chirp pulse) following the orthogonal code is assigned to each of the transmission antennas 3-1 and 3-2, and the transmission pulse 11- 1 and 11-2 are transmitted. Therefore, by performing pulse compression corresponding to each code on the output after DBF, signal separation can be performed and excellent quality can be achieved.

  In the configuration illustrated in FIG. 12, the case where two transmission apparatuses 2 are provided is illustrated, but three or more transmission apparatuses may be provided. At this time, the number of receiving apparatuses 5 may be increased by a smaller number than that of the transmitting apparatuses 2 to form a MIMO configuration. Furthermore, it may be a formation flight by a plurality of platforms.

  In the third embodiment, an orthogonal code or a code that follows the orthogonal code is assigned to each of the transmission antennas 3-1 and 3-2 to modulate the transmission pulses 11-1 and 11-2, and the transmission antenna is received on the reception side. The case where the codes corresponding to 3-1 and 3-2 are multiplied and the echoes 12-1 and 12-2 are separated using the orthogonality is shown. On the other hand, the transmission time of the transmission pulses 11-1 and 11-2 and the observed time are separated in the time domain for each of the transmission antennas 3-1 and 3-2. Separation may be performed by receiving the echoes 12-1 and 12-2 every 3-2 at different times. By making the frequency bands of the transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2 separately and performing observation in the frequency domain on the reception side, the transmission antennas 3-1 and 3-2 are performed. The echoes 12-1 and 12-2 may be separated every time. Further, the transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2 are multiplied by a phase code, and transmission is performed by performing observation in the Doppler frequency region corresponding to the phase code on the reception side. The echoes 12-1 and 12-2 for each of the antennas 3-1 and 3-2 may be separated. Any PRI may be used when using these methods. Further, as in the first embodiment, the transmission times of the transmission pulses 11-1 and 11-2 are shifted, and the arrival directions of the echoes 12-1 and 12-2 of the transmission antennas 3-1 and 3-2 are different. For this reason, separation may be performed by DBF. Further, signal separation may be performed by combining the above-described methods.

  In the multi-channel SAR system according to the third embodiment, HRWS is implemented, but MTI may be performed. Further, InSAR may be performed by changing the antenna arrangement. Further, this embodiment may be used as part of polarimetry SAR.

  As described above, according to the third embodiment, even if the present invention is applied to a multi-channel SAR system that implements HRWS, the same effect as in the first embodiment can be obtained.

Embodiment 4 FIG.
In the fourth embodiment, a radar apparatus of a multi-channel SAR system that includes two transmission apparatuses 2 and two reception apparatuses 5 that perform DBF and performs MTI will be described. FIG. 15 is a diagram showing a configuration of a radar apparatus of a multi-channel SAR system according to Embodiment 4 of the present invention.
The radar apparatus according to Embodiment 4 shown in FIG. 14 is obtained by changing the receiving apparatus 5 of the radar apparatus according to Embodiment 1 shown in FIG. 1 into two receiving apparatuses 5-1 and 5-2. In addition, each receiving apparatus 5-1 and 5-2 sets DBF so that the phase centers of the receiving beams 13-1-1 and 13-2-1 and the receiving beams 13-1-2 and 13-2-2 are different from each other. Assumed to be performed. Other configurations are the same, and the same reference numerals are given and description thereof is omitted. The basic processing procedure of the radar apparatus according to the fourth embodiment is the same as the processing procedure of the radar apparatus according to the first embodiment shown in FIG.

  The DBF processing of the digital beam forming units 504-1 and 504-2 in the fourth embodiment will be described with reference to FIGS. Here, FIG. 16 shows transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2 and reception antennas 4-1-1 to 4-N-1, 4-1-2. ~ Echoes 12-1 and 12-2 received by 4-N-2 and received beams 13-1 formed by the digital beam forming units 504-1 and 504-2 of the receiving devices 5-1 and 5-2. It is a figure which shows the relationship with -1,13-1-2,13-2-1 and 13-2-2. Actually, transmission pulses 11-1 and 11-2 from the transmission antennas 3-1 and 3-2 and reception beams 13-1-1, 13-1-2, 13-2-1 and 13-2 are transmitted. The echoes 12-1 and 12-2 by -2 are not observed at the same time, but are shown together for convenience in this figure. FIG. 17 shows the relationship between the transmission timings of the transmission pulses 11-1 and 11-2 and the observation times of the reception beams 13-1-1, 13-1-2, 13-2-1 and 13-2-2. FIG.

  In the fourth embodiment, as shown in FIG. 17, the transmission antennas 3-1 and 3-2 are switched for each PRI and the transmission pulses 11-1 and 11-2 are transmitted. Furthermore, it is allowed to simultaneously observe the echoes 12-1 and 12-2 with respect to the transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2. At this time, the echo 12-1 for the transmission pulse 11-1 transmitted from the transmission antenna 3-1 and the echo 12-2 for the transmission pulse 11-2 transmitted from the transmission antenna 3-2 at the same time are shown in FIG. Come from different angles. Then, these echoes 12-1 and 12-2 are separated, the Nadia echo is suppressed, and the reception beam 13-1-1 for receiving the echo 12-1 for the transmission pulse 11-1 is improved. 13-1-2 and echoes 12-2 for the transmission pulse 11-2 are received. As a result, the echoes 12-1 and 12-2 for the transmission pulses 11-1 and 11-2 transmitted from the different transmission antennas 3-1 and 3-2 can be separated, and the S / N can be improved while improving the S / N. A channel SAR can be realized.

  The reception beams 13-1-1, 13-1-2, 13-2-1, and 13-2-2 formed by the digital beam forming units 504-1 and 504-2 are transmitted from the transmission antenna 3-1. Raw data 14-1-1, 14-1-2, 14-2-1 and 14-2-2 corresponding to 3-2 are output to a radar signal processing device (not shown) of the multi-channel SAR system. Thereafter, the raw signal 14-1-1, 14-1-2, 14-2-1 and 14-2-2 are reproduced by the radar signal processing device, and the four SAR images obtained are used to perform MTI. Is done. For image reproduction, the range Doppler method, chirp scaling method, ω-k method, polar format method, etc. disclosed in Non-Patent Documents 5 and 6 may be used.

Next, effects of the radar apparatus according to Embodiment 4 will be described.
In the radar apparatus according to the fourth embodiment, the transmission antennas 3-1 and 3-2 are switched for each PRI to transmit the transmission pulses 11-1 and 11-2. Therefore, at the same time, the echo 12-1 for the transmission pulse 11-1 transmitted from the transmission antenna 3-1 and the echo 12-2 for the transmission pulse 11-2 transmitted from the transmission antenna 3-2 are from different angles. To come. Therefore, signal separation can be performed by DBF, and excellent quality can be achieved.
Further, since the PRIs are set at unequal intervals, the blind range can be distributed without being concentrated at a specific range distance. Therefore, it is possible to realize a wide observation width.
As described above, the feature of the fourth embodiment is that the echo separation method shown in the first embodiment can also be realized in MIMO.

  In the configuration illustrated in FIG. 15, the case where two transmission apparatuses 2 are provided is illustrated, but three or more transmission apparatuses may be provided. At this time, the number of receiving devices 5 may be increased in the same manner to form a MIMO configuration.

  In the fourth embodiment, the transmission antennas 3-1 and 3-2 are switched for each PRI with the PRIs being unequal, and the transmission pulses 11-1 and 11-2 are transmitted. The case where the echoes 12-1 and 12-2 for each of 3-1 and 3-2 are separated is shown. On the other hand, the frequency bands of the transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2 are separated, and observation is performed in the frequency domain on the reception side, thereby transmitting antennas 3-1 and 3-1. The echoes 12-1 and 12-2 may be separated every 3-2. Further, the transmission pulses 11-1 and 11-2 transmitted from the transmission antennas 3-1 and 3-2 are multiplied by a phase code, and transmission is performed by performing observation in the Doppler frequency region corresponding to the phase code on the reception side. The echoes 12-1 and 12-2 for each of the antennas 3-1 and 3-2 may be separated. In addition, the transmission time of the transmission pulses 11-1 and 11-2 and the observed time are separated in the time domain for each of the transmission antennas 3-1 and 3-2, and the transmission antennas 3-1 and 3-2 are separated on the reception side. Separation may be performed by receiving the echoes 12-1 and 12-2 at different times. Further, a different orthogonal code or a code according to the orthogonal code is assigned to each of the transmission antennas 3-1 and 3-2 to modulate the transmission pulses 11-1 and 11-2. The codes corresponding to 2 may be multiplied and the echoes 12-1 and 12-2 may be separated using the orthogonality. Any PRI may be used when using these methods. In the fourth embodiment, the same chirp pulse is used for each of the transmission antennas 3-1 and 3-2, but a method of separating on the receiving side using different chirp pulses such as an up chirp pulse and a down chirp pulse is used. May be. Further, signal separation may be performed by combining the above-described methods.

  In addition, although MTI is performed in the multi-channel SAR system according to Embodiment 4, HRWS may be performed. Further, InSAR may be performed by changing the antenna arrangement. Further, this embodiment may be used as part of polarimetry SAR.

  In the fourth embodiment, the MIMO configuration is realized by a single platform. However, the MIMO configuration may be realized by formation flight by a plurality of platforms.

  As described above, according to the fourth embodiment, even if the present invention is applied to a multi-channel SAR system that implements MTI in a MIMO configuration, excellent quality in echo separation can be achieved. it can.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  1 local oscillator, 2 transmitting device, 3 transmitting antenna, 4 receiving antenna, 5 receiving device, 6 reflector antenna, 11 transmitting pulse, 12 echo, 13 receiving beam, 14 raw data, 201, 201b, 201c signal generating unit, 202 multiplication , 203 amplifier, 204 switcher, 501 amplifier, 502 multiplier, 503 A / D converter, 504, 504b, 504c digital beam forming unit.

Claims (9)

A radar apparatus constituting a multi-channel SAR that improves S / N by digital beam forming,
A plurality of transmission devices that output transmission pulses that have been up-converted using local oscillation signals from the same local oscillator, and that have different phase centers of output transmission pulses,
The digital beam is down-converted with respect to the received signal using a local oscillation signal from the local oscillator, and the phase center of the received beam for receiving the echo for the transmission pulse output by each transmitting device is single. A radar apparatus comprising: a single receiving apparatus that performs formation. A radar apparatus constituting a multi-channel SAR that improves S / N by digital beam forming,
A plurality of transmission devices that output transmission pulses that have been up-converted using local oscillation signals from the same local oscillator, and that have different phase centers of output transmission pulses,
A receiving beam is provided that is smaller in number than the transmitter, down-converts the received signal using the local oscillation signal from the local oscillator, and receives echoes for the transmission pulses output by the transmitters. A radar apparatus comprising: a plurality of receiving apparatuses that perform the digital beam forming so as to be single. Each of the transmission devices sets the pulse repetition interval as unequal intervals, and sequentially outputs the transmission pulse for each pulse repetition interval,
The radar apparatus according to claim 1, wherein the reception apparatus separates echoes for transmission pulses output by the transmission apparatuses by the digital beam forming. Each of the transmission devices assigns a different orthogonal code or a code following the orthogonal code to the transmission pulse,
4. The receiver according to claim 1, wherein the receiver separates echoes for the transmission pulses output by the transmitters using orthogonality of the assigned waveform. 5. The radar apparatus according to item 1. Each of the transmission devices outputs the transmission pulse at different times,
The radar apparatus according to claim 1, wherein the receiving apparatus separates the echoes by receiving the echoes for the transmission pulses output by the transmitting apparatuses at different times. Each of the transmission devices outputs the transmission pulse in different frequency bands,
The radar apparatus according to claim 1, wherein the reception apparatus separates echoes for transmission pulses output from the transmission apparatuses by performing observations in the frequency bands. Each of the transmission devices multiplies the transmission pulse by a different phase code,
The said receiving apparatus isolate | separates the echo with respect to the transmission pulse output by each said transmission apparatus by observing in the Doppler frequency band corresponding to each said phase code. Radar equipment. A radar apparatus constituting a multi-channel SAR that improves S / N by digital beam forming,
A plurality of transmission devices that output transmission pulses that have been up-converted using local oscillation signals from the same local oscillator, and that have different phase centers of output transmission pulses,
The digital beam forming is performed by down-converting the received signal by using the local oscillation signal from the local oscillator, and the phase centers of the received beams for receiving the echoes for the transmission pulses output by the respective transmission devices are different from each other. A plurality of receiving devices to perform,
Each of the transmission devices sets the pulse repetition interval as unequal intervals, and sequentially outputs the transmission pulse for each pulse repetition interval,
The radar apparatus according to claim 1, wherein the receiver separates echoes for the transmission pulses output by the transmitters by the digital beam forming. Each of the transmission devices assigns a different orthogonal code or a code following the orthogonal code to the transmission pulse,
The radar apparatus according to claim 8, wherein the reception apparatus separates echoes for transmission pulses output from the transmission apparatuses by using orthogonality of the assigned waveform.

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