JP2010048603A - Synthetic aperture radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a synthetic aperture radar device capable of simplifying a receiving system with multi channels and suppressing the rate and amount of generated data. <P>SOLUTION: The synthetic aperture radar device incldues: a plurality of antennas; a phase shifter for performing a different interpulse phase modulation on each received signal from each of the antennas; a synthesis circuit for synthesizing each received signal subjected to the interpulse phase modulation by the phase shifter; a plurality of demodulators for performing demodulation processing by multiplying the received signal synthesized by the synthesize circuit by a reverse phase data of each interpulse phase modulation series; and a plurality of imaging processing devices each performing different imaging processing on each signal demodulated by the demodulators. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a Synthetic Aperture Radar (SAR) apparatus that performs observation of a multi-channel system such as MTI (Moving Target Indicator) observation, multi-polarization observation, multi-beam observation, etc., and obtains an observation image.

  As an observation method using a synthetic aperture radar (SAR), there are MTI observation, along track interferometry observation, multi-polarization observation, multi-beam observation, and the like (for example, refer to Patent Documents 1 and 2).

JP-A-10-148673

JP 2006-349477 A

  Conventional synthetic aperture radar requires one receiving system for one channel signal, and when multiple observation methods are performed simultaneously with multiple channels (multiple channels), each observation method is dedicated to each observation method. It had a receiving system.

  In addition, in multi-polarization observation using horizontal polarization and vertical polarization, there are two reception systems in order to receive both polarizations simultaneously. At this time, only one of the horizontally polarized waves and the vertically polarized waves is transmitted by alternately switching in time division.

In the conventional synthetic aperture radar, since one reception system is required for one channel signal, resources (mass and power consumption) corresponding to the number of reception channels increase in a multi-channel system.
In addition, since the received signal is converted into data after being digitally converted, the generated data rate and the amount of data are increased by the number of reception channels, and the load on the signal processing, recording system, and transmission system is high.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a synthetic aperture radar apparatus that can simplify a receiving system having multi-channels and can suppress a generated data rate and a data amount. .

  The synthetic aperture radar apparatus according to the present invention includes a plurality of antennas, a phase shifter that performs different inter-pulse phase modulation for each received signal of each of the antennas, and each reception that has been subjected to inter-pulse phase modulation by the phase shifter. A synthesizing circuit for synthesizing signals, a plurality of demodulators for demodulating the received signal synthesized by the synthesizing circuit by multiplying the anti-phase data for each of the inter-pulse phase modulation sequences, and the demodulator And a plurality of imaging processing apparatuses that perform different imaging processes on the demodulated signal.

  Further, a plurality of antennas, a phase shifter that performs different pulse phase modulation for each of the antennas on the transmission type signal, and outputs a modulated signal to each of the antennas, and a received signal received by the antennas between the pulses A plurality of demodulators that perform demodulation processing by multiplying the antiphase data for each phase modulation sequence, and a plurality of imaging processing devices that perform different imaging processes on the signals demodulated by the demodulator. May be.

  According to the present invention, the number of receiving systems and hardware can be reduced by combining a plurality of channels with a combining circuit. Further, the generated data rate and the data amount are reduced due to the decrease in the number of reception systems.

  In addition, by performing inter-pulse phase modulation for each transmission channel, it is possible to simultaneously transmit different types of signals such as horizontal, vertical and vertical polarization. It is possible to improve the observation performance of the synthetic aperture radar by expanding.

Embodiment 1 FIG.
FIG. 1 is a diagram showing the configuration of a synthetic aperture radar apparatus according to Embodiment 1 of the present invention. In the figure, a synthetic aperture radar apparatus includes a plurality of antennas 1 (1-A, 1-B,..., 1-N) and a plurality of phase shifters 2 (2-A, 2-B,... , 2-N), excitation / transmission system 4, reception system 8, synthesis circuit 9, synthesis reception data recording apparatus 20, and a plurality of demodulation processors 21 (21-A, 21-B,... 21-N) and a plurality of SAR imaging processors 22 (22-A, 22-B,..., 22-N).

  The antenna 1 is made up of a plurality of channels (Ach to Nch) of N antennas 1-A, 1-B,..., 1-N (N is a natural number of 2 or more), and radiates radio waves from each antenna to the space. At the same time, it receives the radio waves reflected back from the target. The excitation / transmission system 4 generates an RF signal as a transmission seed signal, amplifies the generated RF signal to a desired transmission power level, and then supplies an RF signal for transmission to each antenna 1-A to 1-N. To do.

  The antennas 1-A to 1-N receive the received signals of Ach to Nch, respectively, and then receive the received signals for each phase shifter 2 (2-A, 2-B, ..., 2-N). Send to. Each phase shifter 2 performs phase setting based on each 0 / π inter-pulse phase modulation sequence having no cross-correlation, and performs phase modulation on each of the received signals of the antennas 1-A to 1-N. The combining circuit 9 combines the reception signals of the antennas 1-A to 1-N. The reception system 8 performs low-noise amplification and demodulation processing on the reception signal synthesized by the synthesis circuit 9, reproduces the reception signal, and converts the reproduced reception signal into a digital signal. The combined received data recording device 20 records the digitized combined received data reproduced by the receiving system 8 and transmits the recorded data to the demodulation processors 21-A to 21-N. Each demodulator 21-A to 21-N has the reverse phase data for each 0 / π inter-pulse phase modulation sequence (sequence RA to RN) set to the reception signal of each Ach to Nch with respect to the combined reception data. Are multiplied to demodulate and receive signals of Ach to Nch are obtained. Each SAR imaging processor 22 (22-A, 22-B,..., 22-N) is based on the received signals of each Ach to Nch demodulated by each demodulation processor 21-A to 21-N. Thus, SAR image data for each of Ach to Nch is obtained by performing different SAR imaging processing on the data of each channel. Here, as the predetermined SAR imaging processing that differs for each of Ach to Nch, there are MTI observation, along track interferometry observation, multi-polarization observation, multi-beam observation, and the like, and imaging processing is performed for each channel. .

Next, the operation will be described.
The RF signal generated and amplified by the excitation / transmission system 4 is distributed to N channels, fed to the antennas 1-A to 1-N, and radiated from the antennas 1-A to 1-N into space. The The reception signal reflected by the target is received by antenna 1-A to antenna 1-N. Since the signals received by the antennas 1-A to 1-N have different information, each SAR imaging processor 22 in the subsequent stage performs independent processing.

  Here, for the Ach to Nch signals received by the antennas 1-A to 1-N, modulation sequences (M sequence, Barker code, PN code, etc.) having no correlation are prepared in advance for the number of reception channels. Each of the phase shifters 2-A, 2-B,..., 2-N performs phase setting on the received signals of Ach to Nch based on the modulation sequence prepared for each pulse. Perform phase modulation between π pulses. The Ach to Nch signals subjected to this modulation are synthesized by the synthesis circuit 9. As a result, the number of channels of the receiving system can be reduced (the number of receiving systems <the number of receiving channels). For example, as shown in FIG. 1, by combining the received signals of all channels Ach to Nch by the combining circuit 9, the combined received signal is output to one receiving system 8. The output signal of the reception system 8 is sequentially stored in the combined reception data recording device 20 as combined reception data, and the stored combined reception data is sequentially distributed to the demodulation processors 21-1 to 21-N.

  Each of the demodulating processors 21-A, 21-B,..., 21-N is a 0 / π pulse interval set in advance to the received signals of Ach to Nch by each phase shifter 2 with respect to the combined received data. By demodulating the data in phase opposite to each of the phase modulation sequences (sequences RA to RN), demodulation processing is performed to obtain reception signals of Ach to Nch. The SAR imaging processor 22-A, 22-B,..., 22-N converts the data of each channel demodulated by each demodulator 21-A, 21-B,. By performing different predetermined SAR imaging processes, SAR image data for each of Ach to Nch is obtained. Here, the signal suppressed by the modulation remains in the image as noise, but it can be sufficiently used as long as it is within the allowable value as the inter-channel isolation.

  For example, when performing MTI observation processing using two reception antennas in each of the SAR imaging processors 22-A to 22-N, the antenna 1-A and the antenna 1-B are assigned to the respective reception apertures. In addition, in each SAR imaging processor 22, when performing multi-polarization observation processing for simultaneously receiving horizontal polarization and vertical polarization, Ach or Bch is assigned to either horizontal or vertical polarization. In each of the SAR imaging processors 22-A to 22-N, when performing multi-beam observation processing with N reception antennas, the antennas 1-A to 1-N are assigned to the respective reception apertures. In addition, in each SAR imaging processor 22-A to 22-N, when performing each imaging process by MTI observation processing, along track interferometry observation, multi-polarization observation, and multi-beam observation, A phase modulation sequence between 0 / π pulses corresponding to the number of observation processes may be set so that signals are separated for each channel according to the observation process.

  As described above, in the synthetic aperture radar apparatus according to the first embodiment, the number of reception systems and hardware can be reduced by synthesizing a plurality of channels by the synthesis circuit 9. Further, the generated data rate and the data amount are reduced due to the decrease in the number of reception systems.

Embodiment 2. FIG.
FIG. 2 is a diagram showing the configuration of the synthetic aperture radar apparatus according to the second embodiment. This synthetic aperture radar apparatus includes a plurality of antennas 1 (1-A, 1-B,..., 1-N) and a plurality of phase shifters 13 (13-A, 13-B,..., 13 -N), excitation / transmission system 4, a plurality of reception systems 5 (5-A, 5-B,..., 5-N), and a plurality of reception data recording devices 30 (30-A, 30-). B, ..., 30-N), a plurality of demodulation processors 31 (31-A, 31-B, ..., 31-N), and a plurality of SAR imaging processors 32 (32-A, 32-B,..., 32-N).

  The antenna 1 is made up of a plurality of channels (Ach to Nch) of N antennas 1-A, 1-B,..., 1-N (N is a natural number of 2 or more), and radiates radio waves from each antenna to the space. At the same time, it receives the radio waves reflected back from the target. The excitation / transmission system 4 generates an RF signal as a transmission seed signal, amplifies the generated RF signal to a desired transmission power level, and then transmits the RF signal for transmission to each of the phase shifters 13-A to 13-N. Supply. Each of the phase shifters 13-A to 13-N performs phase setting based on each 0 / π inter-pulse phase modulation sequence having no cross-correlation, and performs phase modulation on the RF signal from the excitation / transmission system 4 The RF signals for transmission modulated in phase are supplied to the antennas 1-A to 1-N.

  Antennas 1-A to 1-N receive the received signals of Ach to Nch, respectively. Receiving systems 5-A to 5-N perform low-noise amplification and demodulation processing on the received signals Ach to Nch received by antenna 1-A to antenna 1-N, reproduce the received signal, and regenerate the received signal. Each signal is converted into a digital signal. The reception data recording device 30 sequentially records the digitized reception data reproduced by the reception systems 5-1 to 5-N and sequentially transmits the recorded data to the demodulation processors 31-A to 31-N. To do. Each demodulator 31-A to 31-N outputs, with respect to the received data, data in reverse phase for each phase modulation sequence (sequence TA to TN) between 0 / π pulses set in the transmission signal for each of Ach to Nch. Multiplication is performed to perform demodulation processing. The SAR imaging processor 32 performs different SAR imaging processing on the data of each channel based on the received signals of Ach to Nch demodulated by the demodulation processors 31-A to 31-N, respectively. Image data for Ach to Nch is obtained.

  For example, in multi-polarization observation in which horizontal polarization and vertical polarization are simultaneously received, Ach and Bch of the reception system are assigned to either horizontal polarization or vertical polarization. Conventionally, in multi-polarization observation using horizontal polarization and vertical polarization in a transmission system, only one of horizontal polarization and vertical polarization is switched alternately in time division and transmitted. However, by using the synthetic aperture radar device of this second embodiment, it becomes possible to transmit both horizontal and vertical polarizations simultaneously. In addition to simplification of the transmission system, the observation aperture can be expanded, etc. The observation performance can also be improved.

Next, the operation will be described.
The RF signal generated and amplified by the excitation / transmission system 4 is branched into signals of Ach to Nch. Uncorrelated modulation sequences (M sequence, Barker code, PN code, etc.) are prepared for the number of channels for Ach to Nch transmission signals. A modulation sequence for N channels is set for each pulse of the transmission signals of Ach to Nch by a transmission system 0 / π inter-pulse phase modulation setting phase shifter, and phase modulation is performed. The modulated transmission signal is radiated from antenna 1-A to antenna 1-N into space. The reception signal reflected by the target is received by the antennas 1-A to 1-N and reproduced by the reception systems 5-A to 5-N to output digitized reception data.

  In each of the demodulator 31-A to 31-N, each of the Ach to 31A reproduced by each reception system 5-A to 5-N and temporarily stored in each reception data recording device 30-A to 30-N. The Nch reception data is multiplied by the reverse phase data for each 0 / π inter-pulse phase modulation sequence (sequence RA to RN) set in the transmission signal, thereby performing demodulation processing. Thereby, each demodulator 31-A to 31-N obtains a reception signal having information of each Ach to Nch transmission signal. The SAR imaging processors 32-A to 32-N perform SAR imaging processing on the data of each channel demodulated by the demodulation processors 31-A to 31-N, thereby converting the image data of Ach to Nch. obtain.

  Note that the signal suppressed by the modulation remains in the image as noise, but it can be sufficiently used if it is within an allowable value for channel-to-channel isolation.

Embodiment 3 FIG.
The synthetic aperture radar device according to the third embodiment of the present invention is a combination of the configurations of the first and second embodiments. FIG. 3 is a diagram showing a configuration of the synthetic aperture radar apparatus according to the third embodiment.

  In the figure, a synthetic aperture radar apparatus includes a plurality of antennas 1-A, 1-B,... 1-N, a plurality of phase shifters 2-A to 2-N of a reception system, and an excitation / transmission system 4. A receiving system 8, a combining circuit 9, a plurality of transmission phase shifters 13-A to 13-N, a combined received data recording device 20, and a plurality of demodulation processors 21-A to 21-N. And a plurality of SAR imaging processors 22-A to 22-N. In the figure, components having the same reference numerals as those in FIGS.

Next, the operation will be described.
The RF signal generated and amplified in the excitation / transmission system 4 branches to signals of Ach to Nch. For the transmission signals of Ach to Nch, modulation sequences (M sequence, Barker code, PN code, etc.) having no correlation are prepared in advance for the number of channels. A modulation sequence for N channels is set for each pulse of the Ach to Nch transmission signals by the phase shifter 2, and phase modulation is performed. The transmission signals modulated by the phase shifters 2-A to 2-N are radiated to the space from the antennas 1-A to 1-N. The reception signal reflected by the target is received by the antennas 1-A to 1-N.

  Here, since the signals received by the antennas 1-A to 1-N have different information, they are independently processed by the SAR imaging processors 22 in the subsequent stage. Uncorrelated modulation sequences (M sequence, Barker code, PN code, etc.) for the number of channels are prepared for the signals of Ach to Nch received by antenna 1-A to antenna 1-N. It is assumed that the modulation sequence here has no correlation with the modulation sequence at the time of transmission. A modulation sequence for N channels is set for each pulse of the received signals of Ach to Nch by a receiving system 0 / π inter-pulse phase modulation setting phase shifter, and phase modulation is performed. The modulated Ach to Nch signals are combined by the combining circuit 9 to reduce the number of channels (the number of reception systems <the number of reception channels). In FIG. 3, the reception signals of all channels are combined by the combining circuit 9 and output to the combined reception data recording device 20 in one system. The synthesized reception data recording device 20 sequentially accumulates the output signals of the reception system 8 and distributes the accumulated synthesized reception data to the respective demodulation processors 21-A to 21-N sequentially.

  Here, by combining a plurality of channels by the combining circuit 9, the number of receiving systems and hardware can be reduced. Further, the generated data rate and the data amount are reduced due to the decrease in the number of reception systems.

  In addition to the functions of the first embodiment, each of the demodulator 21-A to 21-N performs synthesis on the received data synthesized by the synthesis circuit 9 and distributed from the synthesized received data recording device 20. Demodulation is performed by multiplying the reverse phase data of each 0 / π inter-pulse phase modulation sequence (sequence RA to RN) set in the transmission and reception signals of Ach to Nch. As a result, the demodulation processors 21-A to 21-N obtain Ach to Nch reception signals having information on the transmission signals of the Ach to Nch. Each SAR imaging processor 22-A to 22-N performs different predetermined SAR imaging processing on the data of each channel demodulated by each demodulation processor 21-A to 21-N, respectively. SAR image data for each of Ach to Nch is obtained.

  In this embodiment, in multi-polarization observation in which horizontal polarization and vertical polarization are received simultaneously, Ach and Bch of the reception system are assigned to either horizontal polarization or vertical polarization. Conventionally, in multi-polarization observation using horizontal polarization and vertical polarization in a transmission system, only one of horizontal polarization and vertical polarization is switched alternately in time division. However, by using this embodiment, simultaneous transmission of horizontal and vertical and vertical polarization is possible, and in addition to simplification of the transmission system, the observation performance of the synthetic aperture radar can be improved, such as expansion of the observation width. It becomes. It is also possible to combine multi-polarization observation by the transmission system with MTI observation and multi-beam observation by the reception system.

  Note that the signal suppressed by the modulation remains in the image as noise, but it can be sufficiently used if it is within an allowable value for channel-to-channel isolation.

It is a figure which shows the structure of the synthetic aperture radar apparatus by Embodiment 1 which concerns on this invention. It is a figure which shows the structure of the synthetic aperture radar apparatus of Embodiment 2. FIG. It is the figure which showed the structure of the synthetic aperture radar apparatus by Embodiment 3 which concerns on this invention.

Explanation of symbols

  1 (1-A, 1-B,..., 1-N) antenna, 2 phase shifter, 4 excitation / transmission system, 5 reception system, 8 reception system, 9 synthesis circuit, 13 phase shifter, 20 synthesis Received data recording device, 21 demodulation processor, 22 SAR imaging processor.

Claims (2)

Multiple antennas,
A phase shifter for performing different inter-pulse phase modulation for each received signal of each antenna;
A synthesizing circuit that synthesizes each received signal subjected to inter-pulse phase modulation by the phase shifter;
A plurality of demodulators that perform demodulation processing by multiplying the reception signal synthesized by the synthesis circuit by the anti-phase data for each of the inter-pulse phase modulation series,
A plurality of imaging processing devices that perform different imaging processes on the signals demodulated by the demodulator;
Synthetic aperture radar apparatus comprising: Multiple antennas,
A first phase shifter that performs a first-sequence inter-pulse phase modulation different for each of the antennas on a transmission type signal, and outputs a modulated signal to each of the antennas;
A second phase shifter for performing different inter-pulse phase modulation for each received signal of each antenna;
A synthesizing circuit that synthesizes each received signal that has undergone inter-pulse phase modulation by the first phase shifter;
A plurality of demodulators that perform demodulation processing by multiplying the reception signal synthesized by the synthesis circuit by the anti-phase data for each of the first-sequence and second-sequence inter-pulse phase modulation sequences;
A plurality of demodulators that perform demodulation processing by multiplying the reception signal received by the antenna by the anti-phase data for each of the inter-pulse phase modulation sequences;
A plurality of imaging processing devices that perform different imaging processes on the signals demodulated by the demodulator;
Synthetic aperture radar apparatus comprising:

Images