Radar system with synthetic aperture
Synthetic aperture radar (SAR) system and method of processing signals in a SAR system. The SAR system includes includes a radar antenna having at least one partial antenna, of which each at least one partial antenna includes a plurality of phase centers with assigned transmit/receive modules and a signal processor for coherent processing of signals of the phase centers. The signal processors include a hybrid beam forming module structured and arranged to digitize and process analog receive signals received by the transmit/receive modules of the phase centers, and to convert the digitally processed receive signals into analog signals. Further, an analog receive network is structured and arranged to combine the analog signals of respective transmit/receive modules with one another to form an output signal.
1. A synthetic aperture radar (SAR) system comprising:
a radar antenna having at least one partial antenna, of which each at least one partial antenna comprises a plurality of phase centers with assigned transmit/receive modules and a signal processor for coherent processing of signals of the phase centers;
each of the signal processors comprising a hybrid beam forming module configured to digitize and process analog receive signals received by the transmit/receive modules of the phase centers, and to convert the digitally processed receive signals into analog signals, and
an analog receive network configured to combine the analog signals of respective transmit/receive modules with one another to form an output signal.
2. The SAR system according to claim 1 , wherein the hybrid beam forming module is further configured to feed the processed analog receive signals to the analog receive network.
3. The SAR system according to claim 1 , wherein the hybrid beam forming module is further configured to process the digitized receive signals for digital beam formation and to synchronize digitized receive signals with one another.
4. The SAR system according to claim 3 , wherein the hybrid beam forming module is further configured to correct the digitized receive signals.
5. The SAR system according to claim 1 , wherein the hybrid beam forming module comprises a digital-to-analog converter to convert the digitally processed receive signals into respective analog signals.
6. The SAR system according to claim 5 , wherein the analog receive network is connected immediately downstream of the digital-to-analog converter.
7. The SAR system according to claim 1 , wherein the combining of the analog signals by the analog receive network comprises a summation of the analog signals, whereby the formed output signal is a sum signal.
8. The SAR system according to claim 1 , wherein the signal processors are configured to calibrate the analog signals with a digital calibration signal directly generated at inputs of the analog receive network.
9. The SAR system according to claim 1 , further comprising:
a central processing unit having an analog-to-digital converter; and
an output signal processor configured to process the output signal generated by the analog receive network and to feed the processed output signal to the analog-to-digital converter of the central processing unit.
10. The SAR system according to claim 9 , wherein the signal conversion by at least one of the digital-to-analog converter and the analog-to-digital converter is carried out near to or in the baseband.
11. The SAR system according to claim 1 , wherein the signal processors are configured to combine the signals of several transmit/receive modules to form a signal channel before the analog conversion by the digital-to-analog converter.
12. The SAR system according to claim 1 , wherein the signal processors further comprise a feedback channel having an upward mixer, an amplifier and a filter to generate a digital chirp signal, which is fed on a carrier frequency and as an input signal to the transmit/receive modules.
13. The SAR system according to claim 1 , wherein the plurality of phase centers is included in a plurality of radiators.
14. A method for processing SAR signals with a radar antenna having at least one partial antenna, wherein each partial antenna includes a plurality of phase centers, transmit/receive modules assigned to the plurality of phase centers, and a signal processor for coherent processing of signals of the phase centers, the method comprising:
digitizing and processing analog receive signals from the transmit/receive modules of the phase centers;
converting the digitally processed receive signals into analog signals and to be fed to an analog receive network; and
combining the analog signals of respective transmit/receive modules with one another to form an output signal.
15. The method according to claim 14 , wherein the signal processor comprises a hybrid beam forming module to perform the digitizing and processing.
16. The method according to claim 14 , feeding the analog signals to the analog receive network.
17. The method according to claim 16 , wherein the analog signals are combined by the analog receive network.
18. The method according to claim 16 , further comprising calibrating the analog signals with a digital calibration signal directly generated at inputs of the analog receive network.
19. The method according to claim 14 , wherein the combining of the analog signals comprises a summation of the analog signals.
20. The method according to claim 14 , further comprising:
processing the output signal; and
feeding the processed output signal to a central processing unit having an analog-to-digital converter.