Design ofFrequency Synthesizer forSynchronizing Airborne Bistatic SARSystems

Bistatic synthetic aperture radar (BiSAR) offers many operational advantages; however, itresults in technical problems suchas synchronization of the oscillators andadjustment ofthetransmit pulseversus receive gatetiming. Consequently, highlyaccurate frequency synchronization mustbeensured. Inspired bythe widely usedGPSfortimeandfrequency transfer, this paper concentrates onthedesign ofaGPSdisciplined frequency synthesizer forsynchronizing airborne BiSARsystems. In this paper, boththetransmitter andreceiver contain aGPS disciplined oscillator, withfrequency trimmed bytheuseof a tuningvaractor-diode. Thereafter, a direct digital synthesizer (DDS)basedmultiple tunedfrequency synthesizer isapplied togenerate thewholesystem frequencies. Moreover, togetaround thedisadvantage of inconsistent wideband radarwaveform performance, a novel technique isproposed. Itisshownthat this technique canprovide asolution ofsynchronizing airborne BiSAR systems. 2