Design of Frequency Synthesizer for Synchronizing Airborne Bistatic SAR Systems

Bistatic synthetic aperture radar (BiSAR) offers many operational advantages; however, it results in technical problems such as synchronization of the oscillators and adjustment of the transmit pulse versus receive gate timing. Consequently, highly accurate frequency synchronization must be ensured. Inspired by the widely used GPS for time and frequency transfer, this paper concentrates on the design of a GPS disciplined frequency synthesizer for synchronizing airborne BiSAR systems. In this paper, both the transmitter and receiver contain a GPS disciplined oscillator, with frequency trimmed by the use of a tuning varactor-diode. Thereafter, a direct digital synthesizer (DDS) based multiple tuned frequency synthesizer is applied to generate the whole system frequencies. Moreover, to get around the disadvantage of inconsistent wideband radar waveform performance, a novel technique is proposed. It is shown that this technique can provide a solution of synchronizing airborne BiSAR systems.