The design of frequency synthesizer for the ocean state measuring and analyzing radar

The design and realization of a synthesizer for high frequency radar, OSMAR2003 (ocean state measuring and analyzing radar), is proposed. To provide a 47.5 MHz local signal and 7 MHz transmitting signal, two kinds of frequency synthesizer architectures are presented, and their advantages and disadvantages are compared. The preferred synthesizer is based on an architecture supporting a flexible combination of direct synthesizer and DDS (direct digital synthesizer) techniques with a low frequency reference crystal oscillator. The benefit of this architecture is the generation of signals with low phase noise and low spurious level. The measured output spectrum and field experiments undertaken in Zhujiajian Island demonstrate successful frequency synthesis operation.