Multi-frequency high frequency surface wave radar based on phase offset

Multi-frequency high frequency surface wave radar (MHFSWR) shows good capability of anti-interference, sea-state information extraction and target detection. The authors develop a new technique to produce a specified Doppler frequency offset on the echoes spectra for each operating frequency in simultaneous MHFSWR system. The radar transmits frequency modulated interrupted continuous wave signals with different linear phase offsets which are counted up from sweep cycle to sweep cycle. After the echoes being demodulated, the signals of different operating frequencies from same range can be distinguished by the preset frequency offsets in a single Doppler spectrum, though they are indiscernible in the A-Scope display. In the receiver, both the data transmission channel and the signal processing channel of different operating frequency, including digital down-conversion, data rate conversion and range-Doppler transform, are shared significantly reducing the hardware cost and system complexity. The simulation results and the initial observations obtained by the radar verify the feasibility of the proposed technique. This technique is applicable in monostatic radars, bistatic radars and networking radars to apply multi-frequency observations simultaneously.