Orthogonal and complementary radar signals for multichannel applications

Modern radar include more and more multiple functions and multiple channels; in this context sophisticated waveforms [1] and related processing (pulse compression, extraction of information) are an hot research and development topic. A simple multifunction radar concept includes the detection of air targets (target channel) and the analysis of atmospheric phenomena, mainly: precipitation (weather channel). In a weather channel the design of the waveforms to implement pulse compression techniques requires a low ISR (Integrated Sidelobe Ratio) i.e. less than -30 dB in some cases - while in the target channel a low PSR (Peak Sidelobe Ratio) is needed. Possible novel solutions to this, and the other problems of multifunction radar, exploit the complementary properties of Golay codes to implement pulse compression: the encoded pulses have to be transmitted simultaneously and at the same carrier frequency. To separate them in reception, their sub-pulses can be further encoded by two orthogonal codes respectively (nested orthogonal codes into the complementary codes). The performances of this technique will be evaluated in term of ISR and PSR, with respect to the Doppler shift and to the compression ratio.