COMPLEMENTARY SEQUENCES WITH HIGH SIDELOBE SUPPRESSION FACTORS FOR STMST RADAR APPLICATIONS/

Under ideal conditions, complementary code pairs produce no sidelobes. In practice, sidelobes are produced, among other things, when the per iod of the Doppler frequency shift as well as the time of coherence of clear air turbulence are comparable (or smaller) than the interpulse period. The intensity of sidelobes increases with the radar operating frequency and becomes a real problem in the upper VHF and UHF bands. I n this paper, a new technique for reducing sidelobes originating from atmospheric characteristics for clear air radar systems using pulse co ding is presented. For this, a generalized analytic expression for a s idelobe suppression factor applicable to any number of binary code seq uences is first derived. This is then used to develop the technique, w hich in the case of complementary codes consists of manipulating the o rder of transmission of the code sequences. For such codes, improvemen ts in sidelobe suppression of the order of 80 dB on the VHF frequency band are obtained. The modifications required to implement the techniq ue into existing systems are very few and simple.