GENERATION OF COMPLEMENTARY CODES AND DOUBLY CO-OPERATIVE TERNARY SEQUENCES AND THEIR COMPARITIVE STUDY IN AMBIGUITY DOMAIN

摘要

Pulse coding and linear frequency modulation in analog or discrete form are widely used in radar systems for pulse compression to achieve high range resolution. Such coded waveforms are detected by a threshold detector after matched filtering. Complementary codes, which use multiple binary sequences exhibit the most desirable characteristics, so that they achieve perfect side lobe cancellation. Here generation of complementary codes is presented whose sum of autocorrelation functions is double the length of the sequence for zero shift and zero for other shifts and pairs of doubly co-operative ternary sequences which are co-operative not only in the autocorrelation domain but also in the signal domain is presented. The energy efficiency of the sequences is found as unity or 100%. The choice of the selection of the sequence in the case of complementary sequences is restricted to a few number of sequences where as in doubly co-operative sequences, the choice is broader. This is due to the property of the co-operative sequence is slightly relaxed from complementary codes as side lobe is relaxed to 1 from zero in the case of complementary codes. The radar ambiguity function represents the output of the matched filter used by the radar designers which provides information about how different waveforms may be suitable for various radar applications. The behaviour of complementary sequences and doubly co-operative sequences is studied in ambiguity domain.