Comparison of Complementary Sequences in Hybrid Phase and Frequency Shift Keying CW Radar Using Periodic Ambiguity Analysis
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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Continuous waveform CW polyphase sequences for radar have a much lower power spectral density PSD than pulsed signals but can retain the same target detection capability. The use of different phase values or subcodes to modulate the carrier provides a low probability of intercept LPI radar waveform which cannot be seen by a noncooperative intercept receiver NCIR. Also, it is a low probability of detection LPD waveform due to the low PSD. Frequency shift keying FSK radar has a higher PSD but is moved about quickly in frequency over a large bandwidth in which the NCIR cannot follow. Consequently, the FSK usually a Costas frequency set remains a LPI signal but not a LPD. To combine the advantages of each waveform, this thesis presents a hybrid FSKPSK emitter waveform to further the LPI, LPD characteristics. By combining both techniques PSKFSK, a high time-bandwidth waveform is constructed that provides better LPILPD characteristics than each waveform. The periodic ambiguity function PAF is evaluated for three different complementary sequences to modulate a Costas frequency set. The peak time and Doppler sidelobes of the PAF are compared against the P4 polyphase modulation for the Golay complementary sequence 15 dB improvement, the quaternary periodic complementary sequence 16 dB improvement, and the quaternary Golay complementary sequence 18 dB improvement.
- Active and Passive Radar Detection and Equipment