Complementary Pair Radar Waveforms Figure 15. Delay-Doppler response, GWS and LPF, Doppler shift = 0, no pulse canceller. Zoom on |τ| ≤ tp. sidelobes cancellation. In [7] the originators of the GWS bit representation compared it with several constant-amplitude schemes (phase shift keying, minimum phase shift keying, and derivative phase shift keying) and found that those alternatives worsen the ACF sidelobes of coded radar waveforms. In [8] a continuous phase modulation (CPM) transformation was used, which also increased the delay sidelobes. A remedy described in [8] suggests using mismatched filters to reduce the sidelobes at a cost of some signal-to-noise ratio (SNR) loss. Such a remedy does not suit the concept of complementary pair sidelobe cancellation rather than sidelobe reduction. Figure 16 compares the ACF mainlobe vicinity of the three spectrally efficient implementations. Only the GWS implementation (top) maintained the cancellation of the ACF near-sidelobes. In the CPM version (middle) high near-sidelobes reappear with a peak of −22 dB. The derivative-phase version (bottom) yielded peak near-sidelobe of −34 dB. A fourth representation should be of interest. It uses the biphase-to-quadriphase transformation [9, 4 (sec. 6.8)]. The quad- Figure 16. ACF mainlobe comparison between three spectrally efficient implementations of a 26 element complementary pair. 48 IEEE A&E SYSTEMS MAGAZINE MARCH 2017