PSK) data modulation and binary PN modulation. However, the most common form employs BPSK data modulation and quaternary phase-shift-keying (QPSK) PN modulation. This has some potential advantage against a single tone jammer at the trans- mitted signal carrier frequency. It forces the jammer power to be evenly dis- tributed over the cosine and sine signal coordinates. Section 3.4 of Chapter 3, Part 1, describes the uncoded direct-sequence spread binary phase-shift-keying (DS/BPSK) signal which is given by x(t) = c(t)d(t)V2S cos co,1 = c(t)s(t) (1.4) where (1.5) is the unspread BPSK signal. Defining T as the data bit time interval and T as the PN sequence bit time interval, s(t) has a sin2x/x2 spectrum of band- width roughly 1/Tb while the spread-spectrum signal x(t) has a familiar- shaped spectrum but of bandwidth roughly Wss=1/Tc (1.6) The processing gain is (1.7) The jamming signal is represented by J(t) and in the absence of noise (assume the jammer limits performance) the signal at the receiver is x(t) + J(t). (1.8) The receiver multiplies this by the PN waveform to obtain the signal r(t) = = ((c)(x(t) + J(t)] = t) + c(t)J(t) (1.9) Perfect chip synchronization is assumed for the intended receiver. Chip sequence acquisition and synchronization techniques are presented in Chapters 1 and 2, Part 4. Coherent Direct-Sequence Systems since c2(t)==1. (1.10) Here c(t)J(t) is the effective noise waveform due to jamming. The conventional BPSK detector (see Figure 3.6 of Chapter 3, Part 1) out- put is thus r=dVE,+n (1.11) where d is the data bit for the Tb second interval, Eb = ST is the bit energy, and n is the equivalent noise component given by (1.12) For QPSK modulation the inphase and quadrature data waveforms are denoted de(t) and d&(t), respectively, and corresponding PN binary waveforms are cc(t) and cs(t). These form a QPSK signal + cs(t)d3(t) WOT (1.13) where each QPSK pulse is of duration Ts = 2Tb. The channel output wave- form given by (1.8) is multipled by wot and integrated over Ts seconds to obtain the in