igh degree of accuracy, linearly increasing with (SJR)(dB) , the slope of the line being 0.2. It is therefore concluded that, given a spread tone jammer of Tone Jamming AWGN Jamming "Equivalent" AWGN Jamming Signal-to- - - Jammer Power Ratio, dB Figure 1.16. QPSK bit error probability versus SJR/dl for AWGN and tone jam- ming and spread tone "equivalent" AWGN jamming. Performance of FH/PN/QpSK in the Presence of Partial-Band Multitone Jamming (SJR)(dB), , an "equivalent" AWGN jammer can be devised for which (SJR)equiv(dB)=(08)x(SJR)(d) (1.97) If the SJR's are measured in ordinary numbers rather than decibels, then (1.97) implies that (1.98) From (1.96) and (1.98), it then follows that the spread tone jammer can be conveniently thought of as an "equivalent" AWGN jammer with corre- sponding bit error probability (1.99) Equation (1.99) has been plotted in Figure 1.16 (dashed lines), from which the high degree of agreement with the exact expression for P'b, can be witnessed. The range of applicability of (1.99) is, for the current purposes, more than adequate since, in the frequency bands where the jammer is pre- sent, the system is forced to operate at high bit error probabilities (this is especially true when the jammer strategy, i.e., choice of p, has been opti- mized). From (1.99), it follows that the overall average bit error probability (accounting for partial-band jamming) is given by (1.100) The worst case jammer can be found from (1.100), with the result (1.101) Eg/N,<009220 with corresponding Eb/N, 0.9220 (1.102) i < 0.9220. A comparison of (1.102) with (1.73) indicates that the worst tone jammer for FH/PN/QPSK is slightly less effective than the worst noise jammer for FH/QPSK. Coherent Modulation Techniques 1.6 PERFORMANCE OF FH/PN/QASK IN THE PRESENCE OF PARTIAL-BAND MULTITONE JAMMING A line of thought similar to that of Section 1.6 also applies here. The tone- noise jamming equivalence discussed in Section 1.6 is also applicable because the first Q function in (1.82) dominates over the other terms in the