 form of the transmitted signal in the i-th transmission interval iT's + 1)Ts is (1.1) where S is the transmitted power, fo is the carrier frequency, is the random phase associated with the i-th transmitted tone, Af = kTs (k integer) is the frequency spacing between tones in the M-ary set, and d is the value of the i-th data symbol chosen from the set of integers {1, 2, reduce chance of the interceptor detecting his message and also to combat jamming, the communicator will employ an SS modulation which typically takes on the form of frequency hopping (FH) or a combination (hybrid) of FH with time hopping (TH) and/or direct-sequence pseudonoise (PN). Thus, the four basic SS modulations employed in most LPI systems transmitting MFSK data Low Probability of Intercept Communications modulation are FH, FH/PN, FH/TH, and FH/PN/TH. The intrinsic forms of the transmitted signals corresponding to the first two of these SS modula- tions are ¹ s(t) = n,({0,1,2,...,N7- - 1} Th = hop time interval NT = total number of hops in SS bandwidth (1.2) FH/PN iThsts(i+1)T, s(t) = h,{{{{,1,3,...,NT c(t) = PN modulation T C = PN chip time interval. (1.3) (Note that here the hop frequency spacing is 1/Tc, a factor of Th/Tc larger than for pure FH, to accommodate the bandwidth of the PN modulation.) Although the time-hopped SS modulation types are of interest, we shall focus our attention on the two more commonly found in LPI applications, namely, FH and FH/PN, occasionally making reference to the hybrid TH forms whenever appropriate. 1.2 INTERCEPTION DETECTORS A great amount of effort has been expended over the past decade on the subject of the properties, configurations, performance, and implementation of intercept detectors and many reports and papers are available which delineate basic detector topology and optimum configurations and methods for performance analysis [1]-[6]. The results produced lay the necessary foundations and provide bounding criteria for detectability as a function of the principal parameters: detection SNR (S/No)