Error Performance Analyses of Linear and Nonlinear Combining Square-Law Receivers for L-hops per Bit FH/BFSK Waveforms in Worst-Case Partial-Band Jamming

In this paper we present the results of error probability analyses for a square-law linear combining receiver and, in addition, two types of square-law nonlinear combining receivers, designed to demodulate multi-hops per bit frequency hopping (FH) binary frequency-shift-keying (BFSK) spread-spectrum waveforms in the worst-case partial-band jamming channel. The nonlinear combining receivers employ weighting strategies based on softlimiting of the square-law detector outputs adaptively to reduce jamming influence. The effect of thermal noise is fully accounted for in all of the analysis results. A number of comparative performance results are given under different parametric assumptions of practical interest. It is shown that the linear combining receiver, which is near-optimum for the non-jammed Gaussian channel, is least effective for demodulating the postulated waveform in the optimum partial-band jamming environment as compared to the nonlinear combining receivers. The effect of L, the number of hops per bit, is shown to be the key parameter in LPI waveform design in FH spread-spectrum anti-jam systems.