Performance Analysis of Continuous-Phase Frequency Shift Keying Modulation in Atmospheric Noise.

摘要

Continuous phase frequency shift keying (CPFSK) is potentially an attractive modulation scheme with performance better than PSK in Gaussian noise. The optimum coherent M-ary CPFSK receiver has been developed for operation in Gaussian noise. In this report the optimum receiver performance is evaluated assuming operation at very low frequencies. Atmospheric noise is the most prevalent interference when operating at very low frequencies. An analytic amplitude probability distribution (APD) function is developed that closely approximates the Crichlow atmospheric noise APD model which is based on empirically measured data. The analytic expression for the APD was developed by combining a Rayleigh and a lognormal density and obtaining the corresponding distribution function. By correctly choosing values for two parameters in the distribution, it approximates the atmospheric noise APD for various Vd ratios. The performance of the optimum coherent M-ary CPFSK receiver was evaluated for m=4 and n=3 operating in atmospheric noise with specific Vd ratios (4 and 5). The evaluation consists of finding a probability of error bound for a sub-optimum receiver, which is valid for high signal-to-noise ratios (SNR).