Intermodulation distortion owing to multipath propagation over f.m./f.d.m. microwave links

A theory on intermodulation noise distortion owing to multipath reception in f.m./f.d.m. microwave links is developed for the case when the received signal is Nakagami-Rice distributed, i.e. depends on the addition of a constant signal and a Rayleigh-distributed random signal. The distortion formula derived by Medhurst concerning `the small constant echo of short delay¿, is verified as a special case of the presented solution. It is shown that the median value of the distortion noise power produced when the echo is a non-coherent random signal may be computed as if the echo were constant with a power equal to the total echo power and with a relative delay time equal to the 2nd-order moment (radius of inertia) of the echo-power function with respect to the constant (direct) signal. The probability distribution of the distortion is derived when the received signal is Nakagami-Rice distributed.