A BICMOS PDF notch circuit for FM-DCSK communication over selective channels

A BICMOS circuit is presented which can be electrically programmed to alter the probability density function of a random/chaotic PAM stream and to create a set of null probability. In an FM-DCSK communication system its adoption ahead of the FM modulator allows to place an interval of reduced power in the spectrum of the wideband transmitted signal in correspondence to the in-band multipath related nulls. The expected performance improvement over selective channels is confirmed by the numerical esteem of the bit error rate as a function of the bit-energy/noise-spectral-density ratio.