Improved digital FM transmission with limiter-discriminator detection

Three techniques for improving the performance of discriminator detection of digital FM are presented. In the first technique, use is made of detection theory to develop an efficient scheme for detecting the occurrence of a click and for correcting its effects in the demodulated signal. The second technique is used to combat the triangular noise. An improvement of the signal-to-noise ratio in the decoder is achieved by filtering the demodulated signal. The interest of the proposed method lies in the use of partial response encoding technique in the receiver to perform this filtering operation. The third technique counteracts nonlinear distortion by taking advantage of maximum likelihood sequence estimation. It leads to a reduced state Viterbi decoder. A specific example is given in which these three methods are successfully applied at the same time