Quasioptimal control in diversed signal transmission

Abstract

To increase the noise immunity of signal transmission, diversity methods are now widely used, consisting in obtaining and combining several copies of the transmitted signal. In this case, it is possible to perform a combination either before the detection procedure or after it. If you do not take into account the possible use of non-linear types of modulation, then the pre-detector combination always has advantages over the post-detector combination. However, taking into account the nonlinear properties of the transmitted signals, new possibilities appear for increasing the noise immunity in combination and simplifying the processing. In the case of using analog signals, in particular frequency modulation, at certain points in time, the pre-detection combination can lose to the post-detection combination. At the same time, by combining pre-detector and post-detector combining circuits, it is possible to lower the threshold level during demodulation and increase noise immunity. In the case of using digital modes of modulation, it is possible to process only the signals after demodulation without reducing the noise immunity and to eliminate the need for preliminary phasing of the diversity signals before detection.