NON-FEEDBACK HIGH SPEED ADAPTIVE EQUALIZERS FOR FQPSK AND OTHER SPECTRAL EFFICIENCY SYSTEMS FOR LEO SATELLITE TELEMETRY SYSTEMS

Abstract

A non-feedback adaptive equalizer based on Feher Equalizer (FE) is presented and its performance is evaluated. By artificially adding notch/notches to the corrupted spectrum resulted from selectively faded LEO environments, an artificial symmetry is created and as a result the BER/BLER is improved. The location and the depth of artificial additive notches are based on the shape of the spectrum of the corrupted signal. By measuring the power in narrow bands around certain frequencies the existence of notches around those frequencies are predicted. Based on this information notches with proper depths are added to the main spectrum which results in more symmetry in the spectrum. The selection process of artificial notch/notches are based on the shape of the signal spectrum, which means that this equalizer unlike most conventional equalizer does not need any feedback. The nonfeedback nature of this equalizer improves the adaptation time over that of alternative equalizers The results presented in this paper are based on both MatLab simulations and laboratory hardware measurements.