Equalization techniques for multipath mitigation in aeronautical telemetry

This paper describes the application of adaptive equalization based on the constant modulus algorithm (CMA) and the decision-directed minimum mean squared error (DF-MMSE) concept to the two compatible offset QPSK waveforms (FQPSK and SOQPSK-TG) that constitute the ARTM tier-1 waveforms. An adaptive version of the DF-MMSE equalizer is developed and applied to this application. In the presence of frequency selective multipath interference typically encountered in aeronautical telemetry, both equalization techniques are shown to provide reliable performance for FQPSK and SOQPSK-TG. The performance of both waveforms with the DF-MMSE equalizer is slightly better than that using the CMA equalizer. Implementation trade-offs between the two types of equalizers are discussed.