Low-complexity fractional-spaced equalization approach in the frequency domain for CPM

In this paper, a new receiver architecture with frequency-domain equalization (FDE) for continuous phase modulation (CPM) is proposed. With fractional-spaced FDE for up-sampled CPM signal, receivers designed for additive white Gaussian noise (AWGN) channel can be used for demodulating and detecting the CPM signal. Low complexity fractional-spaced channel estimation and FDE algorithms, which can estimate and equalize multipath channels with fractional-spaced delays, are also proposed in this paper. Moreover, we use linear frequency modulation sequence instead of Chu or FrankZ sequence to estimate the multipath channels, and reasons are analyzed. Bit error rate (BER) performances of ARTM CPM, FQPSK and SOQPSK-MIL modulations are simulated in different multipath channels, and simulation results show that the fractional-spaced FDE approach can effectively overcome the effects of multipath channels with long and fractional-spaced delays.