A low-cost dual-mode noncoherent receiver with robust frequency-offset compensation

A robust frequency-offset compensation technique is proposed and studied for a low-cost noncoherent receiver which can demodulate both analog FM and digital /spl pi//4-differential quadrature phase shift keying (DQPSK) signals. In the noncoherent receiver, which employs a frequency discriminator, the RF/IF carrier frequency offset is converted into DC offset in baseband. A baseband DC-offset compensation technique with a modulo 2/spl pi/ operation is proposed to counteract the RF/IF frequency offset. Computer simulations and hardware experiments were conducted to evaluate the performance of the proposed receiver in a static additive white Gaussian noise (AWGN) environment with receiver frequency-offset. It is demonstrated that with the proposed technique using only five preamble symbols, the power penalty for /spl pi//4-DQPSK is 2 dB for /spl Delta/fT/sub s/ = 10%, where /spl Delta/fT/sub s/ is the offset frequency (/spl Delta/f) normalized to the symbol rate (1/T/sub s/).