A fully digital noncoherent and coherent GMSK receiver architecturewith joint symbol timing error and frequency offset estimation

摘要

We propose a fully digital noncoherent and coherent Gaussiannminimum shift keying (GMSK) receiver architecture with joint frequencynoffset compensation and symbol timing recovery. Carrier phase offset cannbe estimated if the coherent demodulation mode is adopted. The convertednbase-band complex signal is first frequency discriminated and thennpassed through a digital filter which performs a fast Fourier transformn(FFT). The frequency offset can be estimated from the DC component ofnthe FFT, and the symbol timing error can be estimated from the phasenangle of the FFT at a specified frequency which is equal to an integralnmultiple of half the bit rate. These two estimated parameters are thennused for frequency offset compensation and symbol timing recovery duringna preamble period. Coarse carrier phase can be estimated by averagingnsampled in-phase and quadrature-phase signals and finding its phasenangle within the preamble period after carrier frequency offset isnestimated and compensated. The bit error rate (BER) performance of thisnGMSK receiver architecture is assessed for an additive white Gaussiannnoise (AWGN) channel by computer simulation