Shortwave Channel Equalizer

In this paper the equalizer technology of serical transmission of HF digital communication system and the algorithm implement of fixed-point DSP were studied. According to the characteristic of HF channel, the Watterson model which was CCIR recommended was made. The adaptability of the different structure of equalizer to HF channel characteristic were analysized . The simulation result indicated the decision-feedback equalizer(DFE) had good adaptability to HF channel. The converagingbehavior and tracking behavior of two kinds of the adaptive algorithm-LMS algorithmand RLS algorithm were analysized. The Matlab Language and C Language were applied to simulate the fixed-point DSP arithmetic of equalizer algorithm. The simulation result indicated the diveragence phenomenon would happen to ADFE(adaptive decision feedback equalizer) based on RLS algorithm under the fixed-point finite-precision arithmetic. The computational complexitity of Inverse QR-RLS algorithm and Square-Root Kalman algorithm which had numerical stability were analysized. Because the QR-RLS needed the Squart-Root and inverse of matirx operation, which had large computation, was not fit for fixed-point DSP implement of real time, ADFE based on Square-Root Kalman algorithm was applied to fixed-point DSP algorithm implement of the equalizer of HF channel. The simulation result of the equalizer of the moderate HF channel indicated the ADFE based on Square-Root Kalman algorithm was upstanding and had numerical stability. According to Square-Root Kalman algorithm having the phenomenon of the round-off error accumulated, periodical training and the initialization of the algorithm was applied. At last, the scheme of the algorithm implement of fixed-point DSP was presented.