Research On The Key Technologies Of All-digital QAM Receiver

With the increasing development of communication science, the technologies of all-digital receiver have been widely applied in many fields. This paper focuses on two key technologies in the all-digital QAM receiver---symbol synchronization and channel blind equalization. In the aspect of symbol synchronization, firstly, the theory of interpolation filter has been studied, and the performance of interpolation filter has been improved by using liner weighted MSE (minimum square error) principle, and the simulation results show that the performance is better than the original interpolator; secondly, a classical timing error detection algorithm---Gardner algorithm has been studied in detail. An improved structure of the detector is used to resist the large self-noise and the simulation results show that this structure can efficiently reduce both the self-noise and the timing jitter. In the aspect of blind equalization, CMA(constant modulus algorithm) and its improved algorithm have been studied. And then two improved methods are studied in view of the large steady residual error: one is the improvement of the equalizer coefficients updating,and the other is the combination of MMA and DD-LMS. Simulation results show that both two methods can reduce steady residual error and improve the performance of equalization.