This paper presents a system of audio signal processing based on FPGA,the system uses audio codec chip LM4550 to A/D transform and D/A transform the input analog audio signal and output digital audio signal.Using FPGA as the high speed signal processor to realize volume adjustment and audio effect control,so it can output different style music.Meantime, the system designs a FFT computing module and control system of VGA display interface,to compute the digital audio signal which is A/D transformed,and real-time display the frequency spectrum of audio signal on VGA.

A differential phase error detector is inserted in the carrier loop structure for improving the dynamic performance of the loop in GNSS receiver in this paper. It is used to detect the abnormal phase jitter and amplify the adjusting increment for fast tracking. In order to avoid the differential detector amplifying noise interference in locking, fuzzy logical theory is introduced into the loop to control the amplification caused by the differential detector. Finally simulations show that the proposed design achieves high dynamic performance with effectively speeding up the tracking and widening the dynamic stress range.