Research And Implementation Of Digital Down Conversion Based On FPGA

Today, in domestic wireless communication systems, the signal processing unit is restricted by the sampling rate and purchase channels of the A/D converter in the front-end and the processing speed of baseband data processing module in the back-end. First of all. a received RF signal is must to be converted into an appropriate IF signal.Then it is down converted in the digital IF-band. This process includes data collecting, orthogonal mixer, decimation Filter, shaping Filter. Up to now, a high speed RF signal becomes a baseband digital signal and then the baseband digital Signal is connected to a digital signal processing unit. The ultimate goal of DDC is to achieve the extraction of received signal. Function of the digital signal processing unit includes carrier-recovery-processing, demodulating, decoding and so on. The purpose of Band-pass Sampling is to reduce the sample rate of A/D converter. At the same time, it can solve the difficulties caused by the processing clock. Therefore, Design and Implementation of DDC has a very important practical significance in modern wireless communication.Gradually, FPGA replaces many expensive application specific integrated circuits because of its good produce performance, high integration degree and low power consumption. The general hardware platform can be used in a FPGA circuit design. The FPGA circuit design can reduce the hardware complexity of circuit design and has considerable advantages in the software update, unit interconnection, debugging and testing, etc.This thesis explain the theory of Sampling Theory of Signal, NCO. orthogonal demodulation, digital filter and some other related theories. It also analyzes the feasibility of implementation of digital down conversion technology Based on FPGA. This result has been verified on general hardware platform. The main work of this paper includes the following points:Introduced some basic theory of digital down conversion, given a detailed exposition of the comparison of digital down conversion based on specific DDC chip and on FPGA and declared the advantages of digital down conversion based on FPGA.Design and implementation is discussed in the terms of both hardware and software. The Circuit Principle is introduced in detail in term of hardware and the steps of DDC Based on FPGA are listed in term of software.Given the test and simulation results of the digital down converter based on FPGA platform (EP4SE530 of Stratix IV series).