Based On Fpga Digital Downconverter Design And Application

The foundamental idea of Software Defined Radio(SDR) is to establish a open,standard and modular universal hardware platform where the A/D converter is moved asclosed as possible to antenna and all of the communication function is realized bysoftware. The aim is to research and develop a high flexible and adaptablecommunication system. The technology of making A/D converter has been advancedfast. The A/D working bandwidth has covered the intermediate frequency (IF)supporting high sampling frequency and wide dynamic range and long length. Thewireless receiver technology has been developing from digital baseband to digital IF.Thusit is possible to implement the wide bandwidth digital IF receiver based onbandpass sampling theory.In this paper, a digital down converter (DDC) applied on wide bandwidth digital IFreceiver is design and implemented by FPGA. This DDC can translate digital IF signalto baseband, extract desired channel, decimate the sample sequence, multirate converterand channel shape. Using Top-Down design method, the whole DDC function is dividedto many units implemented respectively and organized to the module library. Whenapplying DDC on receiver, these function modules are selected, configured andoptimized to a complex module a designed to satisfy the wireless system demand. ThisDDC based module library and re-conftgurable structure are more flexible andprogrammable than classic ASIC down converter.This dissertation introduced the concept and the structure of Software DefinedRadio, as well as an specific application of FPGA for Software Radio.According to therequirement of system, system design and simulation was processed with MATLABSimulink, which verified the vaIidity of design. Then the design of some keymodules(interpolation and decimation filters, NCO, etc.) which were based on FPGAwas carried into execution with QuartusⅡ, and the simulation was implemented aftercomplitatioin. At last circuit was realized on PCB and applied to our project.