The Design Of Digital Intermediate Frequency Transceiver Based On Soft-defined Radio

Soft-defined radio technology has the advantages of diversity,reconfigurability and expansibility.For communication systems with different application stages,environments and requirements,softdefined radio technology can provide matching design without changing hardware conditions.In order to improve the flexibility of digital signal processing(DSP)and reduce the pressure of PC data processing,a digital IF transceiver based on fixed hardware platform and software radio technology are studied in this paper.The main work of this paper includes:1)A digital IF transceiver program based on soft-defined radio is proposed.For the purpose of multimode and multifunctional application,the digital IF transceiver adopts a modular DSP function architecture based on FPGA.The DSP functions include digital frequency conversion,interpolation,decimation and FFT calculation.In addition,the digital IF transceiver has characteristics of high expansibility and flexibility.2)The design of digital IF transceiver is completed.The hardware part includes the design of peripheral circuit of AD9258,DAC5686 and STM32 MCU.The peripheral circuit includes the design of differential input,low jitter clock source,current sink type output circuit of DAC and the connection of SPI control line between SCM and ADC and DAC.ADC and DAC communicate with FPGA on the digital board through digital interface,and FPGA is the Cyclone series chip from ALTERA company.The software part includes program of MCU and FPGA.The MCU program is used to configure the registers of ADC and DAC.The FPGA program includes modules of DDC,interpolation,decimation and FFT.In signal simulation,LABVIEW and MATLAB are used to reduce the usage of FPGA resource and improve the performance of DSP modules.The decimation filter module is optimized by using CIC+FIR combined filter to achieve the maximum 128 decimation function.The FFT calculation is realized by dynamic loading of window data and zero filling.3)The function test of digital IF transceiver is completed.The work includes the debugging of data link and the programming of upper computer processing software.The results show that the DSP function modules are stable and achieve the design goal.In this digital IF transceiver,the function of data rate conversion and spectrum analysis can be realized in a variety of systems with high flexibility and practicability.