Design And Implementation Of Multi-mode Intermediate Frequency Of Software Radio Based On FPGA

With the rapid development of wireless communication technology, the mobile communication system is rapidly upgrading. However, the traditional mobile communication equipment mainly depends on the fixed hardware circuit, which is difficult to support the smooth upgrade and compatibility of mobile communication system. Software defined radio(SDR) technology which takes the hardware and software as foundation and core can effectively solve the problems of smooth upgrade and compatibility of mobile communication system, and the digital intermediate frequency technology is not only the core technology of SDR, but also the key bottleneck of SDR.Therefore, in this thesis, the multi-mode intermediate frequency fusion scheme is proposed based on the research of digital intermediate frequency, and then utilizing Field Programmable Gate Array(FPGA) to implement the multi-mode intermediate frequency architecture.Firstly, the fusion scheme of multi-mode intermediate frequency is designed. The structure of single mode digital intermediate frequency is deeply studied based on the theory of bandpass sampling, multi-rate signal processing and digital signal orthogonal transformation. Moreover, the technologies of multiplexing and flexible configuration are adopted to design the fusion scheme of multi-mode intermediate frequency, which not only can be compatible with different communication systems, but also can save lots of hardware resources compared with the collateral multi-mode intermediate frequency.Secondly, the design and simulation verification of the multi-mode intermediate frequency algorithm are performed, and the digital mixer and anti-aliasing filter of the multi-mode intermediate frequency are deeply studied and optimized. Consequently, according to the fusion scheme of multi-mode intermediate frequency and the signal characteristics of five kinds of communication systems, the system parameters and MATLAB simulation algorithm of multi-mode intermediate frequency are designed. Simulation results verify the effectiveness of the multi-mode intermediate frequency algorithm.Then, the design and FPGA implementation of multi-mode intermediate frequency system is performed based on the SDR platform and the core modules of multi-mode intermediate is improved. An improved pipelined Coordinate Rotation Digital Computer(CORDIC) circuit is adopted for the design of digital mixer; the improved Distributed Algorithm(DA) is utilized for the design of the high order FIR filter instead of the multiply accumulate method; the design of CIC filter and HBF filter increase the functions of serial dual channel and parameter configuration. Furthermore, the methods of ROM look-up table and state machine are used together to design a multi-mode Radio Frequency(RF) configuration system for the RF configuration of the platform. Moreover, the detailed design and test of RF chip configuration interface, and peripheral interface EMIF, McBSP and network port are introduced.Finally, the testing platform of SDR hardware is built to test the receive path and the transmit path of the multi-mode intermediate frequency system, and the testing results verify the validity of the design and FPGA implementation of multi-mode intermediate frequency, multi-mode RF configuration and peripheral interface.