Wideband Digital Receiver Algorithm Research And Fpga Implementation

Digitization and broad-banding have become the trend of wireless communications today. Along with its rapid development, the radio spectrum monitoring and management is becoming increasingly important. As an important spectrum monitoring equipment, the advanced nature and stability of the monitoring receiver provides a strong guarantee for the radio spectrum monitor system. Therefore, the researching and developing of radio digital wideband monitoring receiver based on Software Defined Radio has great application foreground and vast development space.With the development of wireless communication technology and the popularity of the FPGA development, many digital receiver products have been developed at home and abroad. Under leaded of government, the small civil digital monitoring receiver develops rapidly in China in recent years. But comparing to the advanced foreign monitoring systems, there is still a long way for us to keep up with them in some key Performance Indices. From this point, with an in-depth study of the algorithms and structures involved in the monitoring receiver, the project in this dissertation develops a radio digital wideband monitoring experimental system, with functions including RF front-end signal reception, digital IF processing and monitoring software for the upper computer, and found early success.Contents of this dissertation are mainly about researches of the digital IF processing tasks handling in FPGA branch system, including simulation and realization of algorithms and structures in the functions of automatic gain control (AGC), digital down convertion (DDC), spectrum analysis, etc. Firstly, the scheme for the overall design of the FPGA branch system and design method of the main modules and parameters are given in detail where the variable bandwidth digital down converter (VB-DDC) and spectrum analysis module are highlighted. Then a preliminary analysis and validation of the system are completed by MATLAB software and Model Sim simulation tool. Finally, hardware debugging on a customized receiver system dedicated development board is given out for the modules and system. Functional tests indicate the success of this design. The frequency accuracy of the Local Oscillator signal generated by the NCO module, which is implemented based on CORDIC algorithm, can reach up to1Hz. Meanwhile, it provides17IF filters and can adapt to signals in different form. According to the instruction of the PC monitoring software, VB-DDC module can realize a signal reception from different central frequency and different processing bandwidth. The FFT size and spectral smoothing factor in the spectrum analysis module can be changed in real-time. The FFT processing length can vary from512,1024to2048and the range of spectral smoothing factor is from1to16. Thinking with the characters of the VB-DDC, different FFT resolution bandwidths can be achieved by changing the parameters in both VB-DDC and spectral analysis module when monitoring a same signal. The signal to noise ratio (SNR) of the spectrum results output of this system can be effectively improved by the addition of spectrum smoothing module.