Research And FPGA Implementation Of CIC Filter In Software Defined Radio

One of the basic ideas of software-defined radio is to extend digital signal processing to the antenna,thereby expanding to the analog signal processing area that has dominated so far.It can be easily recognized that the hardware platform is the most important enabling component of a software radio terminal.Part of the processing of the analog signal in the terminal is replaced by digital signal processing,that is,the digital front end.The digital front end includes multi-rate signal processing.To prevent the sampled signal from being distorted,it is generally to increase the sampling rate in AD as much as possible,but this will increase The data flow rate of the latter part is large.When the data flow rate becomes very large,the back-end processor must have a strong processing capacity to process the data.Therefore,it is necessary to perform rate conversion on the sampling signal after AD to reduce the sampling rate,which can reduce the requirements for subsequent processing capabilities and save resources.In this context,the paper designs and designs the CIC(Cascaded Integrator-Comb)filters commonly used in software radio multi-rate signal processing.Because most of the digital front-ends in today's software radio use traditional CIC filters,traditional CIC filters have disadvantages such as passband droop and small stopband attenuation.Therefore,a better CIC filter structure can be designed to improve the passband droop,small stopband attenuation,and other shortcomings,to achieve better performance filters.This paper first analyzes the interpolation and decimation in multi-rate signal processing,and also analyzes the traditional CIC filters,half-band filters and filter banks.Secondly,by consulting a large amount of data,based on the traditional CIC filter,a new CIC filter structure is proposed,and the characteristics of the CIC filter are improved with new sharpening techniques.Then,the traditional CIC filter and the new sharpened CIC filter were simulated and analyzed under the same parameters,and it was demonstrated that the new sharpened CIC filter has better passband flatness and larger stopband attenuation.Finally,a multi-rate extraction model based on the new sharpened CIC filter was built in ISE using verilog language,and the hardware resources occupied by the multi-rate extraction model were analyzed.The functional simulation analysis and analysis of the multi-rate extraction model with ModelSim Timing simulation analysis,test results show that the signal rateconversion is good,verifying the correctness and applicability of the new structure.