Research On Design Method Of Variable Frequency Band-Pass Filter

During the process of sending the signal propagation,in certain degree might generate some other unwanted signal components. So we are faced to extract the useful signal from the noise original signal which is the core filtering technology, is also involved in modern communication signal processing necessary link. Digital Filter is a very important part of a communication signal processing system. With the algorithm or software to realize the digital filter. Digital filter has more functions and advantages compared to analog filter,such as high precision, high stability, small volume, low cost, parameters easy adjustment, high work efficiency,etc..For the many advantages and application prospect of digital FIR band-pass filter,this paper based on the digital filtering technology and digital signal processing principle, put forward the design method of variable frequency band FIR(finite impulse response) band pass filter based on MATLAB. Variable filter has high flexibility. Variable frequency band bandpass filter can also achieve the new desired frequency characteristics of new without off-line design new filter again. So the research of this dissertation has great significance. Variable frequency band bandpass filter design realizing method is after estimation of the center frequency estimation and bandwidth estimation on the original type noise signal, according to the different estimated bandwidth and center frequency calculate the different FIR bandpass filter parameters. So we can realize the flexible filter design. Parameter estimation of digital communication signals (estimation of the center frequency and bandwidth) is a very important research direction of communication signals.This paper first studies several commonly used algorithm to estimate the center frequency and bandwidth, then to simulate compared the algorithm,found that they all limited, low SNR estimation accuracy. Thus researched the bandwidth estimation based on Welch and the center frequency estimation method based on iterative method. Welch bandwidth estimation has good stability and high precision than the commonly used methods m like the modified covariance method and the MUSIC method. The center frequency estimation method based on iterative methods has characteristics of adapt to low signal-to-noise ratio, large frequency measurement range, small computation compared to the classic center frequency estimation method. Variable frequency digital band-pass FIR filter has a broad application prospect.And along with the new development of communication signal processing and continuous put forward of new algorithm and new structure, the digital filter can meet the higher application requirements and the performance also will getting better.