Design Of Digital Filter Based On Wireless RF Chip

Filter is an important part of wireless communication system which is always used for selecting signal based on the target frequency bandwidth and reducing noice. Because of high performance, small circuit area and high speed, digital filter insteads the position of analog filter in wireless communication system. So, this paper designs a variable bandwidth and frequency point bandpass digital filter for a wireless RF chip which works in 100 MHz to 1.2 GHz, and finishes its FPGA test and layout design.This paper introduces the basic principle of digital filter, proposes the circuit structure of digital filter, and emphaticly designs CIC filter groups and FIR bandpass filter. CIC filter groups include CIC filters, CIC compensation filters and gain calibration modules, which change the sampling frequency of input signal, make passband flat and make input and output signal width equal. Use some methods, such as bit width optimization, to reduce the area of CIC filter groups, optimize 36% of the area of CIC filter groups. Then the simulation results of CIC filter groups are given, and achieve that CIC filter groups have 80 tinmes,8times,4times,2times down sampling and 2 times up sampling. Next, design configurable FIR band-pass filter, finish the simulation of FIR filter, and 13 channels are adjustable in normalized angular frequency. Choose liner phase FIR filter to reduce half of the number of multiplier and based on CIC filter groups, reduce 33% of the area of FIR filter. At last, design other modules of digital filter, then the simulation results are given.The paper sets up the FPGA test stage of digital filter. Give digital filter same amplitude superposed sine signal, then observe the waveform of the output of digital filter. Verify the function of digital filter by comparing the spectrum of input data and output data., prove that the digital filter has 43 adjustable channels in 5kHz,50 kHz,100kHz,200 kHz,1MHz,2MkHz bandwidth and its passband ripple less than 0.05 dB and its stopband attenuation greater than 55 dB. At last, use Global Foundry 0.18?m library to synthesize, place and route the filter, and use the methods above to reduce 30% area of digital filter.