Research And Design Of High Linear And Broadband Gm-C Band-pass Filter Used In The RF Receiver

The band pass filter is the key to the RF receiver module of beidou communication system,plays a role of selectting frequency and filtering noise and anti aliasing interference.Receiver need to accurately and undistorted disposal and transmit signal in working condition,and high-performance RF receiver requires bandpass filter with high linearity,wide bandwidth,low noise coefficient and low power.This paper probes into the structure type of the filter and related design method,determines the implementation scheme of the band pass filter;Design a type of cascade biquad Gm-C band-pass filter with high linearity,broadband,low noise and low power consumption as the goal and specific circuit structure is presented;The op-amp,common-mode feedback circuit and reference circuit of bandpass filter is seriously studied and is respectively implemented by rail-to-rail and cross-coupling linear combination structure,unity gain buffer structure and current-mode feedback structure,then further solves the problem of lack of linear and output transconductance change of Gm-C filter,improves and optimizes performance of the designed Gm-C band-pass filter.The circuit of the filter is simulated basing on CSMC 0.25um BCD process library and using Cadence Spectre,the simulation results as follows:center frequency of the filter of 46MHz,bandwidth of 25MHz,-10db rectangular coefficient of 1.11,1dB linear compression points of 22.25dBm,noise factor of 24.3nV/(Hz)0.5 and power consumption of 5.85 mW,the results show that the designed band-pass filter conform to application requirements of RF receiver.