Design And Realization Of Four Channels Programmable Filter

Filter is one of the most popular device in signal processing, which can be worked from signal acquisition to data processing. Band-pass filter and low-pass filter are widely used: Band-pass filter is usually used for checking out fixed signal, while low-pass filter is usually used as an anti-aliasing filter or noise filter in data collecting system to limit high-frequency noise. However, for different applications, the signal acquisition mode and filtering bandwidth requirements are different. For the sake of satisfying most applications,a universal filter was designed, which has fixed amplification and its filtering mode and bandwidth can be programmed and controlled.The filter mainly concludes a front voltage stabilizing circuit,a selection circuit filter,a high-pass filtering circuit, low-pass filter circuit, state variable anti-aliasing filter circuit, the parameter control module and a working state display module. When pre-signals enters into the filter , it firstly needs the voltage processing circuit and then gets into the filter characteristic to select circuit. According to the actual application requirements, select the signal propagation path. If band-pass processing is required, then it goes through high-pass filter circuit and low-pass filter circuit, and if low pass is needed, high-pass filter is skipped,and only goes through the low-pass filter. High-pass filter and low- pass filter are used in transition zone roll off switch capacitor filter, among the high-pass filter is 8th order and and low-pass filter is 10 order. Both of their cut-off frequency can be regulated by the external reference clock. The anti-aliasing filter circuit is used to process the high-frequency noise which is introduced by the front filtering circuit accurately. The parameter control module is mainly used for model configuration, display module is used to display the current working state.This thesis mainly discusses the design and realization of the hardware platform, and to do the whole test of system in the fourth chapter. The test results show that, the filter network has fixed amplification and configuration is simple. In the expected range,bandwidth can be adjusted flexible and it can restrain the outside band signals. All of the indicators have reached the design requirements, and the work is stable and reliable.