| The emergence of DTMF signaling scheme solved much problems of transferring dialing information in the communication system, such as slow, suffering severe distortion, and required a DC path through the communications channel. As one of the most important segments in DTMF communication system, filters take a critical part. Its performance decides whether the receiver can recognize and decode the input DTMF signals accurately or not.Switched-capacitors-filter has the merits of small area, low power-consumption, and easily debugging. Besides, it owns low error, low temperature-coefficient, and stable performance because its RC constant equals the ratio of two capacitors. So it has been used extensively in the field of communication and control. The enhancement of process, the feature size of device becomes smaller, and the deductions of the power supply require the art of design should be consummated.This article firstly makes a detailed analysis and expatiation for the operational principle and design technique of switched-capacitors-filter. Then realize the filter design in biquadratic method and z-domain synthesis. And accomplish the simulation using CSMC 0.6m process, obtaining satisfying results. |
