Design Of High Band-Pass Switched-Capacitors Filter For DTMF Signals Receiver

Firstly, this thesis introduces the development of switched capacitor filters and basic principles of normal filters. In the first part, this thesis emphasizes to introduce the approximation functions and inducement of three filters. Also this thesis introduces the reason of choosing the cauer approximation.The DTMF signal is a new method in the data transferring system that emergences in recent years. This thesis introduces the history and development of the DTMF signal and a DTMF receiving system's working diagram.There are two methods to realize the function of the switched capacitor filter: dual-two order method and Z-domain method. This thesis emphasizes to introduce the two methods and realize the functions with the two methods. In the switched capacitor filter circuit, the properties of the operational amplifier influences the whole circuit severely, so this thesis introduce a typical operational amplifier that has two orders and tests the main properties of it. At last, this thesis tests the properties of the whole circuit system with the library of Csmc60 and compares the results of the two methods. Also thesis gives a code that can optimize the parameter of the switched capacitor filter when using the Z-domain method.