SYSCUF: automated synthesis of switched current filter

This paper presents a software package for the automatic synthesis of switched current (SI) filters, called SYSCUF (SYnthesis of Switched CUrrent Filter). Switched current is a new analog sampled data signal processing technique, which can be implemented without the need of a floating capacitor. High package density and high speed of the switched current circuit makes the technique suitable for mixed analog/digital integrated circuits. In SYSCUF a universal switched current integrator (integrator biquad) has been considered as basic building block. SYSCUF deals with the cascade structure of integrator biquads for higher order filter synthesis. Four types of approximation functions, which have been considered in SYSCUF, are Butterworth, Chebyshev, Inverse Chebyshev and Elliptic. Several examples with different types of filters with different approximation functions, designed by SYSCUF are simulated using PSpice. The results are quite satisfactory. A graphical view of the filter menu, approximation menu, transfer function, block diagram and final circuit diagram are quite helpful for practical filter designers.