Design automation of a lossless multiport network and its application to image filtering

Abstract

The paper presents expert tools which are elaborated on the basis of synthesis method of lossless nonreciprocal multiport circuits, composed of gyrators and capacitors. The algorithms are written in C++ and the tools compose a user friendly environment for design automation of filters, filter pairs and filter banks. It is possible to design in this environment not only classical structures like Butterworth, Chebyshev, and Cauer (elliptic) filters. The lossless nonreciprocal prototype circuit allows to design more complex filters, including allpass sections necessary to improve filter phase characteristics. However, the most important possibility is to design multiport circuits, especially in the case of not fully determined filter specifications. On each stage of the design process VHDL-AMS is used to describe the circuits. The obtained prototype gyrator-capacitor circuit can be implemented in OTA-C, SC (switched-capacitor) or SI (switched-current) techniques to realize the filter in CMOS technology. In the paper SI technique is used for layout generation of an image filter in order to illustrate the elaborated synthesis algorithms and tools.