Switched-current filters and group delay equalizers using wave synthesis technique

This thesis is concerned with the design, analysis and realization of analogue filters and group delay equalizers using switched-current (SI) technology. A key feature of the described design methods is the employment of wave synthesis technique enabling advantages, such as simple circuit implementation and low sensitivity. Despite their simplicity, SI circuits suffer from some fundamental sources of errors, which produce deviations in their performance. The thesis presents a detailed analysis of the non-ideal performance of the recently reported Bruton transformation SI filters and show how the frequency response of such filters are affected by mismatch and clock-feedthrough errors. To carry out such a detailed investigation, behavioural models of the filter main building blocks have been developed based on their physical implementation and incorporated with MATLAB. To improve elliptic filters time-domain response, group delay equalizers are often cascaded with the filters. This thesis describes a systematic design for SI group delay equalizers based on the wave synthesis technique including the development of new group delay equalizer architecture. Using computer program based on the presented design method and architecture, together with an optimisation technique, a number of equalizers have been designed and they are capable of improving the filters step response. To analyse the practical performance of SI wave filter and group delay equalizers, transistor-level circuits using standard 1.2 μm CMOS process are designed. Simulations show the performances of SI wave filters and group delay equalizers agree well with the theoretical predictions. Finally, new adaptive analogue filters with modified wave structure and adaptive algorithm are developed. It is shown that such filters offer a number of advantages including low sensitivity, simple adaptation process and easy stability checks. Furthermore, an efficient hardware implementation of analogue adaptive wave filters using SI technology is outlined.