A linear group delay filter with tunable positive slope for analog signal processing

Abstract

International audienceThis article describes the design of a tunable positive slope linear group delay filter dedicated to analog signal processing applications. The designed filter is composed of eight second-order all-pass cells which have been optimized to obtain a highly linear global group delay characteristic over a specified bandwidth for a specified dispersion. Each of these second-order cell is designed with a dedicated − topology to fit the ideal group delay characteristic with a high efficiency. Based on the sensitivity analysis of the topology the possibility of tuning the group delay slope is highlighted. The design is achieved at transistor level with the ST CMOS 55nm technology and has a maximum bandwidth of 3 GHz, a maximum reachable delay of 4.45 ns, and a group delay swing of 3 ns. The positive slope of the group delay can be tuned in the range from 1.2 ns/GHz up to 1.4 ns/GHz