Recursive Filters Employing Transmission Type Phase Shifters and Novel Self-Switched Time Shifters for Frequency Tuning

In this paper we discuss tuning properties of recursive active filters. Two different types of tuneable microwave monolithic integrated (MMIC) filters working at X-band have been implemented for evaluation. The first filter type uses an analog transmission-type phase shifter as tuning element resulting in a tuneable bandwidth of 9% and an instantaneous filter bandwidth of only 1.2%. The second filter which instead uses a novel small size three-bit self-switched time shifter has a tuneable bandwidth as large as 16% and an instantaneous bandwidth of 5%.