Microwave Tunable Notch Filter Based on Liquid Crystal Using Spiral Spurline Technology

Abstract

ABSTRACT In this article, the design, fabrication, and characterization of a tunable microwave notch filter based on liquid crystal (LC) using inverted‐microstrip technology is presented. A spiral spurline structure is used because of its good performance as a single‐resonator notch filter. Based on the LC dielectric anisotropy, a voltage‐controlled rejection frequency of the filter is achieved, ranging from 3.40 to 3.75 GHz, which means that the tuning range relative to the central rejection frequency is about 10%. At the same time, this device exhibits negative group delay around the rejection frequency and the measured values throughout the tuning frequency range are presented. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2420–2423, 2013