Reconfigurable Patch Filter for Mobile Radio and WiFi Applications

Abstract

Modern wireless communication systems usually require frequency agility. A reconfigurable filter is therefor of highly interest in a lot of considerable researches. The limitations are either the size is cumbersome or the selectivity of filters is reduced. This finial year project presents a method to realize the concept of frequency agility on patch-type filter. It has more applications because of its simple structure especially at higher frequencies. The structure is composed of four squares connected together in two by two matrix on the upper patch. Perturbation of degenerate modes is achieved by using slightly different dimension for adjacent squares and same dimension for diagonal squares. A patterned ground plane was used for size reduction of patch-type filters making them more favorable at lower frequencies. Tunable capacitors are applied to the patterned ground plane to achieve frequency agility. For demonstration, three reconfigurable patch filters using varactor diodes with patterned ground plane are designed to operate from 0.8 to 1.0, 1.8 to 2.5 and 5.5 to 5.8 GHz. The experimental results are demonstrated and discussed.