Six-state reconfigurable filter structure for antenna based systems

This paper demonstrates a six-state reconfigurable band-pass filter intended to add frequency tunability to antenna systems. The present topology produces filter responses with center frequencies of f/sub 0/= 9, 10, and 11 GHz and achieves independent bandwidth control with an average tunable passband ratio of 1.73:1 between the wideband configurations ranging from 13.4% and 14.7% and the narrowband configurations ranging from 7.7% and 8.5%. PIN diodes are implemented as switching elements and the distinct states are discretely accomplished by the connection and isolation of strategically placed transmission line sections. The insertion loss of the filter ranges between 1.74 and 1.92 dB. The circuit produces no significant signal distortion resulting in third-order intermodulation intercept points (IIP3) greater than 48 dBm for tones separated by 1 MHz around the center frequencies.