Switchable Microstrip Bandpass-Stopband Filter Based on Periodically Loaded Transmission Lines

This paper presents the design of a microstrip switchable band pass-stopband filter based on periodically loaded transmission lines. The proposed design, takes advantage of the structure symmetry of the left handed periodically loaded based filter and the extra degrees of freedom introduced by the metamaterial structure to switch between stop-band and bandpass behavior. It is shown that the relations between the device physical dimensions and the pass/rejection band bandwidth and central operating frequency, can be controlled through analytical expressions. As illustrative example, a switchable pass/stop band with the same bandwidth and central frequency is presented, showing a good agreement between measurement, simulation and theoretical predictions.