Reconfigurable lowpass filter based on signal interference techniques

This paper presents a novel reconfigurable filtering block based on signal interference techniques. The topology consists of the connection in parallel of three transmission lines of different electrical lengths. The lines can be switched on/off through the use of p-i-n diodes. In this way, the signal paths and their interferences are controlled providing different states (different cutoff frequencies). The proposed filter is easy to design and fabricate. As demonstration, a reconfigurable microstrip lowpass filter with three states (2.0, 3.0 and 4.0 GHz) is designed and implemented. The three states present selective responses with good rejection levels.