Reconfigurable-bandwidth bandpass filters based on signal interference techniques

This paper presents two novel reconfigurable building blocks for the design of reconfigurable-bandwidth bandpass filters (BPFs). Both building blocks exploit the signal interference concept. They are arranged as transversal filtering sections loaded with switchable stubs. By switching on/off these stubs through the use of p-i-n diodes, it is possible to control the signal interference paths in the transversal sections in order to achieve different bandwidths in each mode of operation. Two reconfigurable-bandwidth BPFs are developed at 2 GHz in microstrip technology by using the proposed building blocks. Both filters present very wide bandwidth tuning range (e.g.: from 10% to 50% in one of the designs) with sharp-rejection responses in all modes of operation.