Frequency Variations Improvement of a Bandwidth and Central Frequency Reconfigurable DBR Filter

This paper deals with the design and frequency variations improvement of a switchable narrow bandpass planar filter. A first filter, based on the DBR topology (dual-behavior resonator), is studied. It allows one to get the central frequency and bandwidth given in two or more specifications. Nevertheless, for far frequency variations, the impossibility to keep a correct matching level for the two bands makes necessary the use of a matching network. This can be done by introducing reconfigurable low-pass structures in the initial switchable filter. Moreover, such low-pass elements enable to soften the first high-frequency spurious resonance