Reconfigurable bandpass filter topology using cul-de-sac resonators with adjustable notches

In this paper, we present a fully reconfigurable bandpass filter structure capable of controlling the center frequency, bandwidth, and notches in the stopband. For the design purpose, we also present a filter topology containing frequency-tunable dangling resonators. The filter has a multi-layer structure having both microstrip-line resonators and substrate-integrated waveguide (SIW) resonators. For achieving high-rejection notches, the filter has been designed in such a way that the notches and passband are produced by SIW resonators and microstrip-line resonators, respectively. Measurement shows that the center frequency can be tuned from 1 GHz to 1.4 GHz and the bandwidth has the tuning range from 100 MHz to 150 MHz. In addition, two notches can be controlled independently with maximum 87 dB attenuation.