Fully Reconfigurable Bandpass Filter with Coupling Resonators and Arbitrary Transmission Zero Position

In this paper, a fully reconfigurable bandpass filter in the X-band is presented. The bandwidth is continuously tunable in the range of 30 MHz to 100 MHz and the center frequency can be changed between 8.3 GHz and 10 GHz, which results in a center frequency tunability of 17%. The filter utilizes additional resonators which operate below the X-band to enable the tunability of the inter-resonator couplings. The filter is able to provide a 20 dB return loss over the whole tuning range. A tunable transmission zero is introduced to increase the selectivity of the filter. The position of the transmission zero can be changed freely and moved above or below the passband without decreasing the filter performance.