A Novel Reconfigurable Multifunctional Integrated Filter With Simultaneously Tunable Frequency, Bandwidth and Attenuation

In this letter, a novel reconfigurable filter with multifunction of continuous tunable frequency, bandwidth (BW), and attenuation is proposed. The tunable filter is integrated designed based on a fully tunable filtering coupling structure with external quality factor (Q e ) control and a tunable attenuation unit with impedance transformation capability. The fully tunable filtering coupling structure is deigned using terminal varactor loaded half‐wavelength microstrip resonator with tunable center frequency and coupling coefficient. Adjustment of Q e is realized through the addition of a varactor at the feedline port. Tunable attenuation is achieved by loading PIN diodes through a coupling structure. To improve the efficiency of impedance transformation, an asymmetric structure is employed. The performance degradation of the bandwidth and center frequency due to the tunable attenuation can be compensated by the fully tunable filtering coupling structure. The measurements show that the reconfigurable filter can be tuned from 0.99 to 1.61 GHz with tunable attenuation and bandwidth. The attenuation can be tuned over a range of 30.6 dB at 1.4 GHz, and the fractional bandwidth (FBW) can be tuned from 10% to 30% at 1.3 GHz.