Frequency-reconfigurable microstrip filter with dual-mode resonators using RF PIN diodes and DGS

This work presents a novel frequency miniaturized reconfigurable dual-mode stub-loaded resonator switchable from bandpass filter to single/double-notched bandnotch filter. The proposed filter topology employs RF PIN diodes as the switching device. Based on the odd- and even-mode equivalent circuits, the resonant characteristics of the proposed microstrip resonator are investigated. The defected ground structure pattern enhanced the performance; the 3-dB bandwidth reached 63%, with insertion loss of −0.5 dB. There was great sharpness of 55 dB in the low-frequency edge (from 1.7982 to 1.8466 GHz) and 33 dB in the high-frequency edge (from 3.4329 to 3.4995 GHz). The frequency-reconfigurable microstrip filter has been designed, fabricated, and measured for application in narrow band and ultra-wideband.