A Novel Reconfigurable Dual-Mode Microstrip Meander Loop Filter

A novel dual-mode reconfigurable band pass filter is proposed. A meander loop compact structure is used, where its four arms are brought inside the loop. Structure's perturbation is designed by filling the gap between the two arms at the top right corner. The loop is loaded by four varactor diodes connected between each arm and a small square patch located at the centre. Varactors are shorted through a via at the centre of the small square patch to control the centre frequency of the filter. This structure is compact, simple in fabrication, and has a wide tuning range. A tunable bandpass filter is designed and implemented to tune over the range from 1.47 GHz to 2.40 GHz (relative tuneable bandwidth similar to 48%). The fractional bandwidth (FBW) changes from 6.9% at 2.4 GHz to 3.1% at 1.47 GHz.