Design of a Switchable Microstrip Bandpass Filter with Single- and Dual-Band Functionality

A novel design for a planar microstrip bandpass filter with reconfigurable single and dual-band functionality has been developed. The filter achieves this flexibility by Incorporating switchable grounded ports strategically placed on the input and output coupled lines. Moreover, an auxiliary half-wavelength open stub circuit Integrated into the middle of the coupled lines enhances filter selectivity by providing high attenuation in both the lower and higher stopbands. To demonstrate the concept, a sample switchable bandpass filter was designed. The filter operates at a central frequency of 3.5 GHz in single-band mode, and when switched to dual-band mode, it achieves center frequencies of 2.9 GHz and 4.1 GHz.