Compact tri to dual passband switchable bandpass filter using stub-loaded split-ring resonator with improved bandwidth

Stub-loaded split-ring resonators (SRRs) are presented for the design of a compact tri- to dual-band bandpass filter (BPF). The length of the two concentric split-rings having splits on the opposite sides, the gap between the two concentric split-rings and the length of the stub determine the positions of the three passbands. Switchability has been achieved by controlling the closing and opening of the inner ring of the SRRs using pin diodes. The responses of the BPF depend upon the condition of the switch. Moreover, lumped coupling capacitors are connected between the two SRRs to enhance the bandwidths of the passbands of the BPF. It also permit a greater coupling-gap between the SRRs which further reduces the challenges of fabrication.