Bandpass/bandstop switching with tunable pass band operation based on split ring and open loop resonators

Abstract

In this work, a bandpass filter (BPF) using a split ring and open-loop resonators for wireless applications is discussed. The split-ring resonator (SRR) is the main part of the band stop filter (BSF) as a preliminary design for obtaining a band stop behavior. The proposed filter is printed on a RO4003 substrate with a 3.55 dielectric constant and a total size of 30 × 30 × 0.813 mm3. First, the SRR BSF is presented to operate at a center frequency of 5 GHz then an open loop resonator is added between input/output ports to achieve an extra band stop region to generate a bandpass behaviour between the two stopbands at 3.5 GHz. The PIN diodes are used to switch between the bandstop and bandpass operation. Then, two varactor diodes are embedded in the open-loop resonator to control the bandpass and bandstop regions of the suggested filter. The experimental results validate the simulated ones confirming the suitability of the suggested filter for proper operations in different wireless applications.