A New Compact Coupled Circular Ring Band-Pass Filter Structure for ISM Band Application

This work presents a compact bandpass filter BPF designed using coupled circular ring resonators implemented with microstrip technology. The key feature of the proposed design lies in the circular ring resonator, which primarily employs capacitive coupling to achieve resonance. The filter is mounted on an RO4003C substrate with a thickness of 1.52 mm, a dielectric constant of 3.38, and a loss tangent of 0.0027. It operates at a center frequency of 5.72 GHz with a bandwidth of 693 MHz, offering low insertion loss and effective suppression of unwanted signals outside the passband. The filter’s performance was verified through simulations carried out using two distinct electromagnetic solvers. Thanks to its compact structure, flexible design, and outstanding performance, this BPF marks a significant improvement in microwave filter technology and shows great promise for use in next-generation wireless communication systems, wireless power transfer, and 5.8 GHz rectenna arrays for RF energy harvesting.