A new compact tunable bandpass filter using defected ground structure with active devices

A new tunable bandpass filter using Hairpin-DGS and varactor as active device has been presented. Both, the simulated and the measured results have demonstrate that the proposed passive one pole DGS BPF may be easily transformed to a tunable BPF by adding a simple variable capacitor on the DGS-element. The measured results have shown a good one pole bandpass response with a high quality factor and with a good sharpness in transition range. Additional the proposed BPF is very compact in comparison with the conventional tunable filters. The introduced BPF has been designed to meet the requirements of modern wireless communication systems.