A Frequency Tunable Patch Bandpass Filter With Wide Tuning Range

In this paper, a new frequency tunable bandpass filter is implemented using a patch element. The frequency tunability was achieved by simply changing the biasing voltages of the four varactor diodes utilized. Thanks to the high flexibility of the patch element utilized, a wide frequency tunable range can be achieved maintaining the simplicity in structure. To validate the proposed structure, a bandpass filter was designed and fabricated. The circuit was measured to achieve a wide tunable frequency range up to 45%.