Design of tunable microwave filter using dual mode resonator two pole bandpass filter

Abstract

Filters are useful components in electronic design. They are required in any communication systems for frequency selection. They allow certain frequencies to pass and reject unwanted frequencies. Microwave signals require special circuits and transmission lines and therefore the design of microwave filters are complex. Modern communication systems require operation in more than one frequency band therefore the microwave filter should be able to operate with more than one center frequency. A tunable microwave bandpass filter is implemented using microstrip lines. The filter is designed using multimode resonator (MMR) and coupled line transmission lines. The filter is simulated in ADS 2009 with substrate material being RO4003C whose dielectric constant is 3.365. Centre frequency of the designed filter is tuned with the aid of varactor diodes. In the passband insertion loss of 1.5 dB and return loss of 25 dB was achieved.