Design Analysis And Implementation Of Tunable Microwave Band Pass Filter

Abstract

Bandpass filters are essential components in electronic design. In microwave applications like satellite communication, Radar and Cellular communication bandpass filters play a crucial role. They attenuate unwanted noise frequencies and pass the desired frequencies without attenuation. With the advent of modern multiservice communication systems, the electronic design demands multiband filters. Multiband filters possess several passbands. This research work proposes wide band tunable bandpass filters with operating range from 1 GHz to 15 GHz and multiband frequency response. Parallel coupled lines are used to realize multiband filters with wide passbands. The frequency responses of the proposed filters are able to be tuned continuously with the help of capacitors and varactor diodes. The proposed coupled line filters has wide passbands and large operating frequency range compared to those in literature. Since parallel coupled lines are easier to fabricate the proposed filters are cost effective and since a single parallel coupled line resonator is used to achieve multiple bands, the proposed filters are also compact in size. T shaped resonators are also investigated in this research since its inherent property of harmonic frequency response helps in multiband filter design. A conventional T shaped resonator is designed, simulated and fabricated which results in triband characteristics. This conventional filter is modified with an additional stub and meandering of stubs. Up to pentaband characteristics are achieved with these modified T shaped resonators. Meandering of stubs resulted in additional passbands making the design compact in size compared to other multiband filters in the literature. The multiple bands of these filters spanned over 1GHz to 10GHz. A superior performance in terms of insertion loss is also achieved. The simulated and measured results are found to be in good agreement. newline