Tunable RF Filters for Modern Wireless Systems

Abstract

This thesis is to propose novel generic methodology and design equations to design multi-band bandpass filters. The design procedure utilizes an approach based on asymmetric half-wavelength resonators. The obtained optimized filters by this approach are used as reference designs and proposed technique is applied to calculate the new filter physical parameters that satisfy its given specifications. Dual-band, tri-band and quad-band filters are designed and implemented using this novel transformation technique. This technique is easy, fast, generic and accurate without relying on computer aided design (CAD) optimization. A reference dual-band filter is designed, based on asymmetric half-wavelength resonator, to obtain the following specifications: the insertion loss is better than 1.5 dB and return loss is better than 10 dB, bandwidths, BW1 ≥ 60 MHz and BW2 ≥ 150 MHz at the resonance frequencies, fr1 = 2.1 GHz and fr2 = 5.6 GHz for UMTS / WiMAX applications, respectively. Utilizing this reference filter; two dual-band filters for GPS / WLAN and GPS / WiMAX applications are illustrated to verify the proposed novel generic design equations. The results obtained from measurements agree well with that obtained from simulations, which verifies the proposed method. A reference tri-band filter is designed, based on asymmetric half-wavelength resonator, to obtain the following specifications: the insertion loss is better than 3 dB and return loss is better than 10 dB, at fr1 =1.4 GHz, fr2 = 4 GHz and fr3 = 6.3 GHz for L-Band DAB, Radar (G-band) and Radar (C-band) applications, respectively. In addition, two tri-band filters are designed to verify the proposed novel generic transformation and design equations based on the reference filter. The proposed technique is validated through fabricating one of the designed examples. The results obtained measurements agree well with that obtained from simulations.