Design & Size Reduction analysis of Microstrip Hairpin Bandpass Filters

Abstract: This thesis presents Design, Measurement and analysis for size reduction of the Coupled line micro strip Hairpin band pass filters (MHBPF’s). Hairpin filters are an interesting topic for microwave designers. These planar circuits are widely used in wireless transceivers and other microwave projects due to an easy design process. The filter design and analysis described in this paper can be used for wireless transceivers as well as for microwave links. Two techniques have been employed for the size reduction and four different filters have been designed. 1st Technique, Conventional Hairpin configuration uses folding of the normal λ/2 resonators into U shape. 2nd technique exploits the cross coupling of the resonators for further size reduction of the filters.  From 1st to last design, different properties of micro strip and couple lines have been analyzed, observed, and finally exploited to reach to a more compact solution. Agilent ADS have been used for the simulation process of the initial filters. Further on, AWR Microwave office has been used for the EM simulation part of the project and a detailed analysis for the size reduction with respect to the different properties of the materials used. Since insertion loss method is going to be used for the designs, low pass filter prototypes parameters are used for further conversion to band pass. The loaded Q factor and the mix coupling coefficients between resonators have been calculated from standard empirical equations. FR4 substrate is used for manufacturing process. RogersRO3210 has also been used as a substrate for 3-section design in AWR Microwave Office for the illustration of size reduction with respect to substrate properties. The design with FR4 substrate has been manufactured and tested. The results have been analyzed on Vector Network Analyzer and displayed in results sections.