Design of tunable edge-coupled microstrip bandpass filters.

摘要

This thesis is a study of tunability of edge-coupled filters. Microstrip edge-coupled bandpass filters are planar structures and have advantages such as easy design procedures and simple integration into circuits.;Three tuning techniques were implemented. The first technique involved the loading of one open end of each coupled into tunable capacitors. The second technique used a tunable resonator in series with the edge-coupled blocks. The final design made use of tunable feedback sections.;A detailed mathematical analysis of each design was performed. MATLAB code based on the analyses was written. The MATLAB simulations were compared to Agilent Advanced Design System (ADS) simulations in order to find the minimum design parameters required to arrive at an approximate solution. ADS simulations were used to accurately determine the final design.;The tunable filters with a series capacitor and feedback were fabricated on RO4003C boards from Roger's Corporation, having a dielectric constant of 3.55. The built boards were then tested with the HP 8510c network analyzer. The measured results were compared to the ADS simulations.;The filter with a tuning capacitor in series with the coupled sections had high insertion loss of -20 dB and tuning range in terms of KHz. The design involving feedback had advantages over the previous design since the insertion loss was better than -14 dB and it had a tuning range of 91 MHz. It was observed from simulations that the design had an adjustable tunability range and bandwidth as the width was varied.