소형화를 위한 개선된 컴라인 필터

Abstract

Bandpass filters are widely used in microwave systems. And miniaturized bandpass filters are required to reduce the cost of a wireless communication system. Therefore, many prototypes have been studied to meet this requirement. The conventional comb-line filter is one of the so many types of proposed size-reduced filters. In this thesis, we propose a modified comb-line filter using a combination of end shorted parallel coupled lines and lumped capacitors. Using the above structure, the electrical length of the parallel coupled lines in the modified comb-line filter, which determines the size of a comb-line filter, can be reduced to even a few degrees, resulting in a much smaller circuit area. Inter-stage connecting lines have been added to connect the neighboring resonators for the suppression of unwanted coupling. The designed comb-line filter also shows a wide upper stopband. Design equations and method will be fully explained in this thesis. Measured results of a fabricated filter centered at 400 MHz show good agreement with the theoretical predications.