Cross-Coupled Microstrip Bandpass Filters With Finite Frequency Transmission Zeros

This paper presents four-pole and six-pole cross-coupled microstrip bandpass filters. Each filter consists of tapped input/output feed lines and square open-loop microstrip resonators. A pair of transmission zeros is obtained by coupling of apart resonators. The presence of these transmission zeros highly improves the selectivity of the filters. The proposed filters are designed to operate at 2.0GHz with a fractional bandwidth of 0.05. The lower transmission zeros are at 1.93 and 1.94GHz whilst the upper transmission zeros are at 2.16 and 2.06GHz for the four-pole and six-pole filters respectively. The proposed filters are simulated using CST and AWR microwave Office CAD tools. The simulated results, which are based on different techniques, are in a good agreement.