Compact wideband bandpass filter with controllable bandwidth and suppression of the second passband using a trimode resonator

Abstract

ABSTRACTThis article presents a wideband bandpass filter with controllable bandwidth and suppression of adjoining second passband, in which four same open loop resonators are adopted, hereinto two resonators located at the middle are integrated into a single trimode resonator using two microstrip lines. One line is applied to adjust desirable passband bandwidth, and the other is used to achieve the suppression of the second passband and obtain a wider stopband. Good return loss and inserted loss are obtained using an optimization routine. This technique has high flexibility on setting bandwidth and suppressing the adjoining second passband. Two prototype filters are designed and fabricated. Good agreements between simulation and measurement are demonstrated. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2939–2943, 2015