A compact wide stop band bandpass filter with loaded feeding structure

This paper presents a compact wide stop band bandpass filter using loaded feeding structure to enhance the out-of-band performance. The filter is constructed by three shorted parallel coupled stepped impendence resonators(SIRs), and is fed by tapping microstrip lines with open stubs loaded. The three order bandpass filter effectively suppresses the spurious pass band so that it has a so wide stop band. Measured results accord well with the simulated results, showing good performance of the filter.