An extended stopband bandpass filter with unequal length open stubs loaded

In this paper, a wide stopband bandpass filter was proposed. The proposed filter is composed of microstrip stepped impedance resonators (SIRs), two open stubs of different lengths are loaded at the center of some of the resonators to suppress the harmonic frequencies, thus makes the filter have a so wide stopband. Measured results accord well with simulated results, showing good performance of the filter.