Design and Simulation of a Novel UWB Bandpass Filter with Compact Size, Wide Upper Stopband and Four Mode-Resonances in Passband

In this paper, a novel microstrip-line Ultra Wide Band (UWB) band-pass filter using two symmetric Multi – Mode Resonators (MMR) loaded with step impedance stub, is designed, analyzed and simulated. The proposed MMR, comprised of triple – mode step impedance resontor, to reduce dimension of filter is folded, and one step impedance stub is located on center of two MMRs. With adding the step impedance stub and appropriate adjusting of it's parameters, one can stablish another mode resonace in the desirable passband, i.e, 3.1 GHz – 10.6 GHz. So, optained good performance of filter, such as: coupling increased well, passbanad became flat as much as possible and stopband became very vast. Finally, using of defected ground structure, increased the coupling between MMRs and feeding lines. The proposed filter to compare with conventional UWB filters has a compact size (is about 16mm×6.7mm), wide upper stopband(up to 20GHz), good performance in passband and high selectivity.