Ultra-wideband bandpass filter using hybrid microstrip/ACPW structures

A novel ultra-wideband (UWB) bandpass filter with hybrid microstrip and asymmetric coplanar waveguide (ACPW) structure is proposed. The filter is realized by coupling between an ACPW quarter-wavelength resonator and two microstrip open-circuited stubs. Parameters of the design were obtained by electromagnetic (EM) simulation and optimization. From the simulation results, it can be shown that the passband frequency range (-3dB bandwidth) is from 3.1GHz to 10.6 GHz, which satisfies to the range allocated to UWB system by FCC. Moreover, the filter can exhibit a better performance at upper stopband from 12GHz to 19GHz with |S21| less than -10dB. The size of the proposed filter is around 0.25×0.25 wavelength of center frequency, which is relatively small.