Design of Bandpass Filter with Transmission Zeros Using Zeroth-order Resonator and U-shaped Resonator

In this article, a novel bandpass filter using symmetrical composite right/left-handed transmission lines (CRLH TL) ZOR and U-shaped resonator with three transmission zeros (TZs) is proposed. The design concept of the proposed filter is based on the zeroth-order resonator (ZOR) and half-wavelength open-ended resonator with opposite phase response around the resonant frequency and, therefore, one TZ can be achieved by using a ZOR parallel-coupled with a conventional resonant circuit. To improve the selectivity, two L-shaped coupling arms connected to feed lines are introduced to provide additional two TZs. Both simulated and measured results have been presented to demonstrate the presence of one TZ on high side of the stopband and two TZs on low side of stopband.