In this article, a compact ultra-wideband (UWB) band-pass filter (BPF) with wide upper stopband is presented. The filter is designed with a UWB response from 3.2 GHz to 10.8 GHz with low insertion loss of 0.9 dB and less than 0.19 dB at the center frequency (6.67 GHz). The filter is also designed with a broad upper stopband with high rejection level of 20 dB. The group delay is flat with maximum of 0.4 ns. The proposed UWB filter is constructed by using a pair of parallel coupled lines and two ring resonators. In this design, the ring resonators provide two new excited modes to widen the desired UWB passband and also create two tunable transmission zeros to achieve a wide stopband. Good agreement is observed between simulated and measured performances of the UWB filter.
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