New ultra-wideband (UWB) bandpass filter using triangle-ring multi-mode stub-loaded resonator

This paper presents a new ultra-wideband (UWB) bandpass filter (BPF) with steeply slopes transition band using triangle-ring multi-mode stub-loaded resonator (MM-SLR). The filter consists of a triangle ring multi-mode resonator with a stub-loaded resonator for controlling the two transmission zeros at 2.8/ 11 GHz and the asymmetric tight coupled input/output (I/O) lines. There are five resonant modes generated in the UWB passband including two odd modes and three even modes. The two transmission zeros generated by the triangle-ring MM-SLR can effectively improve the passband edge selectivity. The attenuation slope in the lower and higher passband edges of the proposed filter show 160 and 153 dB/GHz, respectively. Experimental verification is provided and good agreement has been found between simulation and measurement.