On the Design of Compact Dual Mode Multi-Band Bandpass Filters using Triangular, Circular and Hexagonal Shape Open – Loop Resonators

The design and performance of a band pass filter for UWB communications is presented in this paper. Open loop resonators consisting of parallel arms (stubs) protruding from a 50Ω transmission line create the required rejection bands. The arms height, width and spacing control the bandwidth achieved by the filter. Each pair of arm creates one reject band in the transmission response. Three filters; one with hexagonal shape arms, another with circular shape arms and still another with triangular shape arms are proposed. The triangular shape offers wider pass band along with a narrow stop band response whereas the hexagonal shape exhibits wider stop band and a narrow band pass response. The achieved pass band (experimentally measured) for the filter with triangular arm resonator is from DC to 3.585 GHz, 5.12 GHz to 6.65 GHz and from 7.81 GHz to 8.86 GHz. The corresponding stop bands are from 3.585 5.12 GHz, 6.65-7.81 GHz and 8.86 – 10.0 GHz. The filters are expected to be useful in communication devices operating in the UWB frequency range.