Design of Novel Millimeter-Wave Wideband Bandpass Filter Based on Three-Line Microstrip Structure

A novel three-line microstrip structure wideband bandpass filter is presented. Diamond structures of input/output ports are employed as matching circuits. Compared with the traditional three-line filter, the proposed three-line filter not only retains virtues of the traditional three-line filter, but also resolves drawbacks of it, which include discontinuities between adjacent sections, number of design parameters, and no effective matching circuits at input/output ports. To validate the proposed three-line filter, an eleven-pole millimeter-wave wideband bandpass filter is designed and fabricated. Good agreement between simulated and measured responses is observed.