Developing Low-Cost $W$ -Band SIW Bandpass Filters Using the Commercially Available Printed-Circuit-Board Technology

In this paper, high-performance W -band substrate integrated waveguide (SIW) filters have been investigated by using the low-cost printed-circuit-board (PCB) technology. Two types of SIW bandpass filters including cascaded quadruplet (CQ) and cascaded triplet (CT) filters were studied. The coupling matrix theory has been used to synthesize initial geometries, and the aggressive space mapping (ASM) algorithm was adopted as fast and low computation cost optimization method for realizations of investigated filters. A fin-line SIW-WR10 waveguide transition was developed for experiments. As demonstrations, two W -band prototypes having a 2.5% fractional bandwidth centered at 80 GHz were fabricated on a 0.508-mm-thick RO5880 substrate and measured by a vector network analyzer. Good agreement between simulated and measured results is obtained. This work demonstrates that high-performance W -band planar filters can be realized by utilizing the low-cost commercial PCB technology, and some design rules are recommended.