Recent Development in AFSIW Filtering and Passive Components Toward Advanced Systems on Substrates
Introduced in the early 2000s, the substrate integrated waveguide (SIW) technology, has triggered huge interest from academia to industry with the focus on the design and development of low-loss, compact, integrated, self-packaged and low-cost microwave and mm-wave circuits, antennas and systems. However, the classical metallic waveguide technology, which offers better performance such as lower insertion loss and higher power handling, has still been used in the design of microwave and mm-wave systems, despite its higher cost and bulky structure. To offer a highly integrated, further loss-reduced, low-cost alternative to the conventional waveguide and also to allow a wide-spread use of the mm-wave spectrum, a new SIW structure called Air-Filled SIW (AFSIW) has been introduced. This new structure has been theoretically and experimentally studied in detail with substantial results. At mm-wave frequencies, compared to the SIW topologies, the proposed AFSIW scheme exhibits a substantially lower insertion loss (three times at Ka-band, for example) and a much higher average power handling capability (four times, at Ka-band for example). Numerous AFSIW passive components have been investigated, designed and demonstrated, which take advantage of the well-established multilayer printed circuit board (PCB) fabrication process. Couplers, phase shifters, power dividers, antennas and filters have been modeled, designed, prototyped and measured based on the introduced technology. Their performance has theoretically and experimentally been compared with their SIW counterparts to demonstrate and validate the benefits of the proposed technology.