Advanced Substrate Integrated Waveguide Components

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The principal objective of this research program is to elevate Substrate Integrated Waveguide (SIW) technology to a state in which it provides a complete, technically feasible and low-cost solution to current and future wireless millimetre-wave systems and networks. That includes the capability of low-loss filter, diplexer and antenna components as well as the integration of active, nonlinear and surface-mount devices. Emerging and future ubiquitous broadband networks, as well as medical, automotive, ultra-wideband and radio astronomy applications, will require a significant increase in the number of wireless devices. As data rate demand increases bandwidth requirements, the frequency of operation is increasing into the millimeter-wave range. For such applications, it is of paramount importance to develop planar technologies that can provide straightforward and highly integrated system approaches including antennas. SIW technology fits this profile. It features a reasonable compromise between microstrip and metal waveguide circuitry, and has been demonstrated to be applicable for broadband passive components up to 180 GHz. However, SIW technology is still experiencing two fundamental bottlenecks: first, for filter and multiplexer applications, its Q factor is not compatible with that of metal waveguide; secondly, the integration of active components can be considered to be still in its infancy. Measured SIW filters demonstrate Q factors of about 500. Such values are acceptable for broadband millimeter-wave components but not for narrowband filters and multiplexers. The increased loss compared to all-metal waveguide (Q factors of several thousands) is attributed to the dielectric loss of the substrate and the metallization of via holes. In order to reduce losses, we propose the introduction of Surface Mounted Waveguide (SMW) technology which consists of small air-filled cavities mounted on top of the SIW printed-circuit board. Special SIW-to-SMW transitions will allow entire filter components to use air-filled configurations or individual resonators to be connected to SIW via extracted-pole filter techniques. Our initial investigations have shown that SMW circuits can increase the Q factor by a factor of three to four and thus will make SIW-SMW technology more competitive to all-metal waveguide and more amenable to printed-circuit board fabrication.Integration of SIW technology with nonlinear devices has caught on slowly. Only recently have varactor and PIN diodes been used to switch and tune SIW filters or Schottky diodes to develop SIW mixers. Amplifiers have mostly been used in circuits that are physically separated from the SIW antenna and/or filter components. Therefore, this projects aims at integration of nonlinear devices in SIW technology for the development of SIW components such as amplifiers, mixers, attenuators, variable phase shifters, limiters and automatic gain control circuits. Integration with SIW-based printed-circuit antennas, couplers and limiters is anticipated. Recently, our team developed a number of interconnects form SIW to planar transmission-line technologies such as coplanar waveguide (CPW), coplanar stripline (CPS) and slotline. They are specifically amenable to surface-mount component integration and dense packaging, thus providing the necessary prerequisites for a successful completion of nonlinear device integrations.Prototype fabrication of the SIW printed-circuit boards will be facilitated by one of our Canadian manufactures; surface-mount component integration will be carried out at the University of Victoria.