Antenna Analysis, Design and Measurement Techniques

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The Canadian wireless industry continues to be innovative at both the system and equipment level. Wireless communications pervades everything, and if anything is wireless (as opposed to wired) antennas are required. The objective of my proposed research is the use of electromagnetic principles for developing tools for the analysis, design and measurement of improved antennas for the many emerging wireless applications. A theme running through the proposal is that of letting the electromagnetics directly guide us as to the antenna element shapes needed to achieve the performance we desire.***Except for those on base-stations, wireless antennas must have broad radiation patterns (low directivity) because of the propagation issues extant in wireless networks. They must fit in the crammed environment of portable devices and so can be difficult to design. This difficulty is increased for the cognitive radio and multiple-input/multiple-output capabilities to be used in future systems to overcome spectrum scarcity, since these antennas will need to be multiband, with several closely-spaced antennas on a single mobile device. New configurations and design methods are needed. We have previously developed a unique class of shape synthesis technique that can be used for the design of single-band varieties of such next-generation antennas, which uses as a starting shape the "leftover space" in a portable wireless device. The goal of one part of the research proposal is to extend the approach to multiband antennas, and configurations of two or more very closely-spaced antennas.*******Fifth-generation wireless systems will use smaller cells that utilize millimetrewave bands (28 GHz to 90 GHz for cellular mobile services) due to bandwidth demand, with the high propagation losses at these frequencies exploited to keep cells from interfering with each other. High-directivity antennas, some needing switchable beams, will be needed. To satisfy aggressive cost constraints the antennas must use printed technology. At millimetrewave frequencies the losses in the beamforming networks of conventional printed arrays are a limiting factor. Transmitarray and planar holographic antennas use printed technology but dispense with the beamforming networks. I will advance my research on transmitarrays by using the shaped fragmented element approach (which we have successfully used in reflectarray work) to design multifocal transmitarrays (enabling switched beams) and multiband transmitarrays (operating at widely separated multiple frequencies). Planar holographic antennas can be made truly low profile (important in commercial applications), with the feed integrated onto the substrates supporting the hologram, but have suffered from low aperture efficiencies. We will use the extended electromagnetic modelling abilities we have developed to synthesize feeding arrangements to improve this aperture efficiency.***