52  Reconfigurable Antennas

Obviously, much more work needs to be done to form links between antenna functionality and system performance so that, eventually, particular reconfigurable antenna features will be specified to address known limitations or predicted operating scenarios. These links will also form the basis of new feedback hardware and processing that use information collected about the data, channel, or environment to select the best configuration for the antenna. This research also offers significant opportunities for collaboration with other engineers involved in the design of the necessary hardware, signal processing, and control algorithms that are necessary to take full advantage of antenna reconfigurability.

9.2ECONOMIC VIABILITY OF RECONFIGURABILITY

Second, no clear cost/benefit methodology exists to assess the affordability and viability of reconfigurable antennas for new systems. Although reconfigurable antennas deliver expanded functionality over fixed antennas, they typically require extra parts, extra control lines, and extra infrastructure at one level or another. Antennas with all of these additional parts and connections are more expensive than fixed antennas. Without a clear cost/benefit analysis methodology in place, all of these “extras” may preclude inclusion of a reconfigurable antenna in a system simply because of budgetary constraints. In addition to making the case for a performance/cost trade-off, advances can be made in fabrication and system implementation that will make reconfigurable antennas more affordable in the future. One example of an approach that would result in more economical reconfigurable antennas is the direct integration of switches and associated control lines during antenna fabrication. Several research groups have started along this path, but significant fabrication and design challenges remain, including development of fabrication processes that can deliver high–aspect ratio structures as well as development of new reconfiguration mechanisms that are both compatible with antenna structures and capable of efficient and reliable operation.

9.3EXPANDED DESIGN METHODOLOGIES

Third, other than in the most fundamental designs, there are few design guidelines or theories of operation for reconfigurable antennas that allow engineers to design their own antennas using the same principles. This means, in effect, that existing reconfigurable antennas are waiting for a suitable application to come along, rather than having applications dictate antenna functionality. Admittedly, the goal of being able to exactly specify and then deliver reconfigurability is an ambitious one. However, this goal is necessary to push the required technological and theoretical understanding of these structures to a point where many more reconfigurable antennas can be included in complex, multifunction systems. Certainly, with the expanding demands on wireless systems, we can look forward to new specifications for antenna functionality at multiple frequencies with varying bandwidth, polarization, and radiation characteristics.

Conclusions and Directions for Future Work  53

9.4NEW TECHNOLOGIES FOR RECONFIGURABILITY IN EMERGING APPLICATIONS

As new technologies are developed and mature, antenna engineers will work to include them in new designs. It is hoped that the needs of reconfigurable antennas can also spur development in several areas. Certainly, the maturation and validation of RF-MEMS technology is being pushed to a certain degree by demands for low-cost, high-reliability reconfigurable circuits and antennas. Additionally, pursuit of new and novel tunable materials with improved loss and bias characteristics will make reconfiguration more practical and cost-effective. Finally, the development of new kinds of mechanical actuators and electronic tuning methods can result in reconfigurable antennas with an even broader range of capabilities than those discussed here. With imagination, ingenuity, and enterprise, reconfigurable antennas can lead the way to new levels of wireless system performance.

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