Antenna analysis, design and measurement techniques

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Antennas are required in everything that involves wireless communications and are key to the quality of any wireless link. The move is towards the provision of diverse services that require higher data rates and hence wireless channels with larger bandwidth. This demand for bandwidth is leading to saturation of the available frequency spectrum. So multiple-input/multiple-output (MIMO) and/or cognitive radio techniques are being studied as ways to improve capacity in future wireless networks through improved utilization of the electromagnetic spectrum. All these developments require antennas with greatly improved functionality. It is estimated that in the future mobile terminals will need to have more than twenty antennas. Yet the desire for sleeker wireless handsets with larger screens and batteries has meant that there is less space for the antennas. So antenna design methods cannot be cut-and-try. Whereas antennas for mobile handsets have wide beams, those for wireless base-stations, automotive radar, imaging systems, and satellite communications need narrow beams. In order to achieve their required performance and yet be inexpensive, such antennas must use printed circuit technology. One way to handle increased data rates is to use higher operating frequencies, but at these so-called millimetrewave frequencies conventional narrow-beam (or stated equivalently, high gain) antennas made using printed technology become inefficient. It is not feasible to simply scale antennas already in use at much lower frequencies. Alternative configurations must be sought. These alternatives, such as printed lens antennas, reflectarray antennas and holographic antennas are potential solutions to the problem, but have issues that need to be resolved. In some cases the only solution to the demand for a single antenna to handle many different tasks is for it to be reconfigurable. For example, if its operating frequency can be altered electronically it can be used for more than one application (on the same device) as needed. Or it could be that an antenna is able to alter its beam shape or direction. This proposal is concerned with the development of new antenna configurations capable of satisfying the above tougher requirements and constraints.