Multiple-probe dielectric resonator antennas for asset tracking applications
Simon P. Kingsley · 2000
Dielectric resonator antennas (DRAs) are volumetric devices that can be more efficient than conventional antennas at high frequencies and smaller by approximately the square root of the relative permittivity of the material. Research at Sheffield and Griffith universities has shown that by using several feeds they can be designed to be directional with electronic beam steering. DRAs can also have radio direction finding capabilities by comparing the same signal in two beams or by using monopulse processing. The ability to locate a radio source and form an optimal beam in that direction, combined with nulls that can sometimes be used to cancel out unwanted signals, may give these antennas a limited adaptive or `smart' capability. Optimal beam configuration can also help to extend battery life, which may be important when the asset is not easily recovered, as is the case in some biotelemetry applications. The presentation will describe a number of multi-probe, multi-beam DRAs designed for use on both tags and short-range communications, such as Bluetooth, and for radio direction finding applications such as tag tracking and microbase-stations. A typical 870 MHz multi-beam 360° direction finding DRA system is 32 mm across and 13 mm high using an ɛr of 80 and smaller for higher ɛr materials. The construction of these antennas lend themselves to integration into the manufacture of the communications circuits, thus reducing cost when appropriately designed these antennas are considered to provide better performance than conventional antennas when operating in close proximity to conductive structures. (4 pages)