Antenna for harvesting RF energy and method of designing an antenna

摘要

A radio frequency (RF) apparatus 1, suitable for energy harvesting, comprises an antenna 3 on a substrate 9 where the antenna 3 comprises a first intermittent loop 5 of conductive material and gaps and a second loop 7 of conductive material which is located within the first intermittent loop 5 and where there are a plurality of conductive bridges 25 linking the first intermittent loop 5 and the second loop 7. The conductive material may be in the form of conductive track portions. The location of the conductive bridges 23, 25 and/or gaps 11 21 may be selected to reduce spatial variations in the H-field within the area surrounded by the second loop 7. The first and second loops 5, 7 may be tuned to first and second respective frequencies. The size of the gaps may be selected to reduce the spatial variations in the H-field and/or E-field within the second loop 7. The second loop 7 may also be intermittent including conductive material and gaps 27. A rectifier may be located on the substrate 9 within the second loop 7. Also disclosed is an antenna comprising two concentric loops of conductive material, both arranged between the feed points of a common feed signal arrangement.