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Abstract
Focusing the electromagnetic fields within a lossy half-space is analyzed for a symmetrical annular slotted antenna array. The excitation for focusing the vertical electric field component is specified. Both phase and amplitude compensated focusing results are shown. The focusing is very sharp for high frequency and/or low loss and it deteriorates otherwise. Also, focusing becomes sharper as the number of annular slots is increased. Amplitude compensated focusing is shown to be more tolerant to loss than pure phase focusing. Potential applications are to hyperthermic cancer therapy and to geophysical sub-surface probing.