Development of compact directional antenna utilising plane of symmetry for wideband brain stroke detection systems

Microwave-based brain stroke detection demands low profile, compact, directive and wideband antennas for efficient imaging using portable systems. Using image theory of electromagnetics, the magnetic symmetry plane of a folded antenna is utilised for its miniaturisation to half of its original volume without sacrificing its penetration capability or radiation directivity. The antenna achieves 63% fractional bandwidth (1.25-2.4 GHz) with 3.5 dBi average gain along the direction of radiation. Both the near-field and far-field radiations are characterised to ensure the antenna´s applicability in the detection system. Moreover, the radiation safety is also analysed since the antenna has to operate in close proximity to the head. The overall dimensions of the proposed antenna are 0.29λ₀ × 0.12λ₀ × 0.06λ₀ (λ₀ = lowest operating wavelength).