Radiation efficiency enhancement for dipoles placed adjacent to lossy silicon substrates

Radiation efficiency of a dipole antenna is discussed when placed closely to a 0.11×0.11 λ_e² low-resistivity (10Ω·cm) silicon wafer. The use of a small-size floating metal layer underneath the silicon wafer is proposed for efficiency improvement. The total antenna area with the silicon wafer is 0.13×0.2 λ_e². Co- and cross-polarized radiation patterns in H and E planes are measured with the silicon wafer placed 0.003 λ_e away from the dipole. Full-wave simulations reveal that placing the floating metal layer underneath the lossy silicon substrate increases the total radiated power by approximately 2×. This is validated experimentally by fabricating 3.5-GHz FR4 dipoles next to lossy silicon substrates with and without the aforementioned floating metal. Measured radiation patterns are presented for both cases and result in extracted radiation efficiencies of 72% (floating metal present) and 43% (no floating metal).