Radiation Efficiency Enhancement for Dipoles Placed Adjacent to Lossy Silicon Substrates

Radiation efficiency of a dipole antenna is discussed when placed closely to a 0.11x0.11 lambda(2)(e) low-resistivity (10 Omega.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 0.13x0.2 lambda(2)(e). Co- and cross-polarized radiation patterns in H and E planes are measured with the silicon wafer placed 0.003 lambda(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 2x. 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).