Single-Feed Planar Multiband Quasi-Isotropic Antennas Through Collocating and Co-Design Approaches

This article presents single-feed planar multiband quasi-isotropic antennas through collocating and co-design approaches. The antenna element is a modified dipole with an inclined central part, whose effects are anticipated at the design stage. The concept is implemented on a dual-band quasi-isotropic antenna, fabricated, and verified experimentally with good correlation with simulations. The fabricated prototype covers the frequency bands of 815-1095 (280 MHz, 29.31%) and 1650-2090 MHz (440 MHz, 23.52%), with gain variations of 7.7 and 10.1 dB at 940 and 1800 MHz, respectively. The corresponding peak gains are near 1.7 and 1.2 dBi, with 90%-95% and 63%-93% efficiencies. The present design features are planar shape, single feed, wide impedance bandwidths, good isotropic patterns, and scalability to more isotropic bands. These options make the fabricated prototype suitable for most wireless applications, particularly for optimally collecting the ambient radio frequency (RF) power from any direction and frequency using a planar harvester.