Enabling High Efficiency Bandwidth Electrically Small Antennas through Direct Antenna Modulation

High-bandwidth communications in electrically small antennas (ESA's) are often limited by the inherent narrowband performance physically defined by Chu's limit for these types of emitters. With the advent of compact platforms in unmanned aerial vehicles (UAV's) which may have electrically small volumes yet utilized in systems such as Internet of Things (IoT), supporting such technologies require high-performance antennas capable of radiating high-bandwidth signals. We propose a novel capacitively loaded loop antenna (CLLA), comprised of two complementary and symmetrical high-power high figure-of-merit (FoM) GaN transistors. The antenna utilizes Direct Antenna Modulation (DAM) which, through the transistors, carefully modulate the input RF signal. This allows the transmission of high-bandwidth signals, despite the high radiation Q-factor of the CLLA. The DAM antenna was prototyped, measured, and compared to a conventional CLLA without transistors. The antenna radiates high-bandwidth signals and shows significant efficiency-bandwidth product improvement over traditional ESA's.