High Efficiency Bandwidth Electrically Small Antennas for Compact Wireless Communication Systems

Abstract

The RF bandwidth of systems that are constrained into electrically small volumes are often limited to the resonance bandwidth dictated by the radiation quality-factor of the antenna according to Chu’s limit. Still, many systems, both legacy and emerging, such as in unmanned aerial vehicles (UAV) for applications in the Internet of Things (IoT), require the ability to communicate amongst various systems that may not contain the available electrical volume to support conventional transmission of desired signals. We propose a novel electrically small antenna enabled through Direct Antenna Modulation (DAM). The design of the system utilizes a capacitively loaded loop antenna (CLLA) integrated with symmetrical high-power and high figure-of-merit (FOM) GaN transistors that optimally modulate an input BFSK signal to allow for high-bandwidth radiation, despite the radiation Q-factor of the antenna. The system was prototyped and measured, achieving a 47 efficiency-bandwidth product improvement over a conventional CLLA, surpassing aforementioned limits.