A Class-E, Switched-Mode, Non-LTI Electrically-Small Transmit Antenna Design for Overcoming the Fundamental Bandwidth-Efficiency Product Limits

We present a switched-mode, non-linear-time-invariant (non-LTI) electrically-small antenna (ESA) designed to overcome the theoretical bandwidth-efficiency product limitations governing the performances of passive, LTI ESAs. The proposed non-LTI ESA operates by integrating a class-E, switched-mode inverter, designed to act as an ideal voltage source, with an electrically-small, self-resonant radiator. There is no impedance matching between the output of the class-E inverter and the input of the self-resonant, ESA. This way, the class-E inverter is directly driving a resonant load with a small input resistance without using any intermediate impedance matching stage to 50 Ω. To generate a digitally-modulated waveform, the current passing through the antenna is directly modulated by controlling the bias voltage and/or the gate driver signal of the class-E inverter. Through combined numerical electromagnetic simulation and transient circuit simulation, we demonstrate that a wide range of digitally-modulated waveforms may be generated. We demonstrate that the proposed non-LTI transmitting ESA is capable of offering bandwidth-efficiency product improvements of 10 dB over a passively-matched ESA.