High-Efficiency Class-E Seamlessly Integrated Active-Integrated Antennas of Far-Field SWIPT Base Stations for Batteryless IoT Applications

A deep integration of active-integrated antennas (AIAs) with high transmitter efficiency (TE), high polarization purity, and low interference has presented a difficult-to-ignore challenge for designers. This fundamental problem in AIA design emerges from the lack of an impedance-matching flexibility between the antenna aperture and active element for high dc-to-RF efficiency without deteriorating the radiator’s performance. This work proposes and presents an approach for the seamless integration of AIAs based on a modified rectangular patch loaded with shorting pins. Numerical and experimental results obtained in this research demonstrate that by distributing the shorting pins in the nodes of the fundamental and second-harmonic spatial modes of the canonical patch, new degrees of freedom for flexible impedance matching can be achieved without compromising the radiator’s radiation pattern, polarization purity, and radiation efficiency. The effectiveness of the proposed design strategy is illustrated by a fabricated seamlessly integrated AIA that presents the highest active gain reported in the literature while keeping cross-polarization (CP) and harmonic-interference levels low. Based on the obtained results, the proposed design strategy is believed to have great potential for developing low-cost and high-efficiency far-field simultaneous wireless information and power transmission (SWIPT) base stations for batteryless Internet of Things (IoT) applications.