An Integrated Continuous Class- ${\rm F} ^{-1}$ Mode Power Amplifier Design Approach for Microwave Enhanced Portable Diagnostic Applications

This paper presents a novel technique for designing a microwave power delivery system targeted at compact and portable microwave-assisted diagnostic healthcare applications to help tackle the growing problem of anti-microbial resistance. The arrangement comprises a purpose-built cylindrical cavity resonator within which, the bacterial samples are exposed, driven by a high-efficiency 10-W GaN amplifier, critically coupled via a simple, adjustable internal loop antenna. The experimental work considers the exposure of different sample volumes of water and the change in the natural impedance environment of the cavity that results. For the first time, it is shown that impedance variation cannot only be accommodated, but can actually be exploited, allowing “continuous,” high-efficiency performance to be achieved while processing a wide range of sample volumes. Specifically, using only transistor package parasitics, the impedance of the cavity itself together with a single-series transmission line allows a continuous class- F ^-1 mode loading condition to be realized. Measured results show more than 70% average drain efficiency, above 40-dBm average output power, and more than 10-dB gain over the cavity´s operational bandwidth.