An integrated inverse-F power amplifier design approach for heating applications in a microwave resonant cavity

This paper presents a novel approach for designing a compact and high efficiency solid-state microwave heating apparatus suitable for bedside and field-deployable health-care diagnostic applications. The arrangement uses an LDMOS device and a purpose-build single-mode (TE011) rectangular Cavity. In this novel approach, a high-efficiency inverted class-F mode has been achieved by shaping the current and voltage waveforms at the current generator plane. This has been achieved using the natural impedance environment presented by the cavity together with a very simple series microstrip arrangement to present the required inverted class-F harmonic loading conditions for shaping the voltage and current waveforms for a 10W LDMOS power transistor. This compact structure also includes an in-built coupling structure to measure the incident and reflected power at the output of the inverted class-F power amplifier (PA) at 2.45GHz. The integrated microstrip structure not only simplifies the matching network significantly, but also provides a more compact design for straightforward integration to a microwave resonant cavity, without the need for intermediate 50 Ohm matching.