Wideband PPT Class Φ2 Inverter using Phase-Switched Impedance Modulation and Reactance Compensation

Abstract

The Class Φ2 is a suitable power amplifier (PA) topology for applications that demand low device voltage stress and simple gate driving. The push-pull with T network (PPT) version of this architecture can be advantageous over a conventional single-ended Φ2 due to higher power capabilities through interleaving and simple closed-form design equations. The downside with this and many other switch-mode PAs is that they perform efficiently only at a single frequency with the power degrading outside the nominal point of operation. To solve this issue, we incorporate a phase-switched impedance modulation (PSIM) variable capacitor and a reactance compensation network so that the PPT Φ2 can function across broadband. We experimentally demonstrate a 300 W PA for a 50 Ω load impedance using silicon (Si) devices. The PA achieves above 90% efficiency over approximately a 30% fractional bandwidth. In addition, the PA can also operate across broadband with light loads, where above 80% efficiency is maintained for up to 5 times higher load resistances. This switch-mode PA is one of the first to demonstrate such performance under load variation across a wide bandwidth.

Photograph of the 300 W wideband PA showing the (a) top-view and (b) bottom-view of the system.