Multi-Mode Expansion of Outphasing Power Amplifier Based on Non-Commensurate Transmission Line Combiner

Though Outphasing power amplifier (OPA) exhibits high efficiency across a wide dynamic power range, its frequency coverage is constrained, prompting novel design techniques to enable broadband or multi-band operation. This paper proposes a mode expansion methodology for OPAs that adopt a non-commensurate transmission line combiner (NCTLC). It is indicated in this paper that an NCTLC-based OPA has eight distinct operation modes by judiciously expanding the delta length and base length of the NCTLC, as well as reconfiguring the Outphasing angle. Theoretical analyses confirm that the performance advantages of the OPA can be preserved before and after mode expansion. It is precisely the multi-mode operation that enhances the design flexibility of NCTLC-based OPAs. Moreover, to efficiently design the NCTLC, a relationship between the back-off range of the OPA and the delta length of the NCTLC is established. For experimental validation, three prototypes are designed and fabricated using Wolfspeed CGH40010F devices. Among these, two single-band OPAs operate at 1.0 GHz and 1.2 GHz, and a dual-mode dual-band OPA operates at 1.96/2.48 GHz. The measurement results indicate that the saturation output power of all OPAs is greater than 43.1 dBm with drain efficiency (DE) of above 56%. In the meantime, the 6 dB back-off DEs of all OPAs exceed 50.5%.