Design of a mixed load‐modulation balanced power amplifier with ultra‐extended power back‐off range

Summary This paper proposes a mixed design strategy to expand the power back‐off (OBO) range of the pseudo‐Doherty load‐modulation balanced power amplifier (LMBA). An asymmetric LMBA configuration is employed to increase the OBO range. The two PA branches of the balanced PA operate in different class‐C modes, thereby obtaining two OBO points. Further, an asymmetrical coupler is also introduced into the asymmetrical LMBA architecture to expand the OBO. Here, the relationship between the OBO and coupler's parameters and asymmetrical configuration parameters is built. The behaviors of the proposed PA as a function of input power are derived when several representative parameters are chosen. To validate the proposed topology, a PA with an OBO of 15 dB operating across 3.4–3.6 GHz is designed, fabricated, and tested. Measurements illustrate that the PA can deliver a saturated output power of 43.6–44.5 dBm with a drain efficiency ranging from 70% to 72%. Drain efficiencies are between 50% and 68% at the OBO of 15 dB. The LMBA implemented here shows state‐of‐the‐art performance in terms of the OBO range. The pseudo‐Doherty load‐modulation balanced power amplifier (LMBA) consists of an asymmetric LMBA configuration and an asymmetrical coupler, thus greatly expanding the OBO. An LMBA with an OBO of 15 dB operating across 3.4–3.6 GHz is realized. The LMBA implemented here shows state‐of‐the‐art performance in terms of the OBO range.