A 25 dBm outphasing power amplifier with novel non-isolated combining network

This paper presents a 25 dBm outphasing power amplifier designed in a standard 45 nm CMOS process. Instead of using bulky quarter-wave transmission lines or transformers as non-isolated combiners, we propose a new combiner based on lump elements. The elements of the combiner act differently for in-phase and out-of-phase components, which allows additional resonant networks to be formed for improved backoff efficiency. The proposed PA design achieves 55% peak power added efficiency (PAE) at 900 MHz and 45% at 2.4 GHz. For an OFDM signal with 6 dB PAR, the PAE is 32% at 900 MHz and 22% at 2.4 GHz. The linearity of the PA meets WiFi spec without digital predistortion (DPD). With DPD, the linearity of the PA can be improved further to reach -53 dBc, -50 dBc, -42 dBc ACPR for 10 MHz, 20 MHz, and 2-carrier 20 MHz LTE signals.