An Efficient Asymmetric Outphasing Power Amplifier With Extended Back-Off Range for 5G Applications

5G and future 6G wireless communication systems are pushing the practical limits on the modulation schemes that can be achieved in practice. These higher-level modulation schemes have further exacerbated the challenges in power amplifier (PA) design. One solution to linearly and efficiently amplify these modulation schemes that have high peak-to-average power ratios (PAPRs), is to use dual-input Outphasing PAs (OPAs). However, the output back-off (OBO) range of a conventional OPA is limited. To mitigate this issue, a new OPA based on an asymmetric architecture is proposed. This new asymmetric OPA is shown theoretically that the OBO range can be extended. To validate the proposal, an OPA is designed using two asymmetric sub-PAs and a modified Chireix combiner. The implemented OPA achieves drain efficiencies of 60.6% and 60% at saturation (44.1dBm) and at 8-dB OBO under CW excitation at 2.58 GHz, respectively. Measurement of the OPA using 20-MHz 5G NR signal with 8-dB PAPR yields an average drain efficiency of 58.3% with an adjacent channel power ratio (ACPR) below -45.1 dBc with digital pre-distortion (DPD).