A Fully Integrated 47.6% Fractional Bandwidth GaN MMIC Distributed Efficient Power Amplifier With Modified Input Matching and Power Splitting Network

This article presents a fully integrated distributed efficient power amplifier (DEPA) for fifth-generation (5G) massive multiple-input multiple-output (MIMO) applications. In conventional DEPA, an individual input matching network (IMN), power splitter, and phase compensation line are used for each auxiliary power amplifier (PA) unit, resulting in a large overall size. To facilitate integration, an energy-efficient and compact DEPA with modified input matching and power splitting network is proposed, where a distributed input matching network (DIMN) is used for the auxiliary PA. A broadband input matching, reasonable power splitting, and phase alignment can be achieved simultaneously by adjusting the dimensions of gate transmission lines (TLs) between different auxiliary PA units. An integrated DEPA is implemented in a commercial 0.25-Am GaN-HEMT process to validate the proposed architecture. The fabricated DEPA shows a saturated output power of 40.4-41.7 dBm, an 8-dB back-off drain efficiency (DE) of 35%-50%, and a saturated DE of 46%-56% from 3.2 to 5.2 GHz, with a compact size of 3.4 x 3.0 mm(2). Applying a 100-MHz orthogonal frequency division multiplexing (OFDM) signal with a 7.8-dB peak-to-average power ratio (PAPR), an average efficiency of 35.7%-47% is measured over the entire bandwidth, and the adjacent channel power ratio (ACPR) is better than -46 dBc after digital predistortion (DPD). To the best of our knowledge, the proposed DEPA demonstrates the widest bandwidth among all reported fully integrated back-off efficient PAs without using digital techniques or reconfiguration.