Experimental Study of the Effects of Antenna Crosstalk on the Linearity and Efficiency of 5G Sub-6 GHz Wideband 2 × 2 Transmitter Arrays

This paper presents an experimental study of the effects of antenna crosstalk on the linearizability and efficiency of fifth-generation (5G) sub-6 GHz wideband massive multiple-input multiple-output (MIMO) transmitters. The transmitter consists of 2 × 2 arrays of class AB and Doherty power amplifiers (PAs) connected to an antenna array with reconfigurable spacing. The ability of single-input single-output (SISO) and dual-input single-output (DISO) digital predistortion (DPD) techniques to linearize the PA arrays is assessed under 5G-candidate 100 MHz orthogonal frequency-division multiplexing (OFDM) test signals. From measurement results, DISO DPD successfully linearized the transmitter front-end (adjacent channel power ratio below −48 dBc) for both class AB PA and Doherty PA (DPA) arrays. Despite the effects of antenna load mismatch and crosstalk, the DPA architecture is still preferable to class AB PAs in5G MIMO systems since it can achieve a higher drain efficiency while maintaining similar linearity.