A Dual-Rate Hybrid DAC for High-Speed 6G Massive MIMO Transceivers

This paper presents the design, modeling, and simulation of a dual-rate hybrid digital-to-analog converter (DAC) architecture optimized for 6G massive multiple-input multiple-output (MIMO) transmitters. The proposed structure splits the digital input into a low-resolution Nyquist-rate path for the most significant bits (MSBs) and a high-speed delta-sigma modulator (DSM) path for the least significant bits (LSBs). This configuration enables a favorable trade-off between bandwidth, linearity, and power efficiency, while addressing the limitations of conventional Nyquist and DSM-only DACs. We demonstrate how the architecture improves robustness without dynamic element matching (DEM), and analyze the spectral behavior including out-of-band (OOB) noise suppression. Simulation results using sinusoidal and 256-QAM modulated inputs confirm that the hybrid DAC achieves spectral cleanliness compared to pure DSM DACs, even in the presence of 1% mismatch. These findings position the hybrid DAC as a scalable and efficient solution for wideband digital radio frequency (RF) applications.