How do I synchronize the timing between multiple DAC channels for coherent multi-channel transmission?

Synchronizing the timing between multiple DAC channels for coherent multi-channel transmission ensures that all DAC outputs are phase-aligned and time-aligned, which is essential for: beamforming (the relative phase between channels determines the beam direction; phase error directly causes beam pointing error and sidelobe degradation), MIMO transmission (the channels must be synchronized to maintain the precoding matrix accuracy), and calibration (channel-to-channel skew must be measured and corrected). Synchronization approach: common clock distribution (all DACs share a single clock source, distributed through a low-skew clock buffer (e.g., a fanout buffer or clock distribution IC); the clock skew between channels must be less than a fraction of the sample period (typically less than 10-50 ps for 1-10 GHz sampling rates)), SYSREF synchronization (JESD204B/C interfaces use a SYSREF signal: a periodic signal synchronized to the device clock that establishes a common timing reference across all DACs; the SYSREF edge aligns the DAC's internal data path latency to a deterministic value; all DACs see the same SYSREF edge and establish the same internal latency), and FPGA-side alignment (the FPGA's multi-channel DUC must deliver data to all DACs with the same latency; the FPGA's JESD204 transmit cores must be synchronized so that data for sample N arrives at all DACs simultaneously; techniques: use a common LMFC (Local Multi-Frame Clock) counter across all JESD204 links, and: insert deterministic latency in each channel to equalize the total FPGA-to-DAC latency). The residual timing error after synchronization: typically less than 1-10 ps (achievable with modern DACs and careful clock distribution), which corresponds to less than 1-3 degrees of phase error at 3 GHz (acceptable for most applications).