Effective DoF Collapse in Sparse Near-Field Beamforming: A Block-Rank-1 Mechanism
Sparse near-field arrays phase-cohere <inline-formula> <tex-math notation="LaTeX">$M$ </tex-math></inline-formula> widely separated sub-arrays of <inline-formula> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> elements and underpin distributed MIMO, satellite formations, and integrated sensing and communic...