Cramér-Rao Bounds for Wideband Near-Field Sensing

The evolution of array signal processing technologies is progressing toward the deployment of compact, densely arranged sensors to form extremely large aperture arrays (ELAA), aiming to significantly improve angular resolution and beamforming gain. In this paper, we propose a wideband near-field sensing system that combines orthogonal frequency-division multiplexing (OFDM) signaling with ELAA technology. The ELAA transmitter emits wideband signals, while the radar receiver processes the echoes to estimate critical target parameters, including location, velocity, and radar cross-section. We then derive the generalized Cramér-Rao lower bound (CRB) to assess the OFDM system’s estimation performance. Numerical experiments reveal that the proposed wideband near-field sensing system outperforms its far-field and narrowband counterparts by achieving lower CRB values.