  The performance bounds of near-field sensing are studied for circular arrays,
focusing on the impact of bandwidth and array size. The closed-form Cramer-Rao
bound (CRBs) for angle and distance estimation are derived, revealing the
scaling laws of the CRBs with bandwidth and array size. Contrary to
expectations, enlarging array size does not always enhance sensing performance.
Furthermore, the asymptotic CRBs are analyzed under different conditions,
unveiling that the derived expressions include the existing results as special
cases. Finally, the derived expressions are validated through numerical
results.
