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.

翻译：针对圆形阵列，研究了近场感知的性能界，重点关注带宽与阵列尺寸的影响。推导了角度与距离估计的闭式克拉美-罗界（CRB），揭示了CRB随带宽和阵列尺寸变化的标度律。与预期相反，增大阵列尺寸并不总能提升感知性能。进一步分析了不同条件下的渐近CRB，表明所推导的表达式将现有结果作为特例包含其中。最后，通过数值结果验证了所推导表达式的有效性。