Fundamental Limitations for DOA Estimation by a Sphere
Sven Nordebo, Mats Gustafsson · Lund University Publications (Lund University) · 2004
In this paper we consider fundamental limitations for DOA estimation with arbitrary lossless antennas or antenna arrays inserted inside a sphere. Spherical vector modes and their associated equivalent circuits and Q factor approximations are employed as a general framework for the analysis. The classical broadband matching theory by Fano is extended to a general multiport S–parameter model of the antennas and fundamental bounds are given for the scattering parameters with respect to bandwidth and electrical size of the sphere. Finally, assuming a statistical signal model with Gaussian receiver noise, the Cramer–Rao lower bound is used to derive fundamental upper bounds for the performance of DOA estimation by a sphere.