  In this paper, performance bounds for the multi-antenna near-field range
estimation of extended targets are provided. First, analytic expressions of the
ambiguity functions are obtained, emphasising the cooperation between the
waveform delay and the near-field phase shift information. The impact of
estimating the range of an extended target with a point target model is
analysed, showing that a model mismatch leads to severe performance degradation
in the near-field region. Secondly, Cramer-Rao bounds are derived. Expressions
emphasising the parameters' impact are obtained, the parameters being the
carrier frequency, and the central frequency and root-mean-square bandwidth of
the waveform. The near-field range information is shown to depend on the
root-mean-square value of the propagation delay derivatives, this value scaling
with the fourth power of the ratio between the antenna array dimension and the
target range.
