Limitations and Strengths of the Fourier Transform Method to Detect Accelerating Targets

摘要

There are limitations and shortcomings to the Fourier transform method to detect accelerating targets because of the phenomenon known as Doppler smearing. In using a Pulse Doppler Radar to detect a non-accelerating target in additive white Gaussian noise and to estimate its radial velocity, the Fourier method provides an output signal-to-noise ratio (SNR) that increases linearly with the number of pulses. When the target is accelerating, the Fourier method may still be used to detect the target and estimate its median velocity, provided the acceleration is small enough in the sense described in the paper. For a given acceleration, when the number of pulses is increased, the output SNR of the Fourier method varies as a concave function, increasing to a maximum and then decreasing, before the method fails catastrophically. Thus the number of pulses and the acceleration have to be matched to achieve optimum performance. Empirical formulae for the dependence of the optimum SNR and the optimum number of pulses on the acceleration are given. The results are shown to be relevant to the design of Generalized Likelihood Ratio Test (GLRT) based detectors that apply a search over a grid.