Orthogonally aliased fourier transforms for the analysis of sparsely populated frequency spectra
R. Benjamin · Proceedings of the Institution of Electrical Engineers · 1977
A trick permits the use of several aliased fast Fourier transforms (f.f.t.) in place of a single unambiguous f.f.t. If the proportion of active spectral lines, or directions of arrival, is well under 1%, their location, but not the amplitude, can then be computed with a dramatically reduced workload.