  In some applications of frequency estimation, it is challenging to sample at
as high as the Nyquist rate due to hardware limitations. An effective solution
is to use multiple sub-Nyquist channels with coprime undersampling ratios to
jointly sample. In this paper, an algorithm suitable for any number of channels
is proposed, which is based on subspace techniques. Numerical simulations show
that the proposed algorithm has high accuracy and good robustness.
