Separable Signals

• A 2-D signal $x$ is separable if
  
  $$x(n_1,n_2) = f(n_1) g(n_2)$$
  
  

• An $M$-dimensional signal $x$ is separable if

  
  

  $$x(n_1,n_2,...,n_M) = \prod_{i=1}^Mf_i(n_i)$$