Fourier spectral analysis using Walsh functions
Eduardo Cavanagh · The Journal of the Acoustical Society of America · 1977
Digital electronics allows for the easy generation of Walsh functions, which are a set of orthogonal functions Periodic functions can be expanded into Walsh series by finding the expansion coefficient in the normal manner of multiplying the function and integrating over one period. From these coefficients, the Fourier-expansion coefficient can be calculated. For sinusoidal waves, in-phase and quadrature Fourier components can be ascertained by two Walsh-function coefficients.