Understanding Digital Signal Processing, Second Edition

Chapter Eight. Quadrature Signals

Quadrature signals are based on the notion of complex numbers. Perhaps no other topic causes more heartache for newcomers to DSP than these numbers and their strange terminology of j-operator, complex, analytic, imaginary, real, and orthogonal. If you're a little unsure of the physical meaning of complex numbers and the j = operator, don't feel bad because you're in good company. Sixteenth century Italian mathematician Girolamo Cardano described an imaginary number “as subtle as it is useless.” In the 17th century ...