To get frequencies in the output that were not in the input requires a nonlinearity. If you model the nonlinearity using a series such as Y = a + bX + cX^2 + dX^3... then all of the terms with X^2 and greater are the nonlinear terms. Usually the coefficient of the squared term, c, is the largest of the nonlinear terms. When you have an input that is the sum of two frequencies, you get a component in Y that is c[sin(w1t) + sin(w2t)]^2 . It is the square of the sum of sines that produces the sum and difference frequencies.
In the case of the Moire masks, you end up with a multiplication taking place, not a sum. The product of sines will also produce a sum and difference. Multiplication of inputs is a nonlinear operation. On Sun, Oct 18, 2020 at 9:44 AM H LV <hveeder...@gmail.com> wrote: > Hi, > When two waves of different frequencies combine the result is a third wave > with a beat frequency corresponding to the difference between the two > original frequencies. A wave model can show how this happens, but I don't > see how it can bring about the addition of frequencies. Can someone model > this additive process for me? > > Harry > >>
