So the addition of frequencies requires that the input signal already contains a non-linear component. and for entirely linear input the frequencies would not be additive. Harry
On Sun, Oct 18, 2020 at 12:08 PM Bob Higgins <rj.bob.higg...@gmail.com> wrote: > 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 >> >>>
