Questions as follows: probably signals 1 and 2 work together to get the signal 3 (work together, there are several kinds of circumstances is one of the most simple direct multiplication), are applying frequency signals 1 and 2, respectively, f1 and f2 of intensity modulation, for the 3 signal demodulation frequency (f1 and f2) or (f1, f2) frequency component (and there are other frequency), ask how to make (f1 and f2) or (f1, f2) frequency component of the maximum strength?
Hope glad