I would like to lock two RF sources together that are at different frequencies. I hesitate to say I would like to phase lock them because they are at different frequencies. I guess what I'm looking for would be to lock the signals together in time such that they don't drift relative to each other. For my application, the second source (4.9 GHz) is at twice the frequency of the first source (2.45 GHz). In terms of the lock between the two, what is necessary is that every time the first source crosses zero, the second source is at a constant value (e.g. the sources are offset in time by some constant value). Any help would be appreciated. Thanks!