I don't know if it is your question, but there can be subleties involved when we try to give a math expression for a swept sin. In particular, see this thread: thread384-29248: Swept sine spectrum puzzler

The easy bottom line to that wandering thread - try plotting your proposed analytical expression (like op of linked thread did) to see if the apparent frequency matches what you intended or a factor of 2 different.


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(2B)+(2B)' ?