Re: how does fourier transform transforms time to freq domai
Have you ever got any experience to count total amount of money consisting of only coins? Assume that you got a load of coins on the table and you want to count how much they add up to. There are two ways to do it. In the first way, you start to count from one side of the table. A penny ... and a quarter ... they add up to 26 pennies.... then a dime .. the total ..um... is 36 pennies .. and so on. In the second way, you first pick out all the pennies and put aside, you then pick out all nickles ... and then the dimes ... quarters. This way, it's easy for you to see how many coins you have in each case and, therefore, easier to count the total.
The first way is like the time domain analysis, in which you move like a bulldozer, from the beginning to the end. The second way is like the freq domain analysis, in which you move from the top to the bottom (from high freq to low freq). If you multiply your signal by a COMPLEX signal, it is just like adding a constant number to all the coins. For example, if the fixed number (the freq that COMPLEX signal has) is 10, then all quarters become "35 pennies", dimes "20 pennies" ... ain't they cute?