Delaying a signal then multiplying by the original

[sittinduk]

Hi there,

I'm very new to LabVIEW but I'll try and explain my problem: I'm currently able to receive a waveform from an oscilloscope and display with no problem. The signal I'm measuring is a sinusoid with linearly increasing frequency (a linear chirp). However, what I really want to do is to delay the signal by ~500us and then multiply it by the original. Then, I want to do an FFT on the result.

I tried something similar to the attachment below (found for a similar problem) where I try to change the time components of one signal but when I try and combine them, I simply get the original signal with no modulation.

[Freelance_LV]

Hi

With what you are doing, you will plot two waveforms on the graph, one original and the other with a time delay. (Edit: Set your X axis to absolute time display an you ll see both the waveforms)

If you want to modulate, you should be using the modulation functions available with LabVIEW Modulation Toolkit.

Else, (i think) you can simply use the 'Gaussian modulation' function available with basic labview functions. i have not used this function, though.

then, use the FFT functions on the ouput signal.

[GerdW]

Hi sittinduk,

so you want to shift your waveform Y data by a certain amount of time...

Using a plain Multiply will only take the Y arrays for standard multiplication not caring about time settings (AFAIK).

A basic way could be to rotate (or shift) the by a certain number of samples (given by shift time * sample rate) and then multiply your signals.

Btw. there are functions for correlation in the signal functions palette...