| Re: Complex -> Real FFT [message #16452] |
Mon, 26 July 1999 00:00 |
Jeff Wasserman
Messages: 1
Registered: July 1999
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Junior Member |
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David Fanning wrote:
>
> Jeremy Kepner (jvkepner@muse.Princeton.EDU) writes:
>
>> Does anyone know of a Complex to Real FFT that has
>> been implemented in IDL. (Likewise a corresponding
>> Real to Complex FFT would also be nice).
>
> I'm probably missing something deep here, but
> doesn't this do what you want?
>
> result = FLoat(complex_fft_expression)
> result = Imaginary(complex_fft_expression)
If you don't care about phase information with your FFT data, and
instead want just an absolute power measurement (like a spectrum
analyzer), you could use
power_spectrum = Abs(complex_fft_data)
[the abs function returns the value of sqrt(real^2+imaginary^2) if it's
argument is complex]
Conversely, you could also get the phase info into an array
phase_array = Tan(complex_fft_data)
[The tan function also nicely works with complex data]
From these two arrays you could then go back to the complex array.
However, as far as I know, there is no way to obtain the two independent
variables of the original complex array after it's been converted to
reals.
------------------------------------------------------------
Jeffrey Wasserman - Member of Technical Staff
Group 83 Electro-Optical Materials and Devices
MIT Lincoln Laboratory Lexington, MA
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