IFFT time-interval units
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If I do an inverse-FFT of an amplitude and phase vs frequency plot (where there are 2000 points for a range of 0 to 2 GHz frequency at 1 MHz sampling intervals) , what is the time units X-axis of the resulting inverse-FFT value? Is the inverse-FFT data reported for every 1 ns (ie 1 GHz) , 0.5 ns ( 2 GHz) or 0.25 ns (ie 4 GHz) intervals?
example : For inverse-FFT Generation, I use matlab command x=ifft(complex number in reactangular form) . Will result "x" be generated with data (in time domain) at double the sample rate of max-frequancy (2GHz) in frequency domain? This would be 2x2 GHz ie 4GHz intervals ( ie 0.25ns each in time scale)?
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Star Strider
on 5 Mar 2019
My calculations would indicate 0.25 ns.
Derivation:
Fn = 2E+9; % Nyquist Frequency
Fs = Fn*2; % Sampling Frequency
Ts = 1/Fs % Sampling Interval
producing:
Ts =
2.5000e-10
This is a one-sided Fourier transform (also assuming that it is calculated and reported correctly, and the frequency axis is not artificially truncated). Since 2 GHz is the Nyquist frequency (½ the sampling frequency), multiplying it by 2 to yields the sampling frequency, Fs. The sampling interval is the inverse of that, 2.5E-10 s or 0.25E-9 s = 0.25 ns.
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Star Strider
on 21 Mar 2019
I have no experience with ADS tools. If what it does conforms to my assumptions, my analysis would hold. If it does not, then my analysis is not applicable to it.
Since I now have no idea what you are doing, I will delete my Answer in a few minutes.
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