I'm trying to plot the phase of this signal $s(f)=A^2T^2sinc^2(Tf)e^{-(j\pi Tf)}$ How can I plot manually this signal?I have to follow some particular rules?I have problems with the delay.


After calculation I found that the phase for this signal is: $\phi(s(f))=-\pi Tf$

it should be this the plot. Right or not?

I plot it for $T =3$

enter image description here


1 Answer 1


This is indeed correct. There is a few things you could do to make it a better graph:

  1. Label the X-axis
  2. Label the Y-axis
  3. Use real physical units if it's applicable. Phase is measured either in radians or in degrees. These are VERY different things, so proper labeling with units helps to clarify what you are using. Similar if f is a frequency in Hz (or kHz or MHz) and T is a time (in nanoseconds or fortnights), it should be stated.
  4. You could consider changing the Y-grid so that the grid lines match with meaningful phase values such as 2*pi (or an integer multiple thereof).
  5. Along the same lines, you could alternatively normalize the phase to a meaningful value (like 2*pi) and keep the integer grid.
  6. If the result was obtained by Fourier transform of a real valued time domain signal and the context is clear, consider omitting the left half (f<0) of the plot. The convention is to only plot positive frequencies and the complex conjugate symmetry is implied.

This may sound nit-picky, but making a good graph is typically time well spend. It really helps to clarify what's going on, simplifies communication and will help you to remember what you did when you look at it in 3 months from now.

  • $\begingroup$ +1. Much like in the early years of engineering school they drill into you that "a number is meaningless without a unit," a plot is meaningless without being labeled appropriately. It's worth taking the time to do so. $\endgroup$
    – Jason R
    Mar 24, 2012 at 14:36
  • $\begingroup$ xkcd.com/833 $\endgroup$
    – endolith
    Mar 26, 2012 at 18:42

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