Plotting a frequency spectrum for an Impulse Response

Hi there,

I know I might be asking a completely novice question (and apologies on possibly spamming the forums) but I am extremely new with Matlab and still need a step by step guide on how to work this thing out. I've attached a picture on the type of graph that I'm trying to replicate.

I am currently working on trying to plot out the impulse response of a signal on a frequency domain graph. As such, I'm still struggling trying to plot a frequency spectrum graph as shown in the picture. I am unsure of how one would be able to adjust the frequency on the x-axis to match the one shown in the picture as well as how to match the magnitude (db) on the Y-axis. This is what I've got so far:

I'm not sure if the steps I've taken are correct. Any help in terms of carrying out the code and steps would be appreciated!

Regards

Answer 1

[Star Strider]

Since the impulse has a uniform spectrum equal to unity, the impulse response of a system (control system, filter, etc.) is generally the Fourier transform of the output of the system.

Note that Figure 4.3.5 is plotted as dB on a logarithmic frequency axis.

The plot you created appears to be linear in both axes. You can calculate dB as:

dB = 20*log10(abs(amplitude))

To plot the frequency axis logarithmically, use the semilogx plot function.

So your plot call to simulate Figure 4.3.5 would be something like:

figure
semilogx(frequency, 20*log10(abs(amplitude)))