jackschaedler / circles-sines-signals

A Compact Primer on Digital Signal Processing
982 stars 86 forks source link

Discussion about phase missing #33

Open rgetz opened 4 years ago

rgetz commented 4 years ago

In all the examples, including: https://jackschaedler.github.io/circles-sines-signals/dft_introduction.html

All the examples use clockwise rotation for their phasors, and use phase = 0 at t=0.

A concept that is missing is the relationship between the direction of the unit circle phasors (clockwise or counter-clockwise (or anti-clockwise, depending on where you grew up)) and how this effects the other transforms. For many areas of study, this is the key to understanding why Fourier spans from -Fs/2 to + Fs/2. It describes the direction of the unit circle vector (or the phase relationships between the signals).

I will not effect too many things until you get to Euler. https://jackschaedler.github.io/circles-sines-signals/euler.html

If the phasor rotates the other way, the relationship between I & Q changes, and the FFT shows up on the opposite side of the -Fs/2 to +Fs/2 scale. It's just a mathematical way of representing phase. (that's the part that is difficult to digest for some).

Just a suggestion.