The sampled sinusoids generated by integer powers of the roots of unity are plotted in Fig.6.2. These are the sampled sinusoids used by the DFT. Note that taking successively higher integer powers of the point on the unit circle generates samples of the th DFT sinusoid, giving , . The th sinusoid generator is in turn the th th root of unity (th power of the primitive th root of unity ).
Note that in Fig.6.2 the range of is taken to be instead of . This is the most ``physical'' choice since it corresponds with our notion of ``negative frequencies.'' However, we may add any integer multiple of to without changing the sinusoid indexed by . In other words, refers to the same sinusoid for all integers .
Notation and Terminology
Nth Roots of Unity