Discrete Fourier Transform and Signal Spectrum - Digital Signal Processing: Fundamentals and Applications - page 100

FIGURE 4.9A
Amplitude spectrum and phase spectrum in Example 4.5.
FIGURE 4.9B
Power density spectrum in Example 4.5.
Note that the folding frequency in this example is 50 Hz and the amplitude and power spectrum values at
75 Hz are each image counterparts (corresponding negative-indexed frequency components), respectively. Thus
values at 0, 25, 50 Hz correspond to the positive-indexed frequency components.
We can easily find the one-sided amplitude spectrum and one-sided power spectrum as
A 0 ¼ 2:5; A 1 ¼ 1:4141; A 2 ¼ 1 and
P 0 ¼ 6:25; P 1 ¼ 2; P 2 ¼ 1