Page 384 - Fundamentals of Radar Signal Processing

This occurs when the spectrum is sampled at the Nyquist rate in Doppler, K =

M; no window is applied to the data; and the data frequency does not happen to
fall on a DFT frequency sample (the very situation in which interpolation is
most needed). Figure 5.21a illustrates this case. The data are M = 20 samples of
a 1.35-kHz complex sinusoid sampled at 5 kHz. The spectrum was computed
using a K = 20 point DFT. Without interpolation, the largest DFT magnitude
sample has a value of 15.15. This apparent peak amplitude is in error by 24.3

percent from the true DTFT peak value of 20. The DFT samples occur every
5000/20 = 250 Hz, so the apparent peak occurs at a frequency of 1500 Hz, an
error of 150 Hz.