Zero-Padding for Interpolating Spectral Peaks

For sinusoidal peak-finding, spectral interpolation via zero-padding gets us closer to the true maximum of the main lobe when we simply take the maximum-magnitude FFT-bin as our estimate.

The examples in Fig.2.5 show how zero-padding helps in clarifying the true peak of the sampled window transform. With enough zero-padding, even very simple interpolation methods, such as quadratic polynomial interpolation, will give accurate peak estimates.

Figure 2.5: Illustration of ideal interpolation in the frequency domain as a result of zero padding in the time domain.

Another illustration of zero-padding appears in Section 8.1.3 of [264].