What is Frequency resolution?

In spectrum analysis, how finely two components at close frequencies can be told apart as separate components. For a DFT the guide is the bin spacing Δf = fs/N, which equals 1/T, the reciprocal of the observation time T = N/fs. For example, with fs = 48 kHz and N = 1024 it is about 46.9 Hz. Whether two components can actually be told apart also depends on the main-lobe width of the window function. Zero padding only makes the bin spacing finer and interpolates the spectrum; the ability to tell components apart remains set by the observation time. It is a different notion from the resolution (number of bits) of an AD converter.

Japanese name: 周波数分解能

Frequency resolution appears in 1 practice question across 1 topic, including Digital Signal Processing Basics.

Field: Digital Signal Processing Basics

Try it: questions about Frequency resolution

A 256-point signal is followed by 768 zeros (zero padding) and a 1024-point DFT is computed. Compared with computing the DFT of the 256 points as they are, which of the following is correct?

AThe spectrum is interpolated at finer spacing, but the ability to tell apart two sine waves of close frequencies does not change
BThe bin spacing becomes 1/4, and the ability to tell apart two sine waves of close frequencies also improves fourfold
CThe added zeros join the two ends of the interval smoothly, so spectral leakage disappears and peak heights can be read accurately

Show answer and explanation

Answer: A. The spectrum is interpolated at finer spacing, but the ability to tell apart two sine waves of close frequencies does not change

Zero padding makes the bin spacing finer, fs/1024, and gives values interpolated between those of the 256-point spectrum. No new information is added, however, so the ability to tell two frequencies apart (the frequency resolution) is set by the 256 samples actually observed and stays at about fs/256. Truly improving it requires recording data over a longer time. Zero padding is used to make peak positions easier to read or to bring the number of points to a power of two for the FFT.

Frequency resolution in the explanations

No new information is added, however, so the ability to tell two frequencies apart (the frequency resolution) is set by the 256 samples actually observed and stays at about fs/256.
A 256-point signal is followed by 768 zeros (zero padding) …

Questions that mention Frequency resolution (1)

A 256-point signal is followed by 768 zeros (zero padding) and a 1024-point DFT is computed. Compared with computing the DFT of the 256 points as they are, which of the following is correct?

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