Advantages of the Zoom FFT are :

- Increased frequency domain resolution
- Reduced hardware cost and complexity
- Wider spectral range

Applications of the Zoom FFT include :

- Ultrasonic blood flow analysis
- R.F. communications
- Mechanical stress analysis
- Doppler radar

The following diagram shows the zoom process :

One common question is : Is the zoom FFT the same as the chirp z-transform.

The answer is : Absolutely not. The FFT calculates the FFT at N equally spaced points around the unit circle in the z-plane, the chirp z-transform modifies the locations of these points along a contour that can lie anywhere on the z-plane. In contrast, the zoom-FFT uses digital down conversion techniques to localise the standard FFT to a narrow band of frequencies that are centered on a higher frequency. The chirp z-transform is often used to analyze signals such as speech, that have certain frequency domain charactgeristics. The zoom-FFT is used to reduce the sample rate required when analysing narrowband signals - E.G. in HF communications.

These functions, and more, are available in the SigLib DSP Library.

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