Image Processing Reference
In-Depth Information
Fig. 3. Block diagram of the DFSA
3.2 Measurement methods
Digital beat signals processing is separated two steps that consist of coarse measuring and
fine measuring. The two steps are parallel processed at every measurement period. The
results of coarse measuring can be used to remove the integer ambiguity of fine measuring.
3.2.1 Coarse measurement
The coarse measurement of beat frequency is realized by analyzing the power spectrums
beat signal. The auto power spectrums of the digital signals are calculated to find the
frequency components of beat signal buried in a noisy time domain signal. Generating the
auto power spectrum is by using a fast Fourier transform (FFT) method. The auto power
spectrum is calculated as shown in the following formula:
*
FFT x FFT
()
()
x
Sf
()
(3.1)
x
2
n
Fig. 4. The power vs. frequency in Hertz
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