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Indeed to compute the zoom spectrum, it is necessary to compute 2 signals: | Indeed to compute the zoom spectrum, it is necessary to compute 2 signals: | ||
R (t) = input (t) * cos (2 * PI * fc * t) | R (t) = input (t) * cos (2 * PI * fc * t) | ||
I (t) = input (t) * sin (2 * PI * fc * t) | I (t) = input (t) * sin (2 * PI * fc * t) | ||
With fc = Zoom center frequency ; input (t) = input signal. | With fc = Zoom center frequency ; input (t) = input signal. | ||
Then The signals R (t) and I (t) are decimated (zoom factor: 2, 4, 8…). | Then The signals R (t) and I (t) are decimated (zoom factor: 2, 4, 8…). | ||
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With : RZ (f) = real part of the zoomed spectrum (at frequency f) | With : RZ (f) = real part of the zoomed spectrum (at frequency f) | ||
IZ (f) = imaginary part of the zoomed spectrum (at frequency f) | IZ (f) = imaginary part of the zoomed spectrum (at frequency f) | ||