Digital Signal Processing Reference
In-Depth Information
SIGNAL PROCESSING: FPT (QUANTITATIVE) and FFT (QUALITATIVE)
Input Data : Time signal or Free Induction Decay, FID
2
1.5
Harmonic Exponentially Damped Oscillations
1
0.5
0
−0.5
−1
0
250
500
750
1000
1250
(i) Time (ms)
Output Data (Non−Optimal, Qualitative) ; Sum of Metabolites, No Components
Envelope Spectrum
15
10
5
0
5
4.5
4
3.5
3
2.5
2
1.5
1
(ii) Chemical shift (ppm)
Output Data (Optimal, Quantitative) ; Added Value : All Components
Envelope or Total Shape Spectrum (top)
15
Component Shape Spectra (bottom)
10
5
0
5
4.5
4
3.5
3
2.5
2
1.5
1
(iii) Chemical shift (ppm)
FIGURE 3.2
Time and frequency domain data in signal processing. Top panel (i): the
real part of the input FID (the same as in
Fig. 3.1
where the imaginary
part is also given). Middle panel (ii): absorption total shape spectrum (FFT,
FPT). Bottom panel (iii): absorption component (lower curve; FPT) and total
(upper curve; FPT, FFT) shape spectra. Panels (ii) and (iii) are generated
using both the real and imaginary parts of the FID.
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