iftbis()

iftbis( axis )

Perform inverse of complex-to-real Fourier Transform on data.
This command is the basic step for Hilbert transform. The Hilbert
transform is the mathematical operation which transform the real
part of a causal spectrum (for instance an NMR spectrum) to its
imaginary part.

The command sequence :

 

iftbis ()

phase(90, 0)

ftbis()

realises this operation, thus permitting to regenerate the imaginary
part of the signal, when it is lost for some reasons.
A more usefull operation consists in transforming a real
(unphasable) spectrum to a complex (phasable) spectrum.
either on place (twice as less points in the real part) (1D syntax):

 

iftbis()

ft()

or with a constant resolution (zerofilling once)

 

iftbis()

chsize(get_si1_1d()*2) 

ft()

see also : ft

NPK Documentation, version 0.995 - 2009-10-14