States-TPPI
From NMR Wiki
States-TPPI technique achieves two effects for a given indirect dimension (say, dimension F1): (1) signal frequency discrimination and (2) displacement of the unmodulated artefact signal from an inconvenient location in the middle of spectrum to the edge.
(1) is achieved by recording two data sets at each t1 point - with orthogonal phases of the preparation pulse and same receiver phase - and storing them in separate memory locations. These two fid measurements yield one complex data point in F1.
(2) by inverting phase of the preparation pulse and the receiver each time when t1 is incremented (that is for subsequent complex points). Therefore, the artefact signal becomes modulated at the Nyquist frequency and appears in the spectrum at F1=±SW/2 Hz instead of 0 Hz, where SW is spectral width.
For example to get two sequential complex data points - one at the evolution delay t1 and the next one at evolution delay t1 + 1/SW four fid's are recorded:
| complex point # | fid# | evolution delay | phase of prep. pulse | receiver phase |
| 1 | 1 | t1 | x | x |
| 2 | t1 | y | x | |
| 2 | 3 | t1+1/SW | -x | -x |
| 4 | t1+1/SW | -y | -x |
The data is subsequently processed by the complex Fourier transformation.
