Result data from a gnt analysis is saved in the psf data and can be accessed graphically with the Results Browser or through SKILL functions.

The Direct Plot Form is not supported.
Only the psf data format is supported.

Naming of decomposition results


The NGNT decomposition results, the first-level transfer function and the lower-level transfer functions are calculated and named in an interpretation independent fashion. For example, in the canonical gnt formulation, Hy refers to the transfer function with all vy and iy (from all the probes) nulled, while Hx is the transfer function with all vx and ix nulled. Return ratios are named T1, T2, T1_2, ... and similar for null return ratios.


For 2GFT, NEET and 2CT, the names are mapped to more meaningful names, as these theorems are associated with a desired interpretation of the decomposition result. In addition, useful combinations of lower-level transfer functions are included.

AnalysisMapped names
 2GFT  Hinf, H0, T, Tfwd, Trev, Tvfwd, Tifwd, Tvrev, Tirev, Tn, Tnfwd, Tnrev, Tnvfwd, Tnifwd, Tnvrev, Tnirev, D, Dn, Kd, Kn, Tm
 1EET  Href, Hopref, T, Tn, D, Dn
 2CT  Hv, Tv, Dv, Hi, Ti, Di
 NEET  Href, Hopref, T1, T2, T1_2, T2_1, ... , Tn1, Tn2, Tn1_2, Tn2_1, ... , D, Dn
 NGNT  no name mapping
  • Tm, Mason's loop gain, equals (Tfwd + Trev) and is minus the loopgain that results from a stb analysis when the loop based algorithm is used in a single-loop feedback system, with the same reference node (stb's localgnd option).
  • For nested 2GFT analyses, the total Mason's loop gain Tmtot is calculated when the the appropriate option is selected. This is used the check stability in multiple-loop feedback systems.
  • H0 is not equal to Hy

MIMO systems

When multiple source instances and/or multiple outputs are entered in the Choosing analyses form, all possible transfer functions are calculated. The transfer functions are name Hij (e.g. H11, H21) and their decomposition appears in directories in the psf data. By default, SISO system result naming is simplified.

Accessing data with the Results Browser

The decomposition results appears in the PSF data and can be accessed with ViVa's Results Browser. The following picture shows the results of a 2GFT analysis.

gft result in browser

Results from nested results are saved in the data hierarchy and can be accessed as such as the next image shows. The dot "." is the separator between hierarchy levels. For example, when a 1EET is nested in a 2GFT, Tifwd.Href refers to the forward current loop gain when the selected extra element vanishes.

nested eet results

For more information about the Results Browser, see the Virtuoso Analog Design Environment XL User Guide.

Accessing data through SKILL functions

Result data can be retrieved with the function getData(), for further processing in the calculator, outputs or ADE XL test bench. For example: getData(?result "gnt" "Hinf.Tvfwd"). See the OCEAN Reference for further information.