Write/Read

About Time Domain

Description

Sets the way the PNA computes the DC value of the frequency-domain measurement. The correct DC value is required for inverse-FFT accuracy, and if not estimated properly, can cause distortions in the time-domain measurement in the form of an undesired slope in the waveform.

 VB Syntax

trans.Alignment = value

Variable

(Type) - Description

trans

A Transform (object)

value

(Enum As NATransformAlignment) - Choose from:

0 - naTransformAlignmentLegacy - The DC value is extrapolated using three data points. The transform offset is calculated using the delay of the first frequency point. This is the same algorithm used in the HP 8510 network analyzer.

1 - naTransformAlignmentNormalize - The DC value is extrapolated using three data points. The transform offset is set to zero at t=0 minus six rise-times. This mode requires that a good S-parameter calibration has been performed, which can be verified by observing a flat time-domain response at t=0 when measuring a load located at the physical point corresponding to t=0. Setting the time domain trace to zero at a time before t=0 stabilizes the trace for determining impedances after time t=0, resulting in improved behavior compared to Legacy mode. This method is similar to that used with PLTS, and is very useful in determining the time-domain-transform response of transmission lines and printed-circuit-board characteristics.

Return Type

Enum

Default

0 - naTransformAlignmentNormalize

Examples

trans.Alignment = naTransformAlignmentNormalize  'Write

value = trans.Alignment  'Read

C++ Syntax

HRESULT get_Alignment(enum tagNATransformAlignment *pVal);

HRESULT put_Alignment(enum tagNATransformAlignment newVal);

Interface

ITransform3