Time Domain Controls; Gating Controls - Agilent Technologies N4413A User Manual

Performing Time Domain Measurements
Using the Multiport Test System for Time-Domain Measurement and Analysis

Time Domain Controls

Radio buttons allow selection of impulse or step response. When step response is chosen on a
reflection parameter, the data can also be displayed as impedance rather than a reflection
coefficient. Linear (Real) or logarithmic (Log Mag) scales can also be selected.
Fill-in forms allow the time window to be further customized. The units for the start- and
stop-points are specified in either time (nS) or distance (cm), depending on the setting of the
radio button. With distance selected, you may also specify a velocity factor.

Gating Controls

The controls for gating the time domain response provide the ability to remove the effect of a
particular circuit element mathematically. To add a gate, first choose the gate type. An 'Ideal'
gate replaces the gated section with an ideal transmission line having the same electrical
delay as the section that is removed. A 'Zero Length' gate removes the gated section and
effectively shortens the structure. Then select Add Gate.
When Add Gate is selected, a dialog box appears to allow the start- and stop-points of the
gate to be defined.
Up to 10 gates can be added. When using multiple gates, 'Ideal' and 'Zero Length' gates are
highlighted differently for easy identification. The gates are numbered sequentially from left
to right. For example, to delete the left-most gate, set the Delete Gate box to 1 and click on
the Delete Gate button. The next gate then becomes gate number 1.
Once a gate has been defined, its position can be adjusted. The start-point can be moved with
the end-point fixed, the end-point can be moved with the start-point fixed, or the segment can
be shifted along the trace. This is accomplished by selecting the gate (by its number), and
clicking on the right or left soft arrow keys (not the keyboard).
By observing the original frequency domain response and the transformed frequency domain
response, the effect of the gating operation on the S-parameter data can be seen.
92 Chapter 4