7-33
Operating Concepts
Electrical Delay
Electrical Delay
The softkey adjusts the electrical delay to balance the phase of the
test device. This softkey must be used in conjunction with or
(with cut-off frequency) in order to identify which type of
transmission line the delay is being added to. These softkeys can be accessed by pressing
the key.
Electrical delay simulates a variable length lossless transmission line, which can be added
to or removed from a receiver input to compensate for interconnecting cables, etc. This
function is similar to the mechanical or analog "line stretchers" of other network analyzers.
Delay is annotated in units of time with secondary labeling in distance for the current
velocity factor.
With this feature, and with (refer to “Setting the Electrical Delay”
on page 1-37), an equivalent length of air-filled, lossless transmission line is added or
subtracted according to the following formula:
Once the linear portion of the test device's phase has been removed, the equivalent length
of the lossless, transmission line can be read out in the active marker area. If the average
relative permittivity (ε
r
) of the test device is known over the frequency span, the length
calculation can be adjusted to indicate the actual length of the test device more closely.
This can be done by entering the relative velocity factor for the test device using the
calibrate more menu. The relative velocity factor for a given dielectric can be calculated by:
assuming a relative permeability of 1.
Scale Ref
→
Length meters()
Φ
Freq MHz()1.20083×
()
-------------------------------------------------------------------=
Velocity Factor
1
ε
r
--------=
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