Concepts and features
R&S
®
ZNA
141
User Manual 1178.6462.02 ─ 20
where Δt is the propagation time of the wave across the DUT, which often can be
expressed in terms of its mechanical length L
mech
, the permittivity ε, and the velocity of
light c. The product L
mech
· sqrt(ε) is termed the electrical length of the DUT and is
always larger or equal than the mechanical length (ε > 1 for all dielectrics and ε = 1 for
the vacuum).
4.4
Operations on traces
The R&S
ZNA can perform more complex operations on the measured traces. Some of
the operations, e.g. the time domain transform, require additional software options; see
Chapter 4.7, "Optional extensions and accessories"
The R&S
ZNA can also check whether the measured values comply with specified lim-
its and export trace data, using different file formats.
4.4.1
Limit check
A limit line restricts the allowed range for some or all points of a trace, i.e. for a certain
range of stimulus values. Typically, limit lines are used to check whether a DUT con-
forms to the rated specifications (conformance testing).
●
An upper limit line defines the maximum allowed values for the related stimulus
range.
●
A lower limit line defines the minimum allowed values for the related stimulus
range.
●
A ripple limit defines the maximum difference between the largest and the smallest
response value for the related stimulus range. A ripple limit test is suitable, e.g., to
check whether the passband ripple of a filter is within acceptable limits, irrespective
of the actual transmitted power in the passband.
●
A circle limit defines the acceptable values as a circular area within a complex dia-
gram.
A limit check consists of comparing the measurement results to the limit lines and dis-
play a pass/fail indication. An acoustic warning and a TTL signal at the User Port on
the rear panel (for test automation) can be generated in addition if a limit is violated.
Upper and lower limit lines are both defined as a combination of segments with a linear
or logarithmic dependence between the measured quantity and the sweep variable
(stimulus variable). Similar to this segmentation, ripple limits can be defined in several
ranges. The limit lines (except circle limits) can be stored to a file and recalled. Data or
memory traces can be used to define the segments of an upper or lower limit line.
Moreover it is possible to modify the upper and lower limit lines globally by adding an
offset to the stimulus or response values.
4.4.1.1
Rules for limit line definition
The analyzer places few restrictions on the definition of limit line segments.
Operations on traces
