Concepts and Features
R&S
®
ZNC
59
User Manual 1173.9557.02 ─ 13
f
deg
meas
g
360
,
The aperture Δf must be adjusted to the conditions of the measurement.
If the delay is constant over the considered frequency range (non-dispersive DUT, e.g.
a cable), then τ
g
and τ
g,meas
are identical and
c
L
t
f
d
t
f
d
mech
g
360
)
360
(
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).
3.4 Operations on Traces
The R&S ZNC 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 3.7, "Optional Extensions and Accessories"
The R&S ZNC can also check whether the measured values comply with specified limits
and export trace data, using different file formats.
3.4.1 Limit Check
A limit line is a set of data to specify the allowed range for some or all points of a trace.
Typically, limit lines are used to check whether a DUT conforms to the rated specifications
(conformance testing).
●
The "upper" limit line defines the maximum value for the trace points.
●
The "lower" limit line defines the minimum value for the trace points.
●
The "ripple" limit defines the maximum difference between the largest and the small-
est response value of the trace. 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.
●
The "circle" limit defines the acceptable values as a circular area within a polar dia-
gram.
A limit check consists of comparing the measurement results to the limit lines and display
a pass/fail indication. An acoustic warning and a TTL signal at the "USER PORT" on the
rear panel (for test automatization) can be generated in addition if a limit is exceeded.
Upper and lower limit lines are both defined as a combination of segments with a linear
dependence between the measured quantity and the sweep variable (stimulus variable).
Operations on Traces