Concepts and Features
R&S
®
ZNC
77
User Manual 1173.9557.02 ─ 13
r
mech
r
mech
L
c
L
Length
Electrical
;
Delay
The default delay is 0 s, the default step width is 1 ns, corresponding to a step width
of 299.792 mm for the electrical length. The relations hold for one-port and 2-port
standards.
●
Z
0
is the "Characteristic Impedance" of the standard. If the standard is terminated
with Z
0
, then its input impedance is also equal to Z
0
. Z
0
is not necessarily equal to the
reference impedance of the system (depending on the "Connector Type") or the ter-
minal impedance of the standard. The characteristic impedance of the standard is
only used in the context of calibration.
The default characteristic impedance is equal to the reference impedance of the sys-
tem.
●
The "Loss" is the energy loss along the transmission line due to the skin effect. For
resistive lines and at RF frequencies the loss is approximately proportional to the
square root of the frequency.
In Agilent mode the "Offset Loss" is expressed in units of Ω/s at a frequency of 1 GHz.
The following formula holds for two-port standards:
s
delay
dB
Z
dB
Loss
s
Loss
Offset
/
/
3429
.
4
/
/
/
/
0
The conversion formula for one-port standards has an additional factor ½ on the right-
hand side. The reason for this factor is that the Loss in dB accounts for the attenuation
along the forward
and
the reverse path (no matter how often the wave actually prop-
agates through the line), whereas the "Offset Loss" is proportional to the attenuation
of the line.
To determine an offset loss value experimentally, measure the delay in seconds and
the loss in dB at 1 GHz and use the formula above.
The default "Loss" or "Offset Loss" is zero.
The impedance for waveguides is frequency-dependent. If a waveguide line type is
selected in the "Cal Connector Types" dialog, the "Char. Imp." field is disabled and indi-
cates "varies" instead of a definite impedance value. Moreover no "Loss" or "Offset
Loss" can be set.
Offset parameters and standard types
Offset parameters are used to describe all types of standards except the Sliding Match
and the Attenuation.
●
The Sliding Match is a one-port standard with variable load parameters (sliding load)
and unspecified length. The reference impedance is fixed and equal to the charac-
teristic impedance of the connector type. No load and offset parameters need to be
set.
●
The Attenuation is a two-port standard which is fully matched in both directions (the
reflection factor at both ports is zero). No load and offset parameters need to be set.
Calibration
