Filter
Top Products
11
Note
In some cases (when the phase response is linear
with respect to frequency) the response of an open
can be modeled as an equivalent “incremental”
length.
This method will serve as a first order approxima-
tion only, but can be useful when data or stan-
dards for the above modeling techniques are not
available.
For the waveguide example, this parameter is not
addressed since opens cannot be made valid stan-
dards in waveguide, due to the excessive radiation
loss and indeterminant phase.
Short circuit inductance L
0
, L
1
, L
2
and L
3
If the standard type selected is a ‘short,’ the L
0
through L
3
coefficients are specified to model the
phase shift caused by the standard’s residual
inductance as a function of frequency. The reflec-
tion coefficient of an ideal zero-length short is 1 at
180° at all frequencies. At microwave frequencies,
however, the residual inductance can produce
additional phase shift. When the inductance is
known and repeatable, this phase shift can be
accounted for during the calibration.
Figure 3. Time domain response of open at the end of
an airline
2πf (∆length)
c
∆∅(radians) =