NF FRA51615, Instruction Manual

Page: 203 / 306

5.9 Error correction
5
-
41
FRA 51615
5.9.5 Port extension
This correction function is used when making impedance measurements with two-port connections and
long cables. It corrects for the phase delay that occurs from propagation delay in cables.
Figure 5-22 Impedance measurement connection example (2-port connection)
This function is set with
【
Calibration
】－
[PORT EXTENSION]
. The values set are characteristic
impedance [Z0] (Ω) and electrical length [ELECTRICAL LENGTH] (m).
■ About the port extension function
•
This function is effective when the connection distance to the DUT is long (a few meters or more).
•
This correction applies to two-port connections. Applying this correction to other connection
configurations will increase error rather than reduce it.
•
When a standard impedance is available, the error correction method described in " 5.9.7 Load
correction " is recommended. Port extension correction provides an easy way to correct for phase delay
when a standard impedance is not available.
•
The electrical length setting for extension cables ( [ELECTRICAL LENGTH] ) is not the physical length
of the cable, but the electrical length (physical length × wavelength shortening rate). The wavelength
shortening rate of the RG-58A/u is 67%, but you should check the specifications of the cable that you
are using for more information.
•
Correction is not normally possible when using a cable that does not have a constant characteristic
impedance.
•
The port extension function normalizes the current amplitude (CH2 amplitude) to 1.0 (Arms). Corrected
results for the impedance/admittance values are obtained, but please note that the displayed values for
the voltage amplitude (CH1 amplitude) and the current amplitude (CH2 amplitude) differ from the
measured amplitude values.
FRA51615
1
2
～
Extension cable
DUT
Rsh
Z
Z'
2-port
connection Characteristic impedance = Z
0
Electrical length = L