Teledyne LeCroy QPHY-10GBase-T - Manual (Page 28)

QPHY-10GBASE-T RL Test Configurations
All Tests
There is only one configuration to choose from. This configuration enables users to perform the
fixture calibration and MDI return loss test.
QualiPHY will indicate which ports to connect to on the TF-10GBASE-T fixture (e.g. A+/A-).
QPHY-10GBASE-T RL Tests
PreTest – Fixture Calibration
The purpose of this is to perform a second tier calibration to adjust the reference plane for the
impedance measurements.
The TF-10GBASE-T fixture kit includes a board with differential SHORT, OPEN, LOAD
standards. The Fixture Calibration step makes measurements of these standards in order to
generate “second-tier calibration” files (.L12T extention), one for each of the differential pairs.
When performing the MDI Return Loss test, the SPARQ will use the second-tier calibration file,
which automatically places the reference plane for the S-parameter measurement at the pins of
the receptacle on the DUT. QualiPHY will show pop-up dialogs indicating which cal standard to
connect to. The output of the fixture calibration steps are saved to file:
C:\LeCroy\SPARQ\SPARQ\SecondTierCalibration\XGBT Fixture cal A.l12t
C:\LeCroy\SPARQ\SPARQ\SecondTierCalibration\XGBT Fixture cal B.l12t
C:\LeCroy\SPARQ\SPARQ\SecondTierCalibration\XGBT Fixture cal C.l12t
C:\LeCroy\SPARQ\SPARQ\SecondTierCalibration\XGBT Fixture cal D.l12t
Test 1 – MDI Return Loss
The purpose of this test is to verify that the differential impedance at the MDI for each
transmit/receive channel is within the conformance limits as defined in section 55.8.2.1 of the
IEEE 802.3-2008 specification.
This test uses Test Mode 5.
W HAT I S M EASURED
The MDI Return Loss test measures the S11 S-parameter and converts it to an impedance
profile.
T EST M ETHODOLOGY
Each of the four differential pairs in the Ethernet cable are tested individually. Each is connected
in turn to a balun using supplied matched cables, and the balun is connected to the SPARQ
network analyzer. The SPARQ makes a 1-port measurement, effectively yielding the SDD11 of
the differential pair under test. (Since the SPARQ input is already differential, the S11 result of
the SPARQ is the SDD11 of the differential pair.) The reference plane for this measurement is at
the pins of the DUT’s receptacle by virtue of the second-tier calibration .L12T file that was
performed in the previous step. The software sets the appropriate L12T file for use in the
SPARQ software (Calibration dialog)
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