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QPHY-SAS3 Software Option

Figure 16 - Common Mode RMS Voltage Results

In the Measure section:

• CM Offset (P1) is the common mode offset. This is measured by taking the mean of the common

mode trace. This is the measured value of Tx – Common Mode Offset (5.3.2). This test is

informational only.

• CM RMS (P2) is the common mode RMS voltage. This is measured by taking the RMS of the

common mode trace. This is the measured value for Tx – CM RMS voltage (5.3.2). This value

must be less than 30mV in order to pass this test.

Tx 5.3.3 Common Mode Spectrum (CJTPAT)

The purpose of this test is to verify that the common-mode spectrum is within the specification limits. After

the completion of the Common Mode RMS Voltage test the oscilloscope is in the following configuration:

Figure 17 - Oscilloscope Configuration after the Common Mode Spectrum Test

Shown on this screen:

• F5 is the Common Mode Spectrum trace. This is the FFT of the common mode trace displayed in

dBmV/MHz. The common mode trace is calculated by summing the differential inputs and

dividing by 2.

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Teledyne-lecroy QPHY-SAS3 Manuale Utente Pagina 25