Storing Trace

Memories

Viewing Normalized Parameters

If you view the response of a short circuit, notice that:

•Changing Port 1 attenuator has negligible effect on S11 marker reading

•Changing Port 2 attenuator has negligible effect on S22 marker reading

This is due to the way the attenuators are paired. Both the reference and the test signal are changed by approximately equal amounts.

When viewing S21 or S12, however, changing Port 1 or Port 2 attenuators offsets the marker reading by the difference value between Port 1 attenuator and Port 2 attenuator.

To compensate for the main frequency response effects due to changing the attenuators, use the HP 8510C trace memories and trace mathematics function, as explained below:

1.Connect the thru used for calibration and set the port attenuators to the value used for device measurement.

2.Recheck the user parameter levels, then press PARAMETER [S21].

3.Press MENUS [DISPLAY], then {DATA AND MEMORIES}.

Press DISPLAY: {DATA-->MEMORY n} to store the S21 trace in default trace memory 1. This trace represents the frequency response difference between the S21 signal path calibration and the measurement.

4.Press PARAMETER [S12], then press the following DISPLAY: menu keys:

{SELECT DEFAULTS}

{DEFAULT to MEMORY: 2} {DATA-->MEMORY 2}

The S12 trace is now stored in trace memory 2. This trace is the frequency response difference of the S12 signal path between calibration and measurement.

Use the traces stored in memory 1 and memory 2 to normalize the corrected data to the new levels after the attenuation is changed. The next example uses normalization for S21 or S12, only. To view the corrected parameters:

1.Press MENUS [DISPLAY], then {DATA AND MEMORIES}

2.Press PARAMETER [S11] and view the S11 measurement.

3.Press PARAMETER [S22] and view the S22 measurement.

4.Press PARAMETER [S21], then the following DISPLAY: menu keys:

{SELECT DEFAULTS} {DEFAULT to MEMORY: 1} {MATH ( / ) }

HP 8517B S-Parameter Test Set Manual 3-11