30
S Parameter Mode
The MultiLane DSO is now capable of measuring insertion loss S-parameters.
Depending on how the DSO is connected, the user should be able to measure either of S21 dd, S12
dd, S21, S12, S43, S34, etc.
The only difference between all the above is:
1.
Single ended vs. differential connection.
2.
The direction in which the DUT is connected for S-param capture.
3.
The ports in use when connecting the DUT via a single ended connection.
The approach used consists of the following steps:
1.
Define Circuits:
a.
Main Circuit: Contains the DUT whose S-parameters are to be captured.
b.
Reference Circuit:
i.
Excludes the DUT whose S-parameters are to be captured.
ii.
Is as identical as possible to the Main Circuit, except for the DUT.
iii.
May require an additional component, such as a through, to be placed
in the location of the DUT to close the circuit.
2.
Set up the PPG:
a.
PRBS 7 or 9, PRBS9 is recommended.
b.
Maximum bit-rate possible (For maximum frequency range in the result)
c.
Cleanest possible Eye: This sometimes translates to maximum amplitude to
maximize SNR. However, be careful not to exceed the maximum amplitude
supported by the MultiLane DSO without using attenuators.
Kindly note PPG settings and amplitudes should not be altered after this point.
3.
Capture the reference signal: when having the optimal PPG settings as described
above, and with the reference circuit connected, run the DSO S-Parameter Setup
Wizard to capture reference data.
4.
Without altering any of the PPG settings, connect the main circuit, simply connect the
DUT where needed to switch from
Reference Circuit
to
Main Circuit
, and run in S-
parameter mode, the S21 insertion loss result will be visible.
For a constant PPG Source Signal, S21 Is calculated using the equation:
Frequency Response of DUT = FFT (Main Circuit Signal) / FFT (Reference Circuit Signal)
5.
Insertion loss can be saved in external .S21 or .DsoCirc files. These files contain both
magnitude and phase information; however, phase information is not accurate in the
