Full AFR. Step 2

Specify the Standards

Use the selctions in this tab to specify how the thru-standard characterization is measured or loaded. Depending on your selections in step 1. Describe Fixture, a specific drawing appears in this tab that shows your fixtures.

Open and Short fields

Select the type of calibration standards that you will connect to the fixture's ports during the AFR procedure. Choose Open, Short, or both Open and Short. These selections appear next to the picture that represents your fixtures. For example, the following picture represents a 2X Thru for a two-port single-ended DUT. The picture shows that the left and right fixtures are mirror images of each other and have the same S-parameters. The cascaded combination of the two fixtures are Fixture A + Reversed Fixture A, or A'. If both halves are identical and you do not have a 2X Thru, only Fixture A measurements are necessary.

The following picture shows how the tab might look for multiport differential AFR.

2X Thru

Select this field when a two-port single-ended or a four-port differential AFR is performed using a 2X Thru standard. Clear this selection if you are using separate 1X Thru fixtures, also known as one-port AFR.

Fixtured DUT

The Fixtured DUT field is shown and selected if, in step 1. Describe Fixture, you selected My characterization fixture ≠ DUT measurement fixture. This field is shown in the following picture. In this case, even though your 2x thru is different from the actual DUT measurement fixture, the 2x thru will be used to characterize the fixture. The procedure improves accuracy by performing gating on the DUT measurement fixture that accounts for the fixture input reflection (S11a) and output reflection (S22b).

Advanced Settings

Use the Advanced Settings fields to describe any additional length between the halves of a 2X Thru or added to either of left or right fixtures.

My Thru fixture has:

• Known thru length. Enter the length in nanoseconds. A simulated length in the diagram between the two halves of the 2X Thru is shown. If the electrical length of the Thru standard is identical to the test fixture, then make no changes to the default settings (0 ns).
• Unknown thru length computed using reflects. This setting requires the two halves of the Thru fixture be characterized separately with a reflect standard.
• Unknown thru length computed using fixtured DUT measurements. This setting requires an additional characterization of the Fixture + DUT.