Type C is the most complete, dual fixture extraction approach offered in the VNA. It requires full 2-Port calibrations at two sets of reference planes but can fully determine the S-parameters of two networks independently.
Consider the diagram in NETWORK EXTRACTION dialog box (above in Figure: NETWORK EXTRACTION Dialog Box - 2-Port VNAs). A calibration is required at the outer reference plane set and the inner reference plane set. The outer calibration can usually be done coaxially (or some other well-defined media) depending on the networks involved. The inner calibration is often more complicated and may be board- or wafer-level (and may require the user create calibration standards). Assuming these calibrations are possible, then the S-parameters of Network 1 and Network 2 can be found.
Network Extraction Process Diagram for Type C Networks
1. Test Port 1
2. Test Port 2
3. Network 1 attached to Test Port 1
4. DUT attached to Network 1 (on left) and Network 2 (on right)
5. Network 2 attached to Test Port 2
6. Outer Reference Plane 1
7. Inner Reference Plane 1
8. Outer Reference Plane 2
9. Inner Reference Plane 2
Two port calibrations at two different reference plane sets are used to extract the S-parameters of the intervening networks (often test fixtures). The dialog for loading the two calibrations is shown in NETWORK EXTRACTION [Extract Two 2-Port Networks (Type C)] dialog box below.
NETWORK EXTRACTION Dialog Box - Extract Two 2-Port Networks - Type C
As before, the two calibrations are performed and the setups saved, typically as an active channel CHX file type.
Some conditions:
• The two calibrations must be full 2-Port cals and must have the same frequency lists.
• After extraction is performed, a file dialog will appear allowing the user to indicate where the S2P files should be stored.
• The networks are assumed to be reciprocal.
Unlike Types A and B, this method determines the two fixture halves completely and independently. As a trade-off, a complete set of standards at the inner plane are now required. Algorithmically, this type is very similar to Type A except two networks are processed simultaneously. If the inner cal standards can be successfully made/acquired, the inner match values extracted will typically be more stable than those acquired with a Type B analysis for the reasons discussed in the previous section.
