This chapter describes various methods for handling cases of non-insertable DUTs. In some coaxial cases, this can be handled with a special class of adapter removal calibrations. More generally, de-embedding can be used to remove the effects of fixtures or adapters required to execute the measurement. The de-embedding process itself will be covered in a later chapter but the means of evaluating the network to be de-embedded will be addressed here.
While it is usually desired to perform a 2-Port calibration with mating connectors of the same type, this is sometimes not possible based on the connectors of the device to be tested. Examples of this include:
• The DUT has one N port and one GPC-3.5 port
• The DUT has two female SMA ports and it is not desired to use a non-zero length thru
• The DUT has one fixtured port and one SMA port
• The DUT has one waveguide port and one coaxial port
What these examples share is that completing the through line between the effective test ports requires some kind of adapter or fixture. Since the adapter has some phase length, loss, and mismatch, its effects should be removed for a high quality calibration. Adapter removal is a utility to characterize this adapter and remove its effects from a calibration.
In the more general case of de-embedding, a means of determining the network to be de-embedded must be available. Techniques similar to adapter removal, that is a measurement using one or more calibrations, can be used to extract these parameters. As such network extraction can be viewed as a generalization of adapter removal.