Measuring and modeling package interconnects using vector network analyzers and time domain transforms

The design of electronic packaging interconnects requires precise knowledge of the RF performance in an end use environment. Separating the effects of test fixtures and measurement error from the actual interconnect performance has been a difficult prospect. Vector network analyzers have the capability of measuring the reflection coefficient, or return loss, of a device, then applying an inverse Fourier transform to obtain a time domain response of the device. This response, similar to a time domain reflectometer trace, can be manipulated to remove the unwanted responses of fixtures and transitions, generating a true picture of the desired interconnect frequency response. While this technique has been demonstrated using microwave network analyzers, it can be applied to lower cost RF network analyzers if care is used on designing and calibrating test fixtures.