Overview of PIM test calibrations with its improvement by tunable PIM standard

The traditional calibration method for passive intermodulation (PIM) measurement is realized using a tested low PIM load or several PIM fixed value standards to check if the PIM test loop (excluded DUT) has a low PIM status or equal PIM response. However, as the potential nonlinearities are widely spread in all kinds of microwave devices, the PIM calibration just based on the low PIM statue of whole test loop or several fixed reference values is not sufficient. A tunable PIM source based calibration method appears, it can provide a series of continual tunable PIM references to verify all the test values in the whole test range. In this work, several techniques to generate tunable PIM reference are summarized and introduced. All these methods are developed targeted to the specific demands for PIM measurement, these techniques are able to provide weak PIM level that smaller than -112 dBm @ 2×43 dBm, while the tunable PIM phase reference is achieved furthermore.