Location of a source of passive intermodulation in a frequency selective device

Test apparatus for identifying a location of at least one PIM (passive intermodulation) source in a frequency selective device, the test apparatus comprising:

• a signal generator configured to generate an excitation waveform for application to the frequency selective device;
• a receiver configured to receive PIM produced in the frequency selective device in response to the excitation waveform;
• and
• a circuit comprising a processor configured to:
• measure a PIM response signature of the frequency selective device, the PIM response signature being a characteristic of the PIM received by the receiver;
• produce comparison results by comparing the measured PIM response signature with each of a plurality of example PIM response signatures, each of the plurality of example PIM response signatures corresponding to a characteristic of PIM expected for a respective location of a PIM source in the frequency selective device;
• and
• identify the location of the at least one PIM source within the frequency selective device on the basis of the comparison results.