When testing, cables are connected and disconnected many times. In order to save wear on the PIM test port cables and adapters, Anritsu recommends removing the O-rings. This allows getting a sufficiently tight connection without unnecessary stress on the connectors. In the field, O-rings are important to maintain connection integrity over long time periods. Connections must be torqued to specifications in order to ensure that they prevent water intrusion.
During your test, if the DUT connector has an o‑ring, leave it in place and tighten to the correct torque.
If calibration was performed on the instrument test port, then you must next verify the PIM performance of the test cable.
1. Connect a test cable to the PIM Master and terminate the other end with a Low PIM Load.
2. From the Measurements Menu, press the PIM vs. Time submenu key followed by the Test submenu key so that Measure is underlined.
3. During the test, flex the test cable and verify that the PIM level of the test cable and the Low PIM Load are at least 10 dB below the pass / fail criteria for the DUT.
If the test cable fails, inspect the connections to ensure that they are clean and tight. If poor performance persists, then repeat the calibration process.
4. If the PIM level of the setup is within specification, then disconnect the Low PIM Load and connect the test cable to the DUT for a PIM measurement.
Checking for External Interference
Before performing a PIM test on an antenna system, verify that external interference is not present at the selected IM frequency.
1. Connect a test cable from the PIM Master to the DUT.
2. Press the Measurements main menu key and then press Noise Floor to open the Noise Floor submenu.
3. From the Noise Floor submenu, press the Test submenu key so that Measure is underlined. This will perform a Noise Floor - Time View measurement.
4. Verify that the external noise level at the selected IM frequency is below the required system pass / fail threshold for PIM.
5. If high noise is detected, press the Noise Floor Spectrum View submenu key. If a calibration has not already been performed for this feature, press the Start Cal Spectrum View submenu key and follow the on-screen instructions.
6. Press the Test submenu key so that Measure is underlined. This will perform a swept noise floor measurement to help identify which frequencies in the uplink band are clear of interference. Marker 2 automatically shows the location of the current IM frequency.
Making PIM Measurements
1. Press the Measurements main menu key and then press one of the measurement submenu keys (PIM vs. Time or Swept PIM).
2. From the Measurements menu, press the Test submenu key so that Measure is underlined.
3. During the test, tap connectors and the antenna.
Note: Set the test duration time so that you can tap all desired areas.
4. After the measurement is complete, press the Save Measurement submenu key, provide an appropriate name, and save the measurement.
Note
The PIM Master continually monitors Return Loss at the two PIM test frequencies while performing a PIM test. If the Return Loss exceeds –6 dB, then the PIM test will be terminated, and a warning message will appear saying, “Warning! High Reflection from measurement path!”
If this message appears, use a DTF measurement (using Option 331 or a Site Master) to identify the location of the high reflections.
An option exists to by-pass the high reflection warning and continue testing into a high return loss system. The PIM value measured may not be accurate when high reflections are present. This option should be exercised by experienced users for troubleshooting only.