4. Press the Measurements main menu key and then press the PIM vs. Time submenu key.
5. Verify that the Output Power is set to the desired power level.
Intermodulation Distortion
The intermodulation distortion (IMx) is a mathematical function of F1 and F2.
3rd Order Intermodulation (IM3) = 2F1 – F2 or 2F2 – F1 5th Order Intermodulation (IM5) = 3F1 – 2F2 or 3F2 – 2F1 7th Order Intermodulation (IM7) = 4F1 – 3F2 or 4F2 – 3F1
Example Intermodulation Calculation
Finding IM3 when F1 = 1930 MHz and F2 = 1990 MHz:
IM3 = 2F1 – F2 = 2(1930) – 1990 = 1870 MHz
or
IM3 = 2F2 – F1 = 2(1990) – 1930 = 2050 MHz
The PIM Master uses 1870 MHz (low‑side IMx) as the center frequency. The PIM Master always uses the lower IMx value and does not set to the high‑side IMx frequency, except for instruments that are designed to measure the high‑side product (the MW82119A‑0700, for example).
If the IMx frequency does not fall within one of these bands, then the PIM Master produces an audible tone.
6. Press the Carrier F1 submenu key to enter the frequency of Carrier F1 by using the keypad or the Arrow keys. When entering a frequency by using the keypad, the submenu key labels change to GHz, MHz, kHz, and Hz. Press the appropriate unit key.
8. Press the Intermod Order submenu key so that the desired intermodulation frequency order to be viewed is underlined. 3rd order is the most commonly chosen measurement .
Note
The PIM Parameters screen (press the PIM Aid submenu key) displays the IM frequencies for the F1 and F2 frequencies that are entered.
Amplitude Setup
9. Press the Amplitude main menu key to display the Amplitude menu.
10. Press the Reference Level submenu key. The numeric value and units turn red indicating that the settings are ready for editing. Enter the desired reference level by using the keypad or the Arrow keys. Press Enter.
11. Press the Scale submenu key to change the division of the graticule to a setting other than the default value of 10 dBm.
12. Press the Auto Range submenu key so that On is underlined. This allows the reference level to be adjusted automatically.
13. Press the Amplitude Tone submenu key to have the PIM Master broadcast a tone. The frequency of the tone increases as PIM level increases.
Power and Display Setup
14. Press the Setup main menu key to display the Setup menu.
High Output Power and Low Output Power submenu keys are available for setting output power.
15. Press the High Output Power submenu key to set the output power range between 37 dBm and 46 dBm.
16. Press the Low Output Power submenu key to set the output power range between 25 dBm and 37 dBm.
17. Press Test Duration to set the number of seconds from 1 s to 1200 s.
18. Press the Trace Mode submenu key (if desired) to toggle between Fast and Low Noise modes. For additional information, refer to Trace Mode.
Calibration
If calibration is needed, refer to section Calibrating.
Sample Measurement
Sample Measurement with PIM at 1870.0 MHz
PIM problems can be intermittent and power sensitive. This is often the case when PIM problems first begin to appear. This can be due to light corrosion, to high traffic loading, or to changing weather conditions that are activating environmental diodes. Using higher power levels can often force otherwise intermittent failures to become visible. Higher power levels may be required to find faults in a multicarrier system and to discover microscopic arcing in connectors.
In Figure: Sample Measurement with PIM at 1870.0 MHz, note that the instantaneous PIM levels are displayed in white numerals even though the PIM value exceeded the upper limit line setting during the measurement. The instantaneous measurement values turn red while the measurement is above the limit, but return to white while the measurement is below the limit. The peak PIM values are shown in red (and remain in red) because the measurement exceeded the limit at some time during the measurement.
PIM Summary Table
PIM Summary Information
1.
PIM Order
2.
Instantaneous PIM
3.
Peak PIM
4.
Transmit Frequencies
5.
Test Power Level
6.
RF ON Indicator
7.
Pass / Fail Indication (White = Pass, Red = Fail)
8.
PIM Frequency
In this example of the PIM Summary Table, the instantaneous PIM values (item 2) are displayed with white numerals, indicating that these values are below the upper limit value that was set for this measurement. The peak PIM values (item 3) are also displayed with white numerals, indicating that those values are within the upper limit value setting. If the measurement trace exceeds the upper limit line setting at any time during a measurement, then the peak values are displayed in red and remain red after the measurement is completed. The instantaneous PIM values (item 2) are displayed with red numerals only while the measurement exceeds the limit.
The RF ON indicator (item 6) is displayed in the PIM Summary Table only while the measurement is in progress, that is, while RF is being transmitted. The Test submenu key, in which the word Measure is underlined while the measurement is in progress, is also highlighted in red while RF is present.
Bar Graph of Instantaneous PIM
PIM versus Time
Note the PIM bar graph at the left edge of the sweep window. In this graph, the instantaneous PIM level is displayed in units of dBm by the red bar on the vertical axis. No limit was set for this particular measurement.
PIM Parameters Dialog Box
The PIM Parameters dialog box (Figure: PIM Parameters Dialog Box) is displayed by pressing the PIM Aid submenu key, which is available by pressing the Freq main menu key or the Setup main menu key. This dialog box displays the current carrier frequencies, power, and intermodulation products generated by the selected carrier frequencies. In addition, frequencies for F1 and F2 and the carrier power can be changed in this dialog box. Use the Arrow keys or the touch screen to scroll through the 3 settings (F1, F2, and Power). The chosen value changes color to indicate when the value is ready for editing. Then use the number keypad to enter a value. After editing the value, you must press the Enter key or the appropriate submenu key (MHz for frequency or Enter for power). The highlighting changes to indicate that the new value has been set. When all 3 settings are satisfactory, scroll to highlight the Continue button and press the Enter key, or use the touch screen to press the Continue button, or press the Back submenu key. To abort a setting, before pressing Enter or the MHz submenu key or the Enter submenu key, press the Esc key or an Arrow key, which allows you to enter a different value. Pressing the Esc key when no setting is pending returns the display to the previous menu. To abort a setting, before pressing Enter or the MHz submenu key or the Enter submenu key, touch the Continue button, which returns to the same previous menu as when pressing the Back submenu key.
