PIM Test Tools
Passive Intermodulation (PIM) Test
What is Passive Intermodulation (PIM)
|Passive Intermodulation (PIM) occurs when two or more high power RF signals encounter non-linear electrical junctions or materials in the RF path.|
These non-linear junctions behave like a mixer causing new signals to be generated at mathematical combinations of the original RF inputs.
In the figure below, f1 and f2 represent two Tx frequencies present at a typical cell site and ± m•f1 ± n•f2 are the PIM signals generated by those Tx frequencies.
When these PIM signals fall in the receive (Rx) band of the cell site, the noise floor rises resulting in increased dropped calls, reduced data transmission rates and decreased system capacity.
The impact of PIM on the network performance can be severe, especially for wideband systems such as UMTS or LTE and on shared transmission sites.
PIM Sources at Cell Site
The primary sources of non-linear junctions at a cell site are inconsistent metal to metal contacts in high current density regions such as inside transmission lines, inside RF components or outside the system but in the main beam of the antenna. Clean metal surfaces with high contact pressure generally behave in a linear manner and do not generate PIM. Where there is loose contact between metal surfaces, a non-linear relationship develops between the applied voltage and the resulting current flow across the joint causing PIM to be generated.
PIM Master 1800MHz DCS1800 Portable PIM Analyser EGSM900 Portable PIM Analyser LTE800 Portable PIM Analyser DCS1800 Passive Intermodulation Tester UMTS PIM Tester 2100MHz with RTF Portable PIM Analyser EGSM 900MHz PIM Tester Nardalert S3 Personal Radiation Monitor
PIM Master 1800MHz
DCS1800 Portable PIM Analyser
EGSM900 Portable PIM Analyser
LTE800 Portable PIM Analyser
DCS1800 Passive Intermodulation Tester
UMTS PIM Tester 2100MHz with RTF
Portable PIM Analyser
EGSM 900MHz PIM Tester
Nardalert S3 Personal Radiation Monitor
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PIM Test Equipment
PIM test equipment works by transmitting two high power signals into the line or device under test. If the test signals encounter a non-linear junction mixing occurs causing the PIM frequencies to be generated. The PIM signals travel in all directions from the point of generation. In a coaxial system this means they travel out toward the antenna as well as back in the direction of the PIM test equipment. The PIM test equipment measures the magnitude of the PIM signal generated by the test signals and displays this information to the test operator.
IEC 62037 is the international standard for PIM testing and gives specific details as to PIM measurement setups. This standard (IEC 62037) specifies the use of two +43 dBm (20W)tones as the industry standard test power for PIM testing. This power level has been used by RF equipment manufactures for more than a decade to establish PASS / FAIL specifications for RF components.
If you want to know more about PIM Testing. Watch this useful video:
You can also click here download a useful PDF on Range to Fault Technology.
And for a bit more information:
PIM Measurement Frequency
PIM test equipment is used to find and eliminate non-linear junctions and materials at the cell site. The specific test frequencies used to identify these defects are not critical as long as the following criteria are met:
Some test equipment provides the ability to sweep the two transmit frequencies across a range of frequencies during the test. Swept frequency modes will transmit frequencies outside of the operator’s licensed spectrum. For this reason, swept frequency modes should only be used to test systems terminated into a low PIM load.
Dynamic vs. Static PIM Testing
During a PIM test, all components and interconnections on the line should be subjected to light mechanical stress or “dynamic” test conditions. If the component or RF connector has loose internal connections or internal debris that can result in increased PIM (as identified during dynamic testing) there is a high probability that the condition will present itself in the future and invariably at the most inconvenient time.
Tap Test Guidelines
Antenna PIM Measurement
When performing a PIM test, high power RF energy will be radiated from the antenna. Care must be taken to ensure that people near the test are not exposed to RF field levels in excess of the maximum allowable exposure limits and that the test environment must be free of PIM sources that could invalidate the results.
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