Measurements, Testing, and Calibration Additional Practical Test Questions Informational

What is the recommended test procedure for verifying the intermodulation performance of a passive component?

Q: What PIM level is acceptable?

Industry standards: IEC 62037: specifies PIM testing at 2 × 43 dBm (20 W per carrier). Does not specify a pass/fail threshold (this is application-specific). Typical requirements: base station antenna: PIM less than -150 to -153 dBc (at 2 × 20 W). RF connectors (7/16 DIN, 4.3-10): PIM less than -155 to -165 dBc. Cables and jumpers: PIM less than -155 to -160 dBc. Diplexers/filters: PIM less than -150 to -155 dBc. Lower PIM (more negative dBc) is better. The requirement depends on: the receiver sensitivity, the frequency separation between TX and RX bands, and the system architecture.

Q: What causes high PIM?

The most common causes: loose connectors (the most frequent PIM source in installed systems; torque the connector to specification). Corroded contacts (oxidation creates metal-oxide-metal junctions; clean or replace). Dissimilar metals (galvanic contact between different metals creates nonlinear junctions; use the same metal at all RF contacts). Contamination (metal shavings, dust, flux residue; clean all RF surfaces before assembly). Ferrous materials (steel screws, nickel plating near the RF path; use non-ferrous materials). Damaged components (bent or cracked contacts, scratched surfaces). Prevention: use PIM-rated connectors (7/16 DIN, 4.3-10), silver-plated contacts, proper torque, and clean assembly procedures.

Q: How do I troubleshoot PIM?

Troubleshooting high PIM in an installed system: systematic isolation (disconnect the antenna and terminate the feeder cable; if PIM disappears: the antenna is the source; if PIM remains: the cable or connectors are the source), tap test (gently tap each connector and component while monitoring PIM; a PIM source will show PIM variations when mechanically disturbed), and distance-to-PIM (some PIM analyzers can measure the distance to the PIM source using time-domain analysis; the round-trip delay reveals the location of the nonlinear junction in the cable run). Common fixes: re-torque connectors. Clean contacts with IPA (isopropyl alcohol) and lint-free wipes. Replace damaged connectors.

The recommended test procedure for verifying the intermodulation performance of a passive component (PIM, Passive Intermodulation) detects the generation of spurious intermodulation products by nominally linear passive components (connectors, cables, filters, antennas) when excited by two or more high-power carrier signals. PIM is a critical concern in cellular base stations and satellite systems where: two high-power transmit signals (e.g., +43 dBm each) pass through passive components, and the 3rd-order intermodulation products (2f1-f2 and 2f2-f1) can fall in the receive band, degrading the receiver sensitivity. The test procedure: use a PIM analyzer (a dedicated instrument with two high-power RF sources and a sensitive receiver): commercial PIM analyzers: Kaelus iPA, Rosenberger PIM Master, Anritsu PIM Master MW82119B. Set the two test frequencies (f1 and f2) to the transmit band of the system (e.g., for LTE Band 1: f1 = 2110 MHz, f2 = 2170 MHz). Set the test power level (typically +43 dBm (20 W) per tone, matching the base station transmit power; the IEC 62037 standard specifies 2 × 20 W carriers). Connect the device under test (DUT) between the PIM analyzer's output and a matched termination (a low-PIM load). Measure the 3rd-order PIM products at 2f1-f2 and 2f2-f1. The PIM level is expressed in dBm or dBc (relative to the carrier). Acceptable PIM levels: less than -150 dBc (or less than -107 dBm at 2 × +43 dBm carriers) for base station components.

Category: Measurements, Testing, and Calibration

Updated: April 2026

Product Tie-In: VNAs, Signal Generators, Power Meters

Passive Intermodulation Testing

PIM is caused by nonlinearities in passive components at the metal-to-metal contact interfaces, ferrous materials, and contamination. PIM testing is mandatory for: cellular infrastructure (all base station antennas, cables, connectors, and filters must meet PIM specifications), satellite systems (PIM in the antenna feed can block the satellite's receive band), and distributed antenna systems (DAS) in buildings.

PIM Sources

Metal junctions: Loose or corroded RF connector contacts create metal-oxide-metal junctions that act as diodes, generating intermodulation products
Ferrous materials: Magnetic materials (steel, nickel plating) near the RF current path exhibit nonlinear hysteresis, generating PIM
Contamination: Metal particles, flux residue, or moisture at RF contact surfaces cause PIM
Cold solder joints: A poor solder joint in the RF path acts as a nonlinear junction

PIM Test Parameters

3rd-order PIM frequencies: f_PIM3 = 2f₁ - f₂ and 2f₂ - f₁
PIM level: typically < -150 dBc (relative to each carrier)
In dBm: P_PIM < P_carrier - 150 = +43 - 150 = -107 dBm
IEC 62037 standard: 2 × 20W (+43 dBm) carriers
Pass criterion: PIM₃ < -150 dBc (or as specified by standard)

Common Questions

Frequently Asked Questions

What PIM level is acceptable?

Industry standards: IEC 62037: specifies PIM testing at 2 × 43 dBm (20 W per carrier). Does not specify a pass/fail threshold (this is application-specific). Typical requirements: base station antenna: PIM less than -150 to -153 dBc (at 2 × 20 W). RF connectors (7/16 DIN, 4.3-10): PIM less than -155 to -165 dBc. Cables and jumpers: PIM less than -155 to -160 dBc. Diplexers/filters: PIM less than -150 to -155 dBc. Lower PIM (more negative dBc) is better. The requirement depends on: the receiver sensitivity, the frequency separation between TX and RX bands, and the system architecture.

What causes high PIM?

The most common causes: loose connectors (the most frequent PIM source in installed systems; torque the connector to specification). Corroded contacts (oxidation creates metal-oxide-metal junctions; clean or replace). Dissimilar metals (galvanic contact between different metals creates nonlinear junctions; use the same metal at all RF contacts). Contamination (metal shavings, dust, flux residue; clean all RF surfaces before assembly). Ferrous materials (steel screws, nickel plating near the RF path; use non-ferrous materials). Damaged components (bent or cracked contacts, scratched surfaces). Prevention: use PIM-rated connectors (7/16 DIN, 4.3-10), silver-plated contacts, proper torque, and clean assembly procedures.

How do I troubleshoot PIM?

Troubleshooting high PIM in an installed system: systematic isolation (disconnect the antenna and terminate the feeder cable; if PIM disappears: the antenna is the source; if PIM remains: the cable or connectors are the source), tap test (gently tap each connector and component while monitoring PIM; a PIM source will show PIM variations when mechanically disturbed), and distance-to-PIM (some PIM analyzers can measure the distance to the PIM source using time-domain analysis; the round-trip delay reveals the location of the nonlinear junction in the cable run). Common fixes: re-torque connectors. Clean contacts with IPA (isopropyl alcohol) and lint-free wipes. Replace damaged connectors.

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