What is PIM Testing?
Passive InterModulation (PIM) testing will become more and more important. Today’s mobile handset users expect consistent high throughput from their devices and, consequently, push current networks to their limit. The upcoming networks feature an increased mobile data rate of 100 Mb/s and this higher transmission rate will expose PIM vulnerabilities in today’s networks like never before. Next generation FDD and TDD networks require superior network transmission fidelity, higher than previous generations. Network operators also face the challenge of maintaining customer loyalty in an unforgiving competitive arena. As such, good network PIM performance and PIM testing are now imperative.
Figure shows an example of an operator needing to keep PIM signals below -106 dBm since the base station (BTS) Rx sensitivity is at - 105 dBm.
It should be noted that PIM signals exist as a result of the combined transmission of multiple carrier frequencies within a transmission line path. The objective is to ensure that these levels, by design and in practice, should occur at an amplitude which is below the base stations receiver sensitivity. The amplitude of these undesired signals is directly influenced by the fidelity of the transmission line path, including all components and junctions that can introduce a non-linear effect to the signals passing through them.
Read more about passive intermodulation.
High Power PIM Testing
In order to represent real-traffic network conditions PIM testing measurements must be made at the base station radio power level or higher. PIM tests that are performed at low power can mask the presence of passive intermodulation in the network. The ability to exceed the current 20W specification gives operators much more measurement confidence and with UMTS and LTE carrier power levels likely to be specified at 40W the ability for PIM testing at these levels will become mandatory.
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