What is PIM Effects in Base Station?
From:     Date:2022/04/19 11:44:33     Browse:40

What is PIM Effects in Base Station?


What is PIM?

PIM means passive inter-modulation. PIM represents the inter-modulation products generated when two or more signals transit through a passive device with nonlinear properties. The interaction of mechanical components generally causes nonlinear elements.

As we all know that active devices produce nonlinear effects in systems, various techniques have been developed to improve the performance of such devices at the design and operational stages. It is easy to overlook those passive devices may introduce nonlinear effects that, although sometimes relatively small, may seriously affect the system's performance if not corrected.

PIM means "passive inter-modulation." It represents the inter-modulation product produced when two or more signals are transmitted through a passive device with nonlinear characteristics. The interaction of mechanical joints usually causes nonlinear effects, especially at the junction of two different metals. Examples include loose cable connections, dirty connectors, poorly performing duplexers, or aging antennas.

Passive inter-modulation is a significant problem in cellular communications and is very difficult to solve. In cellular communication systems, PIM may cause interference, decrease the receiver's sensitivity, and even block communication completely. This interference may affect the cell that produced it and other nearby receivers.

For example, in LTE Band 2, the downlink range is 1930mhz to 1990mhz, and the uplink range is 1850mhz to 1910mhz. If two transmitters at 1940 MHz and 1980 MHz transmit signals from a base station system with PIM, their inter-modulation produces a component at 1900 MHz that falls into the receiving band. It's affecting the receiver. In addition, the inter-modulation at 2020 MHz may affect other systems.

PIM is a significant problem for service providers and equipment providers. By detecting and solving the problem as much as possible, the system reliability can be improved, and the running cost can be reduced. This paper attempts to review the sources and causes of PIM and the techniques for detecting and resolving PIM.