Manufacture Of Low PIM Coaxial Cable Assemblies

With the increase in distributed antenna systems (DAS) and the installation of small cells, low passive intermodulation distortion (PIM) interconnect assemblies have become increasingly popular. Modern complex multi-carrier communication systems such as DAS and small cells are now incredibly broadband and support numerous wireless standards such as WiFi, cellular, military, government, public safety and emergency frequency bands.

There is only a growing number of sub-6 GHz wireless standards and technologies of any kind, including Internet of Things (IoT) devices, new 5G-NR sub-6 GHz Ghz services, television white space (TVWS) devices, and more. Many of these standards cover frequencies that would distort any other frequency band if mixed passively. The larger the system bandwidth, the more likely it is that PIM distortion will result in reduced throughput.

As a result, low-PIM coaxial cable assemblies consisting of low-PIM cables and low-PIM connectors are increasingly used as patch cords and interconnects between wireless system components. The value of low PIM cable assemblies is that they have been tested for low PIM operation and are expected to be certified. If properly installed in a system also designed for low PIM performance, these interconnects should not add any significant PIM and mitigate the distortion typically caused by cables with higher PIM ratings.

The construction of a low PIM cable assembly typically consists of three main parts, the two end connectors and the coaxial cable itself. Each terminal connector (DIN 7/16, 4.3-10, Type N and 4.1/9.5 commonly used in communication system applications) shall have a low PIM rating and include hardware that can be attached to coaxial cable, which also Good for low PIM installations. Since any other connection may result in an increase in the system's PIM level, connectors should be chosen to eliminate the need for adapters on both ends. This may require male-to-male or male-to-female connectors, or different connector types and genders on both ends.

Cable assemblies with different connector types are often referred to as in-line, where cable assemblies with the same connector type are referred to as in-line. Additionally, right-angle adapters are often used in narrow and difficult installation situations. However, using low-PIM and right-angle connectors for cable assemblies can result in better PIM performance than relying on additional right-angle adapters.

The coaxial cable should also have a low PIM rating and also meet building code requirements. For building codes, the UL910 rating of gas-filled coaxial cables meets most building code requirements. Low PIM coaxial cables are usually made with solid inner and outer conductors, as solid conductors tend to perform better in low PIM applications than braided ones. Since solid conductors are less flexible, corrugated outer conductors are often used to provide some flexibility and ease of installation. Solid outer conductors also provide better shielding than braided conductors, which can be useful in installations with a large number of services and connections, and nearby transmitters.

Finally, the assembly of the entire cable must be done in a way that ensures low PIM operation, and testing must also be done to ensure that no component or any manufacturing defect in the assembly process will result in a failed unit. If the PIM performance is listed on the cable, it can make installation easier when evaluating the PIM performance of the entire system, especially during troubleshooting.