ONE SIZE DOES NOT FIT ALL: OPTIMIZED CONNECTORS ARE CRUCIAL TO SYSTEM PERFORMANCE

By David Keisling

RF reliability and performance depend on a perfect fit between the system design and specific application needs. One size does not fit all; the performance of any RF system is heavily determined by each of its hardware components and, especially, how they fit together. Some RF installations demand relatively standard products, while others need custom solutions to meet unique requirements.

Environment, temperature variations, vibration, density, and frequencies are just a few factors influencing performance requirements. Installation and maintenance must also be realistically considered – for example, if the RF system is operating in outer space, it needs to be maintenance-free. Similarly, if components will be used for 5G networks, where high cable density is present, easy handling and installation are required to make reliable connections within small spaces.

Several innovative RF interconnect designs, including bundled solutions and locking miniature connectors, were created to address specific needs not fulfilled by standard designs.

BUNDLED SOLUTIONS

Bundled solutions permit installation in tight spaces; instead of connecting multiple threaded connectors, just one will do the job. This strategy is faster and easier to install and maintain and provides one reliable, high-performance connection. Bundled design solutions are becoming particularly popular in applications such as space and avionics, where cable installations and rising operating frequencies demand coaxial cables and connectors that can deliver high signal integrity and reliability.

INDUSTRY EXAMPLE: 5G MULTIPORT CONNECTORS AND BUNDLED CABLE ASSEMBLIES

5G technology requires a substantial expansion and upgrading of existing network infrastructure. To deploy 5G, the networks must be densified, which means more cell sites must be deployed in more locations to get the signal closer to users. 5G applications use antennas with multiple in/multiple out (MIMO) feeds, which substantially increases the number of RF ports.

5G antennas are also shrinking in size as higher frequency bands are used to accommodate larger bandwidth requirements. This translates into more antennas and the corresponding RF cables and connectors needed to power them — in a much smaller space. This type of equipment is also packed much closer together than traditional telecom towers were years ago; some cells are only 100 yards apart. Designing an interconnect system that will perform well and withstand extreme environmental and technical conditions reliably and consistently over long periods is a challenge. Densification creates additional challenges related to installation, torquing, sealing and ruggedization against weather conditions, and other application-specific factors. In addition, 5G small cells have limited space for equipment, so minimizing size and weight are also key goals.

With so many components in such a small space, maintenance can be challenging. If an interconnect fails, it can be hard to troubleshoot the exact one. Moreover, installation can be a time-consuming, labor-intensive, and logistical nightmare. Hooking up the right cables, the right ports, and torquing are all concerns in this scenario. Proper weather sealing is also necessary; it is imperative to ensure that the seal is good but not over-torqued.

New bundled coaxial cable and multiport connector solutions support optimal speed, coverage, and latency requirements for 5G installations. A bundled cable design can help create the perfect flexible antenna jumper for applications requiring multiple runs. A spiral configuration of multiple flexible and ultra-flexible, low PIM jumper cables can be created under a common polyurethane outer jacket to promote easy installation and improved operation. The individual coaxial cable runs are spun together in a way that easily flexes, essentially creating a bundle, which is then run through a large jacket extruder where a ripcord is placed.

This design enables four or five individual cables to be fed into the back of a multiport connector such as those based on the industry-standard MQ4/MQ5 design that encompasses a four-contact connector and a five-contact connector. MQ4/MQ5 connectors incorporate multiple RF ports, greatly reducing the number of cables to hook up, saving a lot of labor, and creating a more rugged solution. They also make the assembly more weatherproof and UV resistant.

Using the four- or five-conductor solution eliminates the need to create individual weather seals, resulting in tremendous labor savings. Furthermore, it reduces the need to worry about coupling torque. This is critical because all it takes is an error on just one weather seal to create a point of ingress for water that could create a multitude of problems and even potentially shut the system down. With a bundled solution, the connection between the male and female cluster connectors is sealed to IP67, as are the connector bodies and the transition from the cluster connector to the bundled cable. Any potential system troubleshooting becomes much easier. Finally, the possibility of hooking up the wrong cable to the wrong port is eliminated. The solution is keyed, so the cables can only be hooked up a certain way— no torque wrenches, know-how, or special technique required.

LOCKING MINIATURE PUSH-ON AND LOCKING MINIATURE BLIND MATE CONNECTORS

The RF industry has been using sub-miniature push on (SMP) connectors for decades. SMP connectors are easy to install by simply pushing against each other to connect and then pulling apart to disconnect. Installers can mate connectors without threading, eliminating the need for small wrenches and other tools. The SMP enables a small amount of radial misalignment during mating, which would be unacceptable with threaded connectors.

While SMPs are still a valuable connector option for many designs, they pose problems as applications demand higher and higher frequencies. One critical issue is shielding and electromagnetic interference (EMI). Similarly, the SMP’s design reduces its ability to function without affecting other equipment in the same environment. Called electromagnetic compatibility or EMC, the connector’s signal leakage issues often result in failed EMC tests. In short, the SMP’s lack of proper electrical bonding and shielding exposes the conductor’s signal to external influence.

Another major failure area in the SMP’s design makes it susceptible to ingress from saltwater, fuel, and other contaminants. The lack of an environmental seal due to their mechanical openings makes SMPs prone to corrosion and failure. Another problem arises with using SMPs in high-vibration applications, where their easy connect/ disconnect design makes them susceptible to unwanted de-mating in high vibration environments.

A new generation of locking miniature push-on (TLMP) and locking miniature blind mate (TLMB) connectors have been introduced, specifically designed to overcome performance issues arising from typical SMP connectors’ susceptibility to EMI and EMC interference, and liquid and salt ingress. Their rugged, sealed design is more durable, enabling these connectors to operate in harsh environments.

The TLMP/TLMB connector retains the small form factor of the SMP and adds improved environmental, shielding, and power capabilities, with a frequency range from DC to 60 GHz. A positive locking feature with visible green (locked) and red (unlocked) color coding prevents de-mating under vibration and shock. At the same time, the high-power/high voltage design overlaps the insulators, cutting off a direct path to the ground from the center conductor to the outer shield to enable higher-power or higher voltage functionality. The connector’s slots are also entirely covered with the mating part, preventing signal leakage, thus improving EMI and EMC. The TLMP has a latching mechanism that significantly improves mating retention, making it a better option than SMPs that use threaded bodies or similar designs that have attempted to overcome the problems of traditional SMP connectors. The mating connectors are also designed for board-level mounting, including a version with a fully shrouded tine protection design, the TLMB.

The TLMP/TLMB was created for high-reliability, high-vibration environments such as military and aerospace. Areas where EMI may be an issue, such as shipboard or aircraft applications, need an environmentally sealed and shielded connector. While an SMP is at risk of disconnection in high vibration environments such as aircraft carriers or weapons launches, a locking miniature push-on connector provides a reliable and secure connection.

Today’s challenging RF applications require a new generation of interconnect solutions that can ensure high reliability, high resistance to vibration, and high density. Innovations in this area include multiport, locking miniature push-on, and locking miniature blind mate connectors.

When it comes to selecting RF cables and connectors, partnering with a supplier whose engineers can design an optimized solution for the application’s unique needs will produce better electrical, mechanical, and environmental performance, as well as easier handling in the field. Look for a supplier with a long history of building quality cable assemblies and connectors, along with the skill, processes, techniques, and materials to bring custom solutions to life.