Research Highlights / Full Story

A new sensor device, smaller than a quarter, may be a means to alleviate some of that impact.

Researchers at Rochester Institute of Technology and PPC Corp. have developed a Smart Connector, a new sensor that once installed in the connecting units of coaxial cables, can provide information about equipment damage and pinpoint the exact location through self-diagnosing technologies, some of the most advanced in the field today.

The sensor is just one more in a line of products being developed through a growing corporate R & D initiative at RIT. The connector-sensor is not commercially available yet, says Robert Bowman, professor of electrical and microelectronic engineering in RIT's Kate Gleason College of Engineering. The university and PPC signed a licensing agreement in June. Both parties are in the process of final testing and technology transfer, he adds.

"Once the university demonstrated the feasibility of the technology, then there needs to be a phase where you show that the technology is robust in a real application," he says. "It's one thing to have a laboratory and demonstrate something, it's another thing to get it into a product. PPC worked very closely with us during this research effort, and we'll work with them as they try to integrate this technology into their product line."

Bowman and his research group worked with Noah Montena, principal engineer at PPC, a Syracuse-based telecommunications connector equipment company, to design the sensor-disk system. The system monitors, online, the primary failure modes in RF cables. Each disk contains a unique site identifier along the connecting cables, monitors critical conditions and is capable of activating or powering-down its energy capacity utilizing the radio frequency energy from the coaxial cables themselves.

"Not only can one predict in advance when you need to replace an RF connector before it fails catastrophically, but the system also provides a technology for characterizing the environment inside any kind of cable that has radio frequency energy in it," says Bowman.

How the Smart Connector Operates

Some cell towers rise more than 100 feet in the air, with varying lengths of cables all connected to an antenna array where radio signals are broadcast. Each cable might have as many as eight RF connectors. A master unit is located at the base of the tower. The sensor-disk system can determine at what point along the cable there is a problem because each cable connector is fitted with a sensor-disk and each has a unique location address.

The disk-sensor system was designed according to integrated circuit environmental standards, which means it can operate from zero-to-125 degrees Centigrade to ensure that the embedded chip will survive the temperature extremes found on exterior cable towers. The sensor-disk has a metal pattern coated with a polymer film called nafion to form a humidity sensor to detect moisture inside the connector. Connector tightness is determined through a capacitive-sensing ring on the disk. The signal generated will change if the RF connector becomes loose during normal operation.

In most applications, many disk-sensor devices operate on one tower. A master unit at the base of the tower interrogates the cable disks on a regular schedule. All of the disk information comes back to the master unit. The chip mounted on the sensor-disk is not physically connected to the cable but the radio frequency energy coming down the central portion of the conductor provides a source of energy, Bowman explains. On the inside of the disk there is an antenna that harvests energy off the cable and allows the chip to derive its operating power from that energy.

The master unit sends an inquiry out to a cable. Each disk listens in a lower power mode until its unique address is interrogated. It then powers up, takes measurements and sends a signal back to the master unit about its sensors' data, specifically humidity rates, connectivity quality and the quality of the radio frequency signal. If there is an alarm condition, it provides notification and site information.

"This technology is really exciting, and the impact it could have on the industry is only just becoming apparent," says Montena. "Up until now, connector and equipment failures could be detected only after tower capacity had been diminished, and only pinpointed on-site with the system shut down."

With Smart Connectors, data can be available real-time and accessed from a central location, he explains. A repair crew can be dispatched to a failing site with full knowledge of the problem before they even arrive.

"Imagine knowing you only need to send a ground crew to work at non-peak traffic hours, rather than a full climbing crew prepared for the worst after the tower fails," he says. "We are confident that this technology, combined with our groundbreaking approach to connector installation and environmental sealing, could transform the way the cellular industry thinks about maintenance and troubleshooting."

Bowman and PPC have 15 aspects of the Smart Connector technology patented, or in the process of being patented. The embedded computer chip alone has four such areas, including the antennae structure.

"The antennae design has several patents pending because it is a near-field coupler and has to be carefully modeled and constructed so it does not disrupt the normal cable operation," says Bowman, "However, it has to gather energy from the cable because that is where it derives its power."

Product Development and Future Applications Considered

"With a working design, the possibilities for integration are extraordinary," says Montena. "The sensors have been designed from the beginning with simplicity, robustness and cost-effectiveness in mind, and one of the advantages of collaborating on the research has been the communication of manufacturing considerations as design decisions get made. Beyond cellular connectors, it is easy to imagine this technology finding a place in other high value, or 'can't fail' applications such as communications or internal networks in spacecraft or aircraft. I look forward to uncovering all the possibilities."