Five Reasons Why Connectivity Fails
There’s no shortage of things that can undermine connectivity in public safety, defense, fleet, and utility IoT applications. The good news is that there’s also no shortage of tools, technologies, and tips that device OEMs and systems integrators can use to strengthen cellular and GNSS signals and in turn maximize application performance and reliability. Here are five key areas to focus on.
Internal Interference
Not all interference comes from external sources. Sometimes it’s generated internally by components such as the power supply and transceivers. An example is an asset tracker whose GNSS Low-Noise Amplifier (LNA) is desensitized when its cellular radio transmits in LTE Band 13. In this case, the solution is a layered approach: use a Surface Acoustic Wave (SAW) filter before the LNA to attenuate those out-of-band signals, followed by an active GNSS antenna with an integrated LTE Band 13 notch filter.
Another example is using Ethernet magnetics, whose common-mode chokes to filter out electromagnetic interference (EMI) and radio-frequency interference (RFI) at ports and connector modules. Magnetics help devices meet MIL-STD-461 EMI requirements by attenuating noise that could interfere with sensitive military equipment. But they can be equally valuable for demanding non-defense applications such as first responder devices and mission-critical enterprise IoT systems. (For more information, see “Ethernet Magnetics for Military Applications.”)
This example also highlights the importance of identifying all the potential interference sources during the design stage, when they’re a lot easier, faster, and cheaper to resolve. Discovering them months later during testing can lead to extensive, expensive rework that delays the product’s time to market and time to revenue. (For more tips, download “Maximizing GNSS Antenna Performance: Integration Tips for Engineers.”)
Signal Obstruction
Dense foliage, tall buildings, and concrete are just few common examples of objects and materials that can severely attenuate cellular signals. Mitigating that problem starts with identifying the primary locations where the device will be used and then the likely sources of attenuation in those places.
Take the example of smart grids. Smart meters, transformers, circuit breakers, reclosers, and other infrastructure often are installed in concealed locations for aesthetic, safety, and security reasons, such as in underground utility vaults. Their IoT devices all need reliable access to Supervisory Control and Data Acquisition (SCADA) and other systems for monitoring, control, and optimization.
If the smart grid uses public or private cellular, one solution is to use a wideband antenna, such as 600 MHz to 6 GHz. This gives the IoT devices the flexibility to use the band that offers the best performance in each environment. An example is using 800 or 900 MHz for maximizing in-building and underground penetration. (For more information, see “B106/n106: The New 900 MHz Option for Private LTE and 5G Networks for Utility Applications.” And for a case study about using broadband antennas, see “Smart Grid Specialist Meets Demand for Low-Cost, High-Reliability Metering Solutions.”)
Weak Antennas
Gain directly affects the performance and reliability of both the device and all of the applications using it. For example, GNSS signals are weak by the time they reach the Earth, so they’re vulnerable to atmospheric interference. Dense foliage and tall buildings further attenuate them, leaving the receiver with even less to work with.
All of that slows the receiver’s Time to First Fix (TTFF) and in turn delays delivery of position, navigation, and timing (PNT) data to the application. That sluggish performance is unacceptable for demanding and mission-critical applications such as drones and turn-by-turn navigation. (For more insights and design tips for GNSS and cellular, see “Understanding Antenna Gain and How It Affects Device Performance, Reliability, and Competitiveness.”)
Environmental Conditions
External antennas spend their entire service life exposed to rain, ice, hail, UV rays, salt spray, temperature extremes, rodents, insects, and birds. All of those can breach antenna enclosures and attack the delicate elements inside.
When comparing external antennas, pay close attention to the enclosure’s IP and IK specs. For example, an IP67-rated enclosure is verified to withstand up to 1 meter submersion for 30 minutes, while an IK08 rating means the antenna elements inside are protected against objects weighing up to 1.7 kg dropped from a height of 29.5 cm. (For more information, see “What Does an IP67 Rating Really Tell You about an Antenna’s Durability?” and “How IP and IK Ratings Measure Real-World Durability.”)
To meet those kinds of demanding requirements, Taoglas developed the Colosseum Series and Olympian Series, all of which have an IP67 enclosure. Taoglas also has antennas designed to withstand the unique challenges of marine environments, from salt spray to seagulls. One example is the Taoglas Neptune XAHP.30, an active multi-band GNSS antenna whose IP67-rated enclosure is domed both to shed water and eliminate signal attenuation from birds perching. It’s also designed to operate in conditions from -40C and +85C.
And make sure the antenna’s cables and connectors aren’t weak links. The cable’s shield and jacket layers should be thick enough to protect the conductor, while the connectors should be ruggedized and, during manufacturing, tested to verify that they’re sealed tight against the cable ends. (For more insights, see “A Crash Course on RF Cables” and “What’s Inside is What Counts: Understanding Antenna Coaxial Cables.”)
Integration Weaknesses
Even the best antennas can struggle if they’re not in the right location. To avoid that problem, follow the antenna’s integration guide. Pro tip: When choosing an antenna, read all of the candidates’ integration guides at the start of the project rather than weeks or months into the project. This helps identify the right one and ensures the PCB and other aspects of the product can accommodate its unique location requirements, thus avoiding extensive, expensive re-work later on.
In the case of patch and chip antennas, the integration guide specifies the optimal PCB location and minimum ground plane size. An example is placement mid-point on the long side of the PCB with a minimum ground plane of 80×40 mm for chip antennas. The integration guide also provides the minimum size of the keep-out area, which is the distance from the device’s processor, memory, battery can, and other metallic structures that can undermine antenna performance and reliability.
For external antennas, one important integration consideration is the surrounding environment. For example, an antenna mounted on a vehicle’s roof or trunk uses that metallic surface as its ground plane. The size of that surface and the antenna’s location within it directly affect signal quality and thus the performance and reliability of the services using that signal.
If the antenna is external, sometimes the “host” might not be able to provide a ground plane. An example is a drone whose shell is plastic rather than metal. In those cases, choose a quad helix GNSS antenna that has an even gain across the hemisphere, such as the Taoglas Accura Series’ TS.125.0111W. In the case of cellular, a good choice is the Taoglas MA741 Pantheon, which can radiate effectively even on plastic surfaces.
Even the shape of the mounting surface affects reliability. For instance, most vehicles have a curved roof to shed water. It’s seemingly slight yet big enough to create a gap between the roof and the antenna enclosure, where water, ice, and insects can enter and damage the elements and cables. The Taoglas Patriot Series eliminates that vulnerability with a custom-engineered foam gasket to ensure a perfect seal between the enclosure and the roof of popular public safety vehicles such as the Ford Interceptor.
An all-in-one antenna such as the Patriot also gives fleet owners and upfitters more flexibility to avoid interference. When up to 18 antennas are housed in a single enclosure, it’s much easier to keep everything a half wavelength away from light bars and other equipment that generates RFI.
Get in touch for orders or any queries: sales@rfdesign.co.za / +27 21 555 8400
Courtesy of Taoglas
