Although GNSS stands for “global navigation satellite system,” all constellations also provide highly accurate timing information. For example, GPS signals provide time data that’s accurate to 100 billionths of a second.
This makes GNSS ideal for applications such as time stamping business transactions at public EV chargers and synchronizing infrastructure in telecom networks and electrical grids. Leveraging GNSS also eliminates the need for devices to support time sources, such as atomic clocks and atomic clock receivers. This helps simplify device designs and reduce bill-of-material (BOM) costs.
Many applications need both location and timing information because they’re mobile, while others require only timing because they’re fixed, such as a cellular base station or a parking garage gate. From an antenna perspective, similar considerations apply to both use cases.
For example, when comparing antenna models, gain is important spec because it improves the signal-to-noise ratio and reduces Time to First Fix (TTFF). The more effective it is at pulling in signals weakened by distance or by physical obstructions such as skyscrapers and foliage, the easier it is for the GNSS receiver to do its job.
The antenna should be directional rather than omnidirectional unless it’s difficult or impossible to ensure that the antenna will always face up at the sky. (For more information about the differences, see “GNSS Antennas: How to Choose Between Directional and Omnidirectional Designs.”)
A directional design also is critical for installations in multipath environments, such as in a downtown concrete canyon. Some of the GNSS signals will bounce off the tall buildings, leading to delays in their arrival at the antenna and thus creating errors in timing. These problems can be mitigated by choosing a GNSS antenna that is designed to reject multipath signals using high directionality or other techniques. (For more information, see “Multipath Analysis Using Code-Minus-Carrier Technique in GNSS Antennas.”)
An active design also is recommended because the integrated Low-Noise Amplifier (LNA) boosts the signal before it’s sent to the GNS receiver. Taoglas active GNSS antennas also have front-end filtering, which removes out-of-band signals and noise to improve signal quality. (For more information, see “Active vs. Passive.”)
Protecting Against Tampering, Weather, and Wildlife
The antenna enclosure also can affect performance. For example, cellular base station GNSS antenna enclosures are shaped like an upside-down acorn because the point and slope help shed water, snow, and ice, which can attenuate signals. This shape also discourages roosting by birds, whose bodies can block signals.
In some applications, it may be desirable to keep the antenna hidden to protect against tampering. The Taoglas TFX125.A multi-band GNSS polymer antenna is transparent, making it difficult to see. It’s also long and flat, the kind of form factor that fraudsters and other unauthorized people wouldn’t look for or would struggle to see.
How to Maximize Resiliency
Installing the antenna in a high location helps ensure that it has a clear view of the sky, such as atop a tall building. But that also increases the possibility of a lightning strike. To mitigate that risk, choose an antenna that’s designed to protect against lightning-induced surges, such as the Taoglas Bolt A.93.A. Its IEC 61000-4-5/Class 4 protection also lowers BOM costs and system complexity by eliminating the need for expensive external solutions.
The Bolt has several additional features to consider when choosing an antenna:
- The enclosure is IP67 rated and UV resistant, which are key for protecting the antenna from environmental damage from storms and sunlight.
- Support for multiple constellations — GPS, GLONASS, GALILEO, and BeiDou — provides redundancy for mission-critical applications. This design also is a good fit for mobile devices that will travel around a continent or the world, or for creating single-SKU products that can be sold worldwide.
- Strong out-of-band rejection ensures that timing performance isn’t compromised when the antenna installed near transmitters, such as Wi-Fi, Bluetooth, and rooftop cell sites. For example, at the commonly used LTE frequencies between 700 MHz and 1 GHz, the A.93 provides greater than 80 dB of rejection. Between 1820 MHz and 3500 MHz, it has greater than 60 dB of rejection.
Finally, don’t overlook the cable, which is a critical component because most GNSS antennas for timing applications are installed externally. The longer the span — such as to a rooftop — the more likely that the cable will run past electrical wiring, elevator motors, and other sources of interference. Quality cable shielding is critical for ensuring that the signal isn’t undermined by the time it reaches the GNSS receiver. (For more information, see “A Crash Course on RF Cables” and “Top 6 Tips for Maintaining and Extending the Lifespan of RF Cables.”)
