Key Considerations for Timely GNSS Antenna Integration
Device OEMs and IoT solution providers add global navigation satellite system (GNSS) capabilities to their products because they enable value-added services such as turn-by-turn navigation, asset tracking, precision timing, fleet management and autonomous taxis. That means GNSS plays a fundamental role in creating new revenue streams and market differentiation opportunities.
Those business benefits highlight the importance of choosing the right GNSS antenna early on in the design stage. But that process can be challenging, especially for companies that have no GNSS experience. Even those with GNSS-enabled products in their portfolio still have to navigate a wide variety of options including constellations, bands, gain, axial ratio and antenna type for each new solution. Here are the top things to consider.
Constellations and Bands
A GNSS device can use one or more constellations: GPS, GLONASS, Galileo, BeiDou, NavIC and QZSS. One important factor is where the device will be used. For example, if the solution tracks high-value assets as they’re shipped around the world, support for multiple constellations would help ensure reliability and accuracy. Multi-constellation support also lets companies create single-SKU devices that can be sold globally. These are two reasons why over 30% of GNSS receiver chipsets support multiple constellations.
The constellation choices also affect which frequency bands are used. Support for multiple bands increases accuracy and reliability, such as by enabling the device to acquire usable signals even in environments where foliage and interference are common.
L1 is the most common band simply because it’s the oldest. But with the L2, L5 and L6 bands now available for commercial use, systems designers have additional options for increasing positional accuracy and overcoming ionospheric errors and interference.
Factors That Affect GNSS Performance
When choosing an antenna, it’s important to take a holistic view of the GNSS system, whose other major components are the receiver chipset module and the RF front end, which integrates the antenna with the receiver module.
Five factors play a major role in GNSS antenna performance: antenna gain, axial ratio, phase center offset (PCO), phase center variation (PCV) and group delay.
Where the device and/or antenna will be installed directly affects performance. For example, suppose the device will be installed in a location where it’s likely to spend a lot of time facing the ground. In that case, a patch antenna, which has a directional radiation pattern, wouldn’t have a sky-facing view of the satellites. A chip solution with an omni-directional radiation pattern is a viable alternative, especially if the product design and/or use case can’t be changed to achieve a view of the sky.
If a patch antenna is a good fit for the device’s use case, one important consideration is the size of the printed circuit board (PCB), which ideally should be at least 70 x 70 mm. A second key consideration is the antenna’s location on the PCB, which directly affects performance because it acts as a ground plane.
Some applications benefit from or require separating the GNSS antenna from the device rather than embedding it. One example is a first responder application where the ideal location is on the roof of the ambulance or police cruiser.
External installations create additional considerations, such whether to use an active or passive antenna. An active GNSS antenna will always provide superior performance because it can overcome cable attenuation better than an equivalent passive model.
In the case of the first responder vehicle, the metal roof acts as a ground plane for the antenna and helps improve performance. But if the antenna is mounted inside at the top of the windshield, performance could be affected by metallic tinting. Most vehicles — passenger, commercial and public safety — also have a 4G/5G cellular antenna. Its proximity to the GNSS antenna can lead to interference that undermines GNSS performance.
Testing and Documentation are Critical
Testing is crucial for verifying that the antenna works in concert with the rest of the GNSS system to achieve the product’s requirements, such as accuracy, performance and reliability. That’s why device OEMs and solution providers turn to Taoglas, which has the extensive experience and facilities necessary to thoroughly test and validate GNSS systems.
For example, all antennas are sensitive to their immediate surroundings, which is why an antenna’s tuning often needs to be tweaked after it’s integrated into a device. The Tagolas CSA.20 Passive Antenna Testing, Matching and Fine-Tuning service achieves the optimal resonant frequencies by implementing a lumped element electrical matching network or through small physical modifications to the antenna itself.
Another example is the Taoglas GSA.40 testing service, an approximately three-week process covering aspects such as power and mounting requirements, and testing the device in a static, open-sky scenario. Taoglas engineering collaborates with the client’s design team to determine if the test results meet the product’s performance requirements.
If not, Taoglas sales and engineering can make recommendations to improve the antenna performance. Clients also can use the Taoglas GSA.30 GPS Acquisition & Tracking Sensitivity Testing service, which include a GPS constellation simulator and anechoic chamber to measure conducted tracking sensitivity. This two-week testing process includes steps such as measuring the antenna passively on a VNA to determine the return loss, which will confirm whether the antenna has been correctly integrated into the product.
Taoglas has a broad, deep portfolio of active and passive GNSS antennas in chip, patch and other designs. But some applications have unique requirements, where a custom antenna solution is the best option. In the CSA.50 Custom Antenna Design service, Taoglas engineers collaborate with the client’s design team to develop key performance metrics, and then test and/or simulate different antenna designs, technologies, topologies, materials and locations to identify the optimal performance solution. This process can take as little as six weeks, which helps clients maintain their product launch schedules.
Finally, Taoglas provides a library of integration guides and other collateral to help systems designers understand their antenna and implementation options. For example, the GPS Patch Integration Application Note provides a concise overview of PCB positioning, ground plane size, impedance matching and other key aspects that systems designers should consider when using a ceramic patch antenna.
Each Taoglas antenna has a dedicated product page that provides a datasheet, drawings, a 3D model, certification documents and other downloadable information that systems designers need to make informed choices. Product pages also include one-click links to request quotes and samples.
If you would like a deeper dive into the concepts covered in this blog post read our GNSS Antenna Selection Guide at the button below.
