Although smart watches are the best-known type of wearable device, the market is much wider and deeper, including:
- Pet tracking collars to help owners quickly find their lost cat or dog.
- Livestock collars and ear tags that provide information such as location, heart rate and temperature.
- Wrist-worn sensors for electricians that warn when they’re near dangerous voltage and alert their employer when they detect a fall.
- Wearable panic buttons for home health aides, hotel housekeepers and other lone workers.
Whether they’re worn by people or animals, all wearables have one thing in common: Wireless performance is critical. For example, wearables that use GNSS need to quickly pinpoint injured lone workers or livestock in distress so help can arrive in the right place right away. Here’s how to maximize GNSS accuracy and availability.
GNSS Constellation Options
A GNSS module and antenna system can support a single band and a single constellation or multiple bands and multiple constellations. For device OEMs and systems integrators, the choice comes down to considerations such as cost and application requirements.
Most wearables — especially those developed for the North American market — have a GNSS module and antenna that support GPS’s L1 signal at 1575.74 MHz. If the wearable is designed for applications that aren’t life or death, or whose target users are highly price sensitive, then L1 alone may be enough.
But if the application is mission critical, or if users are willing to pay a premium for high accuracy and high availability, then there’s a strong business case for augmenting L1 with GPS’s L5 signal. Initially developed for aviation safety, L5 is the most advanced civilian signal available from GPS. The combination of higher power and lower frequency (1176.45 MHz) can significantly boost application performance in locations with dense foliage, skyscrapers and other environmental factors that undermine L1 signals. (For more information, see “Navigating the L1, L2 and L5 Band Options for GNSS.”)
If the wearable’s market is global rather than North America, then it’s worth considering support for one or more additional global GNSS constellations, such as BeiDou, Galileo or GLONASS, or regional ones such as QZSS (eastern Asia-Oceania) or NavIC (India and surrounding areas). Although GPS provides global coverage, augmenting it with another global or regional constellation can improve application precision, resiliency and availability by giving the device access to additional satellites and signals at different frequencies.
This diversity can be particularly valuable for users in latitudes above 55 degrees, where GPS accuracy begins to suffer because its satellites rise only 45 degrees above the horizon. This limits the device’s visibility of its satellites. Adding support for GLONASS and/or Galileo lets wearables take advantage of constellations whose orbits provide better coverage in higher latitudes. (For more information about coverage and capabilities, see “GNSS vs. GPS: What’s the Difference?” and “How to Navigate the L1, L2, L5, E5a, E5b, and G2 Alphabet Soup of GNSS Constellations and Signals.”)
Balancing Form Factor and Function
Another thing that all wearables have in common is that they need to be relatively compact and lightweight. The bigger and bulkier they are, the more likely people and animals will try to avoid wearing them.
Svelte form factors create design challenges. For example, off-the-shelf GNSS antennas that are metal stamped or flexible adhesive types can literally be a bad fit for wearables that are shaped like a wristwatch.
An alternative is Laser Direct Structuring (LDS), a process that uses polymer resins to create a GNSS antenna in a 3-dimensional plastic carrier. The laser enables the metallic antenna traces to adhere to the polymer, which can be part of the device’s housing or a separate piece of plastic.
LDS enables the GNSS antenna to accommodate the wearable’s form factor rather than the other way around. This helps avoid the expense of redesigning the wearable to accommodate an off-the-shelf antenna.
As a result, LDS can help ensure that the wearable meets the target market’s size, weight, aesthetic and price expectations, as well as the OEM’s profit margin requirements. Avoiding a redesign also means that the wearable can get to market faster and start driving revenue. (For more information about LDS, see “Leverage Innovative New GNSS Antenna Manufacturing Technologies to Ensure High Performance Even with Complex Form Factors.”)
Testing Ensures Performance Requirements are Met
GNSS reliability and performance can make or break a wearable in terms of competitiveness, revenue and brand reputation. That critical role highlights the importance of considering GNSS antenna options early on in the device design process.
But navigating all of the options for GNSS signals, constellations and antenna materials can be challenging even for experienced systems designers. Another challenge is testing the wearable to ensure that its GNSS antenna and module are optimized to meet performance requirements.
Taoglas provides a variety of engineering services to help device OEMs overcome those challenges. Two examples are:
- The GSA.30 GPS Acquisition & Tracking Sensitivity Testing service uses a GPS constellation simulator and anechoic chamber to measure conducted tracking sensitivity. This process includes steps to confirm whether the antenna has been correctly integrated into the wearable.
- The CSA.50 custom GNSS test service is ideal for use cases whose unique, demanding requirements can’t be met by off-the-shelf antennas. This service includes simulating a design, building prototypes of it and testing them first in an anechoic chamber and then at the system level.
