Sharpening satnav for smartphones

All smartphones sold in Europe today should make use of Europe’s own Galileo constellation, which is today the world’s most precise satellite navigation system – delivering metre-scale accuracy to more than 3 billion users around the globe. But smartphone users are not typically accessing the same level of precision as those employing dedicated satellite navigation receivers.

“Satnav is only one of many different functions our smartphones are designed around, so that their typical localisation error is quite high,” says antenna engineer Victoria Iza, overseeing the project for ESA.

“In practice it depends on your surroundings, with worst performance in built-up areas and urban canyons where part of the sky is obscured. The localisation error can climb up to 10 m or even higher – still enough to put you in the right street, but only just. That’s because, if you take a smartphone apart, you find its satnav function relies on a single antenna, smaller than a mini-sim card.

“With the Advanced Multi-Frequency Low-Cost, High Gain GNSS Antennas for next generation of Mass-Market Devices, AMELIE, project, we increased the number of satnav antennas, with one on each side of the circuit board – carefully placed to avoid the phone buttons and speaker – then combined their inputs using an array approach usually employed for satellite antennas. We targeted enhanced performance in geo-localisation, signal gain and phase, suitable for next-generation devices.”

The original concept came from the Fraunhofer Institute for Integrated Circuits in Germany, and was supported through ESA’s Navigation Innovation and Support Programme (NAVISP), investigating new concepts in the realm of positioning, navigation and timing. Germany’s TeleOrbit company acted as the prime contractor for the project.

“More typically our team is working on large-size satellite antennas, so this is an interesting change, moving down in scale to smaller, low-cost, mass-market devices,” adds Victoria. “And when it comes down to it, success is defined by the end-user experience, so that meant that as well as lab-based testing the project team had to go outside and perform a variety of walking and driving trials.”

Testing took place in and around in the city of Nuremberg, where TeleOrbit and Fraunhofer-IIS are located. Matthias Overbeck of Fraunhofer-IIS explains: “We used our anechoic chamber to assess antenna patterns and mitigation of multipath signals, but we also went out for walks and drives through a variety of different environments, from the built-up city centre to narrow streets and out to less populated open sky areas.

“A lot depends on the environment because high buildings lead to shadowing of GNSS signals, while all kind of objects also reflect the signals. This multipath signals also reduce positioning precision.

“Additionally, the field tests showed how important it is to consider the user since the placement of the smartphone in a user’s hand influenced the behaviour and performance of the AMELIE antenna.”

The team tested two types of antennas: a dual-band design providing two separate frequency bands – offering a big increase in performance over traditional smartphone-class receivers because errors from the ionosphere, an electrically-active atmospheric layer, can be cancelled out – and a multiband version allowing up to five frequency bands, from the GPS, GLONASS and BeiDou constellations as well as Galileo.

For use in automobiles, the team also assessed a ceramic holder that works to optimise the focus of the antennas to the satnav signals, while keeping the phone at an optimal 30° angle.

The team achieved a maximum localisation error of 1 m, a tenfold increase in precision. For their next step they hope to team up with a smartphone manufacturer directly, to get insight into the maximum area available for satnav functionality – bearing in mind that the performance of the antennas can be impinged by neighbouring components.

They are also reaching out to drone companies, where space is less constrained and the added performance offered by the array antennas could offer a distinct market advantage.

Daniel Seybold of TeleOrbit adds: “Now it is up to us to find the perfect industry partner to turn the prototype into a working product users can implement.”

AMELIE is supported through Element 1 of NAVISP, focused on innovative concepts, techniques, and technologies linked to positioning, navigation and timing. The design went on show at last month’s’s NAVISP Industry Days.

About NAVISP

Many of the experts that designed and oversaw the Galileo satnav system are now supporting cutting-edge European companies in the development of new navigation technologies and services. The result is ESA’s Navigation Innovation and Support Programme, NAVISP.

NAVISP is looking into all kinds of clever ideas about the future of navigation: ways to improve satellite navigation, alternative positioning systems and, new navigation services and applications.

Working in partnership with European industry and researchers, more than 200 NAVISP projects have been initiated so far.