Advanced Multi-Frequency Low-Cost High-Gain GNSS Antennas for next generation of Mass-Market Devices
Mass-market GNSS receivers, mostly installed in smartphones, use low cost antennas that need to be compatible with the communication antennas of these terminals. Typical antennas used in mobile phones are simple PIFAs (Planar Inverted-F Antennas) suitable for any constellation in L1 band, such as GPS/Galileo, GLONASS/Beidou. Their linear polarization (instead of circular) and low gain lead to several dB of signal loss. The antenna location is dictated by smartphone’s design rather than RF constraints. This can result in sub-optimal locations where the interaction with user’s hand further weakens the reception of GNSS signals. In case of highly irregular gain patterns, the relative loss is estimated at around 11dB compared to standard patch antennas.
New generation of mass-market devices includes flexible and wearable smartphones, which require development of advanced techniques and technology in terms of flexible materials for receiver antennas, in particular for the GNSS one.
Moreover, manufacturers are starting to move to multi-frequency (L1/(L2)/L5, E1/E5a) multi-constellation solutions allowing the usage of propagation correction techniques. This requires development of multi-frequency antennas and receivers, in order to take full benefit of these techniques.
In the best-case scenario of a fixed user with a clear view of the sky and without precise propagation correction (http://gpsworld.com/positioning-with-android-gnss-observables/), current mass-market single frequency antennas and receivers can attain horizontal positioning accuracies in the order of 7.5m (2σ). Positioning accuracy significantly improves down to 0.8m with mass-market dual frequency antennas, an order of magnitude better than current mass-market single frequency antennas. In a real mobile user scenario, improvements should be even higher in relative terms.
In case of indoor GNSS, the main challenges are high attenuation, multipath, and near-far effect. Novel high-gain antennas would be of high interest for enabling PNT applications in harsh environment. In particular, development of a multi-frequency, low cost, circularly polarized antenna with higher gain than current solutions available in the market would constitute a major breakthrough for these applications. In order to enhance positioning accuracy, carrier phase stability versus variation of antenna phase center should improve for any device orientation, together with reduction in number of cycle slips.
The main objectives of the proposed activity are to:
- study advanced techniques for miniaturization and radiation enhancement of GNSS antennas to be applied to design, manufacturing and testing of multi-frequency, low-cost, high-gain circularly polarized antennas for next generation of mass-market devices, including overall investigations on front-end, ADC (Analogue Digital Converter) and signal processing;
- identify solutions improving positioning accuracy and availability by means of advanced mass-market antennas and enabling innovative PNT applications in harsh environment.
The tasks to be performed will include:
- definition and consolidation of mass-market device requirements for indoor and outdoor applications. Evaluation of the mass-market challenges, opportunities and applications;
- state-of-the-art review of antenna concepts and technologies for single and multi-frequency GNSS mass-market antennas;
- investigation of techniques for miniaturization and radiation enhancement, including novel materials like Electromagnetic Band-Gaps (EBGs) or meta-surfaces that could also be applied to new generation of flexible/wearable smartphones;
- design of a device to be used as a mock-up for comparison between state-of-the art antennas and advanced ones (single and multi-frequency), considering new generation of flexible/wearable devices and their suitability for manufacturing;
- preliminary design of multi-frequency (in particular L1/E1 and E5a/L5) antennas, focussing on radiation performance, antenna phase center stability versus device orientation, accommodation in presence of other communication antennas;
- testing of GNSS mass-market antennas in static and dynamic configurations (both pedestrian and automotive dynamics, indoor and outdoor), of body masking effects and of changes to GNSS antenna pattern when the device is held.
The results of the activity will provide:
- a breadboard integrated into a receiver representative of a mass-market device;
- a roadmap for technological developments in support of next generation multifrequency mass-market antennas, including consideration of design manufacturability and target production costs.
Results from related GSA activities (e.g. ‘Multi-frequency Multipurpose Antenna for Galileo) will be duly considered and the activity coordinated.