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Why GNSS device design demands careful attention

Growing numbers of IoT devices across the globe are relying on GNSS connections to ensure global coverage to maximize device performance – therefore careful attention needs to be given to the design of GNSS devices. Access to multiple constellations and bands needs to be taken into account at the design stage but there are also fundamental issues to consider which cover; where the GNSS module is located in the device, which antenna is selected (and where it is located) and how the device is configured to optimize power consumption.

Reducing complexity of GNSS device design

Each of these decisions have a knock-on effect on the neighbouring components and increases design complexity, so the importance of planning ahead in terms of hardware design cannot be over-stated. Importantly, any mistakes made at the hardware design stage are difficult or impossible to change later, so it is of paramount importance that all the hardware design implications are explored, thought-through and considered in depth at as early a stage as possible.

In GNSS devices design, this preparatory work is of extreme importance because the RF receiver is 100 times more sensitive than a cellular signal and is therefore more prone to interference and noise. Don’t forget, GNSS signal comes from approximately 20,000km away compared to just a few kilometers or meters for cellular and other wireless technologies. Further to this, GNSS is sensitive to signal power, noise power and the ratio of signal and noise power in a given bandwidth (SNR) fluctuations. This introduces further variables that affect performance, but which can be largely addressed by effective device hardware design.

Additional challenges in GNSS device design

The challenges to excellent GNSS performance don’t end here. The issue of gain also affects GNSS performance. It relates to the efficiency of an antenna in a particular direction, but this can distort performance in other dimensions, so antennas should be placed pointing at the sky rather than in a specific direction. Next, polarization is an issue that is often ignored but should be considered carefully. Light waves are unpolarized and can travel in all directions but signals from the satellite are polarized so you should use the appropriate antenna to ensure you receive the maximum, polarized signals from the satellite. On top of these there are a series of other considerations to carefully assess, all of which impact on GNSS device performance.

There are additional, fundamental device design aspects to address. Antenna placement is an obvious way to enhance performance. Quectel issues guidance on this, pointing out how to optimize patch antenna module design and setting out the recommended ground plane for optimal efficiency. The location of the antenna within a device is also important and Quectel’s advice is to place antennas in recommended locations that allow for maximized performance.

Achieving optimal GNSS device designs

All of these device designs issue help to reduce interference, decrease power consumption and enable the best performance to be achieved. These, and many other issues were addressed in a recent Quectel Masterclass which outlines how to optimize GNSS hardware design. The Masterclass, hosted by Quectel FAE Ratan Yadav, set out further causes of interference and how to mitigate them and also addressed questions from the audience. To view the webinar visit: https://www.quectel.com/library/quectel-masterclass-apac-gnss-design

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