New GPS antenna constructed for the ends of the earth

A new ESA-assisted, wide-bandwidth navigation antenna has been developed to receive both satellite and augmentation signals from anywhere in the sky, even up to a few degrees above the horizon.

With a growing number of navigation constellations in operation, the new VeroStar antenna from Tallysman Wireless of Canada is designed to capture all available signals and support the availability of L-band correction service signals. Its development was supported by ESA’s NAVISP (Navigation Innovation and Support Program).

Less visible to recipients in the far north or south

The precision of GNSS corrections is routinely improved by correction signals from augmentation systems such as the European EGNOS and the US WAAS, which also provide ongoing integrity (or reliability) information for highly accurate and life-like applications such as aircraft departures. However, these augmentation signals are transmitted by geostationary satellites that hang at fixed points above the equator, meaning that they become less visible to receivers in the far north or south.

“If you think of a Global Navigation Satellite System (GNSS) receiver as a camera, the antenna is the lens,” explains Allen Crawford of Tallysman. “Now you may have a great top-of-the-line camera, but if it doesn’t have a clean, distortion-free, and well-focused lens, all you get is blurry pixels that post-processing software can fix.

The new VeroStar antenna from Tallysman Wireless.

“So our antenna is like a lens, only that it collects radio signals instead of light – and this is the first step in the measurement process. We want the antenna to reproduce the received satellite signals as accurately as possible in terms of amplitude and signal phase on a fully representative basis so that the receiver can process them. “

Land surveying and precision farming

The VeroStar is available in a variety of models and sizes, including pole-mounted, surface-mount, and embedded versions. It is aimed at high-performance mobile applications such as land surveying, precision agriculture, maritime and autonomous vehicle navigation, which usually require precise positioning to a few centimeters.

“Different customers have different needs,” adds Tallysman’s Julien Hautcouer. “There are many GNSS antennas that work ‘well enough’. For example, antennas on cars only need to give a rough position. Then the navigation receiver uses its map to estimate which street you are on.”

Just as many satellite signals from several constellations

“We wanted to start from scratch with this new design for high-precision mobile users and be able to use as many satellite signals from as many constellations as possible – not just GPS, but also Galileo, the Russians and Chinese, Indian and Japanese systems, and correction service signals – and this requires good stable performance over a very large bandwidth. “

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GNSS device associated with multiple navigation constellations.

“We want it to only provide the pure circle signals for the right hand, which minimizes misleading reflected multipath signals,” notes Gyles Panther, CTO of Tallysman. “We also paid special attention to the symmetry of our antenna so that satellite signals are treated the same way, regardless of where the signals come from in the sky. It’s like looking through a good quality wine glass if you twist it in front of your eyes and the view stays the same. “

At the same time, the modern radio spectrum is very crowded, so the design team took special care to filter out radio interference that could lead to a drone being pushed down by local radio noise.

Electromagnetic modeling

The VeroStar design is based on eight corrugated petals of printed circuit boards inspired by the post-war Alford loop antenna, which was originally developed for the simultaneous transmission of multiple FM radio signals.

“The Tallysman team carried out a long optimization process using electromagnetic modeling to define the final shape for manufacture,” explains ESA navigational engineer Nicolas Girault, technical officer for the project. “In the end, they had an inexpensive, easy-to-repeat process that is really ideal.”

The new VeroStar antenna from Tallysman Wireless, based in Canada, is designed to capture all available satellite navigation signals. The VeroStar design is based on eight corrugated petals of printed circuit boards inspired by the post-war Alford loop antenna, which was originally developed for the simultaneous transmission of multiple FM radio signals.

The design maximizes the efficiency and performance of the antenna, adds ESA engineer Damiano Trenta: “Its rotational symmetry geometry and broadband behavior help provide a stable phase center over frequency and angular range. Optimizing the shape of the petals helps to improve the minimum gain at very low elevation angles compared to current products on the market and to maintain a very low level of cross polarity for multipath mitigation. ”

Subsequent production line tests showed that this value remained constant across all antennas.

The VeroStar models are now commercially marketed both individually and as part of customer products. The development of VeroStar was supported by NAVISP Element 2 – with the aim of making Member States more competitive by developing improved or innovative commercial products – and by the Canadian Space Agency.

Last update: 01/29/2021

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