Antenna innovator Q&As spotlight advancements

Photo: Trimble

Antenna development, going all the way back to the first antennas, has been one of continuous innovation,” Richard Langley wrote in our September issue. Even after more than 30 years of GNSS technology development, he pointed out, GNSS antenna development continues.

His statement is borne out by the responses submitted by manufacturers of GNSS antennas to four questions we posed to them:

• What specific challenges are your antennas designed to address?
• Over the past three years and the next three years, what have been/will be your key innovations?
• How are advances in real-time kinematic (RTK) and precise point positioning (PPP) changing requirements for GNSS antennas?
• What technical challenges or industry trends do you find most interesting or noteworthy?

The responses display a wide range of antenna designs for a wide range of applications. They show how manufacturers must constantly balance requirements for positioning accuracy, form factor, interference management and cost. For the GNSS user segment, antennas are the first link in the processing chain and the first line of defense against jamming, spoofing, multipath  and, increasingly, adjacent band interference. Antenna designers are also challenged by the growing adoption and sophistication of RTK, PPP and similar technologies. All these variables, challenges and scenarios are reasons for the constant evolution of GNSS antennas.

Finally, it is not always obvious whether a device should be classified as a receiver or an antenna. For example, what Harxon calls a “smart antenna” others might call a receiver.

NovAtel

With Sandy Kennedy, VP of Innovation

Specific challenges
NovAtel antennas enable exceptional tracking for multi-constellation precision and are packaged for practical use in the field. Our antennas are designed to be the first link in the processing chain to deliver centimeter-level precision in harsh operating environments and applications, including contested or crowded RF environments through our CRPA antennas.

Key innovations
Over the past three years, we have focused on multi-frequency support and simultaneous L-band reception (seen in the NovAtel GNSS-850) to provide exceptional positioning solutions and support future technology like RTK From the Sky. Optimized to work with OEM7 receivers, NovAtel antennas leverage patented multi-point feeding networks to providΩe symmetric radiation patterns across all frequencies for excellent multipath rejection and minimal phase-center variation and offset. In the next three years, we expect to further reduce the size of antennas needed in a resilient high-precision solution. At the same time, we are continuing to improve robustness to adjacent band interference. We work to optimize the full GNSS ecosystem, from the signal in space reaching the antenna, to the final position, velocity and time (PVT) solution exiting the receiver.

Anechoic chamber testing. (Photo: NovAtel)

Advances in RTK and PPP
Advances in corrections expose measurements from low-quality antennas. You need an antenna with sub-millimeter phase-center variation (PCV) accuracy and stability on par with the algorithms delivering centimeter-level solutions. When the processing chain eliminates errors down to the centimeter level (or less), you must avoid adding errors from unstable phase centers, for example.

Technical challenges and industry trends
A difficult challenge facing the antenna industry is the commercial demand to reduce the size and weight of antennas while maintaining functionality and performance. The industry will need to continue balancing between size and performance while producing innovative GNSS antenna solutions integrated with other technologies, for example with anti-jam capabilities.

Harxon

With Leo Wang, Product Technical Director

Specific challenges
The design of Harxon’s GNSS antennas aims to achieve a perfect balance between easy integration with RTK solutions and the ultimate product performance by meticulously dealing with wideband, positioning accuracy, form factor, and interference management.

Key innovations
Over the past three years, our signature antenna innovation is our 4-in-1 X-Survey HX-CSX100A multifunctional GNSS antenna, which integrates a GNSS antenna, 4G, Bluetooth and Wi-Fi in one compact enclosure. This multifunctional antenna simplifies receiver integration into an RTK solution and facilitates industry development. In the next three years, Harxon looks forward to more breakthroughs in positioning technology and delivering pragmatic innovations.

Photo: Harxon

Advances in RTK and PPP
The development and maturity of these technologies require a higher standard for more delicate GNSS antenna structure design that takes product form factor into consideration while upgrading performance via wideband, high gain and positioning accuracy.

Technical challenges and industry trends
The 5G era has arrived, and the application of 5G technology for the internet of things (IoT) is extensive. China has also proposed the integration of 5G technology and BeiDou. We believe that, in the next few decades, GNSS positioning and 5G technology will be widely applied in the IoT industry and create huge benefits.

Tallysman Wireless

With Gyles Panther, President and CTO

Specific challenges
The challenge faced by Tallysman was manufacturing a full-band GNSS and L-band correction antenna, with high efficiency, tight PCV, low-gain roll-off and low axial ratio down to the horizon, and minimized multipath. Plus, a narrowly filtered low noise amplifier (LNA) to mitigate interference, all in the smallest possible package.

Key innovations
Over the past three years, Tallysman has released the VeraChoke, helical and VeroStar lines. The VeraChoke serves the geodetic and survey reference station markets with PCV and full-band GNSS coverage.

Our helical GNSS and Iridium antennas are lightweight, compact and robust. They provide a precise phase center and radically reduced dependence on a ground plane because of their differential mode of operation. Their exceptional low weight makes them an excellent choice for copter-style UAVs.

Photo: Tallysman

The patented VeroStar element combines full coverage of the upper and lower GNSS bands, plus L-band corrections service, with reception of L-band downlink Mobile Satellite Service (MSS) signals and exceptional low elevation angle reception. It is rugged, compact and lightweight — ideal for land and marine rover applications. It also provides minimal and symmetric PCV with outstanding all-around performance.

Advances in RTK and PPP
Both correction systems require rover receivers to phase-lock on low-amplitude GNSS satellite signal carriers, and both are hugely dependent upon the GNSS antenna. The corrections are critical for precision agriculture and land survey applications. Our precision antennas are specifically designed to minimize phase-lock loop (PLL) cycle slips.

Technical challenges and industry trends
Interference, accidental or intentional, is a major challenge and threat to GNSS, particularly from encroaching L-band 5G cellular systems. Tallysman offers tightly filtered LNAs and single-band omnidirectional anti-jam antennas with a deep null at low elevations. We plan to introduce a new multiband omnidirectional antijam antenna in the second quarter of 2021.

Taoglas

With Dave Ghilarducci, VP of Worldwide Engineering

Specific challenges
Our antennas are designed for key internet of things (IoT) verticals. Our high-precision, multi-band GNSS antennas offer centimeter-level positioning and timing accuracy for applications where small size and high performance are required. We address the industry’s most compact form factors with out-of-band rejection for operation near transmitters.

Key innovations
Over the past three years, we have focused development on a portfolio of GNSS antennas with centimeter-level positioning accuracy in different form factors:

• 

  EDGE Locate GNSS with RTK. (Photo: Taoglas)

  lighter, more robust antennas through our patent-pending Terrablast-based products (the GGBTP.35); which are impact resistant and 35% lighter than traditional ceramic patches

• developing low-cost, compact, high-performance, multi-band antennas for OEM integrations (XAHP.50, AA.200, GPDF5012).
• high-rejection internal patch modules for rejection for OEM integrations (AGGBP.SL and AGGBP.SLS series)
• surface-mount active patch antennas with embedded active circuitry for easier integration (ASGGB Simplicity series)
• off-the-shelf module with an integrated multi-band RTK antenna, electronics and receiver technology for ease of integration.

Over the next three years, we expect to expand our portfolio and support additional bands like E6, L6 and the L-band correction band. Plus, we are working with the European Space Agency to design IoT devices with integrated high-precision RTK and GNSS technologies.

Advances in RTK and PPP
Expansion of RTK, PPP and similar technologies into new domains has demanded better performance from mainline and OEM antennas. These correction technologies stress antenna gain and polarization purity to maximize signal strength. We address these issues in our integrated designs to mitigate multipath errors and maximize ease of integration.

Technical challenges and industry trends
The release of lower-cost multi-band receivers and modules could be the most significant shift the GNSS industry has seen in the last decade. This innovation is already expanding applications and challenging suppliers to provide better performance for size, weight and cost.

Topcon

With Alok Srivastava, Senior Director, Product Management, Topcon Positioning Group

Specific challenges
Topcon is a proven provider of GNSS antennas for innovative products. Our GNSS product portfolio offers antennas with excellent multipath mitigation, near-band interference rejection, and quality signal tracking from zenith to the horizon. We strive to provide affordable solutions for our geodetic, machine control and agricultural customers.

Key innovations
Topcon antenna technology is applied within standalone antennas along with integrated GNSS receivers. Antennas inside our integrated receivers, such as the HiPer HR, are distinctive in supporting Bluetooth and Wi-Fi in a common antenna stack without sacrificing GNSS tracking and positioning performance. These offerings also support compact designs of integrated receivers.

As the number of GNSS constellations expands and new communication methods become available, potential inference from neighboring signals grows with congestion of the RF spectrum. Our standalone antennas, PN-A5 and CR-G5 with cavity filter option, uniquely address these challenges.

Topcon’s PN-A5 semi-hemispherical ground plane GNSS antenna. (Photo: Topcon)

In the coming years, antenna technology will need to stay strongly focused on interference rejection and mitigation, lower cost and smaller size. These demands challenge antenna providers to make technical advancements while investing in cost-sensitive manufacturing along with higher testing standards. In this regard, our new antenna test facility in Concordia sulla Secchia, Italy, will soon be offering robotic calibration services.

Advances in RTK and PPP
With increased demand and services available for PPP, Topcon antennas support both GNSS and L-band frequencies, such as in the HiPer VR/HR receivers, and standalone antennas (PG-F1, G5-A1, PN-A5 and CR-G5). As data communications continue to expand beyond L-band and RTK/network RTK, Topcon systems will support them without compromising positioning performance.

Technical challenges and industry trends
As GNSS antennas are one of the integral items within the GNSS system, the significance of delivering a cost-effective and miniaturized solution that provides robust positioning is critical to meeting needs in ever-growing precise positioning markets and applications. Topcon will continue to emphasize innovative antenna products through our research.

Trimble

With Stuart Riley, Vice President of GNSS Technology

Specific challenges

Each application has different requirements. For applications that require the highest position accuracy, the stability of the phase center, multipath mitigation, and the unit-to-unit production consistency are critical.

Some markets require high performance, and often in challenging environments such as high vibration experienced on construction equipment. Other customers require smaller, lower cost antennas and can tolerate a slight accuracy reduction.

The antenna is typically a combination of a passive antenna element with an active low-noise amplifier (LNA). The LNA needs to be carefully designed to remain linear in the presence of in-band jamming while rejecting out-of-band signals.

Key Innovations
For high-precision applications, Trimble first released the Zephyr series of antennas in the late 1990s. This antenna provides excellent phase center stability and unit-to-unit production repeatability; the antenna has exceptional multipath mitigation performance, which is enhanced in the geodetic version.

Since the Zephyr was first introduced, we have added support for additional GNSS systems and RF bands (L1/E1, L2, L5/E5 and L6/E6), transitioned to a RoHS-compliant manufacturing process, improved the LNA performance, developed rugged versions for construction vehicle mounting, and produced a smaller version used in the Trimble R10, R12 and SPS986 GNSS receivers.

More recently, we developed a lower cost high-performance antenna for the Trimble Catalyst software-defined GNSS receiver for Android phones and tablets. We also introduced an antenna in the Nav-900 guidance controller for agriculture that implements a meta-material design.

Looking forward, we will continue to innovate by providing antennas optimized to meet the needs of the markets, including cost, performance and morphology. Enhancements will include novel antenna architectures, production technique improvements, and careful material selection.

Advances in RTK and PPP
Applications for GNSS are expanding to include more non-technical users, and the markets are calling for small, light and low-cost antennas — especially for technologies like PPP and positioning products such as Catalyst. These requirements extend across all arenas, especially in applications served by RTX. The needs must be balanced against increased technical demands stemming from the expansion in GNSS bands supporting new frequencies and signals, including PPP correction data.

Technical challenges and industry trends
The challenges come in balancing seemingly conflicting needs for performance, size, weight and cost for the various applications.

Because Trimble focuses on specific user segments, we can provide antenna solutions that are the best fit for the various applications. For example, an antenna in a handheld device must be small and lightweight; however, on a construction machine, durability takes precedence over size and weight.