PCTEL Inc. has launched a new series of multi-GNSS L1/L2/L5 antennas for precision navigation and timing.
According to the company, the antennas combine aerospace-level precision with global satellite compatibility, in a highly durable package. They enable critical applications including vehicular automation, 5G network timing synchronization and Positive Train Control (PTC) systems.
The company made the announcement at the RSSI C&S Exhibition (Railway Systems Suppliers Inc.) being held this week in Omaha, Nebraska.
PCTEL’s multi-GNSS L1/L2/L5 antennas increase the accuracy of timing and location information by providing simultaneous access to multiple GNSS signals across multiple frequency bands. The antennas support all relevant GPS, GLONASS, BeiDou and Galileo frequencies with excellent multipath mitigation and high out-of-band rejection for greater signal clarity, the company said. Their robust AAR and IP67-compliant design makes them suitable for years of use on railways and in other harsh real-world environments.
“Precision navigation is crucial for the next generation of autonomous vehicle technologies, which could drive major improvements in safety and efficiency across a wide variety of industries,” said Rishi Bharadwaj, senior vice president and general manager of PCTEL’s Connected Solutions group. “PCTEL’s new antennas make precision navigation accessible for large-scale deployments in rail, public safety, agricultural and commercial fleets. They also enable commercial deployments of 5G networks, which have higher accuracy requirements for network timing.”
Earlier this month, PCTEL released its 900-MHz MIMO Yagi antennas with dual polarization., designed for use with MIMO or diversity radios in advanced supervisory control and data acquisition (SCADA) systems and other industrial internet of things applications. PCTEL’s dual polarized antenna technology improves data throughput and reliability on both licensed and unlicensed spectrum.
PCTEL is displaying its new multi-GNSS antennas along with other antenna solutions for the rail industry, May 22-23 at the RSSI C&S Exhibition, booth #1109. The new antennas will be available for purchase in mid-July.
AUVSI Xponential was a big show once again — 8,500 attendees, more than 600 exhibitors, 200 educational sessions and 400 speakers. The show floor was huge as usual, with virtually every kind of UAS product and service imaginable for inspection at small, large and larger booths or display areas.
The morning kick-off presentation on Tuesday was enthusiastic about the coming large-scale adoption of drones and associated robotic technology, with a couple of real-time examples — driverless vehicles at Babcock Ranch in Florida and drone supply deliveries for humanitarian aid in Rwanda.
A view of show floor.
However, there still remain a number of barriers to wide-scale integration of drones into daily life from a regulation perspective, as Steven Bradbury, general counsel of the U.S. Department of Transportation, pointed out — while at the same time also indicating that the Federal Aviation Administration (FAA) has granted hundreds of waivers where the safety case has been adequate for lots of commercial UAS operations.
Most of the major GNSS players were exhibiting at the show, so we focused on gathering their news while also collecting a flavor of the many drone system suppliers in attendance.
U-blox introduced its new ZED-F9P multi-band, multi-constellation chip — with GPS, GLONASS, Galileo and BeiDou signal reception and processing and on-chip multi-band RTK with fast convergence times — promising centimeter-level accuracy and low 85 mA (4x GNSS) power consumption in a 17 mm x 22 mm package.
ZED-F9P signals: coverage added in two stages. Option A – available now. Option B – available Q2/2020.
Initial urban testing in Finland in challenging conditions has indicated RTK performance at 9 cm 94%, with high availability, short convergence times (<10 seconds) and fast reconvergence. This kind of performance is apparently initially targeted at automotive applications — u-blox is a member of the Sapcorda automotive group — and is forecasting samples for this July, with production beginning before the end of this year.
The NovAtel tagline for the show was “Assured PNT,” which matches many U.S. and International agency objectives — this was accompanied by several announcements for both commercial and government agency products and applications.
The integrated E1 package includes NovAtel’s SPAN technology, which optimizes positioning and attitude performance during extended GNSS outages. Both new PwrPak enclosures come with the Interference Toolkit advanced interference detection and mitigation capability.
With most UAVs, the electronics on the airframe can produce a disruptive internal interference environment, and can lead to potential problems for the integration of sensitive GNSS. To help overcome this issue, NovAtel has released the OEM7600 receiver board in an extremely small form factor, enclosed with protective shielding to reduce the effects of emissions from nearby electronics.
The 7600 comes with 555 channels, multi-frequency/constellation positioning; L-band support for TerraStar corrections; serial, USB, CAN and Ethernet interfaces; advanced interference detection and mitigation features; RTK; GLIDE and Steadyline firmware options with 20-g vibration rating and the option to add integrated SPAN GNSS + inertial.
NovAtel also announced Inertial Explorer Express, which provides the same core processing and utilities as Waypoint Inertial Explorer software for applications including unmanned aerial vehicles (UAVs) and smaller projects. Inertial Explorer Express will produce centimeter-level position and attitude solutions for lidar, camera and other sensor data with faster processing times and reduced complexity.
On the government/agency business side of the house, NovAtel has been quite successful with the GAJT antenna, which includes integrated anti-jam technology. GAJT is in use operationally and has been shipped to 16 allied nations around the globe, with the latest success being with the artillery Observation Post Vehicles (OPV) for the Canadian Army.
The NovAtel GAJT-710ML GPS anti-jam antenna.
The Type 26 Frigate of the British Fleet will use NovAtel anti-jam technology. (Photo: BAE Systems)
Canadian OPVs are used on the front-line of combat, so its essential that their location and timing information should not be compromised by enemy jammers. The NovAtel GAJT is readily retrofitted to existing vehicles to provide the necessary jamming defense needed by front-line forces.
Previously, NovAtel also announced the selection of GAJT for the UK fleet of Type 26 Frigates – providing essential anti-jam protection for its onboard navigation system.
MB-Two module by Trimble.
Chris Wheeler and Omar Subra were good hosts when we visited them at the Trimble booth — Chris first made a YouTube video for GPS World (see below) and then gave me some insights into what’s new.
Basically, the OEM line has rolled over new versions of almost all individual receiver boards, with the addition of the BeiDou B3 frequency, capability for RTX PPP (precise point positioning) corrections, the addition of new constellations and inertial integration options.
An updated MB-Two receiver module can be configured for single frequency GPS through to dual frequency GPS, GLONASS, QZSS, Galileo and Beidou, uses RTX PPP and has an improved RTK engine for cm positioning from a base-station, or from over-the-air RTK corrections, or provides relative RTK against a moving base.
A typical Trimble application could include capturing an Insitu ScanEagle UAV in a difficult shipboard multipath environment with integrated GNSS-inertial, UAV navigation and control, UAV payload stabilization, or providing a “truth-system” for autonomous unmanned ground vehicles.
Since last year when Trimble introduced a “cell-phone” software receiver application, one useful application could have involved an insurance company using a “pocket-carried” antenna (with integrated RF) for field incident assessments. The cell-phone software license would be transferable to other assessors in the department, while a few pocket antennas are available for the whole assessment crew. This saves purchasing a whole load of hardware, and being limited to where the functionality can be moved or deployed. Everyone has a cell phone, and the relatively inexpensive antenna/RF can be available to all needing them.
Watch this video to learn about Trimble’s latest products, including its BD990 and BD992 GNSS receiver boards.
Trimble is also ramping up its OEM customer service and repair capabilities to improve turn around for multiple customers and applications in the field. Improved results are beginning to help customers and its OEM business, while increased R&D investment is expected to put new products into the field in the fall.
This year Intel’s emphasis continued to be on how to manage the huge amount of data that high-precision visual and multi-spectral cameras are gathering by UAVs carrying out asset inspections for their customers. The Intel view is that this data is useless to an end-user unless it is interpreted and presented in a format that can be readily understood and used for the purpose it was intended.
Let’s say a company operates 75 drones inspecting installations it owns or operates across several states, and that 50 GB of data is the nominal amount of data each drone collects on each mission. That means that nearly 4 TB of data could be collected daily if all 75 drones operate at once. More likely, over 1 TB daily shows up in a central location — a huge amount of unprocessed data.
In a live demonstration, Intel showed how a typical installation inspection — by a drone taking high-resolution still photos at a remote location – could be collected and managed. Once in an Intel processing environment, the data quickly became visual format in 2D or 3D, and could be accessed remotely by an inspection team, saving significant travel costs and time to actionable results.
Intel also promised to soon exceed its record at the Pyeongchang Winter Olympics for the number of drones flown at once — currently set at 1,218 drones. The company’s next target is for a light display using 1,500 multi-colored drones.
Insitu CEO Esina Alic
Insitu held a media event at the show to announce its ScanEagle-3 drone system. Esina Alic, the new Insitu CEO, led a team who introduced and then unveiled the new commercial-standard ScanEagle variant.
This new variant has grown out of 20 years of experience and 15 years of working with the FAA to enable integration of drones into the U.S. National Airspace System (NAS). The ScanEagle-3 (SE-3) has been rebuilt with the objective of developing a certifiable vehicle with increased payload and endurance capability that is free of any ITAR restrictions — allowing export without restrictions to the rest of the world.
Insitu unveils the ScanEagle-3 is at Xponential 2018.
SE-3 features include:
Significantly increased (x2) payload
Still provides for full integration of all existing payloads
Commercial, non-ITAR product for the global market
Long-endurance platform
Service contracts available
Product release in Q2 2019
Fully compatible with existing launch and recovery systems
Around ~100 lb without payloads
ScanEagle variants were used in emergency response to the California wildfires at Santa Rosa and Medicina, gathering real-time information for fire-line combatants.
ScanEagle helped fight these wildfires using High Accuracy Photogrammetry (HAP) sensors. Military-grade electro-optical (EO) cameras during daylight and infrared (IR) cameras for night-time imaging extended the time available for tracking fire lines. Penetrating smoke or darkness, these UAVs gathered video and still images that were used to create geo-referenced, high-resolution digital fire progression and suppression maps to guide firefighting on the ground.
This small overview of Xponential 2018 attempts to provide a flavor of the breadth of activity we saw at the show last week. A good portion of this has also been captured through short videos published on the GPS World website, along with news articles.
There is more to come, with a report to follow from the show on Septentrio’s new product releases, Spirent’s GNSS simulation demo, DJI’s overview of drone products featured at the show, CyPhy Works tethered drones, Swift’s announcement of its Skylark correction service trials, Hemisphere’s new Vector Smart Heading Antenna, and Harxon’santennas for drones.
A big show to cover, that’s for sure! It’s a good sign that people were perhaps talking more business than in previous years and a sign that the UAS industry is perhaps moving into its next growth phase.
Harxon showcased high-precision positioning GNSS antennas and its latest wireless data-transmission technologies for UAV applications at AUVSI Xponential, which was held April 30-May 4 in Denver.
The Harxon D-Helix Antenna.
Harxon’s D-Helix is a patented D-QHA (dual-quadrifilar helix antenna) multi-constellation antenna supports excellent reception of GPS, Galileo, BeiDou and GLONASS, as well as L-band signals. Harxon D-QHA technology ensures the ability of low elevation satellites tracking while maintaining 4-dBi high gain, which makes the D-Helix antenna an excellent choice for any applications where the sky is partially visible, the company said.
The antenna’s low noise amplifier (LNA) with out-of-band rejection performance can suppress electromagnetic interference. Moreover, the D-Helix features the latest low wind resistance design with ruggedized IP67 protection for UAV inspection and monitoring, survey and mapping or agricultural UAVs.
Photo: Harxon
The HX-DU2017D is a 5-gram frequency-hopping OEM transceiver supporting frequencies between 840 MHz and 900 MHz. It provides strong anti-jamming and signal receiving capability for complex data intensive applications. Its full duplex mode ensures data secure transmission, more stable long-range communication and short latency of data transmission.
Watch this video to learn more about the HX-DU2017D.
Other showcased Harxon GNSS products, such as Helix Antenna HX-CH7603A, HX-CH4601A and HX-CH6601A, are all featured with patented D-QHA technology. Moreover, the showcased Survey Antenna GPS 500, OEM Modem HX-DU1018D and Smart Antenna are also appropriate for surveying and mapping, as well as precision agriculture.
Airgain Inc., a provider of advanced antenna technologies used to enable high-performance wireless networking, has released its Ultramax MIMO 9-in-1 antenna, which can receive multiple GNSS signals.
Designed for public safety fleet management, it provides high rejection GNSS technology with coverage for multiple satellite systems including GPS, GLONASS, Galileo and BeiDou.
The new Ultramax MIMO 9-in-1 antenna will help improve public safety and fleet solutions with enhanced Wi-Fi capability, the company said. It includes 6 x 6 MIMO Wi-Fi, dual LTE and multi-GNSS technology antennas in a single enclosure.
MIMO — multiple input multiple output — is used within LTE to provide better signal performance and higher data rates. With integrated 6×6 Wi-Fi antennas, the antenna provides support for full high-definition (HD) streaming video and other high bandwidth applications.
The antenna is the first in an Airgain series designed to support state-of-the-art communications technology in fleet routers, including the Cradlepoint IBR1700.
The Ultramax MIMO 9-in-1 antenna is equipped with nine ports, supporting tri-band Wi-Fi, LTE/MIMO (including Band 14 for FirstNet) and GNSS. With a single compact footprint, the antenna avoids multiple mounting and cable entry points.
“Technology advances in routers, including enhanced Wi-Fi and expanded MIMO LTE, require enabling antenna technology to deliver an optimized end user experience,” said Reed Pangborn, vice president of channel sales for North America. “We designed a new antenna to support the fleet management applications required in today’s evolving mobile environment. The Ultramax MIMO 9-in-1 antenna demonstrates our commitment to providing leading antenna solutions for our mobility customers covering a wide range of vehicles, including police, fire, ambulance and other fleet assets.”
The Ultramax MIMO 9-in-1 antenna complements Cradlepoint’s IBR1700 and supports all six of its Wi-Fi ports.
Airgain will unveil the new antenna at the Cradlepoint Global Partner Summit in Scottsdale, Arizona, April 11-12. The Ultramax MIMO 9-in-1 antenna will be available to order starting in June.
Designed primarily for applications such as homeland security, Spectracom’s 8230AJ antenna provides protection in high-interference environments where additional resilience is needed, such as communications networks, financial systems and power grids, the company said.
Orolia, through its Spectracom brand, said the antenna, Model 8230AJ, is a drop-in replacement for the company’s Model 8230. Its conical antenna pattern rejects interference from the horizon and is simple to mount using the same pipe supports, without new cabling. All that is required is a new bracket.
“Model 8230AJ is a high gain (40 dB) GNSS outdoor antenna covering GPS L1, GLONASS L1, BeiDou B1, Galileo E1, and QZSS L1,” said David Sohn, product manager at Spectracom. “It uses a three-stage low noise amplifier, a mid-section SAW, and a tight pre-filter to protect against saturation by high level sub-harmonics and L-band signals. It is designed especially for harsh environments, is IP67 rated, and improves resilience and protects against jamming and spoofing.”
According to the company, the AJ antenna rejects signals for the lower elevation angles – where most interference comes from – and only receives signals from the higher elevation angles where the satellites are. While this reduces the number of satellites the receiver will see, for timing applications only a few satellites are needed. Moreover, with multi-constellation receivers, an increasing number of satellites are available.
With the increasing prevalence of jamming and spoofing, industries with critical infrastructure must take measures against interference. GPS and GNSS in general have well-known vulnerabilities and limitations that require protection and mitigation: the signals are easily disrupted by unintentional interference from radio transmitters, they are extremely weak, cannot penetrate buildings and can easily be jammed, and civilian signals are not encrypted and can easily be spoofed.
The new anti-jam outdoor antenna is appropriate for anyone who uses a time server, including Spectracom customers who own a SecureSync, VersaSync or Netclock, according to the company.
In mid-2017, Talen-X and Skydel engineers began to conceptualize a GNSS simulation system emanating from their BroadSim platform for the purpose of fortifying anechoic chambers.
Over the next six months, Talen-X and Skydel designed, built, tested and delivered an anechoic chamber simulator capable of simultaneously generating multi-GNSS jamming and spoofing signals.
BroadSim Anechoic can be used to support a wide variety of operational tests.
“Our new Anechoic Chamber solution will radically change the way in which mission critical platforms and systems are tested because we are enabling our customers to create real-world threats,” said Talen-X Chief Technology Officer Tim Erbes said. “Not only will BroadSim Anechoic be able to emulate real-world threat scenarios, it will be easier than ever before to create and simulate these environments.”
BroadSim Anechoic is used to test GNSS spoofing and jamming in an anechoic chamber. The BroadSim Controller is at the heart of the system running Skydel’s SDX software suite. Using SDX, users can create advanced scenarios that include both jamming and spoofing signals.
The 16 software-defined radios (SDRs) each with dual transmit ports (32 total outputs) can be configured to output GNSS or jamming signals, giving users flexibility to run test after test. The transmit chains include the hardware to power 16 dual-frequency antennas. The included GNSS receivers allow users to monitor the environment inside the chamber, providing confidence that tests are running correctly.
The BroadSim Anechoic can also be used in controlled radiation pattern antenna (CRPA) testing. Many ground-, airborne- and water-based platforms are transitioning to using CRPAs because of their added jamming resiliency and significant tracking advantages in degraded environments.
Validation and real-world testing is critical to understanding and characterizing the mitigation these antennas can add in highly degraded areas. By using BroadSim Anechoic, users have the ability to create representative jammers with real-world characteristics (modulations, frequencies, angles, power levels, etc).
“Skydel developed an innovative approach for time offset calibration between multiple transmitting antenna using a COTS Software-Defined Radio (SDR),” said Skydel Solutions Chief Technology Officer, Iurie Ilie. “This approach allows for very precise measurements and adjustments (better than 100ps) to be done automatically before simulation start. At the same time, transmitting signal power is automatically adjusted to keep the power offset at receiving antenna better than 0.1dB.”
BroadSim Anechoic takes advantage of state-of-the-art software defined radios (SDR) for RF up-converting while signal IQ generation is done using high performance commercial-off-the-shelf (COTS) graphics-processing units (GPU). The ability to generate the IQ data in software (using the GPU) as opposed to hardware (FPGA) significantly reduces the cost while maximizing capability, value, and time to market.
BroadSim Anechoic has the capability of powering up to 16-dual frequency antennas requiring 32 RF transmit outputs. The architecture used for this system required the ability to receive signals in a manner such that precise processing could be done on the receive signal.
The SDR selected for this application has one receiver channel for every transmit channel giving BroadSim Anechoic 32 RF receive ports. Innovative software techniques have been developed enabling the accurate time and power calibration for each antenna transmit chain using the SDR receive ports.
Q: What are the key criteria in selecting a GNSS antenna for a particular application?
Jerry Freestone, Chief Engineer, Antennas and Anti-Jam, NovAtel
A: Performance, size and cost. Size and cost are easy for the integrator to assess; determining the necessary antenna performance to achieve the desired system-level performance is difficult to evaluate. Obtaining the complete GNSS solution from a single source is ideal; vendors that sell both antennas and receivers will generally understand the minimum system-level performance their solutions can provide for a given application and deliver the optimized solution to meet all three criteria.
Brandon Oakes, Director, North American Sales and Marketing, OriginGPS
A: Antenna selection for GNSS applications must consider performance, size and cost. Successful GNSS deployments start with the antenna selection in mind rather than waiting until the end and letting other design constraints drive the antenna selection. Patch antennas are always our preferred solution due to polarization, robustness and our patented integration method that minimizes bandwidth shift. Chip antennas are attractive due to their size, but consideration must be paid to ground-plane size and detuning.
This comment piqued my ears when heard over the coffee-break table at ION’s International Technical Meeting last month: “There is a great deal of mutual ignorance between the 5G and PNT communities. I think that the 5G people are pretty naive about PNT and the PNT community is missing an opportunity.”
So when news releases leading up to next week’s Mobile World Congress — several of them mentioning 5G in rosy terms, “catalyst for a better future” typical among these — started flooding my inbox this morning, it seemed an opportune time to investigate. Pardon my top-slice view; I’m not well-versed enough in the technology to discourse knowledgeably, but here’s quick round-up of salient points related to positioning in the fast-oncoming Next Step in cellular communications.
Regular contributing editor for Professional OEM and UAV Tony Murfin will return to this space next month, with a column previewing the massive AUVSI Xponential show in Denver, April 30–May 3. He’ll be there, too, covering the event!
The cellular 5G standard has been designed to target latencies under one millisecond, data rates of up to ten gigabits per second, extremely high network reliability, and better accuracy in positioning. With location awareness becoming an essential feature of many new markets, positioning is consequently considered as an integral part of the system design of upcoming 5G mobile networks.
Its feet firmly planted in both the present and the future, the cellular industry is currently in the midst of implementation of Long Term Evolution (LTE)-Advanced, an evolution of what might be called plain old LTE, and a “true 4G” mobile broadband. Simultaneously, the industry is preparing the next step, as “there is a vastly increased need for a new mobile communications system with even further enhanced capabilities, namely a fifth generation (5G) system.” 5G will process communication 10 times faster than 4G, according to experts. That’s enough to download a 3D movie in 30 seconds. It would take six minutes on 4G.
Pyeongchang
Alert techie viewers of the present ongoing Olympics in South Korea may have noted 5G in action there, in demos of such things as live-streaming virtual reality of bobsled and luge runs, putting the viewer in the breathtaking driver’s seat, and a test drive earlier this month from Seoul to Pyeongchang, a journey of several hours, without any human intervention whatsoever at the car’s controls. The demonstrations in Pyeongchang are laying down a backbone for what will be on show at the Tokyo Games in 2020, when 5G roll-out will be complete in many major metro areas.
As trumpets sound the fanfare for next week’s Mobile World Congress in Barcelona, AT&T announced it will first roll out 5G to three locations: Dallas, Texas; Waco, Texas; and Atlanta, Georgia. The plans introduce the service to about a dozen U.S. markets by late this year. Qualcomm meanwhile is offering insight into its 5G chips.
What has all this got to do with GNSS? Well, aside from the aforementioned precise positioning via cellular to be afforded by 5G, the two technologies share one prominent technique: adaptive array antennas for digital beam-forming. Here I am indebted to Gary McGraw of Rockwell Collins for a primer on the subject, which he presented at the International Technical Symposium on Navigation and Timing (ITSNT) in November 2016.
Adaptive array technologies have many advantages for PNT: primarily, in mitigation for multipath and for jamming and spoofing mitigation. Adaptive antenna arrays with digital beam-forming (DBF) are becoming increasingly important for PNT in challenging signal environments. DBF combines multiple antenna inputs to generate gain in arrival direction of the desired satellite signal and to create spatial nulls in direction of jamming.
Emerging applications of DBF in 5G involve dense networks of picocells, small cellular base stations typically covering a small indoor area. Picocells extend coverage where outdoor signals do not reach well, and add network capacity in areas with very dense phone usage. In this context, 5G cellular architectures will use adaptive array technology to achieve high data rates, spectrum reuse and communications robustness.
The implications for PNT are that 5G system architectures will require improved (relative) PNT to operate effectively, and these 5G picocells will be a source of PNT information in constrained environments.
5G involves massive directional communications via multiple-input multiple-output (MIMO), enabling high-bandwidth communications in fading (multipath) channels by using multiple antenna inputs to adapt to channel. It can do this without knowledge of user location, but it adds to the processing complexity. The directional capability can enable multiple users to be serviced in a picocell at different frequencies, while permitting spectrum re-use by nearby picocells through narrow beam-width and the limited range of millimeter-wave frequencies.
The PNT implications of 5G architectures, according to Gary McGraw of Rockwell, are, principally, that efficient operation of directional links will require some level of knowledge of user location with regard to picocells. Picocells will need to have the ability to do direction-of-arrival positioning and ranging in order to maintain connectivity with user nodes. This can be exploited by the user node for positioning and location-based services, particularly for indoor and dense urban environments. Meanwhile, the proliferation of adaptive array technology will drive down costs for other applications. Further, millimeter-wave transmit/receive modules will become commodity items, analogous to what cell phones have done for GPS chips.
McGraw’s Summary
5G picocells will be synergistic with PNT in challenged environments — naturally, indoor and dense urban. They will necessitate development of distributed, networked PNT processing and infrastructure. Availability of adaptive array technology will increase with deployment of 5G, and costs can be expected to drop dramatically. In addition to GNSS, adaptive array technologies can be employed to support short-range, relative PNT applications such as vehicle-to-vehicle communications and relative positioning.
Driving the Bus
The key driver for all this is that customers, the global We, expect the same quality of experience from Internet applications anytime, anywhere, and through any means of connectivity. The rapid proliferation of smartphones and other mobile devices that support a wide range of applications and services mean that image transfer and video-streaming, as well as more cloud-based services, such as cloud speech services, have become the new norm. Their requirement for massively more data than, say, simple texting is conveniently hidden from or forgotten by users. We want it. We want it now.
From a DOCOMO 5G White Paper: 5G Radio Access: Requirements, Concept and Technologies. NTT DOCOMO, INC., July 2014. At https://www.nttdocomo.co.jp/english/binary/pdf/corporate/technology/whitepaper_5g/DOCOMO_5G_White_Paper.pdf.
Tomorrow, or perhaps the next day, everything will be connected by wireless to enable monitoring and collection of information and control of devices. Thus, remote monitoring and real-time control of nearly all electronic devices in machine-to-machine (M2M) services and Internet of things (IoT): connected cars, connected homes, moving robots and sensors. Such services will become more extensive and enriched through richer content delivered in real-time. Get set for the tactile Internet, augmented reality, and other brave new wonders.
Fraunhofer Enters the Fray
The 5G positioning framework will thereby integrate a multitude of sensors based on both, cellular signals and 3GPP independent techniques, into a hybrid positioning scheme, according to the Fraunhofer Institute for Integrated Circuits (IIS) in Germany. Fraunhofer IIS is currently prototyping low-latency and high-precision positioning systems for legacy LTE and future 5G New Radio (NR). Two selected industrial IoT live demonstrations can be seen at next week’s Mobile World Congress 2018.
Respective positioning performance for 5G NR and other technologies in different environments. (Image: Fraunhofer IIS)
5G NR enables positioning performance by providing high bandwidths for precise timing, new frequency bands at mm-wave, massive MIMO for accurate angle-of-arrival estimation and new architectural options that support positioning. Improved levels of accuracy, robustness and latency, not possible today, can soon be achieved, according to Institute. 5G provides fast and reliable access to moving objects, to achieve time-critical process control and optimization in industrial environments not possible with today’s cellular technology. As requirements vary according to the specific use cases, 5G NR will provide a flexible air interface allowing for scalable bandwidths, data rates, latencies, and positioning accuracy levels.
High-Precision Positioning
With location awareness becoming an essential feature of many new markets, positioning is an integral part of the system design of 5G mobile networks. Increased contextual awareness of goods, parts, machines and workers will enable new interaction and collaboration.
High-precision positioning, in the view of Fraunhofer IIS. (Image: Fraunhofer IIS)
Fraunhofer IIS is working on novel approaches for sub-meter accuracy to enable tracking of mobile devices in indoor and urban areas where GNSS is not sufficiently accurate nor available. Its 5G positioning framework integrate several sensors. The key benefits of 5G in this regard are high accuracy, reliability, mobility and coverage; low latency and low power; and scalability.
The Institute offers the facilities of its Test and Application Center L.I.N.K. in Nuremberg, Germany. The test center includes a 3D positioning system capable, according to the organization, of reproducing, simulating and emulating all kinds of possible environments, using every common communication and positioning system commercially available.
Helix Technologies Ltd. has been awarded a significant contract by the European Space Agency (ESA) to develop its next-generation GNSS antenna — a multi-frequency antenna optimized for the advanced Galileo E1 Alt-BOC and wide-band E5 Alt-BOC waveforms for use in driverless cars.
The antenna, to be developed under the ESA’s Navigation Innovation and Support Programme (NAVISP), will provide enhanced performance due to its dielectric, multi-filar construction. It will also be optimized to take maximum advantage of the Galileo E5 Alt-BOC waveform, which enables significantly improved measurement accuracy, precision and multipath suppression over conventional GNSS signals.
Learn more about the Helix Technologies antenna in our February issue article here.
“In order to achieve the 10-centimeter accuracy that is required for autonomous vehicle lane-level positioning within challenging urban multi-path propagation conditions, there is a need both for a significant improvement in current GNSS antenna performance and to fully exploit the advanced Alt-BOC waveforms transmitted by Galileo,” said John Yates, managing director of Helix Technologies.
The GNSS antenna, which will also be capable of optimized operation with the GPS L1 and L5 M BOC signals, is aimed at the automotive and consumer markets, and the company is targeting the third quarter of this year for the manufacture of prototypes.
Independent testing and evaluation of the vehicle-mounted antenna performance will be conducted in the challenging multipath environments of the high-rise financial districts of the cities of London and Shanghai.
By Oliver Leisten Technical Director, Helix Technologies Ltd.
To attain the 10-centimeter accuracy required for autonomous vehicle positioning within urban multipath propagation conditions, there is a need for a significant upgrade in GNSS antenna performance. The autonomous vehicle application demands excellent antenna performance together with exploitation of the full set of GNSS multi-frequency and multi-constellation system advances to deliver this performance paradigm in the most severe of real-world use scenarios.
Given that an antenna necessarily operates in open fields, it follows that field resonance must be managed to provide predicable performance in diverse use-scenarios. A new antenna developed by Helix Technologies (Figure 1) deploys balanced fields across a cylindrical ceramic dielectric core to constrain the outreach of resonance fields and thereby minimize the interaction with nearby objects. The antenna feed is designed to provide enforcement of balanced operation, which ensures that the antenna resonates predictably and independently of the platform (i.e., the vehicle in the case of autonomous driving). Thus, the operation is not significantly influenced by the mechanical or material properties of the platform or housing. This architecture provides isolation from common-mode signals and protects the GNSS signals from conducted interference.
Figure 1. Features of the hexafilar-turnstile solution for multi-frequency GNSS.
It is challenging to configure a GNSS antenna operating at many frequencies in which the performance at any one frequency is not impaired by mode interactions. Such impairments can have serious consequences for the position accuracy in an urban environment because they adversely affect the cross-polar discrimination: a parameter which is most important for eliminating multipath positioning errors. The architecture of the hexafilar-turnstile antenna has overcome this problem and delivers the circular polarization pattern characteristics illustrated (simulated data) in Figure 2.
Figure 2. Simulated RH circular polarized patterns at GPS L1 (left) and GPS L2 (right).
The figure demonstrates that the antenna is forming cardioid patterns at two frequencies. The 3D graphic is intended to show the omni-directionality and the 2D elevation cuts exhibit the signature cardioid shape which characterize a “spinning-dipole” circular polarization antenna.
It is often suggested that patterns of wide beam-width such as these would not be particularly suitable for positioning in urban canyons where the sky can only be seen in a relatively small solid angle. In fact, the ratio of front-to-back gain is strongly associated with the cross-polar discrimination that is important for position accuracy in urban environments. Patterns of this quality can deliver as much as 30-dB of signal-to-interference advantage in favor of the direct-path satellite signals against signals whose polarization has reversed due to multipath reflection.
Helix Technologies is developing antennas which have two-pole frequency responses that provide two frequencies of optimum cross-polar discrimination that are aligned to the two frequencies of maximum spectral density of an M-BOC or Alt-BOC coded signal, as transmitted by the modern GPS and Galileo satellites respectively. These antennas should be available for test and evaluation in Q2 of 2018.
More satellites, more constellations, more multi-frequency receivers — they all drive greater achievable accuracy. But they also raise the requirements on GNSS antennas because of the stronger impact that possible imperfections might have in the overall error budget for multi-frequency combinations. This analysis of antenna-induced errors in pseudorange code measurements for different antenna feed types helps identify the advantages and disadvantages of such technologies for precise positioning.
By Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
The combination of signals from two frequencies and multiple constellations leads to dual-frequency multi-constellation (DFMC) capabilities, which currently appear to provide improved performance, due to the increased number of satellites available. This leads to better available satellite geometries, but also to the possibility to strongly mitigate ionosphere-related errors, thanks to dual-frequency combination of the ranging signals.
In such scenarios, the hardware-related errors (from satellite and even more from receiver side) will gain a much stronger weight in the overall error budget and should be tackled accordingly.
This article focuses mostly on the receiver antenna contribution, leaving the effects due to the satellite and to the receiver for later work. We will show that the choice of the antenna technology (mostly in terms of the number of feeding points) has a strong impact on the pattern uniformity and therefore on the differential group-delay characteristics over the aspect angle. Optimal performance is demonstrated when using more sophisticated solutions, providing a ground for cost/performance analysis to system engineers of specific applications.
GROUP DELAY PERFORMANCE
Antenna performance in GNSS application is mostly evaluated in terms of antenna gain pattern, noise figure and group delay for code measurement or phase center variation for carrier phase measurement. Gain and noise figure impact on the signal level available at the receiver, while the group delay is a measure of the delay introduced by the antenna hardware to the different spectral components of the signal. The differential group delay (DGD) is
(1)
with φ, f, Az, El being respectively the antenna phase, frequency, azimuth and elevation.
The DGD variation with respect to frequency and aspect angle (that is, elevation and azimuth) actually poses a problem in precision applications: as a matter of fact, if the group delay were constant for all frequencies and all angles of arrival of the signal, no additional error would be introduced in the position calculation, because the group delay term common to all satellites would be encapsulated at the receiver into a user clock offset.
However, group delay can change significantly with respect to aspect angle and frequency, contributing in a different manner for each satellite (due to different angles) and for different signals (due to the different spectral components of each signal), therefore finally producing errors in the pseudorange estimation.
The influence of the DGD on pseudorange measurement error has already been studied in the past and is also taken into consideration in the antenna Minimum Operational Performance Standards (MOPS) for avionic antennas. Empirical studies on the combined effect of antenna group delay and multipath effect on board commercial airplanes have been published recently. However, to our knowledge, the correlation between the antenna intrinsic characteristics (such as gain and phase patterns and smoothness) and group delay behavior has not yet been properly analyzed, leaving a gap in the full understanding of the antenna design impact on the final GNSS receiver performance.
GNSS antennas can be divided into families, according to their geometry (and the related radiation mechanisms): for instance, spiral, helix and microstrip (patch) antennas are quite common in GNSS applications.They differ in achievable bandwidth, size and ease of manufacturing.
Even antennas of the same family can provide different performance, mainly because of the number of feeding points, which are the points where the signal is fed into the antenna.
In order to analyze the relationship between the group delay performance and the antenna properties, we will take into consideration three GNSS antennas of the same family (microstrip patch), having all about half-effective-wavelength size (with the effective wavelength considering the dielectric properties of the substrate material on which the patch antenna is positioned), but with a different number of feeding points. The antennas will be denominated respectively single-feed, double-feed and four-feed antennas.
The single-feed antenna is a square patch, with truncated corners to achieve circular polarization. On the other hand, the double- and four-feed antennas are square patches, having feeds positioned along their x- and y-axis. The feeds are fed progressively: that is, with same amplitude and 0°–90° phases for the double feed and 0–90–180–270° phases for the four feed.
Single-feed antennas are representative of lower cost antennas used in mass-market applications, due to their extreme simplicity allowing for low-cost production. However, their performance exhibits strong cross polarization levels and non-uniform patterns over the azimuth. Dual- and four-feed antennas are more complicated to manufacture and need further hybrid circuits to properly distribute the signal between the different feeding points. However, an increase in the feeding points leads to more uniformity in the radiation pattern and lower-cross polarization and can therefore be expected to improve performance.
Dual-feed antennas are common in applications where a balance between precision and cost is needed, while four feeds are used in high-end applications, such as geodesy and reference stations.
The antennas under consideration here have been tuned to obtain optimal behavior at GPS L1/Galileo E1 band and have been simulated in an electromagnetic solver (Ansys HFSS), with an infinite ground plane assumption, to resemble the large metallic body frame of aircraft structures.
The gain patterns of the different antennas at GPS L1 / Galileo E1 central frequency ( f=1575 MHz) are shown in Figure 1. As discussed earlier, the pattern is not uniform over angle for the single-feed solution. On the other hand, the four-feed antenna shows improved pattern uniformity: the pattern has fewer azimuth and elevation variations, with the two-feed solution providing intermediate results.
Figure 1a. 3D RHCP patterns at f=1575 MHz for single-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 1b. 3D RHCP patterns at f=1575 MHz for a dual-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 1c. 3D RHCP patterns at f=1575 MHz for a four-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Phase patterns for the three antennas are shown in Figure 2. Here again, the one-feed solution exhibits more angular variation than the multi-feed solutions. It is interesting to notice how strong phase variations occur in the same regions where the gain pattern also varies strongly.
Figure 2a. 3D RHCP phase patterns at f=1575 MHz for a single-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 2b. 3D RHCP phase patterns at f=1575 MHz for a dual-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 2c. 3D RHCP phase patterns at f=1575 MHz for a our-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
When considering the DGD, the frequency dependence of the phase pattern will have to be taken into account, according to Equation (1). To show the DGD variability with respect to the aspect angle, the standard deviation of the DGD over a 20-MHz bandwidth has been calculated (for each azimuth and elevation angle) and is shown in Figure 3, confirming the better behavior of the four-feed antenna.
Figure 3a. 3D standard deviation (calculated over frequency) of the DGD for a) single-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 3b. 3D standard deviation (calculated over frequency) of the DGD for a dual-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 3c. 3D standard deviation (calculated over frequency) of the DGD for a four-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 4 shows the group delay versus frequency and elevation (with different azimuth values being represented by curves with different colors) for the three typologies of antennas: such typology of figure contains all information about DGD variation versus frequency and angle and is first introduced in this article. For comparison, in the RTCA’s 2006 MOPS document for airborne antennas, for the sake of simplicity, either DGD variation versus angle at central frequency or DGD variation over frequency at zenith were considered, hence not fully covering the complete space {Frequency, Azimuth, Elevation}.
Figure 4a. Differential group delay versus elevation angle and frequency (each color represents an azimuth value) for single-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 4b. Differential group delay versus elevation angle and frequency (each color represents an azimuth value) for a dual-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 4c. Differential group delay versus elevation angle and frequency (each color represents an azimuth value) for a four-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
While the single-feed antenna in Figure 4 shows a big variation of the DGD when moving from zenith (that is, Elevation = 90°) to lower elevations, a substantial decrease in the DGD spread is recorded for the four-feed solution, with the dual-feed one having again intermediate results.
It is worthwhile noticing that the results obtained for the dual-feed solution are in agreement with the current MOPS for L1 antennas (RTCA DO-301), specifying a maximum value of 2.5 nansoseconds (ns) for the group delay spread at low elevations (normalized to boresight, El = 90°).
The results show how angular variation of the DGD can be related to non-uniformity along the aspect angle (Az or El) and frequency, hence suggesting to use multiple-feed solution for obtaining optimal performance.
A useful metric to quantify the uniformity of the group delay can be introduced as the Uniformity Indicator for Group Delay (UIGD):
( 2 )
with being the sum over frequency (Nf is the number of frequency steps considered) and DGDzenith,n being the value of the DGD at zenith for frequency n.
The UIGD expresses the maximum variation of the DGD over elevation and azimuth from a reference condition (the DGD at zenith) in the bandwidth of interest, extending de facto the MOPS requirements by considering the whole bandwidth behavior in the whole upper hemisphere.
The UIGD for the one-, two- and four-feed antennas is respectively 4.18, 1.03 and 0.05 ns, hence effectively mirroring the better pattern uniformity of the four-feed solution.
The UIGD is a comprehensive metric to describe the DGD uniformity, but needs accurate phase measurement over the entire bandwidth, which may not be always easily obtainable. As a matter of fact, phase can be challenging to measure: some indication of the areas most likely to deliver increased DGD can be found while considering gain patterns, qualitatively providing an easier metric to compare different antennas. In this case, the Uniformity Indicator for Gain (UIG)can be used:
(3)
The UIG expresses the maximum value over all elevation and azimuth angles of the standard deviation of the RHCP gain derivative over frequency (in the band of interest), therefore indicating the roughness of the antenna gain pattern in frequency and angle.
Such a metric does not relate totally with DGD behavior, but serves as an easier metric of pattern uniformity. The UIG for the one-, two- and four-feed antennas is respectively 68.5, 5.7 and 0.3%.
REAL-LIFE PERFORMANCE AND IMPACT ON ACCURACY
To evaluate the performance of actual antennas, three prototypes were measured in a Satimo Starlab anechoic chamber at the German Aerospace Center (DLR).
The antennas under test were:
A badly polarized COTS active antenna, having a behavior similar to that of a single-feed antenna;
An in-house developed passive antenna with two feeds;
An in-house developed passive four-feed antenna.
All antennas were properly tuned to obtain optimal gain and minimum reflection losses (input reflection coefficient <–10 dB) at L1 /E1 central frequency.
The measured RHCP pattern for the various antennas is shown in FiGURE 5. The UIGD for these antennas is 0.9, 0.7 and 0.2 ns respectively, while the UIG is 46.6, 38.5 and 9.0%.
Figure 5a. Measured 3D RHCP gain patterns at f=1575 MHz for a badly polarized COTS antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 5b. Measured 3D RHCP gain patterns at f=1575 MHz for a DLR dual-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 5c. Measured 3D RHCP gain patterns at f=1575 MHz for a DLR four-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Differential group delay was calculated from the measured phase values and is shown in Figure 6.
Figure 6a. Differential group delay versus elevation angle and frequency (each color represents an azimuth value) as from measurement for a badly polarized COTS antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 6b. Differential group delay versus elevation angle and frequency (each color represents an azimuth value) as from measurement for a DLR dual-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 6c. Differential group delay versus elevation angle and frequency (each color represents an azimuth value) as from measurement for a DLR four-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
The results are similar to those obtained from simulation and clearly show the improved flatness of the DGD for the four-feed case.
Moreover, if the measured phase data are fed into an ideal GNSS receiver, able to provide the tracking biases occurring in the pseudorange code measurement for all elevations and azimuths, antenna-effects-only (as weighted by the signal characteristics) will be visible (as in this case, neither multipath nor receiver or satellite imperfections are included in the ideal receiver). The results are shown in Figure 7.
Figure 7a. Pseudorange bias versus elevation angle (each color represents an azimuth value) at L1 band for badly polarized COTS antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 7b. Pseudorange bias versus elevation angle (each color represents an azimuth value) at L1 band for a DLR dual-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
Figure 7c. Pseudorange bias versus elevation angle (each color represents an azimuth value) at L1 band for a DLR four-feed antenna. Source: Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)
A substantial decrease in the antenna-induced error is evident as expected when the four-feed antenna is used.
The differences in performance among different antenna technologies shown here provide valuable insight in the choice of the antenna technology for a specific application, thanks to the better understanding of the impact of the antenna characteristics on the error at pseudorange level. Moreover, they can support the evaluation and definition of antenna requirements and connect them to the expected GNSS pseudorange error, such as during the process of MOPS definition as currently occurring for DFMC systems.
CONCLUSIONS
After investigating the effects of pattern uniformity on antenna-induced errors, group delay behavior over aspect angle and frequency has been shown comprehensively for different antenna feeding technologies for the first time. Minimal error in pseudorange measurements is obtained when the antenna has a smooth pattern, with no abrupt variations or nulls/sidelobes both in aspect angle and frequency. Different antenna feeding technologies currently in use for circularly polarized radiation have been evaluated, and the best performing one has been identified in the multiple-feed solution.
Both a comprehensive and an easier-to-measure metric for group delay uniformity have been identified, providing useful insight for fast comparison of the performance of multiple antennas in terms of GNSS accuracy.
STEFANO CAIZZONE received a Ph.D. in geoinformation from the University of Rome, Tor Vergata. He is is responsible for the development of innovative miniaturized antennas in the antenna group of the Institute of Communications and Navigation of the German Aerospace Center (DLR).
MIHAELA-SIMONA CIRCIU received a master’s degree in computer engineering from Technical University Gheorghe Asachi, Romania, and a master’s in navigation and related applications from Politecnico di Torino, Italy. She works on the development of the multi-frequency multi-constellation Ground Based Augmentation System for DLR.
WAHID ELMARISSI received a Dipl. Ing. in electrical engineering from the University of Applied Sciences, Kiel, Germany. He is responsible for measurement and manufacturing of antennas and antenna electronics at DLR.
CHRISTOPH ENNEKING received a MSc. degree in electrical engineering from the Munich University of Technology. He conducts research in GNSS signal design, estimation theory and GNSS intra- and inter-system interference at DLR.
MICHAEL FELUX is a research associate specializing in GBAS integrity issues for CAT -II/III operations and program manager for the research on GBAS navigation at DLR. He graduated in technical mathematics at Technische Universität München.
KAZEEM A. YINUSA received MSc. and Dr.-Ing. degrees in electrical engineering from the Technische Universität München. He is a researcher at DLR.
An experiment in an anechoic chamber with a JAVAD GNSS TRIUMPH-LS shows the approximate orientation of the spoofer (at 283° azimuth.)
Javad GNSS advises that with its equipment it is possible, when a spoofer is detected in the area, to identify the direction from which the spoofing signals are coming.
Hold the receiver antenna horizontally and rotate it slowly (one rotation in 30 seconds) to determine the angle at which satellite energies become minimum.
The spoofer’s direction lies behind the null point of the antenna reception pattern.
An experiment in an anechoic chamber with a Javad GNSS Triumph-LS shows the approximate orientation of the spoofer (at 283 degree azimuth.)
PCTEL Inc. has launched a new series of multi-GNSS L1/L2/L5 antennas for precision navigation and timing.
