Skydel SDX Release 17.1 adds a fine level of control on signal multipath to the software-defined GNSS simulator.
SDX 17.1 introduces a powerful multipath simulation option, enabling users to create less-than-ideal signal propagation conditions for GNSS testing. Multipath echoes can be added and fined-tuned for each satellite, per signal. Control is possible via four fundamental attributes: pseudorange offset, power loss, Doppler shift and carrier-phase offset.
It’s now convenient to create simplified test conditions otherwise impossible to achieve with the live sky. The new options are fully controllable through the SDX application program interface (API), and can be modified on the fly while the simulation is running.Release 17.1 also adds L2C navigation message modification. Besides the usual conditions such as start and stop time and PRN number, users can specify the message type, and the message content to match.
Because the CNAV message is 300 bits long and not subdivided in words like the NAV message, managing the modifications as a per-bit fashion would be tedious. The interface solves this by letting you add modifications for portions of the message — and lets users add as many as they need.
Software-defined radios (SDR) can take a few seconds to initialize when starting the simulation. To improve software synchronization performance, Skydel has added an armed state. Upon clicking the arm button (or issuing the command through the API), the armed state prepares all hardware. When the start command is later received, the delay to emit the GNSS signals is minimal.
Other updates have also been made. See the release notes for the full list. As always, existing licensees benefit from an immediate upgrade.
Among the next items on SDX’s development agenda is the release of advanced jamming capabilities through an innovative integration with the GNSS simulator.
The European Commission and the European GNSS Agency (GSA) confirm that the first generation of Galileo will already provide users with high accuracy and authentication services. Both the commission and GSA have adopted the Galileo Commercial Service Implementing Decision.
The Commercial Service will complement the Galileo Open Service by providing an additional navigation signal and added-value services in a different frequency band. Unlike the Open Service, the Commercial Service signal can be encrypted in order to control access to Galileo Commercial Services.
“The Commercial Service is unique in that its services are not provided by any other GNSS programme and thus represents a unique opportunity for Galileo to differentiate itself from other systems and offer users an added value to the standard positioning services already available,” says GSA Executive Director Carlo des Dorides.
With the Commercial Service, Galileo users will benefit from:
High Accuracy service based on the transmission of Precise Point Positioning information through its E6-B signal, delivering accuracy below one decimeter worldwide; and
Commercial Authentication service based on the E6 signal code encryption, allowing for increased robustness of professional applications.
Following the Commercial Service Implementing Decision, the user community will also be able to use the Open Service Navigation Message Authentication (OS NMA) for free. The OS NMA is capable of protecting users from spoofing attacks by digitally signing the Open Service message in the E1 band.
The High Accuracy and Commercial Authentication services will most likely be provided for a fee, and at least one signal component of the Galileo E6 signals will remain freely available, allowing user communities to benefit from signals in all Galileo bands.
To avoid disrupting existing professional markets, the Commercial Service will be most likely be operated by at least one yet-to-be-determined commercial service provider. All three services are compatible with the current signal definition and are based on existing infrastructure.
After a test period, the Galileo Commercial Service will become available when Galileo reaches Full Operational Capability, which is expected by 2020. It will complement the Galileo Open Service, Public Regulated Service and Search and Rescue service — all available now via the Galileo Initial Services.
Additional satellites will be successively added to the constellation, with the launch of the next four foreseen in 2017.
Researchers from the Department of Electrical Engineering at KU Leuven (University of Leuven, Belgium) have designed authentication features that will make it more difficult to send out false Galileo signals.
Professor Vincent Rijmen and doctoral student Tomer Ashur from the Department of Electrical Engineering (ESAT) at KU Leuven have advised the European Commission on ways to make Galileo signals more difficult to falsify. Their authentication method involves electronic signatures, similar to methods used for online banking.
Navigation systems are based on satellites that send out signals, including their location. The distance to four or more satellites makes it possible to determine someone’s geographical position and time. But this process may go wrong when hackers send out signals of their own that drown out the real ones. As the authentic signals are blocked, the position information for the navigation system is no longer correct.
To avoid delaying the launch of Galileo, the researchers could only use the remaining “bits” in the signals for authentication purposes.
“This is why we support the TESLA method for electronic signatures,” Rijmen says.
“TESLA (Timed Efficient Stream Loss-Tolerant Authentication) signatures fit into 100 bits,” he adds. “They quickly expire, but this is not a disadvantage in the case of satellite navigation because the location is authenticated every 30 seconds or less anyway.”
The method still needs to be tested and validated before it can be made available to the general public.
“The authentication service is scheduled to become publicly available on a number of Galileo satellites in 2018,” Rijmen says. “By 2020, the method will be fully operational. To use it, however, you will need a special receiver for Galileo signals that can also verify the electronic signatures. These receivers are currently in development.”
The European Union activated its Galileo satellite navigation system in December 2016.
Senior Airman Mathew Snyder, 3d Airlift Squadron loadmaster, loads ramp shoring onto a C-17 Globemaster III. The cargo load required 7,000 pounds of shoring. (Photo: USAF)
Thanks in part to a Team Dover aircrew, the next generation of Air Force GPS satellites will soon be launched into orbit.
A C-17 Globemaster III, operated by the 3d Airlift Squadron, transported a GPS Block IIIA Satellite Pathfinder and its shipping container from the Space Coast Regional Airport in Titusville, Florida, to Buckley Air Force Base, Colorado, Jan. 29-31.
According to Eric Smith, Lockheed Martin Space Systems associate manager of transportation, the Pathfinder was sent to Florida in December to validate the required transportation procedures needed to get a satellite to the launch facility. He explained that the Pathfinder is not a true mocked-up satellite, but a model that is being used to test and certify transportation methods for future satellites.
Personnel load a shipping container, with a GPS Block IIIA Satellite Pathfinder inside, onto a C-17 Globemaster III, operated by the 3d Airlift Squadron. (Photo: USAF)
“It’s as close to a fully built satellite as we could get,” Smith says. “The shipping container is essentially a mobile cleanroom.”
Prior to the mission, the aircrew expected the move would to be challenging. This was the first time an active duty C-17 squadron loaded and moved this type of cargo.
“We prepositioned two loadmasters down to Titusville, at Cape Canaveral, because it was a complicated load,” says Capt. Shawn McDonald, 3d AS pilot and chief of tactics. “They went to figure out some of the logistics about two days in advance.”
Prepositioning loadmasters is not commonplace for the 3d AS.
“We only do it if it’s for something that’s going to be extremely complicated or extremely expensive,” says Senior Airman Mathew Snyder, 3d AS loadmaster. “We were told that the piece itself was worth half-a-billion dollars.”
This was first time an active duty C-17 squadron loaded and moved this type of cargo. (Photo: USAF)
The entire Pathfinder and container payload weighs more than 67,000 pounds, is 42 feet long, 16 feet wide and 11 feet high.
“It was a challenge,” Snyder says. “Just the sheer size of the container took up most of our cargo compartment, came in at over 500 inches long, over 140 inches high, and it really only left us with a foot left or right of the aircraft. There was no kind of wiggle room for mistakes. So we really had to be spot on, working together and make sure everything went smoothly.”
Between the loading team and loadmasters, it took 24 people to successfully load over a five-hour period. It took an additional six hours to offload the cargo in Colorado.
Between the loading team and loadmasters, it took 24 people to successfully load the container. (Photo: USAF)
“I would say [onloading cargo] was most challenging,” Snyder says. “Because for the other two loadmasters, it was the first time we were setting eyes on the piece of cargo. The offload was essentially doing everything in reverse, and by then, we had already done it once.”
The load itself was not the only challenging part of the mission, according to McDonald, who was the aircraft commander.
“Getting to Titusville, it’s a small field, somewhere where we are not usually going,” he says. “Talking about the cargo, though, there were some specifications on how we had to park the plane, nose high attitude to get this thing on and off.”
Personnel offload a shipping container with a GPS Block IIIA Satellite Pathfinder inside. (Photo: USAF)
The GPS III is the next generation of Navstar GPS satellites built by Lockheed Martin Space Systems and operated by the Air Force. There are currently 10 GPS Block III satellites on order, with the first scheduled for launch in the spring of 2018.
The 3d AS aircrew was made up of pilots Capt. Shawn McDonald, Capt. Ricardo Morales, and 1st Lt. Benjamin Bertelson, and loadmasters Master Sgt. David Feaster, Master Sgt. Jason Massey, Staff Sgt. Ryan Thompson, and Senior Airman Mathew Snyder. Also part of the crew were two flying crew chiefs from the 736th Aircraft Maintenance Squadron, Staff Sgt. Daniel Scheuerman and Staff Sgt. Lance Wright.
Geoscience Australia, an agency of the Commonwealth of Australia, and Lockheed Martin have entered into a collaborative research project to show how augmenting signals from multiple GNSS constellations can enhance positioning, navigation and timing for a range of applications.
The research project aims to demonstrate how a second-generation Satellite-Based Augmentation System (SBAS) testbed can — for the first time — use signals from both GPS and the Galileo constellation, as well as dual frequencies, to achieve greater GNSS integrity and accuracy.
Over two years, the testbed will validate applications in nine industry sectors: agriculture, aviation, construction, maritime, mining, rail, road, spatial and utilities.
To improve precision navigation, a second-generation SBAS will use signals from both GPS and Galileo, and dual frequencies, to achieve even greater GNSS integrity and accuracy. (Graphic: Lockheed Martin)
“Many industries rely on GNSS signals for accurate, safe navigation. Users must be confident in the position solutions calculated by GNSS receivers. The term ‘integrity’ defines the confidence in the position solutions provided by GNSS,” says Vince Di Pietro, chief executive of Lockheed Martin Australia and New Zealand. “Industries where safety-of-life navigation is crucial want assured GNSS integrity.”
Ultimately, the second-generation SBAS testbed will broaden understanding of how this technology can benefit safety, productivity, efficiency and innovation in Australia’s industrial and research sectors, according to Lockheed.
“We are excited to have an opportunity to work with Geoscience Australia and Australian industry to demonstrate the best possible GNSS performance and proud that Australia will be leading the way to enhance space-based navigation and industry safety,” Di Pietro adds.
Basic GNSS signals are accurate enough for many civil positioning, navigation and timing users. However, these signals require augmentation to meet higher safety-of-life navigation requirements. The second-generation SBAS will mitigate that issue.
Once the SBAS testbed is operational, basic GNSS signals will be monitored by widely-distributed reference stations operated by Geoscience Australia. An SBAS testbed master station, installed by teammate GMV of Spain, will collect that reference station data, compute corrections and integrity bounds for each GNSS satellite signal, and generate augmentation messages.
“A Lockheed Martin uplink antenna at Uralla, New South Wales, will send these augmentation messages to an SBAS payload hosted aboard a geostationary Earth orbit satellite, owned by Inmarsat,” says Rod Drury, director of international strategy and business development for Lockheed Martin Space Systems Co. “This satellite rebroadcasts the augmentation messages containing corrections and integrity data to the end users. The whole process takes less than six seconds.”
By augmenting signals from multiple GNSS constellations — both Galileo and GPS — second-generation SBAS is not dependent on one GNSS. It will also use signals on two frequencies — the L1 and L5 GPS signals, and their companion E1 and E5a Galileo signals — to provide integrity data and enhanced accuracy for industries that need it.
Research partners
Lockheed Martin will provide systems integration expertise in addition to the Uralla radio frequency uplink. GMV-Spain will provide its magicGNSS processors. Inmarsat will provide the navigation payload hosted on the 4F1 geostationary satellite. The Australia and New Zealand Cooperative Research Centre for Spatial Information will coordinate the demonstrator projects that test the SBAS infrastructure.
Lockheed Martin has significant experience with space-based navigation systems. The company developed and produced 20 GPS IIR and IIR-M satellites. It also maintains the GPS Architecture Evolution Plan ground control system, which operates the entire 31-satellite constellation.
The GPSdome anti-jammer was developed for civilian applications. It aims to curb situations in which civilian vehicles are stuck “off the grid.” It combats electromagnetic warfare by using null steering, a method of spatial signal processing through which a transmitter can nullify communication jamming. In particular, the product was developed to address the requirements of autonomous cars, drones and unmanned aerial vehicles, all of which depend heavily on GPS to function. Several carmakers have expressed interest in integrating the anti-jammer in their autonomous cars, including Daimler-Mercedes, Ford, Toyota, Hondand BMW and others.
The Aaronia GPS Logger is a six-parameter datalogger designed for recording the position and orientation of RF antennas (such as the Aaronia HyperLOG X, HyperLOG EMI and Magnotracker series) during field investigations. It also is useful for a wide range of non-RF applications where position and movement logging is required. It has sensors in a very small form factor, with a fast data-capture rate of up to 35 logs/second. The logger with built-in battery is 4 x 1.7 x 0.9 inches and weighs 3 oz. The logger starts up in about 30 seconds and features a 66-channel GPS sensor with built-in antenna, offering a position accuracy of six feet, maximum velocity measurements of up to 350 mph and altitude up to 60,000 feet, with a signal sensitivity of –165 dBm. The logger can be used to create an RF heat map including frequency, direction and strength of an RF source with a 360-degree view. All sensor data can be captured at up to 35 readings per second on to a microSD card or via USB streaming. The real-time indication of data makes the Aaronia GPS logger useful for instantly assessing position-variable information.
For consumer GPS processing and smartphone indoor positioning
Photo: Focal Point Positioning
S-GPS is a smartphone-based sensor fusion, machine learning and signal processing suite designed to provide satellite positioning capabilities in urban environments and indoors. With its multipath-mitigation process, S-GPS improves the performance of existing radio-based positioning systems. The fully software-defined solution is aimed at system-on-chip silicon architecture and smartphone receiver front ends. A software upgrade for existing receivers, it requires no extra hardware, dongles or infrastructure to operate. The computational load of S-GPS is comparable to that of existing GNSS processing. The higher sensitivity of S-GPS allows signal tracking to be maintained in traditionally difficult environments, such as deep indoors, where standard devices would fail. This reduces the time spent in acquisition mode in urban areas, leading to significant improvements in battery life in like-for-like tests with standard A-GPS technologies.
The u-blox LARA-R3121 is a single-mode LTE Category 1 modem and a GNSS positioning engine. It is designed for Internet of Thigns (IoT) applications including smart utility metering, connected health and patient monitoring, smart buildings, security and video surveillance, smart payment and point-of-sale systems, as well as wearable devices, such as action cameras. It comes in a land grid array (LGA) package for easy manufacturing, and offers easy migration from u‑blox LTE, UMTS, CDMA and GSM/GPRS modules.
NTS units can detect difference between real and spoofed signals
Photo: OnTime Networks
OnTime Networks has added advanced anti-spoofing technology to its Blueberry and Cloudberry CM-1600 network time server (NTS) product lines. OnTime Networks’ proprietary anti-spoofing algorithms and technology provide not only an alert that GPS is been spoofed, but also the protection that the GPS timing signal is moved over to a highly stable free-running clock, as long as the detected GPS spoofing attack is in progress. Power grids are particularly vulnerable to spoofing, and are increasingly implementing GPS technology to more accurately meter allocations of electricity across the grid. Being even 10 microseconds off could cause power generators to shut down or get damaged.
The GNSS tracking engine of the K708 OEM board with 496 channels is capable of tracking all working and future constellations. Compared with the K5 series OEM boards, the K708 uses an application-specific integrated circuit (ASIC) chip that improves data quality and reduces power consumption. It is designed with strong compatibility and built-in functions, including high-accuracy position, velocity and time (PVT) output, long baseline RTK and reserved webserver service. The K708 is designed for CORS, deformation monitoring systems and related high-accuracy GNSS positioning applications. Signals received include GPS L1 C/A, L2C, L2P, L5; BeiDou B1/B2/B3; GLONASS L1C/A, L1P, L2C/A, L2P; Galileo; and QZSS.
Monitor, manage and evaluate monitoring data, optionally trigger alarms
Photo: Topcon Positioning
The Delta Solutions deformation monitoring system uses several software and hardware components — Delta Link, Delta Log, Delta Watch, Delta Sat and the Topcon MS AXII total station — to provide accurate and reliable monitoring measurements and associated reporting for asset protection. Delta Watch delivers accurate and reliable data in a variety of reporting formats to fit a project’s needs. Data from the total station, GNSS receivers, leveling devices and sensors can be processed and analyzed individually or as a network-adjusted solution. Delta Watch’s optional Delta Sat GNSS processing module allows for stand-alone GNSS monitoring or combined GNSS and total-station network adjustments. Delta Link provides hardware support communication for autonomous operation in the field, managing each power source to maximize system availability, while Delta Log provides an intuitive interface to manage observations, target types and measurement scheduling.
GPS data collector for utilities, mining, forestry, agriculture
Photo: Geneq
The SXPad 1000P is an affordable, rugged handheld GPS data collector specifically designed for mobile GIS users in applications such as water, electric and gas utilities, transportation, mining, agriculture and forestry. The high-performance 1000-MHz device is designed to give professionals the power needed to work with maps and large data sets in the field. It has an IP67 waterproof seal and can survive 5-foot (1.5-meter) drops to concrete. Its 3.7-inch color touchscreen (full VGA) is sharp and is sunlight readable. Standard features include a battery life of more than 10 hours on a charge, 8-GB internal storage, and slots for MicroSD cards and SIM cards as well as Windows Mobile 6.5. The SXPad 1000P also offers a 3.5G cellular modem, Wi-Fi, Bluetooth, video capture and a 5-megapixel camera. It is optimized for GPS/GIS field data collection using its 1-to-3-meter accuracy internal GPS receiver or one of Geneq’s high-performance SXBlue GPS receivers for sub-meter and centimeter-level accuracy.
Glean and share insight from big data, internet of things
Esri ArcGIS 10.5 offers next-generation analytics technology by helping organizations glean insight from enterprise data, big data and the Internet of Things (IoT) and share that insight in intuitive ways. It includes improved capabilities for handling large-scale analytics and big data; a drag-and-drop interface that streamlines the creation of spatial analysis through maps, charts and graphs; and collaboration features to connect and analyze information across the enterprise. The new release is powered by Esri ArcGIS Enterprise, a significant evolution of the technology formerly known as ArcGIS for Server. ArcGIS Enterprise has been updated with improved power to process and analyze large, disparate datasets.
Entry-level device for construction, public safety
Photo: Faro
The Faro FocusM 70 is an entry-level laser scanner for construction building information modeling (BIM) and public safety forensics. Features include an IP54 rating for use in high particulate and wet weather, high-dynamic-range imaging, an acquisition speed of almost 500,000 points per second and extended temperature range. Data captured can be used with various third-party software packages. The Faro FocusM 70 is specifically designed for both indoor and outdoor applications that require scanning up to 70 meters and at an accuracy of +/– 3 millimeters.
PingNav ADS-B OUT GNSS navigation unit. Photo: uAvionics
PingNAV is a small, light ADS-B OUT compliant navigation source. ADS-B (Automatic Dependent Surveillance – Broadcast) helps aircraft operators sense and avoid possible collisions. ADS-B is mandated by the FAA for all aircraft in the U.S. National Airspace by 2020. PingNAV supports GPS, GLONASS, Galileo and QZSS, and has a battery backup for quicker position initialization. Dual static ports forpressure altimeter readings and integrated security and integrity technologies include receiver autonomous integrity monitoring (RAIM) and satellite-based augmentation system (SBAS) to detect and correct errors improving accuracy, reliability and availability.
The Ping200S is a small, light, FCC-approved full range mode C and mode SAutomatic Dependent Surveillance-Broadcast (ADS-B) transponder. At 50 grams, power consumption is low enough to be powered by battery pack for 2 hours, yet is powerful enough to provide visibility to other aircraft and UAVs up to 200 miles away, at which point it implements sense and avoid for drone operations in the national airspace. The ping200S is designed to meet the requirements of TSO-C199 as a Class A Traffic Awareness Beacon System.
Defense-proven to disrupt and neutralize hostile UAVS
Photo: Liteye Systems, Tribalco
The AUDS counter-UAS defense systemhas been field proven to detect, track and defeat malicious and errant unmanned aircraft systems (UAS) or drones. The fully integrated system has achieved TRL-9 status following the successful mission deployment of the AUDS system with the U.S. military. TRL-9 is the highest technology readiness level that a technology system can attain. The AUDS system — developed by Blighter Surveillance Systems, Chess Dynamics and Enterprise Control Systems — can detect a drone six miles (10 kilometers) away using electronic scanning radar. It tracks the UAV using precision infrared and daylight cameras and advanced video tracking software before disrupting the flight using a non-kinetic inhibitor to block the radio signals that control it. The detect, track and defeat process typically takes 8–15 seconds. Using AUDS, the operator can effectively take control of a drone and force a safe landing. The AUDS system works in all weather, day or night, and the disruption is flexible, proportional and operator controlled.
For UAV manufacturers to add flight time, extend battery life
Photo: Texas Instruments Sample build.
Two circuit-based subsystem reference designs can help manufacturers add flight time and extend battery life to quadcopters and other non-military consumer and industrial drones used to deliver packages, provide surveillance or communicate and assist at long distances. The 2S1P Battery Management System (BMS) reference design transforms a drone’s battery pack into a smart diagnostic black box recorder that accurately monitors remaining capacity and protects the Li-Ion battery throughout its entire lifetime. Designers can use the drone BMS reference design to add gauging, protection, balancing and charging capabilities to any existing drone design and improve flight time. A second reference design helps manufacturers create drones with longer flight times and smoother performance. It helps electronic speed controllers achieve the highest possible efficiency with performance for speeds more than 12,000 rpm (> 1.2 kHz electrical) including fast-speed reversal capability for more stable roll movement.
The CMA-5024 GPS landing system sensor meets the requirements for an instrument-flight-rules civil-certified GNSS. The European Geostationary Navigation Overlay Service (EGNOS) augments GPS to provide an extremely accurate navigation solution that will support all flight operations from en route through localizer performance with vertical guidance (LPV) CAT-l equivalent approach. The CMA-5024 is compliant with and completely supports EGNOS/SBAS, from departure, en-route navigation and all EGNOS/SBAS LPV precision approaches, and complies with published Communication Navigation Surveillance/Air Traffic Management (CNS/ATM) navigational mandates.
A new variant of Qualcomm’s connected car reference platform uses its gigabit-class Snapdragon X16 LTE modem to help car manufacturers deliver high-speed, high-quality and reliable connectivity for advanced telematics and connected vehicle services. It supports peak download speeds up to 1 Gbps. The reference platform allows carmakers to integrate additional wireless and networking technologies, including Wi-Fi, Bluetooth, Bluetooth Low Energy and GNSS, with optional support for dedicated short-range communication (DSRC) and cellular-V2X. The platform includes a module reference design for the Snapdragon X16 LTE modem to help automotive suppliers accelerate development. The reference platform integrates quad-constellation GNSS and 3D dead-reckoning location solutions, and is designed to manage concurrent operation of multiple wireless technologies using the same spectrum frequencies.
CAD model of the antenna system: The antennas will be arranged so that the center of mass is at the center of the tube. Each antenna will be counterbalanced. (NASA)
Researchers at NASA’s Armstrong Flight Research Center have designed an antenna-mounting platform to provide users satellite-based tracking functions for unmanned aerial vehicles. The platform integrates multiple capabilities onto one low-cost platform.
In August 2016, NASA signed a license agreement with Mobile Antenna Platform Systems Inc. to commercialize the portable antenna platform.
The platform is built to rotate 60 pounds of antennas, transmitters and receivers and eliminate the need for additional load-balancing hardware. A smaller version can be flown on a plane, greatly extending the telemetry link range without requiring more power from the aircraft.
Auto tracking software uses the target’s GPS location to coordinate and maintain a line-of-sight link as great as what the telemetry system can support.
NASA researchers originally developed the technology for use with research UAVs, which often involve multiple transmitters and receivers on the aircraft and on the ground, with multiple antennas that must be pointed at a single UAV.
The platform is a middle ground between the low-end tracking platforms that support only one antenna and expensive, high-end options designed for military use.
Besides research, the platform could be used in marine communications, satellite tracking in multiple frequencies and weather balloon tracking, NASA said.
Powered by 120 VAC, the platform moves all of the antennas simultaneously in continuous rotation in azimuth and vertical ±180°, effectively tracking a line-of-sight object up to 20 miles away or further, limited by transmit power and antenna configuration.
It is designed for use with any moving system needing to transmit large quantities of data over one or more RF links. RF signals can include video, command and control, and signals to and from the UAV as well as the research data of interest.
The platform design includes:
a horizontal bar with antenna mounts
a platform head containing the motors and gears
an antenna stand containing electrical slip rings and cables to connect to the radios, motors and external computer
a microcontroller interface to drive the motors and receive antenna commands from the software
Its user interface runs on Microsoft Windows and enables the tracking antenna to be interfaced to any ground station that can provide the GPS coordinates of the target being tracked in real time and the GPS coordinates of the tracking antenna.
Platform benefits
According to NASA, the antenna platform offers these benefits:
Portability. Lightweight components and a small profile allow the platform to be carried by a single person.
Simplicity. Its unique design eliminates the need for additional load-balancing hardware, simplifying setup.
Versatility. Up to 58 pounds (26 kg) of multiple antennas from various manufacturers in any combination (including Yagi-Uda, dish/parabolic, omnidirectional, patch/microstrip) under 10 W can be accommodated
Low Power Use: Using a smaller motor that is faster than those on other platforms requires less power to achieve continuous rotation.
Low Cost: The overall system is estimated to cost less than $5,000.
RAK equipment records video and tracks GPS coordinates of distressed roads. Photo: RAK
Red Hen Systems Inc. is offering a way to accurately categorize road conditions and linear miles.
The Road Assessment Kit (RAK) can be installed and operated for assessing roads, bridges, curbs, sidewalks, signs and more.
The all-in-one system uses real-time video geotagging with Red Hen’s patented video mapping system, the VMS-333. The VMS-333 connects to a GPS receiver and camera or video recorder to automatically geotag photos, videos and audio notes with GPS coordinates.
The data can then be analyzed in Google Earth with isWhere, Red Hen’s geospatial media mapping software, which provides a track log of the route traversed. Data can also be mapped in Esri ArcMap.
A screenshot of isWhere. Photo: RAK
The survey hardware can be moved from one vehicle to another in 30 minutes or less and is suitable for routine vehicle operation in between annual road surveys.
Using GoPro cameras, the kit can capture up to four views with GPS data points in a single data collect.
The Belgian dredging, environmental and engineering group DEME relies on the accuracy and reliability of the AsteRx family of precise GNSS positioning solutions from Septentrio.
DEME is using Septentrio’s AsteRx GNSS receivers to obtain centimeter-level accuracy for all its dredging and marine construction operations worldwide. These receivers are specifically designed to operate in difficult conditions, from dredging a few meters from the coastline to constructing wind turbines kilometers out at sea.
AsteRx-U dual-antenna receiver.
DEME began using Septentrio’s solutions more than 10 years ago. While dredging in the Belgian town of Oostende, DEME was unable to obtain a reliable RTK position from their GNSS equipment because of interfering radio signals from a local radio tower.
Septentrio worked with DEME to identify the source of the interference and modified a standard RTK receiver with special firmware to address the jamming problem. This case, along with others faced by Septentrio’s customers in the field, encouraged the development of a dedicated interference mitigation technology called AIM+, which is now standard in Septentrio’s GNSS solutions.
Septentrio’s AsteRx GNSS receivers have been deployed on DEME’s ships around the world. They have been vital to DEME for the success of projects such as the creation of Gateway Port in London, U.K.; the construction of Deurganckdok in Antwerp, Belgium; the Pearl Qatar City; the Thornton Bank Offshore Windfarm in Belgium; the extension of the Suez Canal in Egypt; and many more.
“’Creating land for the future’ is the slogan here at DEME and this is thanks, in part, to the accuracy and robustness of the solutions offered by Septentrio,” says Lorentz Lievens, head of the survey department.
“Jamming is a concern which DEME has seen more and more all over the world,” Lievens says. “Septentrio’s receivers are unique in that they continue to provide an accurate solution even in areas of high radio and ionospheric interference allowing DEME to deliver projects on time and on budget. Septentrio’s precise positioning solutions will remain vital for DEME to deliver quality and cost-effective operations around the world for many years to come.”
A diversely polarized antenna array combines signal processing in the spatial and polarization domains for significant improvement in receiver robustness against interference.The C/N0 of line-of-sight components is improved since the receiver can use the power present in the left-hand circularly polarized channels, and also interference mitigation improves.
By Matteo Sgammini, Stefano Caizzone, Achim Hornbostel and Michael Meurer
INNOVATION INSIGHTS with Richard Langley
POLARIZATION. We use the word in everyday speech to mean a division into two groups with sharply contrasting opinions or beliefs.
But the word has another use in physics and electrical engineering to describe a characteristic of electromagnetic waves. Electromagnetic waves, whether they be light waves or radio waves, have electric and magnetic fields vibrating perpendicularly to each other and to the direction of propagation. If the electric field (and, correspondingly, the magnetic field) vibrates in a specific non-changing plane, we say that the wave is linearly polarized.
In terrestrial radio communications, signals are typically transmitted as linearly polarized waves with the electrical field oscillating in the vertical plane or the horizontal plane. Receiving antennas are designed and oriented to preferentially respond to the particular polarization of the signals. Before the widespread use of cable and satellite distribution platforms, VHF and UHF TV signals were received using rooftop antennas consisting of multiple parallel metal rods (similar antennas are used now for terrestrial digital TV).
In North America, the rods were in the horizontal plane since the transmitted signals were horizontally polarized. In Europe, on the other hand, the rods were sometimes in the vertical direction since there, some TV signals were transmitted with vertical polarization.
If the plane of vibration of the electric and magnetic fields rotates uniformly as the signal propagates, we have the case of circular polarization. Since the sense of rotation can be clockwise or anti-clockwise, we have right-hand circularly polarized (RHCP) and left-hand circularly polarized (LHCP) signals following the direction of curl of the fingers of the right and left hands. Circular polarization is typically used for signals from satellites in low and medium Earth orbit, such as GNSS satellites, where the relative orientation of the transmitting and receiving antennas is not fixed. For maximum signal reception, the polarization of the receiving antenna should match the polarization of the signal. All GNSS satellites transmit RHCP signals and therefore most GNSS receiving antennas are designed for such signals.
However, a funny thing can happen to a satellite signal on the way to a receiving antenna. If the signal bounces off a nearby structure or the ground or the sea surface, its polarization is modified and it will become LHCP or a combination of the two polarizations. While this multipath phenomenon can be a pest, as discussed in last month’s column, it can be used to advantage in measuring sea-surface roughness, for example, by monitoring reflected GNSS signals from a low Earth orbiting satellite or an aircraft using a LHCP antenna.
But GNSS receiving antennas are not perfect—especially for direct line-of-sight low-elevation-angle signals. A primarily LHCP antenna can capture a significant portion of the energy in such a RHCP signal and could provide a strong response to a reflected signal when the line-of-sight signal is missing or very weak. So, there could be a benefit in having a dual-polarized antenna to improve positioning capability in marginal situations. Furthermore, jamming signals can be of arbitrary polarization and a dual-polarized antenna array with beamforming capability could better separate and mitigate such interference. In this month’s column, we examine the principles of operation of such an antenna array and how one performed in real-world jamming and non-jamming scenarios.
The rapid growth of the wireless telecommunication sector and, consequently, the high demand of spectrum assigned to the new services make the frequency spectrum very crowded and quite saturated. With the weak received signal power of GNSS signals, spurious harmonics from other systems can cause unintentional interference and, therefore, a serious problem to the reliable estimation of user position, velocity and time (PVT). Besides unintentional interference, more virulent intentionally radiated signals, called jammers, may knock out the GNSS receiver; this is especially the case when a jammer with high time-frequency dynamics (such as a chirp-like jammer) affects the GNSS signal spectrum.
Whether unintentional or intentional, interference represents a serious threat to GNSS in applications ranging from safety-of-life to critical sectors like law enforcement, transportation, communication and finance. In such critical applications, it is important that the GNSS receiver provides a minimum level of reliability and robustness, even at the cost of increased price and complexity.
To meet this need, some manufacturers and research institutions have been developing GNSS receivers equipped with anti-jamming capabilities.
In this article, we propose a novel approach to interference mitigation. We equipped a GNSS receiver with a diversely polarized antenna array to combine signal processing in the spatial and polarization domains in a novel way. By doing this, we demonstrated achievable improvement in interference mitigation. For this purpose, we extended an existing two-step blind adaptive beamforming algorithm to a new algorithm that includes the polarization domain. We evaluated the new algorithm through measurement data gathered during a campaign carried out at the Automotive Testing Center in Aldenhoven, near Jülich, Germany. We used different interference sources, including low-cost jammers, euphemistically called personal privacy devices (PPDs), in real-life situations such as in a moving car approaching a GNSS receiver.
The receiving antenna used in our work is a four-element rectangular dual-polarized (DP) array in a two-by-two configuration. Each element has two feeds available, one ideally receiving the right-hand circularly polarized (RHCP) field and the other the left-hand circularly polarized (LHCP) field of the polarized incoming signals. Due to antenna imperfections and coupling effects, part of the LHCP field impinging on the antenna will be received by the RHCP port and vice versa. Generally, the antenna axial ratio is fine-tuned at boresight so that the energy of a RHCP satellite signal impinging on the array at high-elevation angles will be mostly captured by the RHCP port, while the energy flowing through the LHCP channel can be ignored. This statement does not hold for satellite signals coming from lower elevation angles or in general for signals with polarization other than RHCP, this being generally the case for multipath and interference. In particular, the response of a planar antenna array for angles-of-arrival (AoAs) close to the horizon is almost linearly polarized. It follows that a significant portion of the RHCP energy in a signal is likely to be captured by the LHCP channels and can be used either to strengthen the line-of-sight (LOS) component, or to better separate and mitigate both multipath and interfering (jamming) signals.
Adding the polarization domain makes it possible to better discriminate spatially and temporally correlated signals. In some environments, such as urban canyons, the LOS signal might not be available or might be strongly attenuated. In this case, the reflected non-LOS signals can be used to perform positioning and would benefit from a DP antenna approach. As a matter of fact, the reflected signals will be no longer RHCP, thus the LHCP channel can be used to strengthen the echoes and improve positioning. Diversely polarized antenna arrays also have the advantage of increasing the total number of available degrees of freedom. The number of degrees of freedom of an antenna array corresponds to the number of nulls that can be placed in the direction of arrival of interfering signals. For a single-polarization (SP) array with M elements, M-1 nulls can be placed in the spatial domain. In the case of a DP array, 2M-2 nulls can be placed in the space and/or polarization domains. This is a key factor in counteracting high-power and highly-dynamic jammers, such as PPDs. Furthermore, the use of a diversely polarized array improves signal detection, as well as direction of arrival and polarization-estimation performance. This is particularly true for closely spaced signals with sufficiently separated polarizations. On the other hand, the introduction of the second polarization increases the computational complexity of signal processing, since the number of elements is doubled.
The results of our measurement campaign show a significant improvement in receiver robustness against interference when the DP approach is used compared to the general SP case.
SIGNAL MODEL
In this section, we will briefly describe the theory of signal and antenna polarization with a minimal number of equations. A more complete discussion is included in the paper on which this article is based (see Further Reading).
Polarization of a Plane Wave. A received electromagnetic signal is assumed to be narrow band, and the source of radiation is assumed to be located in the far field. The plane wave propagating in free-space has the property that the direction of propagation is orthogonal to the electric and magnetic field vectors. This allows the electric field e of a polarized wave to be completely described in terms of the two unit vectors, and , orthogonal to the direction of propagation
(1)
where ∈xand ∈y are the real-valued, non-negative, amplitudes of the components of the electric field, Φxand Φyare the phase components of the field, ω is the angular frequency of the carrier and k is the wave number.
Only the real part of Equation (1) is physically relevant, with the complex exponential containing information about the phase of the oscillating field.
Switching from the linear to the circular basis vector set:
(2)
where and are the unit vectors of the RHCP and LHCP components, respectively and omitting the explicit time and spatial dependence, we can write the normalized electric field as
(3)
The polarization state of an electromagnetic signal is fully described by ∈R and ∈L.
More generally, the electric field of any plane wave impinging at the antenna can be expressed in the form
(4)
Dual-Polarized Antenna Array. A circular DP antenna features two orthogonal circular polarization output ports, meaning each element ideally receives the voltage induced by the RHCP and LHCP field components separately on the two different antenna ports. Due to antenna imperfections and the coupling effect, part of the received RHCP field is received by the LHCP port and vice versa. These undesired voltages are responsible for the emergence of the cross-polar components.
In view of this, we characterize the antenna in terms of its response to circularly polarized plane waves and express the electric field using the Jones vector notation in the circular basis as
(5)
where is the complex total electric field received by the RHCP port, is the complex electric field induced at the RHCP port by a purely RHCP electromagnetic wave, indicated as a co-polar component, is the complex cross-polar component of the electric field obtained by exciting the antenna with a purely LHCP electromagnetic wave, φ is the azimuth angle and θ is the elevation angle of the impinging signal assuming the antenna to be at the origin of the spherical coordinate system. Similar statements apply for the total electric field received by the LHCP port, and for the co-polar ( ) and cross-polar () components.
If vR and vL are the complex voltages induced at the RHCP and LHCP antenna outputs by the signal in Equation (4), respectively, the antenna outputs are given by
(6)
where ψ = [θ, φ] is the vector parameter carrying the information about the direction of arrival (DoA) of the incident signal and τ is the time delay of the incident signal.
With an M-element array of DP sensors, we can vR and vL to represent the complex array responses of the DP antenna array:
(7)
where and define the steering vector of the DP antenna array given a signal incident at angle ψ and polarization defined by the Jones vector .
Problem Formulation. The analog signals collected by the antenna array are then passed through the receiver front end where they are amplified, filtered and shifted to baseband. The resulting complex baseband signal with bandwidth B that is received by an antenna array with M DP sensor elements at polarization port P is
(8)
where sp(t) defines the superimposed satellite signal replicas with l = 1 identifying the LOS signal and l = 2, …, L the non-LOS (multipath) signals and zp(t) denotes the superimposed radio frequency interference (RFI) signals with i ranging from 1 to I.
Additionally, we assume temporally and spatially uncorrelated complex white Gaussian noise np(t). can be expressed in terms of the steering vectors given the lth signal’s incident angle, the polarization vector and a complex scalar term involving the signal complex amplitude, Doppler frequency, carrier-phase offset and the particular pseudorandom noise sequence and associated
The baseband signals are then digitized at sampling frequency 1/Ts ≥ 2B. The observations are collected at K periods of the pseudorandom sequence at N time instances and the polarizations of the satellite signals and interferers as well as their DoAs are assumed to be constant over each single observation. We finally combine the two outputs of the DP antenna to benefit from both polarizations with a resulting unified signal output X. This increases the number of available degrees of freedom; furthermore, it allows us to carry out filtering in the polarization domain. On the other hand, the overall system complexity is increased; in particular, the computational complexity of the matrix inversion needed for pre-whitening (to be discussed next) is increased by a factor of about 23.
PRE-WHITENING AND EIGEN-BEAMFORMING
Interference mitigation and beamforming uses a two-step blind beamforming approach based on orthogonal projection. It is similar to an approach we developed for the single-polarization case, with the only difference here being the introduction of the orthogonal LHCP channel, which doubles the number of sensors. Doubling the number of sensors does not necessarily mean that the number of degrees of freedom is also doubled. It has been shown that when using diversely polarized antennas, to discriminate signals unambiguously it is required that the maximum number of signals D = L + I satisfies the relationship D ≥ 2M–2.
This means that one additional degree of freedom is required to discriminate in the polarization domain in comparison to the case of an antenna array of uniformly polarized sensors, where it is required that D ≥ M–1.
Pre-Whitening. We establish a sample spatial-polarimetric covariance matrix, where we assume that the satellite signals, the interfering signals and the noise are uncorrelated among each other. Furthermore, we ignore the influence of the signal replicas, because their power is usually much smaller than the power of the noise and interference. We then obtain the approximate pre-whitening matrix to be applied to X. The pre-whitening matrix is applied before signal despreading.
Eigen-Beamforming. In the next stage, the complex pre-whitened signal passes through the tracking loops for despreading and code and carrier wipe-off. We collect the post-correlation signal at K integration intervals to obtain the data matrix and the post-correlation spatial-polarimetric sample covariance matrix. The post-correlation eigen-beamformer is obtained following the same optimization problem that we solved for the single-polarization case. We apply the optimum weight vector, maximizing the ratio between the power of the desired signal and the power of the undesired signals plus noise, using the eigenvector with respect to the dominant non-zero eigenvalues of the post-correlation covariance matrix.
MEASUREMENT CAMPAIGN
The receiving antenna used in our work is a planar four-element rectangular DP array in a two-by-two configuration, similar to one we have used previously, apart from the additional hybrid couplers needed to provide the LHCP channel outputs. Each element has a double feed, one ideally receiving the RHCP field and the other the LHCP field of the polarized incoming signals, resulting in a total of eight output channels. The single antenna elements are designed for the reception of the GPS L1 and L5 and Galileo E1 and E5 bands, but in this work we focus only on the reception of GPS L1 signals.
The eight signals are passed through a front end, where they are amplified, filtered and down-converted to the intermediate frequency of 2.5 MHz. The analog signals are then digitized with a sampling rate of 8 megasamples per second. The resulting 8-bit digital data are collected and stored on a solid-state drive for data analysis in post-processing. Data analysis is then performed by using a GNSS software-based receiver.
Description of Test Scenarios. The DP system has been tested using measurement data to assess its dual capability of improving the quality of LOS signal reception and robustness against both unintentional RFI and jamming. As mentioned previously, the measurement campaign was conducted at the Aldenhoven Automotive Testing Center. The location provides seven tracks of different lengths, inclinations and shapes. The test track used for this measurement campaign was the so-called autobahn, providing two lanes in each direction of travel and a total length of 1,000 meters (see FIGURE 1).
FIGURE 1. Test track layout.
In this article, we report and analyze the results of three different test scenarios. In the first test, we collected GPS L1 data over 60 seconds in an interference-free environment. The aim of this baseline scenario was to verify if the additional LHCP channels improved signal reception in terms of carrier-to-noise-density ratio (C/N0) and PVT errors.
The second test scenario involved a horn antenna mounted on a mast, transmitting a continuous wave (CW) interference signal in the GPS L1 band and steered in the direction of the receiving antenna, as shown in FIGURE 2. Both the horn antenna and the receiving antenna were kept static during the measurement interval.
FIGURE 2. CW interference scenario.
The objective of the third test scenario was to replicate a real-life situation involving jamming, similar to the so-called “Newark scenario,” where a GPS jammer in a truck driving past Newark Liberty International Airport caused ground-based and satellite-based augmentation systems receivers to malfunction. To carry out this test, we installed a type K-320 PPD jammer transmitting in the GPS L1 band (see FIGURE 3) in the 12-volt auxiliary power outlet (cigarette lighter receptacle) of a moving car approaching the receiver and driving by.
FIGURE 3. The K-320 in-car PPD jammer.
The car started its run at a distance of about 260 meters from the receiver. During the first 20 seconds, the car holds its position. After this time, it was driven in the direction of the receiver with a constant speed of 30 kilometers per hour, finishing its route on the other side of the autobahn track, as depicted in Figure 1.
Baseline Scenario. The benefits that come to light using a DP array are of a dual nature. First, the C/N0 of LOS signals is improved since the receiver can make use of the power present on the LHCP channels due to polarization mismatch, in particular for satellites with low AoA, resulting in better receiver-computed PVT solutions. This effect appears evident if we analyze the behavior of C/N0 values over time collected during the non-interference experimental test in the GPS L1 band.
With reference to the sky plot in FIGURE 4 indicating the positions of the satellites at the time of observation, we analyzed the subgroup composed of those satellites having an elevation AoA lower than 30°. There was a sensible improvement of C/N0 using both polarizations from the DP antenna compared to just using the RHCP output (see FIGURE 5(a)). On the contrary, satellites with an elevation AoA higher than 60° do not benefit from the DP antenna and experienced almost the same C/N0 whether the LHCP channel was used or not, as can be seen in FIGURE 5(b).
FIGURE 4. Receiver sky plot for GPS L1 on October 22, 2015, at 13:10:00 UTC.FIGURE 5. C/N0 improvement using the dual-polarized antenna: (a) low-elevation-angle satellites (elevation angle <30°), (b) high-elevation-angle satellites (elevation angle >60°).
While the advantage of using the DP array is evident when observing the C/N0 behavior, this achievement does not translate with the same clear evidence when assessing the 2-D horizontal position error. Nevertheless, an improvement of about 6 centimeters in terms of the standard deviation of the 2-D position solution error in the horizontal plane has been obtained using the DP antenna (see TABLE 1). It is reasonable to expect that in a scenario where the availability of satellites is not as high as in our test case, the use of low-elevation angle satellites becomes more important for the accuracy of the PVT solution. In this case, the use of a DP antenna could play a key role in improving positioning accuracy.
Table 1. Interference-free RMS positioning error, in meters, in the horizontal plane over 60 seconds. Note that the data for the single-element result was obtained using just one sensor element of the 2 × 2 array in the same test run from which the array DP and array SP results were obtained.
CW Interference Scenario. The use of a DP array provides the ability to filter signals in the polarization domain, and at the same time we benefit from the additional degrees of freedom available. Thus, interference mitigation becomes more effective than using a SP array, increasing the receiver robustness and enabling tracking and successful PVT solutions in a severe interference scenario. This outcome appears evident analyzing the results of our test, where the linearly polarized CW interference described in TABLE 2 impinged on the array.
Table 2. Direction and calculated interference-to-signal ratio (ISR) for 25 dBm transmit power CW interference signal.
We show the 2-D horizontal position errors from this test in FIGURE 6. The figure highlights the improvement in position accuracy when both RHCP and LHCP channels are jointly used, limiting the root mean square (RMS) error to 2.65 meters, while it increases to 3.88 meters when only the RHCP channels have been used.
FIGURE 6. Horizontal position errors over 60 seconds in the presence of CW interference.
The advantages of using the DP array as assessed above are well summarized in FIGURE 7. The figure shows the history of the C/N0 split into two clusters. The upper cluster is from measurements during the interference-free period while the lower cluster is from measurements during the period the receiver is affected by the interference. In the figure, the improvement in terms of C/N0 is notable when using the DP array, in particular for low-elevation angle satellites, and for those satellites having a DoA close to the DoA of the interference. The latter case, when satellite signals and the interfering signal almost overlap in space, has been fully analyzed in a technical note (see Further Reading).
FIGURE 7. C/N0 history for all tracked GPS L1 satellites placed in order of their elevation AoA collected over 120 seconds: (a) using the single-polarized antenna, (b) using the dual-polarized antenna.
PPD Jammer Scenario. The goal of this test was to compare the overall performance of the DP array to the SP array, as well as to the case when only a single-element antenna was used and with no pre-whitening applied. The K-320 PPD employed in this test scenario poses a serious threat to any commercial receiver in obtaining a valid PVT solution. The spectrogram of the K-320 is shown in FIGURE 8(a), which illustrates that the chirp signal sweeps very rapidly (with a sweep interval of about 40 microseconds) across a frequency range of 15 MHz centered at the L1 carrier frequency, as can be seen in the plot of power spectral density in FIGURE 8(b). The frequency range is much larger than the receiver bandwidth of about 8 MHz (dual-sided). This means that the RFI is seen as pulsed RFI by the receiver.
FIGURE 8. Chirp-like signal generated by the K-320 PPD jammer: (a) spectrogram, (b) spectral density.
An estimate of the jamming behavior during the test in terms of interference-to-signal ratio (ISR) is shown in FIGURE 9. The estimated ISR counts only for the portion of jamming power falling within the receiver bandwidth in baseband after down conversion; it is not an estimate of the ISR at the antenna array. The closer the jammer in the passing car is to the receiver, the higher the PPD power affecting it. The minimum distance between the jammer and the receiver is about 14 meters and is reached at 13:13:45 UTC as indicated in the figure.
FIGURE 9. Estimated interference-to-signal ratio (ISR) of the K-320 PPD jammer.
In FIGURE 10, we can observe the impact of the RFI when the car drives past the receiver by means of the number of tracked satellites, or rather by the number of valid pseudoranges available for PVT computation. When the jammer is close to the receiver, the DP antenna is always better than the SP one. When the RFI is at the minimum distance (about 14 meters) from the receiver, the SP antenna is no longer able to deliver a valid position, while the DP antenna still can.
FIGURE 10. Number of available pseudoranges.
The higher number of valid pseudoranges when using the DP antenna is translated into a better position accuracy. This result can be seen in TABLE 3, which lists the RMS horizontal position error computed during the time the estimated ISR is greater than 25 dB. In the computations, only valid PVT solutions and 2-D positioning errors below 20 meters have been considered.
Table 3. RMS positioning error, in meters, in the horizontal plane computed when ISR > 25 dB.
CONCLUSION
The results of the measurement campaign have shown a significant improvement in positioning accuracy and robustness against interference when the dual-polarization approach is used compared to the general single-polarization case. Position accuracy takes advantage of the better C/N0 for those satellites with an AoA below 30°, which experienced up to 2 dB C/N0 improvement. Although the benefit in PVT accuracy was not remarkable in our testing, this should become more notable in scenarios where a lower number of satellites are visible or when the LOS signals are obstructed, such as in urban environments. Receiver robustness takes advantage of the possibility of filtering in the polarization domain and the additional number of available degrees of freedom, enabling tracking and PVT solution availability in severe interference scenarios. In particular, a valid PVT solution was still available for an ISR of 53 dB using the dual-polarization array, while the single-polarization array was unable to deliver a valid position. While these improvements are noteworthy, they do come with added cost and complexity of the receiving system, since the number of channels to be processed is doubled.
ACKNOWLEDGMENTS
This article is based on the paper “Interference Mitigation Using a Dual-Polarized Antenna in a Real Environment,” presented at ION GNSS+ 2016, the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation, held Sept. 12–16, 2016, in Portland, Oregon.
MATTEO SGAMMINI received an M.Eng. degree in electrical engineering in 2005 from the University of Perugia, Italy. He joined the Institute of Communications and Navigation of the German Aerospace Center (DLR), Wessling, Germany, in 2008. He is pursuing a Ph.D. in electrical engineering with research interests in interference mitigation techniques for GNSS.
STEFANO CAIZZONE received an M.Sc. degree in telecommunications engineering and a Ph.D. degree in geoinformation from the University of Rome “Tor Vergata,” Italy, in 2009 and 2015, respectively. Since 2010, he has been with the antenna group of DLR’s Institute of Communications and Navigation, where he is responsible for the development of innovative miniaturized antennas.
ACHIM HORNBOSTEL holds a diploma degree in electrical engineering and a Ph.D. degree from the University of Hannover, Germany. He joined DLR in 1989 and heads a working group on algorithms and user terminals at the Institute of Communications and Navigation.
MICHAEL MEURER received a diploma in electrical engineering and a Ph.D. degree from the University of Kaiserslautern, Germany. Since 2006, he has been with DLR’s Institute of Communications and Navigation, where he is the director of the Department of Navigation and of the Center of Excellence for Satellite Navigation. Since 2013, he has also been a professor of electrical engineering and director of the Institute of Navigation at Rheinisch-Westfälischen Technischen Hochschule (RWTH) Aachen.
FURTHER READING
• Authors’ Conference Paper
“Interference Mitigation using a Dual-Polarized Antenna in a Real Environment” by M. Sgammini, S. Caizzone, A. Iliopoulos, A. Hornbostel and M. Meurer in Proceedings of ION GNSS+ 2016, the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, Sept. 12–16, 2016, pp. 275–285.
“Detection and Suppression of PPD-Jammers and Spoofers with a GNSS Multi-Antenna Receiver: Experimental Analysis” by A. Hornbostel, M. Cuntz, A. Konovaltsev, G.C. Kappen, C. Hättich, C.A. Mendes da Costa and M. Meurer in Proceedings of ENC 2013, the European Navigation Conference, Vienna, Austria, April 23–25, 2013.
“Blind Adaptive Beamformer Based on Orthogonal Projections for GNSS” by M. Sgammini, F. Antreich, L. Kurz, M. Meurer and T.G. Nollin in Proceedings of ION GNSS 2012, the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation, Nashville, Tennessee, Sept. 17–21, 2012, pp. 926–935.
“Field Test: Jamming the DLR Adaptive Antenna Receiver” by M. Cuntz, A. Konovaltsev, M. Sgammini, C. Hattich, G. Kappen, M. Meurer, A. Hornbostel and A. Dreher in Proceedings of ION GNSS 2011, the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, Sept. 19–23, 2011, pp. 384–392.
“Suppression of Multipath and Jamming Signals by Digital Beamforming for GPS/Galileo Applications” by Z. Fu, A. Hornbostel, J. Hammesfahr and A. Konovaltsev in GPS Solutions, Vol. 6, No. 4, March 2003, pp. 257–264, doi: 10.1007/s10291-002-0042-2.
• Diversely Polarized Antenna Arrays
“Subspace Fitting with Diversely Polarized Antenna Arrays” by A.L. Swindlehurst and M. Viberg in IEEE Transactions on Antennas and Propagation, Vol. 41, No.12, Dec. 1993, pp.1687–1694, doi: 10.1109/8.273313.
“Direction Finding with an Array of Antennas Having Diverse Polarizations” in IEEE Transactions on Antennas and Propagation, Vol. 31, No.2, March 1983, pp. 231–236, doi: 10.1109/TAP.1983.1143038.
• Antenna Array Signal Processing
“Two Decades of Array Signal Processing Research: The Parametric Approach” by H. Krim and M. Viberg in IEEE Signal Processing Magazine, Vol. 13, No. 4, July 1996, pp. 67–94, doi: 10.1109/79.526899.
“Multilinear Array Manifold Interpolation” by R.O. Schmidt in IEEE Transactions on Signal Processing, Vol.40, No.4, April 1992, pp. 857–866, doi: 10.1109/78.127958.
Rolls-Royce and VTT’s vision of futuristic land-based control center, known as the Future Operator Experience Concept or oX. (Concept: Rolls-Royce)
Rolls-Royce and VTT Technical Research Centre of Finland Ltd. have signed a strategic partnership to design, test and validate the first generation of remote and autonomous ships.
The partnership, established in November 2016, combines and integrates the two company’s expertise to make such vessels a commercial reality.
Rolls-Royce is pioneering the development of remote controlled and autonomous ships and believes a remote controlled ship will be in commercial use by the end of the decade. The company is applying technology, skills and experience from across its businesses to this development.
VTT is an expert in ship simulation and the development and management of safety-critical and complex systems in demanding environments such as nuclear safety. It combines physical tests, such as model and tank testing, with digital technologies, such as data analytics and computer visualization.
They will also use field research to incorporate human factors into safe ship design. As a result of working with the Finnish telecommunications sector, VTT has extensive experience of working with 5G mobile phone technology and wi-fi mesh networks. VTT has the first 5G test network in Finland.
Working with VTT will allow Rolls-Royce to assess the performance of remote and autonomous designs through the use of both traditional model tank tests and digital simulation, allowing the company to develop functional, safe and reliable prototypes.
Two remote-controlled ship prepare to pass. (Artist’s concept: Rolls-Royce)
“Remotely operated ships are a key development project for Rolls-Royce Marine, and VTT is a reliable and innovative partner for the development of a smart ship concept,” says Karno Tenovuo, vice president of ship intelligence for Rolls-Royce. “This collaboration is a natural continuation of the earlier user experience for complex systems (UXUS) project, where we developed totally new bridge and remote control systems for shipping.”
“Rolls-Royce is a pioneer in remotely controlled and autonomous shipping. Our collaboration strengthens the way we can integrate and leverage VTT’s expertise in simulation and safety validation, including the industrial Internet of Things, to develop new products and in the future, enable us to develop new solutions for new areas of application as well,” says Erja Turunen, executive vice president for VTT.
Ship Intelligence will make greater use of ship systems and sensors to enhance both crew and vessel operating efficiency. (Rolls-Royce)
