Furuno will release a high-performance multi-GNSS timing antenna, the AU-500, in July. The antenna is suitable for time synchronization applications.
The AU-500 supports all constellations in the L1 and L5 bands, including GPS, QZSS, GLONASS, Galileo, BeiDou, and NavIC. A built-in noise filter eliminates interference in the vicinity of 1.5 GHz caused by 4G/LTE mobile base stations as well as other radio waves that can adversely affect GNSS reception.
The antenna is equipped with lightening protection and features a high-quality polymer radome that prevents snow accumulation. It is also waterproof and dustproof in compliance with IP67.
The AU-500 achieves the best performance in time accuracy and robustness fundamental in critical infrastructure, when combined with Furuno’s GNSS receiver, GT-100.
In addition to the AU-500, Furuno will also launch the AU-300, an L1 single-band antenna with the same level of performance as AU-500, except L5 signal reception.
The Moonlight initiative will provide sustainable lunar data-relay services for communication and navigation around the Moon. (ESA Moonlight Study conceptual drawing.) (Image: SSTL/Airbus/ESA)
GNSS researchers presented hundreds of papers at the 2022 Institute of Navigation (ION) GNSS+ conference, which took place Sept. 19–23 in Denver, Colorado, and virtually. The following five papers focused on lunar and space applications. The papers are available now.
MTO Navigation Using Lunar Signals
The moon transfer orbit (MTO) is becoming increasingly important as several national space agencies are planning moon exploration soon, with projects such as NASA’s Artemis. In previous research, the GPS navigation accuracy on the MTO reached 200 m at the moon altitude by using GPS signals emitted from the far side of Earth. As accuracy on a low-Earth orbit (LEO) using GPS is a few meters, 200 m accuracy is not accurate enough to support lunar exploration. The deterioration of accuracy is due to the poor geometry of the GPS satellites that became visible from the MTO.
The authors want to achieve an accuracy of less than 100 m in MTO by using other navigation sources, including the lunar navigation satellite system (LNSS) to be deployed in the moon’s orbit. The LNSS signals will come from the far side of the moon, similar to the signals of GPS satellites coming from the opposite side of Earth. Its satellites will be pointed towards the moon to provide positioning, navigation and timing services on the moon surface, especially at the lunar South Pole region
The researchers have been conducting the simulation evaluation for the MTO navigation accuracy using signals coming from the moon and assume that these signals will be emitted from beacons on the moon surface or the LNSS.
Murata, Masaya; Kogure, Satoshi; “Moon Transfer Orbit Navigation Using Signals Coming from the Moon.”
Designing the Smallsat-Based LNCSS
There is growing interest in the use of a smallsat platform for the future lunar navigation and communication satellite system (LNCSS); however, many design considerations are not finalized for the smallsat-based LNCSS, such as choice of the satellite clock, satellite orbital parameters and the constellation size.
Using the Systems Tool Kit simulation software, the authors examined various LNCSS constellation case studies based in elliptical lunar frozen orbit and with a low-grade chip-scale atomic clock.
They evaluated case studies of navigation design considerations including position and timing accuracy, lunar user equivalent ranging error, and dilution of precision. As for case studies of communications design considerations, the authors examined daily data volume, availability and data rate. Finally, they examined smallsat factors including the cost, size, weight and power of the satellite payload.
The paper includes trade-off analysis in satisfying the preliminary design criteria outlined by international space agencies and commercial space companies.
Bhamidipati, Sriramya; Mina, Tara; Sanchez, Alana; Gao, Grace; “A Lunar Navigation and Communication Satellite System with Earth-GPS Time Transfer: Design and Performance Considerations.”
Developing an SDR for Space
A geostationary satellite (GEO) equipped with the satellite-based augmentation system (SBAS) function has a transmitter for GNSS correction signals at the L1 and L5 bands. This transmitter could interfere with the GNSS space service volume (SSV) receiver in the same satellite, so L1 and L5 signals cannot be used for the GEO SBAS satellite. However, the use of GPS L2C signals can be an alternative.
The authors of this paper present the development of a GPS L2C signal generator for the SSV in GEO simulation. They present the simulation process for GEO satellites and the structure of the GPS L2C signal generator.
In this study, a verification through the receiver test with a GNSS software-defined receiver is included to show the possibility of the designed signal simulator. The validation is performed by analyzing the programmable system device, the results of the acquisition, code/carrier tracking, and the C/N0 estimation.
Lee, Hak-beom; Choi, ByeongHyun; Song, Young-Jin; Won, Jong-Hoon; Kwon, Ki-Ho; “Development of GPS L2C Signal Generator for SSV in Geostationary Orbit Simulation.”
Differential Positioning on the Moon
This paper introduces a new concept of delivering the pseudorange correction calculated at a reference station on the lunar surface, as a part of the lunar navigation satellite system (LNSS) navigation message. The concept enables LNSS users to apply differential positioning using pseudorange correction without adding new hardware to their receivers.
The authors propose the differential positioning technique to reduce the signal-in-space range error of LNSS satellites and the coordinate transformation errors from Earth-centered fixed frame to lunar reference frame — the dominant errors in satellite positioning by LNSS.
The proposed reference station is equipped with instruments to externally estimate its own position relative to the lunar reference frame. The user on the lunar surface would then perform differential positioning using the station coordinate and pseudorange correction obtained at the reference station.
In this study, the simulation results using eight elliptical lunar frozen orbit satellites show that the real-mean-squared values for both horizontal and vertical positioning errors with differential correction are reduced to 1/10 of those without differential correction, even at 10 degrees latitude from the reference station at the lunar South Pole.
Akiyama, Kyohei; Murata, Masaya; Kogure, Satoshi; “Differential Positioning Performance on Lunar South Pole Region Using Lunar Navigation Satellite System.”
GEO Precise Orbit Determination
Using GPS in satellites in geostationary (GEO) orbits provides advantages by improving position, velocity and timing data, reducing operating costs and providing autonomous orbit control for station keeping. This paper presents the result of the onboard data evaluation and precise orbit determination of an optical data-relay satellite (ODRS) using GPS L1 C/A code and carrier-phase observations for 74 days.
As a result of precise orbit determination, the authors found that both code- and carrier-phase observations are affected by the ionospheric delay when signals pass through the plasmasphere located above the ionosphere.
Several methods were implemented during this research to reduce the effect of the plasmasphere, including setting a higher cut-off altitude, applying correction sequences generated from orbit determination residuals, and applying a new observation noise model depending on the GPS off-nadir angle. Results show that the correction sequences and the new noise model improve the internal orbit consistency. The authors also found that the orbit bias in radial direction due to negatively biased carrier-phase observations is mitigated from –51 cm to –17 cm by setting a higher cut-off altitude and applying correction sequences.
Matsumoto, Takehiro; Sakamoto, Takushi; Yoshikawa, Kazuhiro; Kasho, Sachiyo; Nakajima, Ayano; Nakamura, Shinichi; “GEO Precise Orbit Determination Using Onboard GPS Carrier Phase Observations of Optical Data Relay Satellite.”
The GP-L1-32-T-MNT GPS timing antenna with mount included, RHCP polarized, 1.571 to 1.61 GHz. (Photo: RadioWaves)
RadioWaves, an Infinite Electronics brand and a manufacturer of high-quality microwave antennas and accessories, has released a new series of GPS/GNSS timing antennas that cover L1 and L5 GPS bands.
The new series of GPS/GNSS timing antennas provide axial ratio and higher accuracy for the reception of satellite timing signals and reference frequencies for enhanced phase synchronization in precision network deployments.
The high gain, low noise figure of 2 dB and high out-of-band rejection provided by these antennas allows for the use of longer and cost-effective cables for easy and flexible installs. They also feature a VSWR less than 1.8:1 and are compatible with several existing mounting brackets. In addition, thee fully ruggedized, weather-sealed antennas are IP67 compliant for use in outdoor and marine environments.
The antennas come equipped with built-in surge protection and support a wide range of GNSS including GPS, GLONASS, BeiDou and Galileo, as well as Iridium. Increased position accuracy in densely populated urban areas, flexible installation, and improved system security make RadioWaves’ latest antenna offering a valuable system component, the company said.
Models include
GP-L1-L5-40-N, an L1+L5 GPS timing antenna, 1.166 to 1.218 GHz and 1.559 to 1.606 GHz
GP-L1-32-T, a L1 GPS timing antenna, RHCP polarized, 1.574 to 1.61 GHz
GP-L1-32-T-MNT, an L1 GPS timing antenna with mount included, RHCP Polarized, 1.571 to 1.61 GHz.
Telit has launched the SE868SY-D multi-frequency, high-precision GNSS receiver module for applications that require high accuracy, fast updates, multi-constellation support and multipath resistance.
At 11 x 11 mm, the SE868SY-D accommodates ultra-compact devices and IoT trackers.
Available now, the high-precision SE868SY-D module is Telit’s first multi-frequency, multi-constellation GNSS receiver module, featuring an ultra-sensitive -167 dBm (tracking) RF front end. By using both the L1 and L5 bands, the SE868SY-D supplies a significantly higher location accuracy than single-frequency devices — even in high-multipath environments such as urban canyons, Telit said.
This sub-1-meter precision is a major reason ABI Research expects more than 1 billion multi-frequency GNSS devices to ship annually by 2023.
The SE868SY-D is the first product from a new strategic collaboration between Sony and Telit, and features Sony’s next-generation CXD5610 GNSS receiver large-scale integrated circuit (LSI).
The Telit SE868SY-D is designed for battery-powered applications such as IoT trackers and wearables. With less than 45 mW in L1+L5 tracking mode, the module has low power consumption, despite using both L1 and L5 bands.
For high-dynamic applications, the SE868SY-D a high update rate of up to 25 Hz. Its high-accuracy, one-pulse-per-second signal also makes the module suitable for timing applications.
“With the new SE868SY-D, Telit is uniquely prepared to meet the burgeoning global demand for multi-frequency, multi-constellation GNSS receivers for IoT trackers, wearables and more,” said Eric Lagorce, Telit business development director. “The SE868SY-D also perfectly complements Telit’s two decades of GNSS expertise and its broad portfolio, and highlights the potential of our strategic collaboration with Sony.”
The Telit SE868SY-D provides pin-to-pin compatibility for applications based on Telit’s legacy GPS module JF2 and GNSS module SE868V3.
GNSS receivers first reached the commercial domain in the early 1980s. They were bigger than your average carry-on suitcase, weighed more, and consumed so much power that they needed to be plugged into an outlet. But technology advanced quickly, and by the mid-1980s commercial GNSS receivers were appearing in survey and marine markets.
Generation 1. The first generation of truly mobile receivers, in the late 1990s, used only L1 C/A code and were typically found in rugged handhelds for outdoor enthusiasts. The receivers began appearing in mobile phones in the late 1990s.
Gen 2. The second generation added GLONASS. These receivers had to have wider bandwidths on the order of 20-30 MHz to support the GLONASS FDMA signals at a slightly offset frequency from GPS L1.
Gen 3. These receivers added support for Galileo. They started appearing in mainstream cellphones in about 2014. These phones still retained a single frequency front end in the L1 band, but had separate digital processing chains for all three satellite systems.
Gen 4. This evolution added support for BeiDou and a single sideband L5 receiver where BeiDou, Galileo and GPS all have modernized signals. These receivers first appeared in phones in 2019 because of the added size, power and complexity of supporting a dual-band receiver. The front end is a burden on many phone models, especially with the rise of 5G. Plus, the L1 band has reliability issues with jamming and interference. The receivers only support a single sideband at L5 and are not utilizing the full capability of L5.
Every GNSS user in every segment benefits from using the new, modernized signals in the L5 band. L5 signals are more accurate, reliable and available in sufficient numbers to support all user segments. Here are the major advantages of L5 over L1.
Signal structure (narrow correlation peak) accuracy
Wide bandwidth (multipath mitigation) accuracy
Pilot codes (longer coherent integration increasing SNR)
Multiple constellations and signals with common signal structure
Stronger signal transmission
Cleaner band with less interference
Signal availability
The benefits of L5 are clear. That’s why many GNSS suppliers have started building L1/L5 solutions, and they are starting to appear in smartphones. It seems to be a natural progression to add an L5 receiver chain on top of an existing L1 solution and be able to reap the benefits. But bringing along the legacy L1 solution could actually have a negative impact on the overall solution.
The oneNav L5 mobile GNSS system architecture. (Image: oneNav)
L5 Wideband Receiver
We set out to build a fifth-generation GNSS receiver for mobile consumer products. Its single-frequency design only uses the modernized, wideband signals at L5. It has an acquisition engine sophisticated enough to acquire L5 signals directly and a navigation engine that uses artificial intelligence/machine learning (AI/ML) techniques to fully exploit all the signals in 50-MHz wideband at L5.
Optimized engine. Building an acquisition engine for the L5 signal is a huge mathematical task. Since the codes are 10 times longer and have a 10 times faster chipping rate, it’s a 100 times more difficult search problem. The oneNav engine solves that problem with a customized array processor that has a GPU-like approach, maintaining TTFF.
Single-frequency architecture. Pure L5 architecture eliminates the need for a second RF chain. The oneNav L5 engine uses common hardware for signals from all GNSS systems.
Increased sensitivity. The L5 signal has a modernized signal structure that allows for increased sensitivity for both acquisition and tracking. With wideband architecture, all parts of the L5 signal can be combined for maximum performance and significantly more signal strength than L1.
Improved time to fix. Dual-band receivers first get a fix on L1 and then begin the acquisition process on L5. By performing the L5 acquisition directly, we save time.
Acquisition reliability. The L1 signal structures do not have the longer primary codes and the secondary codes like modernized signals on L5 that mitigate many of the reliability problems associated with cross correlation, jamming and spoofing.
Improved tracking and measurement. Using the full bandwidth allows a more sophisticated channel estimation than a simple pseudorange measurement. With multiple signals contained within the L5 wideband signal, we gain advantages from channel diversity.
AI/ML navigation engine. A cloud-connected navigation engine uses advanced AI/ML techniques to further improve navigation accuracy. Sophisticated ML techniques to predict if the received signal is line of sight and predict the measurement error caused by multipath. The cloud service allows reflected signals to be used correctly in the navigation solution rather than being excluded due to their multipath content. A sophisticated pattern-matching-based positioning algorithm combines the pseudorange measurements and the environment’s 3D building map model to enhance positioning accuracy in deep urban canyons.
IP Core
We designed the oneNav receiver as a licensable IP core rather than a discrete silicon solution. The complete solution includes all the firmware and an RF front-end reference design from antenna to A/D converter. This allows customers to determine how to best bring the oneNav advantages to their products.
The IP core can be integrated into a larger ASIC such as a modem or an SOC. It could also be implemented as a discrete silicon solution. The RF could be combined into any of these solutions or implemented with other RF components in the system. The measurement and position engine firmware can be run on a dedicated CPU or shared in either the same or different CPUs for flexible system integration optimal for various applications. The IP core is both process independent and scalable. An integrated GNSS core means that GNSS performance can be maintained across multiple platforms and silicon generations, providing consistency of measurement and positioning performance needed to maintain system reliability and fusion.
In my opinion, the Pure L5 wideband receiver can be considered a next generation — or fifth generation — of GNSS for mobile consumer products.
