Signal Processing

Patch Antennas for the New GNSS

February 1, 2012By

Small ceramic patch elements offer nearly perfect single-frequency receive characteristics and have become the standard for GPS L1 antennas. However, the new generation of GNSS receivers now being introduced track many satellites in multiple constellations. Are these narrow-band devices up to the task for wider bandwidths? read more

This article is tagged with , and posted in Signal Processing

Innovation: Know Your Enemy

January 1, 2012By
Inno-Opener

Signal Characteristics of Civil GPS Jammers
GPS jamming is a continuing threat. A detailed understanding of how the available jammers work is necessary to judge their effectiveness and limitations. A team of researchers from Cornell University and the University of Texas at Austin reports on their analyses of the signal properties of 18 commercially available GPS jammers. read more

Straight Talk on Anti-Spoofing: Securing the Future of PNT

January 1, 2012By
Spoofing

Disruption created by intentional generation of fake GPS signals could have serious economic consequences. This article discusses how typical civil GPS receivers respond to an advanced civil GPS spoofing attack, and four techniques to counter such attacks: spread-spectrum security codes, navigation message authentication, dual-receiver correlation of military signals, and vestigial signal defense. Unfortunately, any kind of anti-spoofing, however necessary, is a tough sell. read more

Low-Complexity Spoofing Mitigation

December 1, 2011By
Figure 3. Null steering toward the spoofer signals.

Most anti-spoofing techniques are computationally complicated or limited to a specific spoofing scenario. A new approach uses a two-antenna array to steer a null toward the direction of the spoofing signals, taking advantage of the spatial filtering and the periodicity of the authentic and spoofing signals. It requires neither antenna-array calibration nor a spoofing detection block, and can be employed as an inline anti-spoofing module at the input of conventional GPS receivers. read more

This article is tagged with , and posted in GNSS, Receiver Design, Signal Processing

Innovation: Digging into GPS Integrity

November 1, 2011By
Inn-opener

Charting the Evolution of Signal-in-Space Performance by Data Mining 400,000,000 Navigation Messages
There are four important requirements of any navigation system: accuracy, availability, continuity, and integrity. In this month’s column we take a look at one particular aspect of GPS integrity: that of the signal in space and find out how trustworthy is the satellite ephemeris and clock information in the broadcast navigation message. read more

This article is tagged with , and posted in From the Magazine, GNSS, Innovation, Signal Processing

Lone Sentinel: Single-Receiver Sensitivity to RF Interference

July 1, 2011By
Tong_open2

Using signal-to-noise measurements from a single commercial-grade L1 GPS receiver, it is possible to detect interference or jamming that is above the thermal noise floor and below a power that causes loss of position. read more

This article is tagged with and posted in GNSS, Signal Processing

Future Wave: L1C Signal Performance and Receiver Design

April 1, 2011By
L1C-3

The new GPS L1C signal will be broadcast by the Block III satellites, with first launches as early as 2014. L1C innovations significantly enhance PNT performance as well as interoperability with other GNSS signals. The authors describe the benefits of its new features and how best to make use of each one. read more

This article is tagged with , , and posted in Receiver Design, Signal Processing

Innovation: Realistic Randomization

March 1, 2011By
Figure 3. Data collection, Gamla Stan (Old Town), Stockholm (route and street view).

New Way to Test GNSS Receivers
In this month’s article, we look at an approach to GNSS receiver testing that uses realistic randomization of signal amplitudes based on histograms of carrier-to-noise-density ratios observed in real-world environments. It can be applied to any simulator scenario, independent of scenario details (position, date, time, motion trajectory, and so on), making it possible to control relevant parameters such as the number of satellites in view and the resulting dilution of precision independent of signal-strength distribution. The method is amenable to standardization and could help the industry to improve the testing methodology for positioning devices — to one that is more meaningfully related to real-world performance and user experience. read more

This article is tagged with , , and posted in GNSS, Innovation, Signal Processing