Signal Processing

Innovation: The Devil Is in the Details

July 1, 2012By
FIGURE 4. A CPSE observed on SVN48 (PRN07) on September 15, 2010, at 19:21:42 GPS Time. (Click to enlarge.)

Looking Closely at Received GPS Carrier Phase
The stability of a received GPS signal determines how well the receiver can track the signal and the accuracy of the positioning results it provides. While the satellites use a very stable oscillator and modulation system to generate their signals, just how stable are the resulting phase-modulated carriers? In particular, do received signals always conform to the published system specifications? In this month’s column we take a look at a specially designed receiver for analyzing GPS carrier phase and some of the interesting results that have been obtained. read more

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

Reminder: Leap Second This Weekend

June 29, 2012By

News courtesy of CANSPACE Listserv. Likely none of us needs a reminder as the upcoming leap second has been all over the news outlets for the past few days. But just to provide the details again, read this article. Presumably, all GPS receiver manufacturers have checked to make sure their receivers will handle the leap second properly. However, at least... read more

This article is tagged with , and posted in Featured Stories, Signal Processing, Timing

Massive GPS Jamming Attack by North Korea

May 8, 2012By

Large coordinated cyber attacks from North Korea near its border with South Korea produced electronic jamming signals that affected GPS navigation for passenger aircraft, ships, and in-car navigation for roughly a week in late April and early May. To date, no accidents, casualties, or fatalities have been attributed to jammed navigation signals aboard 337 commercial flights in and out of South... read more

Innovation: Simulating GPS Signals

May 1, 2012By
FIGURE 3. Signal Architect simulation flow. (Click to enlarge.)

It Doesn't Have to Be Expensive
GNSS signal simulators can be expensive and beyond the limited budgets of many researchers. In this month’s column, we look at one company’s approach to providing GNSS signal simulation at a low cost — one that virtually any researcher can afford.GNSS signal simulators can be expensive and beyond the limited budgets of many researchers. In this month’s column, we look at one company’s approach to providing GNSS signal simulation at a low cost — one that virtually any researcher can afford. read more

Innovation: Ionospheric Scintillations

April 1, 2012By
FIGURE 1 Global occurrence characteristics of scintillation. (Figure courtesy of P. Kintner)

How Irregularities in Electron Density Perturb Satellite Navigation Systems
In this month’s column, the international Satellite-Based Augmentation Systems Ionospheric Working Group presents an abridged version of their recently completed white paper on the effect of ionospheric scintillations on GNSS and the associated augmentation systems. read more

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