Innovation: Position estimation using non-line-of-sight GPS signals

March 15, 2017By and
FIGURE 9.  Normalized overall correlation with contributions from all satellites, including the satellite mirror-image of PRN 5.

Reflected Blessings.
A technique developed by researchers at the University of Illinois at Urbana-Champaign distinguishes a reflected non-line-of-sight (NLOS) signal of a particular satellite from the LOS signal and characterizes the NLOS signal as coming from a virtual mirror-image satellite in the direction of the signal reflection point. By using information on the position and orientation of the reflector, the NLOS signal can be treated as an additional LOS signal. read more

Innovation: Mitigating interference with a dual-polarized antenna array in a real environment

FIGURE 2. CW interference scenario.

Double Take
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. read more

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Innovation: Correlator beamforming for low-cost multipath mitigation

January 13, 2017By , and

GNSS Pest Control
A new solution for GNSS multipath employs a multi-element antenna with RF signal switching and a single front end to reduce complexity, power consumption and cost. Correlator beamforming, initially used in the 2.4 GHz frequency band where it has proven effective at mitigating multipath in heavy industrial environments, has been successfully adapted for GNSS use. read more

Innovation: Precise positioning using raw GPS measurements from Android smartphones

November 7, 2016By and
FIGURE 8. Position estimates as in Figure 7 but with precise external ionospheric information.

Precision GNSS for everyone
In this month’s column, we take a look at some initial efforts to independently process smartphone measurements. How good are the results? Read on. read more

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Innovation: Better GNSS navigation and spoofing detection with chip-scale atomic clocks

October 12, 2016By and
FIGURE 2. Test track. The yellow ellipse marks a treed lane with signal obstructions.

Getting there more safely
We discuss how chip-scale atomic clocks can help us navigate more safely by allowing a GNSS receiver to position itself more accurately even with only three satellites in view, and to protect itself by being able to detect a sophisticated spoofing attempt. read more

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Innovation: Galileo cycle-slip detection

September 1, 2016By and
FIGURE 3.  Statistical and absolute thresholds.

How four frequencies help when the ionosphere is disturbed
The authors explore how cycle slips in Galileo carrier-phase measurements can be more effectively detected using four frequencies. read more

Innovation: Evolutionary and revolutionary

July 11, 2016By
FIGURE 1.  An extended bandwidth GNSS antenna. The lower and connected dipoles are tuned to L2 and the upper coupled shorted dipoles are tuned to L1. Current flow in the circular waveguide of the GNSS antenna is shown. Strong circumferential currents flow at the top of the waveguide. Red indicates large currents and the arrows show the directions of the current flow.

The development and performance of the VeraPhase GNSS antenna
We take a look at a revolutionary design of a multi-frequency multi-GNSS antenna. Our authors discuss how the antenna evolved from a research project in academia to a commercial product about to enter the market. read more

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Innovation: There’s an app for that

June 13, 2016By
Figure 7. Total electron content in TECu across South America on Feb. 5, 2015, between 19:00 UTC and 19:15 UTC.

Using a smartphone for GNSS ionospheric data collection
In this month’s column, we take a look at the use of a smartphone app to collect GNSS ionospheric data. The authors' app-centric approach provides a software framework and output format that remain the same for different receivers. read more