spirent.cn
Posts Tagged "GNSS receivers"

Although there is no specific product standard for EMC in GNSS receivers, testing for immunity to electromagnetic interference has to be an essential part of the product development process. Any receiver designed for low-level signals will inevitably be susceptible to electromagnetic interference. And GNSS receivers inevitably are required to operate reliably in areas where they will be subject to any number of sources of interference. These range from natural phenomena such as solar ra...

Read full post 0 Comments

The GPS Aided Geo Augmented Navigation or GPS and Geo Augmented Navigation system (GAGAN) is a space-based augmentation system (SBAS) funded by the Indian government. Interestingly, Gagan is not just an acronym: it is also a Sanskrit word for the sky. The GAGAN space transponder is due to be launched on 19th May 2011 on an Ariane-5 launcher from the European Space Agency (ESA) spaceport in Kourou, French Guiana. This will be the second attempt to get GAGAN into orbit. The first satelli...

Read full post 0 Comments

In the wider world, an almanac is an annual publication dedicated to information such as weather forecasts, tide tables, lunar cycles etc. A typical almanac will contain tabular information covering a particular field or fields, and will be arranged according to the calendar. However, in the world of satellite navigation systems, the almanac is a regularly updated digital schedule of satellite orbital parameters for use by GNSS receivers. The almanac for any g...

Read full post 0 Comments

Particularly relevant for ground-vehicle-based GNSS receivers, terrain obscuration is the phenomenon of temporary and intermittent masking of GNSS signals when manoeuvring at low altitude in mountainous terrain. This can be a critical limiting factor on the performance of GNSS receivers in certain applications, and so the ability to simulate such effects is an important tool in improving the reliability and performance of GNSS receiver designs. Spirent SimGEN™ software contains a compr...

Read full post 0 Comments

In addition to the new signals to be broadcast under the GPS modernization project, there are to be two significant changes to the existing civilian signals, both designed to improve the performance of GPS receivers. The first is an additional data-free pilot signal and the second is the addition of forward error correction (FEC) encoding to the navigation message. The new data-free signal will be broadcast alongside the normal data signal, acting as an easy-to-acquire pilot signal. On...

Read full post 0 Comments

The official opening on 20th December 2010 of the Fucino Galileo Control Centre, 130km east of Rome, has brought the Galileo global navigation satellite system one step closer to fruition. However, a continuing shortage of funding for the project suggests that while Galileo will be available by 2014, the service will initially be limited. Earlier in 2010, the European Commission confirmed that funding was available to launch four in-orbit validation (IOV) satellites by 2014, with the f...

Read full post 0 Comments
By Andy Walker On January 25, 2011
定位
pseudoranges, GNSS receivers

The pseudorange is an approximation of the distance between a satellite and a GNSS receiver. A GNSS receiver will attempt to measure the ranges of (at least) four satellites as well as their positions when their positional data were transmitted. With the satellites' orbital parameters supplied in the almanac within the message, each position can be calculated for any point in time. The pseudoranges of each satellite are obtained by multiplying the time taken for each signal to re...

Read full post 0 Comments

Although the word “scenario” has been much overused (and misused) in common language, it has particular relevance in terms of testing GNSS receivers. The word can be correctly defined as “an outline or model of an expected or supposed sequence of events”, and this provides an insight to the importance of a test scenario in assessing and/or comparing the performance of one or more GNSS receivers. A GNSS simulator under software control can be used to generate test scenarios of varying d...

Read full post 0 Comments
By Andy Walker On October 5, 2010
定位
Multipath, GNSS receivers

On the face of it, the marine environment might appear relatively benign for GNSS receivers. After all, there is virtually no chance of signal obscuration from buildings or trees (although the odd cliff might come into play), so logically, the design of a marine GNSS receiver should be a piece of cake. However, such devices are particularly prey to multipath interference – both from the surface of the sea and from the superstructure of the vessel itself. And left untreated multipath ef...

Read full post 0 Comments
By Andy Walker On August 25, 2010
定位
Multipath, GNSS receivers

On the face of it, the marine environment might appear relatively benign for GNSS receivers. After all, there is virtually no chance of signal obscuration from buildings or trees (although the odd cliff might come into play), so logically, the design of a marine GNSS receiver should be a piece of cake. However, such devices are particularly prey to multipath interference–both from the surface of the sea and from the superstructure of the vessel itself. And left untreated multipath effe...

Read full post 0 Comments
By Andy Walker On August 16, 2010
定位
ephemeris, GNSS receivers, TTFF

An ephemeris is quite simply a table giving the coordinates of a celestial body at specific times during a given period. The word comes from the same Greek root as “ephemeral”, which strictly means short-lived, but has come to mean inconsequential. However, in terms of GNSS systems, the ephemeris is certainly not inconsequential. Each GNSS satellite includes ephemeris data in the signal it transmits. This comprises a set of parameters that can be used to accurately calculate the locati...

Read full post 0 Comments

Despite continuing delays in its introduction, when the new European Union funded Galileo constellation goes live in 2014 it will provide a number of novel services. Designers of next-generation Multi-GNSS systems need to factor in these new capabilities in order to keep their equipment ahead of the competition. Importantly, Galileo is designed provide more precise location data from that provided by GPS or GLONASS, and will be accurate down to the one-meter range. The data will also i...

Read full post 0 Comments

To those engineers more familiar with automotive or marine navigation systems, the concept of using GNSS receivers for navigation on railways might seem a case of “overkill”. After all, there are only so many places a train can go, and these are firmly bounded by two steel rails. However, the exact knowledge of the position of any train on any rail system allows the rail operator to both improve service and increase traffic density by reducing the headways associated with fixed line-side sig...

Read full post 0 Comments

It goes without saying that any RF device as sensitive as a GPS receiver will be inherently vulnerable to interference. Clearly, care needs to be taken at both the design and integration stages to minimise interference effects. But what interference sources need to be considered? And how do you know if your receiver can deal with them? Most potential sources of interference are obvious and predictable: The effects of fixed-frequency transmitters for TV, radio and the like can easily be modelle...

Read full post 0 Comments
× Spirent.com uses cookies to enhance and streamline your experience. By continuing to browse our site, you are agreeing to the use of cookies. If you would like to learn more about how we use cookies