Galileo, China's BeiDou satellite navigation system, and related augmented systems, such as the United States' WAAS (Wide Area Augmentation System), Europe's EGNOS (European Geostationary Navigation Overlay System) and Japan's MSAS (Multifunctional gps gnss moduleTransport Satellite Augmentation System), as well as other satellite navigation systems under construction or to be built in the future. The international GNSS system is a complex combination of multi-system, multi-dimensional and multi-modal systems. The advantages of using multi-constellation GNSS receivers include better positioning, navigation, and timing (PNT) signals, increased accuracy, integrity, and improved robustness of applications.
However, multi-constellation receiver development is a complex, time-consuming effort that includes: optimizing the L-band antenna; designing the radio frequency (RF) front end; integrating baseband signal processing algorithms to acquire, track, and apply corrections to the various PNT signals; and coding the application's processing software to extract PNT data from each channel of the baseband and use this information to implement system functions. The designer must also select the appropriate antenna and place it correctly.
Designers can turn to pre-built GNSS modules and development environments to quickly and efficiently integrate positioning functions into the system. Such GNSS modules include RF front ends, baseband processing and embedded firmware, and some GNSS modules also include antennas. This allows for faster development of application processing software.
What is GNSS and PNT?
GNSS and PNT are closely related concepts. satellites are the most common source of PNT signals. satellites are essentially highly accurate synchronized clocks that constantly broadcast their PNT information. the GNSS module receives the PNT signal from a specific satellite and calculates its distance to that satellite. When the receiver knows the distances to at least four satellites, it can estimate its own position. However, the accuracy of the position estimate is affected by various sources of error, specifically.
Clock drift in timing circuits in GNSS satellites
General performance drift of the entire satellite equipment relative to other satellites, also known as satellite drift
Variable performance and drift in multipath reflectors and receivers
Currently, designers can use a variety of different techniques to correct for satellite and atmospheric based GNSS errors.
Improving GNSS Performance
The best way to minimize the effects of errors originating from GNSS receivers is to use the highest performance receivers that are cost and size constrained for a given application. However, even high-performance receivers are not perfect; their performance can be improved to a large extent. It is important to understand these calibration methods because they result in different performance, and some GNSS modules cannot use all of them.