Satellite receivers come of age

For many years, the United States' Global Positioning System and the Russian equivalent GLONASS were the only GNSS in operation. The playing field is changing and, in order to keep up with the evolving signals, frequencies and satellite constellations, major changes are required.

Scientists laid the groundwork for development of a software-defined receiver and associated components as an alternative to conventional hardware solutions. EU support of the project 'Professional receiver via software radio' (PRECISIO) made this possible.

An initial review of the state of the art led to identification of 13 specific markets for fixed infrastructure receivers. These were fully characterised in terms of users and their purchasing profiles, equipment suppliers, the competitive environment and potential market evolution. PRECISIO scientists then conducted intensive development and testing of the antenna, radio frequency (RF) front end and software-defined receiver.

The antenna, a conical spiral design, reflects a trade-off between two alternatives. One optimises coverage at low elevations and the other improves performances for multi-path signals that do not follow a direct path from transmitter to receiver. Development work focusing on the flexible RF front end highlighted important limitations and considerations for future research.

Design of the software-defined receiver balances general purpose microprocessor-based, digital signal processing-based and field-programmable gate array-based architectures. The receiver validation tool developed specifically for the project will provide important benefits to future validation work.

Researchers used commercial software tools to test components and compare them to commercially available ones. Detailed results including challenges to be addressed in the future have been widely distributed within the GNSS community through conferences in Europe and the United States.

PRECISIO has taken an important first step in investigating the technical requirements and feasibility of a software-defined receiver for GNSS. When realised, it will provide high performance with configurability and flexibility to meet stringent demands of future professional markets and applications.