The Navigation Signal Generation Unit (NSGU) generates the signal that enables users on the ground to determine their position and to benefit from information that is distributed by those satellites.
The NSGU formats navigation data that are received via the satellite´s mission receiver and modulates them on the spread spectrum coded navigation signals. Further, it establishes a time-base by processing data from the on-board clocks, which is added to the message stream.
The analogue output signals from the NSGU are passed to the L-band up-converter and power amplifier. The NSGU comprises a microprocessor control module, a power converter and the NSG module.
The module allows to generate the three navigation signals L1, E6 and E5 simultaneously.
It is based on a mixed digital and analog board, which performs all high-speed signal generation and processing tasks of the NSGU.
The signal processing task is handled by three identical ASICs called GASIG. Both the board and the GASIG ASIC were designed and tested by RSA. The complex generated E5 baseband signals are upconverted to an intermediate frequency of 122.76MHz by use of a quadrature upconverter located on the NSG module.
The NSG Module is the main constituent of the NSGU (Navigation Signal Generation Unit) designed by a team of RUAG Space and Airbus Defence & Space. It was accommodated on two satellites of the Galileo In-Orbit Validation Phase.
The module is the result of comprehensive pre-development work, that had started in the year 1999. A pre-cursor version of the above described NSG module was launched on-board of the GIOVE B (Galileo In-Orbit Vadidation Experiment B) Satellite on 27 April 2008. This satellite allowed to successfully transmit the multiplexed BOC (MBOC) signal for the first time in the history of GNSS (Global Navigation Satellite System).