Abstract
With the modernization of the GPS system well on its way and Galileo transmitting its first signals, there will be a number of new GNSS signals widely available in the near future. Some of the signals will be very wide-band; they are intended to supply a superior tracking accuracy and improved multipath performance. Some of the signals are modulated using the binary offset carrier modulation. Furthermore these new generation signals can be combined to offer the use of dual-frequency techniques for the general public. The Galileo signals in the E5 band are good candidates for a wide-band signal that will be available for use by the general public. Dual frequency capability is foreseen in combination with the signals in the L1 band. The bandwidth occupied in E5 is more than 50 MHz. Making receiver design challenging; to allow reception of such signals the RF-front-end and the digital parts of a receiver must be able to operate at a sufficient bandwidth with a correspondingly high sample rate. These demands are hurdles facing the implementation of a mass-market dual-band GNSS receiver. On the other hand such a receiver would outperform a single frequency narrow bandwidth heritage GPS L1 receiver with regard to many aspects. Direct-conversion receiver architecture simplifies the construction of a wide-band GNSS receiver. The incoming signal is mixed with a locally produced complex RF carrier converting the incoming signal directly to baseband where low pass filters are used for the channel selection and to prevent aliasing. The use of low-pass filters is an advantage compared to the band-pass filters used in heterodyne receivers; they can be integrated monolithically in the semiconductor reducing the number of components. The use of such a receiver is analysed in this PhD in theory and practice, including the construction of such receiver. A dual frequency receiver was built combining the developed direct-conversion wide-band receiver for the E5 band and a heritage narrow band heterodyne receiver for the signals in the L1 band. The direct conversion receiver was assessed in comparison to the traditional heterodyne receiver with positive outcome. The direct conversion receiver performed well in all tests. The new receiver enabled further investigations on the acquisition and the tracking of the new GNSS signals. In particular the AltBOC modulated Galileo signal in the E5 band was investigated, which resulted in a novel improved processing scheme combining two of the most advanced tracking routines for this signal. This research was carried out at Surrey Satellite Technology Ltd (SSTL) under their joint supervision with Surrey Space Centre. Much of the funding was provided under a cooperation agreement with the UK branch of the Mitsubishi Electric R&D Centre Europe based in Guildford. The work of this thesis will feed into the new generation GPS and Galileo receivers currently under development at SSTL.