Analysis of Receiver Implementation Losses for GNSS Signals

This paper presents an analysis of the implementation losses, <tex>$L_{i m p}$</tex>, affecting a GNSS receiver. The implementation losses are the SNR loss at the correlator output due to payload and receiver imperfections with respect to an ideal case. <tex>$L_{\text {imp }}$</tex> is necessary to compute the link budget <tex>$C / N_{0}$</tex>, which must be compared to different <tex>$C / N_{0}$</tex> thresholds to guarantee the correct processing of a GNSS signal. This paper provides a physical meaning as well as a mathematical definition of the 4 terms constituting the implementation losses; moreover, a computation scheme is also derived where the elements (signal noise, receiver) affecting each of the 4 terms are highlighted. Finally, this paper applies the theory to GPS L5, Galileo E5a and SBAS L5 signals for a civil aviation receiver; different signal definitions are considered (frequency bounding of the power spectrum density) and numerical values are calculated; 0.7 dB can be expected for GPS and Galileo, and 1.27 dB for SBAS, plus the accommodation of the miscellaneous loss term.