Phase noise in GNSS transmission / reception system

Emilie Rebeyrol (1) , Christophe Macabiau (1) , Lionel Ries (2) , Jean-Luc Issler (2) , Michel Bousquet (3) , Marie-Laure Boucheret (4)

1 ENAC - Ecole Nationale de l'Aviation Civile
2 CNES - Centre National d'Études Spatiales [Toulouse]
3 SUPAERO
4 ENSEEIHT - Ecole Nationale Supérieure d'Electrotechnique, d'Electronique, d'Informatique, d'Hydraulique et de Télécommunications

Recently the GPSIIR-M and the experimental Galileo satellites (GIOVE-A) were launched making the first step in the orbit-validation of the GPS modernization system and of the Galileo system. The new signals generated by the GPSIIR-M satellite and the Galileo system require modulations which are more complex than the QPSK modulation used in the current GPS system. These new modulations could be a source of distortions for the received signal and require analyses and optimisation. Indeed, in the Galileo system, the Alternate Binary Offset Carrier modulation (ALTBOC) is an innovative modulation proposed for the transmission of the E5 band signal and the Composite Binary Coded Symbol (CBCS) is an innovative signal proposed to optimize the L1 Open service (OS) signal. All the Galileo signals have a constant envelope modulation, thereby allowing the use of saturated power amplifiers with limited signal distortion. However the signals have 8 phase 'scattered' plots in the modulation diagram and a deviation of the modulation plots, with respect to the nominal constellation, could reduce the performance of the tracking loops in the receiver. This deviation of modulation plots constellation could be induced by the Amplitude-Modulation to Phase- Modulation (AM/PM) distortions of the amplifier in the payload. But it could also be resulting from the phase noise created by the instabilities of the payload and receiver clocks. The aim of this paper is to evaluate the impact of the phase noise due to the SSPA (Solid State Power Amplifier) and to the payload and receiver clocks instabilities, on the receiver tracking performance. The case of the Galileo E5 signal will be studied considering a classical payload scheme. The transmission scheme can be described as follows. In the payload unit, the signals are first digitally generated, then converted by a digital-to-analog device, up-converted, and then amplified by the SSPA before being transmitted in their respective frequency bands. In the receiver part, the signals are down-converted, then go through the analog-to-digital converter, and are finally tracked by the Phase Lock Loop and the Delay Lock Loop. The evaluation of the performance in reception is based on the phase error estimated in the Phase Lock Loop. In a first part the way the phase noise affects the signals through the payload assuming a typical performance of the on-board clock generation unit is studied. In this part the phase noise introduced by the SSPA is also investigated and compared to the phase noise introduced by the atomic clock instabilities. Then, the power spectral density of the phase noise due to the receiver clock and its effects on the received signal during the down-conversion and the analog-to-digital conversion are presented. The effect of the incoming signal phase noise on the phase estimation in the Phase Lock Loop is also studied. Finally, to conclude, the impact of the SSPA phase noise and payload/receiver clocks phase noise on the receiver performance are summarized.

Domaines: Traitement du signal et de l'image [eess.SP]; Traitement du signal et de l'image [eess.SP]

Emilie Rebeyrol, Christophe Macabiau, Lionel Ries, Jean-Luc Issler, Michel Bousquet, et al.. Phase noise in GNSS transmission / reception system. ION NTM 2006, National Technical Meeting of The Institute of Navigation, Jan 2006, Monterey, United States. pp 698 - 708. ⟨hal-01021779⟩