Spectrally Efficient Constant Envelope Modulation for GNSS Signals

Abstract

As the L-band spectral resources for GNSS services are almost exhausted, new bands such as S-band and C-band has been considered for new GNSS signals. In addition to the traditional signal features, out-of-band radiation is an important factor to be considered for signal designing in these new bands. In this paper, a mathematical model for the optimization of GNSS signal waveforms was constructed by integrating ranging accuracy, anti-jamming performance and out-of-band radiation suppression requirements. In combination with numerical optimization methods, a spectrally efficient constant envelope modulation scheme based on phase trajectory optimization was proposed. The modulated signal has a full-response continuous phase waveform, which facilitates signal processing and implementation at both ends of the transmission and reception. In addition, in the signal design, the balance between signal accuracy, anti-interference performance and out-of-band radiation suppression can be achieved through the adjustment of the weight coefficient. The simulation results show that the out-of-band radiation can be reduced by about 7.2-42.7 dB compared with the existing scheme when the signal performance difference is lower than 2 dB.