Abstract: The low earth orbit (LEO) navigation augmentation system is currently a hot topic in the field of global satellite navigation system (GNSS), and its main development direction is to accelerate the convergence speed of precise point positioning (PPP) by broadcasting dedicated LEO navigation augmentation signal. However, LEO satellites have lower orbital heights and faster motion speeds, resulting in a Doppler range of over ±30kHz for LEO navigation augmentation signal, much higher than the ±5kHz range of traditional GNSS signals. How to fast acquire the LEO navigation augmentation signal has become a challenge. An LEO navigation augmentation signal with anti-Doppler characteristics is proposed to address this issue. The proposed signal has the constant envelope characteristic, which is beneficial for signal generation. More importantly, the proposed signal exhibits the multi-peak correlation properties in the Doppler dimension, enabling fast acquisition. For the proposed signal, a two-step method is designed to achieve fast acquisition: the first step is to acquire the signal within the ±5kHz Doppler range, and the second step is to utilize the multi peak correlation characteristics of the Doppler dimension to determine the ambiguity of the Doppler dimension and obtain the final Doppler and code phase. The simulation results show that the designed LEO navigation augmentation signal only needs to search for the Doppler dimension within ±5kHz range during the acquisition phase, which is more than 6 times faster than the acquisition speed of the conventional LEO navigation augmentation signal, and that the acquisition efficiency is comparable to traditional GNSS signals. The proposed LEO navigation augmentation signal has the anti-Doppler characteristics, and its acquisition time does not change with the Doppler range. It can provide reference for the design of LEO navigation augmentation signal.

Key words: LEO navigation augmentation signal, anti-Doppler, signal acquisition, constant envelope, global navigation satellite system