S-curve bias optimization of navigation signals based on a pre-distortion method

Abstract

Nonideal radio-frequency (RF) emission channels directly affect the quality of navigation signals. In particular, the deviation in the pseudo-range, caused by differences among the RF channels of multiple satellites, can decrease user positioning accuracy. Previous studies have primarily focused on designing pre-distortion filters to improve the performance of non-ideal RF channels in navigation signal generators. However, this study shows that using a pre-distortion filter alone limits the improvement of the S-curve bias because the constant-envelope character is compromised, and the nonlinearity of the high-power amplifier (HPA) becomes more pronounced. Applications that require better accuracy require require a smaller S-curve bias. This study proposes a method to compensate for the nonideal RF channel by using pre-distortion that considers both the nonlinear HPA and nonideal filter characteristics. The proposed method is validated through numerical analysis and simulations. The results show that the proposed method can reduce the S-curve bias across different receiver configurations. This study is a useful reference for improving the quality of navigation signals, particularly in terms of correcting the S-curve bias.