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

Abstract Nonideal radio-frequency (RF) emission channels directly affect navigation signal quality. 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 mainly focused on designing pre-distortion filters to improve the performance of non-ideal RF channels in navigation signal generators. However, our findings indicate that using a pre-distortion filter alone results in limited 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. More applications that require better accuracy 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 was 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 provides a reference for improving the quality of navigation signals, particularly in terms of correcting the S-curve bias.