# Improving S-Curve Bias Through Joint Compensation of HPA and Filter Distortions

## TL;DR

This paper proposes a new method to improve navigation signal quality by jointly compensating for distortions from a filter and a power amplifier, enhancing high-precision positioning.

## Contribution

A novel joint compensation method is introduced to reduce S-curve bias by addressing both linear and nonlinear distortions in navigation signal transmission.

## Key findings

- The proposed joint compensation method significantly reduces S-curve bias (SCB) in navigation signals.
- The method combines iterative predistortion filter design with adaptive nonlinear distortion compensation using a lookup table.
- The approach improves signal quality and supports high-precision positioning services.

## Abstract

What are the main findings?
This study reveals that the predistortion filter breaks the constant envelope characteristic of the signal, resulting in nonlinear distortion after passing through the HPA.To address the distortion introduced by both the filter and the power amplifier in the navigation signal transmission chain, this study proposes a joint compensation method, which effectively reduces the SCB.

This study reveals that the predistortion filter breaks the constant envelope characteristic of the signal, resulting in nonlinear distortion after passing through the HPA.

To address the distortion introduced by both the filter and the power amplifier in the navigation signal transmission chain, this study proposes a joint compensation method, which effectively reduces the SCB.

What are the implications of the main findings?
This study effectively enhances navigation signal quality and provides strong support for improving the stability and reliability of high-precision positioning services.The proposed compensation method serves as a reference for optimizing the design of navigation satellite payloads and provides a technical foundation for the evolution of future navigation systems toward high-fidelity signal generation.

This study effectively enhances navigation signal quality and provides strong support for improving the stability and reliability of high-precision positioning services.

The proposed compensation method serves as a reference for optimizing the design of navigation satellite payloads and provides a technical foundation for the evolution of future navigation systems toward high-fidelity signal generation.

Navigation signals are simultaneously affected by nonlinear distortion from the high-power amplifier (HPA) and linear distortion from the filter in the navigation signal transmission channel, which reduce the signal quality and degrade the performance in high-precision positioning services. To address the limitation of traditional compensation methods under nonlinear conditions, this proposes a joint compensation approach. The approach first employs an iterative piecewise optimization method to design a predistortion filter to enhance the compensation ability for linear distortion. Then a QR-decomposition recursive least squares parameter extraction algorithm is used to extract the actual HPA model and construct a lookup table, enabling adaptive compensation of nonlinear distortion. With S-curve bias (SCB) as the performance evaluation index, the results show that this method can significantly reduce the SCB and effectively compensate for the distortion. The findings indicate that the proposed method improves navigation signal quality and provides reliable support for high-precision positioning services.