Adaptive DSSS PN Code Tracking Loop Based on Fuzzy Logic Control Technology

In Lunar-Earth telemetry, tracking, and command (TT&C) scenarios characterized with high dynamics and extremely low carrier-to-noise ratios (CNR), direct sequence spread spectrum (DSSS) pseudo-noise (PN) code tracking loops employ traditional optimal loop design methods at present. These methods rely on dynamics and CNR estimation results, and use on-off switching mechanisms between wide and narrow tracking loop bandwidth for PN code tracking. However, they cannot adaptively adjust parameters based on received signal states, which limits further improvements in tracking accuracy, loop adaptability, and convergence speed. This paper proposes an adaptive DSSS PN code tracking loop based on fuzzy logic (FL)control. A FL controller is incorporated into the tracking loop, which uses the mean and standard deviation of the loop discriminator output as inputs to a Takagi–Sugeno (T–S) fuzzy model to compute bandwidth adjustment parameters, so adaptive loop bandwidth regulation is enabled. To reduce the noise of discrimination result in low CNR scenarios, a Maximum Likelihood Estimation(MLE) based discriminator is applied to match the FL controller. Compared to existing optimal loop designs for DSSS PN code tracking, the proposed method demonstrates enhanced loop adaptability, tracking accuracy, and convergence speed in complex Lunar-Earth TT&C scenarios. The paper provides analysis and simulations under various CNR and Doppler dynamics. Results indicate that the proposed algorithm significantly improves tracking accuracy and convergence speed while ensuring loop stability and dynamic adaptability, and shows superior performance across complex scenarios.