Simulink Modeling and Simulation of Classic Costas Loop Carrier Tracking System

In the Simulink modeling and simulation of the classic Costas loop carrier tracking system, we implement QPSK modulation with comprehensive signal processing components. The model incorporates key functional blocks including up-conversion and down-conversion modules, along with three different phase detection methodologies for performance comparison. The simulation architecture employs MATLAB function blocks to implement the phase detector algorithms, where each method calculates phase error using distinct mathematical approaches: product-based detection, cross-product discrimination, and decision-directed phase estimation. Through this simulation model, engineers can analyze the Costas loop's behavioral characteristics under various phase detection schemes, observing critical parameters such as phase error variance, lock-in range, and tracking accuracy. The simulation environment allows for real-time parameter tuning of loop filter coefficients and VCO gain settings, enabling comprehensive performance evaluation. Such simulation experiments provide valuable insights for optimizing carrier tracking loop design, ultimately enhancing system performance and stability in digital communication applications.