DQPSK Signal Modulation and Demodulation Implementation

In this paper, we provide a comprehensive implementation of DQPSK signal modulation and demodulation, accompanied by detailed MATLAB simulation results. We begin by explaining the fundamental principles and step-by-step procedures of DQPSK signal modulation, covering both the differential encoding process and phase modulation techniques. The implementation utilizes MATLAB's signal processing capabilities, where we demonstrate key functions such as dpskmod() and dpskdemod() for modulation/demodulation operations, and awgn() function for simulating different signal-to-noise ratio conditions. We present complete code examples showing how to generate DQPSK symbols, implement differential encoding, and perform coherent detection. The simulation results compare system performance under various SNR conditions, analyzing bit error rate (BER) characteristics using error rate calculation functions. Finally, we summarize the experimental outcomes and discuss potential enhancements including optimization of decision thresholds, implementation of carrier recovery algorithms, and extension to higher-order modulation schemes.