Enhanced Imbalance-Distortion Mitigation and Noise Suppression in I/Q-Based Phase Demodulation Systems

In advanced sensor system designs, one of the common methods involves converting target physical quantities into phase-/frequency-modulated signals (PM/FM signal). Then, the in-phase/quadrature-phase (I/Q)-based phase demodulation structure is mainly employed to enhance flexibility and efficiency in obtaining the phase information. However, the presence of I/Q imbalance and additive noise in analog I/Q channels greatly degrade the overall system detection performance. Specifically, we investigated the detailed degradation of signal detection, including the introduction of unwanted interference frequency components, elevated noise floor, and distortion of the target signal. To solve this problem, we proposed a novel-controlled-carrier closed-loop structure to realize the phase demodulation. This structure, built upon the zero-error closed-loop structure, further mitigates the imbalance distortion and optimizes the noise performance by modifying the control method. The detailed structure and key issues are provided. Further, the effectiveness and enhanced performance of the proposed structure are verified by simulation and experiments. The experimental results align with the simulations and it shows that the proposed structure can achieve enhanced imbalance-distortion mitigation and noise suppression without the need for complex I/Q estimation and compensation.