Department of Applied Metrology, Institute of Electrical Information Technology, TU Clausthal, Clausthal-Zellerfeld, Germany.
Sci Rep. 2023 May 26;13(1):8570. doi: 10.1038/s41598-023-35000-2.
Digitization of phase-modulated carrier signals with a commercially available analog-to-digital converter (ADC) is a common task in many communication and sensor applications. ADCs deliver phase-modulated digital carrier signals, which are numerically demodulated in order to extract the relevant information. However, the limited dynamic ranges of available ADCs limit the carrier-to-noise ratio of carrier signals after digitization. Correspondingly, the resolution of the demodulated digital signal is degraded. We demonstrate a sampling method with a simple demodulation scheme for phase-modulated signals with a small modulation index. Our new scheme overcomes the limitation due to digital noise defined by the ADC. Through simulations and experiments, we provide evidence that our method can improve the resolution of the demodulated digital signal significantly, when the carrier-to-noise ratio of phase-modulated signals is limited by digital noise. We employ our sampling and demodulation scheme to solve the problem of a possible degradation of measurement resolution after digital demodulation in heterodyne interferometers measuring small vibration amplitudes.
使用市售的模数转换器 (ADC) 对调相信号进行数字化是许多通信和传感器应用中的常见任务。ADC 会输出调相信号的数字载波信号，然后对这些信号进行数值解调，以提取相关信息。然而，可用 ADC 的动态范围有限，这会限制数字化后载波信号的载噪比。相应地，解调后的数字信号的分辨率会降低。我们提出了一种适用于小调制指数的调相信号的简单解调方案的采样方法。我们的新方案克服了由 ADC 定义的数字噪声的限制。通过仿真和实验，我们证明了在调相信号的载噪比受到数字噪声限制的情况下，我们的方法可以显著提高解调后的数字信号的分辨率。我们采用我们的采样和解调方案来解决在测量小振动幅度的外差干涉仪中进行数字解调后可能导致的测量分辨率降低的问题。
