Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China.
School of Electronic Information Engineering, Changchun University of Science and Technology, Changchun 130022, China.
Sensors (Basel). 2022 Nov 29;22(23):9284. doi: 10.3390/s22239284.
In space gravitational-wave-detection missions, inertial sensors are used as the core loads, and their acceleration noise needs to reach 3×10−15 ms−2/Hz at a frequency of 0.1 mHz, which corresponds to the capacitive sensing system; the capacitive sensing noise on the sensitive axis needs to reach 1 aF/Hz. Unlike traditional circuit noise evaluation, the noise in the mHz frequency band is dominated by the thermal noise and the 1/f noise of the device, which is a challenging technical goal. In this paper, a low-frequency, high-precision resonant capacitor bridge method based on a planar transformer is used. Compared with the traditional winding transformer, the developed planar transformer has the advantages of low temperature drift and low 1/f noise. For closed-loop measurements of capacitive sensing circuits and sensitive structures, the minimum capacitive resolution in the time domain is about 3 aF, which is far lower than the scientific measurement resolution requirement of 5.8 fF for gravitational wave detection. The capacitive sensing noise is converted to 1.095 aF/Hz in the frequency band of 10 mHz−1 Hz. Although there is a gap between the closed-loop measurement results and the final index, the measurement environment is an experimental condition without temperature control on the ground; additionally, in China, the measurement integrity and actual measurement results of the capacitive sensing function have reached a domestic leading level. This is the realization of China’s future space gravitational wave exploration.
在空间引力波探测任务中，惯性传感器作为核心负载，其加速度噪声需在 0.1 mHz 频率处达到 3×10−15 ms−2/Hz，这对应于电容传感系统；灵敏轴上的电容传感噪声需要达到 1 aF/Hz。与传统的电路噪声评估不同，在 mHz 频带内的噪声主要由器件的热噪声和 1/f 噪声主导，这是一个具有挑战性的技术目标。本文采用基于平面变压器的低频、高精度谐振电容桥方法。与传统的绕组变压器相比，所开发的平面变压器具有低温漂和低 1/f 噪声的优点。对于电容传感电路和灵敏结构的闭环测量，时域中的最小电容分辨率约为 3 aF，远低于引力波探测的科学测量分辨率要求 5.8 fF。电容传感噪声在 10 mHz-1 Hz 的频段内转换为 1.095 aF/Hz。虽然闭环测量结果与最终指标之间存在差距，但测量环境是在地面上没有温度控制的实验条件；此外，在中国，电容传感功能的测量完整性和实际测量结果已达到国内领先水平。这是中国未来空间引力波探测的实现。
