Analysis of a Capacitive Sensing Circuit and Sensitive Structure Based on a Low-Temperature-Drift Planar Transformer

In space gravitational-wave-detection missions, inertial sensors are used as the core loads, and their acceleration noise needs to reach [Formula: see text] at a frequency of [Formula: see text] , which corresponds to the capacitive sensing system; the capacitive sensing noise on the sensitive axis needs to reach [Formula: see text]. Unlike traditional circuit noise evaluation, the noise in the [Formula: see text] frequency band is dominated by the thermal noise and the [Formula: see text] 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 [Formula: see text] noise. For closed-loop measurements of capacitive sensing circuits and sensitive structures, the minimum capacitive resolution in the time domain is about [Formula: see text] , which is far lower than the scientific measurement resolution requirement of [Formula: see text] for gravitational wave detection. The capacitive sensing noise is converted to [Formula: see text] in the frequency band of [Formula: see text]. 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.