In a study published in Sensors, a research group led by Prof. WANG Zhi from the Changchun Institute of Optics, Fine Mechanics and Physics of the Chinese Academy of Sciences, studied a high-precision resonant capacitive bridge circuit designed for gravitational reference sensors. This circuit significantly reduces capacitive noise in the capacitive sensing system, thereby enhancing sensor performance and the accuracy of gravitational wave detection.

Gravitational wave detection is a cutting-edge field in modern physics and is of great significance for understanding the origin and evolution of the universe. As the inertial reference system for space gravitational wave observatories, the gravitational reference sensor is the core device for detecting gravitational waves. These sensors need to have high sensitivity and precision to achieve a residual acceleration noise level better than 3×10^-15 ms^-2 Hz^-1/2 in the frequency range of 0.1mHz to 1Hz.

To meet these stringent noise requirements, the capacitive noise of the capacitive sensing system needs to be lower than 1aF/Hz^1/2. To this end, the research team utilized weak signal detection methods and analog circuit design techniques to develop the low-capacitive noise resonant capacitive bridge circuit.

The circuit is primarily composed of a differential transformer and transimpedance amplifiers, which can effectively amplify the current signal that characterizes the position information of the measured object and convert it into a voltage signal. Researchers have analyzed and tested this scheme, and the results indicate that the resonance frequency of the circuit, transformer parameters, and amplifier noise have a significant impact on the circuit’s noise performance.

To further reduce the capacitive noise of this scheme, the researchers studied the resonance frequency adjustment and verification methods, developed high-performance transformers, and designed discrete transimpedance amplifiers. This improved the overall performance of the circuit, and the capacitive noise of the sensing system in the low-frequency range of 10mHz to 1Hz reached only 0.84 aF/Hz^1/2.

The successful development of this high-performance resonant bridge circuit not only meets the noise requirements of the capacitive sensing system in the low-frequency range but also has laid the foundation for the development of future gravitational wave detection technology.

WANG Zhi   wangzhi@ciomp.ac.cn