Modeling and analysis of the noise performance of the capacitive sensing circuit with a differential transformer

TY - JOUR

T1 - Modeling and analysis of the noise performance of the capacitive sensing circuit with a differential transformer

AU - Xie, Yafei

AU - Fan, Ji

AU - Zhao, Chun

AU - Yan, Shitao

AU - Hu, Chenyuan

AU - Tu, Liangcheng

N1 - Funding Information: Funding: This research was partially supported by the National Key Research and Development Program of China (grant number 2017YFC0601603), the Natural Science Foundation of China (grant numbers 41874089 and 61871439), and the China Postdoctoral Science Foundation funded project (grant number 2018M630854). Publisher Copyright: © 2019 by the authors.

PY - 2019/5/15

Y1 - 2019/5/15

N2 - Capacitive sensing is a key technique to measure the test mass movement with a high resolution for space-borne gravitational wave detectors, such as Laser Interferometer Space Antenna (LISA) and TianQin. The capacitance resolution requirement of TianQin is higher than that of LISA, as the arm length of TianQin is about 15 times shorter. In this paper, the transfer function and capacitance measurement noise of the circuit are modeled and analyzed. Figure-of-merits, including the product of the inductance L and the quality factor Q of the transformer, are proposed to optimize the transformer and the capacitance measurement resolution of the circuit. The LQ product improvement and the resonant frequency augmentation are the key factors to enhance the capacitance measurement resolution. We fabricated a transformer with a high LQ product over a wide frequency band. The evaluation showed that the transformer can generate a capacitance resolution of 0.11 aF/Hz1/2 at a resonant frequency of 200 kHz, and the amplitude of the injection wave would be 0.6 V. This result supports the potential application of the proposed transformer in space-borne gravitational wave detection and demonstrates that it could relieve the stringent requirements for other parameters in the TianQin mission.

AB - Capacitive sensing is a key technique to measure the test mass movement with a high resolution for space-borne gravitational wave detectors, such as Laser Interferometer Space Antenna (LISA) and TianQin. The capacitance resolution requirement of TianQin is higher than that of LISA, as the arm length of TianQin is about 15 times shorter. In this paper, the transfer function and capacitance measurement noise of the circuit are modeled and analyzed. Figure-of-merits, including the product of the inductance L and the quality factor Q of the transformer, are proposed to optimize the transformer and the capacitance measurement resolution of the circuit. The LQ product improvement and the resonant frequency augmentation are the key factors to enhance the capacitance measurement resolution. We fabricated a transformer with a high LQ product over a wide frequency band. The evaluation showed that the transformer can generate a capacitance resolution of 0.11 aF/Hz1/2 at a resonant frequency of 200 kHz, and the amplitude of the injection wave would be 0.6 V. This result supports the potential application of the proposed transformer in space-borne gravitational wave detection and demonstrates that it could relieve the stringent requirements for other parameters in the TianQin mission.

KW - Capacitive sensing

KW - Differential transformer

KW - Low noise circuit

KW - LQ product

KW - Resonant frequency

UR - http://www.scopus.com/inward/record.url?scp=85073754856&partnerID=8YFLogxK

U2 - 10.3390/mi10050325

DO - 10.3390/mi10050325

M3 - Article

AN - SCOPUS:85073754856

VL - 10

JO - Micromachines

JF - Micromachines

IS - 5

M1 - 325

ER -