调幅式电容位移传感器开关检波电路设计

Design of switch detecting circuit for AM capacitive displacement sensor

针对调幅式电容位移传感器乘法器检波存在的速度慢、功耗大和热噪声大问题,设计了一种基于模拟开关的全波检波电路。首先,对开关全波检波和开关半波检波原理进行分析,根据分析结果选择了全波检波方法。在此基础上,完成开关全波检波电路设计与测量系统其它部分设计。最后,利用八位半数字表3458A对检波电路与测量系统性能指标进行测试。测试结果表明：检波电路可以实现0.1 m V的分辨率,测量系统在150~650μm范围内分辨率达30 nm,系统示值稳定性0.1 m V/30 min,电容测量系统最大测量偏差为20 nm。该测量系统满足电容测微系统稳定性好、准确性高的要求。

Aiming at problem of amplitude modulation（ AM） capacitive displacement sensor multiplier low detecting speed,large power consumption and big thermal noise,a full-wave detecting circuit based on analog switch is designed. Firstly,analyze principle of switch full-wave detection and switch half-wave detecting,according to analysis result,full-wave detecting method is chosen. On this basis,design of switch full-wave detecting circuit and other parts of measuring system are completed. Finally,by using eight and a half bit digital multimeter 3458 A,performance index of detecting circuit and measurement system are tested. Test results show that detecting circuit can realize resolution of 0. 1m V,resolution of system in the range of 150 ~ 650 μm is 30 nm,the maximum deviation of measurement system is 20 nm,stability of showing value is 0. 1 m V /30 min. The measuring system meets requirements of good stability and high accuracy for capacitance measurement microsystem.