基于低压低功耗的电流模预处理锁相环数字反馈检测方法研究

With the need of the weak signal detecting microsystem, the requirement of the high accuracy performance in the low voltage and low power circuits or systems is increasing. However, with the requirement of the low voltage and power, the performance of the distortion of the conventional systems are becoming poor. The idea of the project, inspired by the choice of the frequency bands, presents the approach of the analog signal preprocessing, which is able to improve the preformance of the distortion while maintaining the characteristics of digital programming. Furthermore, on the basic of this methodology, the approach of the current mode preprocessing and PLL digital feedabck detection is proposed, in order to further optimize the system accuracy with the requirement of the low voltage and low power. Simultaneously, the methodologies of the digital compensation and self-calibration are also presented, so as to achieve the improvement of the system noise and integration. The feasibility of the detection idea is initially verified by the simulation of the elementary system model. In conclusion, the detection idea is expected to lay the base of the performances' optimization in the weak signal detection system.

微弱信号检测系统的微型化等应用需求使得其对系统电路在低压低功耗下保持高精度等性能方面提出越来越高的要求，而传统的信号检测处理方法（如：脉宽调制，连续信号和模数互换）在低压低功耗的要求提高的情况下，系统电路的失真愈发严重。本项目力图从信号频段选择方式着手，首先从系统结构上提出模拟信号预处理检测方法代替模数互换方法，以此在保留数字可编程滤波特点的同时减小系统非线性失真；进而以模拟信号预处理系统结构为基础，提出电流模信号预处理锁相环数字反馈检测方法，用以在极低电源电压条件下对系统精度进一步的优化；同时在此系统电路结构基础上提出数字补偿和自校准算法，达到减小系统噪声和提高系统集成度的目的。此检测方法的可行性通过对初步系统模型的仿真得到初步的验证。综上所述，此检测方法有望为微弱信号检测系统在极低电源电压下的各方面性能优化奠定基础。

本项目针对医疗微弱信号检测，建立了一套完整的基于电流模信号预处理锁相环数字反馈的医疗微弱信号检测系统，优化与仿真方法。项目相应得到的系统芯片由电荷泵电路模块，前端读出电路模块，纹波相消锁相环模块和PWM数字转换器和D/A转换器构成。其解决了传统方法在极低电源电压下的失真和功耗问题。通过测试验证，系统达到了研究目标的要求：即.18μm 工艺，0.5V电源电压下和输入信号为1kHz下，实现THD为-71dB@200mVp-p,而等效输入信号分辨率为3.5μV，功耗为14μW 。与此同时，项目实现了系统在（100~10kHz)范围内的可编程电流模预处理。综上所述，通过此项目的执行，此检测方法可被证明对生物医疗传感器检测系统的功耗和精度优化起到重要作用。