超低功耗唤醒电路关键技术研究

Wake-up circuits (including wireless wake-up receivers, timer-based wake-up circuits, etc.) are widely used in energy-constrained IoT systems, such as wireless sensor nodes, active/semi-active RFID and body area network. For wireless wake-up receivers, the received signal strength varies in a wide range in real applications. However, most of existing researches neglect this feature, leading to energy waste. The accuracy and power consumption of timer-based wake-up circuits are mainly affected by the oscillator performance. Most of the present researches use two types of resistors with opposite temperature characteristics, which are connected in series, to achieve temperature compensation in low power oscillator design. However, the performance degrades in extreme temperature regions. This project aims to make breakthroughs in the techniques of low power high sensitivity wake-up receiver and low power high accuracy oscillator for timer-based wake-up circuits. We study energy saving methods that reduce the operational period of modules in the wake-up receiver to the most degree. An on-demand multi-stage wake-up scheme is proposed based on weighing the received signal strength. The energy-saving techniques, such as dual-mode and duty cycling mode, are also investigated comprehensively. Finally, a multi-stage wake-up based wake-up receiver with dual-mode and duty cycling techniques is developed. Great temperature compensation can be achieved in different temperature regions by changing the temperature compensation resistance ratio. Based on the above mechanism and temperature sensing, we explores the adaptive temperature compensation technology for low power high accuracy relaxation oscillator. The stability of clock frequency is improved, and the operational temperature range is extended.

唤醒电路（包括无线电唤醒接收机、定时唤醒电路等）广泛应用于无线传感器网络、有源/半有源射频识别、体域网等物联网系统。在实际应用中，无线电唤醒接收机的接收信号强度常在大范围内变化，而现有研究大多忽视了该特点，导致能量浪费；定时唤醒电路中低功耗振荡器普遍采用两种温度特性相反的电阻叠加实现温度补偿，其在极端温度下温度补偿效果恶化。本项目旨在突破低功耗高灵敏度无线电唤醒接收机、定时唤醒电路中低功耗高精度振荡器的机理与设计方法。针对唤醒接收机的应用特点，探讨最大化缩减其各模块工作时间的节能方法，建立基于接收信号强度检测的按需多级唤醒机制；研究双模式、间歇式节能技术，发展出融合多级唤醒、双模式、间歇式等节能机制的低功耗高灵敏度无线电唤醒接收机技术；利用调整温补电阻比例可分别在多个温度区域实现良好温度补偿的特性，探索基于温度感知自适应温度补偿的低功耗高精度松弛振荡器技术，提高频率精度，扩展工作温度范围。

课题组针对低功耗无线电唤醒接收机与定时唤醒电路关键技术开展了深入研究，发展出新型振荡器工艺与温度补偿机制、无需校准的低功耗高精度振荡器结构、低功耗无线电唤醒接收机架构以及分频器、低噪声放大器、混频器等多种新型射频模拟电路设计技术，完成了相关芯片的设计与流片加工。课题组共发表论文16篇，其中SCI论文11篇（中科院二区期刊论文4篇），申请发明专利2项，培养研究生9名。超额完成了项目计划书中制定的研究目标任务。主要研究成果如下：.（1）研究了基于包络检波的无线电唤醒接收机架构，探索了增大射频前端阻抗匹配网络无源电压增益、提升包络检波驱动能力、降低各模块功耗等设计方法，提出了电压/电流基准源、比较器、分频器等模拟电路的一系列新型电路结构与低功耗设计技术，基于0.18um CMOS工艺完成了唤醒接收机芯片的设计、仿真与流片，验证了本项目提出的设计方法的有效性。.（2）低噪声放大器与混频器对于接收机噪声系数影响极大。课题组针对低噪声混频器和低噪放开展了一系列研究，提出了一种具有有源合路器反馈的宽带差分LNTA，其通过利用有源合路器反馈和互补多门控晶体管(MGTR)配置，同时补偿了器件的二阶和三阶非线性，实现了高线性度、低噪声、高驱动能力等优点。另外，课题组基于电流复用技术与噪声消除跨导技术提出了多种高性能宽带混频器、低噪放的新型电路结构。.（3）定时唤醒电路的核心模块是振荡器，如何在超低功耗下同时获得宽工作温度范围、低温度系数与高频率精度是一大技术挑战。课题组深入分析了松弛振荡器电路参数、非理想因素、工作温度与时钟频率之间的关系，研究了针对不同温度区域的频率温度补偿电路，发展出了一种基于温度感知的自适应频率温度补偿方法及电路结构。此外，课题组还发展出了一种无需校准的新型高精度低功耗松弛振荡器电路结构。.本项目的研究成果对于无线传感器、射频识别、植入式芯片、可穿戴设备等领域的低功耗芯片设计具有较高的科学意义和工程价值。