微瓦级无晶振无锁相环接收机关键技术研究

Recently, wearable and implantable medical devices based on Internet of Thing (IoT) applications have become extremely important in fundamental research, and are highly successful in commercialization. The main challenge in this field is that battery life is extremely limited due to power-hungry RF transceivers which consumes almost 90% of the total battery energy. Besides the severe power budget, implantable device applications in the organism also require small-size external components. So far, the off-chip quartz is usually utilized to generate the system clock, however, it faces a big problem since it typically occupies most volume of external components. ..In this proposal, we are aiming at high efficient medical devices, and we propose our research in twofold. First, we will design and explore a system architecture that shares most of its current between the sub-blocks. An ultra-low-power RF front-end will be implemented by utilizing transformer coupling technique which couples the excessive energy generated by a temperature-compensated FBAR oscillator to the RF receiver chain. The RF/IF includes several key blocks such as quasi-passive I/Q mixer, quasi-passive reconfigurable filter and PGAs. Second, a PLL-free frequency synthesizer will be implemented in the system with the same fixed frequency FBAR oscillator followed by a phase-interpolate-based fractional feedback divider. The glitches generated during the phase interpolating will be filtered by a tracking-and-holding circuit. ..The proposed strategies will be verified by a 65nm CMOS process.

设计无线智能穿戴以及植入式体征检测接收机芯片的关键之处在于超低功耗和超微型化。其中微型化设计除了芯片本身面积之外，还要求该芯片具有最少的片外元件。本课题将针对低功耗和微型化两方面开展科学研究。首先，研究能够在多个子电路模块之间共享静态或者动态电流的接收机体系架构，探索接收链路和本振链路之间变压器能量耦合设计方法，研究与设计无源阻抗变换电路、准无源正交混频器、准无源可配置滤波器以及低功耗基带可编程增益放大器等。其次，采用MEMS与CMOS协同设计方案，研究基于薄膜声体波谐振器（FBAR）的无晶振无锁相环频率综合器电路，包括FBAR谐振器/振荡器，自校准无源正交产生器等，提出一种基于电流模DAC相位插值器的分数反馈分频器。研究分数分频过程中分数杂散抑制以及相位突变过程中信号毛刺滤除问题等。最后通过65nm CMOS工艺流片验证本课题所提出的设计理论和方法。

基于传统集成电路（CMOS）与微机电系统（MEMS）无缝融合的无线传感系统是后摩尔时代异质集成电路技术的发展衍生出的新兴领域。本项目针对无线智能穿戴以及植入式体征检测射频接收机中功耗和体积瓶颈问题，基于CMOS和MEMS协同设计技术，从接收机系统架构和电路理论两个层面开展了创新性的研究。研究了能够在多个子模块之间共享静态（动态）电流的射频接收机体系架构，探索了接收链路和本振链路之间变压器能量耦合设计方法，提出了基于薄膜声体波谐振器（FBAR）的无锁相环射频接收机架构及其频率规划。针对低功耗的指标要求，提出了准无源正交混频、准无源镜像抑制滤波、电流复用等电路设计技术，并将其应用于三种低功耗射频接收机的接收链路的设计，芯片测试结果均达到微瓦级的指标要求。针对微型化的指标要求，研究并设计了基于FBAR谐振器的无锁相环频率合成电路，提出一种基于电流模相位插值器的分数反馈分频器，解决了分数分频过程中分数杂散抑制以及相位突变过程中信号毛刺滤除问题。同时面向实际应用，研究了基于FBAR谐振器的频率源芯片设计技术，研究实现了一种具有低功耗低相噪的四阶皮尔斯FBAR振荡器，有效解决了AM-PM调制效应导致的近偏频噪声恶化的问题。设计了一种低功耗高精度温度传感器，为了提高测温前端电路的精度，采用了斩波运算放大器、βF补偿电路和动态匹配等技术降低工艺非理想因素带来的误差。本项目提出的低功耗电路理论和设计方法能够推动CMOS/MEMS协同设计技术在无线生物医疗及物联网领域的应用，为后摩尔时代异质/异构集成技术在电路设计层面的进一步发展提供技术支撑。

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