低功耗自适应极简人体通信收发机

The bio-medical signals such as ECG and EEG, once collected by the human body health monitoring system, can be transmitted via the human body to the wearable mobile devices, such as smart watch. This is considered as convenient and secure communication method without wire and antenna, and has become one of the IEEE body area network standard. The keys of designing this human body transceiver are, however, to tackle the issues of long-time continuous work, the compactivity of the individual human difference, and the minuature of the circuit. Hence, this proposal is to study an ultra-low power, ultra-simple, fully integrated transceiver with good universality used for human body communication. First, we study the properties of the human body channel, and determine the best frequency band for the human body communication. Then, we study the PLL-based transceiver, and build a multi-mode communication mechanism including both transmitter and receiver. Using only one PLL circuit, and quickly switching between the modes of modulation, demodulation and calibration, this method allows for the realization of multi-function of the signal transmission / signal reception and clock calibration. As a result the compact circuit structure and low power targets can be achieved. Also we will study the on-chip integrated negative-feedback oscillator, build the auto-compensation mechanism of the frequency, so as to remove the huge off-chip crystal device and to obtain the higher integration. Finally, we study the method to remove the individual difference, and propose an active non-coherent method to detect the human body impedance, and a method of digital adjustment of the circuit gain, so as to reduce the signal distortion.

人体健康监测所采集到的心电脑电等体征信号，以身体为媒介传输到随身穿戴的便携设备如智能手表上，是无导线、无天线、零束缚的安全通信方式，已成为IEEE BAN体域网的通信标准之一。实现这种人体通信收发机的关键是解决长时间工作、兼容个体差异以及电路微型化的问题。由此，本项目拟研究一种超低功耗、电路形态极简、人体阻抗通用性好、全集成的人体通信收发机电路。首先研究人体信道特性，确定人体通信的最佳频段。然后研究基于锁相环的极简收发机电路，建立收发一体的多模通信方式，仅靠一套锁相环电路分别工作在调制、解调、校准等模式并快速切换，实现信号接收、发送和频率校准的三合一复用，达到精简电路和超低功耗目的；同时研究片上集成负反馈振荡器，建立时钟频率自补偿机制，以省去臃肿的片外晶振元件、提高集成度。最后，研究消除人体差异的方法，提出人体阻抗的非相干有源探测和数字增益调节方法，以适应个体差异、减小信号失真度。

本项目研究的人体通信收发机具有低功耗、电路结构简单等优点，特别适合于便携移动设备间的通信。我们提出一种基于锁相环电路实现的人体通信收发机电路，通过人体试验确定了合适的人体信道最佳频段为40MHz，建立了人体通信信道模型。在此基础上设计了收发一体的锁相环电路，可工作在调制、解调、校准等模式并快速切换，实现信号接收、发送和频率校准的三合一复用。锁相环电路包括鉴频鉴相器、压控振荡器、分频器、电荷泵等电路。芯片流片后测试可实现数据收发功能，数据率达到5Mbps，满足目标要求。为了进一步提高集成度，减小电路尺寸，我们还研究并设计了在芯片上集成时钟电路，我们提出一种正负温度系数抵消的方法，用环形振荡器实现了较好的温度特性，且芯片面积仅0.08平方毫米。此外我们研究并设计了人体阻抗检测电路，采用二级放大方式，电路具有稳定的输出电流，输出阻抗达到了1M欧姆。