一种用于无源RFID的新型低压低功耗振荡器
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摘 要：采用中芯国际180 nm混合信号工艺，设计了一种新型低压低功耗环形振荡器.基于反馈理论，采用放大器完成从电源电压到环振工作电压的降压稳压转换，实现环振工作电压稳定性优化，同时降低其功耗;环振输出经幅度变换电路，实现高摆幅振荡信号输出;振荡器工作频率电流受控，抑制了电源噪声，降低了电源电压波动对输出频率的影响.结果表明，1 V电源电压下，输出频率2.737 MHz，功耗约0.8 μW，1 MHz频点处相位噪声-108.7 dB;0.9～2.1 V电压范围内，输出频率波动小于0.23%，适于无源芯片设计.
关键词：振荡器;射频识别;低电压;低功耗
中图分类号：TN495 文献标志码：A
A Novel Low-voltage Low-power Oscillator Used for Passive RFID
CHEN Diping1，YANG Cuiling1，DONG Gang1，QIN Pengju2，ZENG Jianping1
（1. College of Physics and Microelectronics Science，Hunan University，Changsha 410082，China;
2. Hunan Runtronic Microelectronics Co Ltd，Changsha 410000，China ）
Abstract：A novel low-voltage low-power ring oscillator was designed，which was implemented by an SMIC's 180 nm mixed signal processing technology. Based on the feedback theory，the regulation and conversion from supply voltage to operating voltage of ring oscillators was completed by employing an amplifier，generating superior operating voltage stability as well as lower consumption. Furthermore，a high output swing was obtained with an amplitude conversion circuit. The operating frequency of the oscillator was controlled by current，resulting in the reduced effect of oscillating signal on the supply voltage VDD and the depressed supply noise. The results demonstrate that the output frequency is 2.737 MHz，the consumption is 0.8 μW with a 1 V supply，and the phase noise at the phase point is -108.7 dB at 1 MHz offset. Meanwhile，the output frequency fluctuations are kept within 0.23% when the supply voltage varies between 0.9 V and 2.1 V，which is reasonable in passive chip design.
Key words：oscillator;radio frequency identification（RFID）;low-voltage;low-power
射頻识别（Radio Frequency Identification，RFID）是近年来备受关注的一种新兴技术，其利用无线电波快速精准地识别相关信息，广泛用于支付系统、物流、人员跟踪等领域[1-3].受限于应用场合，低电压、低功耗、宽电源电压范围、低成本等要求对射频识别系统显得尤为重要，特别在无源RFID电子标签领域.
无源RFID电子标签是一种微型装置，工作于无任何能量储存的情况下，通过对阅读器信号转换获取工作电压，整个芯片的功率只有几微瓦或者更低，因此，高效的功耗分配对于电子标签的性能评估至关重要[4-5].RFID电子标签主要分为3部分：天
线部分、模拟前端和基带处理单元[6].天线部分完成射频信号的接收与发送;模拟前端由整流电路、时钟产生电路、反射调制电路以及解调电路等组成;基带处理单元控制数据编码/解码和内存/传感器等的访问.振荡器产生的信号用于精确控制副载波频率，同时给数字电路提供工作时钟，故振荡器性能优劣直接影响整个射频识别系统的性能.
折衷功耗、面积以及成本，本文采用基于反馈理论的电源电压变换的新型环形振荡器结构，完成了一种适用于无源RFID电子标签的高稳定低压低功耗振荡器的设计，其正常工作电源电压范围为0.9～2.1 V，输出频率波动小于0.23%;1 V电源电压下，输出频率2.737 MHz，功耗约0.8 μW.
1 无源RFID标签振荡器设计要点
1.1 普通振荡器分析
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