面向物联网应用的超低功耗 IM3 反向散射无源传感系统

黄瑞杨; 武鹏德

doi:10.11999/JEIT250787

面向物联网应用的超低功耗 IM3 反向散射无源传感系统

doi: 10.11999/JEIT250787 cstr: 32379.14.JEIT250787

杭州电子科技大学电子信息学院杭州 310018

详细信息

作者简介:
黄瑞杨：男，硕士生，研究方向为射频无线能量与数据协同传输

武鹏德：男，副教授，硕士生导师，研究方向为天线设计、无线能量与数据协同传输、面向植入设备的超低功耗通信，可穿戴和植入式无线传感技术等

中图分类号: TN836
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出版历程
- 修回日期: 2025-12-01
- 录用日期: 2025-12-01
- 网络出版日期: 2025-12-09

Ultra-Low-Power IM3 Backscatter Passive Sensing System for IoT Applications

College of Electronics and Information Engineering, Hangzhou Dianzi University, Hangzhou 310018, China

摘要

摘要: 传统反向散射通信无法同步实现射频能量收集与传感信息读出，而有源标签的传感信息回传存在较高通信能耗。该文提出一种新颖的三阶互调(IM3)反向散射式无源传感系统，可在不影响射频能量收集效率的前提下实现传感信息低功耗读出。该文研究了整流电路中反向散射IM3产生机制，通过差频嵌入阻抗调控IM3信号转换效率，传感信息控制嵌入阻抗谐振频率变化，将传感信息映射到IM3信号强度凹陷点变化上，查询器通过扫描该凹陷点反演传感信息。实验结果表明，该系统能准确读取传感信息，能量转换效率仅比纯整流模式下降约5个百分点；在1米无线传输距离下，反向散射IM3信号反演的传感电压与直接测量值误差小于5%，为解决同步能量收集与模拟量读出、低功耗信息传输问题提供了新方法。
- 无源传感 /
- 无线数据和能量协同传输 /
- 射频能量收集 /
- 低功耗 /
- 三阶互调(IM3)
Abstract: Objective With the advancement of wireless communication and electronic manufacturing, the Internet of Things (IoT) has progressed remarkably, healthcare, agriculture, logistics, and other fields. The exponential growth of IoT devices brings significant challenges: billions of devices demand enormous cumulative energy, and traditional battery-powered devices require frequent charging, increasing operational costs and exacerbating electronic waste. Thus, innovative energy-saving solutions are crucial for IoT’s sustainable development. Core strategies to address energy and lifecycle constraints involve enhancing energy supply and reducing device power consumption. Energy harvesting (EH) technology enables devices to collect and store solar, thermal, kinetic, and radio frequency (RF) energy for Ambient IoT (AmIoT) applications. However, existing EH technologies have limitations: conventional IoT devices (especially active RF components) consume high power, and insufficient EH efficiency may hinder real-time data transmission. To tackle these issues, this paper proposes a novel IM3 backscatter passive sensing system for direct analog sensing transmission without compromising RF energy harvesting efficiency. Methods The third-order intermodulation (IM3) signal is a nonlinear distortion product generated when two fundamental frequency tones are processed by nonlinear devices (e.g., transistors, diodes) in communication systems, with frequencies of 2f₁-f₂ and 2f₂-f₁. The core innovation of this work is establishing a controllable functional relationship between sensor information and IM3 signal frequencies, enabling information encoding via IM3 frequencies. A key regulatory component is an embedded impedance module—designed as a parallel resonant tank with resistors, inductors, and capacitors—integrated into the rectifier circuit. Tuning the tank’s resonant frequency selectively adjusts the conversion efficiency from fundamental tones to IM3 signals: aligning with a target IM3 frequency introduces a high-impedance load, reducing that IM3 component’s efficiency, while other IM3 signals remain unaffected. Sensor information dynamically adjusts the module’s resonant frequency by converting the information into a DC voltage applied to a voltage-controlled varactor. By linking sensor information to impedance states, impedance states to IM3 conversion efficiency, and IM3 frequency characteristics to sensor information, the system achieves novel passive sensing. Results and Discussions A rectifying transmitter operating in the UHF 900 MHz band was designed and fabricated (Fig. 8). One signal source was fixed at 910.5 MHz, and the other cyclically scanned 917–920 MHz, generating IM3 signals in the 923.5–929.5 MHz range. Both sources had an output power of 0 dBm, with DC voltage as the transmitted sensor information. Experimental results show a power trough in the backscattered IM3 spectrum; as the DC voltage varies 0–5 V, the trough position shifts accordingly (Fig. 9), with an attenuation of over 10 dB throughout, ensuring good resolution (related to the varactor diode’s capacitance ratio). Additionally, the embedded impedance module has little impact on RF-DC efficiency (Fig. 10): at fixed DC voltage, efficiency decreases by 5 basis points at the modulation frequency, independent of input power; under fixed input power, different sampled voltages cause ～5 basis points efficiency reduction at different frequencies. These results confirm the rectifier circuit’s stable efficiency, meeting low-power data transmission requirements. Conclusions This paper proposes a novel passive sensing system based on backscattered third-order intermodulation (IM3) signals, enabling simultaneous efficient radio frequency (RF) energy harvesting and sensing readout. It reveals the regulation mechanism between difference-frequency embedded impedance module and backscattered IM3 intensity. Controlled by sensing information, the module correlates sensing data with IM3 intensity for passive readout. Experimental results show the embedded impedance reduces target frequency IM3 intensity by over 10 dB and the RF-DC efficiency decreases by only 5 percentage points during readout. The microwave anechoic chamber tests confirm the error between IM3-parsed bias voltage and measured value is stably within 5%, indicating good stability. This system breaks the coordinated energy-information transmission bottleneck, providing battery-free communication for passive sensor nodes. It extends device lifespan and reduces maintenance costs in ultra-low-power scenarios like wireless sensor networks and implantable medical devices, with significant engineering application value.
- Passive sensing /
- Simultaneous Wireless Information and Power Transfer(SWIPT) /
- RF Energy harvesting /
- Low-power /
- the Third Order Intermodulation(IM3)

HTML全文

图 1 RF WPT系统概况

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图 2 本文提出的基于IM3信号无源传感系统传感端模型

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图 3 系统传感端中IM3信号分量的产生过程

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图 4 辅助过程中第二次频率转换的交流等效模型

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图 5 本文提出的基于IM3信号无源传感系统的传感端电路原理图

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图 6 嵌入阻抗在差频$ {\omega }_{\Delta } $处的等效模型

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图 7 嵌入阻抗$ {Z}_{{{\omega }_{\Delta }}}\left(V\right) $随差分频率$ {\omega }_{\Delta } $的变化情况

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图 8 电路测试实验环境

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图 9 本文设计的基于IM3信号无源传感系统传感端在不同偏置电压下的反向散射的IM3信号强度变化情况

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图 10 不同输入功率与偏置电压情况下传感信息读出对RF-DC效率的影响

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图 11 空间测试实验环境

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图 12 空间测试实验结果

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表 1 $ {Z}_{{{\omega }_{\Delta }}}\left(V\right) $与反向散射的IM3信号强度关系的仿真结果(两输入信号功率均为0 dBm)

光标	二极管上的基波电压 (V)	嵌入阻抗$ {Z}_{{{\omega }_{\Delta }}}\left(V\right) $ (Ω)	$ {V}_{\text{j,}{{\omega }_{\Delta }}} $ (V)	$ {I}_{\text{IM3,MC}}+{I}_{\text{IM3,AC}} $ (10^–5A)
M1	$ \begin{matrix}{\omega }_{1}=1.11\angle -0.78{^{\circ}}\\ {\omega }_{2}=1.11\angle 0.12{^{\circ}}\\ \end{matrix} $	$ 4.87+j49.13 $	$ 0.03\angle -78.33{^{\circ}} $	$ 4.52\angle -135.45{^{\circ}} $
M2(谐振点)		$ 500 $	$ 0.40\angle -0.97{^{\circ}} $	$ 0.21\angle -116.17{^{\circ}} $
M3		$ 70.91-j174.43 $	$ 0.09\angle -18.44{^{\circ}} $	$ 3.98\angle -132.66{^{\circ}} $

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