This paper presents a quad-band, 3D mountable rectenna module for ambient energy harvesting. With the aim of powering up Internet of Things (IoT) nodes in practical ambient environments, a hybrid approach of combining power, both at RF and DC, is adopted using 98 MHz FM band, GSM900 (Global System for Mobile Communications), GSM1800, and Wi-Fi 2.4 GHz band. A dual polarized cross-dipole antenna featuring asymmetric slots as well as central ring structure enables multiband response and improved matching at the higher three frequency bands, whereas a loaded monopole wire antenna is used at the lower FM band. Four identical multiband antennas are placed in a 3D cubic arrangement that houses a 4-to-1 power combiner and matching circuits on the inside and the FM antenna on the top. In order to maintain stable rectenna output at varying input power levels and load resistances, a novel transmission line based matching network using closed form equations is proposed. Integrated in form of a 10 × 10 × 10  cube using standard FR4 substrate, the rectenna generates a peak output voltage of 2.38 V at −10 dBm input power. The RF to DC conversion efficiency is 70.28%, 41.7%, 33.37%, and 27.69% at 98 MHz, 0.9 GHz, 1.8 GHz, and 2.4 GHz, respectively, at −6 dBm. The rectenna also exhibits a measured conversion efficiency of 31.3% at −15 dBm for multitone inputs in ambient environment. The promising results in both indoor and outdoor settings are suitable to power low power IoT devices.

中文翻译：

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四频带3D Rectenna阵列，用于环境RF能量收集

本文提出了一种用于环境能量收集的四频，3D可安装整流天线模块。为了在实际的环境中为物联网（IoT）节点供电，采用了一种混合方式，即使用98 MHz FM频段，GSM900（全球移动通信系统），GSM1800，和Wi-Fi 2.4 GHz频段。具有非对称缝隙和中心环形结构的双极化交叉偶极天线具有较高的三个频段的多频带响应和更好的匹配性，而较低的FM频段则使用了负载的单极线天线。四个相同的多频带天线以3D立方布置放置，内部装有4对1功率组合器和匹配电路，顶部装有FM天线。为了在变化的输入功率水平和负载电阻下保持稳定的整流天线输出，提出了一种使用闭合形式方程的新型基于传输线的匹配网络。以10×10×10的形式集成 在使用标准FR4基板的立方体中，整流天线在-10 dBm输入功率下产生2.38 V的峰值输出电压。在-6 dBm时，在98 MHz，0.9 GHz，1.8 GHz和2.4 GHz时，RF到DC的转换效率分别为70.28％，41.7％，33.37％和27.69％。对于周围环境中的多音输入，该整流天线在-15 dBm时也表现出31.3％的转换效率。在室内和室外环境下都可取得令人满意的结果，适合为低功耗物联网设备供电。