The emergence of Ambient IoT signals a paradigm shift toward massive batteryless networking. However, the absence of an agile physical layer substrate remains a fundamental barrier to research and standardization. Current testbeds are hindered by decoupled radio paths, high static power, and cumbersome control methods, which stifle rapid protocol prototyping. In this paper, we present Janus, the first hybrid active-passive configurable radio architected for agile Ambient IoT networking. Janus introduces a parameterized architecture that unifies passive and active transmission into a single RF front end, abstracting complex physical layer behaviors into concise parameters. This design enables a system-level control plane for dynamic mode transitions and an energy management plane for fine-grained harvesting across multiple sources. We implement a compact PCB prototype and evaluate its performance across diverse protocol landscapes, including 3GPP A-IoT, IEEE 802.11 AMP, and Bluetooth SIG. Our experimental results demonstrate that Janus achieves communication performance on par with dedicated radios while significantly reducing configuration overhead. Ultimately, Janus serves as a versatile enabler for validating emerging protocols and accelerating the standardization of next-generation low-power networks.

翻译：环境物联网的兴起标志着网络架构向大规模无电池化方向的范式转变。然而，敏捷物理层基底的缺失仍是制约其研究与标准化的根本障碍。现有测试平台受限于射频路径解耦、高静态功耗及繁琐的控制方法，严重阻碍了协议快速原型开发。本文提出Janus——首款面向敏捷环境物联网组网设计的混合有源-无源可配置射频架构。Janus通过参数化架构将无源与有源传输统一至单射频前端，将复杂物理层行为抽象为简洁参数。该设计同时支持系统级控制平面实现动态模式切换，以及多源能量精细采集的能量管理平面。我们实现了紧凑型PCB原型，并在多协议场景（涵盖3GPP A-IoT、IEEE 802.11 AMP及蓝牙SIG）下评估其性能。实验结果表明，Janus在达到专用射频通信性能的同时，显著降低了配置开销。最终，Janus作为多功能使能平台，为验证新兴协议并加速下一代低功耗网络标准化进程提供了关键支撑。