This paper presents systematic description of the design, implementation and experimental evaluation of an RF energy harvesting platform that has been tailored specifically to autonomous sensor nodes in Internet of Things (IoT) networks. In a bid to increase the ambient power harvest, the proposed dual-band rectenna consists of 900MHz and 2.4GHz to increase the ambient power capture and also include an impedance-matching network to ensure low reflection losses and optimized broadband performance. The rectifier circuit entails the application of the diodes that are of the Schottkey type in rectifier circuit modeling on a voltage doubler-type topology that is analytically and numerically optimized with electromagnetic and nonlinear circuit co-simulation, resolving into an RF-to-DC power conversion power density peak efficiency 52% based on an input load of -10 dBm. A customer power management unit with cold start support and an adaptive maximum power point tracking algorithm (MPPT) is incorporated to control the energy harvested and allows constant operation. As the experimental evidence shows, in a 0 dBm continuous-wave RF source, the system maintains periodic sensing and data transmission duty with 10 percent duty cycle between a range of 5m. The comparative analysis with recent state-of-the-art prototypes which complement each other demonstrates improvement in operational range by 20 percent and doubling of efficiency in utilization of energy. These results confirm the possibility of battery-free, wire-free, deployment of sensors at scale inside and in cities, laying the foundation of reliable, long-life IoT networks.