Design and Theoretical Analysis of a Microwave Energy Collector

The CTMEC (Copper Tube Microwave Energy Collector) project explores the system-level design and theoretical performance limits of a compact ambient RF energy harvesting system intended for ultra-low-power electronics. The design targets energy capture from dominant ISM-band sources, operating at 2.45 GHz and 5.8 GHz, within a planar form factor of 150 mm × 150 mm. To maximize collected power under favorable ambient conditions, the system employs a high-gain 4×4 dielectric resonator antenna array implemented on a high-permittivity Rogers RT/Duroid 6010 substrate, enabling dense element packing and an estimated realized gain of approximately 15 dBi. The RF-to-DC conversion stage is optimized for microwatt-level inputs typical of ambient harvesting scenarios. A zero-bias Schottky diode (Skyworks SMS7630-079) is used for rectification due to its low junction capacitance and minimal turn-on voltage, allowing efficient operation without external biasing. Power transfer is maximized through a lumped-element impedance matching network designed to accommodate the non-linear input impedance of the rectifier. The rectified output is processed through a multi-stage Greinacher voltage multiplier to boost the low-amplitude signal to a usable DC level in the 3.3–5 V range, suitable for modern ultra-low-power microcontrollers and sensor nodes. Under a strong ambient RF power density assumption of 5 µW/cm², the effective aperture of the antenna array yields an estimated RF input power of approximately 1.125 mW. With an aggressive theoretical RF-to-DC efficiency target of 85%, the corresponding maximum DC output is approximately 0.96 mW, representing an upper-bound performance limit. The project is primarily simulation-driven and conceptual in nature, focusing on antenna–rectifier co-design, impedance optimization, and efficiency analysis to evaluate the feasibility of milliwatt-scale ambient RF energy harvesting within compact geometries.