Experimental investigation on slotted Koch snowflake fractal patch rectenna

Radio frequency energy harvesting, a sustainable power source for IoT devices, faces limitations due to its low power density. However, existing slotted fractal antenna designs often lack systematic optimization and do not emphasize the 2 GHz band, which is crucial for urban RF energy harvesting. This article proposes a rectenna design featuring a Koch snowflake fractal patch antenna with optimized rectangular slots to enhance performance. A comparative study of single-slot and double-slot configurations revealed that double slots improve return loss peak depth and introduce additional resonance modes. The antenna was optimized using a multivariate parametric modelling-based approach with particle swarm optimization for the 2 GHz band. The 102 mm × 102 mm fabricated antenna exhibited - 26.8 dB return loss at 2.07 GHz, validated by experiments. Hence, the work demonstrated the feasibility of incorporating rectangular slots onto the Koch snowflake fractal patch. Furthermore, a half-wave rectifier circuit with a Pi matching network was fabricated. Initial discrepancies between the fabricated and simulated rectifier circuit resonant frequencies were observed. To address this, a microstrip line was introduced for impedance matching, and a capacitor was replaced with that of a higher operating frequency to minimize the parasitic effect due to the self-resonant frequency, thereby improving RF power transfer. The improved fabricated rectifier achieved over 20% RF-DC efficiency from an input power range of - 16 to 16 dBm at 1.88 GHz. Future work will focus on antenna size optimization and refined rectifier circuit simulations to develop a fully functional rectenna system for efficient energy harvesting.