Multi-band Microwave Rectifiers for RF Energy Harvesting: A Comprehensive Review of Design Techniques and Performance Analysis

RF energy harvesting (RF-EH) technology has emerged as a key research direction driven by the increasing demand for sustainable power solutions in applications such as low-power wireless sensors, radio frequency identification (RFID) tags, IoT, and biotelemetry. The need to eliminate frequent battery replacements in large-scale sensor deployments has made RF-EH a promising alternative. At the core of these systems is the rectenna, a key component responsible for capturing and converting ambient RF energy into usable DC power. Research efforts have primarily focused on enhancing power conversion efficiency, ensuring compatibility with various sensors, and maximizing harvested power. Multi-band rectennas have gained significant attention for their ability to capture RF energy across multiple frequency bands, enabling higher overall power generation compared to narrowband counterparts. Consequently, multi-band rectifier circuits play a critical role in RF-EH systems. This paper presents a comprehensive review and performance analysis of multi-band rectifier designs, encompassing over 110 research studies published in the last decade. To enable objective comparison, we propose a novel power/frequency-weighted efficiency (PFE) metric, which accounts for operating frequency, input power, and the number of bands. This metric provides valuable insights into the efficiency of various rectifier architectures and serves as a benchmark for future advancements in RF energy harvesting.