1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 60 61 62 63 64 65 Self-Biased 2.4 GHz CMOS RF-to-DC Converter with 80% Efficiency and -22.04 dBm Sensitivity for Wi-Fi Energy Harvesting Kresil Joy P. Jimenez 1 , Jefferson A. Hora 2 , Olga Joy L. Gerasta 1 , Xi Zhu 2 , and Eryk Dutkiewicz 2 1 Microelectronics Laboratory, Mindanao State University - Iligan Institute of Technology, Iligan City, Philippines 2 School of Electrical and Data Engineering, University of Technology Sydney, NSW 2007, Australia kresiljoy.jimenez@g.msuiit.edu.ph, jefferson.hora@student.uts.edu.au Abstract—One of the significant disadvantages of RF energy harvesting is having a low power density in comparison to other ambient energy sources. The rectifier is the core of an RF energy harvesting system since it converts and boosts weak RF power to usable DC power. This study introduces a design of an efficiency enhanced RF-to-DC power converter with impedance matched to 50 Ω. The circuit design is based on two circuit design architectures, namely: the fully cross-coupled rectifier and self-biased technique, and the combined with LC matching circuit to obtain high power conversion efficiency. The design simulation is implemented using 65 nm CMOS Technology process. The performance of the proposed circuit design has achieved a peak power conversion efficiency of 80% at -14.4 dBm with a minimum input power of -22.04 dBm at 2.4 GHz for a load resistance of 20 kΩ and 10 pF load. Index Terms—Wireless Power Harvesting, CMOS Rectifier, RF-to-DC Converter, 2.4 GHz Wi-Fi Harvesting, Matching Cir- cuit. I. I NTRODUCTION Circuit designs and device development in CMOS technol- ogy has been explored in the past several decades. Several state-of-the-art circuit design techniques have been tested and used commercially, ranging from radio-frequency integrated circuits (RFIC) design [1]-[9] to millimeter-wave IC (mm- Wave) IC design [10]-[11]. Recently, the trend in powering low power wireless sensors is energy scrapping from the ambient electromagnetic wave that came to be known as RF energy. Electromagnetic waves are present from a range of sources including wireless internet, radio and satellite stations as well as in digital multimedia broadcasting. Compared to other energy sources, the main advantage of using RF electromagnetic waves as a replacement for batteries is that it is always available all day long [12]. The use of on-board batteries consumes space and is labor expensive to maintain. Moreover, disposing batteries can cause harmful effects on the environment. Harvesting RF energy can address the problem since it is abundant and is not limited by space and time. But in comparison with other ambient energy sources, such as solar energy and thermal energy, one disadvantage of RF energy is having a low power density. The rectifier is the core of an RF energy harvesting system since it converts and boosts weak RF power to usable DC power. Thus, the purpose of this study is to design an Efficiency Enhanced Self- Biased 2.4 GHz CMOS RF-to-DC Power Converter for Ambient Energy Harvesting. Fig. 1 shows a basic block diagram of an RF energy harvesting system. The RF energy source in this system might be a base station, a cellphone, or even a Wi-Fi router. The presence of these wireless devices such as cellphones and routers, particularly in urban environments, abundant Wi-Fi access points can be detected from a single location. Then the energy harvester antenna receives the incident RF power and is fed into a matching network. Finally, for the energy storage device and the load, a rectifier converts the RF power to DC power. Fig. 1. RF Energy Harvesting System II. DESIGN PARAMETERS The most crucial elements of the RF-to-DC converter are the diodes or transistors that determine the important parameters such as the operating frequency and efficiency. The Schottky diode was used for the first time in rectification due to its low threshold voltage. But the power conversion efficiency of Schottky diodes suffers greatly when dealing with microwatt applications [13]. Recent publications focus on CMOS pro- cesses because of its sensitivity to low operation voltages. The ICSyS2019 1570575107 1 Authorized licensed use limited to: University of Technology Sydney. Downloaded on September 12,2022 at 14:33:45 UTC from IEEE Xplore. Restrictions apply.