The unpredictable propagation of ambient radio frequency (RF) waves may cause significant randomness in power densities against the propagation distance, time, and locations. To address this challenge, we propose a novel adaptive rectifier system with stabilized output dc power against dynamic power densities. A novel detection circuit is designed to identify the frequency range and receiving power level. Then the received RF power is amplified to the saturated level by referring to the detected frequency and power information for adaptive dc biasing control for an integrated power amplifier. Doing so makes the input power to the rectifier constant regardless of the power and frequency variations. The experimentally validated system can output a stabilized power under the time-varying power range of −10 to 0 dBm and location varying within 0.5 m at 1.8, 2.1, and 2.6 GHz. Compared with conventional designs, this system has realized stabilized and enhanced conversion efficiency (61% at 1.8 GHz, 64% at 2.1 GHz, and 53% at 2.6 GHz) and therefore could be adopted for wireless powering distributed sensors and Internet of Thing (IoT) devices continuously and steadily at flexible conditions.

Given the swift advancement of the Internet of Things (IoT) and wireless power transfer (WPT), there is an increasing need for incorporating new functionalities like wireless communication, recognition, sensing, and localization into existing systems. In response to these evolving demands, a transformative rectenna-based unified platform has been developed. This groundbreaking platform is engineered to harvest ambient wireless power while smartly managing the generated second-order harmonic signals. Illustrating its design, a multi-functional system has been implemented. This system can convert 52.9% of input radio frequency power into direct current power and achieve a state-of-the-art SH generation efficiency of 10.2% when the input RF power is set at 0 dBm. Concurrently, the harmonic signals can be re-radiated and automatically directed (steered) from –65° to 66°, facilitated by an 8×8 Butler matrix and an 8-way microwave switch, all controlled by a microcontroller unit (MCU). Notably, our platform extends beyond beamforming to embrace a broader spectrum of applications, including backscattering communication, simultaneous wireless information and power transfer (SWIPT), integrated sensing and communications (ISAC), and continuous wave detection. This expansion significantly enhances the scope and capability of rectification technology applications.

We present a novel design strategy for complex multiband rectifiers, named the “Rectifying Network Common Items Extraction (RNCIE)”. This approach involves sharing one rectifying network (i.e., the common items) between two or more parallel rectifiers, thereby significantly simplifying the design process. In contrast to the traditional global optimization method for multi-band (e.g., >3 bands) rectifier design, our RNCIE strategy can help realize the modular decomposition of the rectifier, including the rectifying network and impedance matching network (with the help of filter branches), thus leading to a significant reduction in design cost and complexity. Additionally, the unique advantage of the RNCIE contributes to in-depth analysis of the influencing factors on the total efficiency of the rectifier. Consequently, the RF-DC conversion efficiency of an example prototype of the rectifier design can be optimized to 44.6% @ 1.8 GHz, 45.4% @ 2.1 GHz, 41.7% @ 2.6 GHz, 33% @ 3.5 GHz, 30.2% @ 4.9 GHz, and 23% @ 5.8 GHz at an input power level of −10 dBm. Meanwhile, our rectifier with a shared rectifying network can improve the total efficiency when multi-tone signal inputs are used (27% @ −20 dBm, 43% @ −10 dBm for a six-tone signal). The strategy is verified by experimental measurements and paves the way for the efficient and accurate design of multi-band rectifiers of high efficiency.

In this paper, a novel topology and method for designing a multi-band rectenna is proposed to improve its RF-DC efficiency. The rectifier achieves simultaneous rectification using both series and parallel configurations by connecting two branches to the respective terminals of the diode, directing the energy input from two ports to the anode and cathode of the diode. Six desired operating frequency bands are evenly distributed across these two branches, each of which is connected to antennas corresponding to their specific operating frequencies, serving as the receiving end of the system. To optimize the design process, a low-pass filter is incorporated into the rectifier design. This filter works in conjunction with a matching network that includes filtering capabilities to isolate the two ports of the rectifier. The addition of the filter ensures that each structure within the rectifier can be designed independently without adversely affecting the performance of the already completed structures. Based on the proposed design methodology, a dual-port rectenna operating at six frequency bands—1.85 GHz, 2.25 GHz, 2.6 GHz, 3.52 GHz, 5.01 GHz, and 5.89 GHz—was designed, covering the 4G, 5G, and Wi-Fi/WLAN frequency bands. The measured results indicate that high-power conversion efficiency was achieved at an input power of −10 dBm: 43.01% @ 1.85 GHz, 41.00% @ 2.25 GHz, 41.33% @ 2.6 GHz, 35.88% @ 3.52 GHz, 22.36% @ 5.01 GHz, and 19.27% @ 5.89 GHz. When the input power is −20 dBm, the conversion efficiency of the rectenna can be improved from 5.2% for single-tone input to 27.7% for six-tone input, representing a 22.5 percentage point improvement. The proposed rectenna demonstrates significant potential for applications in powering low-power sensors and other devices within the Internet of Everything context.

This letter proposes a novel duplex rectifier design that enhances fundamental RF-to-second harmonic (FRF-SH) conversion efficiency while maintaining high RF-dc conversion efficiency. The proposed design features a harmonic matching network at the anode and harmonic suppression at the cathode, significantly enhancing SH generation efficiency via load-pull-based impedance optimization. Experimental results demonstrate that the proposed duplex rectifier achieves a peak FRF-SH conversion efficiency of 13.6%, with an RF-dc efficiency of 47% at an input power of 3 dBm. The simplified design reduces harmonic losses compared to previous approaches, providing a promising solution for efficient power conversion and communication in wireless sensors. This design methodology has applications in the Internet of Thing (IoT) and wireless power transfer (WPT), offering significant improvements in both energy harvesting and communication range.