Fast and Accurate Approach to RF-DC Conversion Efficiency Estimation for Multi-Tone Signals

Abstract

The paper presents a computationally efficient and accurate numerical approach to evaluating RF–DC power conversion efficiency (PCE) for energy harvesting circuits in the case of multi-tone power-carrying signal with periodic envelopes. This type of signal has recently received considerable attention in the literature. It has been shown that their use may result in a higher PCE than the conventional sine wave signal for low to medium input power levels. This reason motivated the authors to develop a fast and accurate two-frequency harmonic balance method (2F-HB), as fast PCE calculation might appreciably expedite the converter circuit optimization process. In order to demonstrate the computational efficiency of the 2F-HB, a comparative study is performed. The results of this study show that the 2F-HB significantly outperforms such extensively used methods as the transient analysis (TA), the harmonic balance method (HB), and the multidimensional harmonic balance method (MHB). The method also outperforms the commercially available non-linear circuit simulator Keysight ADS employing both HB and MHB. Furthermore, the proposed method can be readily integrated into commonly used commercially available non-linear circuit simulation software, including the Keysight ADS, Ansys HFSS, just to name a few—minor modifications are required. In addition, to increase the correctness and reliability of the proposed method, the influence of PCB is considered by calculating Y parameters of its 3D model. The widely employed voltage doubler-based RF–DC converter for energy harvesting and wireless power transfer (WPT) in sub-GHz diapason is chosen to validate the proposed method experimentally. This RF–DC converter is chosen for its simplicity and capability to provide sufficiently high PCE. The measurements of the PCE for a voltage doubler prototype employing different multi-tone waveform signals were performed in laboratory conditions. Various combinations of the matching circuit element values were considered to find the optimal one in both—theoretical model and experimental prototype. The measured PCE is in very good agreement with the PCE calculated numerically, which attests to the validity of the proposed approach. The proposed PCE estimation method is not limited to one selected RF–DC conversion circuit and can also be applied to other circuits and frequency bands. The comparison of the PCE obtained by means of the proposed approach and the measured one shows very good agreement between them. The PCE estimation error reaches as low as 0.37%, and the maximal estimation error is 32.65%.

Efficient Multi-Hop Wireless Power Transfer for the Indoor Environment

“…The fabricated prototype in Figure 10 is a compact solution fabricated on a 1.6 mm FR4 base. This design was explored in our works [41,44] and we proved its efficiency. The latest iteration of this design uses low-DC-resistance inductors from Coilcraft, allowing for reaching significantly higher power conversion efficiency (PCE).…”

“…The schematic in Figure 5 shows the MHN design layout and component selection. The chosen RF-DC converter is based on the well-known and extensively used voltage doubler topology with two Schottky diodes SMS7630 [41]. These diodes are well-suited for high-frequency applications, owing to the low voltage drop they exhibit.…”

“…The presented approach results in a simpler design that can provide greater distance than the previously mentioned signal generation-based approach. The carrier frequency of the WPT system in the study is 865.5 MHz, as this frequency was used in our prior research [41] on RF-DC converter designs for WPT purposes. The emphasis on the sub-GHz range (primarily the ISM bands) is due to the increased distance for power transfer with compatibility with IoT and LORA.…”

Wireless Sensing and Networking for the Internet of Things

“…For the energy harvesting of IoT in paper [ 9 ], a fast and accurate numerical method was given to determine the RF–DC power conversion efficiency (PCE) of energy harvesting circuits in the case of power-carrying signals with multiple tones and periodic envelopes. In recent years, extensive research has been conducted on this kind of signal.…”

“…A comparison study was conducted to show how well the 2F-HB works when it comes to computing. The results of [ 9 ] show that the 2F-HB performs much better than widely used methods such as the transient analysis (TA) method, the harmonic balance method (HB), and the multidimensional harmonic balance method (MHB). This method also proved to be more effective than Keysight ADS, a commercial non-linear circuit simulator that uses both HB and MHB.…”