Waveform Optimization for Wireless Power Transfer with Nonlinear Energy Harvester Modeling

Far-field Wireless Power Transfer (WPT) and Simultaneous Wireless Information and Power Transfer (SWIPT) have attracted significant attention in the RF and communication communities. Despite the rapid progress, the problem of waveform design to enhance the output DC power of wireless energy harvester has received limited attention so far. In this paper, we bridge communication and RF design and derive novel multisine waveforms for multi-antenna wireless power transfer. The waveforms are adaptive to the channel state information and result from a posynomial maximization problem that originates from the non-linearity of the energy harvester. They are shown through realistic simulations to provide significant gains (in terms of harvested DC power) over state-of-the-art waveforms under a fixed transmit power constraint.Comment: paper to be presented at IEEE International Symposium on Wireless Communication Systems (ISWCS 2015

Leakage Analysis and Solution of the RFID Analog Front-END

The identification and modeling of different leakage components are very important for estimation and reduction of leakage power, especially low-power applications, such as RFID chip. This paper proposes a theory about leakage mechanism of RFID chip and proves the theory. The one contribution of the paper is the proposed theory about leakage mechanism of RFID chip. The other contribution is that it proves the differences between tape-out verification results and computer simulation results and that to what degree the differences occur for different circuits. And when the source potential is much lower than the substrate potential, tape-out verification results and computer simulation results have larger differences. The test results show that the actual leakage power increases 26.3 times compares with the computer simulation results’ when the source potential is -750mV

Waveform design for Wireless Power Transfer

Far-field Wireless Power Transfer (WPT) has attracted significant attention in recent years. Despite the rapid progress, the emphasis of the research community in the last decade has remained largely concentrated on improving the design of energy harvester (so-called rectenna) and has left aside the effect of transmitter design. In this paper, we study the design of transmit waveform so as to enhance the dc power at the output of the rectenna. We derive a tractable model of the nonlinearity of the rectenna and compare with a linear model conventionally used in the literature. We then use those models to design novel multisine waveforms that are adaptive to the channel state information (CSI). Interestingly, while the linear model favours narrowband transmission with all the power allocated to a single frequency, the nonlinear model favours a power allocation over multiple frequencies. Through realistic simulations, waveforms designed based on the nonlinear model are shown to provide significant gains (in terms of harvested dc power) over those designed based on the linear model and over nonadaptive waveforms. We also compute analytically the theoretical scaling laws of the harvested energy for various waveforms as a function of the number of sinewaves and transmit antennas. Those scaling laws highlight the benefits of CSI knowledge at the transmitter in WPT and of a WPT design based on a nonlinear rectenna model over a linear model. Results also motivate the study of a promising architecture relying on large-scale multisine multiantenna waveforms for WPT. As a final note, results stress the importance of modeling and accounting for the nonlinearity of the rectenna in any system design involving wireless power