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This paper presents a nonlinear capacitive WPT system that automatically compensate for the coupling variation between the transmitter and receiver in a capacitive wireless power transfer (WPT) system with no active circuitry. The system is capable of minimizing the output power variation at a fixed operating frequency of13 MHz as the coupling distance varies. A constant output power is achieved over a wide range of coupling capacitance variation in comparison to the conventional capacitive wireless power transmission circuits. Such an approach is attractive for biomedical implants employing a capacitive WPT system. 

Conventional linear resonant wireless power trnnsfer (WPT) systems suffe1· from a significant pe1•formance degrndation as the coupling factor between the translnit and receive coils varies. In this paper, the performance of a new WPT circuit that takes the advantage of nonlinear resonant circuit is investigated. It employs passive nonlinear resonators in both the trnnslnitter and receiver sides to regulate the output power without using any active or control circuitry, frequency tuning or complicated coil configurntions. A 60 W nonlinear WPT prototype circuit working at 1.5 MHz is designed, fab1icated and compared with a silnilal'ly designed linear \VPT circuit. The nonlinem· \VPT circuit is capable of maintaining almost a constant output power while the distance between the coils changes from 6 cm to 15 cm, a significant performance improvement as compared to the linear WPT circuit tested under the same conditions. 

Wireless communication has become an integral part of our lives, continuously improving the quality of our everyday activities. A multitude of functionalities are offered by recent generations of mobile phones, resulting in a significant adoption of wireless devices and a growth in data traffic, as reported by Ericsson [1] in Figure 1. To accommodate consumers' continuous demands for high data rates, the number of frequency bands allocated for communication by governments across the world has also steadily increased. Furthermore, new technologies, such as carrier aggregation and multiple-input/multiple-output have been developed. Today's mobile devices are capable of supporting numerous wireless technologies (i.e., Wi-Fi, Bluetooth, GPS, 3G, 4G, and others), each having its own designated frequency bands of operation. Bandpass filters, multiplexers, and switchplexers in RF transceivers are essential for the coexistence of different wireless technologies and play a vital role in efficient spectrum usage. Current mobile devices contain many bandpass filters and switches to select the frequency band of interest, based on the desired mode of operation, as shown in Figure 2. This figure presents a schematic of a generic RF front end for a typical mobile device, where a separate module is allocated for the filters. Each generation of mobile devices demands a larger number of RF filters and switches, and, with the transition toward 5G and its corresponding frequency bands, the larger number of required filters will only add to the challenges associated with cell-phone RF front-end design. 

Wireless communication has become an integral part of our lives, continuously improving the quality of our everyday activities. A multitude of functionalities are offered by recent generations of mobile phones, resulting in a significant adoption of wireless devices and a growth in data traffic, as reported by Ericsson [1] in Figure 1. To accommodate consumers' continuous demands for high data rates, the number of frequency bands allocated for communication by governments across the world has also steadily increased. Furthermore, new technologies, such as carrier aggregation and multiple-input/multiple-output have been developed. Today's mobile devices are capable of supporting numerous wireless technologies (i.e., Wi-Fi, Bluetooth, GPS, 3G, 4G, and others), each having its own designated frequency bands of operation. Bandpass filters, multiplexers, and switchplexers in RF transceivers are essential for the coexistence of different wireless technologies and play a vital role in efficient spectrum usage. Current mobile devices contain many bandpass filters and switches to select the frequency band of interest, based on the desired mode of operation, as shown in Figure 2. This figure presents a schematic of a generic RF front end for a typical mobile device, where a separate module is allocated for the filters. Each generation of mobile devices demands a larger number of RF filters and switches, and, with the transition toward 5G and its corresponding frequency bands, the larger number of required filters will only add to the challenges associated with cell-phone RF front-end design.