Capacitive technology for wireless power transmission has been shown to be a good option for charging the batteries of electric vehicles. It offers better coupling between the transmitter and the receiver than inductive power transmission. On the other hand, it has some disadvantages; for example, it is very sensitive to the distance between plates. Several ideas have recently been proposed to overcome this disadvantage. However, a proper analysis methodology is still lacking, as is a proper design procedure for the circuits used in capacitive transmission. In this paper, an analysis and design methodology is presented for applying the Z-tank resonant circuit to capacitive power transmission, and the theoretical design methodology is based on normalized equations with respect to the operating resonance frequency. The analysis methodology and design procedure result in a circuit where the resonance frequency remains constant despite changes in the distance between the capacitive plates. The simulation results validate the proposal; to ensure robust, realistic simulation results, parasitic elements were considered in all reactive components, and robust models were built for the switching elements, such as MOSFETs and diodes. The results show that the multi-resonant characteristic of the circuit achieves maximum energy transfer and high efficiency.

QR codes (Quick Response) were originally developed by the automotive industry to enable rapid data exchange and have since evolved into versatile tools for commercial applications, such as linking to products or websites. However, the scope of their adoption has expanded into sensitive domains including financial, corporate, and governmental sectors. In order to address increasing security concerns, this work proposes a novel three-layer protection scheme. First, data confidentiality is ensured through encryption—in this study, symmetric AES (Advanced Encryption Standard) encryption is used as an example, though any encryption algorithm can be employed. Second, a multiplexing technique is employed to integrate two independent dichromatic QR codes into a single printed chromatic structure. Third, the recovery of each dichromatic code is achieved through the controlled incidence of specific wavelengths, not only providing improved channel separation but also functioning as a physical access control mechanism. This physical layer restricts unauthorized reading.

Capacitive power transfer (CPT) is a technology that is emerging as an alternative to inductive power transfer (IPT) in applications requiring low to medium power. A great interest has been developed in the implementation of CPT systems in battery charging systems, where a condition to compete with IPT systems is the need to increase the power transfer in the CPT systems without significant losses. This paper puts forth a design methodology for a stabilizing network, which has been applied to a CPT system. This methodology has been developed through impedance analysis of the circuit, in order to achieve maximum power transfer, with total gains of voltage and current reaching a value close to unity. The methodology allows for the calculation of the value of the components of the stabilizing network, which has been designed with the objective of stabilizing the resonant frequency against changes in the capacitance of the transmission plates. To validate the design procedure, an experimental prototype was developed at 25 W and an operational frequency of 1.55 MHz. The results obtained validate the design methodology.