Analysis of wireless power transfer systems using S parameters to generate the power gains

The wireless power transfer systems (WPTS) work at frequencies between 20 kHz – 40 MHz. Considering the system consisting of two magnetically coupled coils, used in WPTSs, as a passive linear two-port network (PL2PN) in harmonic state, this paper describes the possibility of using the scattering parameters S in generating the power gains between the two ports of these coils. The amplification (or attenuation) property of the PL2PN can be emphasised by comparing the active Pin - the power given by the PL2PN at its input, with PL - the active power transmitted to the load. By computing the most significant gains, we describe, in this paper, the practical use of S parameters in order to make more efficient the information propagation and transmission processes in the wireless electromagnetic energy transmission from the emitter to the receiver coils for WPTS. Starting from the correct formulation of S parameters, their generation takes place in an automatic manner, based on the corresponding modified nodal equations. For magnetically coupled coils' parameters we used the most advanced computation software (Cadence, ADS, Ansoft Extractor Q3D, CONSOL, Feko etc.). In this paper, there are defined, in terms of S parameters, a series of constants that are further used to compute the power gains. To generate: the reflexion coefficients, the input and output impedances, the stability factors, the power gains for the bilateral or unilateral signal transmission, Thévenin equivalent circuits, the maximum power transmitted to the load and the conjugate-match and the mismatch conditions of the two magnetically coupled coils, we developed functions and routines in MATLAB and we used the existing routines from MATLAB microwave toolbox. The obtained results are similar to those reported by the existing literature.