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A broadband and polarization-insensitive high impedance surface (HIS) metamaterial absorber (MA) based on octagonal ring-shaped resistive patches is presented. The absorber is investigated theoretically, experimentally and by simulation. The simulated results indicate that this structure obtains 10.28 GHz-wide absorption from 3.65 to 13.93 GHz with absorptivity larger than 90% at the normal incidence. Experimental results are in accordance with those of the simulation results. The electromagnetic (EM) field distributions and the plots of surface power loss density have been illustrated to analyze the absorption mechanism of the structure. Further simulations of the absorptivity of the proposed absorber with different surface resistances and substrate thicknesses indicate that there exist optimal values for the design. The polarization-insensitive feature and the properties under oblique incidence are also investigated. Finally, the interference theory is introduced to analyze and interpret the broadband absorption mechanism at both normal and oblique incidence. The calculated absorption rates of the proposed absorber coincide well with the simulated results. Therefore, the simulated and experimental results verify the validity of the theoretically analytical method for this type of broadband absorber.Index Terms-High impedance surface (HIS), metamaterial absorber (MA), broadband, microwave, interference theory.

In amount of practical applications of wireless power transfer (WPT), charging electric vehicles (EVs) has attracted much attention. Dynamic WPT is considered as a solution to the problem of battery bottleneck and the difficulty of convenient charging encountered in the development of EV. However, the transfer power can hardly be maintained stable under large coil misalignment in movement. What is more, the transfer efficiency will decline correspondingly. A method of optimisation design is presented from the perspective of against misalignment for dynamic series-series (SS) WPT system. The primary compensation capacitance is well designed to regulate transfer power fluctuation in WPT system. Then the optimal load is matched by DC-DC converter to guarantee the highest average transfer efficiency. A secondary-only resonant SS WPT system with fixed frequency is finally built. The power transfer profile is smooth against coupling coefficient to realise high tolerance to position as the power drop (raise) percentage is no more than 10% (20%) within 200% variation of coupling coefficient for different loads. Meanwhile, the efficiency can always be maintained at a high level.