Electronically Controllable Impedance for tuning of active metamaterials

Increasing population density and the consequential increased demand of electrical energy require the integration of electrical infrastructure for power distribution into residential areas and buildings. In order to meet the installation standards regarding the critical value of field emissions, the magnetic stray field of the electric equipment needs to be shielded. One shielding option is to realise an active shield in the form of a metamaterial, (a concept known from high-frequency engineering). A metamaterial is in this case composed by an array of base units, each one containing a LCR-resonator and a control unit called Electronically Controllable Impedance (ECI). The ECI consists of a 4-quadrant power converter with integrated measurement and control units for emulating an arbitrary impedance. The ECIs are used to tune the LCR resonators such that the metamaterial exhibits a paramagnetic or diamagnetic behaviour when excited by an external field. Thereby, each single LCR-resonator's resonant frequency is adjusted to the excitation frequency and the resonator's quality factor Q is optimally selected. This paper shows different realisations of an ECI and proposes an ECI control algorithm to tune the resonant frequency and to adjust the quality factor Q of the resonators. Furthermore, an experimental verification of the ECI concept is provided.