Novel common-mode current detector using metamaterial CRLH transmission-line structure

A novel planar common-mode current(Ic) and differential-mode current(Id) detector is designed to provide a quick check of Ic and Id from the differential-mode signalling, size-reduction effect and possibility of lower manufacturing cost. This is made possible by implementing a branch-line balun which has metamaterial Composite Right- and Left-Handed(CRLH) 1-layer microstrip- structure phase shifter as small as approximately λ_g/14. The proposed balun clearly differs from others who meander the delay line or make slits on the metal ground. When the proposed balun is connected to the output ports of the differential-mode signal lines through its inputs Port U and Port L, Id and Ic are obtained at Port Δ and Port Σ of this compact balun, respectively. The design method is validated by the circuit and full-wave simulations(SEMCAD X) with the dispersion diagram showing metamaterial properties of the structure. Also, the even and odd modes in differential-mode signalling are treated as examples of the Ic and Id Detector. The size-reduction effect is addressed also.