Metamaterial CRLH Structure-based Balun for Common-Mode Current Indicator

Abstract

We proposed a new PCB-type 'common-mode current(<TEX>$I_c$</TEX>) and differential-mode current(<TEX>$I_d$</TEX>) detector' working for fast detection of <TEX>$I_c$</TEX> and <TEX>$I_d$</TEX> from the differential-mode signaling, with miniaturization effect and possibility of cheaper fabrication. In order to realize this device, we suggest a branch-line-coupler balun having a composite right- and left-handed(CRLH) one-layer microstrip phase-shifting line as compact as roughly <TEX>${\lambda}_g/14$</TEX>. The presented balun obviously is different from the conventional bent-&-folded delay lines or slits on the ground for coupling the lines on the top and bottom dielectrics. As we connect the suggested balun output ports of the differential-mode signal lines via the through-port named U and coupled-port named L, <TEX>$I_c$</TEX> and <TEX>$I_d$</TEX> will appear at port <TEX>${\Delta}$</TEX> and port <TEX>${\Sigma}$</TEX> of the present device, in order. The validity of the design scheme is verified by the circuit-and numerical electromagnetic analyses, and the dispersion curve proving the metamaterial characteristics of the geometry. Besides, the examples of the <TEX>$I_c$</TEX> and <TEX>$I_d$</TEX> indicator are observed as the even and odd modes in differential-mode signal feeding. Also, the proposed device is shown to be very compact, compared with the conventional structure.