EMC Coupling Between Two Composite Right/Left-Handed (CRLH) Transmission Lines on PCBs Irfanullah, Shahid Khattak, and Imdad Khan Department of Electrical and Computer Engineering COMSATS University Islamabad, Abbottabad Campus, Pakistan eengr@cuiatd.edu.pk Abstract ─ Unintentional electromagnetic coupling (crosstalk) between PCB lands is an important aspect of the design of an electromagnetically compatible product. In this paper, analytical model to predict crosstalk between two composite right/left-handed (CRLH) transmission lines in close proximity on PCBs is developed, and validated with full-wave simulation and measurement results. A cascaded seven unit cells CRLH transmission line (TL) acting as source of the electromagnetic emission was placed in close proximity to another seven unit cells CRLH transmission line acting as receptor of the emission on PCBs. Then the near- and far-end crosstalk voltages induced from the generator CRLH-TL to receptor TL for various separations between them were analyzed. It is shown that the crosstalk voltages computed with developed analytical model agrees well with full-wave simulation and measured results. Furthermore, it is shown that the left-handed capacitance and inductance design parameters of CRLH-TL can be used to reduce the crosstalk voltages induced on the receptor circuit leading to a cost-effective solution for shielding of near-by CRLH-TL receptor circuits printed on PCBs for various engineering applications. Index Terms ─ CRLH, crosstalk, coupler, EMC. I. INTRODUCTION An important aspect of the design of an electromagnetically compatible product is crosstalk. This essentially refers to the unintended electromagnetic coupling between wires and PCB lands that are in close proximity. The crosstalk analysis (i.e., to determine the near-end and far-end voltages) between conventional coupled cables and coupled PCB lands has been widely studied in the literature, see for example [1-3, 16-18]. Recently, characteristics of the composite right/left- handed (CRLH) metamaterial transmission lines (MTM- TLs) from intentional/tight coupling point of view (for example directional couplers) has been investigated [4-6]. While a lot of attention has been paid to the intentional coupling between CRLH-TLs, not much work (except in [7]) has been done on these couplers from an unwanted electromagnetic compatibility (EMC) coupling perspective. In the research community there is a growing interest to use CRLH-TLs in the design of feed network for antenna arrays [8-10], particularly by placing multiple RH/CRLH-TLs in the feed network to obtain different polarizations [11]. In such scenarios, unwanted coupling from one TL to another can degrade the systems’ performance by deteriorating the desired radiation patterns. Similarly multiple coupled CRLH- TLs have been realized in super-resolution imaging applications [12]. Therefore analysis of crosstalk voltages to mitigate mutual coupling is an important design parameter to obtain the desired performance metrics. In [7], analysis of noise voltage coupling between right- handed (RH) and CRLH-TLs has been formulated. The research work in the paper differs from previous work as follows: In [4]-[6] coupling between CRLH-TLs has been investigated from intentional coupling point of view, that is to couple more power to the receptor TL (ideally 0 dB). In the proposed work, coupling from EMC point of view has been analyzed, that is the objective is to mitigate the coupled voltages from generator CRLH-TL to the receptor CRLH-TL. The work in [7] assumes weak coupling between RH-TL and CRLH-TL, that is the effects of coupling only from generator RH-TL to victim CRLH-TL has been considered and not the effects of coupling back from CRLH-TL to RH-TL has been included. In [1-2 and 7], derivations of NEXT and FEXT is done with the assumptions of weak coupling between coupled transmission lines, and therefore the models cannot predict the crosstalk voltages for strong coupling between the PCB lands, where the transmission lines are printed in close proximity on the printed boards. In contrast to [7], the proposed work here considers the two-way effects of mutual coupling (coupling from generator CRLH-TL to receptor CRLH-TL and back to the generator circuit by the receptor circuit) to compute crosstalk voltages. Therefore, the proposed crosstalk model predicts the near- and far-end coupled voltages for any arbitrary spacing between the coupled transmission lines. Different commercially available simulators are ACES JOURNAL, Vol. 35, No. 1, January 2020 1054-4887 © ACES Submitted On: August 3, 2019 Accepted On: December 28, 2019 51