Theory and Design of Dual-Band Microstrip Networks Using Embedded Metamaterial-Based Electromagnetic Bandgap Structures (MTM-EBGs)

This article examines implementations of the recently introduced metamaterial-based electromagnetic bandgap (MTM-EBG) structure, which may be embedded directly into the transmission-line (TL) segments of microstrip (MS) networks and whose dispersion properties may be accurately determined using multiconductor TL (MTL) theory. Two methods of imparting dual-band behavior to MS-based networks are introduced: utilizing stopband and passband regions of the EBG for frequency-selective signal routing, and using the phasing properties of the EBG to provide equal phase shifts at two separate frequencies. Two topological variants of the MTM-EBG are introduced and shown to provide different bandgap sizes, suiting each proposed application. A dual-band Wilkinson power divider, a dual-band quadrature hybrid coupler, and a dual-band impedance transformer are designed with embedded MTM-EBGs, which due to their ability to be realized in an entirely uniplanar form without vias and using a single dielectric layer, allow these devices to be entirely printable as well. The performance characteristics of all three devices are simulated and demonstrate excellent agreement with measurements. The design methodology is general and based on a rigorous MTL circuit model, making this approach amenable to a variety of MS networks, beyond what is presented.