Printed coupled lines with lumped loads for realizing degenerate band edge and magnetic photonic crystal modes

This paper proposes 4/6-port lumped element printed microstrip circuits composed of dual and coupled transmission lines to realize higher order dispersion behaviors emulating the (degenerate band edge) DBE crystals and magnetic photonic crystals (MPC). Harnessing the maximally flat dispersion of DBE unit cells resulted in a miniature printed antenna with a lambda₀/9 times lambda₀/9 footprint, 3% bandwidth and 4.5 dB gain. As such, this DBE antenna is found to be near the optimal Chu-Harrington limits. It is demonstrated that the DBE unit cell can be further miniaturized via lumped capacitor inclusions. Also, for the first time, a straightforward printed circuit realization of the stationary inflection points (SIP) is presented. Its realization using simple printed circuits is expected to allow for new delay lines and non-linear devices harnessing these novel SIP properties. Higher order filters and high aperture efficient array designs are also mentioned as future applications of the DBE and MPC circuits.