Dual-Band Microstrip Corporate Feed Network Using an Embedded Metamaterial-Based EBG

Abstract

This paper demonstrates the design and experimental validation of a dual-band microstrip (MS) corporate feed network using an embedded metamaterial-based electromagnetic bandgap (MTM-EBG) structure. The MTM-EBG is designed to appear as a 35.4 Ω MS transmission line (TL) with a 90° electrical length at both 2.4 and 5.0 GHz. This structure is then used in place of a conventional single-band quarter-wavelength transformer in a 50 Ω MS T-junction power divider, rendering it dual band with 10 dB return-loss fractional bandwidths of 82.3% and 12.0% at center frequencies of 2.4 and 5.0 GHz, respectively. The result of this modification shows a very good performance at both operating frequencies, as well as substantial rejection over a prescribed bandwidth of intermediate frequencies. The dualband transformer formed by the embedded MTM-EBG is 30.5% miniaturized at 2.4 GHz relative to a conventional MS quarterwavelength transformer, which indicates its potential for use in size-restricted scenarios and embedded filtering applications. A dual-band four-way corporate feed network is then formed by cascading the MTM-EBG-loaded T-junction power dividers, which is suitable for antenna array applications. This structure has an improved performance at 2.4 and 5.0 GHz compared to unloaded networks designed for these frequencies having the same overall size. The experimental 10 dB fractional bandwidth for the MTM-EBG-loaded corporate feed network was found to be 52.0% and 10.8% around 2.4 and 5.0 GHz, respectively.