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

This work demonstrates the design and experimental validation of a dual-band microstrip (MS) corporate feed network using an embedded metamaterial-based electromagnetic bandgap structure (MTM-EBG). 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 GHz 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 GHz and 5.0 GHz, respectively. The result of this modification is very good performance at both operating frequencies as well as substantial rejection over a prescribed bandwidth of intermediate frequencies. The dual-band transformer formed by the embedded MTM-EBG is 30.5% miniaturized at 2.4 GHz relative to a conventional MS quarter-wavelength transformer, which indicates potential for usage 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 improved performance at 2.4 GHz 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 GHz and 5.0 GHz, respectively.