Abstract
A decoupling metamaterial (MTM) configuration based on fractal electromagnetic-bandgap (EMBG) structure is shown to significantly enhance isolation between transmitting and receiving antenna elements in a closely-packed patch antenna array. The MTM-EMBG structure is cross-shaped assembly with fractal-shaped slots etched in each arm of the cross. The fractals are composed of four interconnected-`Y-shaped' slots that are separated with an inverted-`T-shaped' slot. The MTM-EMBG structure is placed between the individual patch antennas in a 2 × 2 antenna array. Measured results show the average inter-element isolation improvement in the frequency band of interest is 17, 37 and 17 dB between radiation elements #1 & #2, #1 & #3, and #1 & #4, respectively. With the proposed method there is no need for using metallic-via-holes. The proposed array covers the frequency range of 8-9.25 GHz for X-band applications, which corresponds to a fractional-bandwidth of 14.5%. With the proposed method the edge-to-edge gap between adjacent antenna elements can be reduced to 0.5λ 0 with no degradation in the antenna array's radiation gain pattern. Across the array's operating band, the measured gain varies between 4 and 7 dBi, and the radiation efficiency varies from 74.22 and 88.71%. The proposed method is applicable in the implementation of closely-packed patch antenna arrays used in SAR and MIMO systems.
Highlights
Electromagnetic interference between antenna elements is a major issue in multi-antenna systems
This is because mutual coupling resulting from surface currents over the antenna can seriously degrade its performance in terms of radiation gain, operating bandwidth, and radiation pattern [1]
This paper provides a solution to the oversize issue encountered with antenna arrays employing conventional EMBG techniques to suppress mutual coupling between neighbouring antennas
Summary
Electromagnetic interference between antenna elements is a major issue in multi-antenna systems. When the antenna array is combined with the fractal decoupling structure, the measured results show that the average isolation is better than -30 dB for S12, -41 dB for S13, and -28 dB for S14 across the antenna array’s operating bandwidth of 1.25 GHz from 8 to 9.25 GHz, which is two-fold greater than reported in literature. The size of the proposed antenna array is 2.4λ0×3.2λ0 with edge-to-edge gap between the radiating elements of 0.5λ0 centred at 8 GHz. FRACTAL MTM-EMBG DECOUPLING
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