A complementary Sierpinski gasket fractal antenna array integrated with a complementary Archimedean defected ground structure for portable 4G/5G UWB MIMO communication devices

Abstract

AbstractThis article presents the design, development, and experimental validation of an aperture coupled complementary Sierpinski gasket equilateral triangular fractal antenna array for portable 4G/5G UWB communication devices. The proposed antenna array is printed on two FR‐4 substrate layers (ε r = 4.4, height = 1.57 mm, and tan δ = 0.024) with two fractal triangular patches on the top layer (separated by a distance of 3λ/2) and feed network on the bottom layer of FR‐4. The fractal patches (optimized up to second order of iteration) are fed using an aperture‐coupled feeding mechanism, where the aperture slots in the ground layer are modified to complementary Archimedean spiral slots which are interconnected by a modified “X” shaped slot to improve the impedance matching at the operational bands. The proposed array has overall volumetric dimensions of 41 × 99.4 × 3.245 mm3 and provides a size reduction of 46% for the metallic area using the fractal geometry. The proposed array shows a simulated UWB response from 4.3 to 11.6 GHz (fractional bandwidth of 91.8% at 7.95 GHz) with a simulated peak gain of 4.7 dB (at 9.2 GHz) and port‐to‐port isolation of ≤−15.8 dB for the entire band. For validation of simulated responses, the proposed array is fabricated and tested for S‐parameters (S11, S22, S12, and S21). A measured impedance bandwidth of 6.3 GHz is observed for a frequency band from 5.7 to 12 GHz. Two additional frequency bands are also exhibited by the array from 4.1 to 4.25 GHz and 4.7 to 5.3 GHz. The array diversity parameters such as envelope correlation coefficient (≤0.007 [simulated], ≤0.0057 [measured]), diversity gain (≥9.999 [simulated], ≥9.971 [measured]), mean effective gain (≥−3.9 dB [simulated], ≥−5.1 dB [measured]), and channel capacity loss, (≤0.37 bits/s/Hz [simulated], ≤0.4 bits/s/Hz [measured]) which are calculated using the simulated and measured S‐parameters of the array are also observed. These parameters allow the proposed fractal array to be implemented in a diversity combining technique to improve the overall SNR and hence support a high data rate for 4G/5G multimedia services.