Highly reduced mutual coupling between wideband patch antenna array using multiresonance EBG structure and defective ground surface

This paper presents a novel slotted wideband microstrip patch antenna array with 2 decoupling structures that enabled isolation enhancement between 10 and 40 dB throughout the operating bandwidth of 4-6.5 GHz. Four asymmetrical patches were first used as a unit cell to produce a multiresonance electromagnetic band gap (EBG) structure capable of increasing the isolation between the patch array by about 50 dB within the impedance bandwidth of 5.8-6.4 GHz. By introducing 3 double F-shaped etchings in the array ground plane, the isolation bandwidth is extended to 4.0-6.5 GHz (ie, 48%) with measured isolation improvement of 10-40 dB over the entire isolation bandwidth. The multiresonance EBG structure mitigates the surface waves propagating in the substrate while the double F-shaped ground plane reduces the surface waves traveling on the ground plane. The edge-to-edge spacing between the 2 patch antennas is 25.2 mm which is equivalent to 0.42 lambda(0) (lambda(0) is the free-space wavelength at the center frequency of 5.0 GHz). After loading the decoupling structures in the antenna array, the gain increased from 5.6 dB to 7 dB. The proposed antenna is fabricated and there is an acceptable agreement between the simulated and measured results. The antenna radiation characteristics are observed to be fairly consistent over the large operating bandwidth of 4-6.5 GHz. The proposed antenna is a potential candidate for wideband wireless applications in the sub-6 GHz band.