Space Efficient Meta-Grid Lines for Mutual Coupling Reduction in Two-Port Planar Monopole and DRA Array

Mohit Mishra,Karu P. Esselle,Rakhesh Singh Kshetrimayum,Arokiaswami Alphones,Sumantra Chaudhuri

doi:10.1109/access.2022.3146941

Abstract

Traditionally used mutual coupling (MC) reduction techniques such as electromagnetic bandgap structures, isolators and neutralization lines require extra space between radiators. Besides, metamaterial-based techniques require multi-layer arrangements. However, the proposed meta-grid lines overcomes the above demerits by integrating meta-grid lines in the ground plane itself. As a proof-of-concept, two-port CPW-fed monopole antenna array (TPCFMAA) and two-port DRA array (TPDRAA) are designed, fabricated and tested. It has been observed that the TPCFMAA has mutual coupling below −20 dB for frequency between 2.6 to 4.4 GHz. The envelope correlation coefficient reduces from 0.072 to 0.026 by integrating meta-grid lines in the ground plane of the TPCFMAA. At 3.5 GHz, the inter-element distance between the antennas is noted to be <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${0.015}\lambda _{\mathrm {h}}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{\mathrm {h}}\,\,=$ </tex-math></inline-formula> highest operating wavelength). The TPDRAA’s operating frequency can be tuned by changing the parameters of the annular ring slot in the excitation patch. The bandwidth of TPDRAA can be further increased by merging the two resonances of the two annular ring slots in the excitation patch. For TPDRAA, the measured −10 dB impedance bandwidth is from 5.65 to 6.55 GHz. The mutual coupling between the antenna elements is seen to be below −16 dB for an inter-element spacing of 4.8 mm, which is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.090\lambda _{\mathrm {h}}$ </tex-math></inline-formula> . The measured gain of TPDRAA within the bandwidth is from 4.17 dBi to 5.2 dBi. The TPCFMAA can be used in 3.5 GHz Internet of Vehicles (IoV) multi-user MIMO service, whereas the TPDRAA can be used for satellite communication in the 5.925 to 6.425 GHz frequency band, WiMAX in the 5.7 to 5.85 GHz band, ISM in the 5.725 to 5.85 GHz band, and WLAN in the 5.8 GHz band.

Highlights

Multiple-input-multiple-output (MIMO) communication system fulfills the demand for higher data rate and better quality of service in modern communication systems
Compact MIMO communication systems generally deploy closely spaced multiple antennas at the transmitter and receiver sides. This results in an undesired mutual coupling (MC) effect, which is inversely proportional to the distance between the antenna array elements [3]
Two-port dielectric resonator antenna (DRA) array (TPDRAA) The novel aspect presented in this article is the use of meta-grid lines (MGLs) integrated with the ground plane for suppression of the surface wave linkage between the antenna elements and achieve a satisfactory isolation level

Summary

INTRODUCTION

Multiple-input-multiple-output (MIMO) communication system fulfills the demand for higher data rate and better quality of service in modern communication systems. The decoupling in [26] is realized by adding a pure DB above the coupled array, and a ceramic superstrate in [27] All these four designs have decoupling structures between or above the antenna elements, which significantly increase the antenna footprint. 2. Two-port DRA array (TPDRAA) The novel aspect presented in this article is the use of meta-grid lines (MGLs) integrated with the ground plane for suppression of the surface wave linkage between the antenna elements and achieve a satisfactory isolation level. This means that EBG and superstrates for MC reduction in patch antennas are generally very difficult to be employable in DRAs without major modifications in their structures and vice-versa This is not the case with presented technique because in TPDRAA, the dielectric blocks are excited by means of microstrip patch feed which are printed over an MGL (with wideband SNG characteristics) backed substrate.

UNIT CELL ANALYSIS

CONCLUSIONS