Abstract
A metamaterial photonic bandgap (MTM-PBG) periodic structure is used as a decoupling frame to improve the isolation between transmit–receive (T/R) sections of the densely packed array antenna in synthetic aperture radar (SAR) and multiple-input–multiple-output (MIMO) systems. With this technique the MTM-PBG structure is shown to effectively suppress surface wave propagations between the T/R array antennas by an average of 12 dB. MTM-PBG layer comprises a periodic arrangement of dielectric circles etched in the cross-shaped microstrip frame that is inserted between the radiating elements. Unlike other recently reported methods, the advantages of the proposed technique are: (i) simplicity; (ii) cost effectiveness as there is no need for short-circuited via-holes or three-dimensional metal walls; and (iii) can be retrofitted in existing array antennas. The proposed T/R array antennas were designed to operate over an arbitrary frequency range (9.25–11 GHz) with a fractional bandwidth of 17.28%. With this technique (i) the side-lobes are reduced; (ii) there is minimal effect on the gain performance; and (iii) the minimum edge-to-edge gap between adjacent radiating elements can be reduced to 0.15λ at 9.25 GHz.
Highlights
One of the features of photonic or electromagnetic bandgap (PBG/EBG) structures is their ability to suppress surface currents within their bandgap [1]
photonic bandgap (PBG) structures have been extensively used to improve the performances of array antennas, e.g. this can be achieved by inserting PBG structures between antenna elements in arrays to suppress mutual coupling that exists between the elements
To date only a few works have been published on investigating isolation enhancement between radiating elements in a larger array antenna, which is crucial to the performance of multiple-input multiple-output (MIMO) and radar systems
Summary
One of the features of photonic or electromagnetic bandgap (PBG/EBG) structures is their ability to suppress surface currents within their bandgap [1] This property can be exploited to reduce the mutual EM coupling between radiating elements resulting from surface wave currents over the antenna [2]. PBG structures have been extensively used to improve the performances of array antennas, e.g. this can be achieved by inserting PBG structures between antenna elements in arrays to suppress mutual coupling that exists between the elements. Results reveal the effectiveness of the MTM-PBG layer in suppressing surface wave propagations between the radiating elements, and thereby enhancing isolation between T/R patches
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