IEEE Access (Jan 2021)
Performance Enhancement of Low-Profile Wideband Multi-Element MIMO Arrays Backed by AMC Surface for Vehicular Wireless Communications
Abstract
A low-profile printed dipole antenna (PDA) backed by broadband rhomboid artificial magnetic conductor (AMC) is introduced for vehicular wireless communications. Firstly, a suggested PDA with a pair of the microstrip E-shaped dipoles is fed by an E-shaped microstrip feedline to expand the bandwidth in the measured range of 5.5-6.96 GHz ( $\text{S}_{11}\le -10$ dB). Then, the suggested rhomboid AMC reflector is inserted into the PDA to gain improved radiation efficiency up to more than 90%. The PDA loaded by the $3\times 3$ rhomboid AMC array with the size of 48 mm $\times48$ mm $\times6.8$ mm exhibits −10 dB measured impedance bandwidth from 4.48 to 7 GHz (almost 44%) for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The suggested PDA with AMC compared to the PDA without AMC exhibits a size reduction of 42.3%, enhanced gain up to 8.4 dBi, and excellent impedance matching (at least −20 dB) with uni-directional radiation patterns. The novel AMC unit cell is realized based on the recognized method as rhomboid coupled parasitic patches. The rhomboid AMC design operates at 6.20 GHz with an AMC bandwidth of 5.10-7.18 GHz (34%). Also, by loading $3\times 4$ and $5\times 5$ AMC reflectors into the two-element and four-element array of PDA, low-profile wideband structures with enhanced radiation properties are achieved. The measured S-parameters show the broad bandwidth from 4.48 to 7.12 GHz in C-band with enhanced gains and efficiencies (more than 90%) of multiple elements. Besides, the suitable isolation between the array elements of more than 30 dB for multiple-input multiple-output (MIMO) systems is achieved by applying various polarized directions of PDAs and loading periodic AMC reflectors.
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