Abstract
A closely packed wideband multiple-input multiple-output (MIMO)/diversity antenna (of two ports) with a small size of less than 18.5 mm by 18.5 mm is proposed for mobile communication applications. The antenna can be orthogonally configured for corner installation or by placing it on a back-to-back structure for compact modules. To enhance the isolation and widen the bandwidth, the antenna is structured with multiple layers having differing dielectric constants. The feeding through a via significantly reduces the ground waves. A multi-fidelity surrogate model-assisted design exploration method is employed to obtain the optimized antenna geometric parameters efficiently. The antenna design was investigated using electromagnetic simulation and a physical realization of the optimal design was then created and subjected to a range of tests. The specific parameters investigated included reflection coefficients, mutual coupling between the input ports, radiation patterns, efficiency and parameters specific to MIMO behavior: envelope correlation coefficient and pattern diversity multiplexing coefficient. It was found that the antenna has an impedance bandwidth of approximately 4 GHz, mutual coupling between input ports of better than −18 dB and an envelope correlation coefficient of less than 0.002 across the operating band. This makes it a good candidate design for many mobile MIMO applications.
Highlights
Small size, high data rates, reliable connectivity, and flexible operation without reconfiguration in many regions and systems are extremely attractive features in current and future mobile devices [1,2].To achieve the above, wideband and higher-frequency antennas have experienced many developments in recent years [3]
Multiple-input multiple-output (MIMO) technology is another effective technique for mitigating this issue, in addition to its features of increasing the channel capacity and transmission quality [4]
Due to some existing wireless standards, i.e., WiMAX (3.3–3.7 GHz), WLAN (5.15–5.35 GHz, and 5.725–5.825), etc., that share the frequency bands within the UWB regulation standards, this causes interference to the UWB system and degrades its performance
Summary
High data rates, reliable connectivity, and flexible operation without reconfiguration in many regions and systems are extremely attractive features in current and future mobile devices [1,2]. While vertical stacking of patches is a known broadbanding technique, large bandwidth is achieved here by feeding the driven (main) patch through a via and the use of parasitic patches that are laterally displaced in a single plane This lateral displacement with respect to the center of the main patch, generates multiple odd-order resonances which cause the bandwidth to increase significantly [34]. The design implemented high dielectric constant substrates, modified the shapes of the parasitic patches and radiator, and a feeding structure to obtain the required characteristics of compact size, good return loss, low mutual coupling level and reasonable gains and radiation patterns. The structure of the feed from the SMA connectors to the respective driven
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