A Review on Sub-6GHz Multiband Antennas for 5G-Based IoT Systems

Abstract

The fast growth of fifth-generation (5G) networks and Internet of Things (IoT) requires the development of compact high-performance antennas which operate
within the sub-6 GHz spectrum. The antennas need to support multiple frequency bands while keeping high efficiency levels and delivering dependable operation
for wearable electronics and smart sensors and high-capacity Multiple-Input Multiple-Output (MIMO) systems. This review provides an extensive evaluation of
modern sub-6 GHz antenna designs through an examination of four prominent antenna types which include microstrip patch antennas, slot antennas, monopole
antennas and Planar Inverted-F Antennas (PIFA). The paper examines multiple advanced enhancement methods which include slot and stub loading together with
Defected Ground Structures (DGS) and Metamaterials/Metasurfaces and reconfigurable mechanisms and machine learning-assisted optimization and flexible
material utilization. Additionally, the evaluation of selected studies examines key performance parameters which include gain, efficiency, reflection coefficient
(S11), Envelope Correlation Coefficient (ECC), mutual coupling, polarization, compactness and Specific Absorption Rate (SAR) are discussed. The analysis of
existing literature shows that ECC and SAR and polarization diversity metrics receive insufficient reporting in wearable and MIMO antenna research. Finally, the
review paper identifies design limitations for advancing antenna development in 5G-enabled IoT systems.