Electrical Reconfigurability in Modern 4G, 4G/5G and 5G Antennas: A Critical Review of Polarization and Frequency Reconfigurable Designs

This paper presents a critical review of modern 4G, 4G/5G, and 5G antennas, which employ PIN diodes and Varactors for polarization or frequency reconfiguration. For the reviewed 4G and 5G polarization reconfigurable antennas, a new parameter named spectrum utilization “AR/
$S_{11}$
B.W. ” is defined for the first time to predict the shared spectrum between the impedance bandwidth and the axial ratio bandwidth for circularly polarized antennas. The calculated spectrum utilization for many designs revealed that the majority of implementations failed to achieve full utilization of the available bandwidth. Besides, employing multiple PIN diodes is shown useful in improving the spectrum utilization and in supporting multiple polarization states. For the reviewed 4G, 4G/5G and 5G frequency reconfigurable antennas, the focus is mainly on comparing the available tuning range, fractional bandwidth and the Fractional Bandwidth Change (FBWC) upon tuning. The latter parameter, is defined and calculated in this work to measure the change in the FBW upon tuning. Utilizing multiple Varactors is shown promising in improving a 4G antenna’s fractional bandwidth, while combining Multiple PINs and Varactors in one design is found efficient in improving the FBWC and the tuning range in the 5G spectrum.