Abstract
Advances in reconfigurable liquid-based reconfigurable antennas are enabling new possibilities to fulfil the requirements of more advanced wireless communication systems. In this review, a comparative analysis of various state-of-the-art concepts and techniques for designing reconfigurable antennas using liquid is presented. First, the electrical properties of different liquids at room temperature commonly used in reconfigurable antennas are identified. This is followed by a discussion of various liquid actuation techniques in enabling high frequency reconfigurability. Next, the liquid-based reconfigurable antennas in literature used to achieve the different types of reconfiguration will be critically reviewed. These include frequency-, polarization-, radiation pattern-, and compound reconfigurability. The current concepts of liquid-based reconfigurable antennas can be classified broadly into three basic approaches: altering the physical (and electrical) dimensions of antennas using liquid; applying liquid-based sections as reactive loads; implementation of liquids as dielectric resonators. Each concept and their design approaches will be examined, outlining their benefits, limitations, and possible future improvements.
Highlights
Antennas are one of the critical components in wireless communication systems, which must be designed and deployed efficiently
Such concept has been applied in [18], where four independent DC bias voltages are applied to two pairs of dipole arms containing eutectic gallium indium (EGaIn) liquid metal and electrolyte to control the lengths of each individual arm
An example of the reactive loading technique involves the integration of Galinstan liquid metal into slot structures to achieve frequency reconfigurability in a coplanar waveguide (CPW)-fed folded slot antenna in [23]
Summary
Antennas are one of the critical components in wireless communication systems, which must be designed and deployed efficiently. These metallic liquids feature excellent electrical and thermal conductivity, nontoxicity, and unique physical properties They have been implemented for frequency reconfigurability [14], polarization reconfigurability [15], radiation pattern reconfigurability [16], gain reconfigurability [17], and the combined reconfiguration of multiple parameters, or compound reconfigurability [18]. The article in [11] reviewed the design techniques, advantages, and limitations of liquid-based antennas, focused on dielectric liquids Despite this literature, none of these reviews have focused on the detailed concepts, design approaches, and implementation of conductive and dielectric liquids into different types of single-parameter and compound reconfigurable antennas. A future perspective of such mechanism, highlighting the life expectancy of these liquids concludes this article
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