Frequency reconfigurable patch antenna using liquid metal as switching mechanism

Abstract

The use of liquid metal as a switching mechanism for a frequencyreconfigurable edge-fed microstrip patch antenna designed to operate in either the 2.4 GHz ISM band or the 1.6 GHz GPS band is illustrated. A partitioned fluidic manifold bonded to the top of the antenna enables the pressure-driven displacement of a low-loss dielectric fluid and the liquid metal from a reservoir atop the patch to switch between the two antenna states. Fabrication and measurement of the antenna illustrates the use of fluidics as an alternative to RF switches for reconfigurable antennas.Introduction: There has been increased interest in reconfigurable antennas in the past few years owing to their versatility over fixed-operation antenna designs. Improvements in RF reconfiguration technologies such as RF MEMS, pin diodes and FET switches [1-3] have enabled much of this growth through their versatility and reliability. These tuning mechanisms are often terminally connected to provide electronic control, and isolating the biasing and control circuits from the antenna's operation can be challenging. Fluidic systems are emerging as an alternative reconfiguration mechanism since pressure-driven systems [4] can be made electromagnetically transparent (or minimally intrusive). Eutectic Gallium Indium (EGaIn) has recently shown its usefulness in fluidic [5] and RF applications [6]. EGaIn has several benefits; the most notable being that it is non-toxic -when compared with other liquid metals, such as mercury.This Letter demonstrates the use of EGaIn in a frequency-reconfigurable antenna with a minimally intrusive fluidic actuation system. The Letter first describes the design procedure involved in creating the dual band antenna. Next is a discussion of the channel design and fluidics involved in the operation. Lastly is a discussion of the measurements of the fabricated antenna's voltage standing wave ratio (VSWR) and load impedance.

Liquid-Metal-Based Reconfigurable Components for RF Front Ends

“…As a low-loss metallic conductor, Galinstan is well suited for high-Q applications [24], and its fluidic nature makes it a natural candidate for reconfigurable devices, including tunable antennas [25], planar filters [26], and baluns [27]. The SIW bandpass filter is based on the physical dimensions of the cavity, which is determined by the placement of via posts using [28]:…”

“…To use liquid metal as a conductive tuning element, enclosed fluidic channels are used to guide the metal and define its shape and range of motion. The liquid metal can be actuated by pressure either hydraulically or pneumatically within these channels [25,27,30,[46][47][48], however, Galinstan and other gallium-based alloys develop an oxide film in the presence of oxygen in concentrations as low as 1 ppm [14]. This oxide film adheres to channel walls and impedes motion of the liquid metal.…”

A microfluidically-tuned dual-band slot antenna

“…The use of fluidic metal in tunable/switchable antennas has attracted much attention recently [1][2][3]. In [1], a stretchable fluidic dipole is presented in which the frequency of the antenna can be tuned by stretching the PDMS structure.…”

“…Although, the frequency is shifted up using a design based on shortening the slot, another mode is also excited by the fluid metal switch appearing at 3.84 GHz. In [3], a reconfigurable patch antenna is proposed in which a PDMS structure is used to reshape the antenna by adding an extension of metal to the patch antenna. As a result, a frequency shift of 1.6-2.4 GHz is observed.…”

Magnetically‐ and Electrically‐Controllable Functional Liquid Metal Droplets

“…

including microelectromechanical (MEMS) actuators, [8][9][10][11][12] microscale heat exchangers, [13,14] soft and wearable electronics, [15][16][17][18][19] and reconfigurable structures. [20,21] Several techniques have been developed to control the motion and deformation of liquid metal droplets. Applying an external potential gradient is the most commonly used method to drive and deform liquid metal within electrolytes.

…”