Two‐octave tunable liquid‐metal monopole antenna

Abstract

Liquid metal is used to tune the operational frequency of a monopole antenna by adjusting its length. The centre frequency can be continuously tuned over two octaves, 2.0-9.5 GHz, while maintaining a gain of ∼5.2 dBi.Introduction: Previously demonstrated frequency-reconfigurable monopole antennas used reactive loading and switching, which provided preset discrete tuning states and tuning bandwidths typically less than an octave [1-3]. One design was tunable over two octaves, but showed degradation in its radiation pattern at higher frequencies [4]. This Letter presents a quarter-wave monopole antenna that can reconfigure its operational frequency over two octaves while maintaining a radiation pattern close to that of an ideal monopole, by using a liquid-metal radiating element whose length physically changes; this allows continuous, rather than discrete tunability compared with the cited work above. Recently, liquid metals have been implemented in a variety of microwave components such as switches [5], tuners [6], resonators [7], filters [8,9] and antennas [10][11][12][13].

Stretchable and Soft Electronics using Liquid Metals

“…The spectral properties of an antenna are a function of its shape; thus the ability to both physically deform and manipulate the shape of liquid metal offers unique possibilities for tunable and reconfigurable antennas. Liquid metal injected into microchannels has been utilized to make many types of antennas including dipoles ( Figure a,b), loops (Figure c), coils and inductors (Figure d), patch antennas (Figure e), radio‐frequency antennas (Figure f), spherical caps, phase shifting coaxial transmission lines, monopoles, and reconfigurable antennas and filters . There are many more examples that utilize Hg.…”

Low-Cost Rapid Fabrication of Conformal Liquid-Metal Patterns

“…An unstretched LM loop antenna had a radiation efficiency of 98% [23]. The gain of an LM monopole antenna was 5.10 to 5.26 dBi [24], matching the gain of a standard monopole (5.17 dBi). An embedded vascular LM dipole antenna had nearly identical radiation patterns as a Cu dipole antenna [25], and a helical LM antenna had the same gain as the Cu version of the antenna [26].…”

Frequency-Reconfigurable Dipole Antenna Using Liquid-Metal Pixels

“…Recent demonstrations in liquid-metal reconfigurable antennas include monopole [6,7], dipole [8], planar inverted F [9], Yagi-Uda [10][11][12], patch [13,14], and slot [15] antennas. Reconfigurability is achieved either by altering the physical dimensions of the radiating element with liquid metal or by configuring an associated liquid-metal parasitic element.…”