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In this article, a VO2‐based tunable omnidirectional circularly polarized (CP) antenna is designed. The proposed antenna combines copper and metamaterial VO2. By utilizing the characteristics of insulator‐metal phase transition of VO2, we can change the length of the resonant branches to achieve tunable working bandwidth. The proposed antenna is composed of a modified floor loaded with VO2 and copper resonant branches, a top patch with slits, and 14 shorting vias connecting the top path and bottom floor. Different from the traditional electric controlled antennas, antennas based on metamaterial VO2 do not need to design complicated circuit structures and can be easily tailored by the external temperature (T). The simulated results illustrate that when T ≥ 68°C (state I), the proposed antenna has a 10‐dB impedance bandwidth of 15.9% (2.09‐2.45 GHz), and a 3‐dB axial ratio (AR) bandwidth of 23.4% (2.04‐2.58 GHz). When T < 68°C (state II), it has a bandwidth of 6.5% (2.38‐2.54 GHz) with S11 below −10 dB, and a bandwidth of 19.9% (2.39‐2.92 GHz) with AR below 3 dB. [ABSTRACT FROM AUTHOR]

In this article, a multilayer dielectric antenna with an air layer is used to realize a strain sensor, which can be utilized to measure the pressure. The springs are sandwiched between a parasitic plate and the designed antenna, where an air layer exists. The pressure can be measured by the relationship between the thickness of the air layer and the S‐parameter of the designed antenna. When the springs are deformed within a certain range, the center frequency of the designed antenna (S‐parameter is less than −10 dB) is correlated with the length of deformation, which can be marked by the thickness of the air layer between the parasitic patch and the antenna. The influence of the air layer thickness on the S‐parameter of this antenna is investigated. The results show that the deformation of the springs has an approximate linear relationship with the center frequency of return loss. The design provides a new idea about stress measurement. [ABSTRACT FROM AUTHOR]

In this article, a polarization reconfigurable omnidirectional antenna realized by the gravity field tailored is proposed, which is composed of the liquid metal Hg. The antenna is composed of four horizontal glass containers for omnidirectional horizontally polarized (HP) operating state (State I) and four tilted glass containers for omnidirectional circularly polarized (CP) working state (State II). By rotating the antenna, the position of Hg can be changed due to the effect of the gravity field, and different resonant structures can be formed to realize the regulation of polarization states between HP and CP working states. A reflector based on electromagnetic band gap (EBG) structure also is introduced, which can increase the gain and widen axial ratio (AR) bandwidth. The simulated results show that when the antenna is not rotated (State I), the 10‐dB impedance bandwidth is 21.2% (2.83~3.5 GHz). When the antenna is rotated (State II), the 10‐dB impedance bandwidth is 37.7% (2.35~3.44 GHz), and the 3‐dB AR bandwidth is 28.5% (2.35~3.13 GHz). After introducing the reflector, the max gain is increased to 2.1 dBic in State I and 2.2 dBic in State II, respectively. To further characterize the concept of the proposed antenna, a parametric study is carried out using HFSS. [ABSTRACT FROM AUTHOR]

In this article, a dual‐band and wideband omnidirectional circularly polarized (CP) antenna based on the vanadium dioxide (VO2) is investigated. The operating bandwidth of such an antenna can be regulated by altering the outside temperature (T), which is attained by the insulator‐metal transition of VO2. The omnidirectional CP antenna is based on a loop antenna‐dipole model, which is composed of four tilted metal and VO2 resonant units that are loaded around a cuboid and a feeding network for broadening bandwidth. The simulated results show that when T = 50°C (State I), the 10‐dB impedance bandwidth is 45.7% (1.67‐2.66 GHz), and the 3‐dB axial ratio (AR) bandwidth is 40% (1.9‐2.85 GHz). When T = 80°C (State II), the 10‐dB impedance bandwidth is 13.8% (1.62‐1.86 GHz), and the 3‐dB AR bandwidth is 21.8% (1.68‐2.09 GHz). In order to further characterize the concept of the proposed antenna, the related parameters of such an antenna are studied using simulation software HFSS. [ABSTRACT FROM AUTHOR]

In this article, a tunable wideband omnidirectional circularly polarized (CP) antenna regulated by the gravity field based on the liquid metal Hg is investigated. Under the action of the gravity field, Hg flows in the upper and lower parts by rotating such an antenna, which can constitute dissimilar resonant units to achieve the dynamic regulation of the operating bandwidths. The proposed antenna consists of four tilted glass containers that are filled with Hg in the upper or lower parts, and a feeding structure for power distribution and impedance matching. To verify concept of the design, equivalent prototypes have been fabricated and measured. The measured results are roughly consistent with simulated results within a reasonable error range. The antenna has a 10‐dB impedance bandwidth of 44.3% (2.37‐3.72 GHz), and a 3‐dB axial ratio (AR) bandwidth of 18.9% (2.83‐3.42 GHz) when the proposed antenna is not rotated (state I). When such an antenna is rotated (state II), it has a bandwidth of 40.7% (2.35‐3.55 GHz) with S11 below −10 dB, and a bandwidth of 22.9% (2.40‐3.02 GHz) with AR below 3 dB. Therefore, the operating band of the antenna can be altered between two wide bands. The proposed antenna has the advantages of tunable bandwidth, novel efficient regulation mechanism, and simple structure. [ABSTRACT FROM AUTHOR]

In this article, a tailored coplanar waveguide (CPW) circularly polarized (CP) antenna is designed, whose operating band can be adjusted in a large range by the gravity field through rotating the antenna vertically. Due to the fluidity of liquid metal mercury, which is packaged in the antenna's glass containers, when the antenna is rotated, mercury will lead to different metal resonant units in different directions under the influence of gravity. This antenna utilizes CPW whose metal reflective surface and the main radiating patch are on the same side of the dielectric substrate. The dielectric substrate is made of FR4, and the metal radiation patch and the metal reflective ground are made of copper. Two metal branches separated from the main radiation patch are connected to the main radiating patch by a glass container. To verify concept of the design, equivalent prototypes have been fabricated and measured. The measured results are roughly consistent with simulated results within a reasonable error range. The measured results show that when the antenna turns 90° counterclockwise along the x‐axis (state I), the 10‐dB return loss bandwidth is 13.5% (4.54~5.2 GHz), and the 3‐dB axial ratio (AR) bandwidth is 13.8% (4.5~5.17 GHz). When the antenna turns 90°clockwise along the x‐axis (state II), the 10‐dB return loss bandwidth is 23% (3.73~4.7 GHz), and the 3‐dB AR bandwidth is 23% (3.73~4.7 GHz) within the antenna operating range. In the cases of two different working states, the proposed antenna can effectively cover the 5G communication band. [ABSTRACT FROM AUTHOR]