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Abstract Intelligent soft robotics and wearable electronics require flexible, wireless radio frequency (RF) pressure sensors for human‐like tactile perception of their moving parts. Existing devices face two challenges for array extension: the construction of sensitive units over a limited area and the handling of resonant peaks overlapping within the channel width. Herein, a simply adjustable RF‐resonator‐based tactile array (RFTA) is reported, in which the initial frequency of each resonator unit is regulated by doping polydimethylsiloxane (PDMS) dielectric layers with various concentrations of multiwalled carbon nanotubes (MWCNTs). An array is constructed using four sensor units with a frequency interval of 15 MHz and a multi‐layer micropyramid structure is employed to obtain a low detection limit (

Flexible pressure sensors have been widely applied in wearable devices, e-skin, and the new generation of robots. However, most of the current sensors use connecting wires for energy supply and signal transmission, which presents an obstacle for application scenarios requiring long endurance and large movement, especially. Flexible sensors combined with wireless technology is a promising research field for realizing efficient state sensing in an active state. Here, we designed and fabricated a soft wireless passive pressure sensor, with a fully flexible Ecoflex substrate and a multi-walled carbon nanotube/polydimethylsiloxane (MWCNT/PDMS) bilayer pyramid dielectric structure. Based on the principle of the radio-frequency resonator, the device achieved pressure sensing with a changeable capacitance. Subsequently, the effect of the pyramid density was simulated by the finite element method to improve the sensitivity. With one-step embossing and spin-coating methods, the fabricated sensor had an optimized sensitivity of 14.25 MHz/kPa in the low-pressure range. The sensor exhibited the potential for application in limb bending monitoring, thus demonstrating its value for long-term wireless clinical monitoring. Moreover, the radio frequency coupling field can be affected by approaching objects, which provides a possible route for realizing non-contact sensing in applications such as pre-collision warning.

Continuous monitoring of physical motion, which can be successfully achieved via a wireless flexible wearable electronic device, is essential for people to ensure the appropriate level of exercise. Currently, most of the flexible LC pressure sensors have low sensitivity because of the high Young’s modulus of the dielectric properties (such as PDMS) and the inflexible polymer films (as the substrate of the sensors), which don’t have excellent stretchability to conform to arbitrarily curved and moving surfaces such as joints. In the LC sensing system, the metal rings, as the traditional readout device, are difficult to meet the needs of the portable readout device for the integrated and planar readout antenna. In order to improve the pressure sensitivity of the sensor, the Ecoflex microcolumn used as the dielectric of the capacitive pressure sensor was prepared by using a metal mold copying method. The Ecoflex elastomer substrates enhanced the levels of conformability, which offered improved capabilities to establish intimate contact with the curved and moving surfaces of the skin. The pressure was applied to the sensor by weights, and the resonance frequency curves of the sensor under different pressures were obtained by the readout device connected to the vector network analyzer. The experimental results show that resonant frequency decreases linearly with the increase of applied pressure in a range of 0–23,760 Pa with a high sensitivity of −2.2 MHz/KPa. We designed a coplanar waveguide-fed monopole antenna used to read the information of the LC sensor, which has the potential to be integrated with RF signal processing circuits as a portable readout device and a higher vertical readout distance (up to 4 cm) than the copper ring. The flexible LC pressure sensor can be attached to the skin conformally and is sensitive to limb bending and facial muscle movements. Therefore, it has the potential to be integrated as a body sensor network that can be used to monitor physical motion.

This paper presents the design of a low-profile circularly polarized dual-beam holographic antenna. Firstly, by employing a novel outer square inner circular (OSIC) structure as the basic unit of the hologram pattern, better performance is achieved for lowprofile dielectric substrate holographic antennas. Secondly, a method of four-zone phase co-modulation is used to derive the impedance modulation formula of the hologram pattern. This formula was employed to model and generate a circularly polarized dual-beam holographic antenna, and the feasibility of theoretical analysis is verified through simulation and measurement. The antenna operates within the frequency range of 10.23 GHz to 16.59 GHz, with maximum gains of 16 dBi and 15.8 dBi for dual beams, respectively. The results indicate that this design method can realize circularly polarized dual-beam holographic antennas and provide some reference for satellite communication applications. [ABSTRACT FROM AUTHOR]

This study introduces a metasurface-based low-profile circularly polarized (CP) antenna with double-wide beam for global navigation satellite systems (GNSSs), which covers primarily BDS-2 B1 band and BDS-3 B1 band. At first, a T-slot structure achieving a compact design is presented to effectively miniaturize the antenna. Except that, a gear-type parasitic ring and eight parasitic microstrip lines are proposed to broaden both the half power beamwidth (HPBW) and axial ratio beamwidth (ARBW) of the antenna. Furthermore, a metasurface unit featuring double "WIFI" logo structure is introduced. This unit is expanded into a 7 * 7 metasurface loaded under the antenna, significantly improving its radiation characteristics. After experimentation, the proposed antenna achieves notable results: 121° HPBW and 214° 3 dB-ARBW at 1.561 GHz and 121° HPBW and 236° 3 dB-ARBW at 1.575 GHz. Additionally, it demonstrates more than 3.52 dBic gain across the whole frequency band, whose simulation and test results are in agreement. These results show that the antenna can be used for various satellite communication systems necessitating CP antennas with wide ARBW and HPBW. [ABSTRACT FROM AUTHOR]

In this paper, a new UWB antenna for the Internet of Things (IoT) based on a left-handed structure is designed. The antenna utilizes a microstrip feeder and consists of a new complementary split ring resonator (CSRR) equipped with a three-stage double rectangular electromagnetic resonator (RER) to form the main radiator with left-handed characteristics. It also includes a double L-shaped parasitic patch and a slotted ground. The dimensions of the antenna are 0.42 × 0.42 × 0.013λ0³. It covers the frequency band of 1.70-3.34 GHz (65.1%), which includes the communication frequency bands used by IoT antennas. The antenna exhibits good directional patterns within this frequency band. The measured peak gain is 5.49 dBi, making it suitable for applications in Wi-Fi, Bluetooth, Zigbee technology, and other fields. [ABSTRACT FROM AUTHOR]

In this paper, a new type of defected ground structure (DGS) antenna based on metamaterial is presented. The proposed antenna has the performance of global bandwidth and gain improvements. The miniaturization of the antenna can be achieved by loading metamaterials on the DGS antenna to reduce the resonance frequency of the antenna. Due to the coupling effect between the metamaterial and the DGS, multiple resonant points are generated, thus extending the impedance bandwidth of the antenna. The impedance bandwidth of the proposed antenna ranges from 3.5 GHz to 6.32 GHz (56.6%). The degree of miniaturization is 37.9%, and the measured peak gain is 4.5 dBi. The dimension of the antenna is only 0.35≥0x0:35≥0x0:011≥0, which has a highly stable antenna efficiency of greater than 90% over the entire operating bandwidth. The proposed antenna is suitable for WLAN and Bluetooth applications. [ABSTRACT FROM AUTHOR]

In this paper, a low-profile dual circularly polarized (CP) antenna for Ku band satellite communication is proposed. A quarter-mode SIW (QMSIW) is designed as a circular polarization unit, which realizes circular polarization by using high-order mode TE130, and a pair of units are combined to form the antenna proposed in this paper. Feeding different units can realize left-handed circular polarization and right-handed circular polarization, respectively. The antenna impedance bandwidth is 5.66 GHz (15.16 GHz{20.82 GHz); the circular polarization bandwidth (CPBW) is 540MHz (15.64 GHz{ 16.18 GHz); and the gain in the passband is 5.1 dBi, with a minimum axial ratio (AR) of 1 dB. The thickness of the antenna is only 1.5 mm, which has obvious low-profile characteristics. [ABSTRACT FROM AUTHOR]

In this paper, a novel dual-frequency circularly polarized (CP) antenna applied to Beidou satellite (BDS) system is presented. CP radiation is achieved by etching slotted circular patches of complementary open-loop resonators, which are excited by a feeding network consisting of a doublelayer power divider. The circular patch is miniaturized by a complementary split-ring resonator (CSRR) etched on the patch. The overall dimension of the antenna is only 0.32λ0 × 0.32λ0 × 0.0104λ0, where λ0 is the corresponding free space wavelength at 1.268 GHz. The proposed antenna has 70 MHz (1.23– 1.30 GHz) and 60 MHz (1.51–1.57 GHz) impedance bandwidth and 20 MHz (1.25–1.27 GHz) and 20 MHz (1.55–1.57 GHz) axial ratio bandwidth, respectively. The antenna profile is low, which is easy to install. Because of these performance indexes, the antenna has superior practicability in BDS system. [ABSTRACT FROM AUTHOR]

A novel low-profile GNSS microstrip circular polarization antenna is proposed and analyzed. Circular polarization is realized by asymmetric structure patch, and an arc structure loaded on the main radiator can keep two modes orthogonal over a wide-angle range, so that the antenna has an extremely wide 3 dB axial ratio beamwidth (ARBW). The far-field AR beamwidths obtained are 232° and 212° respectively in the main plane of φ = 0° and φ = 90°. In φ = 45° and φ = 135°, 3 dB AR beamwidths are 241° and 244°, far exceeding the 120° required for satellite applications. In the whole CP band, 78.95% of the beam width exceeds 180°. The profile is only 0.0156λ0, which is suitable, especially, for portable wireless systems or devices. The return loss bandwidth of -10 dB is 5.13% (1.52 GHz-1.6 GHz), which covers BeiDou Navigation System B1 (1.561 GHz). The axial ratio bandwidth is 1.28% (1.55 GHz-1.57 GHz), and the in-band peak gain is 4.09 dBi. [ABSTRACT FROM AUTHOR]

A wideband and widebeam magneto-electric (ME) dipole antenna is designed in this paper. Based on the conventional magneto-electric dipole antenna, a bent vertical metal plate is added to the electric dipole, and the impedance bandwidth (IBW) and beamwidth of the antenna are widened together. Inclined metal walls are added on both sides of the metal ground to improve the gain at high frequency and make the antenna gain more steady in the operating bandwidth. To further broaden the IBW of the antenna, the conventional Γ-shaped feed is changed into a branch structure. The IBW of the finally designed antenna reaches 56.8% (2.91{5.22 GHz). In the whole operational bandwidth, the radiation pattern in E-plane realizes the half power beamwidth (HPBW) of more than 110°, and the H-plane radiation pattern realizes the HPBW of more than 160°. The maximum width of E-plane HPBW is 175°, and the maximum width of H-plane HPBW is 229°. [ABSTRACT FROM AUTHOR]