RESUMEN
A wideband superdirective array, composed of a two-element circular monopole configuration, is introduced. The monopoles are placed in close proximity, facing each other on a metal ground. To ensure good matching at high frequencies, two pairs of elliptical patches are added to the sides of the monopoles, enhancing the surface current of the circular patch for wideband performance. To achieve equal amplitude excitation and the desired phase difference, a wideband power divider with a phase shifter is designed to feed the antenna array. Simulation and measurement results demonstrate that the proposed wideband antenna array, operating within the frequency range of 2.94-7.93 GHz, exhibits a maximum directivity of 8.36-10 dBi, with an antenna efficiency ranging from 47.86 to 83.18% across the bandwidth. The proposed array has the advantages of miniaturization, high directivity and wideband operation and can be widely used in various portable wireless communication systems, including WLAN (5.05-5.9 GHz), ISM (5.725-5.875 GHz), 5G communication (3.3-3.8 GHz), etc.
RESUMEN
A wearable antenna functioning in the 2.4 GHz band for health monitoring and sensing is proposed. It is a circularly polarized (CP) patch antenna made from textiles. Despite its low profile (3.34 mm thickness, 0.027 λ0), an enhanced 3-dB axial ratio (AR) bandwidth is achieved by introducing slit-loaded parasitic elements on top of analysis and observations within the framework of Characteristic Mode Analysis (CMA). In detail, the parasitic elements introduce higher-order modes at high frequencies that may contribute to the 3-dB AR bandwidth enhancement. More importantly, additional slit loading is investigated to preserve the higher-order modes while relaxing strong capacitive coupling invoked by the low-profile structure and the parasitic elements. As a result, unlike conventional multilayer designs, a simple single-substrate, low-profile, and low-cost structure is achieved. While compared to traditional low-profile antennas, a significantly widened CP bandwidth is realized. These merits are important for the future massive application. The realized CP bandwidth is 2.2-2.54 GHz (14.3%), which is 3-5 times that of traditional low-profile designs (thickness < 4 mm, 0.04 λ0). A prototype was fabricated and measured with good results.
RESUMEN
The development of wearable/stretchable electronics could largely benefit from advanced stretchable antennas with excellent on-body performance upon mechanical deformations. Despite recent developments of stretchable antennas based on intrinsically stretchable conductors, they are often affected by lossy human tissues and exhibit resonant frequency shifts upon stretching, preventing their applications in on-body wireless communication and powering. This work reports a three-dimensional (3D) stretchable wideband dipole antenna from mechanical assembly to simultaneously reduce the frequency detuning and enhance on-body performance. The large bandwidth is achieved by coupling two resonances from two pairs of radiation arms, which is well-maintained even when the antenna is directly placed on human bodies or stretched over 25%. Such an excellent on-body performance allows the antenna to robustly transmit the wireless data and energy. The design of the 3D stretchable wideband dipole antenna with significantly enhanced on-body wireless communication performance was validated by an experimental demonstration that features a small difference in the wirelessly received power between the on-body and off-body use. The combination of the mechanically assembled 3D geometries and the coupled mechanical-electromagnetic properties can open up new opportunities in deformable 3D antennas and other microwave devices with excellent on-body performance and tunable properties.
RESUMEN
As the key component of wireless data transmission and powering, stretchable antennas play an indispensable role in flexible/stretchable electronics. However, they often suffer from frequency detuning upon mechanical deformations; thus, their applications are limited to wireless sensing with wireless transmission capabilities remaining elusive. Here, a hierarchically structured stretchable microstrip antenna with meshed patterns arranged in an arched shape showcases tunable resonance frequency upon deformations with improved overall stretchability. The almost unchanged resonance frequency during deformations enables robust on-body wireless communication and RF energy harvesting, whereas the rapid changing resonance frequency with deformations allows for wireless sensing. The proposed stretchable microstrip antenna was demonstrated to communicate wirelessly with a transmitter (input power of - 3 dBm) efficiently (i.e., the receiving power higher than - 100 dBm over a distance of 100 m) on human bodies even upon 25% stretching. The flexibility in structural engineering combined with the coupled mechanical-electromagnetic simulations, provides a versatile engineering toolkit to design stretchable microstrip antennas and other potential wireless devices for stretchable electronics.
RESUMEN
The ultimate application of bio-integrated, stretchable electronics hinges on the indispensable modules of stretchable wireless data transmission and power supplies. While radiofrequency (RF) antennas and rectennas could enable wireless communication and RF energy harvesting in the far-field, their performance deteriorates because of the frequency detuning from mechanical deformations. Here, stretchable wideband antennas and rectennas are introduced to robustly operate and combine received RF power over their wideband upon mechanical deformations. Devices with stretchable wideband antennas and rectennas create application opportunities such as self-powered systems, remote monitoring of the environment, and clean energy. A comprehensive set of manufacturing schemes, device components, and theoretical design tools for the stretchable wideband antennas and rectennas is reported. A stretchable wideband rectenna integrated with various functional sensing modules and its demonstration with enhanced effective rectenna efficiency over the state-of-the-art by 10-100 times illustrates a system-level example of this technology.