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This paper presents a multi-field coupling model for magnetoelectric (ME) antennas, encompassing a ME film, electrode layers, and a substrate featuring a cavity structure. This model accounts for the nonlinear magnetoelastic coupling within the radiation layer and employs a combined DC and AC simulation methodology to capture the antenna's radiation mechanism. Leveraging this multi-field coupling model, performance differences between the ME antenna and an ideal ME composite film are analyzed. By exploring optimization schemes based on multi-physics fields, electrode materials, and structural design, the ME antenna's radiation performance is significantly enhanced. The findings demonstrate that the complete antenna structure, with its increased thickness and cavity design, exhibits a lower resonance frequency and a higher converse ME (CME) coefficient compared to the ideal ME film. The optimal CME effect is achieved under proper external stimuli, leading to a broader 3 dB bandwidth. Expanding the cavity dimensions enhances the CME coefficient by 42% and reduces the resonance frequency due to decreased acoustic wave loss. Adopting electrode materials with higher acoustic impedance elevates the CME coefficient, yet narrows the bandwidth. Conversely, using silver (Ag) electrodes promotes a broader bandwidth. Additionally, ME antenna arrays are designed to broaden the bandwidth by 300%. [ABSTRACT FROM AUTHOR]

A flexible conducting lossy shield is developed and demonstrated for a reduction in the back radiation of a linearly polarized X-band patch antenna for Wireless Body Area Network (WBAN) applications. The proposed structure comprises a flexible patch antenna backed by a laminated sheet of Expanded Graphite (EG). This flexible sheet is prepared from EG powder pressed uniformly over a thin adhesive tape. The conducting nature of EG is exploited, and the EG sheet is used as a protective shield to prevent back radiation emanating out of the WBAN antenna from propagating toward the human body. The antenna performance is tested over human wrist phantoms experimentally and through full wave simulation studies. The results indicate the marginal variation in the −10 dB impedance bandwidth with a slight increase in the gain and directivity values for a resonant frequency in the range 9.7–10.3 GHz (bending radius variation of 40, 30, and 20 mm and along two bending planes). A measured on-body gain of 6.7 dBi is exhibited by the antenna backed by the EG shield and bent over a 20 mm radius human wrist phantom with an S11 of −19 dB, a −10 dB % bandwidth of 8%, and a directivity of 9.4 dBi. All the other bending configurations exhibit values higher than these. Electric field and Specific Absorption Rate (SAR) studies reveal a reduction in wave penetration by the EG shield antenna inside the wrist phantom with a decrease in the SAR by a maximum of 5%. The measured front-to-back ratio values indicate the lowering of back radiation with a maximum average increase of 76% exhibited by an EG backed antenna. The developed EG shield has an additional advantage of being a standalone structure, which can be integrated with any wearable antenna for a possible reduction in the back radiation. [ABSTRACT FROM AUTHOR]

Antennas operating at the high-frequency (HF) band (3–30 MHz) are frequently electrically small due to the large wavelength of electromagnetic waves (10–100 m). However, the bandwidth-efficiency products of passively matched electrically small antennas (ESAs) are fundamentally limited. Wideband HF waveforms using bandwidths of 24 kHz or more have recently received significant attention in military communications applications. Efficiently radiating such signals from conventional passive ESAs is very challenging due to fundamental physical limits on bandwidth-efficiency products of ESAs. However, active antennas are not subject to the same constraints. In this work, we present the design and experimental characterization of a high-power, class-E active ESA with enhanced bandwidth-efficiency product compared to that of passively matched ESAs. Specifically, the proposed class-E active ESA can radiate wideband HF signals with bandwidths of 24 kHz or more at 3 MHz (fractional bandwidths of ≈ 1 % – 4 %), with total efficiencies ranging from 40 % up to 80 % depending on the modulation type and radiated power levels approaching 100 W. Our approach uses a highly efficient, integrated class-E switching circuit specifically designed to drive an electrically small, high-Q HF antenna over a bandwidth exceeding 24 kHz at 3 MHz. Using a high-Q RLC antenna model, we have successfully demonstrated wideband binary ASK, PSK, and FSK modulations with the proposed class-E active ESA. Experimental results indicate that the bandwidth-efficiency product of this class-E active ESA is 5.4–9.8 dB higher than that of an equivalent passive design with the same data rate and bit-error-rate. [ABSTRACT FROM AUTHOR]

In this paper, a wideband metasurface-loaded (MTS-L) rectenna system is proposed to capture electromagnetic (EM) energy at arbitrary azimuth angles. The radiation patterns of different modes in the original MTS configuration are analyzed using the characteristic mode theory, and potential modes with omnidirectional radiation are screened out. By the arrangement of patches, the roundness performance of the radiation pattern can be ameliorated, and the omnidirectional characteristic is obtained over a wide frequency band. Subsequently, the surface current density of the selected mode is carefully and artificially designed to facilitate probe excitation as well as refrain from introducing complex power-combining networks. A wideband rectifier circuit is designed as the load of the proposed antenna. Eventually, measured results show that it operates from 4.6 to 9.6 GHz with a fractional bandwidth of 70.4%, and the peak system efficiency is 52.2%. The proposed system demonstrates excellent potential for wireless power transmission and EM energy harvesting in indoor environments. [ABSTRACT FROM AUTHOR]

In this paper, a wideband polarization reconfigurable omnidirectional antenna (PROA) based on a single-substrate active metasurface is proposed. By controlling the states of the PIN diodes, the antenna can selectively radiate an omnidirectional linearly polarized wave and an omnidirectional circularly polarized wave. The reflection coefficient, axial ratio (AR), radiation pattern, and gain of the proposed antenna have been analyzed from the perspective of simulation and measurement. The measured results show that the PROA has a wide overlapped bandwidth from 2.87 to 3.67 GHz (relative bandwidth 24.46%). To the authors' best knowledge, this is the first reported wideband PROA based on a single-substrate reconfigurable polarization converter. This study not only offers a novel approach to design PROAs, but also greatly reduces the design complexity of the feed source compared with the traditional design method of PROAs. [ABSTRACT FROM AUTHOR]

Electromagnetic metasurfaces can achieve effective control of electromagnetic waves and achieve effects such as blocking, enhancing, reflecting, transmitting, or deflecting electromagnetic waves, possessing electromagnetic properties that go beyond traditional materials. Existing research indicates that the dielectric substrate of metasurfaces has a significant impact on their electromagnetic properties. Increasing the substrate thickness will be beneficial for expanding the impedance bandwidth of the metasurface, and changes in dielectric constant will also have some impact on the operating frequency and bandwidth of the metasurface. A metasurface based on an air substrate was proposed through the research of dielectric materials. In addition, an ultrawideband, miniaturized, and high-gain metasurface antenna based on an air substrate is designed. The overall size of the designed antenna is 0.5λL × 0.5λL (where λL represents the wavelength at the lowest working frequency in free space). The measured results indicate that the proposed antenna exhibits a −10 dB impedance bandwidth of 74.3% (2.53–5.52 GHz) and a peak boresight gain of 10.1 dBi. [ABSTRACT FROM AUTHOR]

We propose a multi-feed Huygens' metasurface (HMS) transmitarray designed for microwave power transmission applications. A near-field distributed optimization mechanism is employed to determine the optimal focal lengths of subarrays. We aim to balance between illumination efficiency and interference from incident waves, leveraging the conjugate field matching method for precise phase compensation. This approach ensures robust radiation performance, notably reducing the focus-to-diameter ratio for large-aperture antenna arrays. Consequently, it mitigates spatial dispersion effects and upholds the operational bandwidth of mega antennas. As a proof of concept, we have designed a single-layer HMS transmitarray measuring 1.14 × 1.14 m2 (22 λ at 5.8 GHz). Through simulation, we have attained a peak gain of 35.47 dB and an aperture efficiency of 57.73%. Our design exhibits outstanding radiation performance, combined with advantages, such as a low profile, cost-effectiveness, and scalability. [ABSTRACT FROM AUTHOR]

Plasmon-mechanical resonators are frequently employed in sensor development. Here, I report the coupling of plasmon and mechanical modes in a multilayer architecture. In the experiment, the multilayer comprised indium tin oxide (ITO) and silver (Ag) mirrors placed on the top and bottom of a SiO2 substrate. By activating a Fabry–Pérot hybrid mode and surface plasmon polariton in a Kretschmann configuration, I demonstrated the generation of a hybrid plasmon-mechanical mode by plasmonic dispersion and through strong coupling, which resulted in mechanical distortion at multiple frequencies. Adsorption of rhodamine G6 on Ag modifies the optomechanical spectrum; it causes eigenmodes to split, resulting in a coupling rate greater than the optical decay rate (κ ∗ < g). Besides, the excitonic modes were observed to interact with plasmon-mechanical modes, especially on-resonance, where the plasmon-mechanical modes exhibited the higher intensity. For example, the out-of-phase flexural mode (iii, g 0 = 427 × 2 π kHz) became active because of the coupling of the dye. Meanwhile, after dye absorption, the strong in-phase compressional mode (iv, g 0 = 560 × 2 π kHz) exhibited the widest splitting and an increase in the side peaks, which merged when the pump power was raised. The system was then analyzed to determine the ideal experimental settings for detecting mass by the oscillator in a controlled experiment. The mass sensor responsivity was evaluated to be F = 10 17 Hz g − 1 . Advantages and disadvantages of this approach are presented. [ABSTRACT FROM AUTHOR]

Scientific research has shown that the geometric structure of the metasurface has a significant impact on its ability to control the propagation of electromagnetic waves. The control of surface current can be achieved by designing the shape of the metasurface unit cell. In this paper, the traditional metasurface is studied using characteristic mode analysis, and a modified metasurface is proposed, which consists of 4 × 4 hexagonal rings with an asymmetric concave interior. The modified metasurface controls the distribution of surface current by increasing the path of surface current, thus lowering the frequency of modal significance. In addition, due to the special asymmetric concave interior, the frequency difference of different modal currents increases, leading to the expansion of the operating bandwidth of modal currents. A metasurface antenna is fabricated and measured for proof of concept. With a size of 0.69λL × 0.69λL × 0.06λL (λL is the wavelength in free space at the lowest operating frequency), the designed antenna achieves a −10 dB impedance band of 40%, 3 dB axial ratio band of 19.4%, and boresight gain of 8 dBi. [ABSTRACT FROM AUTHOR]

Unlike popular multiband antenna array radiation based on either electric or magnetic surface currents, the use of mutually interleaved and tightly coupled electric and magnetic currents results in an aperture-reuse space-efficient multiband radiating surface for highly integrated antenna-frontend architecture and spatial power combining design scenarios. In this work, slot and dipole modes corresponding to magnetic and electric currents are effectively interleaved and excited in a surface to develop a space-efficient dual-wideband aperture-shared radiating surface. In this case, due to an effective reuse of the antenna aperture over both frequency bands, a high aperture-reuse efficiency is achieved. First, we devise a planar magneto-electric (ME)-dipole-alike antenna and analyze it in both the frequency and time domain. The antenna is then studied by the characteristic mode theory and the findings are validated using full-wave simulations. The developed planar ME-dipole-alike antenna is used to realize a dual-wideband radiating surface in which electric and magnetic currents are mutually coupled and interlaced, which is excited by properly oriented and distributed sources on the antenna's surface. Eventually, a highly isolated dual-wideband prototype was developed and fabricated using a cost-effective multi-layer Printed Circuit Board (PCB) process that operates in the Ku-band with both impedance and gain bandwidth of approximately 42% and in the Ka-band with respective impedance and gain bandwidth of 29% and 16.32%. [ABSTRACT FROM AUTHOR]

This study investigates an axial extension mode magnetoelectric antenna designed for near-field communication in dielectric cluttered environments. The antenna configuration consists of two magnetostrictive Metglas-polymer composites bonded on opposite sides of a PZT-5A actuator, creating a dumbbell configuration. Operating at its 88 kHz mechanical resonance, the antenna emits electromagnetic radiation in the near field by applying an AC voltage to the piezoelectric material, generating an acoustic wave that propagates through the volume and induces oscillating magnetizations. The design uses a system of uncoupled models: an electrostatic finite element model to predict strain that feeds into a Landau–Lifshitz–Gilbert micromagnetic model to predict magnetic moment changes and, subsequently, a dipole model to forecast near-field radiation characteristics. Measurements were conducted on the antenna's impedance, quality factor, mechanical resonance, transmitted magnetic signal strength, and radiation patterns, with variations in the bias magnetic field, frequency, and applied voltage. The results exhibit a strong correlation with model predictions, and the radiated signal strengths compare favorably with those of state-of-the-art pacemaker communication devices. Computational parametric studies using Galfenol and Terfenol-D suggest the potential for up to a three order of magnitude reduction in the antenna's volume, which is critical for implanted medical devices. [ABSTRACT FROM AUTHOR]

We fabricated a photoconductive antenna (PCA) with Er-doped InAs quantum dot (QD) layers on a GaAs substrate and demonstrated THz wave generation with 1.5 μm pump. In terahertz time-domain spectroscopy (THz-TDS), PCAs require high mobility and short lifetimes of photocarriers since the carriers need to respond rapidly to optical pulses for broad THz generation and detection with a high time resolution. In this study, to achieve PCA operation at an optical communication wavelength band of 1.5 μm, a substrate for a PCA was fabricated using stacked Er-doped-InAs QD layers. Then, photocurrent measurements were performed to observe optical absorption in the 1.5 μm band. The results indicated the high capability of the PCA for THz wave generation and detection, in fact, which enabled us to generate the THz wave in the 1.5 μm band optical system. [ABSTRACT FROM AUTHOR]

Luneburg lens is traditionally a spherical dielectric with centro-symmetric and graded refractive index, which has been widely applied in civilian and military fields due to its outstanding abilities of focusing or collimating electromagnetic waves. However, the existing designs of Luneburg lens generally suffer from the disadvantages of bulkiness, complex fabrication process, and limited scanning angles, etc. Herein, a planar metasurface that could mimic the planar Luneburg lens is designed by utilizing the addition theorem. It has been experimentally verified that the Luneburg-like lens has large and continuous scanning angles from − 52 ° to 52° at a frequency of 10 GHz if an excitation antenna is moved along a straight line. Besides, the total thickness of the proposed lens is only 3 mm and it has the advantages of low cost, ease of fabrication, as well as being isolated from the feeder. As a result, the proposed Luneburg-like lens has great potential values of being flexibly applied in numerous fields. [ABSTRACT FROM AUTHOR]

This paper proposes analytical solutions for the resonant radiation performance of bending-mode magnetoelectric (ME) antennas. The strain-mediated Converse ME (CME) coupling model of bending-mode ME antennas is first established by solving nonlinear constitutive equations and bending governing equations using the elastic mechanics method. Then, the calculated magnetic flux and electric displacement are employed to propose a resonant radiation field model based on the dipole method. The numerical results for the CME coefficient show a good agreement with the experimental data. It can be observed that the volume fraction ratio of the piezoelectric layer can control the CME coefficient and radiation efficiency with the same variation trend since it can determine the bending strain via changing the location of the neutral layer of the ME antennas, which also demonstrates the strain-mediated essence of the ME antennas. In addition, the volume fraction ratio can tune the resonant frequency within a wide range. The gain of the ME antenna is stable and higher than −168 dB with the volume fraction ratio ranging from 0.2 to 0.7. The tensile stress and compressive stress have the opposite effect on the resonant frequency at low and high bias magnetic fields. Meanwhile, the tensile (compressive) stress is beneficial for both the radiation and gain in the low (high) bias field region. This model may facilitate the understanding of the bending-mode radiation mechanism of ME antennas and provide a basis for designing asymmetric ME antennas. [ABSTRACT FROM AUTHOR]

Absorption of electromagnetic (EM) wave has been widely studied and applied in EM, optics, and material research. By constructing an adaptive multi-mode absorption, an EM absorber approach that can be used in a variety of EM environments is provided in this research. This property demonstrates the absorber has an improved environment compatibility. It is used as an application example to address the issue that has recently come up in phased array research on the need to reduce the coupling between antenna elements in varied beam-scanning cases. After analyzing the electric and magnetic characteristics of a patch antenna array in different beam-scanning states, an absorber structure is constructed, with electric absorption in the sum beam case, magnetic absorption in the difference beam case, and combined electric-magnetic absorption in other beam scanning cases. The proposed method is systematically investigated and, finally validated by simulation and measurement evidently. In arbitrary beam-scanning states, the absorber exhibits good absorption and coupling reduction performance, while the radiation performance of the array is well maintained after introducing the absorber. This research can be used in absorber and coupling reduction studies, as well as, potentially in metamaterial and electromagnetic compatibility (EMC). [ABSTRACT FROM AUTHOR]

This paper proposes a circularly-polarized (CP) metasurface antenna with ultra-wideband radar cross section (RCS) reduction. Initially, the relationship between RCS reduction and phase difference with different reflection amplitudes is analyzed theoretically. Inspired by the shared-aperture principle, a high-frequency resistive layer is introduced into the antenna element to further fulfill ultra-wideband RCS reduction and low-profile requirements. Numerical simulations demonstrate that the inserted layer has no effect on the radiation performance of the antenna array. Then, the proposed element and its orthogonal unit are arranged in a checkerboard pattern for good CP radiation. In this configuration, the proposed metasurface array antenna has a maximum gain of 16.7 dBi with 72.1% aperture efficiency. The bandwidth of 5 dB RCS reduction with x- and y-polarized incidences is 7.10–17.95 GHz and 7.34–17.85 GHz, respectively. The proposed design is verified by the fabrication of prototype antennas and measurements. [ABSTRACT FROM AUTHOR]

The operating bandwidth of miniaturized magnetoelectric (ME) antenna is generally narrow due to the acoustic wave driven magneto-electromechanical resonance effect, parallel connection of multiple ME antennas with different resonant frequencies is an effective way to broaden the operating bandwidth of the antenna. This paper presents an ME antenna array consisting of three units, which are constructed of a sandwich stack of Metglas/Pb(Mg1/3Nb2/3)O3–PbTiO3/Metglas. The −3 dB operating bandwidth of 152.4–172.8 kHz is achieved, and the relative bandwidth is 12.5%. Experimental results indicated that the bias magnetic field and coupling effect between the ME antenna units significantly influence the performance of ME antenna array. A modified Butterworth–Van Dyke (MBVD) equivalent circuit model is used and improved to analyze the influence of sound waves, electric fields, magnetic fields, parasitic capacitance, and bias magnetic field on the ME antenna array. The simulation results of the MBVD equivalent circuit model are agreed well with the experimental results. The improved MBVD model is beneficial for the design of acoustic wave driven antenna array. [ABSTRACT FROM AUTHOR]

We propose a novel UV/Vis femtosecond spectroscopic technique, two-dimensional fluorescence-excitation (2D-FLEX) spectroscopy, which combines spectral resolution during the excitation process with exclusive monitoring of the excited-state system dynamics at high time and frequency resolution. We discuss the experimental feasibility and realizability of 2D-FLEX, develop the necessary theoretical framework, and demonstrate the high information content of this technique by simulating the 2D-FLEX spectra of a model four-level system and the Fenna–Matthews–Olson antenna complex. We show that the evolution of 2D-FLEX spectra with population time directly monitors energy transfer dynamics and can thus yield direct qualitative insight into the investigated system. This makes 2D-FLEX a highly efficient instrument for real-time monitoring of photophysical processes in polyatomic molecules and molecular aggregates. [ABSTRACT FROM AUTHOR]

Recently it is shown that sensitivity of biosensors can be considerably improved using single trap phenomena resulting in two‐level random telegraph signal (RTS) switching in current. To develop the transistor structure with a predefined trap position using gold antenna is suggested, which can be excited by light of different intensities to influence the properties of the underlying dielectric layer. High‐quality liquid gate‐all‐around (LGAA) silicon nanowire (NW) field‐effect transistor (FET) biosensors are fabricated with a gold bowtie antenna. The transport and noise properties of these new NW FETs are investigated at 940 nm LED excitation in a 1 mm phosphate‐buffered saline (PBS) solution with pH = 7.4. A strong sensitivity of I–V and noise characteristics is revealed with an increase in LED intensity. Well‐resolved Lorentzian components are only found under the influence of light excitation. A two‐level RTS is successfully excited with linear dependence of its amplitude versus intensity. In addition, repeatable fluctuations in current are resolved as small peaks in I–V curves under infrared illumination, thus confirming the excitation of a two‐level RTS in the biosensors. The results demonstrate that the FET devices with a gold antenna have significant potential for the excitation of two‐level signals to enhance the sensitivity of biosensors. [ABSTRACT FROM AUTHOR]

ABSTRACT A novel superstrate‐based Vivaldi antenna design characterized by high‐gain and wideband performance is presented. The proposed design configuration features a Vivaldi antenna positioned between high dielectric superstrate (Rogers 6010, εr = 10.2) with copper etched off on both sides and an FR4 substrate that has copper etched on one side only. The introduction of a high permittivity dielectric material above and a reflector below the Vivaldi antenna enables favorable resonance conditions for achieving high‐gain operation. The measured antenna exhibits a peak gain of 17 dBi at 10 GHz, covering an operating frequency range of 6–20 GHz. It also features a narrow half‐power beamwidth and low side lobe level radiation patterns. Unlike existing studies, which rely on metamaterials, electromagnetic bandgap structures, and frequency selective surfaces for gain enhancement, our design employs high‐dielectric constant superstrates. This approach increased the antenna's peak gain by 10 dB. Also, the proposed configuration act as a radome protecting the antenna from Environment. [ABSTRACT FROM AUTHOR]

Summary Wireless communication systems depend on channel state information (CSI). However, the CSI collection is a significant barrier to achieving high performance. Present wireless communication models mainly rely on many antennas and related signal dispensation for increasing effectiveness. User mobility, the usage of greater frequencies, and a better number of antennas contribute to beamforming and beam management in these networks. Therefore, an improved hybrid heuristic algorithm is proposed here for providing optimized Joint beam forming and antenna selection (JBAS) in a multi‐input multi‐output (MIMO) model. The major novelty of the research work is to jointly perform the beam forming and antenna selection in MIMO that effectively enhanced the performance of the wireless transmission system. The major intention of this paper is to optimize the beamforming vectors and antennae by using the designed algorithm, where the spectral efficiency gets maximized. Initially, the data is collected by varying the number of users, locations, and sampling points, which is optimally selected by developing the hybrid reptile search‐based lion optimization algorithm (HRS‐LOA). Once it is collected, the relevant CSI is considered. This state of information is fed as input to the Auto Encoder with Bayesian Recurrent Neural Network (AE‐BRNN). Finally, through the network, the optimized value of the beamforming vector and antenna is obtained, which is useful to increase the sum rate/spectral efficiency. From the numerical results, the recommended model attained a spectral efficiency of 30 bits/s/Hz, which is higher than the BWO‐AE‐BRNN with 13%, RSO‐AE‐BRNN with 16%, RSA‐AE‐BRNN with 17%, and LA‐AE‐BRNN with 40% respectively. [ABSTRACT FROM AUTHOR]

Two novel antennas are presented in this article. UWB and UWB antenna with triple notched band are designed using an elliptical array structure. To improve the gain and the impedance bandwidth, a new methodology for optimization of an elliptical array UWB antenna with an uncentered feedline model is presented. Based on the Response Surface Modelling, two parameters (Wopt1 and Wopt2) control the return loss of UWB antenna. The mathematical models of S11 is developed using non-regression analysis, and this antenna can be used for various applications such as Wi-Fi, 5 G, 4 G LTE, X-Band application, C-Band application. The band rejection technique is implemented to designed triple notched UWB antenna to reduce the cost of the UWB channel. The first band (2–3 GHz) is rejected by embedding a rectangular stub on the modified partial ground plane on UWB antenna. By etching a three rectangular slot on the elliptical array radiator, two notched bands 2–3 GHz and 5–6 GHz bands are rejected. By embedding two arcs on the elliptical array radiator, triple interfacing bands 2–3 GHz, 5–6 GHz, and 7.8–8.4 GHz are rejected. Two proposed antennas are designed using FR4 substrate and fabricated and verified experimentally. This antenna offers excellent performance and is well-suited for 5 G wireless communications. [ABSTRACT FROM AUTHOR]

Lanthanide‐doped upconversion nanoparticles (UCNPs) have attractive emission properties but suffer from weak light‐absorbing capacities and thereby relatively low brightnesses. This motivates using strongly absorbing dye molecules as antennas and sensitizers. However, despite much effort, understanding of this dye‐UCNP interplay is still limited. Major sensitization mechanisms are still under discussion, largely because there is a lack of effective means to observe key factors such as dark state transitions within the dyes. Here, a combined spectroscopic procedure is established to systematically investigate the photophysics behind the dye‐UCNP interaction, embracing fluorescence‐based transient‐state excitation‐modulation, lifetime and correlation spectroscopy, and spectrofluorometry/spectrophotometry. With this procedure the heptamethine cyanine dye IR806, a typical UCNP sensitizer is studied, its photophysical model is established, its photophysics in UCL‐sensitization‐related environments is deciphered, and the energy transfer from the IR806 singlet excited state to Yb3+ (UCNP sensitizer ion) can be identified as the dominant sensitization mechanism. These studies suggest that IR806 can form non‐emissive H‐aggregates at the nanoparticle surfaces, which can be dissociated after certain light excitation duration (typically>100 µs). Moreover, buildup of a non‐fluorescent, photo‐redox state of IR806 after longer irradiation times (10–100 ms) can deleteriously affect its UCL sensitization effect, inferring an optimal excitation duration for dye‐sensitized UCNPs, relevant for, e.g., optical imaging applications. [ABSTRACT FROM AUTHOR]

This article presents a planar Vivaldi array antenna based on a power divider structure. A half‐loop defected ground structure (DGS) is performed to decrease the mutual coupling between antennas in the bottom layer of the substrate. The proposed Vivaldi antenna has a 1 × 8 power divided microstrip line structure and performs well in antenna gain and beam directivity. To validate the design, the proposed high‐gain planar Vivaldi array antenna was manufactured, and the measured results were very similar to the simulated one. The size of the proposed antenna is 67 × 44 mm2, the application band is 25–27.3 GHz, and the measured peak gain is 12.6 dBi. The antenna is simulated with an electromagnetic power density (PD) of 28.5 W/m2 at 1 cm2 and 7.27 W/m2 at 4 cm2, which are in compliance with the FCC regulations. Therefore, this antenna is suitable for wearable devices and is applied to n257, n258, and n261. [ABSTRACT FROM AUTHOR]

Synthetic impulse and aperture radar (SIAR) is a technique that frequency diverse array (FDA) radars can imply in practice, thus overcoming some of their challenges. SIAR radars, used in various fields like transportation and defense, can detect the range, azimuth angle, elevation angle, and Doppler of the target with their 4D‐matched filter and a single receiver. However, the challenge of high‐amplitude sidelobes is a significant concern for researchers. They have attempted to reduce it through various approaches, including frequency code, range–angle coupling, and range–Doppler coupling, to accurately identify target characteristics. This paper presents the antenna place code (AP code) parameter as a significant factor in minimizing sidelobe amplitudes. The parameter specifies that, rather than having all antennas active, a certain number of antennas are active in each pulse repetition interval (PRI) to achieve a lower sidelobe. Researchers have found that using AP codes can effectively lower the amplitude of the range–angle sidelobe, the range–Doppler sidelobe, error coupling, the repetition of sidelobe strands, and the output of angle error for different target angles. All studies are conducted on a linear array for simplicity. The output of various AP codes is compared to the previously common uniform array. [ABSTRACT FROM AUTHOR]

A cutting-edge antenna system has been developed for new radio (NR) millimeter wave operating from 36.0 to 40.0 GHz frequency range 2 (FR 2) n260 band applications. This innovative system incorporates metasurface-inspired printed dual-port MIMO technology, which includes LP to CP conversion features. The positional orientation of the elements of the MIMO antenna with stacked metasurface provoked the spatial diversity. To convert linearly polarised (LP) waves to circularly polarised (CP) waves, the metasurface layer is suspended above the MIMO antenna. LP to CP polarisation conversion occurs when the conducting strip and rectangular space between strips on the substrate generate π/2 phase-shifted electric field components (Ex and Ey). The proposed stepped impedance-fed antenna elements and metasurface are fabricated on commercially available high-frequency laminates using a double-layer printed circuit board (PCB) fabrication facility. The test findings exhibit a satisfactory level of concurrence with the calculated/measured findings regarding scattering parameters, diversity performance parameters, and realized gain. The result is a highly efficient and versatile antenna system that is ideal for advanced engineering applications. [ABSTRACT FROM AUTHOR]

We demonstrate the generation of highly directive circularly polarized beams by proposing a meta-lens to calibrate the near fields over the holographic surface. Such a design possesses the merits of ultra-low profile as a lens system on the basis of phase compensation of a specific radiating aperture rather than the conventional consideration of the lens focus, and the ratio between the overall height of the antenna architecture and diameter of radiating aperture is only 0.09. Especially, the proposed meta-lens integrated holographic surface also offers a satisfactory solution to improve the overall efficiency of holographic antennas, and the experimental results verify the proposed design with 27.6 dBic measured gain and 40.4 % aperture efficiency at 15 GHz. We expect the proposed strategy of integrating phase compensation lens closely over the holographic surface, pave the way for highly efficient meta-radiators with ultra-low profile. [ABSTRACT FROM AUTHOR]

Smart earth station antennas have been used for several decades in many applications, from satellite communications to space object detection and tracking. The accuracy of the azimuth position for such antennas plays a crucial role in most steerable ground station antennas. Satellite tracking and space object detection demand precise tracking capabilities from the Earth. Several methods and techniques have been developed and used in industry to control the directions of ground station antennas, including the azimuth position. The challenge of azimuth tracking is increasing with the demand for full-sky coverage and with the exponential increase in space objects, including man-made satellites and operational and nonoperational objects; thus, providing accurate tracking is a key technology that demands continuous enhancement and development. This article presents the use of a PID-proportional-integral-derivative controller, a slide mode controller and a fractional order PID controller. It also introduces a new methodology based on model predictive control (MPC). The manuscript provides the core design for each of these controllers and provides insight into the performance of each controller even in the presence of disturbance. The camel optimization algorithm (COA) was used to obtain the optimal design parameters of each controller in the considered scenarios. [ABSTRACT FROM AUTHOR]

This paper proposes and analyzes a 2 × 2 multi‐input multioutput antenna based on an open‐loop resonator structure and an inverted L structure. The top layer of the antenna uses symmetric inverted hook‐shaped and inverted L branches and is connected to the bottom layer of the dual‐feed port and the ground plane using the VIAs, respectively. The open‐loop resonator structure at the bottom of the antenna and the top layer of the branched circuit are resonated to provide wide‐bandwidth and dual‐frequency characteristics. The substrate uses FR4 with an area of 40 × 30 × 0.8 mm3. Although the two antenna feed ports are very close to each other, using via to connect the defective bottom ground structure and the top inverted L‐shaped branch, the isolation still achieves an excellent performance of 15 dB. The antenna has multiband application characteristics, and the bands include 2.29–5.51, 6.14–10.26, 2.29–5.33, 5.19–6.64, and 6.78–10.16 GHz. In pattern and MIMO transmission efficiency measurement, the peak radiation efficiency is 89%, the peak gain is 8.5 dBi, and the ECC is less than 0.034. In the transmission efficiency measurement mode using 64‐QAM, watching the error vector magnitude at 2.56 and 5.11 GHz, the demodulation effect is very good, and the respective throughput results are 100% and 79.2%. The broadband characteristics of the antenna have a variety of applications, and it is simulated at the specific absorption rate, which meets the standards set by the Federal Communications Commission and is very suitable for use in wearable devices. The antenna can be applied to the X‐band, n77, n79, Sub‐6 GHz, WiMax, DSRC, WiFi 6, WiFi 6E, WiFi 7, C‐V2X, and C‐band. [ABSTRACT FROM AUTHOR]

The main and auxiliary radiating elements are linked by linear mathematical relation and coated with nanocomposite (NC) materials to enhance radiation characteristics. Nanocomposite-based electric material (NE) and nanocomposite-based magnetic material (NM) coated on auxiliary radiating elements to enhance the electromagnetic radiation of the proposed antenna. The radiating elements coated with NE graphene oxide (GO) and NM barium ferrite (BF) have higher electric field and magnetic field distribution respectively. The linear relation of main and auxiliary elements is verified by two substrates FR4, Teflon with correlated results. This proposed NC-coated antenna produces a bandwidth of 4.15 GHz, 4.02 dBi average gain and radiation efficiency of 95.17%, being superior to the antenna without NC coating. Fabricated antenna has 1.56–5.71 GHz bandwidth that includes 2.4/5.2 GHz WLAN, 2.5/3.5 GHz WiMAX, 2.4 GHz ISM, 5G SUB-6 GHz, 5G NR 78 and 2.4/5 GHz Wi-Fi bands. [ABSTRACT FROM AUTHOR]

SUMMARY Chlorophylls a and b (Chl a and b) are involved in light harvesting, photochemical reactions, and electron transfer reactions in plants and green algae. The core complexes of the photosystems (PSI and PSII) associate with Chl a, while the peripheral antenna complexes (LHCI and LHCII) bind Chls a and b. One of the final steps of Chl biosynthesis is the conversion of geranylgeranylated Chls (ChlsGG) to phytylated Chls by geranylgeranyl reductase (GGR). Here, we isolated and characterized a pale green mutant of the green alga Chlamydomonas reinhardtii that was very photosensitive and was unable to grow photoautotrophically. This mutant has a 16‐bp deletion in the LHL3 gene, which resulted in the loss of LHL3 and GGR and accumulated only ChlsGG. The lhl3 mutant cells grown in the dark accumulated PSII and PSI proteins at 25–50% of WT levels, lacked PSII activity, and retained a decreased PSI activity. The PSII and PSI proteins were depleted to trace amounts in the mutant cells grown in light. In contrast, the accumulation of LHCI and LHCII was unaffected except for LHCA3. Our results suggest that the replacement of Chls with ChlsGG strongly affects the structural and functional integrity of PSII and PSI complexes but their associating LHC complexes to a lesser extent. Affinity purification of HA‐tagged LHL3 confirmed the formation of a stable LHL3‐GGR complex, which is vital for GGR stability. The LHL3‐GGR complex contained a small amount of PSI complex assembly factors, suggesting a putative coupling between Chl synthesis and PSI complex assembly. [ABSTRACT FROM AUTHOR]

• We analyze the impact of plasma noise on Taiji using Wind's electron number density data. • Lomb–Scargle method is used to estimate the spectrum of plasma noise in 10−6 to 10−2 Hz. • The spectrum of plasma noise is fitted by power law and its effect on TDI is estimated. • It provides a basis for estimating plasma noises in similar gravitational wave observatories. In space-based laser interferometric gravitational wave antennas, plasma from the solar wind is an important noise floor source for laser interferometric measurements between two distant spacecraft. In this study, we aim to analyze the impact of solar wind on the inter-satellite laser interferometric measurements of the Taiji mission, a space-based laser interferometric gravitational wave antenna proposed by the University of Chinese Academy of Sciences. Based on the 6.5-year electron number density data from the National Aeronautics and Space Administration Wind spacecraft and considering the uneven sampling characteristics of the data, we employed the Lomb–Scargle spectral analysis method to study the impact of solar wind plasma on intersatellite laser interferometric measurements within the frequency range of 1 × 10 - 6 Hz to 0.01 Hz. The study shows that the effect of the plasma on the intersatellite laser interferometric measurement is approximately 1 pm/ Hz at 3.3 mHz, which is one order of magnitude smaller than the requirements on the displacement noise of the interferometric measurement of the Taiji mission, indicating that the noise due to plasma will not affect the aim of the Taiji mission to detect gravitational waves. The research can be applied to Taiji, Laser Interferometer Space Antenna, and future gravitational wave detection missions. [ABSTRACT FROM AUTHOR]

AbstractThe microwave free-space technique is an important method to characterize material properties in the scientific fields and actual applications. A microstrip patch antenna is a good radiating element to construct a compact, low-cost free-space setup. It is necessary to clarify the effects of different properties of radiating patch antenna. In this study, microwave attenuation and phase shift are measured with patch antennas with different radiated microwave power and gain. Both the experimental results of attenuation and phase shift show that a high gain of the radiating elements is helpful to measure the microwave parameters in the free-space method accurately, while improving radiating power has less effect. [ABSTRACT FROM AUTHOR]

In this paper, based on the three‐dimensional frame structure between the antenna unit and the ground, a decoupling method, the current phase decoupler method, is proposed for the 5 G smartphone multiunit frame antenna. Using this method in a dual‐unit antenna, the additional current path reverses the phase of the coupled current flowing through the ground to the adjacent unit, while weakening the coupled current intensity and significantly suppressing the coupling between the units. The measured results show that the coupling is less than −28 dB, and the maximum efficiency is 85.53% without adding any lossy components. In an eight‐unit smartphone antenna system, the coupling of adjacent units can also be reduced below −24.6 dB with a maximum efficiency of 82.17%. This method has significant advantages over the existing decoupling methods and can be used as the preferred decoupling scheme for the future 5 G smartphone multiunit frame antenna. [ABSTRACT FROM AUTHOR]

The rapid development of wireless technology has heightened the requirement for antenna performance. Traditional antennas, characterized by their static performance, are no longer sufficient to accommodate the dynamic requirements of modern wireless systems. The advent of reconfigurable antennas has opened new horizons for unleashing the full potential of wireless communication systems. These antennas are versatile and can switch various performance modes in a simple yet ingenious structure. Based on the cutting‐edge research, this paper deeply explores their core design principles, the latest breakthroughs, and the ingenious methods. Through an in‐depth analysis of a multitude of reconfigurable antenna design cases, existing design methods are categorized into four categories: electronic and optical switches, structural physical change, smart materials, and bistable composites. Each category is subjected to a meticulous dissection, revealing the underlying design mechanisms, highlighting innovativeness, and discussing both the strengths and limitations. Furthermore, by conducting a comprehensive comparative analysis, this paper concludes the forthcoming challenges and prospective trajectories for this research domain. Therefore, this paper can serve as a valuable reference for researchers seeking to deepen their understanding and application of various reconfiguration methods in the design of reconfigurable antennas, guiding them toward the forefront of antenna technology innovation. [ABSTRACT FROM AUTHOR]

Narrowband terahertz (THz) detection plays a key role in biomedical imaging, biological applications, and security screening. Particularly rapid resolution of material differences based on spectral fingerprints or time‐resolved observation of the materials conformational state typically requires only the measurement of spectral information at a few selected frequencies. Here, a high‐performance resonance‐based coupled photoconductive antenna (PCA) was designed, which consists of a square split‐ring resonator (SRR) and an H‐shaped antenna. The incident THz wave energy can be effectively coupled in the gap of the H‐shaped antenna, and the coupling effect base on coupled harmonic oscillator model can be effectively strengthened. By decreasing the square SRR gap width HD, the relative position parameters of d and L3 between the square SRR and H‐shaped antenna can markedly improve the resonance frequency sensitivity with inductive–capacitive resonance. With the square SRR arm length L1 = L2 = L increased, the resonance frequency markedly shifted toward a lower frequency and the resonance sensitivity increased. The results prove that the THz frequency selection detection range of the coupled PCA can be designed to 0.1∼1.0 THz. Compared with the traditional H‐shaped photoconductive detection antenna, the detection resonance peak shifted the lower frequency and the maximum THz detection sensitivity increased by approximately two orders of magnitude at 0.2528 THz. The structure of the noncontact micrometer–coupled PCA is simple and easy to fabricate and integrate. Our findings may also help to advance the use of THz technology in rapid distinguish material properties. [ABSTRACT FROM AUTHOR]