Microwave Antenna Research Articles

Additional Acceleration of Antenna Optimal Characterizationwith Modeling Support

Optimal characterization is assumed to provide the best solution for the designed cost function among the possible solutions within the specified range. These processes can take a long time depending on the applications and computer hardware used. Here, the optimization process is supported by ANN modeling in order to shorten the current optimization processes as much as possible. For this purpose, the selection of design parameters of the bowtie patch antenna (BPA) is presented as a multi-dimensional, multi-objective modeling-supported design optimization problem. The operating frequency of the proposed antenna is 28 GHz, which is the standard for millimeter wave band and 5G technologies. To overcome this challenging design optimization, a new, fast and powerful optimization algorithm was used by modifying the non-dominant sorting genetic algorithm (NSGA)-III, and the optimal characterization of the microwave antenna design was achieved. Although the proposed method gives the same results compared to the existing process, it takes much less time. Therefore, it is possible to shorten the process and reduce costs without the need for extra applications or hardware. As a whole, the proposed design optimization process is an efficient, fast and reliable solution for all design problems.

Near-Field Microwave Imaging Method of Monopole Antennas Based on Nitrogen-Vacancy Centers in Diamond.

Visualizing the near-field distribution of microwave field in a monopole antenna is very important for antenna design and manufacture. However, the traditional method of measuring antenna microwave near field distribution by mechanical scanning has some problems, such as long measurement time, low measurement accuracy and large system volume, which seriously limits the measurement effect of antenna microwave near field distribution. In this paper, a method of microwave near-field imaging of a monopole antenna using a nitrogen-vacancy center diamond is presented. We use the whole diamond as a probe and camera to achieve wide-field microwave imaging. Because there is no displacement structure in the system, the method has high time efficiency and good stability. Compared with the traditional measurement methods, the diamond probe has almost no effect on the measured microwave field, which realizes the accurate near-field imaging of the microwave field of the monopole antenna. This method achieves microwave near-field imaging of a monopole antenna with a diameter of 100 µm and a length of 15 mm at a field of view of 5 × 5 mm, with a spatial resolution of 3 µm and an imaging bandwidth of 2.7~3.2 GHz, and an optimal input microwave phase resolution of 0.52° at a microwave power of 0.8494 W. The results provide a new method for microwave near-field imaging and measurement of monopole antennas.

Microwave antenna focusing for spatially resolved modulation of burn rate

This study explores the ability to dynamically modulate the burn rate of nanothermites through microwave generated heat zones. These heat zones were generated by embedding a microwave receiving antenna in 3D printed Al/CuO samples. These thermal hot spots in the nanothermites are generated by the induced high electric fields at the terminus of an embedded receiving antenna and are monitored by an IR camera. The burn rates were investigated for different MW induced hot spot temperatures, geometries and receiving antenna materials. The local burn rate increase closely tracks the hot spot spatial distribution, and for our experimental condition enabled an amplification of burn rate of ∼6×. An effective burn rate activation energy was calculated to be ∼18 kJ/mol from the Arrhenius plot of local burn rate and initial temperature. Three color pyrometry confirms that the main mechanism of the local burn rate increase is related to the initial temperature profile in the sample. This study demonstrates the sensitivity of the local burn rate of nanothermites to initial temperature and provides a new approach to modulate the burn rate by localizing MW energy.

The Optimization of Microwave Field Characteristics for ODMR Measurement of Nitrogen-Vacancy Centers in Diamond

A typical solid-state quantum sensor can be developed based on negatively charged nitrogen-vacancy (NV−) centers in diamond. The electron spin state of NV− can be controlled and read at room temperature. Through optical detection magnetic resonance (ODMR) technology, temperature measurement can be achieved at the nanoscale. The key to ODMR technology is to apply microwave resonance to manipulate the electron spin state of the NV−. Therefore, the microwave field characteristics formed near the NV− have a crucial impact on the sensitivity of ODMR measurement. This article mainly focuses on the temperature situation in cellular applications and simulates the influence of structural parameters of double open loop resonant (DOLR) microwave antennas and broadband large-area (BLA) microwave antennas on the microwave field’s resonance frequency, quality factor Q, magnetic field strength, uniformity, etc. The parameters are optimized to have sufficient bandwidth, high signal-to-noise ratio, low power loss, and high magnetic field strength in the temperature range of 36 °C to 42.5 °C. Finally, the ODMR spectra are used for effect comparison, and the signal-to-noise ratio and Q values of the ODMR spectra are compared when using different antennas. We have provided an optimization method for the design of microwave antennas and it is concluded that the DOLR microwave antenna is more suitable for living cell temperature measurement in the future.

The metamaterial with high thermal-mechanical stability and the practical application as the microwave antenna: Mechanical designs, theoretical predictions, and experimental demonstrations

To address the demand of maintaining the structural configuration upon extreme temperature changes, metamaterials with high thermal-mechanical stability have attracted wide attention recently. However, there are still some challenges for previous studies regarding mechanical design and practical application exploration. This manuscript proposes the design strategy for the lattice sandwich metamaterial with excellent zero thermal-induced warping, along with the metamaterial-based antenna with a high stability of electromagnetic signal transmission. Through the design strategy of discrete lattice units of the metamaterial, the ultra-low thermal warping of the metamaterial is realized upon the non-uniform temperature field. Here, the theoretical model is established to predict both heat transfer and thermal-induced deformation behavior upon complex mechanical-thermal loading conditions. The combination of theoretical predictions, finite element analysis, and experiments verifies the thermal dimensional stability of the metamaterial proposed here. Compared with the heterogeneous bilayer plate, experimental thermal warping of the metamaterial specimen is reduced by 99.7%. Additionally, compared with the bilayer-based specimen, gain attenuation, the main lobe's offset angle, and the voltage standing wave ratio offset of the metamaterial-based antenna specimen are experimentally reduced by 99.5%, 99.9% and 74.2%, revealing the huge application potential of this metamaterial in the field of spacecraft communication.

Microwave analogy of Förster resonance energy transfer and effect of finite antenna length

The near-field interaction between quantum emitters, governed by Förster resonance energy transfer (FRET), plays a pivotal role in nanoscale energy transfer mechanisms. However, FRET measurements in the optical regime are challenging as they require nanoscale control of the position and orientation of the emitters. To overcome these challenges, microwave measurements were proposed for enhanced spatial resolution and precise orientation control. However, unlike in optical systems for which the dipole can be taken to be infinitesimal in size, the finite size of microwave antennas can affect energy transfer measurements, especially at short distances. This highlights the necessity to consider the finite antenna length to obtain accurate results. In this study, we advance the understanding of dipole–dipole energy transfer in the microwave regime by developing an analytical model that explicitly considers finite antennas. Unlike previous works, our model calculates the mutual impedance of finite-length thin-wire dipole antennas without assuming a uniform current distribution. We validate our analytical model through experiments investigating energy transfer between antennas placed adjacent to a perfect electric conductor mirror. This allows us to provide clear guidelines for designing microwave experiments, distinguishing conditions where finite-size effects can be neglected and where they must be taken into account. Our study not only contributes to the fundamental physics of energy transfer but also opens avenues for microwave antenna impedance-based measurements to complement optical FRET experiments and quantitatively explore dipole–dipole energy transfer in a wider range of conditions.

Theory of electron spin resonance in scanning tunneling microscopy

Electron spin resonance (ESR) spectroscopy in scanning tunneling microscopy (STM) has enabled probing the electronic structure of single magnetic atoms and molecules on surfaces with unprecedented energy resolution, as well as demonstrating coherent manipulation of single spins. Despite this remarkable success, the field could still be greatly advanced by a more quantitative understanding of the ESR-STM physical mechanisms. Here, we present a theory of ESR-STM that quantitatively models not only the ESR signal itself, but also the full background tunneling current, from which the ESR signal is derived. Our theory is based on a combination of Green's function techniques to describe the electron tunneling and a quantum master equation for the dynamics of the spin system along with microwave radiation interacting with both the tunneling current and the magnetic system. We show that this theory is able to quantitatively reproduce the experimental results for a spin-1/2 system (TiH molecules on MgO) across many orders of magnitude in tunneling current, providing access to the relaxation and decoherence rates that govern the spin dynamics due to intrinsic mechanisms and to the applied bias voltage. More importantly, our work establishes that (i) sizable ESR signals, which are a measure of microwave-induced changes in the junction magnetoresistance, require surprisingly high tip spin polarizations, and (ii) the coupling of the magnetization dynamics to the microwave field gives rise to the asymmetric ESR spectra often observed in this spectroscopy. Additionally, our theory provides very specific predictions for the dependence of the relaxation and decoherence times on the bias voltage and the tip-sample distance. Finally, with the help of electromagnetic simulations, we find that the transitions in our ESR-STM experiments, in which the tunnel junction is irradiated by a nearby microwave antenna, can be driven by the ac magnetic field at the junction. Published by the American Physical Society 2024

Microwave Antenna Optimization for Low Latency and High Throughput Communication Systems

This paper presents a comprehensive exploration of microwave antenna optimization strategies aimed at achieving low latency and high throughput in modern communication systems. With the escalating demand for real-time applications and data-intensive services, the optimization of microwave antennas has become imperative to meet the stringent requirements of responsiveness and efficiency. The abstract delves into various facets of antenna optimization, including design parameters, signal processing techniques, and deployment considerations, all geared towards minimizing latency and maximizing throughput. Through a thorough review of existing literature and practical insights from real-world deployments, this research aims to provide valuable guidance for engineers and researchers in designing and implementing optimized microwave antennas for next-generation communication networks. By examining the intricate interplay between antenna design, signal processing algorithms, and deployment strategies, this paper elucidates the challenges and opportunities in achieving low latency and high throughput in microwave communication systems. Furthermore, it highlights the significance of factors such as gain, beamwidth, polarization, frequency band selection, multiple-input multiple-output (MIMO) systems, beamforming, adaptive coding and modulation (ACM), antenna placement, tower height, and line-of-sight considerations in optimizing antenna performance. The findings presented in this paper contribute to advancing the understanding of microwave antenna optimization and offer practical insights into enhancing the responsiveness, efficiency, and reliability of modern communication networks.

A high‐power and high‐efficiency low‐profile aperture converter array

AbstractFor a phased‐array antenna system, position mismatches in spacing distances between source's output and antenna arrays’ input ports are common. At present, flexible radiofrequency cables are always utilized to electrically connect those two parts, which will result in the reduced integration. To tackle this problem, a low‐profile aperture converter array (ACA) is first proposed, which is applied between a microwave source and antenna arrays. Each stripline‐structured channel of the ACA is composed of the signal lines with different routing shapes to achieve nearly the same phase shift. In this study, a high‐power and high‐efficiency 16‐channel ACA is designed, fabricated and measured at X‐band. Experimental results show that it meets the requirement of 5‐kW pulse wave input, and the power transfer efficiency of each channel is more than 93.8%. Furthermore, its profile is only 0.42 at 9 GHz, which is favorable to transforming the integration of the whole system.

Transapical intramyocardial septal microwave ablation in treatment of hypertrophic obstructive cardiomyopathy: 12-month outcomes of a swine model

BackgroundTo date, the extended Morrow procedure is considered the gold standard treatment for patients with obstructive hypertrophic cardiomyopathy who experience severe symptoms and are unresponsive to medication treatment. We therefore aimed to perform transapical intramyocardial septal microwave ablation to reduce the thickness of the interventricular septum myocardium in a minimally invasive method.MethodsFourteen swine were divided to form either a microwave ablation group (n = 7) or a sham group (n = 7). In the microwave ablation group, a transapical microwave antenna was inserted into the septum to ablate each myocardial segment at 40 W for 1 min, while in the sham group, the same operation was performed but without power output. We used echocardiography, electrocardiogram, during the operation. And added computerized tomography, cardiac nuclear magnetic resonance during follow-up.ResultsSegment hypokinesis was observed in all swine immediately following ablation. Compared with the sham group, the thickness of ablated segments in the ablation group decreased significantly 1 month post-operation (ablation group, 5.53 ± 1.00 mm vs. 8.03 ± 1.15 mm, respectively, P < 0.01; sham group, 8.40 ± 0.94 mm vs. 8.21 ± 1.09 mm, respectively, P = 0.081), and the outcome was still observed 1 year post-operation (ablation group, 3.36 ± 0.85 mm vs. 8.03 ± 1.15 mm, respectively, P < 0.01). No perforation of the septum was observed during the procedure or follow-up, and no heart failure or sudden cardiac death occurred during postoperative feeding.ConclusionsTransapical intramyocardial septal microwave ablation can effectively and safely produce a large region of necrosis. This technique can potentially mimic surgical myectomy while avoiding cardiopulmonary bypass and median sternotomy in high-risk hypertrophic obstructive cardiomyopathy patients.

Reflection modulation generated by scale-free network resonator periodic structure

The pattern of resonator in a periodical array is decisive for its response under impinging electromagnetic wave. A scale-free network resonator is proposed by connecting sub-units in the form of scale free network. Scale-free network resonator array’s reflectivity near resonant frequency could be modulated at arbitrary value between zero and unity, which is different from known resonator array or frequency selective surface. Reflection amplitude modulation could generate rich behaviors, as effective medium property in wide band could be maintained near zero constant, which means zero phase shift and is favorable in radar radome structure. S-parameter analysis indicates amplitude modulation is owing to polarization conversion generated by network links. Scale-free network resonator array has application potentials in future radar radomes, electromagnetic wave lens and microwave antenna panels.

Synthesis and fabrication of proto-type microstrip patch antenna by using microwave dielectric ceramic nanocomposite material for C-band application

The microwave dielectric properties of Zn(1-x)TixAl2O4 (ZTA) ceramic nanomaterials were investigated with a focus towards their use as wireless antennas. The ZTA nanoparticles were prepared using the sol-gel technique at 700 °C for one hour. The inclusion of titanium decreased the nanomaterials' crystallite size and surface shape, which influenced their dielectric permittivity (εr). Based on the tested material and microwave antenna theory, ZTA was used to fabricate wireless patch antennas, which were then examined using a PNA series network analyzer. The measured results reveal that the return loss and impedance bandwidths of the antenna were −44.83 dB simulated and −34.88 dB measured, and 240 MHz for simulated and 220 MHz for measured, respectively. At 5.1 GHz operating frequency, the Zn0.94Ti0.06Al2O4-based patch antenna demonstrated an exceptional combination of return loss (-34.88 dB), compact size (9.3× 6.3 mm2), and broad bandwidth (220 MHz) as well as VSWR<2. Ultimately, the fabricated antenna showcases a gain of 4.24 decibels and a directivity of 5.97 decibels.

Filtenna Designed with Defected Ground Structure (DGS) for Ultra-wideband Applications

In microwave imaging applications, filter and antenna are the key components as front-end devices and function independently. Antenna radiates and receives signals to or from nearby scattered objects while filter is used to suppress unwanted signals noise before and after the required bandwidth. Current antennas suffer from high loss, bandwidth limitation and impedance mismatch and deteriorate their performance near the band-edges if connected as a stand-alone device. Due to the current trend towards simplicity and size reduction, researchers are focusing on integrating the filter and antenna into a single module called integrated filter-antenna (IFA) or filtering antenna (filtenna). These would improve the noise performance of the system and pre-filtering requirements such as complexity algorithm in inverse scattering techniques This paper introduces a novel contribution in the field of UWB antenna design by incorporating Defected Ground Structure (DGS) on both the antenna and filter. Thus, the main aim of this research is to conduct detail parametric studies of the proposed integrated filter-antenna with defected ground structure (DGS) to enhance the performance of imaging system. The proposed IFA will be analysed on Rogers RO4003C dielectric substrate by using EM tool, Computer Simulation Technology (CST) and measured using R&amp;S Vector Network Analyzer (VNA). A compact ultra-wideband (UWB) filter and UWB elliptical antenna are designed and examined in detail before combining the devices. Different types of DGS are designed and act as the ground layer of the proposed filtering antenna. The bandwidth of each design is then compared with and without the existence of DGS. The results show that the proposed IFA with DGS implementation achieve the targeted objective, with compact size, enhanced bandwidth and better performance compared to the conventional design of filter and antenna. By integrating filter and antenna into one subsystem, it can help to reduce the loss and enhancing the bandwidth of the system thus letting the antenna to operate at more different frequencies that fall within the range. Both simulated and measured results prove that by integrating filter and antenna into one module, a low loss and larger bandwidth can be accomplished. High performance compact IFA can act as microwave transceiver to improve the overall performance of the microwave imaging system, MIS.

Superparamagnetic iron oxide nanoparticle enhanced percutaneous microwave ablation: Ex-vivo characterization using magnetic resonance thermometry.

Percutaneous microwave ablation (pMWA) is a minimally invasive procedure that uses a microwave antenna placed at the tip of a needle to induce lethal tissue heating. It can treat cancer and other diseases with lower morbidity than conventional surgery, but one major limitation is the lack of control over the heating region around the ablation needle. Superparamagnetic iron oxide nanoparticles have the potential to enhance and control pMWA heating due to their ability to absorb microwave energy and their ease of local delivery. The purpose of this study is to experimentally quantify the capabilities of FDA-approved superparamagnetic iron oxide Feraheme nanoparticles (FHNPs) to enhance and control pMWA heating. This study aims to determine the effectiveness of locally injected FHNPs in increasing the maximum temperature during pMWA and to investigate the ability of FHNPs to create a controlled ablation zone around the pMWA needle. PMWA was performed using a clinical ablation system at 915MHz in ex-vivo porcine liver tissues. Prior to ablation, 50uL 5mg/mL FHNP injections were made on one side of the pMWA needle via a 23-gauge needle. Local temperatures at the FHNP injection site were directly compared to equidistant control sites without FHNP. First, temperatures were compared using directly inserted thermocouples. Next, temperatures were measured non-invasively using magnetic resonance thermometry (MRT), which enabled comprehensive four-dimensional (volumetric and temporal) assessment of heating effects relative to nanoparticle distribution, which was quantified using dual-echo ultrashort echo time (UTE) subtraction MR imaging. Maximum heating within FHNP-exposed tissues versus control tissues were compared at multiple pMWA energy delivery settings. The ability to generate a controlled asymmetric ablation zone using multiple FHNP injections was also tested. Finally, intra-procedural MRT-derived heat maps were correlated with gold standard gross pathology using Dice similarity analysis. Maximum temperatures at the FHNP injection site were significantly higher than control (without FHNP) sites when measured using direct thermocouples (93.1±6.0°C vs. 57.2±8.1°C, p=0.002) and using non-invasive MRT (115.6±13.4°C vs. 49.0±10.6°C, p=0.02). Temperature difference between FHNP-exposed and control sites correlated with total energy deposition: 66.6±17.6°C, 58.1±8.5°C, and 20.8±9.2°C at high (17.5±2.2kJ), medium (13.6±1.8kJ), and low (8.8±1.1kJ) energies, respectively (all pairwise p<0.05). Each FHNP injection resulted in a nanoparticle distribution within 0.9±0.2cm radially of the injection site and a local lethal heating zone confined to within 1.1±0.4cm radially of the injection epicenter. Multiple injections enabled a controllable, asymmetric ablation zone to be generated around the ablation needle, with maximal ablation radius on the FHNP injection side of 1.6±0.2cm compared to 0.7±0.2cm on the non-FHNP side (p=0.02). MRT intra-procedural predicted ablation zone correlated strongly with post procedure gold-standard gross pathology assessment (Dice similarity 0.9). Locally injected FHNPs significantly enhanced pMWA heating in liver tissues, and were able to control the ablation zone shape around a pMWA needle. MRI and MRT allowed volumetric real-time visualization of both FHNP distribution and FHNP-enhanced pMWA heating that was useful for intra-procedural monitoring. This work strongly supports further development of a FHNP-enhanced pMWA paradigm; as all individual components of this approach are approved for patient use, there is low barrier for clinical translation.

Microwave Ablation of the Pig Growth Plate: Proof of Concept for Minimally Invasive Epiphysiodesis.

Different surgical methods for epiphysiodesis of limb length discrepancy (LLD) have been described. Although these methods are variably effective, they are associated with morbidity (pain and limp) and potential complications. Microwave ablation is a less-invasive opportunity to halt growth by selectively destroying the growth plate via thermal energy to treat LLD in children. In this proof-of-concept study using an in vivo pig model, we asked: (1) What is the durability of response 2 to 4 months after microwave ablation of the tibial growth plate as measured by length and angulation of the tibia via a CT scan? (2) Was articular cartilage maintained as measured by standard histologic staining for articular cartilage viability? To develop an in vivo protocol for microwave ablation, we placed microwave antennas adjacent to the proximal tibia growth plate in the cadaveric hindlimbs of 18 3-month-old pigs. To determine the suitable time, we varied ablation from 90 to 270 seconds at 65-W power settings. After sectioning the tibia, we visually assessed for discoloration (implying growth plate destruction) that included the central growth plate but did not encroach into the epiphysis in a manner that could disrupt the articular surface. Using this information, we then performed microwave ablation on three live female pigs (3.5 to 4 months old) to evaluate physiologic changes and durability of response. A postprocedure MRI was performed to ensure the intervention led to spatial growth plate alterations similar to that seen in cadavers. This was followed by serial CT, which was used to assess the potential effect on local bone and growth until the animals were euthanized 2 to 4 months after the procedure. We analyzed LLD, angular deformity, and bony deformity using CT scans of both tibias. The visibility of articular cartilage was compared with that of the contralateral tibia via standard histologic staining, and growth rates of the proximal tibial growth plate were compared via fluorochrome labeling. Eighteen cadaveric specimens showed ablation zones across the growth plate without visual damage to the articular surface. The three live pigs did not exhibit changes in gait or require notable pain medication after the procedure. Each animal demonstrated growth plate destruction, expected limb shortening (0.8, 1.2, and 1.5 cm), and bony cavitation around the growth plate. Slight valgus bone angulation (4º, 5º, and 12º) compared with the control tibia was noted. No qualitatively observable articular cartilage damage was encountered from the histologic comparison with the contralateral tibia for articular cartilage thickness and cellular morphology. A microwave antenna placed into a pig's proximal tibia growth plate can slow the growth of the tibia without apparent pain and alteration of gait and function. Further investigation and refinement of our animal model is ongoing and includes shorter ablation times and comparison of dynamic ablation (moving the antennae during the ablation) as well as static ablation of the tibia from a medial and lateral portal. These refinements and planned comparison with standard mechanical growth arrest in our pig model may lead to a similar approach to ablate growth plates in children with LLD.

A Comparative Study of Narrow/Ultra-Wideband Microwave Sensors for the Continuous Monitoring of Vital Signs and Lung Water Level.

This article presents an in-depth investigation of wearable microwave antenna sensors (MASs) used for vital sign detection (VSD) and lung water level (LWL) monitoring. The study looked at two different types of MASs, narrowband (NB) and ultra-wideband (UWB), to decide which one was better. Unlike recent wearable respiratory sensors, these antennas are simple in design, low-profile, and affordable. The narrowband sensor employs an offset-feed microstrip transmission line, which has a bandwidth of 240 MHz at -10 dB reflection coefficient for the textile substrate. The UWB microwave sensor uses a CPW-fed line to excite an unbalanced U-shaped radiator, offering an extended simulated operating bandwidth from 1.5 to 10 GHz with impedance matching ≤-10 dB. Both types of microwave sensors are designed on a flexible RO 3003 substrate and textile conductive fabric attached to a cotton substrate. The specific absorption rate (SAR) of the sensors is measured at different resonant frequencies on 1 g and 10 g of tissue, according to the IEEE C95.3 standard, and both sensors meet the standard limit of 1.6 W/kg and 2 W/kg, respectively. A simple peak-detection algorithm is used to demonstrate high accuracy in the detection of respiration, heartbeat, and lung water content. Based on the experimental results on a child and an adult volunteer, it can be concluded that UWB MASs offer superior performance when compared to NB sensors.

Microwave-based removal of polyurethane and epoxy floor coatings

A new debonding technique based on microwave stimulation is being investigated in epoxy and polyurethane floor coatings by combining specific microwave absorbers with temperature-induced blowing agents. Current methods, including mechanical processes such as grinding, typically produce materials with multiple fractions, impeding recycling and the establishment of a circular economy. The microwave method facilitates mono-fraction materials and enhances accessibility to commonly used recycling techniques, particularly in solvolytic processes such as polyurethane recycling. Consequently, a standard two-layer coating system is used, consisting of an epoxy primer and a polyurethane overlay. Various microwave absorbers, such as carbon black and carbon fibres, as well as blowing agents based on thermally expanding particles are investigated. The influence of the additives on the thermo-mechanical properties is studied to identify suitable combinations. The modified materials are later evaluated for their mechanical properties. Two microwave antennas, operating at a frequency of 2.45 GHz and power of 1 kW, are used and compared to activate the modified coating systems. The technology has been successfully integrated into the formulation to allow mono-fraction recovery of the materials. No significant negative effects on material quality were observed. However, due to the extended processing time required for the debonding, further optimisation is necessary. Nevertheless, the feasibility of utilising a laboratory-based microwave approach has been substantiated.

Advancements in non-invasive microwave brain stimulation: Comment on “Influences of Microwave Antenna on brain stimulation” by Pereira et al.

Advancements in non-invasive microwave brain stimulation: Comment on “Influences of Microwave Antenna on brain stimulation” by Pereira et al.

Wideband and wide-angle reflective metasurface for efficient linear and circular polarization conversion in X, Ku, and K bands

A single-layer wideband and wide-angle reflective metasurface exhibiting linear to cross-polarization conversion (CPC) and linear-to-circular polarization (LP-to-CP) conversion in the X, Ku, and K bands is presented in this research. The devised metasurface serves as a multifunctional platform, achieving CPC over a substantial fractional bandwidth of 64.34% (9.75–19 GHz) with remarkable efficiency exceeding 90% within the 9.75–16 GHz range, reaching a remarkable 100% at resonant frequencies of 11 GHz and 14.6 GHz. Additionally, linear-to-circular polarization conversion is achieved over a significant bandwidth of 9.54 GHz. Notably, the carefully optimized unit cell structure ensures robust polarization transformation, maintaining stability against variations in the incidence angle of up to 45° for both transverse-electric (TE) and transverse-magnetic (TM) polarizations. The proposed metasurface, characterized by its simplicity, compactness, angular stability, and multifunctionality, demonstrates the considerable potential for various microwave communications, antenna design, radar invisibility, and remote sensing device applications.

Unlocking the Potential of Garnet Ferrites: A Comprehensive Review on Properties, Preparation Methods, and Applications

Abstract This review paper provides a comprehensive overview of the recent advances in garnet ferrites, a class of complex magnetic oxides with promising properties for various applications. The paper covers the crystal structure and different properties of garnet ferrites as well as their synthesis methods, including sol-gel auto-combustion, low-temperature liquid phase epitaxy, pulsed laser deposition, coprecipitation method, sol-gel, hydrothermal, ball billing method, and low-temperature solid-state reactions. The functional properties of garnet ferrites, such as permeability, hysteresis loop, loss mechanics, and saturation magnetization, are also discussed in detail, along with their potential applications in microwave devices, antennas, Faraday lasers, and cancer treatment. Finally, the challenges and future directions for the development of garnet ferrites are outlined, highlighting the need for further research to optimize their properties and improve their performance in real-world applications.