This paper proposes a lumped parameter microwave dual frequency filter implemented using surface mount technology (SMT), which has low-pass and band-pass characteristics. We implement a dual-band response by integrating a matching network and harnessing the inherent parasitic inductance of SMT capacitors. This strategy generates transmission zeros (TZs) in the high-frequency band, significantly enhancing frequency selectivity. The performance of the filter was verified through odd-even mode analysis and validated through experimental measurement. The experiment measured that the low pass cut-off frequency of the filter is 360 MHz, and the second channel exhibits good band-pass characteristics at 800 MHz, with an insertion loss of -2.191 dB.

A high-impedance ground plane has been proposed that enables the reflection of magnetic fields within a frequency range of interest. When being combined with loop coil antennas or H-field-oriented structures, it can boost transmission efficiency by up to 3 dB. Although several approaches, such as mushroom-shaped protuberant surfaces paired with capacitive loading, have been described to suppress surface waves at certain frequency ranges, the shift to a desired frequency range (e.g., from 5 GHz to 1 GHz) is marginal, and their form factors make these methods less ideal for applications in power and data communication. Here, we describe new strategies for a low-profile high-impedance ground plane. The insertion of a metal ground plane between the top and bottom mushroom-shaped surfaces reinforces capacitive couplings between adjacent unit cells. When coupled with extended spiral paths, this configuration leads to an apparent change in the resonant frequency of the structure. Fabrication of the proposed structure demonstrates that the sandwiched metal ground plane, paired with extended spiral paths, leads to a noticeable shift in the resonant frequency toward lower sub-GHz ranges at given dimensions. Measurements are in good agreement with the results from the analytical model.

This article addresses the challenges associated with poor tunability and the single absorption function in absorbers. To address these challenges, we designed a dual-band switchable tunable absorber utilizing graphene and vanadium dioxide.The proposed absorber exploits the phase transition characteristics of vanadium dioxide to achieve absorption in the low-frequency band when it is in the dielectric state and absorption switching in the high-frequency band after phase transition. Furthermore, the Fermi level is altered by applying a bias voltage to the graphene, resulting in reduced square resistance. This mechanism allows tuning of the absorption frequency when the vanadium dioxide is in the dielectric state and adjustment of the absorption bandwidth when it is in the metallic state. Simulation results reveal that when the vanadium dioxide is in the dielectric state, the absorption rate exceeds 90% within the 20.0-27.7 GHz range. At this time, increasing the Fermi level of the graphene alters the absorption frequencies to 11 GHz and 42 GHz, respectively. Conversely, when the vanadium dioxide is in the metallic state, the absorption rate exceeds 90% within the 31.1-48.7 GHz range. Thus, elevating the Fermi level of the graphene leads to absorption band tuning at higher frequencies. This absorber demonstrates strong tunability and multifunctional absorption capabilities, offering outstanding practical application value.

In this study, we present a Y-shaped electromagnetic waveguide switch with integrated resonators designed to control wave propagation within a specific frequency range. The switch comprises two input lines and one output line, with each input line connected to a resonator of height d₁ and d₃ that can either allow or block transmission of the signal. Using the Transfer Matrix Method (TMM), we determined transmission and reflection properties to analyze the device's performance in ON (transmission) and OFF (blocking) states. Our results indicate that, depending on the choice of geometric and structural parameters, the resonators enable a transmission of more than 99% (T₁₃) from the first input line to the output line in the ON state, while reducing the transmission from the second input line to less than 1% (T₂₃) in the OFF state .These findings show the importance of resonator tuning for achieving precise electromagnetic wave control, offering a practical approach for enhancing signal management in advanced optical communication systems.

This paper presents a single-layer reflective metasurface for generating dual-linearly polarized orbital angular momentum (OAM) beams with mode number l=-1 at X-band. Phase modulation is achieved by adjusting the unit cell dimensions, which efficiently converts linearly polarized waves into vortex waves with the desired OAM mode. The proposed unit cell integrates a compact `米'-shaped inner patch with a square frame, with a compact size of 0.4λ₀ × 0.4λ₀, enabling independent control of both x-polarized and y-polarized waves. By varying the unit size,a broad phase shift range of 374° is achieved at 8-12 GHz. Based on phase compensation principles, the designed metasurface array is successfully generates dual-polarized vortex waves at X-band. The proposed metasurface exhibits high gain, narrow divergence angle, bandwidth, and dual-polarization capability, demonstrating significant potential for OAM wave multiplexing in wireless communication systems.

This paper introduces a compact dual-band wearable antenna designed for mmWave applications. The antenna is fabricated on a Rogers 3003 semi flexible substrate with dimensions of 15 × 15 × 1.52 mm³ and features a circular radiating patch with a full ground plane. Initially designed to resonate at 28 GHz, the antenna incorporates a square split-ring resonator in the ground plane to achieve an additional resonance at 38 GHz. To improve bandwidth and gain, a round necktie configuration is applied by adding two diagonal rectangular patches to the periphery of the radiating patch. The measured impedance bandwidths are 21.4% at 28 GHz and 23.7% at 38 GHz. The antenna achieves gains of 5.91 dBi and 4.57 dBi, with efficiencies of 90% and 78% at the respective operating bands. Simulated SAR values are 0.57 W/kg and 0.31 W/kg for 1 g and 10 g of human tissue at 28 GHz, and 0.18 W/kg and 0.16 W/kg at 38 GHz. These SAR values comply with FCC and ICNIRP safety standards. Additionally, bending tests illustrate that the antenna's performance was stable under deformation. As a result, the proposed antenna is ideal for fast connectivity 5G and biomedical applications since it efficiently spans fundamental mmWave frequency ranges.

When permanent magnet synchronous motors (PMSMs) drive flexible loads, unknown disturbances (such as sudden load torque changes, parameter uncertainties, and unmodeled dynamics), can degrade the control performance of the system and may even cause irreversible physical damage. To deal with this problem, this paper presents an improved non-singular terminal sliding mode control (INTSMC) scheme based on a finite-time extended state observer. First, the acceleration feedback is introduced into the speed loop to establish the dual-inertia model of the PMSM flexible load system. Secondly, the conventional exponential reaching law is improved to obtain a novel reaching law with adaptive adjustment of the convergence speed, and a novel INTSMC controller is designed accordingly to enhance the system response speed. Then, a finite-time extended state observer (FTESO) is designed to estimate the disturbances of the system, and the estimated disturbances are compensated for the INTSMC controller to achieve convergence in finite time and improve the robustness of the system. The finite-time stability theory is used to prove the stability of the designed controller and observer. Finally, the simulations and experiments demonstrate the effectiveness of the proposed control scheme in improving the system’s anti-disturbance capability.

This paper proposes a spin decoupling phase gradient (SDPG)-scalar holographic impedance (SHI) bidirectional hybrid metasurface (MTS). The integrated SDPG MTS modulates the space wave (SPW) and is excited by the horn, whereas the SHI-integrated MTS modulates the surface wave (SFW) and is excited by a surface-mounted monopole. As example, (1) Dual orbital angular momentum (OAM) beams are generated at 18.3 GHz by the integrated SDPG MTS at 18.3 GHz: left hand circular polarization (LHCP) (OAM mode l₁ = 1, θ₁ = 30˚, φ₁ = 0˚), right hand circular polarization (RHCP) (l₂ = -1, θ₂ = -30˚, φ₂ = 0˚). (2) Linear polarization (LP) pencil beam is generated at 7.8 GHz by the integrated SHI MTS: (l₃ = 0, θ₃ = 150˚, φ₃ = 0˚). The peak gain is 19.9 dBi, and the OAM purity is above 84.7%. The novelty of the manuscript is as follows: (1) To the authors' knowledge, a full-space SDPG-SHI hybrid metasurface has been developed for the first time, which greatly expands the bidirectional multifunctional design freedom. (2) Much higher aperture efficiency (AE) than published results. (3) The proposed SDPG-SHI hybrid MTS simultaneously possesses the following advantages: small size (π × 7.19λ × 7.19λ at 18.3 GHz, and π × 3.06λ × 3.06λ at 7.8 GHz), full space, multibeams, multipolarization, reconfigurability and simultaneous modulation of SPW and SFW. The developed MTS has promising applications in high-capacity bidirectional communication scenarios.

In this study, we evaluated the feasibility of intra- and peritumoral artificial intelligence (AI)-based radiomics from Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for preoperative prediction of lymphatic vascular invasion (LVI) in invasive breast cancer (IBC). Our results demonstrated that a radiomic model (area under the receiver operating characteristic curve AUC = 0.951) outperformed a clinical model (AUC = 0.644) in 193 patients. Optimal tumor segmentation using 3D RU-Net (Dice score > 0.75) and 3 mm to 4 mm isotropic 3D peritumoral expansion yielded the strongest predictive performance.

A four-element compact planar MIMO antenna is developed for the 3.5 GHz 5G sub-6 GHz band, ensuring reliable radiation performance and enabling simultaneous downlink and uplink communication. The proposed MIMO system incorporates four isosceles triangular elements, where two are allocated for uplink and the other two for downlink. Its compact structure facilitates simultaneous communication with separate provisions for uplink and downlink operations. The FR4 substrate has four antennas printed orthogonally to minimize mutual interaction between the elements. Triangles are more isolated and efficient when their corners are trimmed. Cutting the semi-circle yields the desired resonance frequencies. The proposed MIMO system measures 90 × 90 × 1.6 mm³. The performance of the proposed system was evaluated using multiple metrics, including far-field radiation patterns, S-parameters, channel capacity loss, envelope correlation coefficient, peak gain, diversity gain, and radiation efficiency. The simulated results closely aligned with the measured data, demonstrating strong agreement.

This paper presents a novel compact, broadband, and low-loss slow-wave folded substrate integrated waveguide (SW-FSIW) structure, achieved by integrating grounded patches into a conventional FSIW configuration. The slow-wave effect is generated through enhanced capacitive coupling between the grounded patches and the signal trace grid patterned on the FSIW's middle metal layer. Compared to a conventional SIW with the same cutoff frequency, the SW-FSIW achieves a 66% reduction in lateral dimension and a 37% reduction in longitudinal dimension, resulting in a total area reduction of 78.6%. The design exhibits superior performance to state-of-the-art slow-wave SIWs in lateral size reduction, fractional bandwidth (92%), and attenuation constant. Experimental validation shows excellent agreement between measurements and simulations for a fabricated prototype operating across the 4.07-11 GHz frequency range, confirming the structure's strong potential for applications in compact microwave systems, 5G/6G front-ends, and satellite communications.

Long-range near-field magnetic resonance wireless power transfer (WPT) technology holds broad application prospects in fields such as medical implants and industrial manufacturing robots. However, it faces challenges of low efficiency and poor robustness in long-distance transmission. This study proposes an innovative collaborative optimization approach that integrates the machine learning gradient descent optimization algorithm (GDOA) with non-Hermitian topological physics to precisely regulate the coupling strength distribution, thereby realizing a highly flexible, efficient, and robust WPT system capable of anchoring transmission frequencies and accommodating an arbitrary number of resonators. Experimental results demonstrate that the GDOA-optimized Su-Schrieffer-Heeger (SSH)-like topological chain achieves a transmission efficiency of 65% at the target frequency and maintains 57.9% efficiency under 30% structural perturbations, significantly outperforming the SSH chain (45.6%) and uniform chain (24.1%) in control groups. This research provides theoretical and experimental support for the design of machine learning-based topological long-range WPT systems, offering substantial practical value, particularly in medical electronic power supply and wireless industrial equipment applications.

This paper presents an enhanced design of a reconfigurable fractal ultra-wideband (UWB) antenna, improved through the inclusion of parasitic elements. The antenna incorporates two plus-shaped parasitic elements and a hexagonal radiating patch, while maintaining compact dimensions of 30 mm × 22 mm × 1.6 mm on an FR4 substrate. A partial ground plane with an integrated rectangular slot is etched on the backside of the resonator. The antenna was designed using HFSS, fabricated, and experimentally validated. The measured results show good agreement with the simulations. It operates over a frequency range of 4 to 10.57 GHz, with resonant frequencies at 4.7, 7.92, and 10 GHz. The design achieves a gain between 2.76 and 5.83 dB and maintains high radiation efficiency ranging from 82% to 95%. To further enhance performance, two strategically placed HPND-4005 PIN diodes are incorporated, allowing tunable resonance characteristics by altering current distribution under various switch configurations. As a result, the reconfigurable antenna extends its operational bandwidth from 3 to 14 GHz, making it suitable for a variety of wireless applications such as Wi-Fi, WiMAX, WLAN, and C-, X-, and Ku-band communications. Notably, the design achieves this wideband reconfigurability using only two PIN diodes while maintaining a compact footprint - offering an advantage over previous designs. Its features support seamless integration into compact electronic devices, enabling manufacturers to incorporate multiple antennas with minimal complexity.

This paper presents the conception and fabrication of a new steerable microstrip antenna for ISM band applications. At first, the fundamental antenna element is designed, optimized, and miniaturized to operate at 2.45 GHz, exhibiting a narrow impedance bandwidth and a good gain. However, the standalone element lacks beam steering capability. To enable directional control of its radiation pattern, a novel 3 dB hybrid coupler is used to feed two identical optimized elements, forming a switched array antenna. The resulting configuration achieves a wide impedance bandwidth and improved gain with beam steering capability. The proposed steerable antenna is designed and fabricated on a Rogers RT/duroid 5880 substrate. The simulated results are validated with measured data, showing good agreement and confirming the design's performance.

With the increasing interest in negative group delay (NGD) function for RF and microwave circuits, and sensing applications, techniques to fit multiple NGD bands in a single and compact structure can open new possibilities. In this work, a simple and innovative compact quadband NGD microstrip circuit is presented for all ISM bands between 2 GHz and 6 GHz. The circuit is composed of a base line (BL) coupled to the transmission line, which sets the lowest NGD band, and each additional NGD band is created by inserting stubs into the BL. The impact of each stub on the overall circuit is analyzed using parametric simulation. The design and tuning method of the coupled line used to achieve the NGD multiband function is described in detail. Through the insertion loss and group delay results, a well-fitted correlation is observed between the simulated and measured results, where the simulated transmission coefficient and group delay show NGD quadband response with center frequencies at 2.46, 3.49, 4.96, and 5.69 GHz with respective NGD bandwidth of 0.89%, 0.83%, 0.66%, and 0.97%, respectively, whereas the measured results present center frequency NGD deviation of less than 1%. In addition, the NGD quadband circuit prototype has a compact size 40.2 × 30.2 × 1.57 mm³. The measured NGD results are in good agreement with simulated ones.

In this paper, a novel framework is proposed which combines physical scattering models with artificial neural networks (ANN) to solve electromagnetic scattering problems of random media through a volume integral equation formulation. The framework is applied to a snow scattering problem where snow is represented by a bicontinuous random medium. A neural network is constructed linking the random media structure to the induced dipole moments on the media. The volume integral equation (VIE) serves as a natural physical constraint on the network input-out relations and is used to guide the training of the network. A discrete dipole approximation (DDA) strategy is adopted to convert the VIE into matrix equations which also defines the loss function of the surrogate neural network. For addressing deterministic scattering problems, this represents a viable alternative to traditional iterative algorithms, providing comparable accuracy at the expense of reduced efficiency. In solving statistical scattering problems, neural networks with physics-informed loss function achieve accuracy comparable to that of data-driven models while significantly reducing the dependency on extensive precomputed training datasets. The physics-based loss function also allows the network to self-diagnose the prediction accuracy in real operations. This work demonstrates a novel strategy to effectively merge physical equations with artificial neural networks, and the idea can be inspiring to many relevant fields, especially when randomness effects are exhibited through a complicated nonlinear system.

This paper presents the design and in-depth performance analysis of a miniaturized four-port multiple-input multiple-output (MIMO) antenna module intended for integration on the rear cover of mobile devices. The four antenna elements are configured in a sequential rotation layout and fabricated on a low-profile circular substrate. Each antenna element features an E-shaped patch on the upper side of the substrate, coupled with a rectangular defected ground structure (DGS) on the lower side. A needle-like decoupling mechanism has been incorporated to improve the isolation between the antenna elements. The measured -10 dB impedance bandwidth ranges from 3.5 to 5.45 GHz, successfully meeting the demands of the 5G NR bands N77 (3.3-4.2 GHz), N78 (3.3-3.8 GHz), N79 (4.4-5 GHz), as well as the wireless local area network (WLAN) band (5.15-5.35 GHz). The isolation levels between the antenna elements exceed 17 dB. The average total efficiency is over 40.76%, and the envelope correlation coefficients (ECCs) are maintained below 0.01. The measurement outcomes indicate that the proposed MIMO antenna not only fulfills the requirements for the 5G and WLAN frequency bands but also successfully achieves miniaturization and superior wireless communication performance.

This paper introduces a novel finite element boundary integral approach for magnetic resonance electrical properties tomography (MR-EPT) with an inhomogeneous background which improves imaging quality by utilizing inhomogeneous background inversion and allows for a flexible selection of areas for fine reconstruction, thereby saving resources and quickly obtaining the most important information. In the proposed approach, a fictitious inhomogeneous background is initialized, followed by a preliminary reconstruction conducted across the entire field of view (FOV) through a few iterations. This fictitious inhomogeneous background aims to enhance the quality of reconstruction, surpassing that achieved through inversion in a homogeneous background. The proposed method is significantly suitable to the prevailing refinement mechanism, where the refinement area identified from the preliminary reconstruction image is embedded in an inhomogeneous background. This method combines the advantages of the computational efficiency of local methods and the noise robustness of global methods. Numerical examples have validated that the inversion with a fictitious inhomogeneous background yields a superior reconstruction quality. The subsequent narrowing of the inversion area results in a more focused inversion process, significantly reducing reconstruction time.

This paper presents a four-port quarter-mode substrate integrated waveguide (QMSIW) MIMO antenna designed for 2.1 GHz wireless applications. The antenna employs orthogonally positioned complementary square-split ring resonator slots to achieve substantial miniaturization. Additionally, mutual coupling between the antenna elements is effectively minimized by incorporating cross-shaped slots between them, enhancing overall performance. The proposed four-port MIMO antenna achieves high isolation of 40 dB and features a compact electrical size of 0.19λ₀ × 0.19λ₀. The antenna demonstrates outstanding MIMO performance, with simulated and measured gains of 5.32 dBi and 5.44 dBi, respectively. Its efficiency is further supported by key performance metrics, including a low envelope correlation coefficient (ECC) of 0.0841 and a high diversity gain (DG) of 9.22 dB, ensuring enhanced signal reliability and reduced interference. With its compact structure, excellent isolation, and strong diversity performance, the proposed antenna serves as a highly suitable candidate for directional Wi-Fi applications.

Aspiration pneumonia is a type of lung infection caused by the accidental inhalation of foreign substances into the respiratory tract. It is commonly seen in the elderly, young children, and individuals who are unconscious or have difficulty swallowing. Early detection and diagnosis of aspiration pneumonia are beneficial for improving patient outcomes and reducing the medical burden. In this study, we collected bronchoscopic video data from 25 patients in two hospitals. After image preprocessing and expert annotation, we obtained 2830 images from some patients for training and 1215 images from the other patients for validation. We selected three deep learning methods for training. The experimental test results for the identification of aspiration pneumonia showed that ResNet-50, which is based on convolutional operations, gave the best performance in the automatic identification of aspiration pneumonia, with a precision of 97.82%, a recall of 91.82%, an F1 score of 94.73%, and an overall accuracy of 95.88%. The experiments demonstrated that deep learning methods can be used for the automatic identification and diagnosis of aspiration pneumonia from bronchoscope images and deep learning is reported here for the first time for diagnosing aspiration pneumonia from bronchoscope images.