The electromagnetic environment effect test of UAV airborne equipment is commonly completed in anechoic chambers. Due to the influence of platform on antenna radiation characteristics, it is necessary to move the large platform with a antenna to anechoic chambers. However, testing costs even make this case impossible. To evaluate the electromagnetic effect of platform-free antenna ports, this study proposes an antenna platform virtualization technique. The FIT (Finite Integration Technique) is employed to calculate the antenna gain corresponding to different frequencies with and without an antenna platform. Subsequently, the difference in antenna gain under these two cases is obtained. By compensating for this variation at the interference source, the frequency domain response of the interference signal at the antenna port can be predicted, disregarding the platform. To validate the effectiveness of the proposed technique, a UAV's airborne antenna is employed for simulation analysis. The root-mean-square error of the proposed technique is less than 0.5 dB. Moreover, in terms of time domain transient interference, the effect of the platform on the transient interference signal at the antenna port is equivalent to a transfer function. The root-mean-square error for the transient response prediction method is less than 0.1%. The results demonstrate that the proposed antenna platform virtualization technique makes it possible to test the electromagnetic effect of antenna in anechoic chambers without a platform.

In this Letter, a miniaturized U-shaped microstrip filter based on a load-coupled open line is proposed. It is composed of a step impedance resonator and parallel coupled open stub line. Interfinger feed is used to enhance coupling. This configuration and coupled open stub lines form four transmission zeros between two passbands as part of open coupled stub lines to increased out-of-band rejection. The analysis of formation reason of transmission zero is conducted using lossless transmission line theory and even-odd mode analysis techniques. A filter operating at 2.53 GHz and 5.53 GHz is simulated and fabricated. The insertion loss of first passband is 1.30 dB, and return loss is -18.60 dB. The insertion loss of the second passband is 0.70 dB, and return loss is 22.89 dB. The out-of-band rejection is maintained below -20.00 dB. The final model size is 0.20λ_g x 0.23λ_g. The final physical measurement results confirm theoretical results.

In this paper, a compact and reconfigurable radiation pattern dipole antenna based on the Yagi-Uda antenna principle and operating at 2.5 GHz is designed. Controlling the switching states of three loaded switches allows for pattern reconfigurability. Three modes can be chosen based on the results of the simulations and measurements. In the first mode M1, a high directive- beam can be achieved by turning ON all the RF switches, and a measured peak gain of 6.7dBi is obtained with a corresponding half-power beamwidth (HPBW) of 44°. In the second mode, only the director is required to enable a less directive beam. This allows for a larger HPBW of 62° and a lower peak gain of 5.47 dBi. Finally, by disabling the reflector and director in the third mode, M3, we get an omnidirectional radiation pattern around the y-axis with a maximum measured gain of 3.8 dBi. The comparison with other prior art antennas shows that the proposed reconfigurable antenna has compact size, high gain, and simple design, making the structure a good candidate for new wireless applications.

The Global Navigation Satellite System Reflected (GNSS-R) Signal adopts a heterogeneous observation mode and utilizes the globally shared GNSS constellation as a multisource microwave signal transmission source, providing the opportunity signals for radar measurements. As a basis for GNSS-R bistatic remote sensing simulations, this paper analyzes wave spectrum model of sea surfaces, GNSS signal scattering model, and GNSS signal scattering power model. The modified Zavorotny and Voronovich (Z-V) model combined with two-scale method (TSM) for sea surface scattering is utilized to simulate delay Doppler map (DDM), with emphasis on the analysis of the effects of wave polarizations, delay Doppler interval, and sea states on DDM of GNSS signal scattered from sea surfaces. The correlated power model of GNSS scattering signal is validated by comparison with measured Cyclone Global Navigation Satellite System (CYGNSS) DDM data in L1 level 2.1 version. The DDM waveforms obtained from Z-V model combined with TSM are basically consistent with the CYGNSS actual data, in which strong scattering spots can be observed clearly from both simulated and measured DDMs. The modeling and analysis of DDM for spaceborne GNSS-R signal from sea surface is of great value in ocean remote sensing applications, particularly for the interpolation and utilization of various spaceborne GNSS measured data.

A hybrid continuous extended-mode inverse class-F power amplifier is designed with band-pass filtered matching networks to match transistor inputs. This design methodology increases the impedance space by incorporating free factors into the current equation of the traditional inverse class-F power amplifier (PA). The suggested matching network in this article is a reliable alternative to the commonly used low-pass structured matching network, and this synthesis method simplifies the deployment of the distributed network compared to the LC low-pass network. High efficiency is guaranteed by the constructed output band-pass matching network. To verify the validity and superiority of this design method, a broadband power amplifier operating at 2.6-4.0 GHz was designed and fabricated. Largesignal measurement results indicate that the drain efficiency (DE) ranges from 60% to 81%, 40-42.3 dBm output power, and 10.5-11.5 dB power gain across this frequency range.

Multi-input multi-output (MIMO) antennas have garnered significant attention for addressing the demands of high channel capacity, reliable and uninterrupted signal transmission, and high data rates, especially with recent advancements in 5G low Earth orbit (LEO) satellite communications. In addition to these features, automotive applications require antennas with minimal mutual coupling, high gain, multiple resonant frequencies, and compact size for user equipment. To meet these requirements, a 1×2 defected ground structure (DGS)-based fractal MIMO antenna array is proposed, covering various frequencies in the sub-6 GHz bands, including 0.7 GHz, 2.6 GHz, 3.1 GHz, and 3.5 GHz. The proposed antenna provides sufficient channel bandwidths and achieves a gain of 12.9 dBi in the n78 frequency band. The design has been fabricated, and the measured results show good agreement with the simulated ones. Moreover, the proposed antenna design can be integrated into the plastic parts of a car body, offering various automotive applications. It achieves a realistic data rate of approximately 10-12 Mbit/s, as verified through link budget calculations that consider the key parameters of LEO satellite systems.

A reconfigurable patch antenna for X-band applications offers frequency agility and adaptability for systems operating within the 8-12 GHz range. This design allows dynamic tuning of the antenna's operating frequency, making it ideal for radar, satellite communications, and military applications. By incorporating reconfigurable elements, such as switches or tunable materials, the antenna can adjust to varying operational requirements, improving performance and flexibility in compact systems where space and efficiency are crucial. A reconfigurable patch antenna for X-band applications faces several challenges. Incorporating reconfigurable elements, such as switches or tunable materials, can increase the design's complexity and reduce reliability, especially in high-frequency X-band operations. Miniaturization may result in performance trade-offs, potentially affecting the antenna's gain, bandwidth, and radiation efficiency. Additionally, ensuring stable and interference-free operation across the reconfigured frequencies can be difficult. The antenna's power-handling capability may also be limited, which is critical for radar and military applications. Finally, thermal stability and environmental resilience are key concerns, as performance can degrade under varying conditions. Hence, this paper proposes a novel miniature inverted V-slot reconfigurable patch antenna. extended antenna design features a compact radiating patch (10.5 mm x 14 mm) with an inverted `V' slot and corner modifications (chamfering) to enhance performance. Frequency and polarization reconfiguration are achieved through the enable/disable functionality of PIN diodes placed within the inverted `V' slot, allowing dynamic adjustments. The defected ground structure, featuring two vertical slots, further aids in enhancing the antenna's operational capabilities. The antenna operates across multiple frequency bands, specifically 9.84-10.46 GHz, 10.66-11.59 GHz, 11.08-11.98 GHz, and 11.61-12.11 GHz, making it suitable for X-band applications. Additionally, the proposed antenna supports right-hand circular polarization (RHCP), left-hand circular polarization (LHCP), and linear polarization (LP), offering versatile propagation modes. Both practical and simulated results demonstrate good impedance matching across different polarization states. This design is highly suitable for satellite communication and other X-band applications due to its reconfigurable and flexible performance.

This study introduces a compact, dual-band wearable slot antenna with inverted L-shaped partial ground (PG) for Wireless Local Area Networks (WLANs) and X-Band Applications. The proposed antenna design uses a flexible polyamide material of 21×21 mm² dimensions as a dielectric substrate between two metal surfaces. The prime radiator is a rectangular slot antenna patch with several slots etched out, and the ground plane is an inverted L-shaped stub that forms the PG. The insertion of slots in the patch disturbs the surface current path and increases the electrical length to offer miniaturizations. It effectively minimizes the antenna dimensions to resonate at lower frequencies. The dimensions of the PG and its placement on the ground plane attain the dual-band resonance with a good amount of return loss. Different slots are etched on the patch to get the desired frequency bands of operation. The designed antenna has achieved wide impedance bandwidths of 0.55 GHz and 1.04 GHz and peak gains of 6.45 dBi and 6.04 dBi at the 5.15 GHz and 8.13 GHz operating frequencies, respectively. The detuning behavior of the suggested antenna in bending conditions is analyzed. The effect of radiation on the human tissue is calculated in terms of Specific Absorption Rate (SAR), and it is within the standards. The antenna model is fabricated and tested, and a satisfactory agreement between the computed and measured data is achieved. The compactness, flexibility, and radiation pattern make this antenna model suitable for ON/OFF-Body communication in wearable applications.

Magneto-Acousto-Electrical Tomography (MAET), as one of the electrical characterization imaging methods, is used to image the electrical conductivity of biological tissues, which can be used for noninvasive, radiation-free imaging of biological tissues. Currently, most of the studies on MAET are simulations and experimental validations of simple structural models, and there is no sufficient validation of models with complex structures, and most of the results cannot comprehensively invert complex structural models with multi-gradient conductivity distributions. To address this problem, this paper proposes a MAET method for conductivity reconstruction of complex structural models which is applicable to 2D problems and may be extendable to 3D problems. Based on this method, the conductivity distribution of normal and diseased tissues in the simulation model of complex structures was reconstructed, and the consistency between experimental and simulated signals was verified. The results show that the MAET method for conductivity reconstruction of complex structural models proposed in this paper is conducive to improving the image resolution as well as the structural similarity, enhancing the conductivity distribution information of complex structural targets with inhomogeneous shapes and multi-gradient conductivity distributions.

Photonic crystals, often referred to as the ``semiconductors of light,'' have entered a new phase enabling exotic properties once exclusive to topological quantum matter such as topological insulators. While the development of the first three-dimensional (3D) photonic crystal marked the establishment of photonic crystals as an independent field, initial studies in topological photonic crystals focused mainly on one and two dimensions. Though a true photonic crystal counterpart of a 3D strong topological insulator remains elusive, significant progress has been made toward achieving 3D topological photonic crystals. Compared with their lower-dimensional counterparts, 3D topological photonic crystals reveal a richer variety of topological phases and surface manifestation, which enables more degrees of freedom for light manipulation. In this review, concentrating on the novel boundary states unique in 3D systems, we provide a brief survey of the 3D topological photonic crystals and recent advances in this field. We categorize and discuss various topological phases and associated phenomena observed in 3D photonic crystals, including both gapped and gapless phases. Additionally, we delve into some recent developments in this rapidly evolving area, including the realization of 3D topological phases through synthetic dimensions.

A privacy-compliant indoor localization approach utilizing a 3-D near-field (NF) passive radar imaging technique is presented. This technique leverages ubiquitously radiated electromagnetic fields for imaging, with passive tags introduced to enhance the strength of scattering fields, thereby enabling precise localization at the imaging level. The method also supports localization in non-ideal imaging scenarios, such as for limited bandwidth or in highly-reflective environments. Based on their geometrical properties the simple and low-cost passive tags enable intuitive differentiation between individuals or objects. Associated privacy protection mechanisms are discussed, where the frequency-varying properties of the passive tags provide additional flexibility and potential applications under privacy and ethical considerations. Several forms of passive tags are presented, where both simulation and experimental results validate the effectiveness of the proposed passive tag designs.

In this paper, 5G communication system requires high broadband, high efficiency, low distortion and good heat dissipation for RF power amplifier. A GaN RF power amplifier working in broadband is designed. The input and output matching is processed on the Al2O3 ceramic substrate with bond wire, and the tube shell is packaged with CuMoCu copper alloy shell. Because the power loss of the power amplifier will produce a lot of heat, the heat dissipation problem becomes a factor that can not be ignored in the design. Using the finite element thermal simulation analysis method, the maximum temperature of the power amplifier chip under long time operation is 85℃, which meets the heat dissipation demand. Under the continuous wave test conditions, the drain voltage is 30 V; the operating frequency band is 2~6 GHz; the saturation output power is 42 dBm; the power gain is more than 45 dB; and the power added efficiency is 40%. The test results meet the actual demand.

Early detection is critical for effective skin cancer treatment. Micro-/millimeter-wave spectroscopy has emerged as a promising non-invasive and cost-effective detection technique. Tissue models are essential in early numerical studies, which typically represent the first step in detector's feasibility assessment. This paper focuses on quantifying implications of numerical model complexity on computational studies of skin spectroscopy. In our comparative numerical studies, we constructed one finger model that follows anatomical structures, as well as its three simplified versions, subjected to simulated measurements with a slim dielectric probe in the 0.5-50 GHz range. Using the finite-element method (FEM) for simulation, we analyzed mesh count to estimate computational cost and return loss variation to assess model reliability. As a result, we reach recommendations for models that optimize computational resources and can yield meaningful information from the standpoint of skin cancer screening. Simplified models are adequate for lower microwave frequencies (< 10 GHz), but at higher frequencies, models with at least three tissue layers (skin, fat, and ligament) are necessary. Modeling smaller tumors requires greater tissue complexity than larger tumors to achieve comparable reliability. Additionally, squamous cell carcinoma (SCC) scenarios demand higher model complexity than basal cell carcinoma (BCC) and melanoma to achieve similar reliability.

A very compact MIMO antenna for broad-band applications which covers the complete spectrum of X-band applications is represented here. The proposed element in the represented antenna covers a total volume of around 320 mm³. The isolation among radiating elements is improved by placing individual elements orthogonally thereby improving isolation better than 20 dB. This enhanced isolation helps to provide substantial MIMO parameters including ECC, TARC, channel capacity loss, and multiplexing efficiency. The devised antenna is compact (0.066λ × 0.066λ × 0.0024λ mm³) printed over an FR4 substrate which is widely available concerning 6.2 GHz to 11.2 GHz wireless applications. Fabrication of the above-mentioned proposed antenna is done and all the desired calculations are made desirably. Furthermore, the practically measured results conclude that the antenna-measured patterns well correspond to the simulated results.

In order to reduce the coupling between dense antenna arrays in multiple input multiple output (MIMO) systems, this paper proposes a method to reduce the coupling between microstrip antenna arrays by utilizing a defected ground structure (DGS), which consists of ``W''-shaped slits etched in the ground plane. Simulation results show that the structure can achieve -46.6 dB isolation between antenna arrays. To verify the effectiveness of the structure, the microstrip antenna arrays loaded with this DGS are fabricated and measured, and the measured results are consistent with the simulated ones, which verifies the effectiveness of the structure.

We present a self-synchronized dual-color cross-phase-modulation mode-locked (XPM ML) fiber laser with excellent wavelength tunability and signal-to-noise ratio for coherent anti-Stokes Raman scattering (CARS) detection. Cross-phase-modulation gives rise to self-synchronization between the two-color lasers, which enables rapid wavelengths scanning as time delay of the master laser cavity is electrically adjusted. The synchronized cavity without any mode-locking elements helps to improve the mode-locking stability and resistance to environmental interference. The pump (780 nm, 18.5 ps) and Stokes (881.1-899.4 nm, 1.5 ps) pulses obtained by second harmonic generation (SHG) are then sent to a focusing lens for CARS detection for scanning Raman shift of 1470-1701 cm^-1). As an example of analyte, rhodium-bisphosphine complex catalyst samples are detected. This highly stable and fast-tunable two-color XPM synchronized mode-locked laser architecture has the potential for arbitrary waveband extension would greatly improve the possibility of coherent Raman scattering imaging technology from the laboratory to practical applications in e.g. biomedical detection.

A novel compact low-profile Conformal Dielectric Resonator Antenna (CDRA) for wideband applications is proposed. By employing a specially designed dielectric resonator in conjunction with an inverted-trapezoidal patch for feeding, an extensive Impedance Bandwidth (IB) of around 51.5% is realized. The resonant frequencies of 6GHz and 7.5GHz correspond to the observation of the TE21δ mode and the second higher-order TE23δ mode, respectively. Moreover, a realized peak gain of 7.2dBi is attained at 7.4GHz. The proposed DRA offers a wide IB with more than 90% radiation efficiency throughout the bandwidth. Additionally, a good alignment is observed between the measured and simulated results. The proposed DRA is compact and low-profile of 0.1λg, where λg represents the wavelength at the lower cut-off frequency. A CDRA with a conformal feed is an innovative design tailored for wireless communication systems operating within the frequency range from 5.2GHz to 8.8GHz. This antenna configuration is specifically engineered to exhibit conformal properties, enabling it for applications such as the exteriors of vehicles, aircraft, or other non-planar structures.

In this paper, a frog-shaped ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna is proposed for 5G applications in the n77, n78, n79, and 6 GHz bands with a compact antenna structure of 31×55×1.5 mm³. The designed antenna consists of two frog-shaped monopole antennas and a floor from which part has been removed, and the operating bandwidths range from 3.05 to 13.38 GHz, which meets the design criteria for UWB. The T-shaped floor with two T-shaped slots impedes the flow of coupling currents and improves the isolation of the antenna. This results in an isolation of less than -17 dB over the entire operating bandwidth and less than -20 dB in the 5G band. In addition, the envelope correlation coefficient (ECC) is less than 0.007, the diversity gain (DG) more than 9.96, the total active reflection coefficient (TARC) less than -30 dB, and the channel capacity loss (CCL) less than 0.34 bit/s/Hz. The measured and simulated results agree with each other, demonstrating their potential application in 5G communication systems.

In this study, we introduce a dual-modal fluorescence hyperspectral micro-CT system developed for e.g. bioimaging applications. The system integrates an X-ray computed tomography (CT) module with a custom-designed hyperspectral fluorescence imaging module, achieving high-resolution structural imaging with detailed molecular-level insights. With a spectral resolution of 10 nm across the wavelength range of 450–750 nm, the hyperspectral fluorescence imaging module enables a fine compositional analysis. Using surface-modified nanoparticles, we demonstrate the system's capability to capture fluorescence under both X-ray and UV excitation. Imaging experiments on a mouse model further highlight the system's ability to generate comprehensive Four-dimensional (4D) datasets that integrate spatial, spectral, and structural information. To the best of our knowledge, no such a dual-modal system or the like has even been reported before. This dual-modal approach enhances the visualization and analysis of biological tissues, offering promising applications in e.g. disease diagnosis, surgical guidance, and preclinical research.

In the past decades, with the increasing complexity of topological crystals, artificial electromagnetic (EM) materials, and EM environments, understanding their precise scattering behaviors and characteristis is turning more challenging. Traditional methods for modeling these properties often rely on full-wave simulations or analytical algorithms which are only applicable for regular shapes with plane wave incidences. These methods are inefficient for the design and broadband multiple scattering analysis of general 3D EM structures, as new simulations are required for each different scattering scenario and frequency, while solving a substantial number of unknown variables in each analysis. In this paper, a novel hybrid numerical scattering T-matrix extraction method applicable to scatterers of arbitrary shape and composition is developed in the context of the Foldy-Lax multiple scattering theory (F-L MST). Generalization is also made such that the F-L MST can be applied to multiple scattering problems with arbitrary incident fields. Once the T-matrix elements of individual scatterers are obtained through combining spherical wave expansion with full-wave numerical simulations of surface fields as proposed in the paper, it can be stored and reused, significantly reducing the overall computational complexity. Compared to conventional methods, this approach merely requires matrix inversions of moderate orders in a multiple scattering problem, offering notable efficiency advantages for about an order of magnitude. Meanwhile, the smooth frequency dependence of the T-matrix elements and incident field coefficients suggests the feasibility of interpolating these coefficients for broadband simulations. This proves particularly helpful in the swiftly evolving near-field techniques, and scenarios requiring extensive analysis such as broadband and Monte Carlo analysis. Numerical cases, involving multiple scatterer shapes and arrangements, are explored and compared with COMSOL full-wave simulations. The results validate the accuracy and efficiency of the proposed method, with potential to become a powerful tool for EM simulations and optimization of various wave-functional materials and in many other multiple scattering applications.