Lasers emitting visible light based on high harmonic generation (HHG) have significantly enhanced measurement capabilities, enabling new applications across precision metrology, attosecond science, and ultrafast time-resolved spectroscopy. This paper discusses the theoretical framework of HHG with a focus on nonlinear effects, examining in depth second-harmonic generation (SHG) and third-harmonic generation (THG) mechanisms, as well as a thermal nonlinear model for pump stability analysis. The current state of HHG within integrated optical circuits is reviewed, with a particular emphasis on its implementation in high-index doped silica glass micro-ring resonators (HDSG MRRs). We conclude by addressing future directions for optimizing these systems to expand their applicability in advanced photonic technologies, highlighting their potential for innovation in both applied and fundamental sciences.

To solve the problem of low accuracy and real-time performance of direction of arrival (DOA) estimation in an impulsive noise environment, this paper proposes a single-snapshot DOA estimation method based on the median deviation correntropy of hyperbolic tangent kerne and designs an intelligent optimization algorithm for the segmentation and hunting mechanism of gold long-nosed raccoon to obtain accurate DOA estimation angle. The DOA estimation method proposed in this paper uses spatial smoothing technology to process the median deviation correntropy of single snapshot data, and then uses the hyperbolic tangent kernel to remove impulse noise from the pseudo-covariance matrix. The weighted signal subspace fitting method is used to obtain the accurate DOA estimation angle. The Monte Carlo analysis experiments of different schemes are verified, especially in the case of a single snapshot, low generalized signal-to-noise ratio (GSNR), and strong impulse noise.

A method for significantly improving the bandwidth of microstrip patch antennas is proposed, utilizing dual-layer metasurface (MS). The antenna employs coaxial probe feeding and consists of a truncated patch, an upper layer of 4 x 4 periodic N-shaped MS and a lower layer of 3×4 rectangular MS. By introducing multiple resonances via the dual-layer MSs, impedance matching of the patch antenna is greatly enhanced. Its overall geometric dimensions are 1.09λ₀ x 1.09λ₀ x 0.14λ₀ (f₀ = 5.5 GHz), and compared with patch antennas and single-layer metasurface antennas of the same size, it can substantially enhance the bandwidth and gain without significant cost and size increase. The proposed MS antenna operates from 4.7 to 6.66 GHz (39.8% fractional bandwidth), covering two-thirds of the C-band, with a peak realized gain of 9.3 dBi. Within 4.47-5.56 GHz, the realized gain of the antenna remains above 7.5 dBi, and the average gain across the entire operating band is 7 dBi.

The circularly polarized design of a 350° sectoral microstrip antenna is proposed. Orthogonal surface current components at TM₁₀ mode on the sectoral patch provide circularly polarized characteristics. With the substrate thickness of 0.087λ_cAR, it yields the simulated axial ratio bandwidth of 18 MHz (1.9%) that lies inside the reflection coefficient bandwidth of 487 MHz (44.66%). A reduction in the substrate thickness by 0.012λ_cAR in the 350° Sectoral design is achieved by employing an H-shape ground plane profile. This design yields the axial ratio bandwidth of 13 MHz (1.45%), which is present inside the reflection coefficient bandwidth of 386 MHz (36.9%). The antenna using modified ground plane offers peak broadside gain of larger than 6 dBi. On conventional and H-shape ground plane design, reconfigurable design of 350° Sectoral patch is presented that offers switching between the wideband and circularly polarized characteristics. For operation at TM₃₀ mode in the Sectoral patch, circularly polarized reconfigurable configuration for sectoral angle decreasing from 340° to 280° is presented. Over this angle variation, antenna offers tuning in the center frequency of axial ratio bandwidth by 367 MHz (20.6%) with a broadside gain of larger than 5 dBi. A design methodology for circularly polarized antennas functioning at TM₁₀ and TM₃₀ modes is proposed. It helps in realizing similar configuration as per specific wireless application. Experimental verifications for all the obtained results are carried out which show close agreement with the simulated results.

In response to the growing demands of modern communication systems for miniaturized devices, high selectivity, and multi-band characteristics, this paper proposes a design methodology for a dual-band filter based on a planar interdigital structure. Two dual-band filters are developed utilizing transmission zeros and cascading techniques. The filters exhibit high selectivity and wide stopband performance. They are also tunable through parameter adjustments while maintaining a compact form factor. By incorporating composite right/left-handed (CRLH) theory, the proposed filters demonstrate left-handed characteristics. Simulation and experimental results indicate that the designed filters achieve low insertion loss, a wide stopband, and excellent out-of-band rejection within the target frequency bands. Additionally, compared to existing designs in the literature, this approach offers notable advantages in terms of both size and performance. The findings of this study show significant potential for applications in RF and communication systems.

In this paper, a ray-tracing based mathematical model is proposed for the analysis and design of Fabry-Perot antennas with a nonuniform Partially Reflecting Surface (PRS). The use of nonuniform PRS in FPA's has recently gained attention due to its immense applications such as directivity enhancement and beam-steering. A spatially varying phase profile of the PRS is achieved by the arrangement of various distinct unit cells throughout the surface. The PRS phase and magnitude variation enables the alteration of wavefronts to achieve beam steering along a desired polar and azimuth angle (θ, Φ). Thus, a simple, robust and computationally efficient model to find the optimal FPA parameters and phase profiles for beam-steering has been developed in this paper. FPAs were designed using a square PRS for 1-D and 2-D beam steering with gains of up to 17 dBi. The model has been verified with the simulated results at 8 GHz and 8.5 GHz, demonstrating consistent field patterns with the full-wave simulations.

This work presents a new compact split-ring resonator (SRR)-loaded rasorber to achieve narrow in-band transmission while maintaining broad absorption over a wide frequency range. The unit cell on the top layer is made up of four 150-ohm lumped resistors and four modified split ring resonators that are capable of absorbing a wide range of frequencies. The bottom FSS layer comprises a multilayer cascaded structure where top and bottom most metal layers are inductive grids, and the middle-sandwiched layer is a folded square ring structure. This design serves as a band-pass filter, allowing in-band transmission frequencies to pass through and also serving as a ground plane for out-of-band frequencies. The proposed rasorber exhibits an absorption bandwidth of 124% for frequency band starting from 2.5 GHz to 9.5 GHz, which covers mostly ISM and Satellite communication bands. The rasorber also acts as a transparent structure with insertion loss of 1.3 dB at the IOT band of 4.8 GHz. The novelty of the rasorber lies in achieving a very narrow transmission bandwidth with sharp roll off and is well suitable for radome applications having high selectivity. The innovation in this design comes from its combination of wide out-of-band absorption, narrow in-band transmission, high angular stability up to 50° for oblique incidence, and a dual-polarized response. The study looked at polarization behavior, surface current distribution, and other important parameters to figure out how well the rasorber worked. The equivalent circuit response of the proposed rasorber is compared with simulated one to get more circuit level understanding. Our results indicate that the electrical equivalent circuit design closely aligns with the simulated data. The proposed rasorber is suitable for secure communication in defense, as a super-stratum on an antenna, with reduced RCS and stealth characteristics.

This paper presents the design and implementation of a novel S-band antenna utilizing low-temperature co-fired ceramic (LTCC) technology. LTCC enables low losses, efficient radiation performance, and robust packaging. The antenna operates at 2.4 GHz with a size of 40 mm x 26 mm and offers a gain of 5 dB. It features a −10 dB impedance bandwidth of 20 MHz within the frequency range of 2.39 GHz to 2.41 GHz with efficiency of 94%. This design highlights the adaptability of LTCC technology in producing antennas that excel in several application while maintaining a desirable balance of size and efficiency.

Uncertainty analysis has been widely used in electromagnetic compatibility (EMC) simulation. However, a comprehensive credibility assessment system for it has yet to be established. In this article, the concepts of failure domain and failure rate are introduced from the perspective of the practical application of uncertainty analysis methods. The study aims to assess the reliability of uncertainty analysis method from the perspective of system failure, providing a theoretical basis for guiding practical electromagnetic compatibility design through uncertainty analysis.

This paper proposes a broadband multi-input multi-output (MIMO) antenna array operating in the 3.3-6 GHz frequency range. The antenna array consists of eight identical Z-shaped radiation elements, and the coupling between the antenna elements is minimized through the use of an optimized defected ground structure. Each antenna element is composed of a modified Z-shaped radiation strip, an opposing L-shaped strip, and a rectangular strip. Based on simulation and measurement results, it can be concluded that the antenna array meets the -10 dB bandwidth requirement within the desired frequency band, with the transmission coefficient of less than -15 dB, and an envelope correlation coefficient (ECC) below 0.006. Additionally, the proposed antenna achieves a maximum gain ranging from 2.6-8 dBi, with an efficiency exceeding 76%. The overall size of the phone antenna is 150 × 75 × 7 mm³, while each antenna element measured only 7.8 mm × 7 mm × 0.8 mm (0.091λ × 0.082λ × 0.009λ, where λ represents the wavelength at 3.5 GHz). The high-isolation broadband MIMO antenna proposed in this study emerges as a promising candidate for fifth-generation (5G) New Radio (NR) and WLAN applications.

Super fast charging is a key solution to addressing the issue of electric vehicles. In response to the demand for increased current-carrying capacity and lightweight cables in super-fast charging system, optimization design and verification were conducted in this study employing a multi-physics field analysis method. A single-core cable was selected as the research subject, and both the Ohmic loss and temperature distribution were analyzed under the excitation of electric vehicle cold charging current. The influence of different cable core shapes, coolant flow rates, cooling channel structural parameters, and other factors on the maximum temperature rise of the charging cable were compared and analyzed. The calculation results indicated that, under the identical cable core cross-sectional and operating conditions, rectangular cross-section cables exhibited superior heat dissipation performance compared to circular cross-section cables. It was found that the flatter the cable core is, the better the heat dissipation performance is. Under specific operating conditions, the cross-sectional area of the flat linear shape could be reduced appropriately, as increasing the size of the liquid cooling channel would help reduce the overall mass of the cable. These findings provide valuable insights for enhancing the heat dissipation performance and lightweight design of liquid-cooled charging cables in supercharging applications.

A simple, low-profile, and broadband antenna is presented in this paper for bandwidth enhancement. The compact antenna is achieved through a 50% miniaturization of a full-mode substrate integrated waveguide (FMSIW) antenna, known as the half-mode substrate integrated waveguide (HMSIW). The low-profile design is the result of the thin substrate thickness. However, the miniaturized and low-profile antenna suffers from narrow impedance bandwidth, which limits its application in antenna implementations. To address this issue, this paper proposes a broadband antenna in a single HMSIW cavity, offering a simple solution. The broadband performance is achieved by the merging of triple resonances. These triple resonances are generated by the combination of TE₁₀₁, TE₁₀₂, and TE₂₀₂ modes, which are induced by a semi-rectangular ring slot on the top layer of the cavity. Good agreement is observed between the simulation and measurement results. The simulated fractional bandwidth (FBW) is 29.53% (9.67-13.02 GHz), while the measured FBW is 32.05% (9.51-13.14 GHz). Two identical antennas with different polarization directions are obtained by mirroring one of them with respect to the other.

In this study, a quad-port ultra-wideband (UWB) multiple input multiple output (MIMO) antenna with triple band-rejection characteristics is demonstrated. The suggested diversity MIMO antenna comprises four similar rectangular radiators positioned in orthogonal manner by utilizing polarization diversity. For superior interelement isolation, a fan-shaped decoupler is lithographed on the back of the substrate. The MIMO antenna exhibits an operational bandwidth of 9 GHz (3-12 GHz) for each port, with |S₁₁| ≤ -10 dB. This version is more concise and properly formatted. The MIMO aerial exhibits an impedance bandwidth 3-12 GHz) for each port (|S₁₁| ≤ -10 dB) along with an interelement isolation exceeding 20 dB. Additionally, to exclude the 3.5-4.1 GHz (downlink C-band), 4.43-4.79 GHz (INSAT), and 5.25-5.71 GHz (Wireless LAN) bands that coexist in UWB spectrum, the antenna elements are equipped with three U-shaped slots. The MIMO diversity metrics, including isolation, envelope correlation coefficient, diversity gain, TARC, CCL, multiplexing efficiency and group delay, were computed and reported. The reported aerial prototype has been constructed, and the measured results have been validated against the simulated findings.

A low-profile monolayer filtering antenna with compact size is presented in this paper. The antenna features a simple structure, comprising a substrate, a stepped defective ground structure, an asymmetric Y-shaped branch, and a microstrip feedline with an L-shaped branch. The asymmetric Y-shaped branch and L-shaped branch feedline collaborate to introduce two additional resonant frequency points, thereby broadening the impedance bandwidth. Furthermore, two radiation nulls are introduced on either side of the passband, which enhances the frequency selectivity of the band edges and optimizes the antenna's radiating and filtering performances. To verify the proposed design, a prototype of the compact filtering antenna was fabricated and measured. The measured and simulated results show good agreement. The design achieves a wide impedance bandwidth of 44.6% (4.88~7.68 GHz) at a center frequency of 6.22 GHz, a peak realized gain of 5.7 dBi, and a compact size of 35 mm × 29 mm × 0.8 mm. Two radiation nulls on either side of the passband result in an excellent bandpass response, with out-of-band rejection reaching 18.2 dB. Finally, the antenna's excellent radiation performance and filtering characteristics make it suitable for wireless communication applications in the 5G Sub-6 GHz and WiFi-6E bands.

This work is focused on predicting the return loss and gain characteristics, where a new MIMO-OFDM radar waveform design is proposed and then simulated for a line impedance antenna system. A suggested radar waveform is implemented on an FR4 substrate normally used in microwave applications. It is obtained that, after extensive modeling, the return loss for the MIMO-OFDM radar waveform is -31.7265 dB at a frequency of 6.86 GHz, thereby showing minimum reflection and good impedance matching. At this frequency, the gain for the system comes out to be 7.1276 dB, which refers to the fact that this waveform would help in enhancing the performance of radar systems. These results demonstrate how the MIMO-OFDM radar waveform can be used for advanced radar applications because it gives better return loss and gain, some of the critical specifications required for high-performance radar systems.

The early detection of brain tumors presents significant challenges due to the complexity of the brain as well as the need for noninvasive diagnostic tools. This study introduces a novel antenna design optimized for noninvasive brain tumor detection. In this work, a cross slotted circular patch with a rectangular slot in the ground plane is designed in the simulator for brain tumor detection. The designed antenna operates from 1.76 GHz to 13.6 GHz with an impedance matching of greater than -10 dB. The antenna attains a peak gain of 5.8 dBi at 8 GHz. The antenna has been fabricated using the Monolithic Microwave Integrated Circuit (MMIC) technology and then tested in an anechoic chamber environment. The simulated and measured antenna performance parameters are found in agreement. The developed antenna has been used to image a target containing liquid inside a bottle covered by foam material. The liquid inside the bottle mimics the tumor material as its dielectric constant is comparable to a realistic tumor material. The target has been successfully reconstructed using the Delay and Sum (DAS) approach.

This paper presents a new 3D-printed, compact Double-Ridged Conical Horn (DRCH) antenna designed for Ultra-Wideband (UWB) Microwave Imaging (MI). The performance of the proposed antenna is analyzed using an electromagnetic (EM) solver, which demonstrates favorable return loss, gain, and radiation characteristics, indicating its structural and performance robustness. To validate the final design, a prototype is fabricated and tested experimentally. The proposed model features reduced dimensions compared to traditional and commercially available Dual Ridge Horn (DRH) antennas, while still maintaining a broad operational bandwidth (|S₁₁| > -10 over the 0.69 GHz-12 GHz range). Within the variety of potential applications, this frequency band is particularly suitable for biomedical devices, particularly in MI, where compact size is crucial for seamless integration into these systems. Additionally, a safety evaluation of the designed antenna has shown that its Specific Absorption Rate (SAR) is well below regulatory limits, ensuring that it can be safely operated near human users.

A four-port, extremely wideband MIMO array antenna is designed for 5G applications. A single element antenna composed of a two-ring-shaped patch with a partial ground plane is designed. It is then converted into a 1 x 2 array, four arrays of such are placed orthogonally to each other in a MIMO system to get good isolation among them. A Roger substrate with permittivity of 2.2, loss tangent of 0.0009, and thickness of 0.254 mm is used. The antenna arrays of the MIMO system are operate in the range from 24 GHz to 51 GHz with good isolation of more than 22 dB. The peak gain of the MIMO system is 7.4 dB with a bi-directional radiation pattern and efficiency of more than 96%. Also, the overall size of MIMO antennas is compact, with dimensions 18 x 18 x 0.254 mm³. For further verification, the measurements of the fabricated prototype were carried out as well, and a very reasonable agreement with simulated results was achieved which guaranteed the prototype’s strong MIMO performance. The proposed array MIMO system, owing to its various properties, is a potential candidate for mm-wave 5G applications, mm-wave vehicular communication, and the Internet of Things (IoT).

In the complex marine environment, the receiver is susceptible to the influence of water flow, which will cause the mutual inductance to fluctuate, thus affecting the stability of the output current. Therefore, aiming at the problem that the coil is prone to offset, this paper proposes a constant current charging output control method for wireless power transmission system based on parameter identification. Firstly, a method of mutual inductance parameter identification is introduced in detail. Only by measuring the effective value of the current at the transmitting end, the equivalent equation of mutual inductance and current can be established. Aiming at solving complex mathematical equations, the results of mutual inductance identification are obtained from high-order equations by combining with particle swarm optimization algorithm. Secondly, on this basis, a constant current control method for fast calculation of the conduction angle based on the above identification method is proposed. The calculation process of the conduction angle is derived, and the working principle of the constant current charging control is introduced in detail. Finally, this paper completed the construction of the experimental platform and carried out relevant experimental verification. The results show that the error of the parameter identification method proposed in this paper is within 3%, and the constant current output control of the system can be realized in the case of mutual inductance disturbance.

In this paper, a spatial-multiplexing-based transmission-reflection-integrated full-space metasurface (FS-MS) is proposed, which is applied to the generation of orbital angular momentum (OAM) beam. Using the principles of anisotropy and spatial multiplexing, the metasurface element is designed. The element consists of three dielectric substrates and four metal layers, which are of conventional cross-shaped and slotted cross-shaped construction. The designed element has the ability to independently modulate transmitted and reflected electromagnetic (EM) waves at 15 GHz. When EM waves with different polarizations are incident, the metasurface is capable of transmission at the incident x-polarized waves and reflection at the incident y-polarized waves. Using the designed element, the FS-MS was designed by combining the theories of OAM beam generation and phase superposition. The results show that the metasurface can generate the OAM beam with the topological charge of +2 in the transmission mode and +3 in the reflection mode at 15 GHz. The purity of the generated OAM beam is 78.88% in transmission mode, and 72.87% in reflection mode. The metasurface proposed in this paper is characterized by the integration of transmission and reflection, which is valuable for applications in wireless communications, sensing, and imaging.