Electromagnetic scattering from the sea surface is of great significance in ocean remote sensing especially under high wind conditions. A novel volume-surface composite scattering model of nonlinear rough sea surfaces with breaking waves and foam layers under high wind conditions is presented in this study. Based on the semi-deterministic facet scattering model (SDFSM), using a ray tracing method combined with impedance equivalent edge currents (RT-IEEC) and vector radiative transfer theory (VRT), the backscattering characteristics of the sea surface with breaking waves and foam layers are investigated. The crest- and static-foam coverage was introduced to determine the breaking point and foam coverage distribution. The dependence of the backscattering coefficient of thesea surface with and without breaking waves and foam layers on the incident angle, wind speed, and the polarization are discussed in detail. The results of thenumerical simulations are analyzed and compared with the measured data from the relevant references which verifies the validity of our volume-surface composite scattering model. The synthetic aperture radar (SAR) image simulations of the surface with and without the breaking waves and foam layers are compared, and the combined effects of the breaking waves and whitecaps are analyzed.

In this work, two different high-frequency filters were produced, and each was manufactured in two different ways, one using conventional PCB technology and the other using hybrid 3D printing. The hybrid 3D printing technique combined the use of microdispensing of conductive inks and fused filament fabrication (FFF) of thermoplastic substrates. Measurements, properties, and comparisons between these filters are discussed. The goal of the research was to benchmark 3D printing of high-frequency filters to more confidently manufacture sophisticated devices and high-frequency systems by hybrid 3D printing.

A sparse imaging-based clutter suppression method for one channel synthetic aperture radar (SAR) is proposed in this paper. The Doppler characteristic differences between the radar received signal of clutter and moving targets are utilized in this method. A joint projection operator is formulated, and the norm constraint is employed to realize and promote clutter suppression. The reconstructed MT results with suppressed clutter can be applied to moving target detection and imaging. Numerical simulation can verify the validity and robustness of the proposed methodology.

The paper is devoted to an investigation of two-conductor suspended-substrate resonators. For the purpose of miniaturization conductors of a resonator are folded. Four types of the resonator differing in conductors' configurations were considered. Their Q₀-factors and resonant frequencies were studied. Based on results of the study two types of the resonator appeared unsuitable for an application in compact filters. Two other types were investigated in concern of their interaction: dependencies of coupling coefficients versus space between resonators and ver-sus distance from substrate's surfaces, and package's covers were obtained. Based on the depen-dences a type of the resonator suitable for designing compact BPF was chosen. A four-pole BPF was simulated and fabricated. Good agreement between simulated and experimental results is observed. The main filter's characteristics are the next: substrate has ε = 80, thickness 0.5 mm, lateral sizes 0.13λ_g × 0.09λ_g (18.7 mm × 13.2 mm). The central frequency is 305 MHz; bandwidth is 39 MHz; passband minimum insertion loss is 2.0 dB; passband return loss is less -14.6 dB; -40 dB stop-band width is 480 MHz.

To study the transient magnetic field and temperature field of a dry-type transformer core and analyze the core loss and hot spot temperature rise of the core, a magnetic and temperature field coupling analysis method based on finite element method was proposed: the transient magnetic field of dry-type transformer was calculated first, and the core loss under a no-load condition was obtained. Then, the core loss density distribution was coupled to the temperature field as the heat source, and the temperature field distribution in the transformer was calculated by the fluid-thermal coupling method to obtain the hot spot temperature and the position of the core. Compared with the traditional average heat source method, the temperature field distribution calculated by the proposed method is close to the actual temperature distribution of the core. Finally, based on this method, the magnetic field and temperature field of the transformer core under different excitations were calculated, and the effect of harmonics on the core loss and temperature rise of the core was analyzed.

In this paper, microwave breast cancer detection is investigated using the Ultra-Wide Band (UWB) radar imaging technique. A novel calibration approach based on the Estimation of Signal Parameters via Rotational Invariance Technique (ESPRIT) is used and adapted to work in this field. Using this method, many high amplitude undesired responses can be removed like early time clutter, late time clutter, and the mutual coupling between antennas. Using an electromagnetic simulation tool, a numerical phantom with a heterogeneous structure and dispersive dielectric properties is made for simulating the interactions of the electromagnetic fields with various breast tissues and investigating the proposed approach. The calibrated signals show the capability of the proposed algorithm in separating the tumor/glandular responses from the clutter. Also, the results of the proposed algorithm are compared with the Wiener algorithm results which are considered one of the best techniques to remove clutter, reduce late time clutters in the multistatic, and enhance the beamformer algorithm performance. Moreover, we propose the use of Transmitting-Receiving Antenna Separation Distance (TRASD) to limit the reflection angles from the voxel under the calculations of DAS and IDAS beamforming algorithms.

A dual circularly polarized (CP) substrate integrated waveguide (SIW) cavity-backed antenna with the feasibility of obtaining a wider bandwidth and relatively smaller size than other homogeneous referenced antennas is proposed and demonstrated. Fed by a quadrature hybrid coupler, the proposed double-layered stacked antenna, consisting of a perturbed circular SIW cavity and an improved circular patch radiator, is designed, analyzed and fabricated. Good agreement between simulated and measured results is observed. Simulation and measurement results reveal that the proposed antenna can provide impedance bandwidths of 45.7% (4.74-7.55 GHz) and 46.2% (4.75-7.6 GHz), as well as 3-dB axial ratio (AR) bandwidths of 37.5% (4.74-6.93 GHz) and 37.2% (4.75-6.92 GHz) for RHCP and LHCP, respectively. Meanwhile, within the effective RHCP/LHCP bandwidths, the proposed antenna has gains from 4.8 dBic to 7.6 dBic with an average gain of 6.4 dBic for RHCP, and gains from 4.9 dBic to 7.5 dBic with an average gain of 6.3 dBic for LHCP, respectively. Additionally, the measured effective dual CP bandwidth of 37.2% (4.75-6.92 GHz) not only meets the need for certain Wi-Fi (5.2/5.8 GHz) or WiMAX (5.5 GHz) band communication application, but also provides the potential to implement multiservice transmission.

We propose a new approach to design multi-bit coding metasurfaces (MSs) for broadband terahertz scattering reduction. An anisotropic graphene-based element with multiple reflection phase responses is modeled using the Method of Moments combined with the Generalized Equivalent Circuit's approach (MoM-GEC). The multi-level reflection phase response is adjusted by tuning the graphene chemical potential of each cell. On the first hand, based on the coding metamaterials concept, 1-bit MS building blocks are nominated as ``0'' and ``1'' elements with opposite phase responses 0˚ and 180˚, respectively. Therefore, genetic algorithm (GA) is employed to search the optimal reflection phase matrix and determine the best coding metasurface layout. In order to validate our design strategy, 4x4, 8x8, 16x16, 32x32, and 64x64 arrays (MS) are modeled and show a great agreement with the desired low Radar cross section (RCS). On the other hand, 2-bit and 3-bit coding metasurface are then designed using two different sets of reflection phases {0, 60, 120, 180} and {0, 30, 60, 90, 120, 150, 180, 210}, respectively.

A novel beveled triple band rejection UWB monopole radiator is presented. The reference UWB antenna incorporate a beveled radiator and partial ground structure for achieving UWB bandwidth from 2.73 to 11.05 GHz. For rejecting 3.78-4.36, 5.15-5.45, and 7.2-7.9 GHz for C, lower WLAN, and X-band applications, the reference UWB element is freighted with an inverted U-shaped slot etched into a radiating patch. A symmetrical split ring resonator pair (SSRRP) is proximate to microstrip feed, and a C-shaped parasitic stub is embedded on top of defected ground plane. The antenna is designed on an FR-4 substrate with 30 × 32.5 mm² size, having a realized average gain of 3.72 dBi and is nearly stable across the entire UWB excluding at three rejected bands.

In this paper a novel design of microstrip fed L-shaped arm slot and notch loaded RMPA (Rectangular Microstrip Patch Antenna) with mended ground plane for wide bandwidth is presented. The proposed prototype antenna is fabricated on an FR-4 (Fire retardant) substrate with dimension 30×30.8 mm² and 1.6 mm thickness. The proposed design is analyzed and simulated using high frequency structure simulator (HFSS) tool version 15. The analysed results are validated through fabrication and measurement results. The analyzed result shows 96.1% maximum radiation efficiency at 2.9 GHz whereas overall efficiency is more than 85% over the entire frequency range and experiment achieves gain 8.4 dB at 7 GHz. The designed antenna achieves 119.39% impedance bandwidth with more than 5 dB gain over the operating frequency range of 2.41 GHz to 9.55 GHz. For better performance and analysis of proposed antenna, a parametric study has been carried out to analyze the effects of variations in the following --- slot and notch dimensions loaded on the patch as well as variations in ground length. The designed antenna can be utilized for various applications incorporating Bluetooth, WLAN, Wi-Max, and UWB operation.

Characterizing the random errors at the elements of a phased array antenna leads to equations that estimate the associated performance degradation. The increase in sidelobe level and decrease in gain due to random errors is well established. This paper derives an expression that predicts the axial ratio degradation due to random errors in the circularly polarized elements of an array. In the case of small errors in an array of crossed dipoles, we found a simple expression for the axial ratio of the array under random errors at broadside.

The paper discusses the application of laser illumination and brightness amplification techniques for studying the process of high-temperature combustion of aluminum and iron nanopowders and their mixtures. The laser equipment for visualization based on solid-state laser illuminator, brightness amplifier on copper bromide vapors and high-speed camera is considered. These approaches allow the increase of monitoring distance to 50 cm, which is important for high-temperature processes imaging. The video images allow studying the surface morphology changes during high-temperature combustion identifying the main stages of the combustion, spreading of the heat wave and cooling.

In this paper, a novel wearable inkjet printed dual-band antenna is presented, which works at 2.45 GHz and 5.8 GHz for wireless body area network applications. The proposed antenna geometry is composed of two printed monopole elements, which are constructed from an analytical profile of an exponentially-decaying sinusoidal curve. The analytically parameterized curve allows for constructing on demand irregular and unique shaped miniaturized radiators. The antenna system is printed on a transparent flexible polyethylene terephthalate (PET) film. The wearable dual-band printed antenna with an overall size 45 x 40 x 0.135 mm³ is compact, light weight, and low profile, making it a suitable candidate for wireless body area network applications, when limited volume space for the worn unit is a requirement. Good agreement between numerical and measured data is achieved. Moreover, the overall far-field radiation performance of the wearable dual-band antenna is satisfactory, with measured peak gains of 1.81 dBi and 3.92 dBi, and a total computed efficiencies of 81% and 82% at 2.45 GHz and 5.8 GHz, respectively. The effect of bending the wearable antenna structure is also investigated, and only slight performance variations are observed.

Advancements in functionalities and operating frequencies of integrated circuits lead to the necessity to study Electromagnetic Compatibility/Electromagnetic Emissions (EMC/EMEs) from these devices. In this work, a methodology is developed, which combines near field electromagnetic measurements and 3D layout simulation of an Integrated Circuit (IC), to identify the sources of EME from a commercial IC. This methodology can help to narrow down the area of key importance with respect to EME sources, instead of the entire IC, before it is fabricated. Consequently, IC designers can optimize their design to minimize the EME before fabrication, saving cost and time significantly.

A very-low-profile, decoupled, hybrid two-antenna system top-loaded with a coupled strip resonator for isolation enhancement is demonstrated. Each hybrid antenna consists of one 2.4 GHz open slot and one 5 GHz monopole, formed on the two sides of the substrate. The two-antenna design is able to operate in the 2.4 GHz (2400-2484 MHz) and 5 GHz (5150-5825 MHz) wireless local area network (WLAN) bands and yet merely occupies a size of 5 mm × 40 mm (about 0.04λ × 0.32λ at 2.4 GHz). The loaded strip resonator is employed to reduce the mutual coupling in the 2.4 GHz band. With further capacitively grounding the decoupling strip using a grounded T strip, good isolation > 18 dB over the 5 GHz bands can also be achieved. Owing to its low profile of 5 mm, the proposed design can find some practical applications in the narrow-bezel notebook computers and is of the smallest footprint among those two 2.4/5 GHz antennas for notebook applications.

In this paper, a simple and effective side-lobe suppression technique is proposed by using integrated high refractive index matematerial (HRIM). It is known that current reversal, which occurs at the third harmonic of the dipole natural frequency, disturbs the omnidirectional radiation pattern of a dipole antenna, and the main beam splits into two side lobes. For suppressing the two side lobes and maintaining consistent radiation pattern purposes, two regions of HRIMs are integrated along the side-lobe radiation direction of a reflector-backed dipole antenna to tilt the two side lobes toward the broadside radiation direction. The HRIM is constructed with 2X3 H-shaped unit-cells periodically printed on the single side of dielectric substrates. The beam-tilting approach described here uses the phenomenon that the EM wave undergoes a phase shift when entering a medium of different refractive indices. Simulation and measurement results show that by implementing the HRIMs, the two side lobes are tilted toward the broadside radiation direction, and as a result, the side lobe is suppressed, and radiation consistency for the first and third harmonic resonances is realized. Moreover, the antenna gain for the third harmonic is achieved as high as 7.8 dBi, which is an increase of approximately 3 dBi compared with the fundamental resonance.

This paper proposes a coplanar waveguide-fed slot antenna with vertical rounded bow-tie slots for wideband harmonic suppression. Higher-order harmonics up to nine times the fundamental resonant frequency (9f_o) of the slot antenna was successfully suppressed by adding the slots in the middle of the two slot arms. A prototype of the antenna that resonates at 1 GHz was fabricated. The measured input reflection coefficient of the antenna remains over -3 dB at up to 9.15 GHz, which demonstrates the wideband harmonic suppression capabilities.

This paper presents a piezoelectric transducer-tuned fourth-order bandpass filter (BPF). The proposed filter consists of four open-loop resonators which form cascaded quadruplet (CQ) sections with a capacitive cross coupling. There are two transmission zeros (TZs) in the lower and upper stopband to further improve the selectivity of the filter. The structure parameters are optimized by using High Frequency Structure Simulator (HFSS). The piezoelectric transducer (PET) together with a dielectric substrate is used as a tuning element. The effects of the PET on the coupling coefficient and external quality factor are analyzed. The designed tunable filter has been manufactured and measured. The measured results show that the center frequency of the filter changes from 2.48 GHz to 2.28 GHz; the insertion loss basically keeps constant; 3 dB bandwidth of the filter changes from 156 MHz to 168 MHz over the tuning range; and the positions of the TZs in the stopband move synchronously as the center frequency varies.

To improve computational efficiency of traditional method for solving separable multi-objects scattering problems, each subdomain impedance matrix is sparsified by biorthogonal lifting wavelet transform (BLWT) without allocating auxiliary memory, and a sparse underdetermined equation is constructed by enjoying the prior knowledge from known excitation in wavelet domain, then orthogonal matching pursuit (OMP) is employed to fast and accurately solve the sparse underdetermined equation under compressive sensing (CS) framework. Numerical results of separable perfectly electric conduct (PEC) multi-objects are presented to show the efficiency of the proposed method.

Transmission/reflection method is widely used in microwave engineering for determining dielectric properties of materials, and significant uncertainty will arise in the results if the thickness of the samples is small. In this paper, we propose animproved algorithm for deducing complex permittivity of thin dielectric samples with the transmission/reflection method. With the proposed algorithm, the real and imaginary parts of the complex permittivity will be treated separately, and two independent weighting factors, β_re and β_im, will be used to minimize the uncertainty in both parts ofthe complex permittivity. Numerical calculations as well as experimental measurements on undoped and boron-doped diamond films were conducted within the frequency range of 18.5-26.5 GHz to demonstrate the effectiveness of the algorithm. It is verified that among the various iterative algorithms which could be used to derive complex permittivity, the proposed algorithm is the most advantageous inreducing uncertaintieswhen thin dielectric samples are dealt with.