In this paper, an efficient volume surface integral equation (VSIE) method with nonconformal discretization is developed for the analysis of electromagnetic scattering from composite metallic and dielectric (CMD) structures. This VSIE scheme utilizes curved tetrahedral (triangular) elements for volume (surface) modeling and the associated CRWG (CSWG) basis functions for volume current (surface) current modeling. Further, a discontinuous Galerkin (DG) volume integral equation (VIE) method and a DG surface integral equation (SIE) approach are adopted for dielectric and metallic parts, respectively, which allow both conformal and nonconformal volume/surface discretization improving meshing flexibility considerably. Numerical results are provided to demonstrate the accuracy, efficiency, and flexibility of our scheme.
The possibility to achieve a continuous tuning of the spectral properties in the case of two types of planar metamaterials based on the moire effect is demonstrated both experimentally and numerically. Tuning spectral characteristics are provided by changing geometric parameters of above-mentioned metamaterials. It is shown that for a one-dimensional moire metamaterial obtained by superposition of two microstrip photonic crystals with close periods, the position of the stopband in the spectrum can be controlled by changing these periods. We also consider the two-dimensional moire metamaterial formed by two identical periodic crossed structures with hexagonal symmetry. The ability to control the frequency of surface state mode by changing the crossing angle of these structures relative to each other has been shown experimentally and numerically. It is numerically demonstrated that, if the moire metamaterial is irradiated by the horn antenna, a surface wave propagating in the metamaterial plane appears in all directions beginning from its intersection point with the axis of the incident wave beam. In practice, moire metamaterials of this type can be considered as a promising prototype of microwave filters, whose spectral properties can be continuously and smoothly mechanically rearranged.
In this paper, an electrically small magnetic probe combined with principal components analysis (PCA) technique for microwave breast cancer detection is presented. The proposed magnetic probe is designed as an electrically small square loop antenna integrated with a matching network operating at 528 MHz. The concept of the proposed microwave detection is based on the shift in the resonance frequency of the near-field magnetic probe due to the presence of a tumor. The proposed magnetic probe is highly sensitive in detecting any changes or abnormality in the dielectric properties of the female breast tissues. Detecting the existence of the breast tumors is expected by estimating the variations in the scattering parameters of the probe's response. The PCA is a feature extraction technique applied to accentuate the variance in the sensor responses for both healthy and tumorous cases. It is shown that when a numerical realistic breast phantom with and without tumor cells is placed close to the magnetic probe in the near-field region, the probe is capable of distinguishing between healthy and tumorous tissues. In addition, the probe can identify tumors with various sizes placed in a specific location within the breast. As a proof of concept, the magnetic probe was fabricated and used to detect a 9 mm metallic sphere buried at three different locations inside a lump of chicken meat, mimicking both normal and tumorous breast tissues, respectively. The CST numerical simulations and experimental results demonstrate that the presented technique is an emerging modality for detecting breast tumors through an inexpensive and portable way.
Co-design of corner bent Multiple-Input Multiple-Output (MIMO) antennas catering to 4G LTE and mmWave 5G applications is proposed. The 4G LTE MIMO antenna module consists of two element microstrip-fed slot antennas operating from 1.7 to 3 GHz with fractional bandwidth of 55%, which covers LTE1900, LTE2300, and LTE2500 bands. For mmWave 5G MIMO antenna module, two element Vivaldi antennas with wideband operating from 25 to 38 GHz and fractional bandwidth of 41% are proposed. The mmWave 5G microstrip fed Vivaldi MIMO antennas exhibit orthogonal pattern diversity at 28 GHz with 1-dB gain bandwidth of 28%. The single element corner bent co-designed antenna is compact having dimensions of 14 × 51 × 0.254 mm3. The 4G LTE and mmWave 5G antennas are electrically close to each other by 0.01λ at 1.7 GHz for minimal physical footprint. Co-designed 4G LTE and mmWave MIMO antennas are integrated inside a typical mobile case. Simulated and measured results are presented.
An efficient microwave milk pasteurization system requires a rigorous temperature dependent dielectric model of the milk, since the performance of milk pasteurization strongly depends on its dielectric properties. This paper describes the dielectric modelling of cows raw milk during batch (Vat) pasteurization which covers the frequencies from 0.2 GHz to 6 GHz. An open-ended coaxial sensor is used for the measurements of dielectric constant, loss factor, and ionic conductivity at temperature range of 25°C to 75°C with an interval of 5°C. Combinations of Cole-Davison and Debye equations are modified to fit the dielectric measurements. It was found that the measured dielectric constant decreased as the frequency increased, while the high temperature processed produce lower in a convergence manner toward 6 GHz. The loss factor exhibited high losses at higher temperature and lower frequencies, as well as converged at 1.9 GHz then diverged up to 6 GHz. Three relaxation processes are dominated at all temperature treatments within the frequency range. The relaxation time, τ, and the activation energy, Q, are modelled based on linear fitting of measured data according to Debye and Arrhenius approaches.
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 0.13λg × 0.09λg (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.
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.
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.
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.
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.
Optimization design is a satisfactory way to improve the performance of magnetic bearing (MB). In this paper, a multi-objective genetic particle algorithm of swarm optimization (GAPSO) is proposed for homopolar permanent magnet biased magnetic bearings (HPRMBs). By assigning different inertia weights to each objective function, the multi-objective function is transformed into a new single objective function for optimization. In order to ensure the diversity of particles in the optimization process, genetic algorithm is used to cross-mutate them, which enhances the global search ability of particle swarm optimization. After optimization with GAPSO, the levitating force of the MB is increased by 22.3%, the volume decreased by 26.6%, and the loss reduced by 33.9%. The optimization results show that the multi-objective optimization based on GAPSO can effectively improve the performance of HPRMB.
The electrical network model and differo-integral method (D-IM) were applied to electrical parameters estimation of nonhomogeneous composite materials. The laminar composite is arranged of conductive unit cells with adjustable geometry. Modification of unit cell's internal geometry results in change of composite's effective properties. Stationary electric and magnetic fields of exemplary structures were numerically analyzed. Theoretical computations along with network model were verified by experimental measurements of 10 fabricated samples. Obtained results indicate that D-IM is a valuable tool for qualitative and quantitative estimation of electrical parameters.
A novel CPW-fed planar printed monopole antenna with broadband circular polarization (CP) characteristic is presented. The proposed antenna consists of a copper coin-shaped patch (CCSP) and an asymmetrical ground plane. To achieve a broadband CP wave, a vertical stub is added to the CCSP to produce orthogonal surface currents for right-hand circular polarization (RHCP). The design of the CCSP greatly increases the impedance bandwidth (IBW) of 89.2% which can cover the whole CP bandwidth of 71% completely. The measured results show that the proposed antenna has not only a broad 3-dB AR bandwidth (ARBW) of 71% (3900 MHz, 3.1-7 GHz) with respect to the CP center frequency 5.8 GHz, but also a wide 10-dB return loss bandwidth of 89.2% (5040 MHz, 2.16-7.2 GHz) centered at 5.65 GHz.
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, βre and βim, 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.
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