In this paper, a novel miniaturized microstrip branch-line coupler (BLC) with good harmonic suppression using radial stub loaded resonators is proposed. The novel structure has two significant advantages, which not only effectively reduces the occupied area to 10.3% of the conventional BLC at 0.5 GHz, but also has high 14th harmonic suppression performance. The measured results indicate that a bandwidth of more than 121 MHz has been achieved while the phase difference between S₂₁ and S₃₁ is within 90° ± 1.5°. The measured bandwidth of |S₂₁| and |S₃₁| within 3 ± 0.4 dB are 146 MHz and 151 MHz, respectively. Furthermore, the measured insertion loss is comparable to that of a conventional BLC. To validate the design concept, a new miniaturized planar BLC with good harmonic suppression using radial stub loaded resonators is designed and fabricated. Simulated and experimental results are achieved with good agreement.

In this paper, a half-mode substrate integrated waveguide (HMSIW) semi-circular cavity backed antenna, using two higher order modes (TM₂₁₀ and TM₀₂₀), has been proposed for dual-band operation. A semicircular slot is engraved on the top of the HMSIW structure forming a cavity that is fed by co-axial feeding to get impedance matching with the line. The theoretical operation of TM₂₁₀ and TM₀₂₀ modes is explained using the simulation tool. The antenna parameters such as reflection coefficient, gain, and radiation patterns have been measured for the fabricated antenna. The antenna radiates in two bands, in which the first band center frequency is 8.5 GHz, and the second band center frequency is 10.6 GHz. Peak gains at boresight direction are around 7.5 dBi and 6 dBi, respectively.

A novel dual-band circularly-polarized slot array antenna aimed at LEO satellites communications where up-link and down-link operate at different frequencies is introduced. By using higher order modes, the slots can be placed at points where current distributions are null for the fundamental mode. According to this idea, at the receiver frequency band the slots are placed to be excited by mode TE₁₀ currents distribution, and at the transmitting band slots are forced to radiate according to mode TE₂₀ currents distribution. A matching load termination is used to generate the required travelling wave to obtain the circular polarization, introducing low dissipation losses. Additionally, in this investigation an antenna feeder is also designed. Both the feeder and the slot antenna array are designed using Substrate Integrated Waveguide (SIW). The use of SIW makes easier the design of the transitions from the array to the microstrip input lines and the grounded-coplanar termination as well, relaxing fabrication constraints and tolerance.

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.

In this paper, a differentially-fed, multi-band patch antenna with bandpass filtering response is proposed. The antenna consists of two pairs of crossed dipoles, four Γ-shaped feedlines, and four steeped-impedance microstrip lines. With the introduction of Γ-shaped feedlines and U-shaped slots on the radiating patch, extra radiation nulls are induced, four operation bands with band-pass filtering response are obtained. More importantly, the filtering response of the antenna is generated without any filtering circuit, which is easy to design for antenna engineers. Measured results of the prototype show that the proposed antenna has stable radiation patterns with low cross-polarization of better than -26 dB. Besides, bandpass filtering response of the realized gain with deep roll-off can also be observed between different operation bands. Excellent radiating performance make it a promising candidate for 5G wireless communication systems.

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.

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.