In this paper, a novel circularly polarized rectenna using a dual-feed array antenna with inclined patches is proposed to provide a dual-axis wide-angle reception capability. A new conical and pencil dualbeam circularly polarized array antenna integrating planar magic-Ts is designed and fabricated to overcome the polarization and main-beam misalignment between the transmitting and receiving antennas. To improve the rectenna's output power, open stub matching networks are used to achieve the impedance matching between the antenna and rectifying diodes. Two types of circularly polarized dual-axis rectennas which respectively allow the parallel and series connections of two diodes are experimentally evaluated and compared to confirm the wide-angle reception capabilities in the x-z and y-z planes.

A high selectivity compact size coupled open-loop resonator (OLR-) band pass filter (BPF) in 0.18 μm TSMC Complementary Metal Oxide Semiconductor (CMOS) with low insertion (IL) is presented in this manuscript. First, shape optimization and folding are used to guarantee compact size. Then, high performance of the proposed BPF is obtained by virtually increasing the height of the oxide between the OLR's traces and their ground plane. This virtual increase in the oxide height is realized by etching large slot areas below each of the OLRs. Consequently, the traces are characterized by wider width which in return exhibit lower attenuation constant and hence lower IL. The simulated and measured responses have a very good agreement. The fabricated BPF shows an IL of 3.5 dB at 59 GHz with a return loss of 15 dB and a fractional bandwidth of 16.5%. The fabricated chip has an area of 378 × 430 μm² including the measurements pads.

In order to improve the resolution of microwave biomedical imaging, a new method has been proposed in this pa-per, using a water-immersed wide band horn antenna at S-band. Considering the microwave penetration depth and the reflection at the interface between tissues and environment in deionized water, 2.45 GHz is selected as the central frequency of this antenna. Due to the high dielectric constant of water, the design of the impedance matching structure between the coaxial line and rectangular waveguide is most challenging. Therefore, the idea that using water as the medium of the coaxial impedance matching structure is proposed to deal with the problem of processing in our work. Simulated and experimental results show that this antenna has good impedance characteristics (S₁₁ < -10 dB from 2.1 GHz to 3.8 GHz), good reasonable losses (5.1 dB total for two antennas and coaxial line at 3 GHz), and high maximum gain (8.52 dBi at 2.45 GHz).

Due to static magnetic field, the conductivity of graphene becomes an anisotropic tensor, which complicates most modeling methodologies. A practical approach to the Wave Concept Iterative Process method (WCIP) modeling of magnetized graphene sheets as an anisotropic conductive surface from the microwave to terahertz frequencies is proposed. We first introduce a brief description of modeling magnetized graphene as an infinitesimally thin conductive sheet. Then, we present a novel manner for the implementation of the anisotropic boundary conditions using the wave concept in the WCIP method. This proposed method is benchmarked with numerical examples to demonstrate its applicability and accuracy. The proposed approach is used to compare the anisotropic model, isotropic model, and the metal for a strip waveguide. We show that the anisotropic model gives more efficient results.

Owing to the hardware cost and power consumption limitation, hybrid precoding has been recently considered as an alternative to the fully digital precoding in millimeter wave (mmWave) largescale multiple-input multiple-output (MIMO) systems. Although the number of radio frequency (RF) chains is reduced to a certain extent in the hybrid precoding structure, a great number of phase shifters are still needed. In this paper, we present a new hybrid precoding architecture based on switch network to decrease the power consumption of hybrid precoder by reducing the number of phase shifters greatly. The new hybrid precoding architecture consists of three parts, a digital precoder, an analog precoder, and a switch network, in which the switch network is used to offer a dynamic connection from phase shifters to antennas. Afterwards, a two-stage algorithm is proposed to determine each part of the hybrid precoding implementation. Specically, the product of the analog precoding matrix and digital precoding matrix is viewed as a whole matrix rstly, thereby the original problem is simplified into a two-variable problem which is relatively easy to be solved. Then, the decomposition of the analog precoding matrix and digital precoding matrix is considered in the second stage. Simulation results show that the presented implementation can not only provide a better trade-off between hardware complexity and system performance, but also achieve higher energy eciency with far fewer phase shifters than previous works.

A new miniaturized microstrip branch-line coupler with good harmonic suppression is proposed in this paper. The new structure has two significant advantages, which not only effectively reduces the occupied area to 19.1% of the conventional branch-line coupler at 0.90 GHz, but also has high 7th harmonic suppression performance. The measured results indicate that a fractional bandwidth of more than 15.6% has been achieved while the phase difference between S₂₁ and S₃₁ is within 90° ± 0.8°. The measured fractional bandwidths of |S₂₁| and |S₃₁| within 3 ± 0.3 dB are 16.1% and 16.7%, respectively. Furthermore, the measured insertion loss is comparable to that of a conventional branch-line coupler. The new coupler can be easily implemented by using the standard printed-circuit-board etching processes and is very useful for wireless communication systems.

This paper describes a printed wideband low profile omnidirectional dual-polarized antenna, which is a combination of vertical polarization (VP) and horizontal polarization (HP) elements. The VP element printed on a double-layered disk-shaped substrate is a modified monopole with loadings. The introduction of the material of the dielectric substrate can reduce the profile height in the polarized direction to 0.08λ_L (the wavelength at the lowest frequency). And loading metallic cylindrical block and shorting-posts in the dielectric substrate to improve the bandwidth are realized by using metal-vias. The HP element consists of a printed 8-element circular connected Vivaldi antenna array, and each element contains a director in the slot for the improvement of radiation pattern's out-of-roundness. Both the simulated and measured results indicate that operating bands of 2.2-4.52 GHz for VP and 2.4-3.8 GHz for HP. This proposed antenna has good isolation and omnidirectional patterns with the out-of-roundness less than 2.5 dB in the azimuth plane for both VP and HP, and it can be applied in mobile communication systems.

In this paper, a wideband ±45° dual-polarized antenna is proposedfor wireless communication. An annular ring patch with four arc-shaped slots is employed to generate a wide operating impedance bandwidth. By introducing four open stubs to the antenna element, the impedance bandwidth is enhanced. The antenna has a broad impedance bandwidth (VSWR<2) of 51.2% (1.63-2.75 GHz) and a high port-to-port isolation of 27 dB over the entire band of operation. In addition, a 1×4 antenna array is developed for the wireless communication. Experimental results illustrate that the antenna array features wide operational bandwidth, high port isolation and superior radiation performance.

Eddy current (EC) inspection is used extensively in non-destructive testing (NDT) to detect surface-breaking defects of engineering components. However, the sensitivity of conventional eddy current inspection has plateaued in recent years. The ability to detect submillimetre defects before it becomes critical would allow engineering components to remain in-service safely for longer. Typically, it is required that higher frequency EC is employed to achieve a suitable sensitivity for detection of such submillimetre defects. However, that would lead to significant electromagnetic noise affecting the sensitivity of the inspection. To overcome this issue, the electrical-resonance based eddy current method has been proposed, where the electrical enhanced resonance signal increases the contrast between signal and noise, thus improving the sensitivity of the defect detection. This work aims to investigate the electrical-resonance system via simulation technology using combination of fast numerical-based simulation and circuit approach. Leveraging on this model, the detection system can be optimized by performing parameters tuning. Investigation of both experiment and simulation develops a precise calibration model for submillimeter defects detection.

In this research paper, a Ridge Substrate Integrated Waveguide (RSIW) multiple band bandpass filter embedded with an octagonal shape Complementary Split Ring Resonator (CSRRs) is proposed. The electrically coupled octagonal shape CSRR is placed interdigitally in RSIW using transverse coupling technique to improve multiple passband bandwidths. The filter exhibits a highly selective multiple electric or magnetic or bianisotropic mode for different frequencies. The analysis for spurious band suppression has been done by direct method. The prototype configuration of quarter wavelength octagonal CSRR resonators introduces band suppression at all odd harmonics. The proposed structure of filter with dimension 1.36λ_g×0.52λ_g excluding feed port is fabricated. Full wave structure simulated results are compared with measurement ones. The measured passband frequencies and their calculated respective central frequency (f₀), fractional bandwidth (FBW) are in close agreement with the simulated result. The spurious higher order harmonics are observed as suppressed. The filter can be utilized to suppress interference from LAN, WLAN, GSM, WiMAX and variable stopband for ISM interference.

A novel triple-band ultrathin metamaterial absorber (MA) with polarization independence is designed, characterized and realized in this study. The designed absorber consists of three layers. The top metallic patch is patterned in an ultrathin dielectric substrate that is backed with a ground metallic plate. The numerical simulation results show that the presented metamaterial absorber exhibits three distinct absorption peaks of 99.95%, 99.28% and 96.36% under normal incidence at frequencies of 8.115, 11.4 and 15.12 GHz, respectively. Due to its fourfold symmetry, the absorbing properties are independent of the polarization of the incident radiation angle. Moreover, in the cases of TE and TM polarization modes, the proposed absorber displays an outstanding absorption response over a wide range of incident angles. The physical mechanism of the absorption performance is explained by investigating the surface current and field distributions at three distinct absorption peaks. Furthermore, the presented absorber is practically validated by the excellent agreement observed between the experimental and simulated results. The designed absorber has an ultrathin thickness of 1 mm, which is 0.027λ₀ with respect to the lowest peak absorption frequency, and can be useful for several potential applications, such as electromagnetic compatibility, stealth technology and super lenses.

A microstrip antenna with a pixel ground structure for single and multiband frequency reconfigurable applications is presented. The partial ground structure of the primary antenna is converted into pixel shapes which produce single and multiband frequency reconfigurable characteristics by the means of RF switches. The designed antenna operations are switchable over multiband, single frequency band and UWB spectrum with distinct configuration of RF switches. Three cases of RF switch configurations have been demonstrated with their simulated and measured results to verify the reconfigurable characteristics.

Old susceptibility data, measured in superconducting materials at low-frequency, are shown to be accounted for consistently within the framework of a recently published [1] analysis of the skin effect. Their main merit is to emphasize the significance of the skin-depth measurements, performed just beneath the critical temperature T_c, in order to disprove an assumption, which thwarted any understanding of the skin-depth data, achieved so far by conventional high-frequency methods, so that those data might, from now on, give access to the temperature dependence of the concentration of superconducting electrons.

Recent reports on metasurfaces have focused on beam-deflector, a canonical optical element that can be used to compose other functionalities. Most reported designs, however, are limited to small deflection angles; large-angle (≥50 degrees deflection) transmission-mode beam steering designs show poor efficiency. Furthermore, rapid efficiency degradation is also observed for small deviations in the angle of incidence. This paper presents a numerical study of beam-deflectors based on extended unitcell metagratings (unit-cells containing multiple differently sized nanoantenna members). In comparison to previous reports, the designs achieve significant efficiency improvements, wider acceptance angles and better polarization filtering. The versatility of the design technique is demonstrated by designing polarizing beam deflectors polarization insensitive beam deflectors and prismatic beam deflectors.

Global Navigation Satellite System (GNSS) reflectometry is a promising technology used to estimate soil moisture, sea surface height, ice properties, etc. Interference signal technique is an important method to estimate these geophysical parameters. The effect of this method is closely related to the terrain and the receiving antenna placement. This study aims to investigate the effects of terrain and antenna placement on height measurement through simulation and field experiments. In this paper, we first simulated the interference signal in different types of terrain by parabolic equation method and analyzed the influence of terrain on the height measurement. Then we conducted three typical field experiments and processed experimental data. The simulated and experimental results indicate that the interference signal is affected by the terrain and the receiving antenna placement. Height measurement result is correct by both horizontal-looking and zenith-looking antenna when the ground is flat. However when the ground is not flat, the soil block near the receiving antenna leads to estimation errors. A more accurate estimation is obtained by using zenith-looking antenna to suppress the influence from the near terrain than horizontal-looking antenna. When a slope is near the receiving antenna, the signal with a high elevation may achieve an obvious interference effect if high elevation minus slope is equivalent to a low elevation. In this situation, the measurement height is the distance between the antenna and slope surface.

An electroquasistatic (EQS) model of capacitive hyperthermia for treating lung tumors is proposed, based on which the finite element method is applied to compute the electrical potential in a human thorax model. The temperature distribution in the thorax model, which is surrounded by a bolus maintained at a constant temperature, is computed by numerically solving a bioheat equation, which includes metabolic heat generated in the tissues, heat convection mechanism in tissues and bolus, as well as the heat delivered by the microwave field computed with the EQS model and finite element method. Temperature-dependent blood perfusion rates of blood and muscle, respectively, are adopted to account for the physiological reaction of tissues to temperature variation. By simulations, it is observed that adjusting the dielectric properties of adipose tissue via injection, the time evolution of temperature distribution can be controlled to some extent, providing more flexibility to customize a hyperthermia treatment plan for specific patient.

This paper proposes an unequal power divider with different terminated impedances and different electrical lengths for four uniform transmission lines. The proposed power divider consists of four transmission lines with different electrical lengths and an isolation resistor. Under different port impedances, the splitting ratio of the proposed divider can be adjusted to desired values by varying the electrical lengths of the divider transmission lines with uniform impedances. To verify the feasibility of the proposed divider, two circuits were designed with dividing ratios of 2:1 and 4:1 at an operating frequency of 2 GHz. The circuits used a uniform impedance of 40 Ω at terminated impedances of 50, 70, and 60 Ω. The performance showed excellent agreement between the simulated and experimental results.

The role of the source geometry is investigated within the realm of inverse source problems. In order to examine the properties of the far zone radiation operator of some 2D curved sources its Singular Value Decomposition (SVD) is studied, either analytically, when possible, or numerically. This allows to evaluate the number of independent pieces of information, i.e. the number of degrees of freedom (NDF), of the source and to point out the set of far zone fields corresponding to stable solutions of the inverse problem. In particular, upper bounds for the NDF are obtained by exploiting Fourier series representations of the singular functions. Both curved (i.e. circumference and arc of circumference) and rectilinear geometries are considered, pointing out the role of limited angular observation domains. Moreover, in order to obtain some clues about the resolution achievable in the inverse source problem, a point-spread function analysis is performed. The latter reveals a spatially variant resolution for limited angular observation domains. The practical relevance ofthese results is highlighted with numerical examples of array diagnostics.

In this paper, we obtain an asymptotic solution for the problem of electromagnetic diffraction at a thick curved dielectric layer with a nonuniform dielectric permittivity. We show that, in the case of thick layers, the main asymptotic approximation already comprises the curvature correction, verify the results by comparison with a solution obtained with the integral equation method, and offer to approximate the piecewise constant dielectric permittivity of a stratified layer with a continuous function.

A broadband dual-polarized dipole antenna with overlapped dipole arms is proposed in this paper. To obtain a compact radiator size, the arm-overlapped dipole antenna is constituted by splitting and overlapping the edges of a cross loop dipole. Then four open pins are soldered to the dipole to excite a third resonance at high frequency band. Measured results show that the proposed antenna with a small radiator size of 49×49 mm² has an impedance bandwidth of 49.5% (1.7-2.82 GHz) for VSWR<1.5, port isolation >28 dB and half-power beamwidth (HPBW) of 65º±5º. A 4-element antenna array with 8º±2º electrical down tilt is shown to further validate the performance of the antenna.