A rectangular dielectric resonator antenna (DRA) with a square spiral microstrip feedline is investigated in this paper. The design utilizes a feeding structure to excite two resonant modes (TE_δ11 and TE_1δ1 modes) of the rectangular DRA that are spatially orthogonal in polarization and in phase. The antenna with the proposed feeding structure has provided a measured circular polarization(CP) over a bandwidth of ~15.5% in conjunction with an impedance-matching bandwidth of ~31.25% at the same frequency range. The gain of the dielectric resonator antenna varies between 6.8 and 7.2 dBi across the bandwidth (7.5~8.75 GHz). Reasonable agreement between the simulated and measured results is obtained.

A frequency dependent model of sheet resistance of transparent conductive mesh coatings is proposed based on transmission line theory and vilified by experiments. And the effect on shielding effectiveness of frequency dependent sheet resistance is analyzed. Simulation results of shielding effectiveness are compared with the experimental data of a mesh-coated window sample with equivalent parameters fabricated and measured by Exotic Electro-Optics. The agreement between experiment and simulated proves the validity of the proposed sheet resistance model. So it can be therefore concluded that the frequency dependent model can be used to reasonably evaluate sheet resistance and shielding effectiveness of transparent conductive mesh coated windows.

Adaptive beamforming methods degrade in the presence of model mismatch. In this paper, we develop a modified interference covariance matrix reconstruction based beamformer that is robust against large array calibration errors. The calibration errors can come from the element position errors, and/or amplitude and phase errors, etc. The proposed method is based on the fact that the sample covariance matrix can approximate the interference covariance matrix properly when the desired signal is small, and a reconstructed covariance matrix based on the Capon spectral will be better than the sample covariance matrix when the desired signal is large. A weighted summation of two covariance matrices in references is used to reconstruct the interference covariance matrix. Moreover, a computationally efficient convex optimization-based algorithm is used to estimate the mismatch of the steering vector associated with the desired signal. Several simulation cases are applied to show the superiority of the proposed method over other robust adaptive beamformers.

We investigate the design of Concentric Circular Antenna Arrays (CCAAs) with λ/2 uniform inter-element spacing, non-uniform radial separation, and non-uniform excitation across different rings, from the perspective of Multi-objective Optimization (MO). Unlike the existing single-objective design approaches that try to minimize a weighted sum of the design objectives like Maximum Side Lobe Level (MSLL) and principal lobe Beam-Width (BW), we treat these two objectives individually and use Multiobjective Evolutionary Algorithm based on Decomposition (MOEA/D) with Differential Evolution (DE), called MOEA/D-DE, to achieve the best tradeoff between the two objectives. Unlike the single-objective approaches, the MO approach provides greater flexibility in the design by yielding a set of equivalent final (non-dominated) solutions, from which the user can choose one that attains a suitable trade-off margin as per requirements. We illustrate that the best compromise solution attained by MOEA/D-DE can comfortably outperform state-of-the-art variants of single-objective algorithms like Particle Swarm Optimization (PSO) and Differential Evolution. In addition, we compared the results obtained by MOEA/D-DE with those obtained by one of the most widely used MO algorithm called NSGA-2 and a multi-objective DE variant, on the basis of the R-indicator, hypervolume indicator, and quality of the best trade-off solutions obtained. Our simulation results clearly indicate the superiority of the design based on MOEA/D-DE.

This paper presents a stable grounding technique for the inner conductor of a coaxial resonator in vacuum and high-power condition applications, where the inner and outer conductors of the coaxial resonator are connected by a flange plate. When this novel technique is applied, the stable and unified microwave grounding ability is increased by making the stress on the contact surface uniform, the reliability of space products is improved by reducing the deformation of the rod-end at a transverse vibration load of 10 g by 75%, and the unstable tiny cracks of the high-power component are fully eliminated.

This letter presents the design of a novel wideband omnidirectional antenna with the usable bandwidth enhanced. The antenna is designed for wireless applications and proposed to operate within WLAN (2.4 GHz-2.484 GHz) and WiMAX (2.3 GHz, 2.5 GHz and 3.5 GHz) frequency bands. The bandwidth is enhanced through the use of balun, while the radiation patterns remain stable. This antenna has a much wider VSWR band (47.5% for VSWR < 2) with high radiation pattern stability compared with printed dipole antennas. Details of design, simulated and experimental results of this omnidirectional antenna are presented and discussed. The measured results confirm the validity of this design which meet the requirement of wireless applications.

Properties of wave transmission in a photonic quantum well (PQW) structure containing superconducting materials are theoretically investigated. We consider two possible PQW structures, (AB)^P(CD)^Q(AB)^P-asymmetric and (AB)^P(CD)^Q(BA)^P-symmetric, where the host photonic crystal (PC) (AB)^P is made of dielectrics, A = SrTiO₃, B = Al₂O₃, and the PQW (CD)^Q contains C = A and superconducting layer D = YBa₂Cu₃O_7-x, a typical high-temperature superconducting thin film. Multiple transmission peaks can be seen within the photonic band gap (PBG) of (AB)^P and the number of peaks is directly determined by the stack number of PQW, i.e., it equals Q-1. Additionally, the results show that symmetric PQW structure is preferable to the design of a multichannel transmission filter. The effect of stack number of photonic barrier is also illustrated. Such a filter operating at terahertz with feature of multiple channels is of technical use in superconducting optoelectronic applications.

We perform the long time monitoring of nanoparticle-cell membrane interaction with high spatial and temporal resolution. The 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl) phenyl)amino)phenyl) fumaronitrile (TPE-TPA-FN) is doped in organically modified silica (ORMOSIL) to be a biocompatible nanoprobe, which displays an aggregation-induced emission (AIE) effect. Photobleaching resistance of this synthesized nanoparticle is tested and compared with its similar counterpart, which proves its superiority and capability of long term fluorescence emission. We utilize the objective-based total internal reflection microscopy combined with the living cell incubation platform to investigate the cell uptake process of this nanoparticle in real time.

To obtain Electromagnetic Compatibility (EMC), we would like to study the worst-case electromagnetic eld-induced voltages at the ends of Printed Circuit Board (PCB) traces. With increasing frequencies, modelling these traces as electrically short no longer suffices. Accurate long line models exist, but are too complicated to easily induce the worst case. Therefore, we need a simple analytical model. In this article, we predict the terminal voltages of an electrically long, two-wire transmission line with characteristic loads in vacuum, excited by a linearly polarised plane wave. The model consists of a short line model (one Taylor cell) with an intuitive correction factor for long line effects: the modified Taylor cell. We then adapt the model to the case of a PCB trace above a ground plane, illuminated by a grazing, vertically polarised wave. For this case, we prove that end-fire illumination constitutes the worst case. We derive the worst-case envelope and try to falsify it by measurement in a Gigahertz Transverse Electromagnetic (GTEM) cell.

We describe a four-layered model for near infrared light propagation in a human head based on the Monte Carlo method. With the use of three-dimensional voxel-based media discretization, photon migration in the brain is analyzed by both the time-of-flight measurement and the spatial sensitivity profile. In the measurement of brain activity, the selection of light wavelength and the distance between the source and the detector have a great influence on the detected signal. In this study, we compare the detected signals from the detectors with different source-detector spacing at wavelengths of 690 nm, 800 nm and 1300 nm, and find that in our model, the wavelength of 1300 nm is more appropriate for the measurement of brain activity because the signals at 1300 nm get better detection sensitivity and spatial resolution. Source-detector spacing is also optimized.

This paper deals with the measurement of the magnetic flux generated by the armature of electromagnetic rail launchers linked with external pick-up loops. In particular we discuss possible methods to experimentally evaluate measurement uncertainty when the magnetic flux is obtained by numerical voltage integration. These methods aim at an approximate identification of the correlation among voltage samples introduced by the analog-to-digital converter, only based on the available measurements without requiring additional tests and instruments. An estimate of this correlation allows to better evaluate the overall measurement uncertainty, thus providing the applicability limits of the proposed inductive technique and contributing to a better understanding of the current and force distribution in the armature.

A simple and novel method for increasing the gain at low elevation angle and widening the beamwidth of quadrifilar helix antenna (QHA) is presented. By adding cross dipoles as a reflector, the right hand circular polarization (RHCP) gain at 5° elevation angle (theta=85°) increases by about 1.4 dB. Parametric studies are performed to explore the performance improvements. An antenna for CNSS (Compass Navigation Satellite System, 2.492 GHz) application is realized based on the studies. The RHCP gain at 5° elevation angle is about 0.6 dB, and 3dB beamwidth is greater than 220°. 10 dB impedance bandwidth is more than 24%, and 3dB axial ratio bandwidth is more than 32%. Measured results are presented to validate the proposed method.

This paper discusses an improved in-situ immunity measurement test bench of a microcontroller -PIC18F458 to conducted continuous wave interference (CWI). The updated measurement algorithm gives more accurate measurement result. Compared with normal failure criterion, the DC shift failure criterion is adopted because it gives better description of the immunity behavior of the microcontroller. Finally, the susceptibility results are explained in detail.

In this paper we present two simulation techniques for modeling periodic structures with three-dimensional elements in general. The first of these is based on the Method of Moments (MoM) and is suitable for thin-wire structures, which could be either PEC or plasmonic, e.g., nanowires at optical wavelengths. The second is a Finite Difference Time Domain (FDTD)-based approach, which is well suited for handling arbitrary, inhomogeneous, three-dimensional periodic structures. Neither of the two approaches make use of the traditional Periodic Boundary Conditions (PBCs), and are free from the difficulties encountered in the application of the PBC, as for instance slowness in convergence (MoM) and instabilities (FDTD).

A novel dual-polarized dipole antenna with compact size is presented for wireless communication applications. The proposed antenna is composed of a dual-polarized cross dipole, a small-sized tapered reflector, a square patch director, and an octagon ring as a parasitic element. Low VSWRs (<1.5) are achieved in aimed operating band of 2500-2690 MHz at both ports, which can cover the LTE2600 frequency band. High port isolation (>38 dB) and symmetric broadside radiation patterns are also achieved. Two dual-polarized reference antennas are also developed. Contrast results show that the proposed antenna can obtain improved radiation patterns compared with the reference antennas. Moreover, the proposed antenna is very compact in size (0.52λ₀×0.52λ₀×0.32λ₀, λ₀ refers to the center frequency of operating band), which achieves about 20% size reduction than Ref 2. Experimental results are also carried out to verify the simulation analysis.

A novel slot-line filter with stop-band up to 30 GHz is proposed in this paper, and the theoretical analysis is illustrated in detail. This filter is designed on a Rogers RT/duroid 5870 substrate. The rectangular micro-strips can generate transmission zero to give a great suppression for the spurious response around 5f₀ while the L slot lines can create transmission zeros to suppress the spurious response around 7f₀, 9f₀ and 11f₀. f₀ is 2.43 GHz in this paper and represents the center frequency of the main passband. The compact size of this novel filter is 23.7 mm * 14.725 mm (0.152λ * 0.103λ (λ is the working wavelength of this filter)). Besides, the external quality factor of this filter can be as high as about 29.6. To demonstrate the transmission function, the compact filter has been fabricated and the measured results show the feasibility of this structure.

In this manuscript, a novel design of ultra-wideband (UWB) monopole antenna with dual frequency band-stop performance is proposed. The proposed antenna consists of an ordinary square radiating patch with a pair of rotated T-shaped slits, and a modified ground plane with an inverted Ω-shaped and a pair of rectangular-ring slots. In the presented structure, by cutting a pair of rectangular-ring slots in the ground plane, additional resonances are excited and hence much wider impedance bandwidth can be produced, especially at the higher band that the antenna provides a wide usable fractional bandwidth of more than 140% (2.8-17.5 GHz). In order to generate single band-notched characteristic, we cut a pair of rotated T-shaped slits in the square radiating patch. Finally, by inserting an inverted Ω-shaped slot in the ground plane, a dual band-notched function is achieved. The measured results reveal that the presented dual band-notch monopole antenna offers a very wide bandwidth with two notched bands, covering all the 5.2/5.8 GHz WLAN, 3.5/5.5 GHz WiMAX and 4 GHz C bands. The designed antenna has a small size of 12×18 mm². Good return loss, antenna gain and radiation pattern characteristics are obtained in the frequency band of interest. Simulated and measured results are presented to validate the usefulness of the proposed antenna structure for UWB applications.

In this paper, an electronically reconfigurable beam steering antenna using embedded RF PIN switches based parasitic array (ERPPA) is proposed for modern wireless communication systems that operate at 5.8 GHz frequency. In the proposed antenna, a single driven element is fed by a coaxial probe, while each of the two parasitic elements is integrated with an RF PIN switches that embedded inside the substrate. In the conventional reconfigurable antennas, the RF PIN switches are mounted on narrow slots created on the top or bottom layer of the radiator/parasitic elements, which could lead to the dimensional changes of the antenna and degrade the performance in terms of beam steering and return loss. However, this research proposes an exclusive solution where the RF PIN diodes at parasitic elements are embedded inside the substrate thus no additional slots have to be created to mount the SMCs on the antenna. In this regard, the proposed antenna is highly competent to eliminate the intermodulation effect generated by the RF PIN diodes and the other passive elements associated with the PIN diodes. In this research, extensive investigations revealed that the parasitic element dimension and the selection of RF PIN switches significantly influence the antenna's beam steering capability. Adopting certain ON/OFF condition of the embedded RF switches, three beam-steering angles of -30°, 0° and +30° are achieved in the xz-plane, with measured peak gains at θ = -30°, 0° and +30° are 6.5 dBi, 6.5 dBi and 4.9 dBi, respectively. The fabricated antenna with Taconic substrate provides a good agreement with the simulation result. Furthermore, the performance of ERPPA is further tested by outdoor measurement using a wireless bridging system to verify the functionality of the designed antenna at the angles of -45°, -30°, -15°, 0°, 15°, 30° and 45°. The analysis with the switched diversity combining scheme has demonstrated that a maximum diversity gain approximately of 12 dBi is offered by the proposed antenna. With a compact dimension of 32 mm by 76 mm, the proposed antenna is a potential candidate in point-to-point wireless applications such as WIFI application.

The asymmetric transmission of the linearly polarized waves at normal incidence through the lossy anisotropic chiral structure is demonstrated. The proposed chiral metamaterial structure is composed of bi-layered discontinuous cross-wire-strips, and it is utilized in order to realize polarization rotation. Firstly, the theoretical relations between the incident polarization and the polarization rotation are derived using transmission matrices. Secondly, a strong and dynamically asymmetric transmission of linearly polarized electromagnetic wave through the chiral metamaterial has been demonstrated for microwave region, both by simulation and experimentally. The experiment results are in good agreement with the simulation ones. It can be seen from the results that the proposed chiral metamaterial structure can be used to design novel polarization control devices for several frequency regions.

A reconfigurable half-mode substrate integrated waveguide (HMSIW) bandpass filter (BPF) loaded by complementary split-ring resonator (CSRR) is investigated. The proposed HMSIW-CSRR structure allows the implementation of a forward-wave passband propagating below the characteristic cutoff frequency of the waveguide. By changing the effective capacitance to ground of the CSRR, frequency tuning of the resonator is observed without other external circuit. The proposed filter exhibits improved selectivity due to the employment of the pseudo-S defected structure to generate transmission zero at the low stopband. To verify the presented design method, the predicted compact reconfigurable filter, tuned between 3.6 GHz and 4.5 GHz with insertion loss less than 3.6 dB and return loss better than 17 dB, is fabricated based on the standard printed circuit board process. The measured results are in good agreement with the simulation.