To suppress electromagnetic interference at 5.5-GHz WLAN (5.15-5.825 GHz) band operation, a novel ultra-wideband (UWB) design of a slotted twin-patch monopole antenna with a band-rejection characteristic is presented. The proposed antenna with a simple structure has a large impedance bandwidth, defined by 10-dB return loss, covering the range from 2.95 to 10.85 GHz, and a tunable cutoff band from 5.18 to 6 GHz for band-operation suppression. Measured monopole-like radiation pattern and in-band average gain of about 2.3 dBi have also been obtained, simultaneously, with good agreement to the simulated results.

A time domain hybrid method is presented for efficiently solving the electromagnetic coupling problems of transmission lines in cavity. The proposed method is based on the finite-difference time-domain (FDTD) method and transmission line (TL) equations (FDTD-TL), which can achieve a strong synergism on the computations of field and circuit. The FDTD method with an auto mesh generation technique is employed to obtain the electric fields of transmission lines excited by an incident wave from the outside of the cavity. The electric fields are introduced into the TL equations as additional voltage sources at each time step of FDTD method. The current and voltage responses of terminal loads can be obtained by the TL equations. Two examples are presented to demonstrate the correctness of this method. The high efficiency of this hybrid method is verified by comparing the computation time with the traditional method.

This paper proposes a burst model of chaotic noise signals with randomly stepped carrier frequencies for velocity estimation and high-resolution range imaging of high-speed moving targets. The random stepping of carrier frequencies is controlled by a combination chaotic map (CCM), which is generated by embedding a Logistic map into a Bernoulli map. The baseband noise signal adopts the CCM based frequency-modulation (CCM-FM) signal, which has good randomness and a thumbtack ambiguity function as well. The velocity estimation includes a coarse search where the coarse search is conducted with a fixed step to makes the velocity deviation less than the velocity resolution, while the precise search adopts the Golden Section Search (GSS) algorithm to get an accurate estimation of velocity. What should be emphasized is that the velocity estimation process can be completed with just a burst of subpulses. Then the spectra are coherently synthesized to obtain ultra-wide bandwidth and high-resolution range imaging. Finally, numerical simulations demonstrate a good performance of the proposed signal model and the processing algorithm.

In this article, the design of an electromagnetically-coupled millimeter-wave elliptical patch array antenna prepared to work in the 56-65 GHz (14.8%) frequency band is presented. The introduced antenna array is designed for low-loss, high-gain and low cross-polarization levels. The proposed antenna exhibits a measured gain of 8 dBi and good linear polarization across the desired frequency range. It has a good side lobe suppression better than 17 dB in both E- and H-planes. Measured and simulated results confirm that this antenna is a good candidate for short-range wireless communication applications at millimeter-wave frequencies.

Electromagnetic field transformations are important for electromagnetic simulations and for measurements. Especially for field measurements, the influence of the measurement probe must be considered, and this can be achieved by working with weighted field transformations. This paper is a review paper on weighted field transformations, where new information on algorithmic properties and new results are also included. Starting from the spatial domain weighted radiation integral involving free space Green's functions, properties such as uniqueness and the meaning of the weighting function are discussed. Several spectral domain formulations of the weighted field transformation integrals are reviewed. The focus of the paper is on hierarchical multilevel representations of irregular field transformations with propagating plane waves on the Ewald sphere. The resulting Fast Irregular Antenna Field Transformation Algorithm (FIAFTA) is a versatile and efficient transformation technique for arbitrary antenna and scattering fields. The fields can be sampled at arbitrary irregular locations and with arbitrary measurement probes without compromising the accuracy and the efficiency of the algorithm. FIAFTA supports different equivalent sources representations of the radiation or scattering object: 1) equivalent surface current densities discretized on triangular meshes, 2) plane wave representations, 3) spherical harmonics representations. The current densities provide for excellent spatial localization and deliver most diagnostics information about the test object. A priori information about the test object can easily be incorporated, too. Using plane wave and spherical harmonics representations, the spatial localization is not as good as with spatial current densities, but still much better than in the case of conventional modal expansions. Both far-field based expansions lead to faster transformations than the equivalent currents and in particular the orthogonal spherical harmonics expansion is a very attractive and robust choice. All three expansions are well-suited for efficient echo suppression by spatial filtering. Various new field transformation and new computational performance results are shown in order to illustrate some capabilities of the algorithm.

In this paper, a novel printed microstrip-fed monopole ultra-wideband (UWB) antenna with triple-notched bands using triple-mode stepped impedance resonator (SIR) is presented. The proposed triple-mode SIR is found to have the advantages of introducing triple-notched bands and providing higher degree of freedom to adjust the resonant frequencies. By coupling the triple-mode SIR beside the microstrip feedline, band-rejected filtering properties around the 5.2 GHz WLAN band, the 6.8 GHz RFID band, and the X-band satellite communication band, are generated. To validate the design concept, a novel compact UWB antenna with three notched bands is designed and measured. Results indicate that the proposed compact antenna not only retains triple band-rejections capability but also owns omni directional radiation patterns across nearly whole operating bandwidth for UWB communications.

In this paper a dual-band bandpass filter using loaded stub in the ring resonator and etched nested C-shape defected ground structure (DGS) on ground plane is reported. The operating frequencies of the bandpass filter are selected for applications in Bluetooth (2.4 GHz-2.484 GHz) and WLAN (5.15 GHz-5.35 GHz) systems. Due to its applications in WLAN and Bluetooth system the filter will be subjected to high EM radiation from the antenna and nearby sources. Therefore, susceptibility study of such filter is very important. The susceptibility study of the filter has been carried out by subjecting the structure to an interference source. Experimental results are presented and analyzed.

A simple slot coupled dual-band circularly polarized (CP) rectangular dielectric resonator antenna (DRA) is presented. The TE₁₁₁ and TE₁₁₃ modes of the rectangular DRA are excited by a modified annular slot. Working principle of the proposed antenna is explained in this paper. Design guideline of the proposed antenna is also devised based on the parameter study. The simple feeding and radiating structures of the proposed antenna make it easy to be designed and fabricated. A prototype antenna was designed, fabricated and measured. The simulated and measured results confirm the dual-band CP performance of the proposed antenna.

We study the magneto-permittivity effect in a magnetized plasma with appropriately designed parameters. We show that at frequency near the plasma frequency, magneto-optical activity plays an important role to manipulate and control the wave propagations in the magnetized plasma. Such a unique feature can be utilized to establish sensitive magnetic field switching mechanism, which is confirmed by detailed numerical investigations. Switching by magnetic field based on magnetized plasma is flexible and compatible with other optical system; moreover it is applicable to any frequency by tuning the plasma density. For these reason, our work shows the possibility for developing a new family of high frequency and ultrasensitive switching applications.

For the first time, the higher-ordered modes of a stepped-impedance slotline resonator are closely combined for designing the broadband in-phase andout-of-phase power dividers. It was found that the output phases of the two modes can be easily reversed at the same time by changing the direction of their feeding currents. For this configuration, interestingly, a multifunctional power divider which is reconfigurable to produce either in-phase or out-of-phase signals can be easily designed from its passive counterparts by incorporating multiple RF diodes into the output feedlines, leading to significant cost saving and high compactness. The design procedure and equations of the power-dividing structures are discussed.

A novel direction of arrival (DOA) and polarization estimation method with sparse conical conformal array consisting of concentred loop and dipole (CLD) pairs along the z-axis direction is proposed in this paper. In the algorithm, the DOA and polarization information of incident signals are decoupled through transformation to array steering vectors. According to the array manifold vector relationship between electric dipoles and magnetic loops, the signal polarization parameters are given. The phase differences between reference element and elements on upper circular ring are acquired from the steering vectors of upper circular ring, it can be used to give rough but unambiguous estimates of DOA. The phase differences are also used as coarse references to disambiguate the cyclic phase ambiguities in phase differences between two array elements on lower circular ring. Without spectral peak searching and parameter matching, this method has the advantage of small amount of calculation. Finally, simulation results verify the effectiveness of the algorithm.

We investigate the electromagnetic wave propagation across a finite inhomogeneous and anisotropic cylindrical metamaterial composite containing both positive and negative effective refractive index parts with linear spatial gradient. Exact analytical solutions for the electric and magnetic field distributions are obtained for a linear variation of effective refractive index across the structure. The model allows for general temporal dispersion and uniform losses within the composite.

The matrix method for the calculation of antenna far-field using irregularly distributed near-field measurement data is presented. The matrix method is based on the determination of the plane wave expansion (PWE) coefficients from the irregular near-field samples using a matrix form that connects the radiated field with the corresponding plane wave spectrum. The plane wave spectrum is used to determine the far-field of the antenna under test (AUT). The matrix method has been implemented, and its potentialities are presented. The validations using analytical radiating model (dipoles array) and experimental measurement (X band standard gain horn antenna) results have demonstrated the efficiency and stability of the proposed method.

A microstrip antenna design is introduced in which aperture coupled rectangular microstrip patch is coupled electromagnetically with a parasitic gridded rectangular patch placed above. The gridded patch consists of nine identical rectangular parts separated by a distance which is much smaller than a free space wavelength for a central frequency. The antenna is designed to operate in the 60 GHz band and is fabricated on a conventional PTFE (polytetrafluoroethylene) thin substrate. Different published arrangements for parasitic patches are studied. For the same substrate and central frequency the proposed antenna has improved return loss bandwidth and gain bandwidth for approximately the same maximum gain. Measurement results are in good agreement with simulation. Measured 10 dB return loss bandwidth is from 54 GHz up to 67 GHz. It fully covers the unlicensed band around 60 GHz. The measured antenna realized gain at 60 GHz is close to 8 dB, while the simulated antenna radiation efficiency is 85%. A simple beam shifting method is possible for this antenna structure by connecting adjacent outside parts in the gridded patch. The designed antenna is suitable for a high speed wireless communication system in particular for a user terminal in a fifth generation (5G) cellular network.

This paper presents a novel approach for solving the frequency responses of a powerline network, which is a two-parallel-conductor system with multiple junctions and branches. By correcting the reflection coefficient and transmission coefficient of each junction, a complex network can be decomposed into several, single-junction, units. Based on the Baum-Liu-Tesche (BLT) equation, we preliminarily propose the calculation method of frequency responses for single-junction network. In accordance with the direction of power transfer, we calculate the frequency responses of loads connected to each junction sequentially, from the perspective of the network structure. This approach greatly simplifies the computational complexity of the network frequency responses. To verify the proposed algorithm, networks with various numbers of junctions and branches are investigated, and the results are compared with a commercial electromagnetic simulator based on the topology. The analytical results agree well with the simulated ones.

Pneumothorax is the medical condition caused by the air concentration inside the pleural cavity, the space between the lung and the chest wall. Apart from traditional diagnostic methods, it can be detected by using microwave sensors that capture variations in reflected electromagnetic field (EMF). Sex and obesity, related to the internal composition of the biological tissues, can influence the reflected EMF and therefore the sensor diagnostic ability. This paper investigates the effect on the performance of a proposed on-body dual-patch antenna sensor for pneumothorax diagnosis, due to inter-subject variability in underlying tissue structure. The sensor operates at frequency range of 1-4 GHz. The challenge of the paper is to propose frequency bands for robust and safe sensor operation. S₁₂ parameter alternation versus frequency is assessed for healthy and pathological cases. Implemented thorax numerical models include modified (i) closed rectangular multilayered and (ii) MRI-based anatomical ones. In rectangular models, thickness and configuration of muscle, fat and bone tissues are varied, according to literature. Additionally, sex-related anatomical differences are taken into account in MRI-based models. All scenarios are solved using Finite Difference Time Domain method. Results revealed that the proposed frequency bands lie within 1-2.7 and 2.9-3.5 GHz, for muscle, 1.4-3.5 GHz for fat and 1-2.2 and 2.8-3.5 GHz, for bone variations. Numerical evaluations for accurate anatomical models verify the findings.

A new printed helical antenna (PHA) for a circularly polarized (CP) titled beam is proposed. With the introduction of a multiple sections technique into the PHA's helical arm, the antenna radiates a CP titled beam. To feed the antenna, a matching network composed of a 50 Ω microstrip transmission line and two symmetrical λ₀/8 open stubs is designed. The simulated and measured results show that the PHA radiates a CP tilted beam with a maximum radiation direction of (θ_max, φ_max) = (32°, 135°) at f₀ = 2.11 GHz. The measured bandwidth with a reflection coefficient lower than −10 dB is 11.8% (1.99-2.24 GHz), and the experimental results for the radiation pattern, gain, and axial ratio (AR) are also presented.

This paper describes a novel technique which has the potential to make a significant impact on the mapping of the human brain. This technique has been designed for 3D full-wave electromagnetic simulation of waves at very low frequencies and has been applied to the problem of modeling of brain waves which can be modeled as electromagnetic waves lying in the frequency range of 0.1-100 Hz. The use of this technique to model the brain waves inside the head enables one to solve the problem on a regular PC within 24 hrs, and requires just 1 GB of memory, as opposed to a few years of run time and nearly 200 Terabyte (200,000 GB) needed by the conventional FDTD (Finite Difference Time Domain) methods. The proposed technique is based on scaling the material parameters inside the head and solving the problem at a higher frequency (few tens of MHz) and then obtaining the actual fields at the frequency of interest (0.1-100 Hz) by using the fields computed at the higher frequency. The technique has been validated analytically by using the Mie Series solution for a homogeneous sphere, as well as numerically for a sphere, a finite lossy dielectric slab and the human head using the conventional Finite Difference Time Domain (FDTD) Method. The presented technique is universal and can be used to obtain full-wave solution to low-frequency problems in electromagnetics by using any numerical technique.

This paper presents a miniaturized tunable bandpass filter, consisting of two coaxial dielectric resonators and a pair of parallel-coupled lines. A coaxial dielectric resonators and a microstrip line form a new step-impedance resonator (SIR), which is different from a conventional SIR. Varactor diodes are connected to SIRs to tune the center frequency. The gap between parallel-coupled lines controls the inter-stage coupling coefficient. Lumped inductors used for coupling to I/O ports can reduce design complexity. The variations of coupling coefficient and external quality factor with tuning frequency are analyzed using HFSS software. A appropriate coupling coefficient which satisfies with constant fractional bandwidth within the tuning range is available. A tunable filter has been made of dielectric ceramics with dielectric constant of 38, fabricated on dielectric substrate and measured using Networks analyzer. Center frequencies vary from 0.43 GHz to 0.78 GHz, 3 dB fractional bandwidth from 6.4% to 6.8% when bias voltages are applied from 0 V to 10 V. The measured results validate the approach and agree with the simulation.

This paper gives a comprehensive study on the modeling and design challenges of Through Silicon Vias (TSVs) in high speed three dimensional (3D) system integration. To investigate the propagation characteristics incurred by operations within the ultra-broad band frequency range, we propose an equivalent circuit model which accounts for rough sidewall effect and high frequency effect. A closed-form expression for TSV metal oxide semiconductor (MOS) capacitance in both depletion and accumulation regions is proposed. The coupling of TSV arrays and near and far field effect on crosstalk analysis are performed using 3D EM field solver. Based on the TSV circuit model, we optimize the TSVs' architecture and manufacturing process parameters and develop effective design guidelines for TSVs which could be used to resolve the signal integrity issues arising at high frequency data transmission in 3D ICs.