Brain stroke is a serious disease and one of the major causes of death. Stroke detection based on the frequently studied microwave imaging method is computation-intensive and not always reliable. This paper presents a stroke-detection scheme based on subspace classification technique. Specifically, the stroke is detected and located using the intersection of the positive antenna lines, i.e. connecting the transmitter and receiver. The numerical results show that the proposed method can detect and locate blood clots efficiently.

This paper presents a short-range imaging algorithm for multiple-input-multiple-output (MIMO) array. One of the steps in a previous method utilizes 2-D STOLT interpolation to transform 3-D data into 2-D data, which is not strict in the view of mathematical derivation and lack of physical meaning. The convolution operation which is analyzed by physical process of angular spectrum propagation is used to explain multi-static configuration and reduce the 3-D data into 2-D ones. This paper gives the physical phenomena of the whole process of imaging. We also explain the different physical meanings of FFT between transmitters and receivers. Numerical simulations show the consequence of STOLT interpolation in the previous algorithm and demonstrate the performance of the proposed algorithm.

Nowadays it is important to create military and civilian vehicles which would be invisible to radar (or homing precision weapons). Such a task requires using high amount of radio-absorbing materials and high cost of finished samples of re-engineering. So it is very useful to have some methods for mathematical modeling of electromagnetic waves scattering on the object in order to take into account various techniques to reduce the object visibility at the stage of design. After the mathematical modeling for each case (specified wavelength, polarization, background surface, etc.), we obtain the angular RCS dependence. We obtain such dependencies for two different models. Based on the comparison of these two dependencies for different objects, it is very difficult to determine which one of the objects is more detectable. This paper presents a new calculation method which allows characterizing the scattering properties of each object only with a few numbers: specific RCS (same as normalized RCS) and RCS dispersion. The presented method can be simply used to assess the visibility of the objects placed on different background surfaces.

A microstrip filtering balun with a wide stopband is presented. Its filtering function is realized by four meandering stepped impedance resonators (SIRs). Except for an identical fundamental-mode resonant frequency, the SIRs have different high-order resonant frequencies. Thus, the parasitic passbands are suppressed, and a wide stopband is achieved. The unbalance-to-balance transition is accomplished by introducing two coupling output ports at two symmetry positions of the output SIR. The voltages at symmetrical positions have equal magnitudes and opposite phases, thus, signals coupled from the symmetry positions also have equal magnitude and opposite phase, i.e., balanced output signals are achieved. A more general design approach is discussed in detail, and the proposed approach is similar to the design method of the conventional filter except that a small modification is made. Additionally, two kinds of external coupling structures, microstrip coupling lines and tapped line, are compared in terms of stopband performance. The comparison shows that better stopband performance is observed when utilizing the microstrip coupling lines as the external coupling structure. A filtering balun with central frequency of 2.4 GHz and Chebyshev frequency response is designed, fabricated and measured. The measured results give a reasonable agreement with the simulated ones, which verifies the effectiveness of the filtering balun.

In this letter, an interdigital band-pass filter is proposed for out-of-band rejection improvement. Seven quarter-wavelength resonators are employed to form the passband. Three extra transmission zeros (TZs) on both sides of the passband are implemented by introducing source-load coupling and dumbbell defected ground structures (DGS). As demonstrated by the measured results, out-of-band rejection and selectivity are improved by these three TZs, and good performances are achieved. The proposed method of increasing out-of-band rejection is feasible and applicable in the design of modern microstrip filters.

A dual-band microstrip distributed multiplier with two multiplication factors based on the extended composite right- and left-handed (E-CRLH) transmission lines (TLs) is presented. Dual-band operation for distributed multiplier is achieved by three cells, and each cell consists of a transistor, microstrip TL and E-CRLH transmission line. The distributed multiplier exhibits two multiplication factors in two different frequencies: one multiplication factor in reverse direction and the other multiplication factor in forward direction. The excellent agreement between proposed technique and measurement results confirms the accuracy and efficiency of the method.

The paper is devoted to experimental and theoretical study of spectra zone characteristics of the wire medium metamaterial with mechanically tunable unit cell. We experimentally demonstrated the effective control possibility of the spectral characteristics of wire medium metamaterial by varying its elementary unit-cell geometry. We established conditions under which the experimental implementation of the wire medium metamaterial at microwaves possesses the properties of a plasma-like medium and the properties band gap structure. A good agreement between the experiment and theory is demonstrated.

In this paper, a new diode-clamped multilevel inverter for capacitor voltage with inserted inductors is proposed. The key is to solve the voltage unbalance of diode-clamped multilevel inverter (DCMLI), which utilizes fewer switches and adopts a simpler control strategy. In this way, the cost and volume of the DCMLI can be effectively reduced. Firstly, the new five-level inverter topology is analyzed in detail under different operation modes. Then, the proposed topology extended to (2n+1) level inverter is introduced and discussed. Finally, both simulation and experiment results are demonstrated to verify the validity of the proposed topology.

This paper presents an improved structure of a Gysel combiner/divider suitable for high-power applications. The proposed structure makes use of stepped-impedance load line features to implement a simple, compact, low loss and sufficiently wideband Gysel configuration. It also improves isolation and facilitates design flexibility for the load location. Measurements agree with expected simulated results thus, demonstrating the proposed structure with a 10% fractional bandwidth while maintaining 20 dB of return loss and 0.25 dB of insertion loss.

An alternative representation of a Green function for electric fields on surfaces of thin impedance vibrators is proposed. The representation can be applied in software packages for simulation of RF and microwave devices. Advantages of the approach were demonstrated by analyzing the well-known problem of a thin symmetrical horizontal vibrator above a perfectly conducting plane. For a half-wave vibrator, numerical estimates of an effective external induced impedance were made for various distances between the vibrator and the plane. A possibility to realize a distribution of intrinsic impedance on the vibrator capable to compensate of the plane influence was also analyzed.

A novel UWB antenna with adjustable rejection bandwidth is proposed and fabricated. The proposed antenna consists of a monopole and a novel dual-T square resonator. The results demonstrate that a wide rejection bandwidth from 10.4 to 11.5 GHz can be achieved, and the rejection bandwidth can be adjusted by transforming the dimensions of dual-T square resonator. Moreover, reflection coefficient curve with two poles at one rejected bandwidth is also obtained which is induced by the proposed novel square resonator. In addition, to explain the mechanism of adjustable rejection bandwidth, the analysis of parametric study and electric field distributions of the design are given. The total volume of the antenna is 27 mm×19 mm×1 mm. Compared to other recent works, a simpler structure, wider rejection bandwidth and more compact size are the key features of the proposed antenna. Owing to its adjustable bandwidth and simple structure, the proposed antenna can be used in UWB communications applications to suppress the radio-frequency interference.

An electrodeless measurement technique of complex dielectric permittivity of high-K dielectric films is described. The technique is based on a quasi-optic Fabry-Perot resonator and modified for investigation of two-layer dielectric structures --- substrate/K-film. This procedure is destined to be used for providing a simple intermediate control of parameters of high-K films before the following technological process. Regimes of measurements providing the most sensitive conditions for definition of film parameters are considered. The proposed method is tested on two-layer structures with well-known parameters and is used for characterization of ferroelectric (Ba,Sr)TiO₃ films in the millimeter wavelength range (~50 GHz).

A study of the Hebron two-way radio tower in Halhul, which is part of the two-way radio network that links Bethlehem tower in the West Bank to Khan Younes tower in Gaza strip, was conducted. Hebron Tower was built over the highest spot in the region, 1027 m above the sea level. Measurements of signal power was conducted for Hebron tower and compared to various other transmitting towers seen from the area. Analysis reveals that power densities of all towers are invariably safe, and their power densities fall below international safe standards. Results show that power densities from Orange cellular tower, 3500 m away and Marah radio tower, 2350 m away from Hebron tower were indeed higher than all others measured, when all power densities were referenced back to 30 m of their respective tower antenna positions. As far as the Hebron tower is concerned, its height of 111m provides a relative safe umbrella, from electromagnetic radiation hazard, away from the main radiation beam, over the area below it.

A compact quad-band slot antenna is presented in this paper. The proposed antenna consists of ground plane, dielectric material and top radiation patch. Firstly, symmetrical L-shaped slots are inserted in a radiation patch. Then to achieve multiband performances, symmetrical square spiral slots and a snakelike area with two symmetrical arms enclosed by a long slot in the ground plane are adopted. The process of design and parametric studies are illustrated in detail. The final quad-band antenna has a small size of 0.22λ_g×0.28λ_g = 17×22 mm² (where λ_g is the guide wavelength) and covers the frequency bands from 2.39 to 2.48 GHz for lower WLAN, 3.64-3.73 GHz for downlink and 5.98-6.30 GHz for uplink standard satellite communications, and 6.97-7.18 GHz mainly used by the Indian National Satellite System (INSAT). The measured results of the proposed quad-band antenna are in accordance with simulated analysis and show good performance of return loss characteristics, radiation patterns, bandwidths and gains. Especially, with a very small size, the proposed antenna is suitable to be integrated with a portable device for varieties of wireless communication applications.

Design, optimization, and performance analysis of a three-phase field-excited flux switching (FEFS) motor to be employed for the future hybrid electric vehicle (HEV) drive applications is investigated in this paper. The stator of designed motor made of electromagnetic steels is composed of unique field mmf source and armature coils while a rotor is made of iron stack. This design has been evaluated in order to achieve power and torque density higher than 3.50 kW/kg and 210 Nm, respectively, so as to compete with the interior permanent magnet synchronous (IPMS) motor commonly installed in HEV. Given its robust rotor structure, the maximum achievable motor speed went up to 20,000 rpm. To perfect the motor design, a deterministic optimization approach was applied to meet the stringent performance requirements. In addition, experimental analyses were carried out to confirm the effectiveness of the proposed motor. Positively, the proposed FEFS motor has proved to be a suitable candidate of non-permanent magnet motor for efficient and safe HEV drive.

A low-profile wideband multiple-input-multiple-output (MIMO) antenna is presented. The proposed antenna is suitable for mobile terminals applications, as its measured -10 dB bandwidth ranges from 1.56 GHz to 2.77 GHz. The overall antenna efficiency ranges from 68% to 83% over the operating bandwidth. The overall size of the proposed antenna is 60×97×0.8 mm³. A novel isolation structure is employed to achieve isolation range of -26 dB to -16 dB. The radiation patterns are measured, and envelope correlation coefficient is evaluated. The simulated and measured results are in good agreement.

This paper describes the concept and design of a novel compactself-supported cup feedantenna for parabolic reflectors. The feed antenna consists of an open waveguide cup which is excited by a disk loaded dipole. This structure is fed by a coaxial waveguide through a split-coaxial balun and has a rear radiation pattern toward the reflector antenna. Two different types of this configuration are designed in this paper: a linearly-polarized grid reflector antenna fed by a single dipole excitation, and a circularly-polarized solid reflector antenna fed by a cross dipole excitation. The measurement is done for the former, and simulation results of the latter via two different software packages CST and HFSS are compared in this paper. Analyzing the results shows that both types of cup feed antenna have an excellent aperture efficiency and low side lobe level.

A highly efficient hybrid method of single integral equation (SIE) and electric/magnetic current combined field integral equation (JMCFIE) is presented, named as SJMCFIE, for analysing scattering from composite conductor and dielectric objects, in which, SIE can reduce one half unknowns in dielectric region. The resultant matrix equation of SJMCFIE can be represented in the iteration form, which makes the computation complexity reduced further, and coupling mechanism of composite model becomes more explicit. For accelerating matrix-vector multiplications (MVMs), Multilevel Fast Multipole Algorithm (MLFMA) is employed to combine SJMCFIE to formulate SJMCFIE-MLFMA at last, which is the extension of SIE-MLFMA in the proposed reference. Finally, some examples verify the new hybrid method on accuracy, memory storage, computation efficiency compared to SIE-MLFMA and JMCFIE-MLFMA. Besides, SJMCFIE-MLFMA can also be used to analyse the complete coated model's scattering.

In this paper, we propose a systematic simulation-based approach to estimate the reading distance of an RKE system. In our electromagnetic (EM) simulation, a receiving RKE antenna and a vehicle structure, including both exterior and interior, are modeled as piece-wise mesh triangles to obtain accurate radiation characteristics of the antenna mounted inside the vehicle. The reading distance is then estimated by a two-ray propagation model that includes effects of space loss, ground properties, and antenna polarizations for various orientations and heights of handheld devices. The estimated distances are compared to the measurement, and results show that the proposed approach is suitable to replace the measurement-based approach with an average error of less than 2 m.

The main section of this paper comprehensively analyzes electrical shielding effectiveness (ESE) of enclosures with rectangular apertures for producing valuable information used in electromagnetic interference and compatibility guiding enclosure designers of electronic devices. Firstly, results of conventional analytical equivalent circuit model, measurement and simulation with computer simulating technology (CSTTM) of ESE for an enclosure with a single aperture size are compared to improve closeness in different models at 0-1 GHz. After getting a suitable simulation model, all possible parameters with detailed cases are examined to approach beneficial conclusions. Especially, size of enclosure, aperture size, aperture shape, configuration and number of apertures, probe position parameters that affect ESE are investigated. Also, some double parameters are analyzed together to achieve detailed review as two enclosure dimensions, two aperture dimensions and probe position with enclosure depth. Therefore, three-dimensional graphical investigations are performed. Obtained results of these parametric approaches are explained with acceptable reasons. Finally, detailed and itemized comments are given about simulated results of ESE parameters, which are collected from previous sections.