A new design of high selectivity wideband bandpass filter based on transversal signal-interaction concepts loaded with open and shorted stubs is proposed in this paper. Two transmission paths are used to realize signal transmission. Path 1 is composed of a T-shaped structure with shorted stub, and Path 2 consists of two open coupled lines loaded with open stubs. A wide five-order passband and high selectivity stopband with four transmission zeros can be achieved in the proposed filter. Finally, a wideband bandpass filter operating at 3 GHz with 3-dB fractional bandwidth of 83.3% (1.55 to 4.05 GHz) is designed, fabricated, and measured. Good agreement between the simulation and experiment is obtained.

Magnetically coupled resonant wireless power transfer (WPT) has been employed in many applications, including wireless charging of portable electronic devices, electric vehicles and powering of implanted biomedical devices. However, transmission efficiency decreases sharply due to divergence of magnetic field, especially in under coupled region. Electromagnetic (EM) metamaterial (MM) can manipulate the direction of EM fields due to its abnormal effective permittivity or permeability. In this paper, an ultra-thin and extremely sub-wavelength magnetic MM is designed for a 13.56 MHz WPT system to enhance magnetic field and its power transfer efficiency (PTE). The WPT systems are investigated theoretically, experimentally and by simulation. A relatively high maximum efficiency improvement of 41.7% is obtained, and the range of efficient power transfer can be greatly extended. The proposed MM structure is very compact and ultra-thin in size compared with early publications for some miniaturized applications. In addition, large area, homogeneous magnetic field is obtained and discussed using the proposed MM. Finally, the proposed MM is applied in a more practical WPT system (with a low power light bulb load) to reveal its effects. The bulb brightness intuitively verifies the efficiency improvement in the WPT system with the MM.

Recent technological achievements have made it low cost to realize indoor localization using the received signal strength (RSS) information from Wi-Fi signals. However, the current RSS-based indoor localization techniques have two major challenges: one is that the RSS signal is quite sensitive to channel conditions, and the other is that sufficient number of access points (APs) is needed to provide enough RSS measurements for guaranteeing good performance. To solve these problems, this paper proposes an adaptive compressive sensing (CS) based indoor localization method based on the IEEE 802.11 Wi-Fi standard. The novel feature of this method is to dynamically adjust both the dictionary and the sparse solution using an online dictionary learning (DL) technology so that the location solution can better match the real-time RSS scenario. Meanwhile, an improved approximate l₀ norm minimization algorithm is presented to enhance sparse recovery speed and reduce the number of APs required by indoor localization systems. The effectiveness of the proposed scheme is demonstrated by experimental results where the proposed algorithm yields substantial improvement for localization performance and reduces computation complexity.

This letter presents a compact hexa-mode microstrip resonator which is originated from a traditional stub-load resonator (SLR). Stub in SLR isreplaced by a couple of square-loops in the proposed resonator. The advantage of this replacement is that six modes emerge to realize a compact size, and more transmission zeros are generated in its application on filter to enhance the frequency selectivity. For demonstration, a compact dual-band microstrip filter using the proposed resonator is designed in 2.4 GHz/5.2 GHz of WIFI channel, and six transmission zeros are generated to enhance the frequency selectivity.

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.