This paper proposes a cascaded multilevel converter to reduce the number of IGBT switches for the purpose of improving system stability and decreasing switching losses. This converter can eliminate second-order ripple caused by energy exchange between grid and batteries, and thus extend battery life. This cascaded connection between the equivalent buck/boost circuit and the half-bridge inverter is also able to reduce the number of switch tubes. A control strategy based on state of charge (SOC) closed-loop tracking is designed to implement the errorless follow-up control of average SOC values for electric vehicle batteries. The equivalent circuit under different working modes of the topology is analyzed, and the effectiveness of the control strategy is verified. Simulated and experimental results show that this converter can effectively achieve grid connection requirements and balance the battery units to meet practical needs.

This paper presented the effects of Defected Waveguide Structure (DWS) toward wideband monopole antennas. Ultra-wideband (UWB) technology was introduced to support high data rate and maximum bandwidth utilization. Monopole antenna received great attention owing to its appealing features of planar in the structure and is easy to manufacture in miniaturized sizes. Yet, poor gain and directivity are always the drawbacks of the miniaturized antennas. It was found that there was no research work done on the monopole antenna design with DWS. Two wideband monopole antennas with a microstrip feed line and coplanar waveguide (CPW) feed line were proposed. Two waveguides with full copper and square DWS were designed at all the inner walls. Monopole antennas were then integrated in the waveguides. The antenna parameters studied were return loss, efficiency, gain, directivity and radiation pattern to investigate the effects of DWS toward monopole antennas. Both monopole antennas achieved wide bandwidth from 2.5 GHz to 11 GHz and higher efficiency of more than -2 dB. Monopole antennas with waveguide presented a narrower bandwidth from 6 GHz to 11 GHz but a significant directivity improvement of 5 dBi at a lower frequency of 4.5 GHz. Monopole antenna with square DWS demonstrated high directivity and gain in a wide bandwidth of 8.5 GHz. Higher gain was improved around 4 dB at the frequency of 4.5 GHz, and high efficiency of more than -2 dB was achieved. The DWS design served as a guide for future communication system based on the smart technology system.

Airborne and spaceborne optical remote sensing is an important means formonitoring oil slicks on ocean surface. However, it is still a major challenge to determine both the category (related to a specific value of reflective index) and thickness of the marine oil slick with existing methods, particularly when the oil slick is too thin to obtain significant fluorescence signal with a laser induced fluorescence method. Sun-glint is usually harmful to optical remote sensing of an ocean target. In this work we utilize the polarized sun-glint reflection to monitor oil slicks on a rough ocean surface.The degree of linear polarization (DOLP) of the sun-glint reflection contains the characteristics information of the oil slick with different physical properties. Combiningthe polarized optical remote sensing and the inversion theory based on a thin-film optical model, weanalyze the variation trend of the DOLP with the parameters of solar zenith angle, sensor zenith angle, relative azimuth angle, refractive index and thickness of the oil slick. Different types and thicknesses of the oil slicksgive different Fresnel's reflection coefficients of polarized sun-glint reflections and consequently different Stokes parameters, which lead to different DOLP. We analyze the DOLP of the sun-glint reflection at the wavelength of 532 nm,and determine simultaneously the refractive index and thickness of marineoil slick from the DOLP values measured by a remote detector at two different zenith angles.

Reflective filters are characterized by a frequency response with good matching at the band of interest and usually reactive impedance out of those frequencies which may adversely affect the system performance. On the other hand, reflectionless filters are characterized by good matching characteristic not only at the interest frequencies, but in the whole frequency spectrum which improves the overall linearity, efficiency, and reduces instability scenarios at the system level. Although several reflectionless structures can be found in the literature, the concatenation of different reflectionless sections, combined with the use of acoustic resonators has not been exploited yet. The particular electrical behavior of acoustic wave resonators, where two different resonant frequencies are found, allow to obtain a frequency response with high selectivity due to the presence of transmission zeros below and above the passband. A bandpass filter has been designed following the described procedure with a fractional bandwidth FBW = 2%, a pair of transmission zeros below and above the bandpass, and an improved out-of-band rejection with respect conventional topologies.

This paper reports on the development of a compact, low-cost, impulse bi-static UWB radar sensor for its use as non-destructive methods for electrical property measurement in industrial application. This UWB Radar sensor consists of an ultrashort-monocycle-pulse transmitter of 330 ps, an oscilloscope as a UWB sampling receiver with a high wide band of 6 GHz, and two UWB antennas ranging from 0.4 to 6 GHz. A new model of SRD has been introduced in order to decrease the rise time of the impulse. Performance of this UWB radar sensor was veried through two kinds of applications: range detection and electrical property measurements. All measurements have been carried out in an anechoic chamber with a distance variation between 80 and 300 cm. The full radar system provides good agreement between the experimental and theoretical results, which demonstrate its application in many fields, especially for electrical Property Measurements.

In the moment method solution of the integral equations for currents of a rectangular microstrip patch reflectarray, the Leontovich boundary condition is employed to determine the conductor loss. If the basis functions contain edge conditions that approach infinity, the moment matrix elements will have diverging integrals in the Galerkin technique. In this paper, we present a criterion to stop the evaluation of these integrals at a distance before the edge, thereby avoiding the divergence problem. The stopping distance derived here is found to work for a range of values of permittivity, loss tangent, and thickness of the substrate, polarization, angles of incidence of the plane wave source, and also for superstrates. Our computed results are in good agreement with measured results and those computed by HFSS.

The derivation of the scattering matrix of hybrid directional couplers with more than four ports is rather difficult to find in the literature. Some particular cases can be found, but a general form is not yet discussed. The aim of this contribution is to develop a simple procedure to write the 2N×2N S-matrix for hybrid directional couplers with N input and N output ports. This procedure is based on the separation of the phase of the scattering coecients in two terms. The first is related to the presence of transmission lines, or phase shifters, connected to the coupler ports and the second to the intrinsic nature of the coupler that imposes particular phase relationships to the scattering coecients to ensure that the S-matrix is unitary. These relationships are due to the presence of one polyphase systems of order N or to m polyphase subsystems of order N/m, if N is multiple of m. Finally, it will be shown that 2N port hybrid directional couplers with phase shift equal to 0 or π are possible only if N is an integer power of 2.

Electromagnetic wave propagation suffers attenuation and phase rotation by suspended dust particles especially in arid and semi-arid regions where occurrence of sand and dust storms (SDS) is predominant. The SDS phenomenon has received considerable interest in recent times with emphasis on signal attenuation and phase rotation effects. To this end, mathematical models of dust induced complex scattering are developed and proposed in this paper using Rayleigh method to compute attenuation and phase rotation of electromagnetic waves by considering dust particle shapes and best fit ellipsoids. This work also presents a new expression for the relation between visibility and dust concentration. The expression was included in the proposed models whose simulated results, compared with some published results, show close agreement. Attenuation and phase rotation in dry dust are found to be significant only when visibility becomes severe or at increased microwave bands.

In this paper, a novel X-band push-push oscillator employing dual-feedback sub-oscillators and a half-wavelength microstrip line resonator is presented. The dual-feedback sub-oscillator consists of a series feedback commonly used in conventional oscillators due to its good phase noise performance and a parallel feedback circuit which improves both the output power and stability. The resonator and power combiner form a single circuit allowing compact size. Measured results show that an excellent output power of +13.3 dBm was obtained at the second harmonic frequency of 9.81 GHz. Moreover, superior phase noise of -105.0 dBc/Hz and -123.5 dBc/Hz were achieved at 100-kHz and 1-MHz offset frequencies, respectively. The suppression of undesired harmonic signals, namely fundamental and third harmonic signals, are 27.9 dB and 55.7 dB, respectively. With a simple design structure and compact size the proposed push-push oscillator achieved very good performance.

A conformal wideband antenna is investigated and compared with its planar counterpart. First, a planar U-slot patch with about 43% fractional impedance bandwidth is designed. Then, it is mounted on a conformal cylindrical structure. It is observed that the fractional impedance bandwidth of the resulting conformal antenna increases to 50%, when it is bent along the H-plane. It is also found that the cross polarization discrimination of the antenna is improved. The effects of the arc angle and radius of the cylinder on the impedance bandwidth and radiation characteristics of the antenna are extensively studied. The conformal antenna was fabricated on a thin film of Kapton and tested. The measured and simulated results closely resembled each other.

This letter presents the development of a miniaturized and folded multisection quadrature hybrid for ultra-wideband (UWB) applications. For a size reduction, Stages 1, 2 and 3 are placed on the top of PCB, and Stages 5, 7 and 7 are placed on the bottom of PCB. The transition between top and bottom layers uses via transitions. Stage 4 is proposed with vertical via transitions and microstrip lines on the top and bottom sides of PCB, which is helpful for bandwidth increment and size reduction. The overall size of the proposed UWB hybrid is only 21 mm by 14 mm, and a size reduction of 50% is achieved compared with a planar multisection one. Performance comparisons are also implemented and discussed compared with a planar one.

In this paper, a novel low-cost, high gain dual-polarized antenna design with a suspended cylinder and a ground connected cylinder geometry is proposed. The design structure of the antenna is simple and fabricated with two cylinders, two shorting strips, and a circular ground plane. All these components are easily fabricated from a copper sheet of thickness 0.4 mm, and the antenna is fed by two coaxial probes at the orthogonal planes on the circumference of the cylinders. A prototype is designed, fabricated and measured. The measured results show that the prototype has -10 dB impedance bandwidth of 34.37% at port 1 & 34.21% at port 2. Broadside gain from port 1 is 10.2-10.4 dBi & port 2 is 10.25-10.52 dBi, which indicates that the antenna has flat gain over the impedance bandwidth, and isolation between the ports is more than 15 dB from 2.65-3.6 GHz and more than 20 dB from 2.75-3.55 GHz. The isolation of the proposed antenna is improved by shorting the suspended cylinder to the ground plane by two shorting strips. The resonance frequency and isolation peak are simultaneously tunable with varying the width of the shorting strips. The parameters of the antenna are optimized by using HFSS, and good agreement between the simulated and measured results is obtained. The proposed dual polarized antenna can be used for base station applications such as LTE (Long Term Evolution) and WiMAX (Worldwide Interoperability for Microwave Access).

In this paper, we present a hybrid system consisting of a novel design of a microstrip antenna that can be designed to resonate at various frequencies within the ultra-high frequency (UHF) band (e.g. 415 MHz, 905 MHz, and 1300 MHz), combined with a pair of high frequency (HF) coils (13.56 MHz). The system is designed to be fabricated on an FR4 substrate layer, and it provides a compact solution for simultaneous wireless power transfer (WPT) and multi-band wireless communication, to be utilized in implanted medical devices. The external antenna/coil combination (EX) will be located outside the body on the skin layer. The EX has 79.6 mm-diameter. The implanted hybrid combination (IM) has 31.5 mm diameter. The antenna is designed such that by varying the position of a shorting pin the resonance frequency can be switched among three frequencies; therefore, the same design can be used for various applications. The system was designed using numerical simulation tools, and then it was fabricated and measured. The design was optimized while the performance of the system was numerically simulated at various depths inside a layered body model. Furthermore, the insertion loss (S₂₁) and transmission efficiency (η) for both antenna and coil pairs at different depths were studied through simulation and measurements. The system provides a good solution for the combination of power transfer and multi-band data communication.

The scattering center extraction algorithm is a method to estimate the scattering center from the backscattered field. Superior scattering center extraction algorithms should be robust to noise, independent of the model order, and automatically and quickly operated. In this paper, we propose a novel super resolution scattering center extraction algorithm that satisfies the conditions mentioned above, which has been named the dimension reduced optimization problem (DROP). Using DROP, we determined a one-dimensional scattering center from a high resolution range profile and a two-dimensional scattering center from an inverse synthetic aperture radar image.

In this paper, the polarizations of single-feed crossed-dipole antennas loaded with different near-field resonant parasitic (NFRP) elements are investigated. The antennas are placed above a metallic reflector for a broadside radiation pattern. Meander line with an arrowhead-shaped ending is applied in all arms of the crossed-dipole and NFRP elements for the compactness. By adjusting the ending sizes of the NFRP element, the polarization of antenna can be right-hand circularly polarized (RHCP) - linearly polarized (LP) - left-hand circularly polarized (LHCP). For validation, two antennas with RHCP and LHCP performances are implemented and measured. The RHCP antenna yields a |S₁₁| < -10 dB bandwidth of 1.454-1.668 GHz (214 MHz) and a 3-dB axial ratio (AR) bandwidth of 1.525-1.585 GHz (60 MHz). The LHCP antenna yields a |S₁₁| < -10 dB bandwidth of 1.475-1.702 GHz (227 MHz) and a 3-dB AR bandwidth of 1.535-1.580 GHz (45 MHz). Moreover, both antennas yield a good broadside radiation with a gain of > 6.0 dBic and a radiation efficiency of > 65% across their operational bandwidth.

Thermal effects limit the gain, quality, and stability of high power fiber lasers and amplifiers. In this paper, different values of heat conductive coefficients at the core, the first and second clad with the complete form of the heat transfer equation are considered. A quartic equation was proposed to determine the temperature at the fiber laser surface. Using the surface temperature value, the temperature can be determined at the longitudinal and radial position of the double clad fiber laser. The different definitions of heat sources which were previously presented in articles is used to describe the heat generation at a double clad high pump power fiber laser condition. The results were compared to each other, and the percentage of each factor in heat generation was calculated.

A compact composite right/left-handed (CRLH) bandpass filter with wide out-of-band rejection, which utilizes a substrate integrated waveguide (SIW) and modified complementary split-ring resonators (CSRRs) is presented. By incorporating two sets of CSRRs resonators (the top and bottom CSRRs) into SIW cavity, the proposed filter obtains a high selectivity. Besides, the filter has the CRLH property, and no additional areas are required because of the structure of the top CSRRs and the gap between them. At the same time, two slots of etched units used in feeding lines are replaced to obtain a wide out-of-band rejection. Finally, the measured results show that the filter has a wide stopband with rejection over 20 dB up to 4.3 times of the center frequency, implying that the experimental results are in good agreement with simulated ones.

This paper describes a wideband transmitting adaptive digital beamforming (ADBF) scheme with nulls in the direction of interference. The scheme partitions the wideband transmit signal into independent sub-bands using an analysis filter bank behind each array element. In each channel, sub-band ADBF weight vector is computed based on the minimum variance criterion with multiple linear constraints to form the sub-band transmit beam. Finally, a wideband transmit adaptive beam is reconstructed through the synthesis filters. Theoretical analysis and simulation experiments show that this algorithm can form a wideband transmit beam with deep nulls, and the pointing direction of the null keeps unchanged regardless of frequency. The algorithm proposed in this paper has little computation load and is efficient to implement in engineering applications.

A three layered low profile dodecagon shaped band stop frequency selective surface (FSS) is presented in this paper for X band rejection applications. The three layers are placed in a manner which is complement to each other. The low profile three layered FSS with unit cell dimensions on the order of 0.2λ₀x0.2λ₀ (at lower center frequency of 8.2 GHz) with overall thickness of three layers including air gap of 5.2 mm is presented. For experimental verification, a three layered FSS has been fabricated and measured. Simulation results show that the designed three layered FSS can provide a stopband from 8 GHz to 12.5 GHz with two transmission zeros of 8.2 GHz and 10.2 GHz with a fractional bandwidth of 45%. The complete design and equivalent circuit model (ECM) of the three layered FSS are presented in this paper.

This paper describes the radio propagation measurement campaign in the sugarcane field representing a tall food grass characteristic which is one of the common types in outdoor agriculture environments. The measurement was conducted by using a channel sounder having a bandwidth of 45.6 MHz at 2.45 GHz with the aim at investigating the propagation channel characteristics which are useful in deploying of wireless sensor networks in the precision agriculture. By analogy to Ikegami model, the variation of path loss over the relative angles between the plant rows and the line-of-sight direction from the transmitter to the receiver is identified. Utilizing this knowledge, this work justifies the procedure of predicting the path loss at any point in the field by a few measurement efforts. Furthermore, the Rician K-factor and RMS delay spread are investigated in the vegetation depth shorter than 40 m. The result shows that the relationship between the Rician K-factor and its corresponding path loss value in each measurement point can be fitted with the log-linear line. This leads to the possibility of predicting K-factor at any points in the field. In addition, since the result of RMS delay spread is independent to the vegetation depth and the density of the plant, it is represented by the statistical model in which the Weibull distribution provides the best representation.