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Examines the use of distributed, monolithic travelling-wave amplifiers. Guidance on reducing amplifier noise by rendering dipole-domain-generated noise contributed by the individual field effect transistor (FET); Use of insulated gate FET to permit higher gate breakdown voltage operation in the accumulation mode; Reduction of even harmonics and the improvement of efficiency.

This paper elucidates the working of shunt active filters in dynamically varying grid conditions. The accuracy of harmonics eliminated is based on the harmonic extraction technique and the switching techniques used. The harmonics of the electrical system are computed and based on the various harmonics produced; the shunt active filter has to supply a compensating current in opposition at the point of common coupling. Space Vector Pulse Width modulation (SVPWM) is an effective switching technique used but its performance is not satisfactory in the over-modulation regions. In this paper, optimised switching technique using a neural network for SVPWM is used which has lesser computation time and computes the gating pulses effectively in the over-modulation regions. Shunt active filter mitigates the impact of harmonics even in the over-modulation regions. The hardware is implemented using FPGA Spartan 6 controller, which utilises fewer hardware resources. The optimised switching topology results with improved harmonic reduction even in the over-modulation regions with unbalanced loading conditions is presented in this paper. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to provide a robust solution for fault detection in the induction motor. The structure of nonlinear unknown input observer is investigated for observer design in this paper. Recently, rotor defect is considered as the most important non-electric fault in induction motors. One of the challenges in rotor fault detection is the uncertainty in the mechanical load of the motor and the harmonics in the electric power. Accordingly, these cases are considered as disturbances for unknown input observer and their effects on the residual signal are eliminated. The results of the simulation show the performance of the observer to diagnose the induction motor rotor fault in different scenarios. [ABSTRACT FROM AUTHOR]

In recent wireless communications, spectrally flexible transmissions such as carrier aggregation and cognitive radio pose severe challenges for the high-efficient radio-frequency power amplifier (PA) design. The non-linear characteristics of PAs may yield substantial unwanted emissions that can violate the emission limits, thus interfere with other communication systems within the frequency vicinity. Furthermore, in frequency-division duplexing systems, if the unwanted emissions happen to fall into the intended receiver band, it may cause severe receiver desensitisation. In this paper, we present a novel digital predistortion (DPD) technique based on a frequency selective architecture, which is aimed at reducing the unwanted harmonic emissions at any pre-specified frequency and linearising the fundamental signal at the same time. The method can simplify the predistortion structure compared with the whole spurious suppression DPD method and thus reduce the computational complexity of the predistortion process. Furthermore, the identification of the DPD coefficients is based on a breeding particle swarm optimisation algorithm, which can enhance the calculation flexibility as well accelerate the convergence speed compared with traditional gradient methods. Both simulation and measurement results demonstrate sufficient spur suppression at the target frequency. [ABSTRACT FROM AUTHOR]

In this paper, a synchronous reference frame (SRF) method based on a modified phase lock loop (PLL) circuit is developed for a three-phase four-wire shunt hybrid active power filter (APF). Its performance is analysed under unbalanced grid conditions. The dominant lower order harmonics as well as reactive power can be compensated by the passive elements, whereas the active part mitigates the remaining distortions and improves the power quality. As different control methods show contradictory performance, fuzzy logic controller is considered here for DC-link voltage regulation of the inverter. Extensive simulations of the proposed technique are carried out in a MATLAB-SIMULINK environment. A laboratory prototype has been built on dSPACE1104 platform to verify the feasibility of the suggested SHAPF controller. The simulation and experimental results validate the effectiveness of the proposed technique. [ABSTRACT FROM AUTHOR]

This paper proposes a harmonic elimination technique for online reducing harmonics in voltage source inverters. In the presented method, in order to provide required fundamental voltage and eliminate specified harmonics simultaneously, the value of the switching angles are determined using a new efficient optimization algorithm named Enhanced Teaching-learning-based Optimization (ETLBO). The efficiency of the presented strategy is validated on three-phase seven-level diode-clamped inverter while other structures of multi-level inverters (MLIs) can be employed. The aim is to reduce the Total Harmonic Distortion (THD) in multilevel converter. In this paper, a new optimization algorithm named ETLBO has been successfully implemented to achieve optimal switching angles in order to harmonic elimination in MLIs. A three-phase seven-level diode-clamped MLI has been selected as a test case to validate the effectiveness of the proposed method. The simulation results demonstrated the ETLBO method not only is in preference to the Genetic Algorithm and Particle Swarm Optimization for including no user-defined parameter and simple implementation, but also for providing higher quality solutions. Moreover, in order to verify the superiority of the ETLBO algorithm over conventional methods for harmonic elimination, the Newton-Raphson (NR) method was implemented to find optimal switching angles. The results obtained by the NR method compared with those of the ETLBO and the superiority of the ETLBO in terms of the both computational time and the resulted %THD was concluded. As a whole, the results show that the ETLBO algorithm is expected to become widespread in power systems where on-line updating harmonics is needed since it provide accurate and high-quality solution in extremely short time. [ABSTRACT FROM AUTHOR]

Online detuning state detection and the subsequent detuned element identification of a passive filter bank is of great concern in regard to achieving condition-based maintenance of an HVDC transmission system. In this paper, a novel method that can rapidly detect the online detuning state of filter banks with arbitrary structures of an HVDC system and accurately identify the detuning element is proposed. The method is based on the calculated amplitude change rates (ACRs) of several deliberately selected harmonic components of the measured real-time current in each branch of the filter. The principle and the implementation of the proposed method are presented, and the relationship between the ACR of the harmonic current and the detuning degree of an individual element is deduced theoretically. Based on the above works, the criteria for identifying the detuning state of the filter bank, the detuned element in the series and parallel part of the filter, and the detuning degree of the element are given. Diverse simulation results, such as applications on a single- and a double-tuned DC filter bank, sensitivity analysis and performance comparison, are provided to show the correctness and the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive unscented Kalman filter for parameter estimation of non-stationary signals, like amplitude and frequency, in the presence of significant noise and harmonics. This paper proposes an iterative update equation for model and measurement error covariances Q and R to improve tracking of the filter in the presence of high noise. The initial choice of the model and measurement error covariances Q and R, along with the UKF parameters, are crucial in noise rejection. This paper utilizes a modified particle swarm optimization (MPSO) algorithm for the initial choice of the error covariances and UKF parameters. Various simulation results for time varying signals reveal significant improvement in noise rejection and accuracy in obtaining the frequency and amplitude of the signal. [ABSTRACT FROM AUTHOR]

In this paper the stability of a multifrequency model of a PWM converter is investigated. A multifrequency model is a model based on Fourier series that contains as a special case the so-called state space average model. In contrast to a state space average model a multifrequency model may also include so-called higher order harmonics, where the zeroth order harmonic corresponds to the (moving) average. This paper focuses on a specific PWM converter, namely a Ćuk converter, and it is proved that a multifrequency model of a Ćuk converter with fixed duty ratio is asymptotically stable. This result generalizes the known corresponding result for a state space average model of a Ćuk converter with fixed duty ratio. Taking all the harmonics into account the result also illustrates the well-known fact that a Ćuk converter with a fixed duty ratio and a finite switching frequency is asymptotically stable in the following sense. If the signals in a Ćuk converter do not correspond with a periodic behaviour, they will however do so in the limit, i.e. as time goes to infinity the signals will become periodic, and this limiting periodic behaviour is unique. Although the paper mainly deals with the stability issues for a Ćuk converter, it is possible to use the ideas of the paper to derive similar results for other types of PWM converters. [ABSTRACT FROM AUTHOR]

This paper presents a shunt active filter for non-linear loads designed to minimise the harmonics presented in the three-phase three-wire system. Due to the large proliferation of power electronic control systems in our day to day life, the switching of these power electronic circuits induces harmonics in the sources which cause undesirable effects on the electrical components. Shunt active filter is a harmonic mitigating device comprising of voltage source inverter fed through a DC capacitor. The control strategy is based on extraction of harmonics using synchronous reference frame theory. The extracted harmonics are used to generate pulse-width modulation (PWM) signals using the space vector PWM (SVPWM) for the voltage source inverter which has reduced losses. The proposed method is modelled and simulated using Matlab/Simulink and the output shows that the total harmonic distortion of the supply can be reduced at the point of common coupling. [ABSTRACT FROM AUTHOR]

This paper presents a self-powered inductor-based converter which harvests thermoelectric energy and boosts extremely low voltage to a typical voltage level for supplying body sensor nodes. Electromagnetic interference (EMI) of the converter is reduced by spreading spectrum of fundamental frequency and harmonics via pseudo-random modulation, which is obtained via combining the linear feedback shift register and digitally controlled oscillator. Besides, the methods, namely extracting energy near MPP and reducing the power dissipation, are employed to improve the power efficiency. The presented inductor-based converter is designed and verified in CSMC CMOS 0.18-µm 1P6M process. The results reveal that it achieves the high efficiency and EMI reduction at the same time. [ABSTRACT FROM PUBLISHER]

The intent of this paper is to find out significant united electromechanical characteristics for online monitoring of stator interturn short circuit (SISC) faults. Different from other studies, this paper pays attention to neither the stator voltage and current, nor the winding inductance variation, but focuses on the faulty electromagnetic characteristics including the exciting current, the circulating current in the parallel branches (CCPB), and the electromagnetic torque (EMT). The simulation work is modeled for a QFSN-600-2YHG type turbo-generator and the experiment is taken on a MJF-30-6 fault-simulating generator to verify the theoretical analysis. The simulation result and the experiment data accord with the theoretical analysis and show that, as SISC occurs, second harmonics will be induced in the exciting current, first and third harmonics will be induced in the CCPB, and second and fourth harmonics will be produced in the EMT. Moreover, the corresponding time-domain waves will also fluctuate intensely, while the mean value of the exciting current and the EMT will be decreased. As SISC develops, the harmonic increment, the fluctuation intensity of the time waves, and the decreased rate of the mean value will be also increased. These united characteristics can be applied to the fault diagnosis and online monitoring on SISC fault. [ABSTRACT FROM PUBLISHER]

The article presents abstracts on electric power topics which include a five-level diode-clamped active power filter, a new approach to harmonic allocation, and the design and implementation of a radial magnetic bearing.

A tunable dual-band microstrip filter using step-impedance resonators with harmonic suppression and compact size is presented in this paper. The second passband frequency of the filter can be flexibly controlled by tuning the bias voltage across the varactor whereas the first passband frequency is fixed. The structure is composed of couple lines and capacitive-loaded stepped-impedance resonator to provide frequency tunability and folded to reduce the size of the filter. The coupling scheme applied in this paper helps to reduce insertion loss and eliminate parasitic parameters, which is due to that extra blocking capacitances that are needless compared with the conventional coupling structure. To certify the validity, a prototype dual-band filter is designed, fabricated, and measured. The measured results show good agreement with the simulated ones. [ABSTRACT FROM PUBLISHER]

This paper presents the analysis, design, and experimental results of a new integrated electronic ballast based on the half-bridge boost rectifier followed by the half-bridge series resonant parallel loaded inverter. The electronic ballast features a high power factor and low harmonics input current. The involved converters share the power switches, reducing costs significantly. The input stage of the ballast works in discontinuous inductor current mode with constant duty cycle and variable switching frequency. It is important to maintain this operating condition in order to get a high power factor. Integrating the power stages results in higher complexity in the control design because a close relationship still exists between the power stages. Within the paper, the operating characteristic is established in order to obtain a design method for the ballast. The obtained method is used to design a laboratory prototype for a 26-watt fluorescent lamp. Some experimental results are included. [ABSTRACT FROM AUTHOR]

This paper considers the linearisation of an asymmetrical two-way Doherty amplifier by the method that uses the second harmonics and fourth-order non-linear signals for linearisation. These even-order signals for linearisation are extracted at the output of the peaking amplifier, adjusted in amplitude and phase and injected at the input and output of the carrier amplifier transistor in the Doherty configuration. The effect of linearisation has been experimentally confirmed on a fabricated asymmetrical Doherty amplifier with the additional circuit for linearisation. The suppression of the third-order intermodulation products has been carried out for two-tone test, 64QAM and WCDMA digitally modulated signals in a range of signal power. [ABSTRACT FROM AUTHOR]

Free electron LASer in Hamburg is the first free electron laser user facility operating in the vacuum ultraviolet and soft X-ray wavelength range. Many user experiments require knowledge of the spatial and temporal coherence properties of the radiation. In this paper, we present a theoretical analysis of the coherence properties of the radiation for the fundamental and for the higher odd frequency harmonics. We show that temporal and spatial coherence reach their maxima close to the free electron laser (FEL) saturation but may degrade significantly in the post-saturation regime. We also find that the pointing stability of short FEL pulses is limited due to the fact that nonazimuthal FEL eigenmodes are not sufficiently suppressed. We discuss possible ways for improving the degree of transverse coherence and the pointing stability. [ABSTRACT FROM AUTHOR]

Multiple pulse width modulated (MPWM) AC choppers are gaining popularity over phase controlled circuits mainly due to the minimization of harmonics and the improvement in the input power factor. In this paper a direct digitally controlled MPWM AC Chopper using power transistors is described. A 120° chopping period is used for the main transistors in the three-phase power circuit to allow the circuit to accommodate loads of any power factor angle. Single-phase sensing is used to generate all control signals necessary for three-phase power control. The experimental results obtained with a three-phase prototype circuit are presented. The circuit described is expected to find extensive use in microprocessor based MPWM AC power controllers and AC line regulators. [ABSTRACT FROM AUTHOR]

Shunt active power filter (SAPF) is a well-established and widely accepted power electronic device for cancelling harmonic currents from electrical networks. The common configuration of SAPF utilises a proportional-plus-integral (PI) controller. However, the conventional approaches for determining the Picoefficients may not provide satisfactory results for a wide range of operating points (loads). This paper proposes to use the particle swarm optimisation (PSO) algorithm to determine the optimal coefficients of Picontroller for SAPF applications. The DC control approach is used to generate the reference harmonic signals from the non-sinusoidal load current while a hysteresis-based Picontroller is selected to control the compensating currents. Simulation results for a power network connected to a non-linear load are generated to investigate the dynamic performances of SAPF with the conventional-PI and enhanced PSO-Picontrollers. [ABSTRACT FROM AUTHOR]

Stepped impedance resonator (SIR) and asymmetric coupled-line sections are used to design a novel fifth-order wideband bandpass filter in this paper. Even- and odd-mode technique is introduced to design and analyze the filter. The proposed filter possesses the characteristics of spurious-free response up to the third harmonic frequency with two transmission zeros on each side of the passband, thus resulting in the improved selectivity. One prototype with 3-dB fractional bandwidth of 53% (2.2–3.79 GHz) is fabricated for demonstration, and good agreement can be observed between simulated and measured results. [ABSTRACT FROM AUTHOR]

Management of harmonic voltage levels can impose significant economic impacts for both electricity suppliers and customers. For the case where harmonic voltage levels are high, economic costs include damage to equipment and associated loss of production due to high voltage harmonic levels as well as the costs associated with mitigation of harmonic currents, for example, harmonic filters. In the alternate scenario, ie. the case where harmonic voltage levels are acceptable, considerable expense may be incurred mitigating harmonic currents unnecessarily due to lack of knowledge of harmonic levels and/or network capabilities. As such, there is considerable potential for industry to make large economic gains if harmonic voltage levels can be better understood. Using data collected as part of an ongoing long-term power quality monitoring project, this paper details the characteristics of voltage harmonic behaviour on Australia electricity distribution networks [ABSTRACT FROM AUTHOR]

In this paper, based on the equivalent circuit of spiral-shaped CPW resonators, a novel compact cascaded inhomogeneous coupled-line (CIHCL) with two tunable transmission zeros is proposed to replace the quarter-wavelength microstrip line of the conventional power divider (CPD). The modified power divider with CIHCL could achieve the same frequency responses of CPD and also realize controllable harmonic suppression with compact size. To verify the expected results, two power dividers with different harmonic suppression ratios are designed and one of them is fabricated to demonstrate the performances of the proposed power divider. The simulated and measured results illustrate that the return loss and isolation at center frequency 3 GHz are better than 25 dB and the insert loss is better than 0.4 dB. In addition, about 30 dB suppression for second and third harmonic is achieved. [ABSTRACT FROM AUTHOR]

In this paper, a new power divider (PD) is designed initially; then a new PD has been proposed by replacing the conventional transmission lines with rectangular-shaped and radial-shaped resonators. It results in the extra harmonics suppression with a miniaturized circuit size. The proposed PD has been analyzed using even-mode/odd-mode analysis. The designed PD shows a very good fractional bandwidth. In addition, the proposed PD is miniaturized 41% approximately. Also, seven harmonics are eliminated. Finally, PD was implemented and the experimental results illustrate a good agreement with simulation results. [ABSTRACT FROM AUTHOR]

This paper proposes a systematic approach for the development of electric machine windings with reduced magnetomotive force (MMF) space harmonic content. By identifying the levels and slot position angles in the winding function of an electric machine winding, the winding factor, the magnitudes of individual harmonic components and thus the MMF spectrum of a winding can be represented mathematically as functions of the levels and angles. With numerical optimization, these functions can act as the constraints and the objective function. A typical formulation is to limit the magnitudes of undesired harmonics and to maximize the winding factor of the working component. The result of the optimization is often a new winding layout with potentially unequally pitched slots and different turns for the coils within a phase, and reduced or even eliminated harmonic orders of design interest, while maintaining a reasonable winding factor. The mathematical representation and design approach is applicable to both distributed windings and fractional-slot concentrated windings (FSCWs), with no special requirements on the slot/pole combination and the number of layers. Two design examples, a mixed-layer distributed winding and a 24-slot, 22-pole double-layer FSCW, are shown to have improved electromagnetic performance with finite element simulations. [ABSTRACT FROM AUTHOR]

This paper presents a synchronous reference frame (SRF)-based power angle control (PAC) approach for a specific unified power quality conditioner (UPQC) arrangement, termed as UPQC-L for dual point of common coupling system under unbalanced source voltage condition. In contrast to a conventional configuration of UPQC, the static compensator (STATCOM) part is on left side of UPQC-L, while dynamic voltage restorer (DVR) is on the right side. The UPQC-L configuration is specifically adapted for protection of sensitive and critical load types from voltage disturbances. Along with its basic compensation capability of current harmonic compensation and voltage compensation, it efficiently handles reactive power demand from sensitive load. This is achieved with the introduction of PAC concept for effective sharing of reactive power between STATCOM and DVR. The extraction of instantaneous power angle faces difficulty with unbalanced voltage and UPQC-L configuration. Thus, the control algorithm for UPQC-L is designed based on SRF and numerical analysis approach with equal reactive power sharing phenomena by STATCOM and DVR of UPQC-L. UPQC-L with the proposed control approach is successfully implemented in MATLAB/SIMULINK (The Mathworks, Inc. USA) and verified experimentally for mitigation of voltage disturbances (such as sag/swell, unbalancing, and harmonics), current harmonics, and high-reactive power demand. [ABSTRACT FROM AUTHOR]

Now a day, distributed sources are emerging widely due to their advantages owing to renewable-based power generation. In this paper, a novel passive islanding method for the inverter-based grid-connected system is presented. This method can be suitably applied along with the conventional passive methods like under/over voltage and under/over frequency islanding techniques. Total harmonic distortion (THD) at the point of common coupling (PCC) is used to discriminate the islanding condition, and to safely disconnect the grid. This method has an advantage that it is able to discriminate non-detection zone (NDZ) when the local load matches the inverter output power. The results using MATLAB simulations and laboratory prototype have been presented. [ABSTRACT FROM PUBLISHER]

This paper presents the loss analysis of a dual-air-gap axial flux permanent magnet machine for a flywheel energy storage system. Losses in iron-core and permanent magnets caused by both space harmonics and time harmonics are respectively analysed using a three-dimensional finite element method. The effect of skew of magnets on machine losses is also taken into account. The analysis is validated by comparisons of calculated losses and measured values on a prototype. A solution to reduce eddy-current losses in the magnets for this machine is also presented. The eddy-current losses in the permanent magnets can be significantly lessened by both circumferential and radial segmentations. [ABSTRACT FROM AUTHOR]

In this paper, a low phase-noise millimeter-wave planar dual-port voltage-controlled oscillator (VCO) using a novel electronically tunable substrate integrated waveguide (SIW) resonator is proposed. The VCO operates in the Ka- and E-band simultaneously. At the fundamental-wave port, the VCO achieves a tuning rang of more than 120MHz by varying the varactor tuning voltage from 0 to 11V, spurious output less than −40 dBc, and a phase-noise of −114.7 dBc/Hz at 1MHz offset from 32 GHz carrier frequency. Meanwhile, at the harmonic port, a tuning rang of more than 240MHz around 64GHz carrier frequency is achieved. The measured output power varies from 6.04 to 8.75 dBm and 7.2 to 9.46 dBm within the fundamental-wave and second harmonic tuning ranges, respectively. This type of low phase-noise planar dual-port VCO is very suitable for millimeter-wave applications in high stable phase-locked sources or FMCW radars. [ABSTRACT FROM PUBLISHER]

In traditional Z-source inverter (ZSI) fed induction motor drives, the Z-source capacitor voltage and the motor terminal voltage are controlled by the shoot-through duty ratio and the modulation index, respectively. Modified voltage space vector has been proposed to improve motor terminal voltage control with effective DC boost in the DC link. For the same shootthrough duty ratio, modified voltage space vector provides better voltage boost in the DC link with reduced harmonics in the load side than the traditional voltage space vector. This paper presents an integrated control technique to minimise the electromagnetic torque ripples in the rotor of the ZSI-fed induction motor drives using modified voltage space vector. To improve the stability of the overall drive system, the motor terminal voltage alone is sensed instead of sensing the Z-source capacitor voltage and motor terminal voltage independently. This provides a single-stage controller for motor drive systems. The proposed induction motor drive system provides a better ride-through capability during voltage sags, better line harmonic profile, and minimisation of the torque ripples in the rotor. The proposed control technique is simulated using MATLAB/Simulink software, and analysis and experimental results have been presented to validate them. [ABSTRACT FROM AUTHOR]

This paper presents the hybrid phase-shifted carrier (PSC) modulation for cascaded voltage source inverters, investigates their performance characteristics, and provides a comparison with the standard pulse-width modulation (PWM) methods. The proposed PWM combines the features of fundamental frequency PWM and high-frequency PSC-PWM in power conversion, and resolves the contradiction between high frequency and accuracy in a digital control scheme. The proposed PWM is developed based on PWM base generator and hybrid PWM control algorithm, and it is implemented using TMS320 F2407 DSP processor and Xilinx XC95108 CPLD controller, respectively. The main characteristic of this hybrid modulation is the reduction in switching losses, effectively improving harmonic performance, and solving the problem of unequal voltage stress and current stress of power devices. The performance of this hybrid modulation is analysed and compared with the original strategies. Power losses, total harmonic distortion (THD), weighted THD and the normalised weighted THD are evaluated. Simulation and experimental results verify that the proposed PWM technique is superior to standard techniques. Finally, it is concluded that the proposed strategy is highly suited to inverters with high number of voltage levels. [ABSTRACT FROM AUTHOR]

In traditional Z-source inverter (ZSI) fed induction motor drives, the Z-source capacitor voltage and the motor terminal voltage are controlled by the shoot-through duty ratio and the modulation index, respectively. Modified voltage space vector has been proposed to improve motor terminal voltage control with effective DC boost in the DC link. For the same shootthrough duty ratio, modified voltage space vector provides better voltage boost in the DC link with reduced harmonics in the load side than the traditional voltage space vector. This paper presents an integrated control technique to minimise the electromagnetic torque ripples in the rotor of the ZSI-fed induction motor drives using modified voltage space vector. To improve the stability of the overall drive system, the motor terminal voltage alone is sensed instead of sensing the Z-source capacitor voltage and motor terminal voltage independently. This provides a single-stage controller for motor drive systems. The proposed induction motor drive system provides a better ride-through capability during voltage sags, better line harmonic profile, and minimisation of the torque ripples in the rotor. The proposed control technique is simulated using MATLAB/Simulink software, and analysis and experimental results have been presented to validate them. [ABSTRACT FROM AUTHOR]

This paper presents a novel harmonic-suppressed microstrip open-loop resonator bandpass filter with the different transmission line characteristic impedance of the feed line and open-loop resonator for wireless local area network (WLAN) application. To improve the stopband rejection of the filter, the dumbbell-shape defected ground structure (DGS) are applied under the feed lines to suppress the harmonics and the equivalent parameters extraction formulations of double-dumbell-shaped DGSs are the first to proposed. The bandpass filter with center frequency of 2.44 GHz were designed and fabricated on a TLX substrate with thickness of 1 mm and dielectric constant of 2.55. Measurement results show the filter has a wide stopband characteristic with 30 dB attenuation up to 7.5 GHz and only has an –1.23 dB insertion loss while it is a little larger than the conventional one. The measured results are in good agreement with the simulated results. It can be widely used for WLAN application. [ABSTRACT FROM AUTHOR]

In this paper we show how it is possible to investigate the nuclear dynamics of simple molecular ions and molecules by looking at the high-order harmonic generation spectra they emit in the presence of a laser field. In particular we investigate two different effects: the presence of sidebands in the emitted spectra around the usual odd harmonics and an isotopic effect which affects the height of the plateau lines. We further study the advantages and the limitations of the semiclassical approach. [ABSTRACT FROM AUTHOR]

In this paper, we study the effect of harmonics of phase-shifted square-wave corrugations on the different stopbands of a corrugated parallel-plate waveguide supporting TM waves. The stopbands are characterized by simultaneous occurrence of first-order and higher-order Bragg interactions. Coupled mode equations of two or four modes are derived via the method of multiple scales. Above cutoff of a higher-order mode, it is found that three resonance conditions must be satisfied: a first-order Bragg condition for the higher-order mode and a higher-order Bragg condition for the dominant TM10 mode, and a third condition coupling the two modes. A design of a multiple stopband filter for interference suppression in UWB applications is given showing all stopbands above cutoff of the TM10 and higher-order modes up to TM50 by including effects of higher harmonics of the structure. The bandwidth of each stopband is controllable by varying the phase shift between corrugations on the two walls of the waveguide. The fundamental matrix method is used to solve the filtering problem numerically. [ABSTRACT FROM AUTHOR]

Harmonic suppressed active antenna integrated with power amplifier yields improved efficiency, higher output power and reduced harmonic radiation from transmitter front end. This paper presents different harmonic suppression techniques of active antenna integrated with power amplifier. This paper also proposes and demonstrates novel PBG engineered structures to suppress higher order harmonics of integrated active antenna. [ABSTRACT FROM AUTHOR]

In this paper, the mathematic model of Colpitts oscillator is illustrated and the expressions for the main circuit parameters are derived, with which chaotic oscillation can be established. Experimental researches were conducted on the implementations of chaotic Colpitts oscillator using two types of broadband bipolar junction transistors (BJTs), namely BFG520XR and BFG425W with corresponding threshold frequency of 9 GHz and 25 GHz. Experimental results indicate that, chaotic oscillation can be obtained in a wide frequency regime in microwave band. When using BFG425W in the Colpitts circuit, the highest fundamental frequency of the chaotic oscillation can be about 1.6 GHz, and the harmonics observed with Agilent PSA/ESA Spectrum Analyzer are noticeable as far as 12 GHz, which is the highest one reported so far. Several typical applications using such chaotic oscillators are also presented at the end of this paper. [ABSTRACT FROM AUTHOR]

The analysis of multiconductor transmission lines with arbitrary nonlinear terminations in the frequency domain is presented in this paper. The transmission line system can either be modeled by the R, L, G, G matrix for quasi-static approximation, or represented by the multi-port 5-parameter for the full-wave consideration. The time-domain responses for both of the two transmission line formulations in nonlinear loading then are acquired by using the harmonic balance technique with the periodic pulse excitation in a few iteration processes. Numerical examples show the availability and versatile features of the proposed approach with confirmations of the literature and the commercial software results. [ABSTRACT FROM AUTHOR]

In the title paper, Li et al. have presented a scheme for filter-less photonic millimetre-wave (mm-wave) generation based on two polarization multiplexed parallel dual-parallel Mach-Zehnder modulators (DP-MZMs). For frequency octo-tupling, all the harmonics are suppressed except those of order 4l, where l is the integer. The carrier is then suppressed by the polarization multiplexing technique, which is the principal innovative step in their design. Frequency 12-tupling and 16-tupling is also described following a similar method. The two DP-MZM are similarly driven and provide identical outputs for the same RF modulation indices. Consequently, a demerit of their design is the requirement to apply two different RF signal modulation indexes in a particular range and set the polarizer to a precise angle which depends on the pair of modulation indices used in order to suppress the unwanted harmonics (e.g. the carrier) without simultaneously suppressing the wanted harmonics. The aim of this comment is to show that, an adjustment of the RF drive phases with a fixed polarizer angle with the design presented by Li, all harmonics can be suppressed except those of order4l, where l is an odd integer. Hence, a filter-less frequency octo-tupling can be generated whose performance is not limited by the careful adjustment of the RF drive signal, rather it can be operated for a wide range of modulation indexes (m ~ 2.5 → 7.5). If the modulation index is adjusted to suppress 4th harmonics, then the design can be used to perform frequency 24-tupling. Since, the carrier is suppressed by design in the modified architecture, the strict requirement to adjust the RF drive (and polarizer angle) can be avoided without any significant change to the circuit complexity. [ABSTRACT FROM AUTHOR]

Under investigation in this paper is a (2+1)-dimensional Gross-Pitaevskii equation with timevarying trapping potential, which describes the dynamics of the (2+1)-dimensional Bose-Einstein condensate. Employing the Hirota method and symbolic computation, we obtain the dark onesoliton, two-soliton, three-soliton, breather-wave and rouge-wave solutions, respectively. We graphically study the dark solitons with the time-varying harmonic potential and scaled scattering length. Parallel and period solitons are observed.Weobtain thatwhen the external trapping potential increases with time, amplitudes of the dark solitons increase and widths of those solitons become narrower; when the external trapping potential is a periodic function, amplitudes and widths of the dark solitons periodically change. Decrease in the scaled scattering length leads to the narrower solitons' widths, but does not affect the solitons' amplitudes. Breather waves and rouge waves are also displayed: Rouge waves emerge when the period of the breather waves go to the infinity. [ABSTRACT FROM AUTHOR]

A new fault location numerical algorithm based on terminal data and derived in time domain is presented. The fault location and its nature (arcing or arcless fault) are estimated using Least Error Squares Technique. In the paper, the arc, occurring on the fault point, is included into the problem consideration. The algorithm is derived for the case of a three-phase symmetrical fault. The results of the algorithm testing through computer simulation and under laboratory conditions are given. The influence of higher-order harmonics is investigated and presented. [ABSTRACT FROM AUTHOR]

Various attempts have been made for the selective reduction of harmonies in the output of AC/AC converters. However, when some harmonics are reduced other harmonic amplitudes increase. Thus, to reduce the harmful effects of these harmonics on other equipment operating on the same line, it may be necessary to use filters. A suitable type of filter depending on the line inductance for such cases is suggested in this paper. Experimental results are also presented. [ABSTRACT FROM AUTHOR]

In order to obtain an analytical solution of the step-recovery diode as a harmonic multiplier, various models of the diode have been used by several authors without sufficient explanation. This paper examines and compares the properties of these models by taking as a reference Kotzebue's experimentally verified model. An improvement of the 'resistive' model is also put forward. [ABSTRACT FROM AUTHOR]

In a permanent magnet synchronous motor (PMSM) control system, usually, the phase voltage instruction is limited independently to prevent a three-phase pulse width modulation (PWM) wave from overflowing. This method decreases the efficiency of the bus voltage and causes voltage vector direction errors. To solve these problems, we propose a harmonic injection sinusoidal pulse-width modulation (SPWM). This method uses harmonic injected sinusoidal PWM to improve the utilisation ratio of the bus voltage, and consequently improve system performance. In this paper, we analyse the problem in terms of potential difference. The simulation results show that the proposed method can increase the utilisation ratio of the bus voltage up to 15.4%, and the voltage vector mode obtained with the proposed algorithm is larger than that obtained with the conventional one. The method with harmonic injection consequently improves current response, without affecting voltage vector accuracy. The experiment results validate the proposed method. [ABSTRACT FROM PUBLISHER]

The harmonious appearance in multilevel inverter output voltage is more for the case of unequal DC sources. In this paper, a hybrid technique incorporating fuzzy inference system (FIS) and artificial bee's colony (ABC) algorithm is proposed. FIS is a rule-based artificial intelligent technique which is used for generating the data set in terms of switching angle, harmonic voltage and harmonic distortion. The data set is generated as per the behaviour of the multilevel inverter without using any harmonic elimination technique. In the generated data set, the switching angle and the harmonic voltage are categorised as SMALL, MEDIUM and LARGE. Then, the ABC algorithm is used to optimise the selection of switching angles from the training data set. The performance of the proposed hybrid technique is tested on a 7-level cascade H-bridge inverter for different voltage levels of unequal DC sources using MATLAB/SIMULINK platform. The effectiveness and superiority of the proposed technique is evaluated by comparing the reduction capacity of total harmonic distortion for different voltage levels of unequal DC sources with particle swarm optimisation (PSO) algorithm and fuzzy-PSO algorithm. [ABSTRACT FROM AUTHOR]

A compact electronically tunable dual-bandpass filter (BPF) with harmonic suppression is investigated in this paper. The BPF is composed of a step-impedance resonator, aT-stub with a varactor diode and a filtering network. The second passband can be independently tuned by varying the bias voltage across the varactor, whereas the first passband is fixed. The proposed filter exhibits wide stopband due to the introduction of the filtering network suppressing harmonics. A prototype of a tunable dual-band BPF, in which the second passband is tuned from 1.58 to 2.21?GHz and the first passband is fixed at 0.98?GHz, is designed and fabricated. The simulated and measured results are in good agreement with each other. [ABSTRACT FROM PUBLISHER]

Renewable energy sources (RES) are rapidly gaining popularity for sustainable power generation, they being less polluting and using readily available resources. This paper presents the modelling, control, and design analysis of a single-stage, three-phase RES-based distributed generation system where the grid-interfacing inverter is controlled to perform multi-functions by simultaneously incorporating active power filter (APF) functionality. The RES is connected to the DC-side of the voltage source inverter for interfacing with the grid. The inverter is utilized as power converter to inject the power generated from the RES to the PCC and shunt APF to compensate load current harmonics, load reactive power demand, and load current imbalance under distorted supply voltage conditions. Both these functions may be accomplished either individually or simultaneously. Thus, the designed controller either regulates the power flow between the RES and the grid or works as an APF or performs both the functions simultaneously. Simulation in MATAB and experimentation using DSP is carried out to verify the operation and the control principle. [ABSTRACT FROM AUTHOR]

Distributors need to allocate a maximum allowed level of harmonic current to medium-voltage customers to keep voltage distortion acceptable. The paper describes a new approach, based on the concept of voltage droop, requiring much less calculation and data than required by the present approach based on an IEC technical report. The discrepancy between the new method and the present is studied by comparing some carefully selected scenarios. It is shown that the proposed method gives results within 20% of the standards-based approach which makes it a very attractive alternative for harmonic allocation. [ABSTRACT FROM AUTHOR]

In this paper, a miniaturized Wilkinson power divider using a novel technique fornth harmonic suppression is presented. In this technique, a novel low-pass filter (LPF) is inserted into each quarter-wavelength transmission line of the conventional Wilkinson power divider and open stubs are used at each port. For verification, the proposed 1 GHz power divider and the miniaturized LPF are fabricated and measured. The presented structure not only impressively suppresses the harmonics (2nd–12th) with high levels of attenuation, but also significantly reduces the size over 71% of the conventional one. The overall size of the fabricated power divider is only 14.1 mm × 18.2 mm (0.06λg × 0.08λg). [ABSTRACT FROM AUTHOR]

A novel dual-frequency microwave rectifier that operates at 2.45 GHz alone, 5.8 GHz alone, or their combination has been developed in this paper. It is the first approach to microwave rectifying for a situation of the incoherent microwave power combination. We focused on the two primary components, i.e. the regulation of impedance matching and the recycling of the second harmonics. A quarter-wave short-ended microstrip line at 5.8 GHz is shunted at the input of the rectifier to enhance the impedance matching at 2.45 GHz. A microstrip line band-stop filter (BSF) and a quarter-wave short-ended microstrip line are introduced to improve the recycling of the second harmonics. The measured microwave to DC (MW-DC) conversion efficiencies are 57.5, 46.5, and 40.7% at 2.45, 5.8 GHz, and their combination, respectively, with an input microwave power at 17 dBm. It may be applied to a dual-frequency microwave power wireless transmission system. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel capacitor-based coupling scheme for realizing both harmonic-suppressed and miniaturized microstrip bandpass filters. The proposed coupling scheme employs lumped-/distributed-capacitors to provide the desired coupling strength between the resonance elements instead of traditional parallel-coupled lines. Certain coupling regions are replaced by coupling points resulting in high freedom degree of the filter topologies. Thus, the filter structure can be effectively miniaturized by meandering microstrip lines. To investigate the properties of the novel coupling scheme, an analytical equation is derived for describing the coupling coefficient variation vs. the positions of coupling points and the values of coupled-capacitors. Theoretical analysis indicates that several zero-voltage points can be chosen to suppress the harmonics, and the coupling coefficient can be easily tuned in a wide range by adjusting the capacitance of the coupled-capacitor. For demonstration, two sample filters are designed and fabricated. Simulation and experimental results agree well, validating the proposed methodologies. [ABSTRACT FROM PUBLISHER]