A Soft-Switched Full-Bridge Single-Stage AC-to-DC Converter With Low-Line-Current Harmonic Distortion

A single-phase high-frequency transformer-isolated soft-switching single-stage ac-to-dc converter with low-line-current distortion is presented. The circuit configuration is obtained by integrating two discontinuous current mode (DCM) boost converters with a DCM full-bridge buck converter. The zero-voltage switching for the top switches is achieved automatically, whereas bottom switches are aided by zero-voltage transition circuits. The output voltage is regulated by duty-cycle control at constant switching frequency. The intervals of operation and steady-state analysis are presented. A systematic design procedure is presented with a 1-kW converter design example. PSPICE simulation and experimental results obtained from a 1-kW laboratory prototype are presented for a wide variation in line and load conditions.     

Electronically Tunable Microwave Bandstop Filters

The design procedures for varactor tuned bandstop filters are presented. A novel circuit technique for realizing bandstop filters with a symmetrical frequency response is described and explicit design formulas are presented. The physical design and experimental performance of a three cavity varactor tuned bandstop filter tunable around 4 GHz is presented. Experimental results are substantiated with computer analysis which includes the effects of varactor resistance.     

A study of the quadrifilar helix antenna for Global PositioningSystem (GPS) applications

An analytic model for computing the radiation properties of the quadrifilar helix volute antenna is discussed and various design considerations for GPS applications are presented. The effects of modifying the antenna length and diameter on the antenna amplitude and phase performance are presented, and using the antenna for dual-frequency operation is discussed. The effects of phase imbalances are presented and compared with measured pattern anomalies     

Active millimetre-wave aperture-coupled microstrip patch antennaarray

An active millimetre-wave aperture-coupled microstrip patch and four element array are presented. The design methodology is discussed and experimental measurements between 41 and 42 GHz are presented. The results presented should have useful applications in phased arrays and communication systems at EHF frequencies     

In-circuit test fixture [PCB testing]

Deficiencies in the conventional in-circuit fixture are presented. A novel fixture is described, and quantitative comparisons are presented. Crosstalk is decreased by 60 dB, and transmission-line matching is possible     

A recursive maximum likelihood algorithm for ARMA spectral estimation

A spectral estimation technique is presented for autoregressive moving-average (ARMA) processes. The technique is based on a parameter estimation technique known as the rec ursive maximum likelihood (RML) method. The recursive spectral estimation algorithm is presented and its asymptotic properties are discussed. Simulation results are presented to illustrate the performance of the estimator for various types of data.     

Numerical modeling of axisymmetric coaxial waveguidediscontinuities

Techniques for determining field behavior in the presence of coaxial-to-coaxial discontinuities are presented for axisymmetric geometries. A bilinear functional is formulated from which field solutions are obtained by way of the finite element method. An absorbing boundary condition is applied at the input and output port boundaries to reduce the size and complexity of the problem. An additional approach, mode matching, is outlined and presented as verification of finite element results. Two geometries are investigated, for which numerical results are presented. A comparative evaluation of the two techniques is included     

A mixed-signal approach for tuning continuous-time low-pass filters

A mixed-signal approach for tuning the bandwidth of continuous-time low-pass filters is presented. The tuning loop uses common circuit blocks (a data converter and digital filters). Simulation results are presented for a number of filters, and measured results are presented for tuning second-order and fourth-order filters.     

Predictive current control of voltage-source inverters

A new predictive current controller for a voltage-source inverter is presented in this paper. Practical aspects of realizing the new controller in a system with a digital signal processor (DSP) are considered. Delays introduced by measurements are considered and an improved algorithm with one-period prediction of current is presented. The controller was realized in an experimental system with DSP and field-programmable gate array circuits. Results of the simulations and experiments are presented.     

A novel unipolar converter for switched reluctance motor

A configuration of a unipolar power converter with improved switching performance suitable for switched-reluctance motor supply is presented. The switched-reluctance motor operation principle is presented and its ideal characteristics are considered. The proposed converter is described and its operation is analyzed. The converter characteristics are studied with the aid of computer simulation. Current control of the proposed converter is considered. A prototype converter has been built to verify the analysis results and to validate the simulation. The design procedure is presented and experimental results which confirm the analysis are given and discussed     

Amorphous silicon rich silicon nitride optical waveguides for high density integrated optics

Amorphous silicon rich silicon nitride optical waveguides clad in silica are presented as a high-index contrast platform for high-density integrated optics. Performance of different cross-sectional geometries have been measured and are presented with regards to bending loss and insertion loss. A sample double ring add-drop filter is presented.     

基于电调谐DOCCII的电流模式连续时间滤波器

本文提出了基于可变电流增益双输出CCII(DOCCII)的电流模式N阶低通滤波器和通用滤波器,并给出了N阶通用滤波器的一个通用表达式。所给出的滤波器参数可以通过DOCCII的可变电流增益因子独立调谐,并且结构简单,所有无源元件均接地,便于集成。     

Microprocessor-Based Control for Cigarette Makers

This paper describes a microprocessor-based on-machine controller for the regulation of cigarette weight. Control analysis is presented using the linearized system response to an impulse disturbance. A technique for driving an ac servomotor via on-time outputs is presented. Anti-windup features of the control algorithm are discussed. Results from an operating maker are presented.     

Zero-voltage switching technique in DC/DC converters

A novel resonant switch operating under the principle of zero-voltage switching is presented. The basic configurations of the voltage-mode resonant switches are presented. The circuit's operating principles are described using a voltage-mode quasi-resonant boost converter. DC analysis of the converter is carried out. A new family of voltage-mode quasi-resonant converters are derived, and several members of this family are presented. The duality relationship between the zero-current switching technique and the zero-voltage switching technique is derived. These two techniques are compared using an example showing the duality between a current-mode quasi-resonant Buck converter and a voltage-mode quasi-resonant boost converter. The similarities and differences of the voltage-mode quasi-resonant converters and the Class-E converters are discussed. A 5 MHz 50 V to 5 V flyback converter employing the zero-voltage switching technique has been implemented. Design considerations and experimental results of this circuit are presented     

The Traveling-Wave Divider/Combiner

A new kind of distributed power divider/combiner circuit for use in octave (or more) bandwidth microstrip power transistor amplifiers is presented. The design, characteristics and advantages are discussed. Experimental results on a four-way divider and divider/combiner are presented and compared with theory. First experimental results on a six-way traveling-wave divider (TWD) are also presented.     

Characteristics of sealed-off waveguide CO2lasers

Gain and output power of sealed-off waveguide CO2lasers are presented as a function of gas mixtures and total gas pressure. Experimental data on circular-bore and square-channel waveguide lasers are presented. Output power per unit length of 0.2 W/cm is achieved for both types of lasers in agreement with gas-discharge scaling laws which are presented. Saturation intensities as high as 24 kW/cm²are inferred from the data. The effects of the optical properties of the waveguide wall material on the waveguide losses are discussed and theoretical waveguide loss versus wavelength is presented for BeO, Al2O3, and fused silica.     

Taylor series based two-dimensional digital differentiators

A new type of Taylor series based 2-D finite difference approximation is presented, and it is shown that the coefficients of these approximations are not unique. Explicit formulas are presented for one of the possible sets of coefficients for an arbitrary order, by extending the previously presented 1-D approximations. These coefficients are implemented as maximally linear 2-D FIR digital differentiators, and their formulas are modified to narrow the inaccuracy regions on the resultant frequency responses, close to the Nyquist frequencies     

Modeling and simulation of mobile satellite propagation

Mobile satellite systems are subject to severe fading due to blockage of the line-of-sight (LOS) path by roadside vegetation. A thorough understanding of the fading effects is necessary for the design of a reliable land-mobile satellite system. Analytical and empirical models are presented for predicting fade statistics for vegetative shadowing of mobile satellite terminals. A software simulator for generating simulated fade data is also presented. A physical model relating physical path parameters to propagation model parameters is presented, and results using the model are shown     

Compensation for nonlinearities in third-generation mobile systems

A technique for compensating for nonlinear distortion in third-generation (3G) communication systems is presented. In these communication systems, the power-efficient amplification introduces both a widening of the transmitted pulse and nonlinear intersymbol interference. Novel structures are presented which are able to reduce simultaneously both unwanted effects. Examples are presented which show the performance of the compensators in typical digital channels     

Higher-order finite-difference schemes for electromagneticradiation, scattering, and penetration .1. Theory

Higher-order schemes for the finite-difference time-domain (FDTD) method are presented, in particular, a second-order-in-time, fourth-order-in-space method: FDTD(2,4). This method is compared to the original Yee (1966) FDTD scheme. One-dimensional update equations are presented, and the characteristics of the FDTD(2,4) scheme are investigated. Theoretical results for numerical stability and dispersion are presented, with numerical results for the latter, as well. The use of the perfectly matched layer for the FDTD(2,4) scheme is discussed, and numerical results are shown