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This paper proposes an oppositely coupled varactor pair and reports the measured results for applying to a test digitally controlled oscillator (DCO). The pair exploits the differences between the accumulation region capacitance and inversion region capacitance of pMOS varactors. The novel varactor pairs provide much smaller switchable capacitances than those of other approaches, and hence, the test DCO for verifying the property of the pair achieves the high-frequency resolution. The pairs and test DCO are implemented in a 0.18-μm CMOS process. The switchable discrete capacitance of 32 aF is obtained by using the novel varactor pairs, and the test DCO has a frequency resolution of about 110 kHz at 5.8 GHz. Furthermore, ΔC of 4-aF and 14-kHz frequency resolution can be obtained through the dithering processes. The test DCO achieves a low phase noise of -117.6 dBc/Hz at 1-MHz offset from 5.8 GHz.

A linear induction motor (LIM) with a cage-type secondary has contact resistances between side-bars and secondary conductors due to its own manufacturing process of welding. The finite-element analysis considering the equivalent circuit of the secondary winding is carried out to present the effect of the contact resistance in the LIM. As a result, thrust, normal force, the primary phase current, and the secondary conductor currents of the motor are analyzed for the various contact resistances.

Most single-phase brushless DC (BLDC) motors have unequal air gaps to eliminate the dead point where the developed torque value is zero. These unequal air gaps deteriorate the motor characteristics in cogging torque. Thus in this paper a new topology of the unequal air gaps is proposed to solve this problem. As a result, it is proved by the finite element analysis and experimental results that the proposed air gap topology is very effective in reducing the cogging torque.

In this paper, we discuss the analysis for the dynamic characteristics of a single-sided linear induction motor (SLIM) having the joints in the secondary conductor and the back-iron. The time-stepping finite element method and the moving mesh techniques are used for the simulation. The gradients of the electric scalar potential in the jointed secondary conductors and back-irons are defined for the eddy current analysis. The simulation results show that the junction between the secondary conductors creates a discontinuity of the eddy current and causes fluctuations of the thrust and the normal force.

This paper presents the finite element analysis for the dynamic characteristics of an inverter-fed permanent magnet linear synchronous motor (PMLSM) having the conductive sheet secondary. The time-stepping finite element method and the moving mesh technique are used for the simulation. The eddy currents in the secondary aluminum sheet and solid back-iron are taken into account in the electromagnetic field analysis.

The real brushless DC motor has different permanent magnet pole magnetization levels due to the influence of the magnetizer geometry. Therefore, this paper discusses the influence of change in the magnetic parameter on brushless DC motor performances. As a result, the unbalanced magnetic force acting on the rotor, cogging torque and torque ripple are examined for spindle motor with unsymmetric magnetization distribution.

This paper describes the effect of eddy currents generated in the rotor steel shell of an exterior-rotor type permanent magnet brushless DC motor of which the rotor is revolving at a high speed. A two dimensional time-stepped finite element method is used to analyze the electromagnetic field and compute motor performance. The conductivity of the rotor steel shell is modified to consider the transverse edge effect. As a result, the effect of eddy currents is shown by comparing the analysis results between when the proposed method is used and when the method it is not.

This paper discusses the phenomena of the axially nonuniform distribution of magnetic flux densities and losses in a three-phase squirrel cage induction motor of which the rotor bars are skewed. A 2-D complex finite element method, taking account of the effects of the skewed rotor bars, is utilized for the analysis of characteristics such as copper and iron losses and the loss distributions are examined. The summing up values of nonuniform losses resulted from the finite element analysis are compared with measurements.

This paper presents a method to analyze radial force densities acting on each stator tooth of an induction motor with skewed slots. A two-dimensional finite element method is used for electromagnetic field analysis of an induction motor, and skew effects are considered by coupling several disks cut by planes perpendicular to the shaft. Radial force densities as a source of vibration are calculated along the surface elements of each stator tooth and its time harmonics are examined by discrete Fourier decomposition.

The optimization of the design variables of a single-sided linear induction motor (SLIM) using the finite-element method (FEM) and the sequential unconstrained minimization technique (SUMT) is presented. Thrust is taken as an objective function in order to maximize thrust under a constant current drive, and seven independent design variables and nine constraints are chosen. As a result, pole pitch/airgap and pole pitch/aluminum depth for the best design are determined. Thrust is increased by 30% under a constant current of 12 A, so that the input current can be reduced to 10.5 A for necessary starting thrust because thrust is proportional to I/sup 2/. >