Improved Power-Series Expansion Method for the Analysis of Magnetic Deflection Yokes

We have proposed an improved power-series expansion method for the analysis of magnetic deflection yokes in a cathode-ray tube (CRT). The magnetic field is expanded to either of two different power-series formulations, depending on the radial position from the central axis of the deflection yoke. The coefficients of the power series are calculated by symbolically differentiating the magnetic field expressed by the surface magnetic charge method formulation. The boundary position for selecting either of the two formulations and the required highest order of the power series are determined by minimizing the summation of squared differences between the magnetic fields given by the proposed method and those given by the surface magnetic charge method at an off-center position. We compared the speed of the proposed method with the conventional surface magnetic charge method and evaluated the picture quality on a screen. We found that the calculation time for the misconvergence was reduced to 1/63 that of the conventional method, with an accuracy of [+ or -] 0.4 mm. Index Terms--CRT, deflection yokes, surface magnetic charge method.