| 摘要 |
A circular array of equally spaced, interleaved, reference elecrodes or pole pieces are arranged about the center of the array for producing an electric or magnetic field in which the resultant vector representing the maximum field strength rotates as a polyphase current or voltage source is successively applied to successive ones of the electrodes or pole pieces. In a preferred embodiment, each of the electrodes is uniquely and generally crescent shaped such that along any radius from the center of the array passing through a given electrode, the radial width of the electrode varies in proportion to the sine of Ax theta where A is an arbitrary constant and theta is the azimuthal angle of the radius as measured from the initial end of the electrode. The radial cross-section ratio may be achieved by varying the width alone, varying the elevation alone, or by a combination of the two. So arranged, the inner and outer edges of each electrode of constant elevation conform substantially to the curves <IMAGE> <IMAGE> where router is the radial distance from the center of the array to the outer edge of the electrode at any angle theta within the arc subtended by the electrode (O</= theta </= pi ); rinner is the radial distance from the center of the array to the inner edge of the electrode at any angle theta within the arc subtended by the electrode (O</= theta </= pi ); Rmin is the radial distance from the center of the array to both curves at theta =0; rmax is the radial distance from the center of the array to both curves at theta = pi ; theta is the azimuthal angle to a given point, measured in radians; d is a parameter which determines the maximum width of the electrode.
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