Capacitance of Narrow Strip in Tall Rectangular Cross-section Envelope

The 2D capacitance of a thin (zero thickness) strip in the center of rectangular cross section grounded envelope can be evaluated using the formulas for 2D “corner” geometric capacitances or permeances. If the width of the strip is larger than the height of the envelope the known corner capacitance for infinitely wide strip can be used. Because the exact solution for narrow strip contains difficult to evaluate series simpler approximate formulas were proposed for particular cases and interpolation is suggested for intermediate value of the parameters. In the paper, using conformal mapping and numerical conformal mapping, a new more exact approximate formula is proposed which significantly enlarge the application domain, up to infinitely tall envelope.