Characteristic Impedance of Parallel Wires in Rectangular Troughs

The method of conformal transformation and the method of images are employed jointly to deduce the characteristic impedance of a balanced two-conductor transmission line and of a balanced three-conductor transmission line symmetrically surrounded by perfect, rectangular, grounded, conducting surfaces. It is assumed that 1, the wires are of circular cross section, of diameter small compared to the distance between them and small compared to the distance from the wire to any side of the surrounding surface, and 2, the wires are perfect conductors.