In the radiation pattern of an antenna, an electromagnetic wave that (a) predominates in the far-field region, (b) has a wavefront that is essentially in a Flat plane, and (c) has wavefront planes that are parallel, i.e., the wave surfaces of constant phase are infinite parallel planes normal to the direction of propagation. Note 1: A uniform plane-polarized electromagnetic wave, i.e., a plane wave, propagating in free space or in a dielectric propagation medium, has a characteristic impedance magnitude, i.e., the ratio of the electric and magnetic field strengths, given by the relation Z = E/H where E and H(a) are the electric field and magnetic field strengths, (b) are orthogonal, and (c) are in a direction perpendicular to the direction of propagation, i.e., are perpendicular to the Poynting vector. In free space, the characteristic impedance of a plane electromagnetic wave is 377 ohms. From Maxwell's equations, the characteristic impedance of a plane wave in a linear,...