Electric fields and vector potentials of thin cylindrical antennas

The vector potential and elastic field generated by the current in a center-driven or parasitic dipole antenna that extends from z=-h to z=h are investigated for each of the several components of the current. These include sin k (h-|z|), sin k|z|-sin kh , cos kz-cos kh, and cos kz/2-cos kh /2. Of special interest are the interactions among the variously spaced elements in parallel, nonstaggered arrays. These depend on the mutual vector potentials. It is shown that at a radial distance ρ~ h and in the range -h⩽z⩽h, the vector potentials due to all four components become alike and have an approximately plane-wave form. Simple approximate formulas for the electric fields and vector potentials generated by each of the four distributions are derived and compared with the exact results. The application of the new formulas to large arrays is discussed