Dipoles, Slots, and Loops

Small resonant structures of dipoles, loops, and slots determine the current distribution and pattern of small antennas used alone or in arrays. Finite ground planes, cylinders, resonant loops, and corner reflectors modify the patterns of dipoles. Small or resonant loops produce dipole shaped patterns or can be twisted into a quadifilar helix for a unidirectional pattern. Slots cut into walls of waveguides, stripline, cylinders, or cones radiate dipole patterns analyzed as magnetic currents whose level of excitation is determined by the disturbance currents of wall currents. Combinations of slots with dipoles or loops shape the pattern.