Figure 3

Evolution of magnetic-current antennas. The left column, middle column, and the right column are the names, structure diagrams, and corresponding radiation patterns, respectively. The blue arrows indicate the equivalent magnetic currents. In the simulations, the ground is set to infinite to clearly show performances of radiation patterns and avoid the influence of ground edges. Antenna 1, i.e., single-magnetic-current antenna, has an open edge and three short edges. The slot on open edge can be equivalent to a magnetic current and generate a dipole-like radiation pattern. Antenna 2 is composed of two single-magnetic-current antennas, which are fed with equal magnitude and phase. Two inversed equivalent magnetic currents are generated on the two open edges and the binary magnetic-current array has a bidirectional radiation pattern. Antenna 3 with two open edges and two short edges is a simplified structure of Antenna 2. Antenna 3 has only one feed and the impedance can be matched by adjusting the feed position. Antenna 4 is a practical antenna proposed in this paper. The sheets on short edges of Antenna 3 are replaced with metal grounded holes and two slots are etched on top patch to excite two binary magnetic-current modes and increase the operational frequency band.