Microstrip Magnetic Monopole and Dipole Antennas With High Directivity and a Horizontally Polarized Omnidirectional Pattern

Novel microstrip magnetic monopole and dipole antennas are proposed to achieve a high directivity along the elevation plane as well as a horizontally polarized omnidirectional pattern in the azimuth plane. The directivity of this microstrip magnetic monopole antenna is calculated by numerical integration; the results show that the directivity increases with the antenna length when the antenna resonates in the fundamental mode. However, simulation shows that the main beam is tilted away from the azimuth plane when the antenna length exceeds 2λ due to high-order resonant mode interference. A solution is provided to suppress the second resonant mode and retain the radiation peak in the azimuth direction. The peak gain of the microstrip magnetic monopole is increased to 7.2 dBi when the antenna length is approximately 3λ. A microstrip magnetic dipole antenna with an antenna length of 6λ is also designed to obtain a higher gain of 9.7 dBi. The impedance bandwidths of the microstrip magnetic monopole and dipole antennas are 6.5% (2.37-2.52 GHz) and 7.3% (2.35-2.53 GHz), respectively. The proposed antennas produce maximum radiation in the azimuth direction and have horizontally polarized omnidirectional patterns in the azimuth plane.