Compact Planar Multipole Antenna for Scalable Wide Beamwidth and Bandwidth Characteristics

This article proposes a concept of compact planar multipole antenna configured by multiple magnetic and electric dipoles as a single radiation element with a single signal excitation port. The proposed structure uses diverse orientations in magnetic field and electric coupling through segmented radiation conductors and ground vias. The uniqueness of multipole antenna can be emphasized by its compactness, wide beamwidth in both the E- and H-planes with a finite ground plane size, and wide impedance bandwidth characteristics. To verify the concept of multipole structure, four different types of antennas are proposed and analyzed. With a radiation element size of 0.33\lambda _{\mathrm {o}}\,\, \times 0.33\lambda _{\mathrm {o}} ( \lambda _{\mathrm {o}} for free-space wavelength) and a finite ground size of 1.1\lambda _{\mathrm {o}}\,\, \times 1.1\lambda _{\mathrm {o}} at 5.9 GHz, the half-power beamwidths (HPBWs) of 175° and 133° in both the E- and H-planes were measured, respectively. A wider bandwidth characteristic compared to previously reported wide beamwidth planar antennas was also achieved by one of the proposed structures. The measured 10 dB impedance bandwidth was about 13% with HPBWs of 111° and 160° in both the E- and H-planes, respectively. Also, the measured peak gains were better than 5.3 dBi for all structures with an excellent gain flatness at the operation band.