Publication: IEICE TRANSACTIONS on Communications Publication Date: 2010/10/01 Vol. E93-BNo. 10pp. 2658-2661 Type of Manuscript: Special Section LETTER (Special Section on Advanced Technologies in Antennas and Propagation in Conjunction with Main Topics of ISAP2009) Category: Antennas Keyword: microstrip antenna, circular polarization, coupled feed, ring resonator,