Planar antennas, including microstrip and printed antennas and other types of antennas that arc flat in appearance and have a low profile, have recently received much attention for application in cellular communication systems, such as the global system for mobile communication (GSM: 890/960 MHz), the digital communication system (DCS: 1710-1880MHz), the personal communication system (PCS: 1850-1990MHz), the universal mobile telecommunication system (UMTS: 1920-2170MHz), and wireless local area networks (WLANs) in the 2.4 GHz (2400-2484MHz) and 5.2GHz (5l50-5350MHz) bands. Many novel designs of planar antennas for related applications such as internal mobile phone antennas, base-station antennas, WLAN. or Bluetooth antennas, and so on, have been reported very recently, especially since the year 2000.