Radio frequency identification (RFID) is rapidly developing technology which is widely adopted for various data collection applications such as warehouse and retail item management . Currently, several frequency bands have been assigned to RFID applications, such as 125 kHz, 13.56 MHz, 840∼960 MHz, 2.45GHz, and 5.8 GHz. The Microwave RFID band 2.45 GHz is allocated around the frequency range from 2.4GHz to 2.4835 GHz. Compared to the UHF RFID systems around 900 MHz, the 2.45 GHz systems have the advantages of compactness, flexibility, and maneuverability for the item management applications. Different from antenna designs for fixed reader, the antenna design in an RFID handheld reader should fulfill several unique requirements, such as high gain, high front-to-back ratio, and asymmetric radiation beamwidth on two orthogonal cut planes.