In this letter, a reconfigurable radiation pattern antenna for multiple-input-multiple-output (MIMO) applications on mobile devices is proposed. The operating frequency band of the antenna is 5.15-5.35 GHz for a wireless local area network (WLAN) 802.11a service. Each antenna is composed of a loop-and-dipole structure, as well as two switches for the reconfigurable radiation pattern, to generate a beam in three different directions. The proposed antenna is designed to have an orthogonally directional radiation pattern with high isolation and a low-correlation coefficient in the MIMO environment.

In this paper, a dual-band antenna is proposed for the RF power harvester system as well as RFID tag. The proposed antenna operates as the passive and active RFID tag antenna in the UHF and microwave band, respectively. In addition, to charge the battery of an active RFID tag in the microwave band, it harvest the RF signal for tagging from the passive RFID tag antenna in the UHF band. The proposed antenna operates in the UHF band (917~923.5 MHz) and microwave band (2.4~2.45 GHz). In order to obtain the dual-band operation, the dipole structure and meander parasitic elements are proposed as the λ/2 and 1λ dipole antenna, respectively. The radiating dipole structure in the microwave band acts as the coupled feed for the meander parasitic elements in the UHF band. The impedance bandwidth (VSWR < 2) of the proposed antenna covers 917~923.5 MHz (UHF band) and 2.4~2.45 GHz (Microwave band). Measured total efficiencies are over 45 % in the UHF band and over 70 % in the microwave band. Peak gains are over 0.18 dBi and 2.8 dBi in the UHF and microwave band with an omni-directional radiation pattern, respectively.