Syuichi Sekine

Antenna-selective transmit diversity technique for OFDM-based WLANs with dual-band printed antennas

An antenna-selective transmit diversity (ASTD) technique, applied to a PC card for an orthogonal frequency division multiplexing (OFDM)-based wireless local area network (WLAN) system, is presented. The PC card, which is based on IEEE 802.11 a/g, is equipped with dual-band printed antennas. The ASTD processing is implemented in the developed WLAN system, which has two antennas for transmit and receive modes. The effects of the ASTD technique on the TCP (transmission control protocol) throughput performance are experimentally evaluated. Measurement results with the PC card in an imitated office show that the TCP throughput is improved on both the 2.4 and 5.2 GHz bands under the conditions of an indoor radio propagation channel due to the ASTD technique. In particular, application of the ASTD technique to an access point (AP) achieves four times the average TCP throughput on the 5.2 GHz band.

Improvement of the radiation pattern by reducing the leakage current on the ground plane for antennas of PC terminals

In order to reduce the leakage current on the ground plane and improve the radiation pattern, we have proposed an antenna structure with parasitic elements. The validity of the simulated result is shown by comparison with the measurement. The proposed antenna is satisfied with the required bandwidth of IEEE 802.11b/g. Since the leakage current on the ground plane is reduced with the proposed antenna in comparison with the inverted-F antenna, the radiation pattern of vertical polarization in the horizontal plane is improved.

Radiation characteristics of modified H-shaped antenna with robustness against the environment around the antenna

In order to realize an antenna capable of operating without depending on the environment around the antenna, we have proposed a modified H-shaped antenna which has a unidirectional radiation pattern like a Yagi-Uda array. The antenna characteristics in the vicinity of the metal plate are calculated using the moment method, and the proposed antenna has little degradation of VSWR compared with a two-element Yagi-Uda array