Genichiro Ohta

Switched-beam slot sector antenna for WLAN applications

A small sector antenna using a switched-beam slot antenna is proposed. The switched-beam slot antenna has a main beam which is tilted to the direction along the slot plane, and its beam direction is inverted by changing the phase of the slot element excitation. We present a four-sector structure whose planar size of 10/spl times/10 mm/sup 2/ at 25 GHz and is suited to the antenna for a small card terminal. For the future, we are planning to fabricate and measure the four-slot structure and investigate the main beam control in the vertical plane for further performance improvement.

A planar sector antenna suitable for small WLAN card terminal

In this paper, a planar antenna and the 6-sector arrangement for a small card type mobile terminal used in the wireless local area network (WLAN) system are proposed. The radiation characteristics, particularly the tilted main beam in vertical plane and current distribution are calculated and discussed. We show that the 6-sector beams of half power width of 60 degrees are obtained by the proposed arrangement that is in a rectangular configuration of 10.6 mm /spl times/ 44 mm at 25 GHz band, and this is suited to a built-in antenna mounted on the edge of the card type mobile terminal like a PCMCIA card.

OFDM transmission diversity scheme for MMAC systems

OFDM (orthogonal frequency division multiplexing) is used in the MMAC (multimedia mobile access communication) systems using 5 GHz band systems as an effective solution under a multipass fading environment. Transmission space diversity techniques for OFDM have been reported. In order to improve the performance better, it is proposed to control the gain of each sub-carrier at the transmitter side using transmission space diversity. Then the receiver gets a constant received level at each sub-carrier. Using this scheme, the receiver improves the performance better. Moreover, concerning peak power reduction, it is proposed to control the bound of the maximum gain according to number of sub-carriers in each branch.