Takahiro Sekiguchi

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.

Development of a PC card using planar antennas for wireless LAN on 2.4/5 GHz bands

We have developed a wireless LAN PC card for 2.4 GHz and 5 GHz dual-band operation using printed planar antennas, and evaluated its throughput performance. The planar antennas, which combine an inverted-F antenna with an inverted-L antenna, can realize a dual-band at low cost in a limited integrated area on the PC card. The radio propagation performance was evaluated in a shielded room which is modeled after an office. In the 2.4 GHz band, operation is stable and independent of the deployed position and the direction of a laptop PC with the PC card. On the other hand, in the 5 GHz band, although the performance is affected by surrounding objects and antenna directivity, the PC card with the printed antennas can realize as high a throughput as one with external omnidirectional antennas.

A 1.2V 0.2-to-6.3GHz Transceiver with Less Than -29.5dB EVM@-3dBm and a Choke/Coil-Less Pre-Power Amplifier

1.2 V 0.2-to-6.3 GHz transceiver for a multimode radio is fabricated in a 0.13 mum CMOS technology is proposed. The transmitter achieves EVM of less than -29.5 dB at -3 dBm output from 0.2 to 7.2 GHz while consuming 69 mW, where the modulation scheme used is equivalent to 802.11a, 54Mb/s mode. Without any explicit matching components, S22 and S11 are kept less than -9.5 dB and -9.2 dB, respectively, over the frequency range from 0.1 to 6.3 GHz. To achieve wideband output matching, a parallel combination of a common-source amplifier and a source-follower buffer is used. This structure copes with both 50 Omega output resistance, and small output capacitance. The choke in the pre-power-amplifier (PPA) is also eliminated by adopting a push-pull amplifier and by using a modified envelope signal injection biasing scheme. The PPA achieves OP 1dB of 6 dBm, which corresponds to almost the rail-to- rail swing for 1.2 V power supply.

A 0.13/spl mu/m CMOS 5GHz Fully Integrated 2x3 MIMO Transceiver IC with over 40dB Isolation

A 5 GHz MIMO direct-conversion transceiver composed of 2 transmitters (TXs) and 3 receivers (RXs) is fabricated with 0.13 mum CMOS technology. Die size is 4.56 mm times 7.7 mm. For driving 10 GHz LO signal lines of 5 mm length for both TXs and RXs, inductor-less low-power LO repeaters are equipped in individual LO paths. A linearized RF variable gain amplifier is proposed for low power operation. Isolation of over 40 dB is obtained by equipping separate GNDs on both the MIMO IC and the circuit board. This results in negligible degradation of EVM. TX EVM of over -31 dB is obtained at -8.6 dBm for 2 TX mode when external LO of 10 GHz is applied. The 3 RXs and 2 TXs with LO paths dissipate 703 mW and 412 mW from 1.5 V, respectively.