Design and fabrication of pHEMT MMIC switches for IEEE 802.11.a/b/g WLAN applications

Abstract

The WLAN technology is capable of providing data service in a specific distinct area (about 100 m coverage), so called hot spot area, using some RF techniques without wired network. For example, the customers are able to access to the LAN services and the Internet by simply installing the WLAN card into the notebooks or PDAs. The WLAN service is able to provide both high data rate up to 54 Mbps and a walking pace mobility in both indoor and outdoor. Because of this performance, the WLAN service and its system have been extensively developed in the all over the world. The recent growth of WLAN is very impressive both in terms of the quantity of units deployed and the number of companies working on WLAN products. A large variety of WLAN cards operating in the 2.4-2.5 GHz (IEEE 802.11 b/g standard) and the 4.9-5.9 GHz (IEEE 802.11a standard) is on the market. The main market of WLAN is personal computer (PC) and personal digital assistant (PDA). In 2002, the PCI cards for PC and IEEE 802.11b are mostly occupied in the market. However, as of 2005, the market is gradually changing into modules for PC and multiband IEEE 802.11a/b/g system. For a multi-service system capable of more than two different services (i.e. data, voice, multimedia etc.), multiband antennas and switches are essential to select a specific service that is user oriented. For controlling the $R_x-$ and $T_x-signal$ flow in the multiband wireless LAN communication terminals, one of the most suitable MMIC components at front-end behind antenna is switching circuit. As state-of-the-art systems have become more complex, switches have emerged as key elements which significantly determine the overall terminal performance. In digital wireless LAN systems, switches are used for a great variety of functions, such as mode selection, band selection, power control and transmit/receive switching functions. Switching circuits can be implemented by using like MEMS, PIN diodes and FETs. Currently, GaAs-ba...