Dual-band LNA with notch filter for WLAN and WiMAX

• Main Authors: Hsu, Pei-Hsiang, 徐培翔
• Other Authors: Kuo, Chien-Nan
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/41610311773190299481

碩士 === 國立交通大學 === 電機學院碩士在職專班電子與光電組 === 97 === Because of the advances of wireless communications in recent years, utilization of radio frequency bands has become more and more frequent. As a result, some issues arise gradually, especially the problem of signal interference. Therefore, it is necessary to avoid loss of system sensitivity to interferences by careful receiver front-end circuitry design. Usually band-pass filter (BPF) is used in receiver front-end to suppress interfering signal strength. Also, LNA provides gain control to avoid loss of sensitivity due to interferences. For multi-band and multi-mode integrated systems, adjacent band interference is another server problem that needs to be addressed. For example, in Taiwan, the already popular WLAN (2.4~2.5GHz) and emerging WiMAX (2.5~2.7GHz), because of the close and almost overlapping frequency bands, it is clear that the signal interference problem cannot not be handled by only the BPF. This kind of issues point out new research directions. In this thesis, active notch filter is proposed to resolve issues caused by two signals that are too close in frequency. Also, varactor is utilized to adjust the LC tank such that WLAN or WiMAX signal can be obtained at RF output.