Wireless Lan (802.11a) Rf Receiver

The need to support broadband multimedia services over wireless infrastructure is driving the development of Wireless local area network(WLAN) and its applications. With the increasing popularity of WLAN, the portable devices such as smart phones, tablet PCs which not only transfer voice and multimedia data but also access internet wherever possible. With the huge demand of WLAN chipsets, the stress on lowering the volage supply, the power consumption and the cost, and increasing level of integration are driving forces. To satisfy this requirement, CMOS process technology is widely used in the circuits design now.A WLAN (IEEE 802.11) receiver is proposed and analyzed in this thesis. In this receiver, a zero-IF architecture has been used for high integration and low power consumption. It consists of low noise amplifier(LNA), down-converter mixer, variable gain amplifier(VGA) and channel selection low-pass filter. The receiver is implemented in SMIC 0.13 um CMOS process. The post simulation indicates it works at pure 1.2V power supply and the total current is 37mA. Noise figure is 4.01 dB, and the third input inter-modulation point is-3.39dBm at high gain mode.The first part of the thesis is the receiver system design. Some of the receiver's performance parameters and specifications based on IEEE 802.11a are defined from the system viewpoint including noise figure, linearity, gain, dynamic range, cut-off frequency. These specifications are distributed to each block design requirements for system optimization and module design.The following sections focus on the circuit design. A detailed analysis about the baseband including channel selection low-pass filter and VGA is presented. In order to increase the receiver dynamic and the trade-off about the noise and chip area, the VGA is distributed before and after the channel selection low-pass filter. A fully differential fourth-order Butterworth low-pass filter based on active-RC filter is disigned. It consists of two-stage cascade fully differential second-order Tow-Thomas filters. VGA consists of attenuation network and the fixed gain amplifiers with good linearity and low noise figure. A analog lowpass feedback solution and a current injection solution are proposed to solve the DC-offset problem in the zero-IF architecture.