Design Of A Fully-Integrated CMOS Transmitter For802.11b WLAN

IEEE802.11b standards is a typical representative of the wireless LAN applications,which is used widely and developed rapidly. With persistent decrease in the feature size,CMOS technology is capable of enabling such a low-cost implementation ofradio-frequency transceivers for WLANs.This paper focus on research and design of a fully-integrated2.4GHz CMOStransmitter for802.11b WLAN. Using direct-conversion structure, transmitter avoidedImage Rejection. The main work covers the design flow of system parameters, theselection of the system architecture, the circuit design, layout design and so on. Thetransmitter contains of a active low-pass filter, up-mixers, Class AB power amplifier,baseband amplifier, orthogonal prescaler, bandgap and so on.Many efforts are focused on the design of Class AB Power Amplifier, which has atwo-stage structure. This paper puts forward a kind of design methodology abouttwo-stage Class AB Power Amplifier and gives feasible design flow. The two stageamplifiers both take linearization method. Driver stage is Class-A linear amplifier, whichimproves its linearity by using Class-A amplifier and Class-C amplifier’stransconductance compensation. Output stage is Class-AB amplifier, whose operatingpoint is optimized basing on the strong-to-weak nonlinear model of CMOS transistor. Sooutput stage also has good linearity. The simulation results show that the maximum outputpower of the transmitter is up to16dBm, and PAE of the Power Amplifier reaches19%.The double-balanced Gilbert up-conversion Mixer eliminates carrier leakage and increasesits linearity by using source-port negative feedback. This paper designs a fifth-orderButterworth low-pass filter, which not only shows the processes of the design offull-integrated active filters that based on signal flow graph, but also verifies the validityand correctness of the given method.After the completion of circuit and layout design, the transmitter is fabricated inSMIC0.18RF-CMOS process. The simulation results show that the transmitter is capableto put out QPSK modulated signal and its output signal meets the requirements of802.11bstandards. The maximum output power of the transmitter is up to16dBm and116mA current is exhausted.