Study On 5GHz RF Receiver Front-End Based On Silicon Germanium Technology

Radio frequency IC design is beginning to move into the system-on-a-chip (SoC) solution era. The merits of extremely low cost and high integration naturally make direct down-conversion (Zero IF) architecture the choice of solution for single-chip RF transceiver ICs, particularly for U-NII (Unlicensed National Information Infrastructure) band applications, such as high-speed wireless local area networks (WLANs,502.11a). Rapid technology advancements in IC technologies for RF IC applications greatly improve the quality of passive IC components; therefore open the door to monolithic designs for more RF wireless applications. Yet in practical designs, some traditional drawbacks, such as second-order distortion, flicker noise and DC-offset contamination from self-mixing, have strong impact on RF transceiver sensitivity level, particularly in direct down-conversion transceiver architectures. These adverse phenomena are inherent to direct conversion from RF to base band and become an interesting research topic in RFIC designs.Silicon Germanium (SiGe) BiCMOS technology represents one possible solution to this problem. The SiGe BiCMOS process has the potential for low cost since it leverages mature Si process technologies and can use existing Si fabrication infrastructure. SiGe BiCMOS processes offer excellent high frequency performance through the use of SiGe hetero-junction bipolar transistors (HBTs), while coexisting Si CMOS offers compatibility with digital circuitry for high-level SoC integration.The work presented in this thesis focuses on the development of a SiGe RFIC front-end for operation in the U-NII bands. A low noise amplifier (LNA) and a active x2 sub-harmonic mixer (SHM) have been designed and simulated.The LNA designs use a single-stage, cascoded topology. The input ports are impedance matched using inductive emitter degeneration through bond wires to ground. The LNA uses a series inductor output match. Gain, isolation, match, linearity and noise figure (NF) were used to characterize the performance of the LNAs in the 5 - 6 GHz frequency band. The SHM is an active, double-balanced mixer that achieves x2 sub-harmonic mixing through two quadrature (I/Q) driven, stacked Gilbert-cell switching stages. Single ended-to-differential conversion, buffering and I/Q phase separation of the LO signal are included in this mixer.