Microwave SiGe Circuits and Baseband Modulation for 5-GHz Wireless Communications

High-Speed radio design research activities undertaken by the Communications Technology Department at IBM's TJ Watson Research Center are described. Hardware results for the key building blocks of a 5-GHz SiGe microwave transceiver, namely low-noise amplifier, mixer, and voltage-controlled oscillator, are presented. It is demonstrated that the low-noise, high-gain characteristics of SiGe HBTs enable the implementation of fully-monolithic microwave circuits at supply voltages of 3.3V or less. Measured performance levels and related figure-of-merit numbers for these SiGe circuits are shown to be comparable or better than the previously published results using other microwave technologies at C-band. A novel baseband modulation scheme which provides increased spectral efficiency over traditional Direct-Sequence Spread Spectrum technology in an indoor multipath fading environment is also discussed. The predicted coverage range at 1% block error rate is more than 30 meters for a 10Mb/s robust indoor wireless system at 5 GHz. The ultimate goal is to implement a cost-effective, short range, high-speed radio in the 5-GHz U-NII band and leverage IBM's ultra-high-bandwidth, 200-mm wafer, 0.5um lithography SiGe BiCMOS production technology.