VCO design for low-power, high-efficiency transmitter applications

In this paper, we examine Voltage Controlled Oscillator (VCO) design techniques to be used in different transmitter applications. These transmitters, with their unique specifications such as fast oscillation start-up, fast locking or proper capacitor bank design, require different VCO design considerations. We first look at a fast on-off LC-VCO used to realize OOK IR-UWB transmitter. It is implemented in 0.18μm CMOS process and achieves 2Mbps at 236μW power consumption. Next, we examine injection locking LC-VCO employed to achieve efficient QPSK/O- QPSKB modulation. Through proper capacitor bank design, an EVM of 6.4% has been demonstrated at data rate of 50Mbps with the low reported energy efficiency of 118pJ/bit. The area consumption is only 0.28mm2 in 0.18μm CMOS process.