A LowNoise, LowPower VCO with Automatic Amplitude Control for Wireless Applications

Voltage-contrelled oscillators (VCO's) used in postable wireless communications applications, such as cellular telepheny, are required to achieve low phase-noise levels while consuming minimal power. This paper presents the design challenges of a monolithic VCO with automatic amplitude control, which operates in the 300 MHz to 1.2 GHz frequeney range using different external resonators. The VCO phase-noise level is -106 dBc/Hz at 100-KHz. offset from an 800-MHz carrier, and it consumes 1.6 mA from a 2.7-V power sopply. An extensive phase-noise analysis is employed for this VCO design in order to identify the most important noise sources in the circuit and to find the optimum tradeoff between noise performance and power consumption.