A low-noise, low-power VCO with automatic amplitude control for wireless applications

Voltage-controlled oscillators (VCO's) used in portable wireless communicat ions applications, such as cellular telephony, are required to achieve low phase-noise levels while consuming minimal power, This paper presents the d esign challenges of a monolithic VCO with automatic amplitude control, whic h operates in the 300 MHz to 1.2 GHz frequency range using different extern al resonators. The VCO phase-noise level is -106 dBc/Hz at 100-KHz offset f rom an 800-MHz carrier, and it consumes 1.6 mA from a 2.7-V power supply. 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.