A SiGe Voltage-controlled Oscillator for 4G LTE Applications

A voltage-controlled oscillator (VCO) for fourth generation (4G) long term evolution (LTE) applications is designed and implemented using a standard 0.35-mu m SiGe BiCMOS foundry process in this paper. A crucial goal for the design is to achieve low phase noise required in 4G LTE systems under a low supply voltage. The presented VCO design is based on a NMOS-only cross-coupled pair with an integrated LC tank. An on-chip inductance is used in place of a tail current transistor in a conventional NMOS-only cross-coupled oscillator, which can reduce the supply voltage of the VCO. A phase noise is inversely proportional to the ratio of Q factor to inductance in a tank. Therefore, the tank with high ratio of Q factor to inductance is adopted for low phase noise. A supply voltage of 1 V is used with a power consumption of 5 mW. Measurements of the VCO are made, revealing that the frequency tuning range is 5.4%; the output power is -0.9 dBm; the second harmonic suppression is -29 dBc, and the phase noise is -116 dBc/Hz at a 1 MHz offset.