Recently, the small size and the low power are required as the demand of the wireless communication application field increases. Because there are various problems that it is generated as the size and power consumption become smaller, many efforts are necessary in order to solve it. In the case of an oscillator, 1/f noise is increased as the size of chip becomes smaller. Therefore this affects on directly the phase noise characteristic. Moreover, as the power consumption becomes smaller, the phase noise characteristic will be inferior because the power consumption of an oscillator has an effect on the voltage amplitude of output node.
This thesis showed that the insertion of gm boosting circuits to differential Colpitts VCO allows larger voltage amplitude at the output node consuming same amount of power, which guarantees improved phase noise characteristic comparing to that of the differential Colpitts VCO. Also, we can achieve the same phase noise characteristic even though reduce power of oscillator. It can be possible low power VCO design.
The formally proposed differential/quadrature VCOs show better phase noise characteristic than conventional differential VCO at overall frequency. The proposed VCO/QVCO are designed for 2 GHz operation based on 0.13 um CMOS technology. Simulated phase noise verified for the 2.75 GHz carrier is -108.0 dBc/Hz at 100kHz and-128.7 dBc/Hz at 1MHz offset in VCO. Phase noise of QVCO is -104.8 dBc/Hz at 100kHz and -129.0 dBc/Hz at 1MHz offset. Each of power consumption for VCO/QVCO is 2mA and 4mA respectively at 1.5V supply.