An on-chip low power low phase noise VCO with frequency divider for low jitter low phase noise applications

This paper presents the design and implementation of a low power low phase noise Voltage Controlled Oscillator (VCO) using 0.25-micron Silicon-on-Sapphire (SOS) technology for low jitter low phase noise applications. The VCO comprised of a cross-coupled complementary LC core generating 3.6GHz output and a fully optimised Injection Locked Frequency Divider (ILFD) circuit generating the divide-by-two frequency output at 1.8GHz. In addition, a controllable tail current source is added to the VCO and divider to optimise their phase noise, power consumption and performance. The phase noise of the proposed VCO and divider is also improved by employing a filtering circuit to suppress the second harmonic component of drain and source currents. High-Q custom inductors were also designed and implemented to improve the system performance. Results indicate that the VCO and divider achieved the phase noise of -106.2dBc/Hz and -112.2dBc/Hz respectively at 100kHz offset. The VCO and divider core consumed only 6.1mW and 15.7mW of power respectively at 2.5 V power supply.