A low phase noise CMOS oscillator with tail current-shaping technique in wireless implantable SoC applications

摘要

In this paper, a voltage-controlled oscillator (VCO) circuit topology suitable for ultra low-phase noise applications is presented. A differential stage is added for tail current shaping to a conventional cross-coupled VCO to improve the phase noise. The tail current becomes larger when the sensitivity of the output phase to the noise is smaller and the oscillator output voltage reaches to the maximum or minimum values. The proposed circuit does not consume extra power and does not utilize noisy active devices. Simulation results show the 2.5 dB improvement in the phase noise at 1 GHz center frequency. The power consumption of the proposed circuit is 2.44 mW with a figure of merit (FoM) of -192.2 dBc/Hz.