Investigation of Sub-Milliwatt Current-Reuse VCOs With Mono-Spontaneous Transconductance Match Technique

In this paper, we investigate amplitude compensation techniques of current-reuse (CR) voltage-controlled oscillators (VCOs) and propose an innovative mono-spontaneous transconductance match (m-STM) compensation technique. Due to the asymmetrical structure of CR VCOs, the imbalance between two differential oscillating amplitudes is inevitable. The proposed m-STM technique is able to overcome the unpredictable amplitude imbalance. Compared to a typical spontaneous transconductance match technique, the m-STM consumes less voltage headroom and is thus suitable for low-voltage application. Two sub-Milliwatt VCOs are designed and implemented. The first VCO, using the m-STM technique, demonstrates the compensation of amplitude oscillation and the feasibility of a lower supply voltage. The measured imbalance ratio is less than 0.8%. The power consumption is 0.9 mW using a supply voltage of 1.0 V. A FOM ^T of -191.6 dBc/Hz is achieved. The second VCO is designed for ultra-low-power consumption. The power consumption is less than 0.4 mW using a supply voltage of 0.9 V and the imbalance ratio is below 4.6%. A FOM^T of -193.1 dBc/Hz is achieved.