Ultralow-Power Ku-Band Dual-Feedback Armstrong VCO With a Wide Tuning Range

Here, we investigate the design of a Ku-band Armstrong voltage-controlled oscillator (VCO) utilizing dual transformer feedback for low-voltage low-power operation. The primary transformer feedback between the drain and the source of the VCO increases the output voltage swing under low supply voltage. With the secondary transformer feedback, g_m-boosting is obtained by the coupling between the drain and the gate of the Armstrong VCO. Combined with transformer feedback, g_m-boosting further reduces the negative transconductance required for oscillation startup, enabling ultralow-power operation. Thus, the proposed Armstrong VCO with dual feedback operates at 0.4 V with power consumption as low as 600 W. Under this condition, the measured phase noise of the VCO is -100.6 dB/Hz at 1-MHz offset from a 14.1-GHz carrier. The results show that the proposed VCO is suitable for very low-power applications requiring high signal purity.