Low Phase Noise Series-coupled VCO using Current-reuse and Armstrong Topologies

This paper proposes a new series-coupled voltage-controlled oscillator (VCO). The proposed VCO consists of four current-reuse Armstrong VCOs (CRA-VCOs) coupled by four transformers. The series-coupling, current-reuse, and Armstrong topologies improve the phase noise performance by increasing the negative-Gm of the VCO core with half the current consumption of a conventional differential VCO. The proposed VCO consumes 6.54 mW at 9.78 GHz from a 1-V supply voltage. The measured phase noise is -115.1 dBc/Hz at an offset frequency of 1 MHz, and the FoM is -186.5 dBc/Hz. The frequency tuning range is from 9.38-10.52 GHz. The core area is $0.49mm^2$ in a $0.13-{\mu}m$ CMOS process.