Analysis and Design of an E-Band Transformer-Coupled Low-Noise Quadrature VCO in 28-nm CMOS

This paper presents an E-band quadrature voltage-controlled oscillator implemented in 28-nm CMOS. Two fundamental oscillators are coupled by means of gate-to-drain transformers to realize accurate quadrature phases and switched coupled inductors are added for tuning extension. Closed-form expressions of the oscillation frequency and the tuning extension design parameters are derived. The time-variant nature of the circuit noise to phase noise (PN) of the presented topology is investigated, resulting in simple design guidelines for optimal design. Based on the proposed techniques, the realized prototype is tunable over two bands of almost 5 GHz each separated in frequency, while occupying only 0.031 mm. The peak measured PN at 10-MHz offset is -117.7 dBc/Hz from a 72.7-GHz carrier and -110 dBc/Hz from a 88.2-GHz carrier and varies less than 3.5 dB within each band.