28-GHz CMOS VCO With Capacitive Splitting and Transformer Feedback Techniques for 5G Communication

This paper presents a 28-GHz low phase noise voltage-controlled oscillator (VCO) in a 65-nm CMOS process for 5G communication applications. With the capacitive splitting and transformer feedback techniques, theoretical analysis and simulations are undertaken for the proposed oscillator, proving that its negative G_{m} can be enhanced over the interested frequency range and reduced at the harmonic frequencies. Moreover, the proposed oscillator startup performance is analyzed, and its tank quality factor, transient and phase noise performance are simulated. With 4-bit switch capacitors and varactors, the proposed VCO achieves a tuning range from 25.7 to 29.7 GHz, consuming 10.8 mW from a 0.9-V supply voltage. With a wideband common-source buffer, the output signal power is around 1 dBm. At 26.5 GHz, the proposed VCO achieves low phase noise of −105.8 dBc/Hz at 1-MHz offset and −130 dBc/Hz at the 10-MHz offset, respectively.