A 52% tuning range QVCO with a reduced noise coupling scheme and a minimum FOMT of 196dBc/Hz

A wide-tuning range QVCO with a novel complimentary-coupling scheme is presented. Two NMOS-only VCOs are coupled via complimentary PMOS injection transistors. This shifts the injection current away from the zerocrossings of the output voltage, thereby reducing the sensitivity of the VCO to injection noise, which results in significant phasenoise improvement. Phase-shift is achieved without frequencydependent phase-shifting networks, allowing robust coupling over a wide tuning range. As a proof-of-concept, a prototype is designed in TSMC 65nm process with 4-bits of discrete tuning spanning the frequency range 4.6-7.8 GHz (52% tuning range). The prototype operates from 0.5V supply, with a power consumption ranging from 7.4mW–11mW, while achieving a minimum figure-of-merit (FOM) of 181.6dBc/Hz, and a minimum figure-of-merit with tuning-range (FOMT ) of 196dBc/Hz.