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 zero-crossings of the output voltage, thereby reducing the sensitivity of the VCO to injection noise, which results in significant phase-noise improvement. Phase-shift is achieved without frequency-dependent 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 (FOM_T) of 196dBc/Hz.