Design of Octave Tuning Range LC VCO With Ultralow KVCO Using Frequency-Dependent Implicit Capacitance Neutralization Technique

This article presents a technique of frequency-dependent implicit capacitance neutralization (FD-ICN) amongcapacitor bank and varactors inL Cvoltage-controlled oscil-lator (VCO) to facilitate ultralow VCO gain (K-VCO) acrossan octave frequency tuning range (TR). Series interconnectinductors are used between capacitor units to feature the inversecapacitance-frequency (C-f) relationship with varactors, thusyielding the proposed FD-ICN. A split 8-bit capacitor bankwith centrosymmetric double-cross layout pattern is designed,enabling an enhanced FD-ICN through multiple capacitanceequivalent iterations of the capacitor bank. The proposedFD-ICN technique is validated in a prototype of dual-modeelectric-coupling VCO and fabricated in 130-nm CMOS process,exhibiting a measured frequency TR of 72.1% from 6.49 to13.81 GHz with aK(VCO )of 7-73 MHz/V. The VCO shows acompetitive phase noise (PN) and figures-of-merit in TR (FoMT)from-121.3 to-111.4 dBc/Hz and 197.4 to 201.7 dBc/Hz at1-MHz offset across the whole TR.