This work describes a novel wide tuning range ring voltage controlled oscillator (RVCO) for generating six-phase signals. The proposed circuit is realized by coupling two identical three-stage single-ended inverter based RVCOs. The coupling network injects the common mode signals from one RVCO to the other one and vice versa in cross-connected manner. Three-stage RVCOs used for coupling have been configured by modifying the conventional current-starved RVCO. The proposed six-phase RVCO is optimized using an improved version of Non-dominated Sorting Genetic Algorithm III (NSGAIII). In this algorithm, sigma scaling method is used to control the selection pressure and enhance the performance of the algorithm. The proposed RVCO oscillates at 4.3 GHz. The proposed oscillator can operate from 1.65 GHz to 4.62 GHz under the supply voltage of 1.5 V. This oscillator demonstrates a wide frequency tuning range of 95 %. The proposed RVCO has been designed in 0.18 µm standard CMOS technology and the chip area is 28 × 38.5 µm ².