Wide frequency multiphase oscillator designed by coupling two identical
ring voltage controlled oscillators
Abstract
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.