3.6 GHz highly monotonic digitally controlled oscillator for all-digital phase locked loop

An analytical method to make a trade-off between the tuning range and differential non-linearity (DNL) for a digitally controlled oscillator (DCO) is proposed. To verify the approach, a 12-bit DCO is designed, implemented in 0.18 μm CMOS technology, and tested. The measured DNL was -0.41 Least Significant Bit (LSB) in the worst case without degrading the other parameters which, in turn, results in highly monotonic behavior over the tuning range from 3.12 GHz to 4.15 GHz. The measured phase noise was -135.2 dBc/Hz (@ 4 MHz offset) at oscillation frequency of 3.6 GHz with 19.2 mW power consumption which results in figure of merit (FOM) to be -181.5 dBc/Hz.