A low power 8-bit digitally controlled CMOS ring oscillator

A novel low power 8-bit digitally controlled oscillator in 0.18 μm CMOS technology is designed and implemented. It consumes only 12.6 mW to oscillate at 3.44 GHz. Sub-feedback technique is used to produce stable quadrature output with even number of stages. Tuning frequency range is from 1.2 GHz to 3.44 GHz, i.e., it has tuning width of about 97%. Phase noise of -110.9 dBc/Hz is achieved at 3.44 GHz carrier and 4 MHz frequency offset. Figure of Merit (FoM) is -158.6 dBc/Hz.