A low power low noise eight-phase output ring oscillator

Aiming at the problems of the ring oscillator such as large power consumption, loud noise, linearity deficiency etc., a novel ring oscillator with cross feed forward structure is proposed based on TSMC 55 nm process. After the contribution percentage of device thermal noise and flicker noise on the output phase noise is analyzed, the capacitance filtering technique is applied to reduce the output phase noise. The linear current is obtained with the source negative feedback circuit to improve the linearity of the frequency modulation, and offers a wide tuning range.The Spectre RF simulation results show that the designed ring oscillator has a frequency coverage of 0.2 GHz～3.8 GHz, produces 8 phases. Its phase noise is -91.34 dBc/Hz@1 MHz, and the current consumption is 4.6 mA at the 1.2 V supply voltage. The results also indicate the good linearity.