Sinusoidal shaping of the ISF in LC oscillators

A new method to decrease the phase noise of the sinusoidal oscillators is proposed. The proposed method is based on using a dynamic transistor biasing in a typical oscillator topology. This method uses the oscillator impulse sensitivity function (ISF) shaping to reduce the sensitivity of the oscillator to the transistor noise and as a result reducing the oscillator phase noise. A 1.8 GHz, 1.8 V designed oscillator based on the proposed method shows a phase noise of -130.3dBc-Hz at 1 MHz offset frequency, thereby showing about 6 dB phase noise decreasing in comparison with the typical constant bias topology. This result is obtained from the simulation based on 0.18u CMOS technology and on-chip spiral inductor with a quality factor equal to 8. Copyright © 2007 John Wiley & Sons, Ltd.

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