A 1/f Noise Upconversion Reduction Technique for Voltage-Biased RF CMOS Oscillators

作者：Shahmohammadi Mina^*; Babaie Masoud; Staszewski Robert Bogdan

来源：IEEE Journal of Solid-State Circuits, 2016, 51(11): 2610-2624.

DOI：10.1109/JSSC.2016.2602214

• Class-D oscillator
• class-F oscillator
• digitally controlled oscillator
• flicker noise
• flicker noise upconversion
• impulse sensitivity ISF)
• phase noise (PN)
• voltage-biased RF oscillator

In this paper, we propose a method to reduce a flicker (1/f) noise upconversion in voltage-biased RF oscillators. Excited by a harmonically rich tank current, a typical oscillation voltage waveform is observed to have asymmetric rise and fall times due to even-order current harmonics flowing into the capacitive part, as it presents the lowest impedance path. The asymmetric oscillation waveform results in an effective impulse sensitivity function of a nonzero dc value, which facilitates the 1/f noise upconversion into the oscillator's 1/f(3) phase noise. We demonstrate that if the omega(0) tank exhibits an auxiliary resonance at 2 omega(0), thereby forcing this current harmonic to flow into the equivalent resistance of the 2 omega(0) resonance, then the oscillation waveform would be symmetric and the flicker noise upconversion would be largely suppressed. The auxiliary resonance is realized at no extra silicon area in both inductor-and transformer-based tanks by exploiting different behaviors of inductors and transformers in differential-and common-mode excitations. These tanks are ultimately employed in designing modified class-D and class-F oscillators in 40 nm CMOS technology. They exhibit an average flicker noise corner of less than 100 kHz.

• 出版日期2016-11