Abstract
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/f3 phase noise. We demonstrate that if the ω0 tank exhibits an auxiliary resonance at 2 ω0, thereby forcing this current harmonic to flow into the equivalent resistance of the 2 ω0 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.
Original language | English |
---|---|
Article number | 7571191 |
Pages (from-to) | 2610-2624 |
Number of pages | 15 |
Journal | IEEE Journal of Solid State Circuits |
Volume | 51 |
Issue number | 11 |
DOIs | |
Publication status | Published - 2016 |
Keywords
- Class-D oscillator
- class-F oscillator
- digitally controlled oscillator
- flicker noise
- flicker noise upconversion
- impulse sensitivity function (ISF)
- phase noise (PN)
- voltage-biased RF oscillator