Flicker noise conversion in CMOS LC oscillators : capacitance modulation dominance and core device sizing

• Flicker noise upconversion mechanisms in oscillators have been acquired in the literature, however their relative weights are still under investigation. It is desirable to find the dominant one, since a certain noise suppression method reduces one mechanism but may increase another. In this work, we propose a systematic simulation method to distinguish their relative impacts. The outcome indicates parasitic capacitance is the dominant factor for both tail 1/f noise and switch pair 1/f noise upconversions, implying to use small dimension core devices. Design guidelines on sizing devices are presented and two suppression techniques are compared. Two voltage-controlled oscillators (VCOs) with these suppression techniques are fabricated in a 0.18 mu m CMOS process, allowing us to compare their performance. The two VCOs can be Focused-Ion-Beam (FIB) trimmed to change the width of switch pair FETs. The fair comparison of measurement results among them verify the dominant role of parasitic capacitance in 1/f noise upconversion. The measurement results also confirm the design guidelines and demonstrate the difference of two suppression methods.

Nyckelord

Oscillator

VCO

Device sizing

Flicker noise

1/f noise

Phase noise

TECHNOLOGY

TEKNIKVETENSKAP

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)