FLICKER NOISE IN CMOS LC OSCILLATORS国外硕士论文

qitianhua

A Thesis Presented to The Academic Faculty
By Dale Scott Douglas In Partial Fulfillment Of the Requirements for the Degree
Master of Science in Electrical and Computer Engineering
3 y& w" z, B' m9 h6 jGeorgia Institute of Technology
/ M% m* O# |' L6 ^4 |8 {  IDecember, 2008


SUMMARY
4 B, s+ ^9 Z# [; u) ^( PSources of flicker noise generation in the cross-coupled negative resistance oscillator
  q' B4 g; o) X: r! i(NMOS, PMOS, and CMOS) are explored. Also, prior and current work in the area of
8 R4 T3 i2 I" R9 p/ m; u' ^phase noise modeling is reviewed, including the work of Leeson, Hajimiri, Hegazi, and
8 G3 U6 |* R( X& ?others, seeking the mechanisms by which flicker noise is upconverted.
A Figure of Merit (FOM) methodology suitable to the 1/f3 phase noise region is also
2 f" z6 K# O- H. Ndeveloped, which allows a new quantity, FOM1, to be defined. FOM1 is proportional to
+ x  z  v' H, N8 z9 K! \flicker noise upconverted, thus allowing the effectiveness of flicker noise upconversion
( c+ N: b( e, q$ m' Y; Asuppression techniques to be evaluated, despite possibly changing bias points or tank Q,
which would change phase noise and FOM in the 1/f2 region.
4 }( R: e4 A8 A- y% M9 w0 kThe work of Hajimiri is extended with a simple ΛDC estimator for the special case of
LC CMOS oscillators. A method of adaptive control of an oscillator core is presented, as
well, comprised of a CMOS oscillator with a digitally adjustable N and P width, and a
  n! S: {4 e; Ccircuit (which is essentially a tracking ADC) which repeatedly adjusts the relative N to P
& K+ S, ?' Y: W" E' {. n2 y* gwidth dependent on the ΛDC estimate to maintain the condition of minimum flicker noise
upconversion. A fixed calibration constant is sufficient to allow convergence to within
0.7dB of optimal FOM1 for all cases of N width, for a varactorless oscillator test cell.
# W( t' T9 G& o  s, h' nFinally, a circuit is proposed which would allow the flicker noise reduction technique
of cycling to accumulation to be applied to continuous time oscillators, but is not
rigorously vetted.