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A Thesis Presented to The Academic Faculty
( z# Z* v3 V0 d# N6 a( E8 ]By Dale Scott Douglas In Partial Fulfillment Of the Requirements for the Degree
% y4 E/ r0 T' I/ q# |2 WMaster of Science in Electrical and Computer Engineering* E3 W' C+ m& \9 Q/ X
Georgia Institute of Technology( @4 @$ [$ r* e- K5 \
December, 2008. [2 x8 |4 d/ H2 C3 F
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SUMMARY
2 g$ t7 J9 Y+ O9 M& NSources of flicker noise generation in the cross-coupled negative resistance oscillator2 e* n' X& }" p' |% j
(NMOS, PMOS, and CMOS) are explored. Also, prior and current work in the area of% ]. O& N2 N7 ^( E" w% E0 @
phase noise modeling is reviewed, including the work of Leeson, Hajimiri, Hegazi, and/ Z* e4 V8 K3 s- i6 u4 ?
others, seeking the mechanisms by which flicker noise is upconverted.
* p' V3 T/ S/ c, ?% _A Figure of Merit (FOM) methodology suitable to the 1/f3 phase noise region is also
% t w7 e% t) c% g- ^, wdeveloped, which allows a new quantity, FOM1, to be defined. FOM1 is proportional to" p4 \! W1 v: A2 W4 O0 I+ ]
flicker noise upconverted, thus allowing the effectiveness of flicker noise upconversion7 s4 J. m' D; `, t6 J+ b. |
suppression techniques to be evaluated, despite possibly changing bias points or tank Q,# H: u9 Y1 f7 b3 r1 K8 Y# m6 i
which would change phase noise and FOM in the 1/f2 region.4 y7 B# R, h7 Y8 y5 q. H
The work of Hajimiri is extended with a simple ΛDC estimator for the special case of
2 }' N- v& ]$ l( h/ U+ d2 BLC CMOS oscillators. A method of adaptive control of an oscillator core is presented, as
4 f) B" y, w, S" y O% Hwell, comprised of a CMOS oscillator with a digitally adjustable N and P width, and a7 I" g7 N5 V+ C& Q& N; O
circuit (which is essentially a tracking ADC) which repeatedly adjusts the relative N to P2 [, n" H! h: k9 M' R
width dependent on the ΛDC estimate to maintain the condition of minimum flicker noise
1 Q* p; X4 M2 G# `* x8 u Lupconversion. A fixed calibration constant is sufficient to allow convergence to within
& g! O L, j, E* s& w0.7dB of optimal FOM1 for all cases of N width, for a varactorless oscillator test cell.1 B. o$ c) W8 ?; w- J F& ~
Finally, a circuit is proposed which would allow the flicker noise reduction technique
! `" V+ O- T: [7 D# Wof cycling to accumulation to be applied to continuous time oscillators, but is not
$ d) C* |9 L/ \! @% j& k6 lrigorously vetted. |
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