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[email protected] 2006 1

Osci l latorsAleksandar Tasic

Electronics Research LaboratoryDelft University of Technology

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UMTS VCO Requirements

VCO design parameters Design requ irem entOscillating frequency 2.1GHz

Tuning range 400MHzVoltage swing 0.7V

Phase noise -110dBc@1MHz

Supply voltage 3V

Power consumption 10mW

Technology parameters ValuesTechnology BiCMOS

Number of metals 4

Transit frequency 50GHzMIM capacitors available

Varactors available

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Outline

LC Oscillators

Oscillation Signal Steady-State Amplitude

Interpretation of Noise in Oscillators Linear Phase-Noise Model

Spectral Analysis of Phase Noise

Noise Suppression of Bias Current Sources

LC-Oscillator Design Procedure

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LC Osc il lato rs

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Negative Resistance Oscillator

C CL,

UT

VCC

RLV V

Q1 Q2

ITAIL

QCS

QCS

resonating LC tank

active pair

biasing current source

Mg

2/

10

VLC

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- Simplified Model

LC/10

TKM Gg oscillation condition

2/mM gg

oscillation frequency

2/CC V

GTK C L-gM

+

V

-gMV

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7/[email protected] 2006 7

202

0

)(2)(

CRL

RG C

LTK

tank conductance

0

0

1L C

L V C

LQ Q

R C R

quality factors

CL

TKQQL

G111

0

C

2R C

L

RL

GTK C L

LC Tank

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Steady-State

Osc il lat ion Signal

Ampl i tude

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Sub-Outline

Differential Pair Characteristic

Large-Signal Conductance Steady-State Oscillation Signal Amplitude

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Amplitude Stabilization

Amplitude regulator

amplitude control mechanism

Resonator Resonator

ALC

y(x)y(x)

Nonlinear amplifier

well defined nonlinearity

timing reference loss

compensation

loop-gain control

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IOUT

VIN

1/f0

1/f0

Differential Characteristic

tcosx

tanhI)t(iOUT2

0

I0

-I0

tcosV)t(vIN 1

TT VVV/Vx 11

n

nOUT tncosaI...tcosItcosItcosI)t(i 1253 120531

current harmonic content

)x(aI)x(I nn 0 d)ncos(cosx

tanh)x(an2

1

Q1 Q2

IOUT

VIN

I0

2

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Large Signal (Trans)Conductance

II

VV

VI

VIxG T

T

M

0

1

1

0

1

11 )(

x

xag

I

I

xgxG MmM

)(2

1)( 1

0

11

x

xagxG MM

)(2/)(

11

GM1(x)/gM

x

1

0.5

1 10

gainloopsignalsmall

1

uctance)trans(condsignalsmall

ductance(trans)conlfundamentasignallarge

1011 jHg

g

VGM

M

M

steady state oscillation condition

1011 jHVGM

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Current Harmonic Components

0

120531 12cos...5cos3coscos)(n

nOUT tnaItItItIti

output current

close to square wave ifV1 >> VT

n

I

n

I

I

TAIL

n

24 0

harmonics of the square-wave signal current

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11

1

1

111

2)(

V

I

V

I

I

I

V

IVG TAILTAIL

TAIL

Mkg

VG

M

M 1)( 11

lfundamentacurrentresistancetanklfundamentavoltage

TKTAILRIV2

1

steady state fundamental amplitude

small signal loop gain (k)

MTKgRk

large signal conductance and steady state oscillationcondition

Steady-State Oscillation Amplitude

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So Far

VCO design parameters Design requi rementOscillating frequency 2.1GHz

Tuning range 400MHz

Voltage swing 0.7V


Supply voltage 3V



Number of metals 4

Transit frequency 50GHz

MIM capacitors available

Varactors available

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In terp retat ion o f

Noise in

Osci l lators

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Sub-Outline

Signal Phasor Description

Signal Spectral Description Phase-Noise Definition

Phase-Noise Specification

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Bennett Noise Interpretation

kkk tatn cos)(

White noise spectrum (power spectral density)

One noise component (time domain)

AfN )(

ak known amplitude

k known angular frequency

k random phase (constant and uniform)

)2( A

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Oscillation Signal Description

Ideal vs. actual oscillation signalV0cos 0t vs. V0[1+a(t)]cos[ t+ (t)]

a(t) amplitude modulated component

(t) phase modulated component

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Oscillation Signal Phasor

Description

in-phase component (AM) can be removed

quadrature-phase component (PM) is unavoidable

)(ta

)(t

a(t)

n(t)

v(t)

)(t

ttttattttatv tn 0000)( sin)(cos)(cos)(cos)](1[)(

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Oscillation Signal Phasor

Description

a(t)

n(t)

v(t)

)(t

ttttattttatv tn 0000)( sin)(cos)(cos)(cos)](1[)(

amplitude control

mechanism

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Oscillation Signal Spectral

Description

=

+

AM

PM

f0 f+f0

oscillating signal and

noise component

amplitude modulated

component

phase modulated

component

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oscillating signal and

noise component

amplitude control

mechanism

phase modulated

component

Oscillation Signal Spectral

Description

=

+

AM

PM

f0 f+f0

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Phase Spectrum vs. Oscillation

Signal Spectrum

)()()()()( 0000 fffffffffV

0

f0-f0

( )f phase spectrum

oscillation signal spectrum

ttAtA

ttAttAtv

kkk

kkk

00

00

sinsincos

sincos)(cos)(

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Phase Noise Definition

ratio of the noise power in a 1Hz bandwidthat frequency f0+ fand the carrier power

( )=10log[Pside-band( 0+ )/Pcarrier( 0)] [dBc/Hz]L

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Why is Phase Noise Important?

Reciprocal mixing

desired signal covered by thephase-noise skirt of the interferer

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Phase Noise Specification

Typical blocking profile

Specra of downconverted signals

BW

blocker

S/N

desired signal (MDS)

f

( f)=SMDS-SBLOCK-10logBW-S/N [dBc/Hz]

S/N=SMDS-NxBW

=N/SBLOCKL

L

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Linear

Phase-NoiseModel

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Sub-Outline

Generic Linear Phase-Noise Model

Circuit-Specific Linear Phase-Noise Model

G

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Generic Linear Phase-Noise

Model - Outline

Linear Oscillator Model

LC-Tank noise

active part noise

(Phase) Noise Factor

Phase-Noise Properties

Li O ill t M d l

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Linear Oscillator Model

GTK C L

-gM

LC-tank impedance (noise shaping)

2

0

2

22

0

22

2

0

0

00

00

44

1

22

Q

R

QG)(Z

C

j

/

Lj)(Z

TK

TKTK

TK

G

CQ

LGQ

0

0

1

LC-tank quality factor

LC-tank noise

transconductornoise

no tail-currentsource noise

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LC-Tank Noise

GTK C L

-gMI(GTK)

tank resistance noise (RTK=1/GTK)

TKTK KTGI 4

2

tank contribution to the equivalent voltage noise spectral density2

2 2 2 0

2

0

( )( )

TKTKTK

GV I Z KT

C

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Active Part Noise

GTK C LI(GTK)-gM

I(gM)

active part contribution to the equivalent voltage noisespectral density

2

0

2

0

2

)(A

C

GKTV TKAP

active part noise factorA

excess negative conductance

additional noise of the active devices

ideallyA=1 (i.e., gM=GTK, and no excess noise from the active part)

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Phase Noise

VN,TOT

IN,TOT

222

APTKTOT VVV

2

0

2

0

2

)(F

C

GKTV TKTOT

2

0

2

2

QP

FkT

S

)L(

2

0

22

2

1

2/2

1) QFGVKTV

V

TKSS

TOT

L(

total voltage noise spectral density

oscillator noise factorF=1+A

resulting phase noise

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Phase Noise Properties

inversely proportional to tank quality factor (square)

inversely proportional to signal power

-20dB/decade slope at mid frequencies (~MHz)

directly proportional to oscillation frequency (square)

2

0

2

2

QP

FkT

S

)L(

Leesons phase noise model

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Phase Noise Plot

Leesons modification to capture 1/fand flat noise part

f/

S QP

FkT)(

1

2

0 12

12

L

1/f noise

Thermal, shot noise

Noise floor due to activeelements or instrumentation

Circuit Specific Linear Phase

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Circuit-Specific Linear Phase-

Noise Model - Outline

Spectral Noise Analysis

oscillation condition

LC-tank, gm

-cell, current source noise

(phase) noise factor

Circuit Noise Analysis

LC-tank, gm

-cell, current source noise

(phase) noise factor

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Spectral Analys iso f No ise in

Swi tch ing

LC-Osci l lators

S b O tli

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Sub-Outline

Duty Cycle of Small-Signal gm-cell Gain Oscillation Condition

LC-Tank Noise

gm-cell Noise Tail-Current Source Noise

(Phase) Noise Factor Bipolar VCO

(Phase) Noise Factor CMOS VCO

Bipolar vs. CMOS VCO

Is it Indeed so Simple?

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Is it Indeed so Simple?

noise from the transistors Q1 and Q2 is switched ON and OFF

noise from current source QCS is modulated by oscillator switching

LC-tank noise

transconductornoise

tail-current sourcenoise

C C

L

V V

Q1 Q

2

QCS

IGT

ICIC

IB

VB

VB

ICS

IB

VCO N i S

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VCO Noise Sources

2 ( ) 2N B Bv r KTr

2 ( ) 2 / 2N B B mi I qI KTg

2 ( ) 2 / 2N C C mi I qI KTg

2 ( ) 2N TK TKi G KTG

,2 2 2

, , , ,

1( ) 2 1 2 ( ) ( )

2

m CS

N TCS B CS m CS B CS m CS

F T

gi I KT r g r g

LC-tank noise

base-resistance thermal noise

collector-current shot noise

base-current shot noise

tail-current source output noise

A ti P t B V lt N i

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Active Part - Base Voltage Noise

small signal gain in presence of a large signal

g(t)

2/

2/

2 0

2)('

1'

T

T

tkjdtetg

T

ck

Fourier domain even harmonicsc

0 c2c4

Fourier domain convolution = spectra shifting

C C

L

V V

Q1 Q

2

QCS

QCS

VB VB

)(')( 02

, kffScfS VBk

kVBTK

IOUT

VIN

dIOUT dVIN

1/f0

1/2f0

gM

A ti P t B C t N i

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Active Part - Base Current Noise

base current (switching) transfer function

2/

2/

2 0

2)(''

1''

T

T

tkjdtetg

Tc

k

Fourier domain even harmonics


C C

L

V V

Q1 Q

2

QCS

IBIB

QCS

)('')( 02

, kffScfS IBk

kIBTK

:)2

(''

2

BIg

1/2f0

1.41

0

1

Active Part Collector Current Noise

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Active Part - Collector Current Noise

collector current (switching) transfer function

2/

2/

2 0

2)('''

1'''

T

T

tkjdtetg

Tc

k

Fourier domain even harmonics


C C

L

V V

Q1 Q

2

QCS

ICIC

QCS

:)2

('''

2

CIg

)(''')( 02

, kffScfS ICk

kICTK

1/2f0

1

0

0

Active Part Noise Folding

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Active Part Noise Folding

x

f0 2f0 3f0

cAP,0 cAP,2

cAP,4

=

shifting of active part noise spectral components

, 0

2 2 2

0 0 0 0 0 0

2 2 2

2 0 2 0 2 0

2 2 2

2 0 2 0 2 0

( )

' ( ) '' ( ) ''' ( )

' ( ) '' ( ) ''' ( )

' (3 ) '' (3 ) ''' (3 )

...

TK AP

VB IB IC

VB IB IC

VB IB IC

S f f

c S f f c S f f c S f f



active part noise at odd multiples of the resonant frequency istransformed into the LC-tank noise at the resonant frequency

...2)(2

2,

2

0,0, AP

k

kAPAPAPTK SccffS ...)3()( 00 ffSffSS APAPAP

T il C t N i

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Tail Current Noise

oscillator switching model

2

2

12 012

1 /T

/T

t)k(jdte

T

a k

Fourier domain odd harmonics


a1 a3

C C

L

V V

Q1 Q

2

QCS

QCS ICS

)()( 02

, kffSafS CSk

kCSTK

IOUT

VIN

1/f0

1/f0

T il C t N i F ldi

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Tail Current Noise Folding

shifting of tail-current source noise spectral components

...)6()4(

)4()2(

)2()()(

0

2

50

2

5

0

2

30

2

3

0

2

1

2

10,

ffSaffSa

ffSaffSa

ffSafSaffS

CSCS

CSCS

CSCSCSTK

tail current noise at even multiples of the resonant frequency

is transformed into the LC-tank noise at resonant frequency

CS

k

kCSTK SaffS2

120, 2)( ...)4()2( 00 ffSffSS CSCSCS

X

f0 2f0 3f0

c1 c

3

=

aa

T t l N i

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Total Noise

total power spectral density across the LC tank

APTKCSTKTKTOT SSSS ,,

near linear operation (Q1 and Q2 always ON; gM=GTK)

2 22 2 22 2( ) 2

2

C BTKTOT B TK

I IV Z I V G

total voltage noise density across the LC tank

22

12

22

2

22

2

22

2

222 '''''')( CSk

kC

k

kB

k

kB

k

kTKTOT IaIcIcVcIZV

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Other Noise Analysis Methods

Linear frequency domain analysis Craninckx

noise superimposed on the carrier

Linear time varying analysis (Impulse Sensitivity

Function) Hajimiri

noise added to phase

Nonlinear analysis Samori

noise added to phase

S F

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So Far


Tuning range 400MHz

Voltage swing 0.7V


Supply voltage 3V



Number of metals 4


Varactors available

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Suppress ion o f No ise

in Oscillators

Tail-Curren t Source

O tli

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[email protected] 2006

Outline

Contribution of Tail-Current Source Noise to

Phase Noise of LC-Oscillators

Techniques for Reduction of Tail-CurrentSource Noise

Analysis of Tail-Current Source Noise

Bias Noise Suppression - Design Example

VCO Noise Contributions

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VCO Noise Contributions

LC-tanknoise ~ 1

transconductor

noise ~ 0.5+ck

tail-current sourcenoise ~ (0.5+ck)k

C C

L

V V

Q1 Q

2

QCS

IGT

ICIC

IB

VB

VB

CBCB

ICS

IB CACA

(k=loop gain)

TCS noise >> LC-tank noise + gm-cell noise (k>>1)

VCO Phase Noise

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VCO Phase-Noise

TCS noise >> LC-tank noise + gm-cell noise

powersignalsource)currentcell,-tank,-(LCpowernoise mgPN=

phase noise ~ 1/k2 orconst

TCS noise suppression with RID

phase noise ~ 1/k2 or 1/k

VCO noise power ~ 1 orck2

VCO noise power ~ 1 orck

(~k2)

Bias Noise Reduction Techniques

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Bias Noise Reduction Techniques

resona ntinductivedegeneratio n(RID)resistive degeneration(RD)commonemi tter(CE)

high supply

required large area if

integrated

noise injection if

discrete

transconductor

noise always ON

reduced output

impedance

resistive

degenerationinductive

degeneration filtering?

VIN

ITAIL

VIN

ITAIL

RD

LD

VIN

ITAIL

+

-

CD

Resonant-Inductive

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Resonant Inductive

Degeneration (RID)

high TCS noise

suppressionintegration

no voltage

headroom

integrated degenerative inductor (LRID)matched with base-emitter capacitance (C )

at 2f0

LRID

VIN

ITAIL

C

P & C f RID

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Pros & Cons of RID

good suppression of high frequency TCSnoise (2f0)

low voltage operation

small chip area (vs. discrete solutions)

TCS DC noise upconversion

large area (vs. resistive degeneration) poorer noise suppression at high supplies

(vs. resistive degeneration)

Tail-Current Source with

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Tail-Current Source with

Resonant-Inductive Degeneration

LRID matched to C at 2f0

rB noise contribution reduced

transconductance gain small at resonance series resonance

IB noise contribution small

common-base like configuration (gain of 1)

ICnoise contribution removed

parallel resonance

emitter open at resonance (IC floats)

LRID

VINITAIL

C

IC

IB

Circuit Diagram for Noise

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Circuit Diagram for Noise

Transfer Functions

(VB -VE)gm

C

E

B

LRID

rBC

IB IC IOUT

VB

IC to IOUT: VB short, IB open

IB to IOUT: VB short, ICopen

VB to IOUT: ICopen, IB open

Tail-Current Source Noise

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Tail Current Source Noise

Contributions

2

1( ) 1

1/ 1 ( )

OUT m

BBm RID B m

RID T

I gf

C r fI g j C j L r g L f

2

1( ) 1 1 0

1/ 1 ( )

OUT m

BCm RID B m

RID T

I gf

C r fI g j C j L r g L f

1( ) ( )

1/

OUT Tm

T RID RID T B

I ff g

L j L j C fV

series resonance

parallel resonance

parallel resonance

TCS w/ RID vs TCS w/o RID

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TCS w/ RID vs. TCS w/o RID

more than a factor (fT/2f0)2 noise reduction after RID

22 2 0

,

0

1 24 0 ( ) 2

2 2

m TCS RID B m

F T

g f fI kT r g

f f

22

0

14 1 0 ( ) 2

2 2

m TCS B m

F

g fI kT r g

f

TCS noise without degeneration

TCS noise with degeneration

for (fT/2f0)=10, a factor of100 reduction

22 2

0,

2CS RID CS

T

fI I

f

5.7GHzband VCO

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LC-tankRID

buffer-g-cell

m

buffer

5.7GHz

band VCO

5 metals

active area 0.1mm2

LRID=2.6nH, 7-turns, 0.01mm2

Phase Noise (w/ RID vs w/o RID)

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to groundto ground

to TCS transistors to ground

Phase Noise (w/ RID vs. w/o RID)

TCS noise into phase noise: w/ RID 9%, w/o RID 77%


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with RID

without RID


6dB phase-noise improvement with RID

-112dBc/Hz @1MHz from 5.7GHz @ 4.8mA&2.2V

RID Conclusions

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RID Conclusions

resonant-inductive degeneration for a 4-foldphase noise improvement of a 5.7GHz VCO

no voltage headroom required

small inductance for resonance at 2f0

cost-effective implementation in multi-layer

technologies

manifold oscillator phase-noise improvement

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LC-VCO Des ign

Procedure

Sub-Outline

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Sub-Outline

VCO Specifications

LC-Tank Design

How to Choose LC-Tank Inductance How to Choose LC-Tank Varactor

Active-Part Design

UMTS VCO

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UMTS VCO

WCDMA Specs ValueReceiving Band (GHz) 2.11-2.17

Channel Spacing (MHz) 5 (3.84)

Multiplex / Modulation FDD / QPSKMDSeff (dBm) -99

SNR (dB) / BER 7 / 1E-3Processing Gain (dB) 25Tx-Rx Isolation (dB) 50

Blocker @ 8MHz (dB) -46




Supply voltage 3V



Number of metals 4Transit frequency 50GHz

MIM capacitors available

Varactors available

(8MHz)=-99-(-46)-10log(3.84e6)-7=-129dBc/Hz

L

Series vs Parallel Resonator

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Series vs. Parallel Resonator

frequency f0=2.1GHz

desired signal powerP=10mW

RTK

C L

L=3nH, C=1.9pF, RS=2

fundamental current and voltage

i=100mA, v=0.2V

L=3nH, C=1.9pF, RTK=800

fundamental current and voltage

i=5mA, v=4V

QL=20

very large current moderate current and voltage

realistic choice

RS

CL


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resonating LC tank

active part

biasing current source

LC1

0

2/gm

2T

C II

2/CC VC CL,

UT

VCC

RLV V

Q1 Q2

ITAIL

QCS

QCS

LC Tank Design

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LC Tank Design

LCf

2

10

oscillation frequency

2/CC V

parasitics impose largercapacitive tuning range

MIN,V

PAR

MIN,V

PAR

MIN,V

MAX,V

MIN

MAX

C

C

CC

CC

f

f

21

2

MIN,V

PAR

MIN

MAX

MIN

MAX

MIN,V

MAX,V

C

C

f

f

f

f

C

C12

22

determine L and C

determine CMAXand CMIN

tuning range

How to Choose L?

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tank conductance

CL

TKQQL

G111

0

How to Choose L?

2

0

2

2F

V

RRKT

S

CL)L(

largerL => largerQL

largerL => lowerGTK

largerL => lower power consumption

largerL => largerRL largerL => poorer

choice ofL

phase noise

choose for the largest L having peak Q close to the

operating frequency

largerL => lowerfRES, fQ-PEAK

largerL => lower tuning range

L

How to Choose C?

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How to Choose C?

largerC=> lowerQ

largerC=> largerGTK

largerC=> larger power consumption

tank conductance phase noise 20

2

2F

V

RRKT

S

CL)L(2

020

2 )C(R)L(

RG C

LTK

choice ofC

largerC=> slightly better

largerC=> larger tuning range

choose forCproviding not more than the required

frequency tuning range

largerC=> lowerRC

L

Active Part Design

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Active Part Design

chosen LC tank parameters determine losses tobe compensated2

02

0

2 )C(R)L(

RG C

LTK

oscillation condition gM>GTKdetermines the very

minimum compensating active-devices current

2/mM gg

cross-coupled pair conductance

TC

L

TTKTmC V)C(R)L(

R

VGVgI2

02

0222

choose for the transistors having enough fT(~10f0) forthe determined collector current

What About Phase Noise?

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What About Phase Noise?

there is nothing better than the best LC-tank the best LC tank chosen determines power

consumption and accordingly active devices

operating current

shot noise is directly determined by operating

current, i.e., LC tank

the larger the transistor the lower the base

resistance thermal noise (but more parasitics)

choose for as large transistors as possible havingenough fT(~10f0) for the determined collector current

Tail Current Source

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Tail Current Source

Tail current noise around even multiples of the oscillating

frequency is transformed into the phase noise of the VCO

Tail current noise contribution larger than all other

contributions together

Reducing the output noise power of the current source, its

contribution to the phase noise is reduced as well

emitter degeneration reduces the tail-

current source noise transfer functions

resistive degeneration effective at all

frequencies but requires voltage headroom

inductive degeneration effective in narrow

frequency band but requires no voltage

headroom

ZD

B,CSV

B,CSI

RIDCSI ,

C,CSI

QCS

So Far

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So Far

VCO design parameters Design requi rementOscillating frequency 2.1GHzTuning range 400MHz

Voltage swing 0.7V


Supply voltage 3V



Number of metals 4


Varactors available

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VCO Des ign

Example -Measurements

Post-Design Flow

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Post Design Flow

Oscillator Design Layout

Oscillator Chip Packaging

Printed Circuit Board Design

Measurement Setup

Interpretation of Results

VCO Chip Microphotograph

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LC-gM

LRID

LRID

VCO Chip Microphotograph

VCO chipPackaged VCO IC

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VCO chip

bondwire

bondpad

SMD t fPackaged VCO IC on PCB

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package

SMD transformer

SMD capacitor

bias choke

VCO IC

SMD resistor

SMD inductor

Measurement Fixture

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package

transformer

bias filtering

bias filtering

VCO IC

I/O

connectors

PCB

Measurement System

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y

testfixtureLO

VCC

ITAIL

VVCO

UTUNE

IBUFFER

VCC-XF

VCC+

+ +

+

IBUFFER

+VVCO

Spectrumanalyzer

Chip and Measurement Equipment -I t f

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Interface

Measured Signal Spectrum

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g p

signal frequency

signal power

Measured Frequency Tuning Range

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Measured Frequency Tuning Range

1,7

1,8

1,9

2

2,1

2,2

2,3

2,4

2,5

0 0,5 1 1,5 2 2,5 3

Tuning voltage VT [V]

O

sc

illa

tin

gf

requency

[GHz

]

V =3VCC

fLOW=1.8GHz

fUP=2.4GHz

f=600MHz

VTUNE=3V

Measured Phase Noise

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Measured Phase Noise

PN(1MHz)=-110dBc@3mW

Measured VCO Performance

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Measured VCO Performance

VCO design parameters Measurement Results

Central frequency 2.1GHz



Supply voltage 3V


Poor PCB Design

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g

number of spurs from cables and supply necessity for filtering on supply lines

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Conclus ions

So far

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LC Oscillators

Oscillation Signal Steady-State Amplitude

Interpretation of Noise in Oscillators Linear Phase-Noise Model

Spectral Analysis of Phase Noise

Noise Suppression of Bias Current Source LC-Oscillator Design Procedure

PCIRF_6_8_VCO

Documents

Transcript of PCIRF_6_8_VCO