University of Toronto 2006 1

Frequency Scaling and Topology Comparison of Millimeter-wave VCOs

Keith TangSteven Leung

Nelson TieuPeter Schvan*

Sorin Voinigescu

University of Toronto, *NORTEL

University of Toronto 2006 2

Outline

Motivation

VCO Design Methodology

Frequency Scaling

Measurement

Summary

University of Toronto 2006 3

Motivation

MOSFET DC, HF and noise characteristics are scalable across technology nodesVCO topologies are very simple with one or two transistor half-circuits

Algorithmic design and frequency scaling methodologies can be developed even at 77GHz

→ Design productivity increases!

University of Toronto 2006 4

Colpitts VCO – Design1. Choose LTANK (smallest for

low phase noise)

2. Calculate Ceq from operating frequency

3. Bias transistors at optimum noise current density (0.15

mA/m)

4. Size transistors to provide enough negative resistance

5. Choose LS large (AC open)

6. Add RSS, CSS and LSS for bias and noise de-coupling

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Cross-coupled VCO – Design

1. Choose LTANK

2. Bias transistors at optimum noise current density (0.15 mA/m)

3. Size transistors to provide enough negative resistance

4. Calculate CVAR from operating frequency

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LTANK

C1

CVAR

Frequency Scaling

LTANK/k

C1/k

CVAR/k

LCfOSC

1

fOSCk

Same applies to cross-coupled VCO

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8 2 1.6

Nf does not scale with L and C at very high frequency because of parasitic gate and source resistances

fOSC drops by 20% in 180-nm VCO due to lack of parasitic extraction tools

VCO Test Structures

Colpitts VCO

90-nm

10 GHz

90-nm

77 GHz

180-nm

20 GHz

180-nm

40 GHz

90-nm

50 GHz

90-nm

80 GHz

LTANK [pH] 435 50 200 100 100 60

C1 [fF] 800 100 100 50 50 35

CVAR [fF] 800 100 100 50 50 35

Wf [um] 1 1 2 2 2 2

Nf 100 60 40 20 20 16

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VCO Test Structures (2)

Cross-coupled VCO

90-nm

10 GHz

90-nm

12 GHz

180-nm

17 GHz

LTANK [pH] 435 273 70

CVAR [fF] 260 260 70

Wf [um] 1 1 2

Nf 24 24 40

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Tuning range:

9.2 – 10.4 GHz (11.8%)

10-GHz Colpitts VCO

Record phase noise:

-117.5 dBc/Hz @ 1 MHz (100 avg.)

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Record tuning range:

73.8 – 80.0 GHz (8.3%)

77-GHz Colpitts VCO

Record phase noise:

-100.3 dBc/Hz @ 1 MHz (100 avg.)20log(8) ≈ 17dB higher than

10-GHz VCO’s phase noise!

University of Toronto 2006 11

10-GHz Cross-coupled VCO

Phase noise:

-109.2 dBc/Hz @ 1 MHz (100 avg.)

Tuning range:

9.3 – 10.9 GHz (15.8%)

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77-GHz CMOSCross-coupled VCOs

First VCO with p-MOSFET at 77 GHz

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Die Photos77 GHz Colpitts VCO:

0.42mm

0.40mm0.16mm

0.22mm

77 GHz Cross-coupledVCO:

0.37mm

0.27mm0.08mm

0.22mm

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√ ․√ X

At very high frequency…

Topology Comparison

Topology Colpitts Cross-coupled

Power consumption

Tuning range

Output power

Phase noise

At low frequency:

√ √

√ ․

․ √

√ X

√ X

․ √

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Figure of Merit for VCO defined in ITRS 2003:

But, output power is important for mixer, PA…

VCO Figure of Merit

DISS

OSC

PfLf

fFoM

][

12

1

DISS

OUTOSC

PfL

P

f

fFoM

][

2

2

University of Toronto 2006 16

FoMs Comparison

With FoM2, SiGe HBT VCOs show better performance than CMOS VCOs at mm-wave frequencies

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Summary

VCOs with record-breaking performances achieved by algorithmic design at 10 and 77 GHz

Frequency scaling of Colpitts VCOs from 10 to 77

GHz in 90-nm CMOS, 20 to 40 GHz in 180-nm CMOS demonstrated

First cross-coupled VCO with p-MOSFET at77 GHzColpitts topology exhibits better performances

than cross-coupled topology at mm-wave frequencies

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Acknowledgement

NORTEL and CMC for fabricationCMC for CAD toolsCFI and OIT for test equipmentDr. M. T. Yang for support

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Loss at Very High FrequencyConsidering the transistor’s resistance:

RG, RS increase with frequency and both lumped to RTANK

- Larger transistor size required at very high frequencies

It is critical to keep the VCO layout identical:- Transistor layout- Component orientation- Interconnect routing

such that layout parasitics also scale

fRRN

RR

fNC

SGf

SG

f

,1

,

1,1

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Ref Process fosc

[GHz]

Tuning[%]

Phase Noise[dBc/Hz]

Pout

[dBm]

Pdiss

[mW]

FoM1

[dB]FoM2

[dB]

* 90-nm CMOS:Colpitts

10 12.2 -117.5@1MHz 4.0 36 181.9 185.9

77 8.1 -100.3@1MHz -13.8 37.5 182.3 168.5

* NMOS cross-coupled 10 15.8 -109.2@1MHz -2.2 7.5 180.4 178.2

* CMOS cross-coupled 77 2.6 -84.3@10MHz -13.2 13.5 150.7 137.5

[1] 90-nm CMOS 60 0.17 -100@1MHz -23.2 1.9 192.8 169.6

*[6] SiGe HBT, fT = 170GHz 96 4.6 -101.6@1MHz 0.7 133 180.0 180.7

SiGe HBT, fT = 230GHz 105 4.4 -101.3@1MHz 2.7 133 180.3 183.0

[7] SiGe HBT, fT = 175GHz 77 8.7 -97@1MHz 18.5 1200 163.9 183.0

100 6.2 -90@1MHz 14.3 1200 159.2 173.5

[8] SiGe HBT, fT = 200GHz 75 6.1 -105@1MHz 3.5 72 183.9 187.4

[9] SiGe HBT, fT = 200GHz 98 3.3 -85@1MHz -6 60 167.0 161.0

[10] SiGe HBT, fT = 200GHz 85 2.7 -94@1MHz -8 25 178.6 170.6

[11] InP HBT, fT = 75GHz 108 2.6 -88@1MHz 0.92 204 165.6 166.5

[12] 130nm CMOS 90 2.4 -105@10MHz -16 15.5 172.2 156.2

[13] 130nm CMOS 114 2.1 -107.6@10MHz -22.5 8.4 179.5 157.0

* our work