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
University of Toronto 2006 5
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
University of Toronto 2006 6
LTANK
C1
CVAR
Frequency Scaling
LTANK/k
C1/k
CVAR/k
LCfOSC
1
fOSCk
Same applies to cross-coupled VCO
University of Toronto 2006 7
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
University of Toronto 2006 8
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
University of Toronto 2006 9
Tuning range:
9.2 – 10.4 GHz (11.8%)
10-GHz Colpitts VCO
Record phase noise:
-117.5 dBc/Hz @ 1 MHz (100 avg.)
University of Toronto 2006 10
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%)
University of Toronto 2006 12
77-GHz CMOSCross-coupled VCOs
First VCO with p-MOSFET at 77 GHz
University of Toronto 2006 13
Die Photos77 GHz Colpitts VCO:
0.42mm
0.40mm0.16mm
0.22mm
77 GHz Cross-coupledVCO:
0.37mm
0.27mm0.08mm
0.22mm
University of Toronto 2006 14
√ ․√ X
At very high frequency…
Topology Comparison
Topology Colpitts Cross-coupled
Power consumption
Tuning range
Output power
Phase noise
At low frequency:
√ √
√ ․
․ √
√ X
√ X
․ √
University of Toronto 2006 15
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
University of Toronto 2006 17
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
University of Toronto 2006 18
Acknowledgement
NORTEL and CMC for fabricationCMC for CAD toolsCFI and OIT for test equipmentDr. M. T. Yang for support
University of Toronto 2006 19
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
University of Toronto 2006 20
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