RTU1A-5

RFIC – Atlanta June 15-17, 2008

RTU1A-5

A 25 GHz 3.3 dB NF Low Noise Amplifier based upon Slow Wave

Transmission Lines and the 0.18 μm CMOS Technology

A. Sayag(1), S. Levin(2), D. Regev(2), D. Zfira(2),

S. Shapira(2), D. Goren(3) and D. Ritter(1) (1) Department of Electrical Engineering, Technion, Haifa, Israel

(2) Tower Semiconductors inc., Migdal HaEmek, Israel(3) IBM Haifa Research Laboratories, Haifa, Israel


Outline

• Low Noise Amplifier design methodology

• New semi-analytic model for slow wave

transmission lines

• LNA performance


Motivation

• Can we get close to the transistor minimum

NF in 24GHz LNA design?

Best 0.18 μm 24 GHz LNA: NF=3.9

[Shih-Chieh Shin et al., IEEE MWCL, 2005.]

@ 24GHz


LNA Design Methodology

1. Determine the optimal current density

2. Determine critical circuit element values

3. Choose the transistor width


Transistor Performance Determined by Current Density

@ 24GHz

@ 24GHz

@ 24GHz


Transistor Performance Determined by Current Density


Circuit Topology: Common source with inductive source degeneration


Source Inductor value for each Width


Example: Source Inductor for W=40μm


How does the Insertion Loss of the Input Matching Network Depend on Transistor Width?

Equal Insertion loss contours

•Each point on the Smith Chart corresponds to a hypothetical transistor input impedance

•Input impedance is matched to 50 ohms by a matching network with inductors having Q=20


Insertion Loss Map of the Input Matching Network with Q = 10


Insertion Loss Map of the Input Matching Network with Q = 30


We need Q > 20 !


Choosing the Transistor Widths (assuming a two identical stage amplifier)

1

21

1

G

NFNFNFtotal

W [um] Transistor Max

Gain [dB]

Min NF [dB] gs [dB] NF total [dB]

20 7.2 0.82 0.3 1.2

40 8 0.9 0.8 1.3

80 8.2 1 1.44 1.6

*gS - normalized source gain factor


Choosing the Transistor Widths (assuming a two identical stage amplifier)

W [um] Max Gain [dB] Min NF [dB] gs [dB] NF total [dB]

20 7.2 0.82 0.3 1.2

40 8 0.9 0.8 1.3

80 8.2 1 1.44 1.6


High Q Slow Wave Transmission Lines

2SiOeff

2SiO

Si

• Effective dielectric constant larger than that of the surrounding dielectric material

• The effective dielectric constant determined by geometry


Properties of Slow Wave TL

• Isolation from the lossy silicon substrate

• Shorter wavelength shorter matching networks

• Lower loss per wave length higher Q of resonators

• Smaller die area

• Higher characteristic impedance

• Complicated EM simulations

• Complicated layout


Measured and Simulated Slow Wave Transmission Line Parameters

twice the effective dielectric cons. of SiO2


Properties of Slow Wave Transmission Line


Our Compact Analytic RLCG Model of Slow Wave Transmission Lines

*A. Sayag et al., submitted to TMTT


Using our Compact Model to predict Slow wave TL performance

W


Low Noise Amplifier

•All the matching networks are slow wave transmission lines


Measured and Simulated Performance


Simulated Noise Contributions

• Transistors: 70%

• Transmissions lines: 23%

• Capacitor parasitics: 7%


Comparison with State of the Art LNAs

mWPdBNF

GHzBWdBGainFOM

D

1

[1] Shih-ChiehShin et al., IEEE Microwave and Wireless Component Letters, July, 2005.[2] E. Adabi et al., " RFIC Symposium, June 3-5, 2007, Honolulu, Hawaii.


Conclusions

• LNA design methodology presented.

• New analytic model of slow wave transmission lines.

• Record 2.8dB NF @ 24 GHz obtained using 0.18 μm technology.

• Slow wave transmission lines contributed only 23% of the total noise.

• Lower NF should be achieved using more advanced technologies


Thank You!


Testing our model: Comparison between Slow Wave Transmission Line and

Grounded Coplanar Waveguide

Grounded coplanar Slow wave


Comparison of Slow Wave and Grounded Coplanar Waveguide


Comparison between Slow Wave Transmission Line and Coplanar Waveguide

Coplanar Waveguide slow wave


Comparison between Slow Wave and Coplanar Waveguide

RTU1A-5

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