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Paper presentation – Ultra-Portable Devices

Paper:

Presented by:

Hooman Darabi, Janice Chiu,

A noise Cancellation Technique in Active RF-CMOS

Mixers.

Journal of Solid-State Circuits, vol. 40, no. 12, pp. 2628-

2632, Dec 2005.(compact version also at ISSCC, feb. 2005)

Carl Bryant

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Outline

• Introduction

• Noise sources

• Noise improvement

• Implementation

• Results

• Summary

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Introduction

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• Double balanced mixer

• 1/f (flicker) noise important for direct conversion receiver

• Most 1/f noise comes from switch pair

Introduction

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1/f noise

White noise

Nois

e

Frequency

• 1/f noise produced when drain current nonzero

• Noise large for low frequencies

• Narrowband receiver may operate below total noise corner

Noise sources

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LO

Switch fully ON

Switch fully OFF

Both switch devices conducting

• Switch pair contributes no noise when fully on/off

• Noise introduced during zero crossings

• Noise modulates zero crossings

Noise sources

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Noise Improvement

• Reduce flicker noise component:

• Increasing switch size

– Slower switches

– Increases capacitive load of input devices

• Reduce width of noise pulses:

• Faster LO slopes

– Increses power consumption in LO buffers

– Supply voltage limits LO amplitude

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Noise improvement

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• Increases switch stage impedance 1/gm

• More current shunted through parasitic capacitance

• Reduces bandwidth and linearity

• Reduce height of noise pulses• Reducing switch stage current

Noise improvement (this work)

• Reduce switch stage current dynamically

• Starve switch stages only during switching event

• Detect switch event by monitoring source voltage

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Noise improvement

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Implementation

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Implementation

• Injection devices should be dimensioned to turn on/off

• Large injection devices add parasitic capacitance

• Since the noise is reduced, switch pair can be made smaller

• TSMC 0.13μm

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Results

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Results

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Summary

• Significant improvement of flicker noise

• Little negative impact on performance

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Chip photo

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Further reading

• Darabi H., Abidi A.A.,“Noise in RF-CMOS mixers: a simple

physical model”, Solid-State Circuits, IEEE Journal of , vol.35,

no.1, pp.15-25, Jan 2000

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