Differential VCO and Differential VCO and Frequency Tripler using - - PowerPoint PPT Presentation

RFIC 2003

Mina Danesh 1

Differential VCO and Differential VCO and Frequency Tripler using Frequency Tripler using SiGe SiGe HBTs HBTs for the 24 GHz ISM Band for the 24 GHz ISM Band

Mina Danesh*,

Frank Gruson, Peter Abele, Hermann Schumacher

* - Microwave Communications (Montreal, Canada) University of Ulm (Germany)

2003 RFIC Symposium June 9, 2003 Philadelphia, PA, USA

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Outline Outline Outline

• Project overview
• 8 GHz Differential VCO
• Circuit Design
• Measurement Results
• Differential Frequency Tripler
• Circuit Design
• Measurement Results
• VCO/Tripler MMIC
• Measurement Results

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24 GHz ISM Band 24 GHz ISM Band Overview Overview

• ISM Band: 24 - 24.25 GHz
• Applications
• Short-range wireless data link
• Short range radar sensors (automotive)
• Project goals
• Low cost, reliable, fully integrated, energy efficient MMIC
• Attractive SiGe technology (low-cost, high integration)
• System Design Requirements
• LO source to drive a mixer at 0-10 dBm LO power
• LO tuning range >= 250 MHz
• IF frequency range: 500 MHz to 1 GHz
• FM / BPSK modulation carrier phase noise: -80 dBc/Hz

at 100 kHz

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LO Source Design LO Source Design

• Differential design advantages:
• Easier integration with frequency divider and Gilbert-type mixer
• Better common-mode rejection
• 2x maximum voltage swing
• Reduced crosstalk & immunity from substrate
• Higher differential Q if substrate loss dominates

VCO

Buffer

Frequency tripler Frequency source building block IC

Phase detector Loop filter

Vcont

Upstream or downstream conversion

LO

Frequency divider (static +

programmable)

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Atmel Atmel SiGe1 HBT Process SiGe1 HBT Process

HBT (0.8 m) technology fT = 30 GHz BVce0 = 6 V HBTS

(selectively implanted collector )

fT = 50 GHz BVce0 = 3 V Initial SiGe1 Process: 2 Al metal layers

Nitride passivation layer Metal1 Metal2

• xide

Si substrate 3.7 m 300 m 20 -cm 1.5 m

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Differential VCO Circuit Differential VCO Circuit Design Design -

• Schematic

Schematic

Q1 Rbb Vbb Iee Ree Vcc Ls Cb Cb Rbb Vbb Q2 Q3 Q4 Ls Cv Cv Vct

Differential VCO

OUT+ Vcc Cbo Q5 Rf Cn Rcb Cf Reb

Emitter follower

OUT- Vcc Cbo Q6 Rf Cn Rcb Cf Reb

Emitter follower

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VCO Circuit Design VCO Circuit Design -

• Layout

Layout

Differentially driven symmetric inductor

HBTS transistor pair Varactors Biasing

Emitter follower

G G P P S+ 380

Emitter follower

380 P G S- G

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VCO Design VCO Design – – Symmetric Symmetric Inductor Inductor

Layout generated by custom script

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VCO Design VCO Design – – Symmetric Symmetric Inductor Inductor

105

• w = 10

s = 3 N = 3 M2 Underpass in M1 Port1 Port2 Port3 Reference: M. Danesh and J. R. Long, “Differentially Driven Symmetric Microstrip Inductors”, IEEE Trans. MTT,

• vol. MTT-50, no. 1, Part II, pp. 332-341,
• Jan. 2002.

Zd = Z11 + Z22 – Z12 – Z21

Qdiff = Re[Zd] / Im[Zd]

Lind = 0.8 nH (meas); 0.76 nH (sim) Rdc

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VCO Tuning Measurements VCO Tuning Measurements

40 MHz/V 160 MHz/V Vcc - vo 270 MHz

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VCO Phase Noise Results VCO Phase Noise Results

• 90 dBc/Hz @ 100 kHz

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VCO Performance Summary VCO Performance Summary

• Frequency of operation:

7.95 – 7.75 GHz

• Tuning voltage: 0 – 2.7V
• Tuning sensitivity: 50 MHz/V
• Output power: 4.4 dBm +/- 0.1
• Biasing voltage: 3.3V
• Total current: 27 mA
• Phase noise: -90 dBc/Hz @100 kHz
• Harmonic rejection: > 30 dBc

4.4 dBm > - 30 dBc

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Frequency Tripler Design Frequency Tripler Design

Pout+ Pin+ Pin- Pout- R= 30 HBTS transistor pair Biasing GND GND GND GND 380

• 150

Symmetric Inductor w = 10 ; s = 3 Rdc 2*Ls = 0.32 nH Q at 24 GHz = 13 IN- IN+ Q1 Rbb Cb2 Vbb Iee Ree Vcc Ls OUT+ OUT- Cb2 Cb1 Cb1 Rbb Vbb Q2 Ls Cs Cs

Characteristics:

• Differential transistor pair
• high input voltage swing
• limiting amplifier
• square wave at output
• rich in odd harmonics

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Frequency Tripler Frequency Tripler Measurements Measurements

Pin = 0 dBm

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Frequency Tripler Frequency Tripler Measurements Measurements

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Frequency Tripler Frequency Tripler Conversion Loss Conversion Loss

I = 28 mA V = 3.3 V DC pwr = 92.4mW

GaAs comparison: Optimal conversion loss of – 4 dB

• 9 dB

RF-RF efficiency: 12%

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VCO/Tripler MMIC VCO/Tripler MMIC

Tripler inductor VCO inductor Buffer Buffer VCO o/p Tripler o/p VCO o/p Tripler o/p

VCO Tripler

300 600

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VCO / Tripler Results VCO / Tripler Results

Frequency (GHz) VCO output power (dBm) Tripler output power (dBm) 7.82 / 7.81 0.5 / 2.6

• 9 / -8.8

15.6 / 15.6

• 33 / -32
• 30 / -37

23.5 / 23.4

• 34.5 / -33
• 10 / -4

Values in italics indicate simulated results.

Frequency tripler phase noise degradation ~ 20log(3) = 9.5 dB Measured spot phase noise @ 100 kHz ~ -80 dBc/Hz

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VCO / Tripler Tuning Range VCO / Tripler Tuning Range

100 MHz/V 270 MHz/V 420 MHz

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VCO VCO-

• Tripler LO

Tripler LO Performance Summary Performance Summary

> 20 dBc Even Harmonic rejection

• 80 dBc/Hz @100 kHz

Phase noise 55 mA Total current 3.3V Biasing voltage

• 10 dBm +/- 1 dB

Output power 100 - 270 MHz/V Tuning sensitivity 0 – 2.5V Tuning voltage 23.5 – 23.08 GHz Frequency of operation

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Conclusion Conclusion

• Integrated variable frequency source for

the 24 GHz ISM Band

• Taking advantage of differential circuits
• Frequency tripler built in a SiGe process
• Optimization of the VCO at a lower

frequency

• Overall frequency source performance

enhancement

• Feasibility of a low-cost solution