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Departement Elektriese, Elektroniese & Rekenaar-IngenieursweseDepartment of Electrical, Electronic & Computer EngineeringKgoro ya Merero ya Mohlagase, Elektroniki & Bointšinere bja Khomphutha
SiGe based SiGe based Multiple-phase VCO Multiple-phase VCO Operating for mm-WaveOperating for mm-WaveFrequenciesFrequencies
Deepa GeorgeDeepa George
Saurabh SinhaSaurabh Sinha
Microelectronics & Electronics GroupUniversity of Pretoria, South Africa
Wednesday 19 April 2023
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mm-Wave systems• Unlicensed spectrum – 7 GHz bandwidth @ 60 GHz• Short range communication systems - specific attenuation
characteristics :10-15 dB/km • Highly advanced Silicon integrated circuit technology
eg: SiGe HBTs with fT = 500GHz
• Reduced antenna size – phased arrays
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Phased arrays
Phased array transmitter [1]
• Number of antenna elements
• Narrow-band systems
Phase control range = 360°
Phase resolution = 22.5°
• Phase shift @ RF, IF or LO
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Integrated phase shifter
•Vector sum phase shifting method
- Practically demonstrated at 5 GHz [1]
Vector sum method
I
Q
V
Vφ 1tan
Block diagram
2Q
2I VV RESV
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VCO• Centre frequency of 60 GHz and a tuning range to
accommodate process, voltage and temperature variations• Figure of merit
• Phase noise
• Phase noise improvement– Circuit techniques
• LC oscillators – lowest phase noise
• Fully differential configuration
• LC filtering technique
– Device technology
0( ,1Hz)( ) 10.log sideband
carrier
PL
P
21mW
FOM ( , ) 10.log cc
DC
fL f f
f P
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VCO – Basic topology
• High Q tank
• Qtank dependant on Qvaractor
– MOS varactors are preferred– Accumulation mode varactors
• Transmission lines as L
• Transistors biased at NFmin current density
• High tank swing
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Improving the phase noise•LC filtering technique – improves phase noise and tuning range [2]
Normal topology LC filtering technique
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SiGe BiCMOS technology
• Low 1/f noise • Graded Ge content in base
– Reduces base transmit time, b
– Increases unity gain frequency, ft
IBM SiGe structure Ge content in base
1~
2 Je Jc b e c e c Jc ns SUBt C
kTC C R R C R C
f qI
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Need for HICUM/L0• SGPM inaccurate for SiGe transistors at high frequencies
– Charge storage effects
– Internal base resistance
– Self-heating
– Base-Collector avalanche effect
• Advanced models (MEXTRAM, VBIC, HICUM/L2)
– Complicated – EC, model equations, parameter extraction and computational effort
• HICUM/L0 for high frequency circuit design [4]
SGPM equivalent circuit
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Design and Challenges
• Transistor model – Accurate and time-efficient• Interconnect modeling
- Transmission line effects• Substrate effects shielded/accurately modeled• Accurate extraction of layout parasitic effects• SpectreRF from Cadence
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Conclusion
• Integrated phase shifter– Reduce rms phase error
– Investigate the current scaled DACs effectiveness to compensate for the amplitude mismatch introduced by QAF
• Investigate techniques to improve the phase noise of the VCO
• Accuracy of HICUM/L0 for mm-wave designs
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References [1] A. Hajimiri, H. Hashemi, A. Natarajan, X. Guan and A. Komijani, “Integrated
Phased Array Systems in Silicon,” Proc. IEEE, vol. 93, no. 9, pp. 1637–1655, Sept. 2005.
[2] T. A. K. Opperman and S. Sinha, “A 5 GHz BiCMOS I/Q VCO with 360◦ variable phase outputs using the vector sum method,” Proc. IEEE PIMRC 2008 Symp., Cannes, pp. 1–5, 15-18 Sept. 2008.
[3] H. Li and H. M. Rein, “Millimeter-Wave VCOs With Wide Tuning Range and Low Phase Noise, Fully Integrated in a SiGe Bipolar Production Technology,” IEEE J. Solid-State Circuits, vol. 38, no. 2, pp. 184–191, Feb. 2003.
[4] M. Schröter, S. Lehmann, S. Fregonese and T. Zimmer, “A Computationally Efficient Physics-Based Compact Bipolar Transistor Model for Circuit Design Part I: Model Formulation,” IEEE Trans. Electron Devices, vol. 53, no. 2, pp. 279–286, Feb. 2006.
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Feedback/QuestionsDeepa GeorgeCarl & Emily Fuchs Institute for MicroelectronicsDept.: Electrical, Electronic & Computer EngineeringUniversity of PretoriaPretoria 0002SOUTH AFRICA
E-mail: [email protected]
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Acknowledgements
The authors would like to thank the Federal Ministry for Education and Research (BMBF), Germany and National Research Foundation (NRF), South Africa for enabling bilateral collaboration; particularly for enabling reciprocity around usage of the High Current Model (TU-Dresden).