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Simple and Accurate Approach to Implement the Complex Trans-Conductance in Time-Domain Simulators

Simple and Accurate Approach to Implement the Complex Trans-Conductance in Time-Domain Simulators M. Homayouni, D. Schreurs, and B. Nauwelaers K.U.Leuven, Belgium. Outline. Introduction to Table-Based Model Microwave and mm-Wave Issues Implementation Linear Model Non-Linear Model

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Simple and Accurate Approach to Implement the Complex Trans-Conductance in Time-Domain Simulators

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  1. Simple and Accurate Approach to Implement the Complex Trans-Conductance in Time-Domain Simulators M. Homayouni, D. Schreurs, and B. Nauwelaers K.U.Leuven, Belgium

  2. Outline • Introduction to Table-Based Model • Microwave and mm-Wave Issues • Implementation • Linear Model • Non-Linear Model • Conclusion • Acknowledgement

  3. Introduction to Table-Based Model • Layout and equivalent circuit of CMOS FinFET transistor.

  4. Introduction to Table-Based Model • Equivalent Circuit • Intrinsic Network: Parameters that are bias-dependent, representing active channel. • Extrinsic Network: Parasitic elements that are bias-independent, originating from layout pads.

  5. Introduction to Table-Based Model • Model (equivalent circuit parameters) is extracted from measurements carried out on actual device. • DC-measurements • S-parameter measurements • Thermal measurements • Noise measurements • Intrinsic Network Parameters • Bias-dependent • Extracted from S-parameters at hot bias condition (Vgs and Vds non-zero) • Tabulated in table-files • Extrinsic Network Parameters • Bias-independent • Extracted from S-parameters at cold bias condition (Vds=0) • Tabulated in table-files

  6. Microwave and mm-Wave Issues • Complex Trans-Conductance • gm, represents the gain • t, represents the channel time-delay Complex Trans-conductance

  7. Microwave and mm-Wave Issues • Influence of channel time-delay on model accuracy. • Most sensitive parameter: S21. Error (difference between model and measurement ) in percentage in S-parameters due to ignorance of channel time-delay. • mm-Wave application: • 38GHz fast Ethernet, 60GHz WLAN, 77GHz car-radar • Significant features: gain (S21), fmax, ft

  8. Implementation • Do microwave software support complex trans-conductance (time-delay)? Complex trans-conductance in ADS Gain: gm = 45mS time delay: t = 5.2psec

  9. Implementation • t, represents the channel time-delay • Virtual implementation of time-delay • Introduction of transmission line • @ Gate terminal to delay the sampling voltage • @ Drain terminal to delay the current of voltage-controlled current source (VCCS) Delayed Voltage

  10. Implementation • How to determine and implement the t-line? • T-line should be terminated with match-load to guarantee no reflection. • Input impedance of t-line should be orders of magnitudes larger than impedance seen from connection point (Zin should be much larger than Zout) . • Electrical length of t-line corresponds to time-delay. Zout Zin

  11. Implementation • Implementation Issues for Simulators • T-lines are not very convenient for time-domain simulators. • T-lines are approximated by lumped LC-network • Simpler to extract the values • Simpler to develop them in model • Limited in terms of frequency range

  12. Implementation • Approximate LC-Network • If wt<<1 then the LC-network is performing as a t-line that delays the input signal. • t is in order of tenth of psec. • Z0 is in order of M • In our case (FinFET transistor): • 300MHz < f < 50GHz • t<1 psec wt < 0.3333 , acceptable but limited in terms of frequency range

  13. Implementation • Comparison between model and measurement in both cases, with time-delay and without time-delay. • Accuracy of model is improved due to implementation of time-delay. Improvement in model accuracy

  14. Implementation • Non-linear table-based model Integration

  15. Implementation • Implementation of time-delay in non-linear model • Different from linear model • No need for t-line or equivalent lumped network • Complex trans-conductance can be split into real and imaginary parts • Non Quasi-Static non-linear model can be implemented Real trans-conductance: modeled as normal Negative capacitance

  16. Conclusion • Channel time-delay is significant at microwave and mm-wave frequencies. • Accurate technique was introduced to introduce complex trans-conductance in time-domain simulators. • Simple and accurate approximation was introduced to ease the time-delay implementation in model for time-domain simulators. • Simple method was introduced to implement non quasi-static non-linear table-based models.

  17. Acknowledgements • Nano-RF project IST-027150 • FinFET team at IMEC • Andries Scholten from NXP

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