Tour Agilent ADS EMPro 2011 Stability Analysis of Microwave Circuits

Transcription

1 Tour Agilent ADS EMPro 2011 Stability Analysis of Microwave Circuits S. Dellier, PhD

2 AMCAD Engineering Introduction to AMCAD s products and services AMCAD is a provider of new RF & Microwave solutions Privately-owned independent company Founded in 2004 by PhDs from XLIM Laboratory Head Office and Lab in Limoges, France Multi-disciplinary and high skilled team New building under construction Slide 2

3 Solutions and Tools Services Component Pulsed IV/ RF meas. Model extraction Load-Pull meas. Design, Stability Analysis, Behavioral Modeling X-parameters System Circuit STAN tool PIV-RF system Modelling tool (FET) LP system Products IVCAD software platform Slide 3

4 Agenda Introduction Existing methods STAN tool and application examples Q&A Slide 4

5 Introduction Stability analysis is a critical step of RF design flow Classical methods are either not complete or too complex Stability analysis need to be efficient (especially in large signal) - Rigorous - Fast - User-friendly - Compatible with commercial CAD softwares Slide 5

6 Existing Methods Linear analysis small signal - K factor - Normalized Determinant Function (NDF) - Stability envelope Non-linear analysis large signal - Nyquist criterion - NDF - Bolcato, Di Paolo & Leuzzi, Mochizuki, Slide 6

7 Existing Methods Linear analysis Widely used: K factor (also µ and µ now) - K>1 & <1: unconditional stability of two port network - K<1: conditional stability stability circles Unconditional stability Conditional stability Unconditional instability Limitations: Only indicates that a stable circuit will continue to be stable when loading it with passive external loads at the input or output Do not guarantee the internal stability of the circuit! Slide 7

8 Source Existing Methods Linear analysis Potentially instable architectures for which K factor is not enough Multi-stage power amplifier Multi-fingers transistor IN OUT Gate Drain Slide 8

9 phase(zsond) H (º) db(zsond) H (db) Existing Methods Pole-Zero Identification Principle H( s) H( j ) Frequency domain Identification techniques n i 1 p j 1 ( s z ) ( s ) i j Im (GHz) E9 4.0E9 6.0E9 8.0E9 1.0E10 1.2E10 Freq frequency (GHz) Pole-zero plot poles Re (GHz) zeros R G f 0, P in v out Node n (i,f ) in s Slide 9 R L Complex conjugate poles with positive real part -> start-up of an oscillation Oscillation frequency = Module of the imaginary part

10 STAN Tool J.M. Collantes et al. Monte-Carlo Stability Analysis of Microwave Amplifiers, 12th IEEE Wireless and Microwave Technology Conference, April 2011, Florida. A. Anakabe et al. Automatic Pole-Zero Identification for Multivariable Large-Signal Stability Analysis of RF and Microwave Circuits, European Microwave Conference, September 2010, Paris. J.M. Collantes et al. Expanding the Capabilities of Pole-Zero Identification Techniques for Stability Analysis, IEEE Microwave Theory and Techniques International Symposium, June 2009, Boston. Slide 10

11 STAN Tool Key Elements Suitable for both linear and non-linear stability analysis Very easy to use with any CAD tool Very easy to analyze results Relative stability information delivered Oscillation mode knowledge -> Help to find the suitable stabilization strategy Parametric Analysis implemented Monte-Carlo Analysis Slide 11

12 STAN Tool Integration in CAD Environment GENERATOR Perturbation introduction node CIRCUIT LOAD in out Var VAR Eqn VAR1 fin=9.65 GHz Pin=12 Input frequency Input power P_1Tone cmp1198 Num=1 Z=50 Ohm P=polar(dbmtow(Pin),0) Freq=fin ampli X1 Term Term1 Num=1 Z=50 Ohm HARMONIC BALANCE HarmonicBalance HB1 Freq[1]=fin Order[1]=10 SS_MixerMode=yes SS_Start=f1 SS_Stop=f2 UseAllSS_Freqs=yes MergeSS_Freqs=yes Var VAR Eqn VAR3 f1=fstart+fin e9 f2=fend+fin Meas MeasEqn Eqn meas1 Zsond=mix(v_sond,{-1,1})/mix(I_sond.i,{-1,1}) frequency=ssfreq-fin Var VAR Eqn VAR2 fstart=4.325 GHz fend=5.325 GHz n_point=101 I_Probe I_sond v_sond I_1Tone SRC1 I_LSB=polar(0.0001,0) Start sweep frequency Stop sweep frequency Number of frequency points Nonlinear stability analysis template EDA Tool Templates for ADS AC simulation for linear HB simulation for non-linear STAN tool integrated in IVCAD software User-friendly GUIs Slide 12

13 STAN Tool ADS Templates Slide 13

14 STAN Tool ADS Templates Ho(jω) results.txt STAN tool Slide 14

15 STAN Tool Automatic mode ( s zi ) The order of Hs ˆ () is a priori unknown i H( s) 1 p ( s j ) Automatic algorithm for pole-zero identification in the j 1 context of stability analysis is integrated in STAN tool n Phase(H 0 ) (º) Mag(H 0 ) (db) H( j ) H( s) Freq (GHz) This routine eases the use of pole-zero identification for multivariable stability analysis Slide 15

16 STAN Tool v out Node n (i,f ) in s A B FET 2 FET 1 FET 3 Multi-nodes A- No oscillation detected in the common node FET 4 FET 5 FET 6 B- Oscillation detected in the transistor node Odd mode (parametric frequency division) will determine the stabilization strategy Slide 16

17 STAN Tool Multi-parameters Analysis with swept parameter(s) Verification for various conditions (Pin, Zload, ) Optimization of stabilization networks R G P IN f 0, v out (i,f ) in s Z load R stab Slide 17

18 polar(inestables_hb1..mod,inestables_hb1..phase) S(1,1) STAN Tool Example: 3-stage LDMOS DPA for SDR applications Multi-parameters Application requires absence of spurious for a wide range of operating conditions Multivariable large-signal stability analysis versus input frequency, input power and real and imaginary parts of load termination Z L. Frequency division (f in /2) detected Unstable loads A. Anakabe et al. Automatic Pole-Zero Identification for Multivariable Large-Signal Stability Analysis of RF and Microwave Circuits, 2010 European Microwaev Conference, Paris, September freq (1.000GHz to 1.000GHz) Stable mod and (0.693 unstable to 0.990) regions in the L plane for fin=500 MHz and Pin=17.1 dbm Slide 18 Stable loads

19 Imaginary Axis (MHz) Imaginary Axis (MHz) STAN Tool Monte-Carlo Example: L-Band medium power FET amplifier Low frequency instability related to the input bias network Stabilization by the inclusion of a gate-bias resistor R STAB Monte Carlo sensitivity analysis for different R STAB (5 % dispersion in all circuit parameters) R STAB = 44 0 R STAB = Real Axis (MHz) Real Axis (MHz) Slide 19

20 Q & A Contact Stéphane Dellier dellier@amcad-engineering.com Phone: Slide 20