A Survey of Load Pull Simulation Capabilities – How do they Help You Design Power Amplifiers? 1 Agilent EEsof EDA IMS 2010 MicroApps Andy Howard Agilent Technologies May 19, 2010 Outline • Power amplifier design questions • Basic load pull concepts • Fast, simple load pull • Adding power sweeps to see compression • Constant power-delivered load pull • Constant power-delivered source pull • Using two input tones to see intermodulation distortion • Load pull with a WCDMA source 2 May 19, 2010 Power amplifier design questions: What’s the best load? How does the bias point affect performance? Do I need to add stabilization networks? What about device size or # of cells? Can I get a particular output power from a device? How far into compression when delivering that power? Many different loads satisfy the output power requirement. How do I choose the best one? What about the load impedance at harmonic frequencies? How do I choose the best source impedance? How does the optimal load impedance vary with frequency? With other swept parameters? What is an efficient approach for running load pull simulations? What signal source should I use when running load pull? 3 May 19, 2010 Load pull concept Two main techniques Available source power held constant Available source power optimized 4 Power delivered held constant May 19, 2010 Load pull concept 5 May 19, 2010 Some preliminaries: biasing and stability Choose bias point based on class of operation or vendor/ foundry recommendation Add feedback for stability, as needed 6 May 19, 2010 Start with fast, simple load pull Available source power held constant Source Power = 5 dBm 7 Source Power = 12 dBm May 19, 2010 Focusing on a smaller region of the Smith Chart Source Power = 12 dBm 8 May 19, 2010 Add power sweeps to see compression At each load reflection coefficient, also sweep available source power. 9 May 19, 2010 Compression curves at maximum output power and maximum PAE loads 10 May 19, 2010 Constant power-delivered load pull You specify the power to be delivered to the load. For each reflection coefficient the available source power is optimized. Available source power optimized 11 Power delivered held constant May 19, 2010 Contours are all with same power delivered Power delivered=27 dBm 12 May 19, 2010 Do you want maximum PAE or minimum gain compression? 13 May 19, 2010 Results with delivered power goal set to 28 dBm 14 May 19, 2010 Do you want maximum PAE or minimum gain compression? (Pdel_dBm = 28 dBm) 15 May 19, 2010 Run source pull to improve gain Chose load for maximum PAE from previous simulations 16 May 19, 2010 Choose source Z for maximum gain or minimum gain compression 17 May 19, 2010 What else could you simulate? • Performance versus frequency • Performance with two input tones • Performance with modulated input signals • Performance versus some other swept parameter • Performance versus harmonic load impedance 18 May 19, 2010 Two-tone swept power load pull 19 May 19, 2010 Two-tone swept power load pull Available source power swept from -10 to +12 dBm 20 May 19, 2010 Constant power delivered load pull with two tones 21 May 19, 2010 Do you want to maximize PAE or minimize intermodulation distortion? 22 May 19, 2010 Load pull with WCDMA signal Read modulated data from file. Scale signal amplitude by Filter bank at amplifier optimizing “SFexp” variable. output for computing ACLRs. 23 May 19, 2010 ACLR and PAE contours Power delivered set to 27 dBm 24 May 19, 2010 Do you want to maximize PAE or minimize ACLR? 25 May 19, 2010 Review • Power amplifier design questions • Basic load pull concepts • Fast, simple load pull • Adding power sweeps to see compression • Constant power-delivered load pull • Constant power-delivered source pull • Using two input tones to see intermodulation distortion • Load pull with a WCDMA source 26 May 19, 2010 For more information: On the latest release of ADS: http://www.agilent.com/find/eesof-ads Supported ADS customers may download an updated Load Pull DesignGuide with all these simulation setups from our Knowledge Center: http://edocs.soco.agilent.com/display/eesofkc/ Loadpull+DesignGuide+for+ADS+2009+Update+1+with+new+content Please view our load pull videos: http://www.youtube.com/watch?v=FTK1pEu1Z64 27 May 19, 2010