A Survey of Load Pull Simulation Capabilities How do they Help You Design Power Amplifiers?

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1 A Survey of Load Pull Simulation Capabilities How do they Help You Design Power Amplifiers? Agilent EEsof EDA IMS 2010 MicroApps Andy Howard Agilent Technologies 1

2 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

3 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

4 Load pull concept Two main techniques Available source power held constant Available source power optimized Power delivered held constant 4

5 Load pull concept 5

6 Some preliminaries: biasing and stability Choose bias point based on class of operation or vendor/ foundry recommendation Add feedback for stability, as needed 6

7 Start with fast, simple load pull Available source power held constant Source Power = 5 dbm Source Power = 12 dbm 7

8 Focusing on a smaller region of the Smith Chart Source Power = 12 dbm 8

9 Add power sweeps to see compression At each load reflection coefficient, also sweep available source power. 9

10 Compression curves at maximum output power and maximum PAE loads 10

11 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 Power delivered held constant 11

12 Contours are all with same power delivered Power delivered=27 dbm 12

13 Do you want maximum PAE or minimum gain compression? 13

14 Results with delivered power goal set to 28 dbm 14

15 Do you want maximum PAE or minimum gain compression? (Pdel_dBm = 28 dbm) 15

16 Run source pull to improve gain Chose load for maximum PAE from previous simulations 16

17 Choose source Z for maximum gain or minimum gain compression 17

18 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

19 Two-tone swept power load pull 19

20 Two-tone swept power load pull Available source power swept from -10 to +12 dbm 20

21 Constant power delivered load pull with two tones 21

22 Do you want to maximize PAE or minimize intermodulation distortion? 22

23 Load pull with WCDMA signal Read modulated data from file. Scale signal amplitude by optimizing SFexp variable. Filter bank at amplifier output for computing ACLRs. 23

24 ACLR and PAE contours Power delivered set to 27 dbm 24

25 Do you want to maximize PAE or minimize ACLR? 25

26 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

27 For more information: On the latest release of ADS: Supported ADS customers may download an updated Load Pull DesignGuide with all these simulation setups from our Knowledge Center: Loadpull+DesignGuide+for+ADS+2009+Update+1+with+new+content Please view our load pull videos: 27

Welcome. Steven Baker Founder & Director OpenET Alliance. Andy Howard Senior Application Specialist Agilent EEsof EDA Agilent Technologies, Inc.

Welcome. Steven Baker Founder & Director OpenET Alliance. Andy Howard Senior Application Specialist Agilent EEsof EDA Agilent Technologies, Inc. Welcome Steven Baker Founder & Director OpenET Alliance Andy Howard Senior Application Specialist Agilent EEsof EDA 1 Outline Steven Baker, OpenET Alliance What problem are we trying to solve? What is