Spurious and Stability Analysis under Large-Signal Conditions using your Vector Network Analyser

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1 Spurious and Stability Analysis under Large-Signal Conditions using your Vector Network Analyser An application of ICE June 2012

2 Outline Why combining Large-Signal and Small-Signal Measurements Block Diagram Practical Setup S-parameters Stability Criteria Large-Signal Measurements References and Acknowledgements Conclusions NMDG

3 Why combining Large-Signal and Small-Signal Measurements How to quantify impact from? SPURIOUS SIGNALS INTERFERENCE S-parameters, usually measured under small-signal conditions, provide good insight in the linear behaviour of a amplifiers provide insight in the stability of the amplifier S-parameters, measured under large-signal conditions, provide good insight in what happens with spurious signals and interference signals NMDG

4 Why combining Large-Signal and Small-Signal Measurements Under different large signal conditions what about? STABILITY Z S Z L S-parameters, usually measured under small-signal conditions, provide good insight in the linear behaviour of a amplifiers provide insight in the stability of the amplifier S-parameters, measured under large-signal conditions, provide provide insight in the stability of the amplifier as conditions change NMDG

5 Block Diagram Measure at large-signal frequency grid and at small-signal frequency grid, sweeping source 2 Large Signal Conditions f 0 ` Network Analyzer Receivers (*) (*) Z S DUT External RF source 1 or VNA RF source 1 (depends on VNA) Measure S-par VNA couplers or external (low-loss) couplers 50 Ohm Z L VNA RF source 2 [similar to S-par measurement] Large Signal Conditions Absolute Calibration Planes (*) Other configurations possible, e.g. position couplers, use of splitters, depending on power requirements NMDG

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7 Practical Setup Bias External RF Source 1 ICE Termination Using VNA couplers FET Gate bias: -1.2 V Drain bias: 4 V (class A) Increasing input power and different terminations NMDG

8 Channel capability of the ZVA 24 Using Rohde&Schwarz ZVA capability to configure different channels Each channel has his own specific hardware configuration measured data The Rohde&Schwarz ZVA switches fast from channel to channel ZVA24 Display Large-Signal Measurements Small-Signal Measurements NMDG

9 S-parameters under different large-signal conditions db S freq GHz 15 db S12 NO RF signal 0 dbm (load) 5 dbm (load) 5 dbm (open) freq GHz 30 db S21 20 db S freq GHz freq GHz NMDG

10 Stability K-Factor and Determinant Abs U Kfact Abs U 1.0 Determinant freq GHz freq GHz Stability Conditions K 1 and 1 NO RF signal 0 dbm (load) 5 dbm (load) 5 dbm (open) NMDG

11 Input and Output Stability Circles Input NO RF signal Output 5 dbm (load / open) 0 dbm (load) X 0.5 X 1.0 R 0 X 2.0 R 0.5 R 1.0 R 2.0 Stable X 0 X 0.5 X 1.0R 0 X 2.0 R 0.5 R 1.0 R 2.0 X 0 Stable 5 dbm (load / open) NO RF signal X 0.5 X 2.0 X 1.0 X 0.5 X 2.0 X dbm (load) Frequency: 4.2 GHz NMDG

12 Large-Signal Conditions while measuring S-parameters Amp V v1 t Amp V time ns 8 v2 t dbm (load) 5 dbm (load) 5 dbm (open) Amp A i1 t Amp A i2 t time ns time ns time ns NMDG

13 References and Acknowledgements A New Characterization Technique of Four Hot S-parameters for the Study of Nonlinear Parametric Behaviors of Microwave Devices, T. Gasseling, D. Barataud, et alii, 2003 IEEE MTT-S Digest, p Thanks to Rohde & Schwarz for providing the R&S ZVA network analyzer equipment and the support around the network analyzer Thanks to Focus Microwaves for providing the tuners and the good cooperation NMDG

14 Conclusions It is straightforward with a Rohde & Schwarz network analyzer to measure the small-signal behaviour while applying and measuring the large-signal conditions With the S-parameters it is possible to get better insight when spurious signals are applied to the component or interference signals are picked up, e.g. RF front-end picking up signals The S-parameters result in different stability criteria. This is evenly important as the large-signal performance, designing active circuits, like amplifiers For more information info@nmdg.be NMDG