Spurious and Stability Analysisunder Large-Signal Conditions

using your Vector Network Analyser

An application of ICE

June 2012

© NMDG 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 2012 3

Why combining Large-Signal and Small-Signal Measurements

S-parameters, usually measured under small-signal conditions, provide

S-parameters, measured under large-signal conditions, provide

● good insight in the linear behaviour of a amplifiers

● provide insight in the stability of the amplifier

SPURIOUS SIGNALS

INTERFERENCE

● good insight in what happens with spurious signals and interference signals

How to quantify impact from … ?

© NMDG 2012 4

Why combining Large-Signal and Small-Signal Measurements

S-parameters, usually measured under small-signal conditions, provide

S-parameters, measured under large-signal conditions, provide

● good insight in the linear behaviour of a amplifiers

● provide insight in the stability of the amplifier

● provide insight in the stability of the amplifier as conditions change

STABILITY

Z S

Z L

Under different large signal conditions … what about … ?

© NMDG 2012 5

Block Diagram

f0

Z L

`

Z SDUT

Network Analyzer Receivers

50 Ohm

VNA couplersor

external (low-loss) couplersVNA RF source 2 [similar to S-par measurement]

External RF source 1 orVNA RF source 1(depends on VNA)

Measure at large-signal frequency grid andat small-signal frequency grid, sweeping source 2

Absolute Calibration Planes

(*) (*)

(*) Other configurations possible, e.g. position couplers, use of splitters, depending on power requirements

Large SignalConditions

Large SignalConditions

“Measure S-par”

© NMDG 2012 6

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Practical Setup

FET Gate bias: -1.2 VDrain bias: 4 V

(class A)

Increasing input power and different terminations

ICE

External RF Source 1

Using VNA couplersTermination

Bias

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“Channel” capability of the ZVA 24

Large-Signal Measurements

Small-Signal Measurements

Using Rohde&Schwarz ZVA capability to configure different “channels”

Each channel has his own specific hardware configurationmeasured data

The Rohde&Schwarz ZVA switches fast from channel to channelZVA24 Display

© NMDG 2012 9

S-parameters under different large-signal conditions

2 4 6 8 10freq GHz

5

4

3

2

1

dBS11

2 4 6 8 10freq GHz

25

20

15

dBS12

2 4 6 8 10freq GHz

10

10

20

30

dBS21

2 4 6 8 10freq GHz

30

20

10

10

20dB

S22

5 dBm (open)5 dBm (load)0 dBm (load)NO RF signal

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Stability K-Factor and Determinant

2 4 6 8 10freq GHz

0.5

0.5

1.0

Abs U Kfact

2 4 6 8 10freq GHz

0.2

0.4

0.6

0.8

1.0

Abs U Determinant

5 dBm (open)5 dBm (load)0 dBm (load)NO RF signal

∣K∣1 and ∣∣1

Stability Conditions

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Input and Output Stability Circles

R0R0.5

R1.0R2.0

X2.0X1.0

X0.5

X0

X2.0X1.0

X0.5

R0

R0.5

R1.0

R2.0

X2.0

X1.0

X0.5

X0

X2.0

X1.0

X0.5

Input Output

Stable

Stable

5 dBm (load / open)

0 dBm (load)

NO RF signal

NO RF signal

0 dBm (load)

5 dBm (load / open)

Frequency: 4.2 GHz

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Large-Signal Conditions while measuring S-parameters

0.5 1.0 1.5 2.0time ns

2.0

1.5

1.0

0.5

Amp V v1t

0.5 1.0 1.5 2.0time ns

0.010

0.005

0.005

0.010Amp A i1t

0.5 1.0 1.5 2.0time ns

2

4

6

8

Amp V v2t

0.5 1.0 1.5 2.0time ns

0.05

0.10

0.15

0.20

0.25

Amp A i2t

5 dBm (open)5 dBm (load)0 dBm (load)

© NMDG 2012 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. 1663

● 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 2012 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

www.nmdg.be