noise figure measurement with spectrum analyzer and vector

Frédéric Molina19/03/2019

Noise Figure measurement with Spectrum analyzerand Vector Network Analyzer

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Agenda

ı Background and theory

ı Measurement method : Spectrum analyzer

ı Measurement method : Vector Network Analyzer

ı Measurements uncertainty

ı Conclusion

19/03/2019 2Noise Figure measurement with Spectrum analyzerand Vector Network Analyzer

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• N=k*T (Watt/Hz) k = Boltzmann’s constant=1.38 x 10-23 Joules/K and T = temperature in Kelvin Special Case: kTo where To = room temperature (293 K = 20 °C) : -174 dBm/Hz

• Over a certain bandwidth, we use : kT * B

• Example: What is the thermal noise floor in a 1 MHz BW?

Thermal Noise


Answer:-174 dBm/Hz + 10*LOG(1MHz/1Hz)= -174 dBm/Hz + 60 dB= -114 dBm

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This is the IEEE standard definition of Noise Factor

Noise Factor Definition

Gin

in

NS

+

Na

Noise Figure (dB) = 10*LOG(F)

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in

in

NS

ain

in

out

out

NGNGS

NS

out

out

NS

Ga

Ga + Na


NoiseFactorF

SinNinSoutNout

KT0B*G NaKT0B*G

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Noise Temperature

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Noise Factor F Noise Figure NF Noise Temperature1 0 dB 0K (absolute zero)

1.12 0.5 dB 35.4 K1.26 1 dB 75.1 K

2 3 dB 288.6 K3.16 5 dB 627 K10 10 dB 2610 K

Noise Temperature :


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Friis Equation

(linear terms, not dB)

Noise Figure of Cascaded Components

G1Na1

G2Na2

Nin

Nin NinG1

Na1NinG1G2

Na2

Na1G2

1

21

1G

FFF

Stage 1 (attenuator)

Stage 2(amplifier)

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Stage 2(attenuator)

Stage 1(amplifier)

Or


T T1T2G1

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Measurement methodsı 1) Noise Figure Meter:

Accurate, allow to measure low Noise Figure Expensive instruments and limited in frequency

ı 2) Power method:

Valid for high NF The noise floor of the analyzer must be very low

1. Gain Measurement2. Pout Measuremnt3. NF calculation

noise figure meter DUT noise-meas.-equip.

input noise is known

))log(10174( GBPNF HzdBm

out


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Agenda





ı Conclusion


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Method 3 : Y-Factor method with Spectrum Analyzer

ı Y-Factor Method: Valid for all NF values A known noise source must be commuted to 2 known temperatures values

ENR is for T0 @ 50 ohms Source & DUT Connection Accuracy is significantly impacted

Bias Input28 V DC

Matching Pad-16 dB

AvalancheDiode

BIAS control

Noise OutputENR typ. 15 dBequiv. 9460 K

The noise source has a level output calibrated = Excess Noise Ratio

The ENR are delivered with the noise source and are validated at T0 = 290K = 16.85°C]/)log[(10 0TTTENR off

son

s


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Method 3 : Y-Factor method with Spectrum AnalyzerOption FSx-K30

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DUT

USB +

28V Control connection R&S Smart Noise Source

FS-SNxx (up tp 55GHz)


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ı 1- During calibration step, the ENR of the noise source has to be at least 3dB higher than the noise figure of the spectrum analyzer:

ı 2- During measurement step, the ENR of the noise source has to be at least 5dB higher than the noise figure of the DUT:

ı 3- The noise figure of the DUT + the gain of the DUT is at least 1dB greater than the noise figure of the spectrum analyzer :

Guide line : Selecting a Spectrum Analyzer and Noise Source


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Measurement procedure

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G+

Na

Step 1 : 2nd Stage calibration (spectrum calibration)

Step 2 : DUT Measurement


• Measure : 2 noise temperatures• Calculate NFSA

• Measure : 2 noise temperatures• Calculate Gain DUT• Calculate NFDUT+SA

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Step 1 : 2nd Stage Calibration (detail)

1. Connect noise source direclty to Spectrum Analyzer

2. Two measurements are performed : Noise source OFF and ON : NSAOFF and NSAON

3. Calculate Y-Factor of the spectrum Analyzer

4. Calculate Noise temperature and noise figure of spectrum analyzer

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OFFsourceT

ONsourceT


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Step 2 : DUT measurement (detail)

1. Add the DUT between the noise source and Spectrum Analyzer

2. Two measurements are performed Noise source OFF and ON = NDUT&SAOFF and NDUT&SAON

3. Calculate Y-Factor of the DUT and spectrum Analyzer

4. Calculate Noise temperature and noise figure of spectrum analyzer

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G+

NaOFF

sourceT

ONsourceT


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DUT GAIN and NF Final calculation


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Noise Figure and Gain results


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Specific measurement 1 : Noise figure above 110 GHz


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Specific measurement 2 : Pulsed Noise Figure measurements


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Agenda





ı Conclusion


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Method 4 : using Vector Network Analyzer(Option ZNA-K30 or ZVA-K30, and K31 for mixer measurement)

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DUT


Measurement with two detectors : RMS and AVG

RMS detector : ‘signal + noise’AVG detector : ‘signal’ and ZNA

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Noise = (S+N)-S

-6

-4

-2

0

2

4

6

8

10

time

ampl

itude

signalAVG PP ̂noisesignalRMS PP ̂

Signal + Noise

-40

-30

-20

-10

0

10

20

30

40

time

ampl

itude −

Signal

-40

-30

-20

-10

0

10

20

30

40

time

ampl

itude

Signal+Noise Power Signal Power

Noise Power

RMS detector AVG detector

Noise figure measurement with Vector Network Analyzer


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Calibration Step 1 : Port 1 reference receiver calibration and source flatness

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Port 1 ref. plane

USB connexionPower Sensor

22Noise Figure measurement with Spectrum analyzerand Vector Network Analyzer

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Calibration Step 2 : Port 2 receiver power and noise source calibration

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Ports 1 & 2 ref. planes


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Calibration Step 3 : Receiver noise calibration

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MATCH

Port 2 ref. plane

l Noise floor of port 2 must be measuredl The noise generated by the match is -174dBm/Hz @ 290K


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Calibration Step 4 : Attenuator calibration

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l An additional attenuator must be activated in order to compensate the gain of the DUT, to avoid any compressionl The attenuator can be internal or externall This attenuator must be measured


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Calibration Step 5 (Optional) : S-Parameters calibration

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26

OPEN

SHORT

MATCH

THROUGH


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Measurement

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DUTNoise figure calculation :

output

inputDUT SNR

SNRNF log10

measNF

noise

signal

dataCAL

noise

signal

output

output

input

input

P

P

P

P

::

log10log10


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Noise Figure & gain results


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Agenda





ı Conclusion


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Comparison of both method result


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Measurement uncertainty (for both methods)

ı Uncertainty can be calculated : Worst case scenario by adding up all the contributions to the overall uncertainty Using the Root of the Sum of the Squares (RSS) approach. In general, when the contributions are independent from each other, the RSS approach is utilized in practice as a more realistic bound on uncertainty. In a noise figure uncertainty calculation the contributions are independent making the RSS approach the appropriate selection.

ı Several factors contribute to noise figure measurement uncertainty : Noise figure of the analyzer (spectrum or vector network analyzer) Uncertainty of the noise source ENR value (for spectrum analyzer) Uncertainty of power meter (for vector network analyzer) Gain of the DUT (significant impact) Impedance mismatches between noise source and DUT


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Uncertainty comparison – Case 1DUT = Amplifier (Gain=20dB/NF=1.8dB) and ENR uncertainty for Noise Source=0.2dB

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Y Factor Method - Spectrum Analyzer Vector Network Analyzer


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Measurement setup (in case of DUT Gain too small)

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DUT DUT

Basic Setup Setup for LNA test

Preamp


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Measurement setup (in case of DUT Gain too small)

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DUT

Reverse coupler

DUT


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Uncertainty integrated on spectrum analyzer


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Agenda





ı Conclusion


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Conclusion

ı Spectrum Analyzer : Easy to operate : only 2 steps : 2nd stage calibration and Measurement Need only the Noise Source Works up to 500GHz with external mixers Works in pulses conditions

ı Vector Network Analyzer : Don’t need a Noise Source (Avoid mismatch uncertainty) S-Parameters can be measured at the same time Mismatch can be calibrated and corrected


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For further reading….

19/03/2019

1EF1031MA178 1EZ61


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noise figure measurement with spectrum analyzer and vector

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