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Reduction of the UncertaintyReduction of the Uncertainty on Noise Figure Measurements on Noise Figure Measurements

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1

INAF – Institute of Radioastronomy- Bologna – Italy

2

Elettronica s.p.a. – V. Tiburtina Valeria, Rome – Italy

3

University “Tor Vergata” – Electronic Eng. Dept. – Rome - Italy

Reduction of the Uncertainty Reduction of the Uncertainty

on Noise Figure Measurements on Noise Figure Measurements

A. Cremonini

1

, M. De Dominicis

2

, S. Mariotti

1

, E. Limiti

3

, A.Serino

3

(2)

WHY WHY

Reduce Uncertainty?

Reduce Uncertainty?

Uncertainty should be much lower than the value to be measured

3.5E-02

1E-13

5E-07

5E-03

1.E-14 1.E-12 1.E-10 1.E-08 1.E-06 1.E-04 1.E-02 1.E+00

Time Voltage RF Impedance Noise Figure

Absolute Uncertainty +/- 3.5 % = +/- 0.15 dB

For a receiver:

NF = 0.3 +/-0.15 dB

Te = 21 +/- 11 K

(3)

Looking for and Find Sources of Uncertainty (U)

How How

Reduce Uncertainty?

Reduce Uncertainty?

Analyze and propagate uncertainty

Minimize the sources wherever it is possible

Since U(ENR) is dominant, let do calibration of Noise Source with a Secondary Standard (liq. N

2

)

Let Practical operations accurate as possible

(4)

Involved Environments Involved Environments

Room Temperature

Room Temperature Cryogenic /on Dewar Cryogenic /on Dewar - easier

- faster

- accurate

- less jitter

- more realistic

- accurate

(5)

 

1

0.11 0.02 0.077 0.098

2 2 2 2

0.167

u NF

c

       dB

Sources (causes) of Uncertainty:

Sources (causes) of Uncertainty:

Propagation, Math Formulation Propagation, Math Formulation

12 1 2

1

1 F F F

G

  

     

   

2 2

2 12 2 2 2

1 12 2

1 1 1

2 2

2 2

2 12 2

1

1 1 1 1 1

1

c

dB dB

F F

u NF u NF u NF

F F G

F F F

u G u ENR

F G F F G

   

      

   

    

      

   

F

12

F

2

= 10dB F

1

= 3 dB

G

1

= 15 dB

Depend on many causes, even Depend on many causes, even U(ENR) U(ENR) Depend on

Depend on U(ENR) U(ENR)

(6)

Causes of Uncertainty:

Causes of Uncertainty:

Graphical - Intuitive Graphical - Intuitive

T

e

T

c

T

h

P

c

P

h

T

e

T

c

T

h

P

c

P

h

Reducing T

c

, will reduce U(T

e

)

T

e

T

c

T

h

P

c

P

h

Reducing U(T

h

) and U(T

c

) will reduce U(T

e

)

Increasing T

h

don’t reduce U(T

e

) , because U(T

h

)/T

h

is a constant

Instead increase T

h

may generate non-linearity . Yopt 2…5

(7)

Causes of Uncertainty:

Causes of Uncertainty:

Practical, Tips&Tricks Practical, Tips&Tricks

|S

11 ON

| , |S

11 OFF

| < - 33 dB Selected Attenuator

PT 100 A Cascade Ferrite Isolators

Environment: Thermostatic room, NO cables movement

Precision Connectors / Connector Care

Type A Uncert. << Type B Uncert.

10 dB

6 dB

(8)

Other causes of Uncertainty:

Other causes of Uncertainty:

Approximate Expression  T e

1

1  NS  DUT  2

1  290 T e

0.1 1.0 10.0 100.0

0 10 20 30 40 50 60 70

R.L. NoiseSource + R.L. DUT [dB ]

+/-

Te [oK ]

NSDUT

Mismatch: A closed form expression doesn’t exist

(9)

Liq. N2

77 K POWER METER

800 W

Liq. N2

77 K POWER METER

3200 W

Liq. N2

77 K POWER METER

9400 W

Liq. N2

77 K POWER METER

800 W

Liq. N2

77 K POWER METER

3200 W

Liq. N2

77 K POWER METER

9400 W

Principle of Operation 1/3 Principle of Operation 1/3

Noise Source +

Attenuator

(10)

Principle of Operation 2/3 Principle of Operation 2/3

1

Switch Isolators 2

LNA

Receiver

0 1

2

Px

02

01

M0,crio

Noise Source Ta–TH

77 K

7mm-K

M0,x

HP 8971C

HP 8970B

Pad 3dB

Att. Step 1dB Att. Step 10dB Cold Load

IF 20 MHz

Power Meter

PA PA

IF 6 dB

   

   eiso

crio x x

, crio ,

a crio

a

x T

Y Y M

T M T

T

T  

 

 1

1

02 0

01 0

Vector Correction

(11)

Pictures Pictures

•Coaxial 1-18 GHz

•WR 28

26.5-40 GHz

•WR 22

33-50 GHz

(12)

Data Analysis Data Analysis MatLab

MatLab ® ® codes has been used to: codes has been used to:

Process spar of non insertable Adapter Compute Mismatch and Available Gain

Instruments control and automatic data collection

Calculate ENR and associated Uncertainty

(13)

Uncertainty of the Result Uncertainty of the Result

       

     

21 '

2 2 2

2 2 2

0.0045 1.72 0.74 1.87 K

trans

crio crio Ta crio S crio T

u Tu Tu Tu T

   

          

       

2 2 2 2

2 2 2 2

18.0 1.83 8.68 23.5 30.9 K

hot hot s hot a hot Y hot S

u Tu Tu Tu Tu T

    

Uncertainty of VNA is dominant ( 0.045 dB - hp 8510C )

S par Uncertainty Depend on U(T

cryo

)

S par Uncertainty

(14)

Results and Results and

Associated Uncertainty Associated Uncertainty

U(ENR) was +/- 0.15 dB U(ENR) = +/- 0.06 dB

(15)

Spin-off for the LNAs Spin-off for the LNAs

80 100 120 140

18 20 22 24 26

Frequency [ GHz ] N o is e T em p er at u re [ K ]

Simulation

80 100 120 140

18 20 22 24 26

Frequency [ GHz ] N o is e T em p er at u re [ K ]

Simulation

Common U(ENR)

80 100 120 140

18 20 22 24 26

Frequency [ GHz ] N o is e T em p er at u re [ K ]

SimulationCommon U(ENR)

Low U(ENR)

(16)

WHAT can we do ? 1/3 WHAT can we do ? 1/3

• No possibility to further reduce ENR Uncertainty

• … but we may transfer our expertise to reduce ENR Uncertainty of other Noise Sources

•REQUEST and submit a PROPOSAL

• Need to share expensive Instruments (CryoLoad)

(17)

WHAT can we do ? 2/3 WHAT can we do ? 2/3

• PROPOSAL:

Comparition of Noise Figure Measurement

over community (better if even larger)

• As the IEEE “Round Robin”, an LNA will be sent to European Laboratories to be measured.

Each laboratory will perform measurement as usual and according to its own methodology

•Measured data will be compared and published

(18)

WHAT can we do ? 3/3 WHAT can we do ? 3/3

• LNA Bandwidth has been chosen to be a bridge between the

“easy” 1-18 GHz and the “difficult”

over 18 GHz.

• Freq. 16 – 26 GHz, Gain=27dB,

NF=1.6 dB (130K)

LNA

Power Supply

Euro Plug

(19)

Essential Bibliography Essential Bibliography

• [1] J. Randa, “Noise Temperature Measurements on wafer ” NIST Tech. Note 1390 03/1997

• [2] Agilent Technologies, “Noise Figure measurement accuracy – The Y-Factor method”, Application Note 57-2, 2001.

•[3] W.C. Daywitt, “Radiometer equation and analysis of systematic errors for the NIST automated radiometers”, National Institute of

Standards and Technology, Technical Note 1327, 03/1989.

•[4] C.T. Stelzried, “Temperature calibration of microwave thermal noise sources”, IEEE Transactions on Microwave Theory and Techniques (Correspondence), Vol. MTT-13, No. 1, 01/1965, pp. 128-130.

•[5] R.F. Bauer, P. Penfield, “De-Embedding and Unterminating”, IEEE Transactions on Microwave Theory and Techniques, Vol. 22, No. 3,

03/1974, pp. 282-288.

• [6] J.D. Gallego, “Accuracy of Noise Temperature Measurement of

Cryogenic Amplifiers”, - NRAO Int. Rep. No 285 jan. 1990.

(20)

Conclusions Conclusions

• The ENR of some Noise Sources has been calibrated.

• The Uncertainty related to ENR has been reduced from +/-0.15 dB typ to +/- 0.06 dB typ

•The calibration routine and the instrumental set-up may be repeated once again.

•Waveguide, millimeter cryoloads are needed to improve reliability

(21)

Thanks

Thanks

Riferimenti

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