the impact or cables and connectors on measurement uncertainty · measurement” 58 connectors...

1

The Impact or Cables and Connectors On Measurement Uncertainty

Dennis Lewis

BOEING is a trademark of Boeing Management Company.Copyright © 2009 Boeing. All rights reserved.

Dennis LewisThe Boeing company

Associate Technical Fellow RF / Microwave and Antenna Metrology

P.O. Box 3707 MC 19-LLSeattle WA, 98124-2207

[email protected]

AgendaConnector Overview

Measurement Uncertainty EvaluationsMeasurement Uncertainty Evaluations

Mismatch

Error

Correction

Correction Uncertainty

BOEING is a trademark of Boeing Management Company.Copyright © 2009 Boeing. All rights reserved. 2

Connector and Cable Effects

Example

2

Connector Specifications

Characteristic Impedance

Connector Overview

Characteristic Impedance

Insertion Loss

Frequency Range

GRADESMetrology


Metrology

Instrument

Production (Field)

D = Inner diameter of

Model for Characteristic Impedance, Z (Low-Loss Case)

D60

Connector Overview

D = 7.0 mm

D Inner diameter of outer conductor

d = Outer diameter of inner conductor

d

DZ

r

ln60

0


Dd d = 3.04 mm

ohms 500 rZ

Courtesy of Agilent Technologies

3

Frequency Coverage

Connector Overview

fmax(GHz) = approx. 120/D mm

7 mm = approx. 18 GHz3.5 mm = 32 GHz

Ratio D/d constant

Depends strongly on dielectric support and mating pin geometry

Dd



Depends strongly on dielectric support and mating pin geometry

Connector Overview


4

Connector Overview


Connector Overview



5

Some Precision Metrology Grade Adapters

N(f)-3.5(m) N(f)-3.5(f)

Connector Overview

N(m)-3.5(f) N(m)-3.5(m)


7mm-3.5(f) 7mm-3.5(m) 3.5(m)-3.5(m) 3.5(f)-3.5(f)


1.0 mm Coaxial Adapters (110 GHz)

Connector Overview



6

1.0 mm Launch Adapter

Connector Overview


For Coax to Microstrip, pin diameter = 0.162 mm 11923A


IEEE P287 Working Group

Connector Overview


Maury Microwave:COLORCONNECT PRECISIONADAPTERS

7

Slotted Female Center Conductor Slotless Female Center Conductor

Connector Overview



Damage From ProtrusionPin Recession

Connector Overview



Increased uncertainty from recession

8

Connector Overview


Connector Overview

3.5 mm vs. SMA


9

Connector Metrology Instrument Production Cutoff Freq (GHz)

Sexed Precision Slotted Connector

Type F(75) N N Y 1 Y N

Connector Overview

yp ( )

BNC (50 & 75) N N Y 2 Y N

SMC N Y N 7 Y N

Type-N (50 & 75) Y Y Y 18 Y Y

APC-7 or 7 mm Y Y Y 18 N N

SMA (4.14mm) N N Y 22 Y N

3.55 mm Y Y Y 34 Y Y

2.92 mm or "K" N Y Y 44 Y N

2.4 mm Y Y Y 52 Y Y

1 85 mm N Y Y 70 Y N

1

2

2 3


1.85 mm N Y Y 70 Y N

1.0 mm N Y Y 110 Y N

1. Compatible with SMA and 3.5 mm connectors.2. Not compatible with SMA, 3.5 or 2.92 mm connectors3. Compatible with 2.4 mm connector

2, 3

Reference: Agilent Microwave Test Accessories Catalog , 1992-1993 pp. 14, 15.

N t d t d

Handling

Connector Overview

Never stand connectors on end

Use protective caps

Don’t touch

If dropped re-inspect

A id t t t t


Avoid stress on test port

Don’t over torque

Don’t spin connectors (center conductors)

10

O l 99 5% I l l h l ( ll t )

Cleaning

Connector Overview

Only use 99.5% Isopropyl alcohol (small amounts)

Avoid direct pressure on center conductor

Use clean dry low pressure air

Use appropriate sized toothpick and lint free cloth

Clean connector threads holding connector upside


down

B t fi d fi

Inspecting

Connector Overview

Bent fingers or spread fingers

Offset center conductor

Dirt

Foreign objects

B d th d


Bad threads

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Using the Torque Wrench

Connector Overview


Using a Second Torque Wrench

Connector Overview


12

Connector Gauging




Mismatch

Error

Correction




Examples

13

Measurement Uncertainty Evaluations

Worst Case - Add all contributing errors

)()()(U

RSS – Root Sum Square of all contributing errors

)...()()( 321 xuxuxuU wc

i iRSS xuU 2)(


ISO Guide to Uncertainty in Measurement (GUM)

26

)()( 2

2

1

2i

n

i ic xu

x

fyu

V 2 PMeasurement Equation Sensitivity Coefficients

Measurement Uncertainty Evaluations

R

VP

)(1)(2)( 222 RuVuPu

1

2

RP

VVP

Combined Standard uncertainty


)(

)(1)(2)(

yukU

RuVuPu

c

c

k= Coverage Factor1= 68.27%2=95.45%3=99.73%

Expanded Uncertainty

14



Mismatch

Error

Correction




Examples

Mismatch

Distribution of Uncertainties

15%

50%Mismatch

Instrumentation

Environment


35%

15

Mismatch

Mismatch Error vs. Mismatch Correction

21 G SMM

The mismatch corrections for a source and one load is given by:

je

The worst-case uncertainty in the case where no phase data is available is


given by:

2

1 1100 1 1errMM

Mismatch

2C l C j t

Given phase information a better estimate of the magnitude uncertainty is as follows:

1 2 1 2

1 2 1 2 1 2 1 2

j -j

2

1 2 1 2 1 2

2 2 2

Complex Conjugate

Euler's Rule

e +ecos =

2Using the above to simplify equation (1)

1- 1 1

1 1

j

j

j j

j j j j

e

e

e e


1 2 1 2 1 2 1 22 21 2 1 2 1 2 1 21- 1

1-

j j j je e e e

1 2 1 2

1 2

2 2 21 2 1 2 1 2

2cos

2 2 21 2 1 2 1 2 1 2

1

The mismatch correction for a source and one load is given by:

MM 1- 1 2 cos

j je e

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Mismatch

2 22 2

2 2 2 2MM MM MM MM

The combined standard uncertainty for the mismatch is:

2 2 2 2

S L S LMM PS L S L

MM MM MM MMU

22 cos( ) 2L S L S LS

MM

22 cos( ) 2S S L L SL

MM


L

2 sin( )S L L S LS

MM

2 sin( )S L S S LL

MM

Mismatch

Example: VSWR <1.02Converting SWR to Reflection coefficient as follows:

1 1 1.02 0.020.01

1 1 1.02 2.02

VSWR

VSWR

Substituting ρ into Equation 1

2

1 1100 1 1UncMM


2

2

100 1 (0.01)(0.01) 1

100 1 (0.01)(0.01) 1 0.02%

Unc

Unc

MM

MM

17

Mismatch

Example: VSWR <1.2Converting SWR to Reflection coefficient as follows:

1 1 1.2 0.20.091

1 1 1.2 2.2

VSWR

VSWR

Substituting ρ into Equation 1

2

1 1100 1 1UncMM


2

2

100 1 (0.091)(0.091) 1

100 1 (0.091)(0.091) 1 1.65%

Unc

Unc

MM

MM



Mismatch

Error

Correction




Example

18



Not all connectors are created equal!


Reverberation Chamber Field Uniformity

Chamber Troubleshooting

1.5

2.0

2.5

3.0

dB

rel

. to

mea

n)

4 Finger Connector

Vents Not covered

Vents Covered/ 8 fingerConnectors


0.0

0.5

1.0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

GHz

F. U

. (d

19


Connector Bends



Connector Bends

Uncorrected Data Comparison

-8

-6

-4

-2

0

2

dB

Type N (6 Finger)SMA


-14

-12

-10

45 18000

Freq (MHz)

20

20

0

Gasket Effects


-120

-100

-80

-60

-40

-20

1.4

2.6 3.6 4.6

5.6 6.6 7.6

8.6

9.710.

711

.7

GHz

dB

With Gasket

Without Gasket



Cable Crosstalk


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Cracked Semi-ridged cables




22





Mismatch

Error

Correction




Example

23

Standard Field Method TEM Cell Reverberation Chamber

Net Input Power

Chamber


2

30( / ) t NETG P

E V mR

net 0P ZVE(V/M)= =

h h

2

12

2

22

NET

SP =

1- S

Net Input Power

21MM 11 LGMM

Source VSWR = 1.8 (0.29)

Load VSWR = 1.2 (0.09)


Mismatch Error = 5.2%

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Net Input Power

21 SGMM

2

1 UG

SGMM


Load VSWR = 1.2 (0.09)Sensor VSWR = 1 2


Sensor VSWR = 1.2

Mismatch Error = 0%

Net Input Power

21 SGMM

2

1 UG

SGMM


Load VSWR = 1.2 (0.09)Sensor VSWR = 1 02


Sensor VSWR = 1.02

Mismatch Error = 4.8%

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Net Input Power

21 SGMM

2

1 UG

MM


0 1 2NET fwd revP C P C P

Example - Dual Directional Coupler

PM1 PM2

Power Meter

0 1 2NET fwd rev

2

34

2

13

fwd

SC

S

2

24

1revC

S

Forward3 4

1 2

Source

Reverse

Input Output

Antenna


0

2

34 1 22 2 2 2

13 1 24 2

1

1 1NET

S P PP

S S

26

Net Power Expression Based On Full S-parameters

S S S S


11 12 13 14

21 22 23 24

31 32 33 34

41 42 43 44

S S S S

S S S SS

S S S S

S S S S

2

13 22 2 12 23 2

23 11 1 12 13 1

(1 )

(1 )

A S S S S

B S S S S

0

2

34 1 22 2 2 2

13 1 24 2

1

1 1NET

S P PP

S S


22 22 41

2 2

1 21 1NET

PPP G H

13 24 14 23 4

13 44 4 14 34 4

34 11 1 13 14 1

13 24 12 34 2

( )

(1 )

(1 )

( )

/

/

C S S S S

D S S S S

E S S S S

F S S S S

G FB AE DA FC

H BF AE BD EC

Net power uncertainty using Law of Propagation of Uncertainty

2PP


12 23 2 23 11 1 12 13 1 13 24 14 23 2

13 22 2 13 22 2 12 23 2 34 11 1 13 14 122 2

14 23 23 11 1 12 13 1 13 44 4 14 34 424 4

13 24 34

[ (1 ) ]( )1 1

(1 ) [ (1 ) ][ (1 ) ]11( , )

[ (1 ) ][ (1 ) ]1 1

[ (

S S S S S S S S S S

S S S S S S S S S SSH S

S S S S S S S S S SSS S S

11 1 13 14 1 13 24 14 23 41 ) ][( ) ]S S S S S S S

2 22 412 2

1 21 1NET

PPP G H


3 3 3 3 3

16 S-parameters, 1, 2 , 4 Magnitude and Phase

27

For a complicated model equation, it may not even be practical to take the Partial derivatives.

Monte Carlo Method

p

GUMS1 – “Evaluation of measurement data —Supplement 1 to the GUM - Propagation of distributions using a Monte Carlo method” gives a practical way to deal with the situation.


Monte Carlo Method

MCM – Method for the propagation of distributions by performing random sampling from probability distributions

R d l d f h i i bl b d hRandom values are generated for the input variables based on the assigned distributions.

They are fed to the model equation. The results are based on the inputs, which gives us a range (U).


28

References

IEEE 287 Standard for Precision Coaxial Connectors (DC to 110 GHz)

Connector Care for RF and Microwave Coaxial Connectors

– HP Part No. 08510-90064

ANAMET Report 032 “Guidance on Using Coaxial Connectors in Measurement”

“GUM” – Guide to the Expression of Uncertainty in Measurement, published by ISO/IEC


NIST Technical Note 1297 “Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results”

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Summary

Not all connectors are created equal

Consider requirements when selecting cables andConsider requirements when selecting cables and connectors

Mismatch Uncertainty can be the most significant contribution to overall measurement uncertainty

Cables performance shouldn’t be neglected (verified)

Damaged connectors can impact impedance and


therefore uncertainty

Monte Carlo Method is useful when evaluating uncertainties described by complex measurement equations

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Questions?


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