Extension of Attenuation Measurement range Extension of Attenuation Measurement range in Intermediate Frequency (IF) substitution in Intermediate Frequency (IF) substitution

and Vector Network Analyzer techniquesand Vector Network Analyzer techniques  Kamlesh Patel*Kamlesh Patel*, P.S. Negi and P. C. Kothari, P.S. Negi and P. C. Kothari

Electrical & Electronics Standards Electrical & Electronics Standards National Physical Laboratory (CSIR)National Physical Laboratory (CSIR)

New Delhi, India New Delhi, India

kpatel@nplindia.orgkpatel@nplindia.org

22

ATTENUATIONATTENUATION STANDARDSSTANDARDS

30 MHz WBCO 30 MHz WBCO attenuatorattenuator

Inductive Voltage Inductive Voltage Divider (IVD) Divider (IVD)

Operated at 10 kHz Operated at 10 kHz or 1 kHz usuallyor 1 kHz usually

33

ATTENUATION STANDARDS AND ATTENUATION STANDARDS AND TECHNIQUESTECHNIQUES

S.No.S.No. Standard/ Standard/ TechniqueTechnique

Waveguide System Waveguide System

(2.6 – 18 GHz)(2.6 – 18 GHz)

Coaxial SystemCoaxial System

(30MHz & 1-18 GHz)(30MHz & 1-18 GHz)

1.1. PrimaryPrimary i. 30MHz WBCO Attenuatori. 30MHz WBCO Attenuator

Resolution:0. 001dBResolution:0. 001dB

Accuracy:Accuracy: 0.005dB/10dB 0.005dB/10dB

Make: NIST, USAMake: NIST, USA

ii. Audio Attenuatorii. Audio Attenuator

Resolution: 0.002dBResolution: 0.002dB

Accuracy:Accuracy: 0.02dB/30dB 0.02dB/30dB

Make: WE, USAMake: WE, USA

i. 30MHz WBCO attenuatori. 30MHz WBCO attenuator

Resolution:0. 001dBResolution:0. 001dB

Accuracy: Accuracy: 0.005dB/10dB 0.005dB/10dB

    Make: NIST, USAMake: NIST, USA

ii. Audio attenuatorii. Audio attenuator

Resolution: 0.002dBResolution: 0.002dB

Accuracy:Accuracy: 0.02dB/30dB 0.02dB/30dB

Make: WE, USA Make: WE, USA

2.2. Transfer Transfer i. Parallel IF substitutioni. Parallel IF substitution

Uncertainty: Uncertainty: 0.02 dB/10 dB 0.02 dB/10 dB

Range: 60 dBRange: 60 dB

ii. Dual Channel AF substitutionii. Dual Channel AF substitution

Uncertainty:Uncertainty: 0.02 dB/10 dB 0.02 dB/10 dB

Range: 30 dBRange: 30 dB

i. 30MHz series substitutioni. 30MHz series substitution

Uncertainty:Uncertainty: 0.007 dB/10 dB 0.007 dB/10 dB

Range:100 dB Range:100 dB

ii. Parallel IF substitution ii. Parallel IF substitution

iii. Dual Channel AF iii. Dual Channel AF substitutionsubstitution

3.3. ReferenceReference Fixed & variable attenuatorFixed & variable attenuator

Rotary vane attenuatorsRotary vane attenuators

Calibration equipmentsCalibration equipments

Fixed & variable Fixed & variable (Step/continuous) attenuators(Step/continuous) attenuators

Calibration equipmentsCalibration equipments

44

IF SUBSTITUTION TECHNIQUEIF SUBSTITUTION TECHNIQUE

Block diagram of I.F. substitution technique

Master Oscillator Isolator No.1 Tuner No.1 DUT Isolator No.2Tuner No.2

RF mixer

A B

B’A’

Local Oscillator

VM-7

10 MHz reference signal

WBCO attenuator( 0,005dB/10dB)

55

TWO–PORT VECTOR NETWORK TWO–PORT VECTOR NETWORK ANALYZER TECHNIQUEANALYZER TECHNIQUE

VNA based measurement set up and Wiltron VNA model 37247B

V N A

DUT

Port 1 Port 2

66

-10 0 10 20 30 40 50 60 70 80 90

0.004

0.006

0.008

0.010

0.012

E

xpa

nd

ed

Un

cert

ain

ity

Measured Attenuation (dB)

Exploration of the uncertainties Exploration of the uncertainties for WBCO attenuatorfor WBCO attenuator

77

TABLE I. UNCERTAINTY BUDGET FOR IF SUBSTITUTION TECHNIQUETABLE I. UNCERTAINTY BUDGET FOR IF SUBSTITUTION TECHNIQUE

Frequency: 18,0 GHz Frequency: 18,0 GHz Measured Attenuation: 79,449 dBMeasured Attenuation: 79,449 dB Source of

uncertaintyEstimate

(± dB)Probability Distribution

TypeA/B

Sensitivity coefficient

Standard uncertainty

(dB)

Repeatability 0,1273 Normal A 1,0 0,0569

Reference Standard attenuator

0,04 Normal B 1,0 0,02

Resolution 0,0005 Rectangular B 1,0 0,00029

Mismatch uncertainty

0,015 U-shaped B 1,0 0,1061

MixerNon linearity

0,065 Rectangular B 1,0 0,03753

Mixer Noise 0,1 Rectangular B 1,0 0,05774

Combined uncertainty 0,098774

Expanded uncertainty (k = 2) 0,181

88

TABLE II. UNCERTAINTY BUDGET FOR TWO-PORT VNA TECHNIQUETABLE II. UNCERTAINTY BUDGET FOR TWO-PORT VNA TECHNIQUE

Frequency: 18,0 GHz Frequency: 18,0 GHz Measured Attenuation: 79,203 dBMeasured Attenuation: 79,203 dBSource of

uncertaintyEstimate

(± dB)Standard

uncertaintyType A/B

Probability Distribution

Sensitivity coefficient

Uncertainty Contributions

(± dB)Repeatability 0,4 0,4 A t-distribution 1.0 0,126491

Linearity 0,1 0,1 B Rectangular 1.0 0,05

Test port Match 0,07433 3,89732E-05 B

 Load Match 0,012589 0,000148662 B

Test port*Load Match

0,000936 0,000935764 B

Mismatch calculated

  0,000187942 B U-shaped 1.0 0,000133

Cross-talk 0,27042 0,27042 B Gaussian 1.0 0,156132

System Repeatability

0,095354 0,09535424 A Gaussian 1.0 0,047677

Noise 0,05 0,05 B Gaussian 1.0 0,025

Cable fixture 0,0003 0,0003 A Gaussian 1.0 0,00015

Ambient Conditions

0,02 0,02 B Rectangular 1.0 0,011547

Connector Repeatability

0,085898 0,085898001 A Gaussian 1.0 0,000075

Combined Standard Uncertainty 0,218525

Expanded Uncertainty (k=2) 0,437  

99

RESULT AND DISCUSSIONSRESULT AND DISCUSSIONS

0 2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 09 . 9 0

9 . 9 5

1 0 . 0 0

1 0 . 0 5

1 0 . 1 0

1 0 . 1 5

1 0 . 2 0

Mea

sure

d A

ttenu

atio

n (d

B)

F r e q u e n c y ( G H z )

I F t e c h 1 0 V N A 1 0

1 9 . 7

1 9 . 8

1 9 . 9

2 0 . 0

2 0 . 1

2 0 . 2

2 0 . 3

I F t e c h 2 0 V N A 2 0

0 2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0

2 9 . 8

3 0 . 0

3 0 . 2

3 0 . 4

Mea

sure

d A

ttenu

atio

n (d

B)

F r e q u e n c y ( G H z )

I F t e c h 3 0 V N A 3 0

3 9 . 2

3 9 . 6

4 0 . 0

4 0 . 4

I F t e c h 4 0 V N A 4 0

Measured attenuation with associated uncertainties (a) 0-10 dB, 0–20 dB, (b) 0-30 dB, 0–40 dB

1010

RESULT AND DISCUSSIONSRESULT AND DISCUSSIONS

0 2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 04 9 . 2

4 9 . 6

5 0 . 0

5 0 . 4

5 0 . 8 I F t e c h 5 0 V N A 5 0

Mea

sure

d A

ttenu

atio

n (d

B)

F r e q u e n c y ( G H z )

5 9 . 2

5 9 . 6

6 0 . 0

6 0 . 4

6 0 . 8 I F t e c h 6 0 V N A 6 0

0 2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0

6 8 . 8

6 9 . 2

6 9 . 6

7 0 . 0

7 0 . 4

7 0 . 8

7 1 . 2

Mea

sure

d A

ttenu

atio

n (d

B)

F r e q u e n c y ( G H z )

I F t e c h 7 0 V N A 7 0

7 8 . 8

7 9 . 2

7 9 . 6

8 0 . 0

8 0 . 4

I F t e c h 8 0 V N A 8 0

Measured attenuation with associated uncertainties(a) 0-50 dB, 0 - 60 dB, (b) 0-70 dB, 0–80 dB

1111

CONCLUSIONSCONCLUSIONS 30 MHz piston

attenuator (NMI Australia)

± 0.001 dB/ 10 dB

30 MHzWBCO attenuator

(NPL, India)± [0.004+0.0001] dB

: measured attenuation value

RF attenuation measurement system using

IF substitution technique± 0.01 dB/ 10 dB

(0.1-60 dB, 30 MHz to 18 GHz)

RF step attenuator

RF attenuation measurement using Vector network analyzer

± 0.06/10 dB(0.1-80 dB, 50 MHz to 18 GHz)

Traceability of RF attenuation measurements

  VNA technique:

Measurements provide the fast, accurate and complete characterization of microwave components over broad frequency range.

Wide measurement range can be achieved by improving the linearity, directivity, tracking and effective test port match terms.

The expanded uncertainty in VNA technique is within 0,06 dB/10 dB for 80 dB in frequency range 50 MHz to18 GHz.

IF substitution technique:

The mixer non-linearity, RF leakage and noise are the major factors to be controlled in order to enhance the measurement dynamic range and better uncertainty.

The measurement process is time consuming with better uncertainty at spot frequency since measurements have taken at each frequency.

However the estimation of uncertainty is easy and measurement speed can be improved through the automation of the complete system

The expanded uncertainty in IF substitution technique is estimated within 0,03 dB/10 dB for 80 dB in the frequency range 50 MHz to 18 GHz.