Transcript
Transmission Line Theory and Advanced Measurements in the Field
Co-sponsored by
Tom Hoppin Application Specialist On Contract to Component Test Division Keysight Technologies
© Keysight Technologies 2015
Keysight FieldFox Education Webcast Series
Agenda – Transmission Line Basics – Frequency and Time Measurements
– Frequency Limitations of Connectors and Cables – Measuring Insertion Loss • One-Port Techniques • Very Long Cables – Troubleshooting Line Faults • TDR and Impulse Modes
• Examples of Cable and Waveguide Damage • Velocity Factor of Coax and Waveguide – Conclusions Keysight FieldFox Education Webcast Series
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Types of Common Transmission Lines Cross Section Metal
Microstrip (PCB) Dielectric Coaxial
Twin-lead
Twisted Pair (unshielded)
Twinaxial (shielded)
Stripline (PCB)
Waveguide Keysight FieldFox Education Webcast Series
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Physical Length of a Transmission Line When is a cable considered a “transmission line”?
Length
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Physical Length of a Transmission Line When is a cable considered a “transmission line”?
Length
Length
~ >
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Physical Length of a Transmission Line When is a cable considered a “transmission line”?
1.2 meter (4 ft.) Example 1: Frequency (f) = 1 kHz
Example 2: Frequency (f) = 1 GHz
vcoax 3x10 8 m/sec (VF) 198km f 1kHz
vcoax 3x10 8 m/sec (VF) 0.198m f 1GHz
1.2 meter cable is 0.000006
(=0.0020)
Not considered a transmission line
1.2 meter cable is 6.06
(=2.2k0)
Yes, this is a transmission line
VF = 0.66 (cable datasheet) Keysight FieldFox Education Webcast Series
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Measured S21 (Phase) vs. Frequency 1.2 meter
@1GHz: 6 = 2.2k0 (1 = 3600) S21( unwrapped phase)
• Negative phase implies delay or lag • Linear phase response = Non-dispersive medium
Linear slope
• Phase displayed in “wrapped” or “unwrapped” format.
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Measured S11 (dB) as a function of Frequency 50 W
1 S11 2
2 1
n (1800)
n (3600)
Frequency Keysight FieldFox Education Webcast Series
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Measured S11 (Z) as a function of Time Step
SHORT t=0
time
TDR (Lowpass Step)
Convert time to distance 50 W
time distance vcoax 2
12nsec (1.2m)
0W
vcoax VF c Time
RG-214 Cable Length = 1.2 meter, Impedance = 50 ohms, Velocity Factor (VF) = 66% Keysight FieldFox Education Webcast Series
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Frequency Range Specifications CAT-3 CAT-5e CAT-6a
DXN-2600 7/16 Connector
Type-N SMA LMR-1700
Cable
RG-214 TTL26 WR-187 WR-137 WR-90 WR-62 WR-42 0.001
DXN2600 is a product of W.L. Gore & Associates LMR® is a trademark of Times Microwave Systems TT26 is an Accuphase ® cable from Carlisle Group
0.01
0.1
1
10
26.5
Frequency (GHz) Keysight FieldFox Education Webcast Series
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Frequency Limitations – Coaxial Cable • RG-214 specified from DC to 11 GHz • fc, TE11 = 13.1GHz (RG-214) D
d
S21 for RG-214 TEM
TE11
(desired)
Specified Range DC (30kHz)
11 GHz
TE11 Mode
Coax TE11 Mode:
f C , TE11
7.514 D d r
f in GHz, D & d in inches Keysight FieldFox Education Webcast Series
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Frequency Limitations - Waveguide • Operates above fc, TE10 and below fc, TE20
b
• WR-90: fc, TE10 = 6.56GHz, fc, TE20 = 13.1GHz a S21 for WR-90
TE10 Cutoff
Specified Range 8.2GHz
TE10 (desired)
12.4GHz TE20 Cutoff
TE20 Waveguide TEm0 Modes:
f C , m0 WR-90: a=0.9”, b=0.4”
m( c ) 2a r
f in GHz, D &d in inches
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Measurement Types • FieldFox measures s-parameters: S11, S21, S12, S22 • Calculate delay • Calculate time domain response (step and impulse)
Slope
Log Mag
Delay
Delay (secs.) -
1 3600 f
Frequency
Non-dispersive = “flat” response
Time Domain (Impulse)
Phase
IFFT
Time
VF required for distance calculations
VF
1
r
constant for coax
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Insertion Loss Measurement Techniques Traditional • Both ends available • Mechanical and ECal • CalReady and QuickCal
1-Port Loss • Only one end available • Low Loss (<30dB)
Open or Short
Extended Range (ERTA) • High Dynamic Range • No calibration or warm-up time • Frequency Offset Capable
11667B
Trig/ Data
#1:Source
#2: Receiver Keysight FieldFox Education Webcast Series
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Low-Loss Cable Measurement 2-Port VNA
Open or Short
1-Port CAT
CableLoss (S21)
Cable Loss
10-foot Coaxial Cable, SMA
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Long Cable Measurement
2-Port VNA
ERTA
Cable Loss (S21)
Cable Loss
100-foot Coaxial Cable, Type-N Keysight FieldFox Education Webcast Series
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Other Transmission Line Configurations 50W Cable
75W Cable
Waveguide
Twisted Pair
Direct Connection
N9910X-846 50-75W adapter
Coax-to-WG Adapter
RJ45-to-SMA Adapter or Balun
50 W coax
Waveguide
50 W coax
100W balanced
75W coax
Type N or 3.5mm
Z0=75 W (Smith Chart)
Medium = Waveguide
Mixed Mode Keysight FieldFox Education Webcast Series
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Troubleshooting Transmission Lines CAT and VNA Modes • Verify transmission line performance (line sweeping) • Determine the location of damage (DTF) • Determine the type of failure Types of Faults • Loose connector, flange screws
• Failed seal at a cable splice or flange (water ingress) • Failed solder joint at connector interface • Cut, crushed and/or weather-induced cracks • Minimum bend radius exceeded
• Breakdown, and arcing effects DTF = Distance to Fault Images courtesy of John Arthur, Wireless EDGE
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Distance to Fault (DTF) Measurements Technique to determine the location of problems along a transmission line Damaged Cable
Input Pulse or Step Measuring reflected pulse:
Transmitted Pulse or Step Reflected Pulse or Step
timeround trip vcable DTF(meters) 2 timeround trip (VF)( c) 2 Keysight FieldFox Education Webcast Series
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DTF For Coax
(M2) (M3) End of Cable
“Velocity Factor” (VF)
FieldFox
Cable
4m
Adapter
Cable
50-ohm Load
9.8m
(M2)
(M3) Keysight FieldFox Education Webcast Series
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TDR and Impulse Response A
Bend Radius Exceeded
B
Outer Conductor Cut
B
B
TDR (Step) A
Impulse (Low-Pass)
A
Input connector
50-ohm
Termination Inductive Keysight FieldFox Education Webcast Series
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Types of Discontinuities TDR (Step)
Impulse (Low-Pass)
R > Z0 R < Z0 Inductor Capacitor Step and Low-pass mode requires transmission line operation to DC • Cable and Antenna Test Option includes TDR (Step) • VNA option includes Step, Low-Pass Impulse, Band-Pass Impulse Keysight FieldFox Education Webcast Series
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DTF For Waveguide Coax-WG
Straight WR-90
Flex WR-90
Water Terminated Or Open
To FieldFox
Bandpass Mode Required
Open-ended Waveguide
Coaxial Adapter
Water in Flexguide Open
Termination What about the VF for Waveguide? Keysight FieldFox Education Webcast Series
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Velocity Factor For Waveguide
Cross section of Waveguide 12 GHz
Velocity Factor is a function of frequency
VF_1 = 0.649
a
2.5 ft. length of X-Band waveguide
VF_2 = 0.771
8 GHz
VF_3 = 0.836
Delay is non-linear = “Dispersive” 6.5 GHz
No Propagation
Time Domain Corrected for Non-linear VF f VF ( f ) 1 cutoff f
2
Select “Waveguide” media on FieldFox Keysight FieldFox Education Webcast Series
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FieldFox Rugged to MIL-PRF-2880F Class 2 MIL-Spec durability Meets MIL-PRF-28800F Class 2 requirements Type tested and meets MIL-STD-810G, Method 511.5 Procedure 1 requirements for operation in explosive environments
Field-proof Type tested to IP53: completely sealed instrument enclosure provides measurement stability in dusty and wet environments
3-year warranty ensures field confidence (standard on all FieldFox analyzers) Low emissions, meets CISPR Pub 11, class B Water-resistant chassis, keypad, and case withstand wide temperature ranges, and salty, humid environments • Case withstands shock and vibrations • Wide operating temperature -10 to +55 °C (+14 to +131 °F) • Wide storage temperature -51 to +71 °C (-60 to +160 °F) Keysight FieldFox Education Webcast Series
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Keysight FieldFox Combination Analyzers Combination Analyzers can be configured with the following capabilities • Vector Network Analyzer (VNA) • Cable and Antenna Test (CAT) • Spectrum Analyzer • Vector Voltmeter (VVM)
• Power Meter • Independent Source Models include frequencies up to 26.5 GHz
• 6.6 pounds (3 kg) • Built-in GPS • 3.5 hour battery life Carry precision with you - Keysight-quality measurements Keysight FieldFox Education Webcast Series
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Conclusions – Transmission lines have lengths on the order of a wavelength – Phase affects the magnitude response – Operating frequency is limited by geometry • Two-conductor lines operate down to DC • Waveguide is narrowband – Insertion loss can be measured several ways
– Troubleshooting faults requires a time domain response – Non-dispersive lines have a linear phase slope • Coaxial lines are non-dispersive • Waveguide is dispersive – With industry's best transmission line measurement capability, FieldFox is the ideal tool for testing in the field Keysight FieldFox Education Webcast Series
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For More Information Web: www.keysight.com/find/FieldFox Literature: •
Techniques for Precise Interference Measurements in the Field, Application Note, Literature Number 5991-0418EN
•
Techniques for Precise Cable and Antenna Measurements in the Field, Application Note, Literature Number 5991-0419EN
•
Correlating Microwave Measurements between Handheld and Benchtop Analyzers, Application Note, Literature Number 5991-0422EN
•
Techniques for Precise Measurement Calibrations in the Field, Application Note, Literature Number 5991-0421EN
•
Techniques for Precision Validation of Radar System Performance in the Field, Application Note, Literature Number 5991-4107EN
FieldFox handheld education application webcast series Registration: www.keysight.com/find/FieldFoxWebcasts Co-sponsored by
Thank you for your time. Questions? Keysight FieldFox Education Webcast Series
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