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Electro-Optic Sensors for RF Electric Fields: a Diagnostic Tool for Microwave
Circuits and Antennas
If any of the enclosed materials are to be cited in other publications, the users are responsible for referencing the authors of this tutorial as the source of such material.
Reproductions of any of the enclosed materials, either partial or whole, and including the extraction of individual graphs or figures, is not allowed without permission from the copyright holder and appropriate citation of the source.
Specific copyright information is included on each slide as appropriate.
Electro-Optic Sensors for RF Electric Fields: a Diagnostic Tool for Microwave
Circuits and Antennas
John F. Whitaker, Kyoung Yang*, Ron Reano, and Linda P.B. Katehi#
Center For Ultrafast Optical Science & Radiation LaboratoryDept. of Electrical Engineering & Computer ScienceUniversity of Michigan, Ann Arbor
* Currently at EMAG Technologies, Inc.# Currently at Purdue University
Outline
• Motivation & Background
• Fundamental Concepts of Electro-Optic Probing
• System Configuration & Attributes
• Diagnostic Measurement Examples
• Thermal & Magnetic-Field Imaging
Motivation• Near-field measurements – radiating structures
– High spatial resolution at h << λ– Observation of nonradiating waves– Near-to-far-field transformation
• Near-field measurements – guided-wave structures– Internal-node characterization
• Near-field diagnostics - fault isolation – Detect malfunctioning components– Determine relative phase of sources
• Design/performance verification• Model Validation
Electro-Optic Sampling Probe Embodimentsinput beamoutput beam
optical fiber
integrated type
fiber-based EO probingexternal (free-space)EO probing
substrate probing
1st Generation 2nd Generation 3rd Generation
Additional field-mapping concept & applications references:
• U. Colorado – Boulder• U. Duisberg
• U. Maryland• Brunel Univ.• U. Tokyo
• U. Aachen• NTT (x2)• NPL
"This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder."
Principle – Electro-optic Effect
•RF electric-field measurements based on electro-optic (Pockels) effect.
•External polarizers are cross-polarized.
•Change in polarization state due to electric field induced linear birefringence.
"(c) 2002 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
Electro-Optic Equivalent-Time Sampling for High-Bandwidth Measurements
microwave signal f m
Principle:Harmonic Mixing
f = f - n fm rep.IF
timereplocal oscillator (laser pulse train) f
f Iintermediate frequency Ftime
time
Fiber-Based EO Field-Mapping System
Lock-inAmplifier
opticalisolator
mirror
polarization dependantbeam splitter
fiber coupler
fiber polarizationcontroller (λ/2,λ/4)
computer-controlledtranslation stage
10 M
Hz
com
mon
refe
renc
e
single-modeoptical fiber
GRIN Lens
GaAs Tip
λ/2 wave plate
input (detection) beam
reflected (signal) beam
photo diode
RF-Synthesizer
Ti:Sapphire Laser
RF-Synthesizer
"(c) 2001 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
Polarization Control in an Electro-Optic Probing System IN2 IN4IN1 IN3
optical isolatorλ/2 WP BS
photo diode
OUT1
OUT3
H
V90o
67.5o
0o 0o
0o
(45+δ)o
λ/2 loop λ/4 loop
(22.5+δ)o
o22.5
IN7(22.5+θ)o
(22.5+θ+δ)o
(45+δ)o
90o
OUT4
IN5
fiber couplerOUT2
OUT5
IN6
GaAs tip
single-mode optical fiber GRIN Lens
"This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder."
1-D Electro-Optic Field MappingCoplanar Waveguide Transmission Line cross Section
zcrosssection
x
-200 -100 0 100 2000.0
0.2
0.4
0.6
0.8
1.0
position (µm)
norm
. am
plitu
de
-100
-50
0
50
100
Normal field component
-200 -100 0 100 200
0.0
0.2
0.4
0.6
0.8
1.0
-200
-100
0
100
norm
. am
plitu
de
position (µm)
Tangential field component
rel.
phas
e (d
eg.)
rel.
phas
e (d
eg.)
"(c) 1998 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
Electro-Optic Electric-Field-Sensing Capabilities
• Extract both amplitude and phase of electric fields• Isolate X, Y, and Z vectorial components
– (110) GaAs probe tip for tangential fields– (100) GaAs probe tip for normal field
• Near-field measurement (range < 100 µm)• Low invasiveness
– probe much smaller than wavelength– no metal near field to be measured– finite difference simulations indicate small changes
in Zc for typical probe heights• High positioning flexibility with fiber coupling
Electro-Optic Electric-Field Sensing: System Performance
• Bandwidth: >100 GHz
• Spatial Resolution: < 8 µm• Phase stability: +/- 3°/hour
• Cross Polarization Suppression: > 30 dB
• Time for Measurement: 15-60 min.
• Area of measurement: micrometers to meters• Sensitivity: < 1 V/m/(Hz)1/2
Electro-Optic Field Mapping of a Microstrip Patch- Measurement vs. FEM Simulation
amplitude (height :0 mm)
x component
y component
z component
simulationmeasurement measurement simulation
phase (height :0 mm)
180
100
0
-100
-180
1.00
0.80
0.60
0.40
0.20
0.00
x component
y component
z component
xy
"(c) 2000 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
Electro-Optic Electric-Field Sensing:S11 Measurement on Microstrip Patch Antenna
0 10 20 30 40-250
-200
-150
-100
-50
0
50
100
150
200
feeding line antenna
3.523 GHz 4.011 GHz 4.563 GHz
E.O
. sig
nal p
hase
[deg
.]
distance [mm]
0 10 20 30 40-1
0
1
2
3
4
5
6
feeding line antenna
3.523 GHz 4.011 GHz 4.563 GHz
E.O
. sig
nal a
mpl
itude
[ a.
u. ]
distance [mm]
3.0 3.5 4.0 4.5 5.0-40
-30
-20
-10
0
E.O. measurement HP 8510 measurement
l S11
l [d
B]
frequency [GHz]
"(c) 2000 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
Field-Sensing-Probe Invasiveness• Return loss from CPW measured and calculated with and without
EO probe in position.
• Frequency domain measurements (2 - 40 GHz): |S11| < -30 dB with and without probe
"(c) 2001 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
Electric Field Sensing in a 1 X 4 Power Distribution Network: Operation and Fault Isolation
IN
OUT OUT OUT OUT
short point3.7
mm
Wilkinsonpower divider
y
z-component, frequency: 15 GHz
xz8.3 mm
-0
--25
--50matched circuit, amplitude (dB)
-0
--30
--60partially shorted circuit, amplitude (dB)
shorted air-bridge fault
"(c) 1998 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
Field Sensing in an Antenna ArrayDiagnosis of Malfunction in a Ka-Band Quasi-Optical Amplifier Patch Array
patch antenna
input horn
output horn
input polarizeroutput polarizer
QO array
Ampl
itude
(nor
m.)
coup
ler
MM
IC a
mpl
ifierBasic operating principle
Array provided by Lockheed-Martin
"(c) 2001 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
Field Sensing in an Antenna ArrayKa-Band Quasi-Optical Amplifier Slot Array:Observation of parasitic coupling
ampl
itude
(nor
m.)
DC bias point
0.00
0.20
0.40
0.60
0.80
1.00
-180 100 0 180100phase (degree)
0.00 0.20 0.40 0.60 0.80 1.00amplitude (norm.)
Array provided by Zoya PopovicUniv. of Colorado - Boulder
"(c) 2001 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
Field Sensing Inside Microwave PackagesShielded Microstrip at f = 8 GHz
sliding top metal plate
short termination
glass tube (supporter)
GRIN lensGaAs EO tip
input port
optical fiber
side metal wall
microstrip substrate
Shielded Microstrip (open side view)
"(c) 2001 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
Field Sensing Inside Microwave Packages: Shielded Microstrip Measurements
E h = 1 mm
shielded microstripexposed microstrip
amplitude [norm.] phase [degree] amplitude [norm.] phase [degree]
"This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder."
Thermal Calibration, Sensing, and Imaging• Temperature measurements based on optical absorption due to the
temperature dependence of the band-edge in GaAs.
"(c) 2001 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
•Relationship between optical power (P) and temperature (T)
System Implementation for Simultaneous Electric Field and Temperature Sensing
*Absorption Temperature &E-field
*Polarization-state E-Field
• E-fields and thermal distributions can be measured at the same time with a single probe.
"(c) 2001 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
Electro/Thermal Measurements on a Quasi-Optical Amplifier via Optical Sensor
• Corrupted electric-field data corrected via:
Temperature Corrected Data
Cor
r. E-
Fiel
d D
ata
[µV]
Cor
r. E-
Fiel
d D
ata
[µV]
Power M
eter Data [V]
Measured Tem
p [ oC]
Simultaneous Measurements
Time [min] Time [min]• Simultaneous measurements show an increase of 7oC in 11
min during which the output E-field is essentially constant."(c) 2001 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
Magnetic-Field Mapping via Magneto-Optic Sampling• RF magnetic-field measurements based on Faraday effect
• External polarizers are oriented at 45 degrees.
T = −12
12
2sin( )αo H V Lα µ=α = µοHVL
•Rotation of optical linear polarization due to magnetic field induced circular birefringence.
"This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder."
Magneto-Optic Magnetic-Field-Sensing System Schematic and Probe
Terbium Gallium Garnet (TGG) magneto-optic material
"This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder."
Magnetic-Field Sensing• Magnetic-field phasor vs. position of horn antenna aperture
obtained at 60 GHz
- Probe length tuned to device frequency to create resonant cavityand provide 10-dB sensitivity enhancement.
- B-field can be combined with E-field to determine impedance at internal measurement locations
"This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder."
Combined Electric/Magnetic-Field Sensor• Utilizing a Hybrid Electro-Optic Magneto-Optic Probe
TGG (εr=12.4)Diameter: 2 mmLength: 2.3 mm
V = 61 rad T-1 m-1
GaAs (εr=13.2)Edge: 2 mm
Length: 0.1 mmr41 = 1.1 pm V-1
"(c) 2002 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
Hybrid EO/MO Sensor Measurements•Device-under-test: Shorted microstrip transmission line
•RF: 4.003 GHz @ 17.7 dBm
• Demonstrated 22 dB of isolation• Isolation between electric and magnetic field sensitivity:
- limited by degree to which electrooptic effect can be minimized- minimization driven by optical linear polarization purity
"(c) 2002 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
Electric-Field, Magnetic-Field, and ThermalSensing in a High-Power Microstrip Patch
x
x
x|Hx| |Hx|
"(c) 2002 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE."
ConclusionA fiber-optic-based field-sensing system offers:
• high spatial-resolution, broad-bandwidth, and low invasiveness
• detailed performance verification and diagnosis in the near-field region
• high measurement flexibility• detection of electric field distributions inside
of microwave enclosures and packages• expanded capability with thermal and
magnetic-field sensing