Electro-Optic Sensors for RF Electric Fields: a Diagnostic Tool for Microwave Circuits and Antennas

Transcription

1 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.

2 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 Laboratory Dept. of Electrical Engineering & Computer Science University of Michigan, Ann Arbor * Currently at EMAG Technologies, Inc. # Currently at Purdue University

3 Outline Motivation & Background Fundamental Concepts of Electro-Optic Probing System Configuration & Attributes Diagnostic Measurement Examples Thermal & Magnetic-Field Imaging

4 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

5 Electro-Optic Sampling Probe Embodiments output beam input beam optical fiber integrated type external (free-space) EO probing fiber-based EO probing substrate probing 1st Generation 2nd Generation 3rd Generation Additional field-mapping concept & applications references: U. Colorado Boulder U. Duisberg U. Aachen NTT (x2) NPL U. Maryland Brunel Univ. U. Tokyo "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."

6 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

7 Electro-Optic Equivalent-Time Sampling for High-Bandwidth Measurements microwave signal f m Principle: Harmonic Mixing local oscillator (laser pulse train) f rep time f = f - n. f IF m rep intermediate frequency f I F time time

8 Fiber-Based EO Field-Mapping System 10 MHz common reference Ti:Sapphire Laser RF- Synthesizer Lock-in Amplifier optical isolator photo diode input (detection) beam λ/2 wave plate reflected (signal) beam mirror polarization dependant beam splitter RF- Synthesizer fiber coupler fiber polarization controller (λ/2,λ/4) single-mode optical fiber GRIN Lens GaAs Tip computer-controlled translation stage "(c) 2001 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional

9 Polarization Control in an Electro-Optic Probing System IN1 V 90 o H IN2 IN3 IN4 0 o 0 o OUT4 (45+δ) o IN5 optical isolator λ/2 WP 67.5 o BS 0 o OUT5 90 o photo diode OUT2 fiber coupler (22.5+δ) o (45+δ) o OUT3 OUT1 (22.5+θ+δ) o (22.5+θ) o IN7 λ/2 loop λ/4 loop o 22.5 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."

10 1-D Electro-Optic Field Mapping Coplanar Waveguide Transmission Line cross Section cross section z x norm. amplitude position (µm) rel. phase (deg.) norm. amplitude position (µm) rel. phase (deg.) Normal field component Tangential field component "(c) 1998 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional

11 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 Z c for typical probe heights High positioning flexibility with fiber coupling

12 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: min. Area of measurement: micrometers to meters Sensitivity: < 1 V/m/(Hz) 1/2

13 Electro-Optic Field Mapping of a Microstrip Patch - Measurement vs. FEM Simulation amplitude (height :0 mm) phase (height :0 mm) measurement simulation measurement simulation 1.00 x y x component x component y component y component z component 0.00 z component -180 "(c) 2000 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional

14 Electro-Optic Electric-Field Sensing: S 11 Measurement on Microstrip Patch Antenna 6 E.O. signal amplitude [ a.u. ] GHz GHz GHz feeding line antenna distance [mm] E.O. signal phase [deg.] GHz GHz GHz feeding line antenna distance [mm] l S11 l [db] E.O. measurement HP 8510 measurement 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

15 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

16 Electric Field Sensing in a 1 X 4 Power Distribution Network: Operation and Fault Isolation IN 3.7 mm OUT OUT OUT OUT Wilkinson power divider 8.3 mm short point z y x z-component, frequency: 15 GHz -0 matched circuit, amplitude (db) partially 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

17 Field Sensing in an Antenna Array Diagnosis of Malfunction in a Ka-Band Quasi- Optical Amplifier Patch Array Basic operating principle output horn QO array input horn output polarizer input polarizer coupler MMIC amplifier patch antenna Array provided by Lockheed-Martin Amplitude (norm.) "(c) 2001 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional

18 Field Sensing in an Antenna Array Ka-Band Quasi-Optical Amplifier Slot Array: Observation of parasitic coupling DC bias point amplitude (norm.) Array provided by Zoya Popovic Univ. of Colorado - Boulder amplitude (norm.) phase (degree) "(c) 2001 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional

19 Field Sensing Inside Microwave Packages Shielded Microstrip at f = 8 GHz optical fiber sliding top metal plate glass tube (supporter) GaAs EO tip GRIN lens side metal wall short termination microstrip substrate input port 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

20 Field Sensing Inside Microwave Packages: Shielded Microstrip Measurements E h = 1 mm exposed microstrip shielded 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."

21 Thermal Calibration, Sensing, and Imaging Temperature measurements based on optical absorption due to the temperature dependence of the band-edge in GaAs. Relationship between optical power (P) and temperature (T) "(c) 2001 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional

22 System Implementation for Simultaneous Electric Field and Temperature Sensing E-fields and thermal distributions can be measured at the same time with a single probe. *Absorption Temperature & E-field *Polarization-state E-Field "(c) 2001 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional

23 Electro/Thermal Measurements on a Quasi-Optical Amplifier via Optical Sensor Corrupted electric-field data corrected via: Temperature Corrected Data Simultaneous Measurements Corr. E-Field Data [µv] Power Meter Data [V] Corr. E-Field Data [µv] Measured Temp [ o C] Time [min] Time [min] Simultaneous measurements show an increase of 7 o C 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

24 Magnetic-Field Mapping via Magneto-Optic Sampling RF magnetic-field measurements based on Faraday effect T = sin( 2α ) External polarizers are oriented at 45 degrees. α = µ o ο HVL 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."

25 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."

26 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 cavity and 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."

27 Combined Electric/Magnetic-Field Sensor Utilizing a Hybrid Electro-Optic Magneto-Optic Probe TGG (ε r =12.4) Diameter: 2 mm Length: 2.3 mm V = 61 rad T -1 m -1 GaAs (ε r =13.2) Edge: 2 mm Length: 0.1 mm r 41 = 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

28 Hybrid EO/MO Sensor Measurements Device-under-test: Shorted microstrip transmission line RF: 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

29 Electric-Field, Magnetic-Field, and Thermal Sensing in a High-Power Microstrip Patch H x x H x x x "(c) 2002 IEEE. Personal and classroom use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional

30 Conclusion A 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