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Measurements of Wireless Devices in Reverberation Chambers Measurements of Wireless Devices in Reverberation Chambers Kate A. Remley IEEE EMC Society Distinguished Lecturer Group Leader, NIST Metrology for Wireless Systems Publication of the United States government, not subject to copyright in the U.S. Institute of Electrical and Electronics Engineers (IEEE) Mission: Advance technological innovation and excellence for the benefit of humanity IEEE Geographical Operations center @ Technical Corporate office @ 17th floor, organizational Piscataway, New Jersey 3 Park Avenue in New York City units focus A dual complementary Region regional & 1-10 technical Societies structure Sections Chapters The Founding of IEEE 1884 1912 1963 AIEE and IRE merged to become AIEE IRE American Institute Institute of Radio the Institute of Electrical and of Electrical Engineers Engineers Electronics Engineers, or IEEE. Thomas Edison, Pioneers of wireless Alexander Graham Bell, technologies and other notables and electronics founded the founded the American Institute of Institute of Radio Electrical Engineers. Engineers. IEEE Today at a Glance Our Global Reach 421,000+ 39 160 Members Technical Societies Countries Member Senior Member IEEE Fellow Our Technical Breadth 1,600 3,900,000+ 170+ Annual Conferences Technical Documents Top-cited Periodicals IEEE EMC Society IEEE Electromagnetic Compatibility Society: the world's largest organization dedicated to the development and distribution of information, tools, and techniques for reducing electromagnetic interference. The society's field of interest: standards, measurement techniques and test procedures, instrumentation, equipment and systems characteristics, interference control techniques and components, education, computational analysis, and spectrum management, along with scientific, technical, industrial, professional and other activities that contribute to this field. Founded in 1957 Professional Group on Radio Frequency Interference (PGRFI) Institute of Radio Engineers (IRE) IEEE EMC Society Global Reach 60th anniversary ~4,000 160 (2017) Members Countries Member Senior Member IEEE Fellow Technical Breadth Flagship Annual Conference IEEE Trans. EMC IEEE International IEEE EMC Magazine EMC Standards EMC Symposium IEEE Trans SIPI NIST, Wireless, and 5G Communications Technology Laboratory (March 2014) Targeted research: test and measurement of new communication technologiesNIST Mission: To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, o Calibrations and traceability for wireless instrumentation and technology in ways that enhance economic security and o Refinement and validation of test protocols, models, and simulation tools improve our quality of life. o New test methods for spectrum sharing, 5G, and other national priorities mmWave mmWave Channel Transistors, Over-the-Air, Modulated Signals Measurement Amplifiers Antennas and and Modeling Massive MIMO Metrology8 for Wireless Systems Group . Test methods and uncertainties for modulated-signal measurements . Support for standards development . Standards and certification groups (CTIA, IEEE, ANSI, …) . Data for standards development (smart manufacturing initiative, NFPA, …) Research Services Publications Direct Committees Interaction OTA Test in reverberation chambers involves all except calibration services What is a Reverberation Chamber? . A shielded, highly reflective radiated-signal test chamber What you can do with one: . Create known fields (EMC/susceptibility) . Radiated emissions and power (CW and modulated-signal) . Antenna parameters (, efficiency, etc.) You can also do communication system tests . Receiver sensitivity . Throughput . EVM, BER, etc. DUT needs realistic channel 1 BER BER .01 CBW=32.8CBW=328 kHzkHz HighLow BERBER .01 0 45 90 135 180 225 270 315 360 ) Paddle angle (degrees) ) Paddle angle (degrees) m m NIST measurements of prototype 4G NISTMIMO measurements cellular telephone of wireless antennas router Fields in a Metal Box (Cavity)* . In a metal box, the fields have well defined modal distributions. Some locations have very high field values . Some locations have very low field values * With thanks to Chris Holloway Fields in a Metal Box with Large, Rotating Scatterer (Paddle) Frozen Food • The paddle changes internal field distributions (modes) where the high and low field values occur • Ideally, after one mode-stirring sequence, all locations in the chamber will have experienced nearly the same collection of field maxima and minima A “Statistical” Test Chamber . Quantities measured in the reverberation chamber are averaged over a mode-stirring sequence . Randomize fields with . Mode-stirring paddles . Changing physical position or moving walls . Using multiple antennas with various locations, polarizations, etc. Reverberation Chambers Come in All Shapes and Sizes Lowest frequency of operation, uncertainties determined by chamber size, wall loss NASA: Glenn Research Reverberation Chamber Center (Sandusky, OH) with Moving Walls Reverberation Chamber Characteristics Constructive and destructive interference for each -10 mode-stirring sample All Frequencies, one angle PCS Band, four angles -20 . Frequency domain (|S |2): 21 -30 (dB) Reflections create multipath 2 -40 |S21| -50 Reverberation Chamber -60 Measurement 1 1.5 2 antenna Frequency (GHz) Mode-stirring paddle Reference . Time domain (power antenna delay profile): Decay time Device Vector Network RF under RF Analyzer of reflections depends on abs test abs P1 P2 Platform chamber reflectivity Original Applications . Radiated immunity: . Antenna efficiency high field strength . Calibrate RF probes . components . RF/MW Spectrograph . large systems . absorption properties . Radiated emissions . Material heating . Shielding . Biological effects . cables . Conductivity and . connectors material properties . enclosures Wireless Applications . Multipath environments . Standardized over- . Rayleigh, Rician multipath the-air test methods channels: with/without . Radiated power of channel emulators mobile wireless devices . Time response: power . Receiver sensitivity delay profile, delay spread . Large-form-factor and . Biological effects of body-worn devices (with modulated-signal phantoms) exposure . Public-safety emergency equipment . Gain from multiple antenna systems . TX or RX diversity . MIMO Emulating Multipath Environments Office Corridor Oil Refinery Apartment Building Automobile Plants Subterranean Tunnels NIST channel measurements: Standards development for electronic safety equipment such as firefighter beacons Channel Measurements: Denver High Rise Receiving Transmitting antenna antenna tripods 16062 inches cm VNA Port 1 Port 4 Ground Plane Fiber Optic Fiber Optic Transmitter Receiver 200 m RF Optical RF Optical Optical Fiber Replicate Environment in Reverberation Chamber • Add RF absorbing material to “tune” the decay time of the chamber • Distributed multipath (reflections) matched by chamber’s decay profile Time response of channel replicated in chamber 0 1 absorber: rms=187 ns -5 -10 3 absorber: rms=106 ns -15 -20 7 absorber: rms=66 ns -25 ile (dB) ile f -30 -35 -40 -45 Power Delay Pro -50 -55 Reverberation chamber with -60 Large office biulding -65 absorbing material rms=59 ns -70 0 50 100 150 200 250 300 350 400 450 500 time (ns) Emulating Other Reflective Environments . Oil Refinery Emulating Other Reflective Environments . Automobile Factories 0 -5 -10 -15 -20 o delay-spread=207ns * mean-delay=252.4ns o delay-spread=123ns * mean-delay=130.3ns -25 o delay-spread= 69ns * mean-delay=71.8ns o delay-spread=195ns * mean-delay=147.0ns -30 o delay-spread=199ns * mean-delay=161.6ns o delay-spread=261ns * mean-delay=275.3ns Power Delay Profile (dB) Profile Delay Power -35 1 absorber 3 absorbers -40 7 absorbers Jefferson North Plant, 10m -45 Jeffersonassembly North Plant, plant 50m Jefferson North Plant, 100m -50 0 100 200 300 400 500 600 700 800 900 time (ns) 0 o delay-spread=277ns * mean-delay=290.5ns 1 absorber o delay-spread=122ns * mean-delay=130.1ns 3 absorbers o delay-spread= 67ns * mean-delay=71.2ns o delay-spread=168ns * mean-delay=137.8ns 7 absorbers -5 o delay-spread=175ns * mean-delay=142.7ns flint metal, drg-drg, 10m o delay-spread=128ns * mean-delay=105.8ns flint stampingmetal, drg-drg, 50m o delay-spread=173ns * mean-delay=176.1ns flint metal, drg-drg, 80m flint metal,plant drg-drg, 110Bm -10 -15 Power Delay Profile (dB) Profile Delay Power -20 -25 -30 0 200 400 600 800 1000 1200 1400 1600 1800 2000 time (ns) Urban Canyon Multipath Effects -90 TX1 to RX5 -110 -100 rms = 115 ns Noise Threshold = -116 dB -110 -120 -120 -130 -130 -140 PDP (dB) PDP -140 PDP PDP (dB) -150 -150 TX1 to RX9 -160 -160 rms = 39 ns Noise Threshold = -116 dB R -170 -170 9 0 200 400 600 800 1000 1200 0 500 1000 Delay (ns) Delay (ns) R10 Line of Sight Non Line of Sight R (LOS) (NLOS) 5 T R T1 1212 •Measurements made in T3 Denver urban canyon 2009 T2 •Channel characterization: LOS and NLOS Replicating Clustered Multipath in 1 fitted simulated data Reverberation Chamber 0.9 measured Data Denver 0.8 0.7 Shortest path 0.6 0.5 PDP TX 0.4 0.3 0.2 0.1 0 0 100 200 300 400 500 600 700 800 900 1000 RX Delay [ns] • Blue: Mean of 27 NLOS Clusters of measurements exponentially • Red: RC + channel distributed signals emulator received off of • Dashed: Exponential model buildings “Channel Models” used for standardized over-the-air (OTA) tests . Outdoor-to-indoor channel model for 700 MHz . 8 environments, hundreds of measurements . Included in proposed 3GPP reverberation- chamber-based test methods
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