This document summarizes work calibrating and characterizing the electromagnetic reverberation chamber at NASA's Johnson Space Center. It describes the chamber dimensions and components, calibration procedures according to standards like DO-160F, and issues encountered like antenna fixture problems or field monitor failures. Solutions for improving chamber operation and future work are discussed, such as developing rigorous test procedures, integrating an improved motor controller, and replacing aging equipment. The intern's work calibrating the chamber and addressing technical challenges is acknowledged.

1. THE ELECTROMAGNETIC
REVERBERATION
CHAMBER AT NASA JSC
Field Uniformity Testing and Calibration

2. ABOUT THE INTERN
• Oregon State University: B.S., Philosophy
• San Francisco State University: M.S., Physics
• University of Connecticut: Ph.D., Physics
(in progress)
• EMI Intern by trade
• Hobbies include
• Travel
• Photography
• Quantum Field Theory

3. EV5: ELECTROMAGNETIC
INTERFERENCE AND COMPATIBILITY
• EMI/EMC test facilities at JSC provide evaluation and certification testing of
crew, flight, and ground support equipment including: Communication,
Instrumentation, Biomedical, Guidance and Navigation, Computation, and
Robotics.
• Electrical and electronic equipment aboard a spacecraft can malfunction
or become totally inoperable if not designed to properly minimize the effects
of interference from the internal and external electromagnetic environments.
Proper equipment and system designs are also necessary for minimizing
potential electromagnetic emissions into the operating environment.

4. THE REVERB CHAMBER
Physical Characterization and Relevant Parameters

5. THE REVERB CHAMBER
Dimensions: 3.07 x 3.07 x 2.46 meters
Lowest Usable Frequency: ~240 MHz (100 modes)
Installed
Equipment: Tuner
Step Motor
Transmit Antenna
Calibration
Equipment: Field Probe
Receive Antenna
RF Absorbers (loaded chamber)
Closed Cell Styrofoam Test Bench
(loaded chamber)

6. THE REVERB CHAMBER
A BIG “MICROWAVE OVEN”
• Transmit antenna sets up EM fields in
chamber
• Tuner position determines EM
boundary conditions
• Averaging measurements over tuner
rotation washes out “hot” and “cold”
spots
• Rigid coordinate system
• Field Probe and Rx antenna positions
• 9 positions (8 for loaded chamber)
• Probe axis orientation vs chamber
coordinate axes

7. REVERBERATION CHAMBER TESTING:
BENEFITS
• Allows equipment under susceptibility
test to be exposed to RF radiation
isotropically (from all directions)
• Radiated emissions will be picked up
regardless of any directional bias in
emissions
• Allows for automated testing without
switching out antennas/varying
polarizations
• Depending on the application, test
frequency step granularity may be
coarser than (semi-)anechoic
alternative offering faster test times
• Susceptibility testing emulates realistic
aircraft operating environment more
faithfully than (semi-)anechoic
methods

8. INSTRUMENTATION
• Signal Generator
• Amplifier
• Directional Coupler
• Power Sensors/Meter
• Spectrum Analyzer
• Field Monitor
• Control PC
• Motor Controller

9. INSTRUMENTATION
• Signal Generator
• Amplifier
• Directional Coupler
• Power Sensors/Meter
• Spectrum Analyzer
• Field Monitor
• Control PC
• Motor Controller

10. RC CALIBRATION AND
TESTING STANDARDS
IEC 61000-4-21
• terminology, descriptions
of electromagnetic
phenomena and the EM
environment,
measurement and
testing techniques, and
guidelines on installation
and mitigation
MIL-STD-461
• establishes interface and
associated verification
requirements for the control of
the electromagnetic
interference (emission and
susceptibility) characteristics of
electronic, electrical, and
electromechanical equipment
and subsystems designed or
procured for use by activities
and agencies of the
Department of Defense
RTCA DO-160F/G
• establishes interface and
associated verification
requirements for the control of
the electromagnetic
interference (emission and
susceptibility) characteristics of
electronic, electrical, and
electromechanical equipment
and subsystems designed or
procured for use by activities
and agencies of the
Department of Defense

11. DO-160F
REQUIREMENTS
• Field Uniformity Requirements
• Test Frequency Spectrum Resolution (50
freq. per decade)
• Receive power and field strength
measurement regimen
• Field strength data verifies field
uniformity
• Received power measurements
provide baseline Antenna Calibration
Factor used in determining necessary
injected power for equipment test
• Suggested maximum loading (16 dB)
• # of tuner steps (frequency dependent)

12. CALIBRATION AND TESTING
Empty Chamber
• Field Uniformity Verification
• Antenna Calibration Factor
Loaded Chamber
• Field Uniformity Verification
• Antenna Calibration Factor
Equipment Test
• Pretest Chamber Calibration Factor
(injected power determination)
• Emissions and Susceptibility Test

13. TILE RC
CALIBRATION
PROFILE
1. Initialize Instrumentation
2. Sweep test frequency range
3. Export data (power/field strength
measurements) to .csv
4. Increment Tuner
5. Repeat 1-4 50 times for 1 revolution
6. Move probe/Rx antenna
7. Repeat 1-5
Note: TILE! v.6 has no versatile loop
capability

14. MOTOR CONTROLLER
COMMAND SEQUENCE
• Anaheim Automation Motor Controller
“Direct Talk” Mode
• VISA interface
• Acceleration/Base speed important
• Line break syntax

15. TILE! REVERBERATION CHAMBER CALIBRATION DIALOGUE

16. TILE! TABLE: OUTPUT TO .CSV FILE
• Test Frequency
• Electric field strength: components and
RMS (Watts/m)
• Forward/Reverse/Net Injected Power
• Received Power
• Signal Generator Amplitude

17. DATA PROCESSING TEMPLATES

18. 0
0.5
1
1.5
2
2.5
3
3.5
4
0 500 1000 1500
E-fieldStandardDeviation
(dBm)
Frequency (MHz)
Empty Chamber Field Uniformity
SD Ex
SD Ey
SD Ez
SD x-y-z
EMPTY CHAMBER DATA

19. EMPTY CHAMBER DATA
-25
-20
-15
-10
-5
0
0 200 400 600 800 1000 1200
ACF(dB)
Frequency (MHz)
Empty Chamber ACF
ACF =
Average power
received divided by
average power
transmitted
(averaging
performed over
tuner positions)

20. EMPTY CHAMBER DATA
Rayleigh curve gives
probability distribution for
field strength of statistically
independent rectangular
components of multiply
scattered EM waves

21. THE LOADED CHAMBER
• DO-160F suggests loading the
chamber to obtain a factor of
12 (16 dB) degradation in ACF
• Obtained an average of 7 dB
decrease with significant
loading

22. 0
0.5
1
1.5
2
2.5
3
3.5
4
0 500 1000 1500
E-fieldStandardDeviation
(dBm)
Frequency (MHz)
Loaded Chamber Field Uniformity
SD Ex
SD Ey
SD Ez
SD x-y-z
LOADED CHAMBER DATA

23. LOADED CHAMBER DATA
-35
-30
-25
-20
-15
-10
-5
0
0 200 400 600 800 1000 1200
ACF(dB)
Frequency (MHz)
Loaded Chamber ACF
EMPTY CHAMBER DATA
~7.3 dB average decrease from empty configuration

24. PROBLEMS AND SOLUTIONS

25. ISSUE 1:
TILE POWER DATA ELEMENTS BUG
y = 1.0032x - 0.0004
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0 0.5 1 1.5 2
MeasuredReversePower(Watts)
TILE Reverse Power (Watts)
Reverse Power TILE vs manual measurement
1.01
1.02
1.03
1.04
1.05
1.06
1.07
1.08
0 0.5 1 1.5 2 2.5 3
ManualForwardPower(Watts)
TILE Forward Power (Watts)
Forward Power TILE vs Manual Measurement
y = 0.974x + 0.0251
1.01
1.02
1.03
1.04
1.05
1.06
1.07
1.08
1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08
NetPowerManaul(Watts)
Forward Power Tile (Watts)
Forward Power TILE vs Net Power Manual Measurement
RESOLUTION
• Recognize TILE! Forward Power data
element as Net Power record
• Ignore TILE! Net Power data element
• If Forward power is needed,
compute as difference of reverse
and net power
THREAT LEVEL: LOW (SIMPLE USER END FIX)

26. ISSUE 2:
FIELD MONITOR BECOMES
UNRESPONSIVE
• Field Monitor occasionally
becomes unresponsive
• Monitor screen goes blank and
TILE! starts reading zero for
electric field components and
RMS
RESOLUTION
• Spot check TILE! dialogue and
field monitor readings frequently
• In case of failure, locate failure
point in .csv file (signaled by null
probe readings)
• Delete data for tuner steps with
null results
• Reboot TILE! and reinitialize test
phase at appropriate tile
THREAT LEVEL: ANNOYING
(EASY TO PREVENT BY SPOT MONITORING BUT TIME
CONSUMING IF UNNOTICED)

27. ISSUE 3:
STEP MOTOR SLOP
• Step motor advertised as having
1.8 degree step size
• Slop observed to be at least on
this order (partially due to
mechanical tuner fixture)
RESOLUTION
• Spot check tuner position on
occasion
• Tuner increment step size larger
than observed slop
• Ensure large sampling size
• Averaging over probe positions
should wash out problems
• Eliminate mechanical fixture
contribution
THREAT LEVEL: UNADVISABLE LONG TERM
(INTRODUCES AND PROPAGATES UNNECESSARY ERROR)

28. ISSUE 4:
MOTOR CTRL FAULTS
RESOLUTION
• Motor controller occasionally
faults and ceases operation
• TILE! Routine continues
collecting data unaware
• Spot check motor controller to ensure
FLT light is off and PWR light is green
• In case of fault:
1. Abort Test Sequence
2. Isolate failure point in .csv (signaled
by repetitious field probe readings
for subsequent tuner positions
(~1V/m similarity)
3. Delete these repeated data sets
from .csv
4. Clear motor controller error using
the “Clear Motor Ctrl Error” tile or
by power cycling the controller
5. Reinitialize test sequence at point
of failure
THREAT LEVEL: MODERATE
(WHILE EASY TO AVOID BY CONSISTENT SPOT
CHECKING, FAILURE CAN BE TIME
CONSUMING TO CORRECT IF LEFT UNNOTICED)

29. ISSUE 5: TX ANTENNA FIXTURE
• Transmit antenna should be
permanently affixed to chamber
• Movement or alteration of position
and alignment voids calibration
RESOLUTION
• Temporary: Tape
• Long Term: Solutions forthcoming
THREAT LEVEL: LOW
(CURRENT CONFIGURATION IS RELATIVELY RIGID: DO NOT BUMP)

30. ISSUE 6:
ANCIENT LAPTOP
RESOLUTION
• Forthcoming
THREAT LEVEL:
LOW TO MODERATE
(DATA BACKUP WILL AVOID
CATASTROPHIC CONSEQUENCES,
BUT RISK OF SUDDEN INTERRUPTION TO
OPERATIONAL CAPACITY IS NONTRIVIAL)

31. FUTURE WORK
• Continue development and
implementation of EUT TILE!
profile
• Continue certification process
for chamber
• Integrate Anaheim motor
controller driver into TILE!
(whenever it arrives)
• Calibrate at higher frequencies
with horn tx antenna (fewer
probe/rx antenna positions/test
frequencies required)
• Replace step motor with
another having finer step
precision
• Replace Test PC with newer
equipment
• Develop rigorous RC chamber
test procedures for JSC
• Test something

32. MY FUTURE

33. ACKNOWLEDGEMENTS AND DEEPEST THANKS
• Dr. Scully
• Xiang Ni
• Rick Deppisch
• Isreal Vences
• Wayne Cope
• Denise Romero
• Dr. Norgard
• Chuck Roberts, Victor Murray,
Dan Tran
• Missy Mathias