The Evolution of Complex Cavity Measurement
Techniques from Precision Metrology
Applications to Aircraft/Vehicle Electromagnetic
Environment Assessments
Dennis Lewis
The Boeing company
Associate Technical Fellow
RF / Microwave and Antenna Metrology
P.O. Box 3707 MC 19-LL
Seattle WA, 98124-2207
dennis.m.lewis@boeing.com
BOEING is a trademark of Boeing Management Company.
Copyright © 2012 Boeing. All rights reserved.
Agenda
 What is a Reverberation Chamber?
 Metrology Application of Reverberation Chambers
– Probe Calibration
 Measurement Advances
– Precision Network Analyzer Port Extenders
– Discrete Frequency Stirring (DFS)
 Measurement Applications
– Wireless (MIMO) Propagation Measurements
– Aircraft Shielding Effectiveness
– Leaky Feeder Antenna Propagation
– Portable Electronic Devices and Aircraft Antenna Coupling
Copyright © 2012 Boeing. All rights reserved.
What is a Reverberation Chamber?
Shielded enclosure / cavity in which the test
electromagnetic environment is statistically:
– Isotropic
– Randomly polarized
– Homogeneous
Copyright © 2012 Boeing. All rights reserved.
What is a Reverberation Chamber?
MODAL STRUCTURE
F63 IN TWO DIMENSIONAL REGULAR CAVITY
Permitted Modes
2
2
l  w  h 
f lwh ( MHz ) = 150   +   +  
 L  W   H 
2
Lowest allowable mode
2
2
1  1   0 
f110 ( MHz ) = 150   +   +  
 L  W   H 
Copyright © 2012 Boeing. All rights reserved.
2
What is a Reverberation Chamber?
MODAL STRUCTURE
F63 IN TWO DIMENSIONAL REGULAR CAVITY WITH STIRRER
Copyright © 2012 Boeing. All rights reserved.
What is a Reverberation Chamber?
Stepper Motor
Working
Volume
Tuner / Paddle
Coupler
>λ/4 from
Boundaries
RF Source
Power Meter
EUT Monitor
Spectrum/Network
Analyzer
Copyright © 2012 Boeing. All rights reserved.
Computer
What is a Reverberation Chamber?
Mean Norm Power (mW)
Mean Norm Power (dB)
CDF (Linear)
CDF (Log)
1.2
1
1
CDF
0.8
DATA
Theoretical
0.6
0.4
CDF (Log)
1.2
0.8
DATA
Theoretical
0.6
0.4
0.2
0.2
0
0
0
2
4
Data
Copyright © 2012 Boeing. All rights reserved.
6
8
-20
-15
-10
-5
Data
0
5
10
What is a Reverberation Chamber?
NIST Technical Note 1508
“Evaluation of the NASA
Langley Research Center
mode-Stirred Chamber
Facility”
Copyright © 2012 Boeing. All rights reserved.
What is a Reverberation Chamber?
Photos courtesy of ETS-Lindgren
NASA Glen Research Facility
(100 ft Diameter 120 ft. Tall)
Copyright © 2012 Boeing. All rights reserved.
What is a Reverberation Chamber?
737-400 Inside Paint Hangar
767-400 Inside Paint Hangar
Copyright © 2012 Boeing. All rights reserved.
Agenda
 What is a Reverberation Chamber?
 Metrology Application of Reverberation Chambers
– Probe Calibration
Measurement Advances
– Precision Network Analyzer Port Extenders
– Discrete Frequency Stirring (DFS)
 Measurement Applications
– Wireless (MIMO) Propagation Measurements
– Aircraft Shielding Effectiveness
– Leaky Feeder Antenna Propagation
– Portable Electronic Devices and Aircraft Antenna Coupling
Copyright © 2012 Boeing. All rights reserved.
Probe Calibrations
– NIST released a series of tech notes on recent work in the theory of
reverberation chamber measurements
• Work could be extended to higher levels of accuracy
• May be useful for antenna and field strength calibrations
Anechoic Chamber Calibrations
• Poor repeatability
• Least developed and automated of our capability
• Require reconfiguration of the test and measurement equipment
• Difficult to correct for multi-path signals
• Require the most accurate of antenna measurements
Copyright © 2012 Boeing. All rights reserved.
Probe Calibrations
Overlap for method
comparison
TEM Cell
Reverberation Chamber
Anechoic Chamber
200 MHz 250 MHz
Copyright © 2012 Boeing. All rights reserved.
40 GHz
Probe Calibrations
TEM Cell
• Transverse Electromagnetic Mode of
Propagation (primary mode)
• Allow higher order modes of propagation at
higher frequencies (TE, TM)
• Work very well at low frequencies
E=
P ∗ R V Volts
= =
d
d Meter
Copyright © 2012 Boeing. All rights reserved.
Probe Calibrations
Gain Extrapolation Range
Copyright © 2012 Boeing. All rights reserved.
Probe Calibrations
Reverb Chamber Method…
Copyright © 2012 Boeing. All rights reserved.
What is a Reverberation Chamber?
Reverb chamber
Paint hangar
Main passenger cabin
Copyright © 2012 Boeing. All rights reserved.
Agenda
 What is a Reverberation Chamber?
 Metrology Application of Reverberation Chambers
– Probe Calibration
 Measurement Advances
– Precision Network Analyzer Port Extenders
– Discrete Frequency Stirring (DFS)
 Measurement Applications
– Wireless (MIMO) Propagation Measurements
– Aircraft Shielding Effectiveness
– Leaky Feeder Antenna Propagation
– Portable Electronic Devices and Aircraft Antenna Coupling
Copyright © 2012 Boeing. All rights reserved.
Fiber Optic Port Extenders
 Boeing’s two-port DUT…
Copyright © 2012 Boeing. All rights reserved.
Fiber Optic Port Extenders
 Summing up our challenges…
Free-space Path Loss
Coax Cable Losses - Storm Cables
-20
0
10 ft
-30
25 ft
50 ft
Attenuation (dB)
Attenuation (dB)
-5
100 ft
-40
-50
-60
-70
-10
-15
-20
-80
16 ft cable
-25
-90
50 ft cable
100 ft cable
-30
-100
0
5
10
Frequency (GHz)
Copyright © 2012 Boeing. All rights reserved.
15
20
0
5
10
Frequency (GHz)
15
20
Fiber Optic Port Extenders
 Block diagram of fiber optic port extenders…
First Generation design jointly developed
by Miteq and Boeing – developed for use
with Agilent PNA
Allows for extension of PNA ports to
remote test points
– Remotes full 2-port capabilities
– Eliminates RF losses associated with
long cable runs
– Improves overall dynamic range of
measurement system
– Decouples analyzer from test points
– Provides magnitude and phase data
Copyright © 2012 Boeing. All rights reserved.
Fiber Optic Port Extenders
 Fiber Optic Port Extenders performance was evaluated at Agilent test facility using
PNA performance specifications
 Can pass PNA verification with port extenders
 Performed within PNA specification for dynamic accuracy in 10 to 110 dB attenuation
range
Copyright © 2012 Boeing. All rights reserved.
Fiber Optic Port Extenders
 Fiber optic port extenders allowed us to go from…
This…
to this!
and still improve on…
 Dynamic range
 Measurement accuracy/uncertainty
 Reduce transmit power / Increase FCC
frequency spectrum allocations
Copyright © 2012 Boeing. All rights reserved.
Agenda
 What is a Reverberation Chamber?
 Metrology Application of Reverberation Chambers
– Probe Calibration
 Measurement Advances
– Precision Network Analyzer Port Extenders
– Discrete Frequency Stirring (DFS)
 Measurement Applications
– Wireless (MIMO) Propagation Measurements
– Aircraft Shielding Effectiveness
– Leaky Feeder Antenna Propagation
– Portable Electronic Devices and Aircraft Antenna Coupling
Copyright © 2012 Boeing. All rights reserved.
DFS Measurement Technique
DFS is a measurement methodology for performing frequency stirred
measurements by making narrowband, stepped frequency measurements
across a broad frequency range as opposed to the more traditional method
of BLWGN or mechanical mode stirring
 Electrical perturbation of cavity fields (no mechanical paddle need for stirring) –
effected by frequency stepping the excitation source.
 “Frequency stir” by averaging over stirring bandwidth – need to consider sample size
and frequency resolution
 Frequency step size slightly larger than resonant mode bandwidth – generates
independent samples; determine analytically or trial-and-error (or both)
DFS advantages include…
 Simple setup (network analyzer, optical link, antennas) – easy to move around large
test article and easy to transport to remote test site
 Fast data acquisition – reduce test time, save $$
 Discrete measurement at each frequency step provides statistical data
Copyright © 2012 Boeing. All rights reserved.
DFS Measurement Technique (cont)
Discrete Frequency Stirring
Measurement of discrete data
samples allows for further
processing and statistical analysis
Copyright © 2012 Boeing. All rights reserved.
Statistical Analyses
DFS Measurement Technique (cont)
Copyright © 2012 Boeing. All rights reserved.
Agenda
 What is a Reverberation Chamber?
 Metrology Application of Reverberation Chambers
– Probe Calibration
 Measurement Advances
– Precision Network Analyzer Port Extenders
– Discrete Frequency Stirring (DFS)
 Measurement Applications
– Wireless (MIMO) Propagation Measurements
– Aircraft Shielding Effectiveness
– Leaky Feeder Antenna Propagation
– Portable Electronic Devices and Aircraft Antenna Coupling
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – Aircraft
Wireless MIMO Propagation
Wireless propagation measurements
Deliver DVD quality streamed unicast video to every seat
 Airplane is high multipath environment, but with curved boundary surfaces, how
correlated will multipath be?
 Need Coverage, Delay Spread, Angle of Arrival / Departure statistics to build a good
Airplane MIMO channel model
Copyright © 2012 Boeing. All rights reserved.
57
56
58
56
57
56
55
57
55
54
54
54
53
55
53
52
53
52
51
52
51
50
51
50
49
50
49
48
Conceptual coverage layout, 777-300
49
48
47
47
46
47
46
48
45
46
45
30
31
32
31
30
30
31
28
27
26
25
24
23
29
29
29
28
28
27
27
26
26
25
25
24
24
23
21
22
23
21
22
22
15
14
13
21
20
15
15
12
12
12
14
11
11
11
14
10
10
10
13
9
9
9
13
8
8
7
7
7
3A
8
3K
2H
2C
1A
2D
3G
1G
1K
– Optimize installation locations
– Optimize antennas types, orientations, spacing
– Optimize radio designs
Measurement Applications – Aircraft
Wireless MIMO Propagation
 Boeing built test setup as described in the online “Intel UWB and MIMO
Channel Measurement Database”
– Use Network Analyzer (Agilent PNA series) to sweep frequency response of
channel between Tx and Rx antennas
– Stepper motor translation stages allow measurements between closely
spaced Tx or Rx antenna locations over grid area
 e.g., ¼ lambda over 12” square
 Using variety of FFTs and IFFTs over frequency or space lets us calculate
– Statistical delay spreads
– Correlation between antenna location points
– Angle of Arrival / Departure vs. time
 We can combine some of these to build airplane MIMO channel model
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – Aircraft
Wireless MIMO Propagation
Wireless propagation measurements
Copyright © 2012 Boeing. All rights reserved.
Channel Sounding
Translation Stages
Measurement Applications – Aircraft
Wireless MIMO Propagation
Reverb Chamber Results
Energy across X-Z grid
Energy vs. Polar Direction
Energy/Angle vs. Time
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – Aircraft
Wireless MIMO Propagation
Wireless propagation measurements
Angle of Arrival over Time (S
-150
-100
Angle (deg)
-50
0
50
100
150
0
0.5
1
1.5
Example Angle Spectrum
DC-10 Seat 51E
60
58
59
2
56
57
55
54
53
52
51
50
49
48
47
46
45
32
58
60
57
59
1
57
56
PNA
58
56
55
55
54
54
53
53
3
52
52
51
51
50
50
49
49
48
48
47
47
46
46
45
32
32
45
5, 6
31
31
7
59
TX 1
30
Copyright © 2012 Boeing. All rights reserved.
31
30
Time (sec)
Agenda
 What is a Reverberation Chamber?
 Metrology Application of Reverberation Chambers
– Probe Calibration
 Measurement Advances
– Precision Network Analyzer Port Extenders
– Discrete Frequency Stirring (DFS)
 Measurement Applications
– Wireless (MIMO) Propagation Measurements
– Aircraft Shielding Effectiveness
– Leaky Feeder Antenna Propagation
– Portable Electronic Devices and Aircraft Antenna Coupling
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – Aircraft Shielding
–Three distinct types of measurements can be
used during aircraft test (all utilizing the DFS
measurement technique)
–Direct Illumination Shielding Measurements
(HIRF)
–Reverberant Shielding Measurements (Nested
Chamber)
–Reverberant Attenuation & Q Factor
Measurements
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – Aircraft Shielding
High Intensity Radiated Fields
(HIRF) Certification Testing:
Greater than 200 meters of
cables
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – Aircraft Shielding
HIRF Measurements
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – Aircraft Shielding
– Directly illuminate device under test with transmit antenna; can be used
to directly illuminate apertures of concern
– Can be used to determine a worst case shielding number
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – Aircraft Shielding
– Reverb shielding measurements
utilize a “nested” chamber approach –
paint hanger used as outer chamber,
aircraft fuselage considered to be the
inner chamber
– Shielding number produced is an
average over all incident angles and
polarizations
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – Aircraft Shielding
 Hanger Insertion Loss for empty hanger (REF1) and for hanger with
aircraft (REF2)…
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – Aircraft Shielding
– Measurement of antenna-to-antenna gain / attenuation when both
transmit and receive antennas are located inside the device under test
– Provides an indirect assessment of cavity Q and can reveal changes
to internal cavity electrical characteristics
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – Aircraft Shielding
Copyright © 2012 Boeing. All rights reserved.
Agenda
 What is a Reverberation Chamber?
 Metrology Application of Reverberation Chambers
– Probe Calibration
 Measurement Advances
– Precision Network Analyzer Port Extenders
– Discrete Frequency Stirring (DFS)
 Measurement Applications
– Wireless (MIMO) Propagation Measurements
– Aircraft Shielding Effectiveness
– Leaky Feeder Antenna Propagation
– Portable Electronic Devices and Aircraft Antenna Coupling
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – Leaky Feeder
Antenna Measurements
Patch Antenna
Leaky Feeder
o Transmitting with either two patch antennas located in mid-cabin zone or with combination of leaky
coax configuration and receiving with the discone antennas
o Three leaky coax transmit configurations: All leaky coax (161ft), leaky-std coax-leaky (mid section is
68ft standard coax) and aft leaky coax only (50 ohm termination plugs inserted at end of aft section
leaky coax run)
o Flight deck antenna was measured with flight deck door open and closed
o Ground test was run on both unshielded and shielded airplane configuration
o Transmit frequencies were 872 MHz, 1962 MHz, and 2148 MHz (cellular, PCS and WCDMA/UMTS
bands)
Copyright © 2012 Boeing. All rights reserved.
5 dB/Div
Measurement Applications – Leaky Feeder
Antenna Measurements
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – Leaky Feeder
Antenna Measurements
Laptop
location
Row 2
Row 4
Row 24
Row 29
Row 47
Row 51
Row 56
Copyright © 2012 Boeing. All rights reserved.
LF Coax
Antenna
Agenda
 What is a Reverberation Chamber?
 Metrology Application of Reverberation Chambers
– Probe Calibration
 Measurement Advances
– Precision Network Analyzer Port Extenders
– Discrete Frequency Stirring (DFS)
 Measurement Applications
– Wireless (MIMO) Propagation Measurements
– Aircraft Shielding Effectiveness
– Leaky Feeder Antenna Propagation
– Portable Electronic Devices and Aircraft Antenna Coupling
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – PEDs and
Aircraft Antenna Coupling
The number of consumer portable electronic devices (PEDs) available are
increasing exponentially, as are the number of PEDs finding their way
onboard aircraft.
The FAA requested that RTCA, Inc. form a special committee to present an
up-to-date evaluation of the use of PEDs.
 Particular attention was to be paid towards intentionally transmitting PEDs
(T-PEDs) such as mobile phones, wireless RF network devices, and other
wireless-enabled devices.
 Phase 1 – current T-PED technologies
 Phase 2 – upcoming, next-generation T-PED technologies plus guidance
for airplane design and certification.
RTCA SC-202 WG5 was tasked with creating document (DO-307) that
addresses design & certification of new aircraft to be PED-tolerant
DO-307 specifies Interference Path Loss (IPL) targets and RF immunity
requirements for aircraft systems (front door & back door interference)
For certification, IPL targets for each receiver will be demonstrated by an
IPL test procedure recommended in DO-307
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – PEDs and
Aircraft Antenna Coupling
Regulatory Agencies
FAA (Flight Standards, Aircraft Certification, Spectrum Management), UK-CAA, Transport Canada,
DGAC-France, FCC
Airlines
United, Delta Air Lines, US Airways, Continental, Northwest, American, Lufthansa, JAL, ANA,
FedEx, UPS, Southwest, QANTAS, Air Wisconsin, ANA
Airplane Manufacturers
Airbus, Cessna, Boeing, Bombardier, Embraer
Avionics Manufacturers
Rockwell-Collins, Honeywell, Connexion, Matsushita, General Dynamics, Teledyne, AirCell, Row 44
Consumer Electronics
Verizon, Intel, Sony-Erickson, Panasonic, QUALCOMM, XCube Communications, CEA, Sony,
Motorola, Dell, CTIA, Freescale Semiconductor
Associations, Universities, Agencies
NASA, UofOK, ARINC, SITA, ALPA, AFA, IATA, EUROCAE, Carnegie Mellon
Aviation Industry Consultants
CAVOK International, Alion, Eagle’s Wings, AJ Systems, Overlook Systems
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – PEDs and
Aircraft Antenna Coupling
Interference Path Loss (IPL) is the amount of
attenuation experienced by unintentionally radiated
signals originating within an aircraft interior region
(zone) as they propagate through aircraft structure to
aircraft antennas and in to RF receivers
Interference signals are in-band of aircraft
communication, navigation and surveillance radios
Frequencies range from VHF (108 MHz) to Microwave
Landing System (5090 MHz)
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – PEDs and
Aircraft Antenna Coupling
Copyright © 2012 Boeing. All rights reserved.
Measurement Applications – PEDs and
Aircraft Antenna Coupling
Copyright © 2012 Boeing. All rights reserved.
Summary

Probe calibration in reverberation chambers
 Comparable uncertainties to Anechoic chambers
 More repeatable than anechoic chamber method.
 Eliminates alignment problems

Optical Port Extenders
 Eliminates RF losses associated with long cable runs
 Maintain the ability to perform full 2-port vector corrected measurements
 Simplify hardware setup and maintenance
 Performed within PNA specification over 120dB dynamic range

Measurement applications
 Provides a more accurate assessment of EM environment over deterministic
approach
 Uncertainty is known
 Bounds the problem
 Significant reduction in test times while providing more data
 Reduce transmit power / Increase FCC frequency spectrum allocations
 DFS measurement technique used to make reverberation chamber type
measurements of attenuation provided by aircraft structure.
Copyright © 2012 Boeing. All rights reserved.
Questions?
Copyright © 2012 Boeing. All rights reserved.