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TRANSCRIPT
1
MIMO and other Wireless Measurements in
Reverberation Chambers at NIST
Presented by: William Young
C. L. Holloway, K.A. Remley, J. Ladbury, G. Koepke, W.F. Young,
R. Pirkl, E. Genender, S. Floris, H. Fielitz
National Institute of Standards and Technology
Electromagnetics Division
Boulder, Colorado
303-497-3471, email: [email protected]
July 2011, SPOKANE, WA
Content
• Basics of Radio Frequency Reverberation
Chambers
• Key Reverberation Chambers Characteristics for
Wireless Measurements
• Creating Realistic Environments for Testing
Wireless Devices
• Reverberation Chamber Test Environments for
MIMO Systems
2
BASICS OF RADIO
FREQUENCY
REVERBERATION CHAMBERS
OPEN AREA TEST SITES (OATS)
Problems:Ambients
Reflections
Scanning
Interference
Positioning
3
ANECHOIC CHAMBER
Problems:Low Frequencies
Reflections
Positioning
Directional Antennas
REVERBERATION CHAMBER
Why use a reverberation chamber?
1) Relatively inexpensive
2) Relatively fast
3) Multipath environment- useful
for MIMO testing
4
Commercial Solutions…
• Stirrer
• Turntable
Reverberation chambers are being used for a
wide range of EM and EMC measurements.
Reverberation Chamber
D-U-TTransmit Antenna
Receive AntennaProbe(s)
Transmit Instrumentation:
Signal Generator
Amplifier
Directional coupler
Power Meter(s)
etc.
Motor Control
Control and Monitoring
Instrumentation for
Device-under-test
Receive Instrumentation:
Spectrum Analyzer
Receiver, Scopes
Probe System
etc.
5
Fields in a Metal Box (A Shielded Room)
•In a metal box, the fields have well defined modal field distributions.
Locations in the chamber with very high field values
Locations in the chamber with very low field values
Frozen Food
Fields in a Metal Box with Small Scatterer
(Paddle)
In a metal box, the fields have well defined modal field distributions.
Small changes in locations where very high field values occur
Small changes in locations where very low field values occur
6
Fields in a Metal Box with Large Scatterer (Paddle)
Large changes in locations where very high field values occur
Large changes in locations where very low field values occur
In fact, after one fan rotation, all locations in the chamber will have nearly the
same maxima and minima fields.
Stirring MethodTIME DOMAIN
Click to play paddle
rotation
750MHz
Paddle
7
Reverberation Chamber: All Shape and Sizes
Large Chamber
Small Chamber
Moving walls
Huge ChamberNASA: Glenn Research Center
Original Applications
• Radiated Immunity
components
large systems
• Radiated Emissions
• Shielding
cables
connectors
materials
• Antenna efficiency
• Calibrate rf probes
• RF/MW Spectrograph
absorption properties
• Material heating
• Biological effects
• Conductivity and
material properties
8
KEY REVERBERATION
CHAMBER
CHARACTERISTICS FOR
WIRELESS MEASUREMENTS
Wireless Applications
• Radiated power of mobile phones
• Antenna efficiency measurements
• Measurements of receiver sensitivity of mobile terminals
• Investigating biological effects of cell-phone base-station RF exposure
• Device testing in emulated Rayleigh multipath environments
• Device testing in emulated Rician multipath environments
• Gain obtained by using diversity antennas in fading environments
• Measurements on multiple-input multiple-output (MIMO) systems
9
Standardization of Wireless Measurements
Can we use a reverberation chamber as a reliable and
repeatable test facility that has the capability of simulating
key multipath environments for the testing of wireless
communications devices?
If so, such a test facility will be useful in wireless
measurement standards.
Testing Application: Total Radiated Power
from Cell-PhonesData from CTIA working group on total radiated power (TRP) testing:
TRP Comparison, Free Space, Slider Open, W-CDMA Band II
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
Low Mid High
Reference Channel
Re
lati
ve
TR
P
Anechoic Lab A Band II
Anechoic Lab B Band II
Anechoic Lab C Band II
Reverb Lab A Band II
Reverb Lab B Band II
Reverb Lab C Band II
Reverb Lab D Band II
Reverb Lab E Band II
TRP Comparison, Free Space, Slider Open GSM850
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
Low Mid High
Channel
Re
lati
ve
TR
P
Anechoic Lab A GSM850
Anechoic Lab B GSM850
Anechoic Lab C GSM850
Reverb Lab A GSM850
Reverb Lab B GSM850
Reverb Lab C GSM850
Reverb Lab D GSM850
Reverb Lab E GSM850
Reverb chamber
data has less
variability than
the anechoic data!
10
Can we model multipath environments in a
reverberation chamber?
Reverberation Chambers are
Natural Multipath Environments
11
Reverberation Chamber Provides a
Statistically Uniform Channel
21
1.5 GHz 2.5 GHz
• At a single frequency, observed received power is not uniformly distributed over azimuth.
Power vs. Azimuth Angle
Channel is Frequency Dependent
22
Power vs. Azimuth Angle: Paddle Configuration A
• Strong frequency dependence is indicative of an isotropic scattering environment.
• Constructive and destructive interference cause peaks and nulls.
12
Power vs. Azimuth Angle: 3.6 MHz BW
1.5 GHz 2.5 GHz
23
• Received power is distributed more uniformly when observed over some bandwidth.
Multipath Environments
Extensive measurements have shown that when light of sight (LOS) path is present
the radio multipath environment is well approximated by a Ricean channel, and
when no LOS is present the channel is well approximated by a Rayleigh channel:
The Amplitude of E is either Rayleigh or Ricean depending if a LOS path is present.
Urban Environment Rural Environment
13
Ricean K-factor
componentsscattered
componentdirectk or K = 10Log(k)
K=10 dBK=4 dB
K=1 dBK= -∞ dB
(Rayleigh)
K-factor:
Typical Reverberation Chamber Set-up
Antenna pointing away from probe (DUT)
Paddle
Transmitting Antenna
metallic walls
DUT
a
a
A Rayleigh test environment
Can we generate a Ricean environment?
14
Chamber Set-up for Ricean Environment
Antenna pointing toward (DUT)
We will show that by varying the characteristics of the reverberation
chamber and/or the antenna configurations in the chamber, any desired
Rician K-factor can be obtained.
Paddle
DUT
Transmitting Antenna
metallic walls
Reverberation Chamber Ricean Environment
Calculating the Ricean K-factor in a reverberation chamber [1]
• K is proportional to D. This suggests that if an antenna with a well defined antenna
pattern is used, it can be rotated with respect to the DUT, thereby changing the K-factor.
•If r is large, K is small (approaching a Rayleigh environment)
•If r is small, K is large. This suggests that if the separation distance between the antenna
and the DUT is varied, then the K-factor can also be changed to some desired value.
•By varying Q (the chamber quality factor), the K-factor can be changed.
• If K becomes small, the distribution approaches Rayleigh.
Thus, varying all these different quantities in a judicious manner can result in
controllable K-factor over a reasonably large range.
15
Measured K-factor for Chamber Loading
The thick black curve running over each data set represents the K-factor obtained
by using d determined in the anechoic chamber.
1.0E-02
1.0E-01
1.0E+00
1.0E+01
1.0E+02
1.0E+03
1000 2000 3000 4000 5000 6000 7000
Frequency (MHz)
K-f
ac
tor
2 pcs absorber
6 pcs absorber
0 pcs absorber
Simulating Propagation Environments
with Different Impulse Responses and RMS Delay Spreads
0 1000 2000 3000
2
4
6
8
10x 10
-12
Delay (ns)
PD
P (
linear)
Rx8rms
= 105 ns
Ground Plane
Transmitting
antenna
tripods
62 inches
VNA
Port 1 Port 4
200 m
Optical
Fiber
Receiving
antenna
Fiber Optic
Receiver
OpticalRF
Fiber Optic
Transmitter
OpticalRF
0 1000 2000 3000
1
2
3
4
5
6
7
x 10-13
Delay (ns)
PD
P (
linear)
Rx12rms
= 232 ns
16
S21 Measurements: Loading the Chamber
Impulse Responses and Power Delay Profiles
Loading the Chamber
Power Delay Profile:
where h(t) is the Fourier transform of S21(w)
17
RMS Delay Spreads from Q measurements
where K is the K-factor and a threshold.
Thus, once we have Q, we can estimate rms
Impulse Responses and RMS Delay Spreads
for Different Ricean K-factors
18
Same Absorber, Different PDPs
0 500 1000 1500 2000-130
-120
-110
-100
-90
-80
-70
-60
Mean Power Delay Profile (100 steps)
Delay (ns)
Po
we
r D
ela
y P
rofil
e (
dB
)
Horn Indirect 1, Absorber A
Horn Indirect 2, Absorber A
Horn Indirect 1, Absorber B
Horn Indirect 2, Absorber B
Horn Indirect 1, Absorber C
Horn Indirect 2, Absorber C
Horn Direct CoPol, Absorber B
Horn Direct XPol, Absorber B
0 500 1000 1500 2000-130
-120
-110
-100
-90
-80
-70
-60
Mean Power Delay Profile (100 steps)
Delay (ns)
Po
we
r D
ela
y P
rofil
e (
dB
)
Horn Indirect 1, Absorber A
Horn Indirect 2, Absorber A
Horn Indirect 1, Absorber B
Horn Indirect 2, Absorber B
Horn Indirect 1, Absorber C
Horn Indirect 2, Absorber C
Omni Direct CoPol, Absorber B
Omni Direct XPol, Absorber B
•Different antenna types can impact PDP, just as absorber can
Horns Omnis
Instantaneous Results Can Vary
0 20 40 60 80 1000
20
40
60
80
100
120
140
160
180
200
Paddle Position
RM
S D
ela
y S
pre
ad
(n
s)
RMS Delay Spread at Each Paddle Position
3 Abs Floor, Horn Pos 1
3 Abs Floor, Horn Pos 2
1 Abs Floor, 2 Abs Raised, Horn Pos 1
1 Abs Floor, 2 Abs Raised, Horn Pos 2
3 Abs Raised, Horn Pos 1
3 Abs Raised, Horn Pos 2
0 100 200 300 400 500 600 700 8000
2
4
6
8
10
12
14
16
18
20
Delay (ns)
Po
we
r D
ela
y P
rofil
e (
line
ar
un
its)
All PDPs, Antenna Position 2a, Abs Ht 2, Xpol
19
BER Measurements – setup*Agilent 4438C Vector Signal Generator
Agilent 89600 Vector Signal Analyzer
External trigger
Firewire connection
to control VSA
GPIB connection
to control VSG
Reverberation chamber
*Mention of products by name does not imply endorsement
by NIST. Other products may work as well or better.
BER Measurements*Calibration: determine delay between received external trigger and the first demodulated bit of the
pattern
This offset depends on the signal bit rate.
Measurement: VSG repeatedly transmits an a priori known bit pattern
VSA locks on the external trigger and stores the received bit pattern
VSA integrates the signal spectrum to find the received signal power
LabVIEW: receives the bits from the VSA
corrects for the determined offset
calculates the BER
Each measurement is
finished when the BER
has settled
This measurement is repeated
for a range of VSG transmit powers
0 0.5 1 1.5 2 2.5 3 3.5
x 106
0
0.01
0.02
0.03
0.04
0.05
0.06
Number of received bits [N]
BE
R
BER running average - 24.3 ksps BPSK with slow paddle speeds
VSG transmit power: -65 dBm
VSG transmit power: -55 dBm
VSG transmit power: -45 dBm
*Mention of products by name does not imply endorsement by NIST. Other products may work as well or better.
20
BER Measurements
BER for a 243 ksps BPSK signal
BER for a 786 ksps BPSK signal
CREATING REALISTIC
ENVIRONMENTS FOR
TESTING WIRELESS DEVICES
21
Difficult Radio Environments
NIST is measuring signal penetration and multipath in representative emergency response
environments to provide data for improved wireless device design, standards development,
and better channel models.
Apartment Building
Oil RefineryOffice Corridor
Subterranean Tunnels
Small Chamber = Large Structure?
•Omnidirectional antennas
•Instantaneous differences (even if mean characteristics match)
•Monotonic, exponential decay
•Decay time
0 1000 2000 3000
2
4
6
8
10x 10
-12
Delay (ns)
PD
P (
linear)
Rx8rms
= 105 ns
0 1000 2000 3000
1
2
3
4
5
6
7
x 10-13
Delay (ns)
PD
P (
linear)
Rx12rms
= 232 ns
22
Example: Denver High-Rise Building Tests
North
South
East
West1
2
35
4
67
8109
11121314
1516
21
20
19
18
17
VNA measurement test locations are in pink
Ground Plane
Transmitting
antenna
tripods
62 inches
VNA
Port 1 Port 4
200 m
Optical
Fiber
Receiving
antenna
Fiber Optic
Receiver
OpticalRF
Fiber Optic
Transmitter
OpticalRF
Can we replicate the Denver high-rise in a
reverberation chamber?
absorber
wireless device
antenna
mode stirrers
horn antenna
Reverberation chamber with absorbing material
and phantom head0 50 100 150 200 250 300 350 400 450 500
time (ns)
-70
-65
-60
-55
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
Po
we
r D
ela
y P
rofile
(d
B)
1 absorber: rms=187 ns
3 absorber: rms=106 ns
7 absorber: rms=66 ns
Large office biulding
rms=59 ns
23
Can the reverberation chamber simulate an oil
refinery?Power Delay Profile in an oil refinery.
Lab-Based Test Method
North
South
East
West1
2
35
4
67
8109
11121314
1516
21
20
19
18
17
VNA measurement test locations are in pink
Location and
Notes
Test Point VNA Loss
Data (dB)
Path Loss
@700 MHz
(dB)
RMS Delay
Spread @700
MHz
(ns)
Republic
Notes:
- System 1
repeater at test
point 2.
1 7.23 68.6149 44.99
2 27.06 88.4449 39.52
3 38.15 99.5349 52.30
4 37.60 98.9849 133.41
5 37.18 98.5649 81.25
6 42.26 103.6449 102.78
7 46.04 107.4249 138.29
8 44.88 106.2649 104.69
9 48.30 109.6849 376.10
10 45.34 106.7249 338.17
11 50.25 111.6349 167.91
12 50.48 111.8649 231.57
13 50.98 112.3649 209.07
14 51.82 113.2049 192.25
15 49.60 110.9849 240.20
16 44.64 106.0249 377.45
17 29.28 90.6649 296.87
18 30.45 91.8349 161.75
19 42.24 103.6249 429.90
20 39.30 100.6849 333.25
21 47.07 108.4549 453.47
Compare wireless device performance measured in the field to performance in the
reverberation chamber
24
Adding More Realism to the PDP
T
T
R12
T1
T2
T3
R12
R9
R5
R10
•Mean of 27 NLOS
measurements made in Denver
urban canyon.
•Channel characterization and
PASS device measurements.
0 200 400 600 800 1000 1200
-170
-160
-150
-140
-130
-120
-110
-100
-90
Delay (ns)
PD
P (
dB
)
TX1 to RX5rms
= 115 ns
Noise Threshold = -116 dB
0 500 1000
-170
-160
-150
-140
-130
-120
-110
Delay (ns)P
DP
(dB
)
TX1 to RX9rms
= 39 ns
Noise Threshold = -116 dB
Clustering of Multipath is Common
0 100 200 300 400 500 600 700 800 900 10000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Delay [ns]
PD
P
fitted simulated data
measured Data Denver
RX
TX
Shortest path
Welton Street
17
th
Str
ee
t
Glenarm Pl
TX
RX
1
RX
2
RX
3
Transmitter Site
Parking lot
Mean of 27 NLOS
measurements
Clusters of
exponential
distributions off of
buildings
25
Channel Emulator (CE) and Vector Network
Analyzer (VNA) used with a Reverberation
Chamber
Generate a Complex Power Delay Profile [8]
26
REVERBERATION CHAMBER
TEST ENVIRONMENTS FOR
MIMO SYSTEMS
Motivation
Alternative transmit/receive
configurations can improve wireless
reception in weak-signal and multipath
environments
To verify performance of multiple
antenna algorithms, testing in a
multipath environment is desirable
We discuss methods for implementing
such test environments using
reverberation chambers
TX RX
TX RX
TX RX
TX RX
SISO
MISO
SIMO
MIMO
27
Measurement Set-up
VSG 1
VSA
LO in
LO out
I out
Q out
Event 1
RF out
VSG 2
LO in
LO out
I in
Q in
Event 1
RF out
Pattern sync.
LO in RF in
IEEE 1394
Firewire
GPIB
Reverberation chamber
Stirrer
GPIB
•Multiple TX simulated using 2
VSGs
•Vector signal analyzer provides
channel power and demodulated
data
•BPSK modulated signal;
random, equal distribution; 2048
bits
•Error correction only to recover
constellation after deep fade
•Paddle stepped
Test Methodology
INITInitialize the stirrer
Initialize the VSA
Beamforming?
Recording data
Stepping the stirrers
Switch antenna!Tells the user to switch to a
different antenna
Storing the data to file
Exiting the program
BeamformingShifting the phase until
maximum power is reached
at the receiver
Recording data
Switch antenna!Tells the user to switch to a
different antenna
Stepping the stirrers
All steps done?
All antennas
used?
All steps done?
All antennas
used?
Yes
No
No
Yes
Yes
No
Yes
No
No
Yes
•One receiver is used: repeatability and
post processing are key
•Careful synchronization of
generators, receiver, paddles required
•Post processing implements diversity,
MIMO schemes
•System is automated to prompt user
for correct inputs
•System applicable for design (laptop
antennas, for example) and test of
algorithms
28
NIST Chamber Characteristics
•Chamber dimensions:
4.28m x 3.66m x 2.90m
•Two paddles: vertical
and horizontal
•Table shows Q, RMS
delay spread, and
coherence bandwidth
for various numbers of
absorbing blocks
Absorber Q τ RMS [ns] Δf [MHz]0 47130 3121.99 0.321 8505 563.38 1.772 3319 220.08 4.543 2051 136.01 7.354 1479 98.06 10.205 1407 93.32 10.716 1067 70.66 14.147 918 60.82 16.428 765 50.71 19.729 731 48.48 20.62
10 550 36.49 27.4011 551 36.55 27.3612 435 28.83 34.6813 399 26.47 37.7714 369 24.48 40.8415 340 22.57 44.3016 332 22.03 45.38
•No choice of received signal •Antenna orientation sets level of
direct vs. reflected signal in the
reverb chamber
SISO
Real life Simulation in reverberation chamber
Transmitter Receiver
Vector
Signal
Generator
Vector
Signal
Analyzer
Reverberation
chamber
Stirrer
29
•Also called Diversity
•Power meter monitors
received signal strength
•Strongest signal
demodulated by receiver •VSA provides channel power
•Data from strongest signal
chosen in post processing
SIMO
Real life Simulation in reverberation chamber
Transmitter Receiver
Vector
Signal
Generator
Vector
Signal
Analyzer
Reverberation
chamber
StirrerA
B
Antenna A receives strongest
signal
Switch
B
A
Data A RX Power A
Data B RX Power B
RX Power A is strongest
In post processing Data A is selected
•TX antennas phase adjusted
to maximize received signal
•Received signal strength
relayed to transmitter
•Strongest signal demodulated
by receiver
•VSGs are phase locked
• Phase swept 360°
•Strongest channel power
chosen in post processing
TX BEAMFORMING
Real life Simulation in reverberation chamber
Transmitter Receiver
Vector
Signal
Analyzer
Reverberation
chamber
Stirrer
Phase
Signal strength
Vector Signal
Generator 2
Phase
Vector Signal
Generator 1
Signal strength
30
•Phasing of RX antennas
adjusted based on received
signal strength
•Strongest signal demodulated
by receiver
RX BEAMFORMING
Real life
Transmitter Receiver
Phase
Not implemented in the
simulation yet
Various schemes:•Precoding (like beamforming)
•Spatial multiplexing (data
broken into multiple streams, TX
on uncorrelated channels)
•Diversity coding (identical data
streams TX using orthogonal
codes. RX decides which one to
use)
•MISO => MIMO using post
processing
MIMO
Real life Simulation in reverberation chamber
Transmitter Receiver
Vector
Signal
Generator 1
Vector
Signal
Analyzer
Reverberation
chamber
Stirrer
Switch
B
A
Data A-C RX Power A-C
Data A-D RX Power A-D
Data B-C RX Power B-C
Data B-D RX Power B-D
Vector
Signal
Generator 2
C
D
31
Simulation of various MIMO
schemes:•Precoding: TX beamforming
used.
•Spatial multiplexing: TX data
start time not sufficiently precise
for simultaneous transmit. One
TX, one RX used in multiple
combinations. Data recombined in
post processing.
•Diversity coding: One RX so
only one code implemented. VSA
reports channel power, strongest
path chosen.
MIMO
Real life Simulation in reverberation chamber
Transmitter Receiver
Vector
Signal
Generator 1
Vector
Signal
Analyzer
Reverberation
chamber
Stirrer
Switch
B
A
Data A-C RX Power A-C
Data A-D RX Power A-D
Data B-C RX Power B-C
Data B-D RX Power B-D
Vector
Signal
Generator 2
C
D
Measured Results:
Various Data Rates
Frequency = 2.4 GHz
Pout = -50 dBm
BPSK modulated signal
•Best performance:
RX diversity with TX beamforming
and MIMO
•Huge increase in BER for high data
rates may be affected by coherence
BW of chamber
0
5
10
15
20
25
30
768 ksps
1 Msps 2.5 Msps
3 Msps5 Msps 10 Msps
BER
[%
] SISO
Receive diversity (MISO)
MIMO without beamforming
0
5
10
15
20
25
30
768 ksps
1 Msps
2.5 Msps
3 Msps
5 Msps
10 Msps
BER
[%
] TX beamforming (SIMO)
Receive diversity with TX beamforming
MIMO
32
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
1 2 3 4 5 6 7 8 9
10
11
12
BE
R [
%]
Number of absorbers inside chamber
BER SISO
BER MISO
BER SIMO
BER MIMO no Beamforming
BER MIMO
Number of Absorbers
Frequency = 2.4 GHz
Pout = -50 dBm
BPSK modulated signal, 768 ksps
70%
Non-line-of-sight: Nested Reverberation Chamber
Line of sight,
no nested chamberLine of sight, with
nested chamber
No line of sight,
with nested chamber
1. The paddle in the outer
chamber is turned through
100 positions, over 360⁰.
2. Paddle in the nested chamber
is turned continuously.
33
Nested Chamber Wireless Environment
0
50
100
150
200
250
300
0 10 20 30 40 50 60 70 80
RM
S D
elay S
pre
ad (
ns)
Threshold (dB)
LOS, w/o nested chamber
LOS, w/ nested chamber, w/ small paddle
NLOS, w/nested chamber, w/o small paddle
NLOS, w/ nested chamber, w/ small paddle
1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6-21
-18
-15
-12
-9
-6
-3
0
mean K values: -4.3 -5.3 -6.9 -10.7
Frequency, (GHz)
K-F
acto
r, (
dB)
LOS, w/o nested chamber
LOS w/ nested chamber, small paddle
NLOS w/ nested chamber, w/o small paddle
NLOS w/ nested chamber, w/ small paddle
Nested Chamber
Network
Analyzer
Large, outer
Chamber
MIMO Antenna
(Ports 1 & 2)
MIMO Antenna
(Ports 3 & 4)
Measuring MIMO Channel Correlation using a Nested
Reverberation Chamber
1 2 3 40
0.2
0.4
0.6
0.8
1
Chamber Configuration
|S
#,S
#|
S42,S24
S42,S41
S41,S31
S42,S32
S41,S32
S31,S32
Low correlation in
S-parameters =
good MIMO channel
Chamber Configurations (2.4 GHz):
1) No stirring in small chamber
2) Stirring in both; no RF absorbers
3) Stirring in both, one RF absorber
4) Stirring in both, two RF
absorbers
34
Correlation in the Nested Chamber MIMO Channels
(2.4 GHz)Without small paddle stirring
S13 S14 S23 S24 S31 S32 S41 S42
S13
S14
S23
S24
S31
S32
S41
S42
With small paddle stirring
S13 S14 S23 S24 S31 S32 S41 S42
S13
S14
S23
S24
S31
S32
S41
S42
With small paddle stirring
and one absorber
S13 S14 S23 S24 S31 S32 S41 S42
S13
S14
S23
S24
S31
S32
S41
S42
With small paddle stirring
and two absorbers
S13 S14 S23 S24 S31 S32 S41 S42
S13
S14
S23
S24
S31
S32
S41
S42
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Reverberation Chamber Standards Proposed
Testing MethodsStandards
•International Standard IEC 61000-4-21: Testing and
measurement techniques – Reverberation chamber test methods
•3rd Generation Partnership Project (3GPP) RAN4
– R4-111690, “TP for 37.976: LTE MIMO OTA Test Plan for
Reverberation Chamber Based Methodologies”
Testing Methods•CTIA Certification Program Working Group Contribution
– RCSG090101, P.-S. Kildal and C. Orlenius, “TRP and TIS/AFS
Measurements of Mobile Stations in Reverberation Chambers (RC)”
• “Utilizing a channel emulator with a reverberation chamber to
create the optimal MIMO OTA test methodology”
– C. Wright, S. Basuki, [8]
35
Challenges and Opportunities in Reverberation
Chamber Wireless Testing
• Direct path with omnidirectional antennas
• Tuning decay times = field non-uniformity
• How to test devices with repeaters
• Creating complicated PDPs for wireless device test
• Automating PDP development
• Advanced transmission, multiple antenna systems
• Test methods (CTIA, 3GPP groups)
• Angle of arrival measurements
• Uncertainties
Conclusions and Observations
1. Reverberation chambers represent reliable and repeatable test facilities that have
the capability of simulating any multipath environment for the
testing of wireless communications devices.
2. Such a test facility will be useful in the testing of the operation and
functionality of the new emerging wireless devices in the future.
3. Such a test facility will be useful in wireless measurements standards.
• Radiated power of mobile phones
• Receiver Sensitivity
• Gain obtained by using diversity antennas in fading environments
• Antenna efficiency measurements
• Measurements on multiple-input multiple-output (MIMO) systems
• Emulated channel testing in Rayleigh multipath environments
• Emulated channel testing in Rician multipath environments
• Measurements of receiver sensitivity of mobile terminals
• Investigating biological effects of cell-phone base-station RF exposure
36
References from NIST on Wireless Measurements
in Reverberation Chambers [1] C.L. Holloway, D.A. Hill, J.M. Ladbury, P. Wilson, G. Koepke, and J. Coder, “On the Use of Reverberation
Chambers to Simulate a Controllable Rician Radio Environment for the Testing of Wireless
Devices”, IEEE Transactions on Antennas and Propagation, Special Issue on Wireless
Communications, vol. 54, no. 11, pp. 3167-3177, Nov., 2006.
[2] E. Genender, C.L. Holloway, K.A. Remley, J.M. Ladbury, G. Koepke, and H, “Simulating the Multipath
Channel with a Reverberation Chamber: Application to Bit Error Rate Measurements,” IEEE
Transactions on EMC, vol. 52, no 4, pp. 766 – 777, Nov. 2010.
[3] E. Genender, C.L. Holloway, K.A. Remley, J. Ladbury, G. Koepke and H. Garbe, “Using Reverberation
Chamber to Simulate the Power Delay Profile of a Wireless Environment”, EMC Europe 2008,
Sept, 2008, Hamburg, Germany.
[4] H. Fielitz, K.A. Remley, C.L. Holloway, Q. Zhang, Q. Wu, and D. W. Matolak, “Reverberation-Chamber
Test Environment for Outdoor Urban Wireless Propagation Studies”, IEEE Antennas and Wireless
Propag. Lett., 2009.
[5] K.A. Remley, H. Fielitz, and C.L. Holloway, Q. Zhang, Q. Wu, and D. W. Matolak, “Simulation of a MIMO
system in a reverberation chamber”, IEEE EMC Symp. August 2011
[6] K.A. Remley, S.J. Floris, and C.L. Holloway, “Static and Dynamic Propagation-Channel Impairments in
Reverberation Chambers,” submitted to IEEE Transactions on EMC, 2010.
[7] D. Hill, “Electromagnetic Fields in Cavities: Deterministic and Statistical Theories” , IEEE Press, Copyright
© 2009.
Other References on Wireless Measurements
in Reverberation Chambers [8] C. Wright, S. Basuki, "Utilizing a channel emulator with a reverberation chamber to create the optimal
MIMO OTA test methodology," Mobile Congress (GMC), 2010 Global , vol., no., pp.1-5, 18-19
Oct. 2010.
[9] N. Serafimov, P.-S. Kildal, and T. Bolin, “Comparison between radiation efficiencies of phone antennas and
radiated power of mobile phones measured in anechoic chambers and reverberation chambers,”
in Proc. IEEE Antennas Propag. Int. Symp. 2002, Jun. 2002, vol. 2, pp.478–481.
[10] P.-S. Kildal, K. Rosengren, J. Byun, and J. Lee, “Definition of effective diversity gain and how to measure
it in a reverberation chamber,” Microwave Opt. Technol. Lett., vol. 34, no. 1, pp. 56–59, Jul. 2002.
[11] K. Rosengren and P.-S. Kildal, “Radiation efficiency, correlation, diversity gain, and capacity of a six
monopole antenna array for a MIMO system: Theory, simulation and measurement in reverberation
chamber,” Proc. Inst. Elect. Eng. Microwave, Antennas, Propag., vol. 152, no. 1, pp. 7–16, Feb.
2005.
[12] M. Lienard and P. Degauque, “Simulation of dual array multipath channels using mode-stirred
reverberation chambers,” Electron. Lett., vol. 40, no. 10, pp. 578–5790, May 2004.
[13] P.-S. Kildal and K. Rosengren, “Electromagnetic analysis of effective and apparent diversity gain of two
parallel dipoles,” IEEE Antennas Wireless Propag. Lett., vol. 2, pp. 9–13, 2003.