December 2012 

NASA/TM-2012-

Analysis of the Radiated Field in an 

Electromagnetic Reverberation Chamber as an 

Upset-Inducing Stimulus for Digital Systems 

Wilfredo Torres-Pomales 

Langley Research Center, Hampton, Virginia 
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December 2012 

NASA/TM-2012-

Analysis of the Radiated Field in an 

Electromagnetic Reverberation Chamber as an 

Upset-Inducing Stimulus for Digital Systems 

Wilfredo Torres-Pomales 

Langley Research Center, Hampton, Virginia 
Available from: 

NASA Center for AeroSpace Information 

7115 Standard Drive 

Hanover, MD 21076-1320 

443-757-5802 

Acknowledgement 

The author is grateful for the contributions to the work described here by the following 

individuals: Sandra V. Koppen, Truong X. Nguyen, Jay J. Ely, John J. Mielnik, Jr, and 

Daniel M. Koppen. 
iii

Abstract 

Preliminary data analysis for a physical fault injection 

experiment of a digital system exposed to High Intensity 

Radiated Fields (HIRF) in an electromagnetic reverberation 

chamber suggests a direct causal relation between the time 

profile of the field strength amplitude in the chamber and the 

severity of observed effects at the outputs of the radiated system. 

This report presents an analysis of the field strength modulation 

induced by the movement of the field stirrers in the reverberation 

chamber. The analysis is framed as a characterization of the 

discrete features of the field strength waveform responsible for 

the faults experienced by a radiated digital system. The results 

presented here will serve as a basis to refine the approach for a 

detailed analysis of HIRF-induced upsets observed during the 

radiation experiment. This work offers a novel perspective into 

the use of an electromagnetic reverberation chamber to generate 

upset-inducing stimili for the study of fault effects in digital 

systems. 
iv

Table of Contents 

Abbreviations ..................................................................................................................................................v

1. Introduction ................................................................................................................................................ 1

2. Stirrer-Induced Modulation Test ................................................................................................................ 4

3. Insight into the Error Generation Mechanism in a HIRF Environment...................................................... 6

4. Approach to the Analysis of Stirrer-Induced Modulation ........................................................................ 11

5. Results and Analysis................................................................................................................................. 11

5.1. Stirrer-Induced Modulation Waveforms............................................................................................ 11

5.1.1. Periodicity................................................................................................................................... 12

5.1.2. Effect of stirrer angular offset..................................................................................................... 13

5.1.3. Effect of frequency ..................................................................................................................... 13

5.2. Overstrokes........................................................................................................................................ 14

5.2.1. Population Spread....................................................................................................................... 15

5.2.2. Statistics of Overstroke Features for the Range of Test Frequencies ......................................... 20

5.2.2.1. Peak amplitude multiplied by duration................................................................................ 20

5.2.2.2. Peak Amplitude Divided by Duration ................................................................................. 22

5.2.2.3. Peak Amplitude ................................................................................................................... 24

5.2.2.4. Duration............................................................................................................................... 26

5.2.3. Statistics of Overstroke Features for the Range of Reference Levels......................................... 28

5.2.3.1. Peak Amplitude ................................................................................................................... 28

5.2.3.2. Duration............................................................................................................................... 30

5.2.4. Variability of Statistics with Respect to Relative Stirrer Angular Offset ................................... 32

5.2.4.1. Variability Across the Frequency Range ............................................................................. 32

5.2.4.2. Variability Across the Reference-Level Range ................................................................... 36

5.3. Agregated Overstrokes for Mean HSTC Node Susceptibility Threshold Profile .............................. 39

5.3.1. Population Spread....................................................................................................................... 41

5.3.2. Statistics of Overstroke Features for the Range of HEC Nominal Overstrengths ...................... 43

5.3.2.1. Peak Amplitude Multiplied by Duration.............................................................................. 43

5.3.2.2. Peak Amplitude Divided by Duration ................................................................................. 43

5.3.2.3. Peak Amplitude ................................................................................................................... 44

5.3.2.4. Duration............................................................................................................................... 44

6. Final Remarks........................................................................................................................................... 46

Appendix A. Stirrer-Induced Modulation Waveforms ................................................................................. 47

Appendix B. Overstroke Population at Test Frequencies............................................................................. 54

References .................................................................................................................................................... 68
v

Abbreviations 

AC Alternating Current 

ASIC Application Specific Integrated Circuit 

ASCII American Standard Code for Information Interchange 

BIU Bus Interface Unit 

CCP Controller Coordination Protocol 

COTS Commercial Off-The-Shelf 

CPU Central Processing Unit 

CW Continuous Wave 

DC Direct Current 

DUT Device Under Test 

EM Electromagnetic 

EMI Electromagnetic Interference 

Et Overstroke Reference Level 

FHSTC Fine HIRF Susceptibility Threshold Characterization 

FPGA Field Programmable Gate Array 

FSM Finite State Machine 

GPIB General Purpose Instrumentation Bus 

HC Hardware Configuration 

HEC HIRF Effects Characterization 

HFA Hub Fault Analyzer 

HIRF High Intensity Radiated Field 

HSTC HIRF Susceptibility Threshold Characterization

IMA Integrated Modular Architecture 

IVHM Integrated Vehicle Health Management 

LUF Lowest Usable Frequency 

Mbps Mega-bits per second 

MHz Megahertz 

ms Millisecond 

NFA Node Fault Analyzer 

NIST National Institute of Standards and Technology

OS Overstroke 

PE Processing Element 

RC Reverberation Chamber 

RF Radio Frequency 

RMS Root Mean Square 

RMU Redundancy Management Unit 

ROBUS Robust Bus 

RPP ROBUS Protocol Processor 

RSPP Reconfigurable SPIDER Prototyping Platform 

RTCA Radio Technical Commission for Aeronautics 

SD Standard Deviation 

SHM System Health Monitor 

SIM Stirrer Induced Modulation 

SPIDER Scalable Processor-Independent Design for Extended Reliability 

SUT System Under Test 

TCS Test Control System 

TDMA Time Division Multiple Access 

VHDL VHSIC Hardware Description Language 

VHSIC Very High Speed Integrated Circuit 

V/m Volts per meter 

 
1

1. Introduction 

A physical fault injection experiment was conducted in which a prototype implementation of an 

onboard data network for safety-critical, real-time Integrated Modular Architectures (IMA) was exposed

to a High Intensity Radiated Field (HIRF) environment in a mode-stirred electromagnetic reverberation 

chamber. The purpose of the experiment was to gain insight into the response of the system to a wide 

range of internal faults, including conditions that exceed the design safety margins [1, 2, 3]. There is 

special interest in examining the response to functional upsets, which are error modes that involve no 

permanent component damage, can simultaneously occur in multiple channels of a redundant distributed 

system and can cause unrecoverable distributed state error conditions [4, 5, 6]. 

The fault injection experiment was divided in two parts. The HIRF Susceptibility Threshold 

Characterization (HSTC) experiment was intended to identify and examine factors that determine the 

measured minimum HIRF field strength level at which a particular electronic System Under Test (SUT) 

begins to experience HIRF-induced interference to its internal operation (i.e., faults). The results and 

lessons learned in the execution of the HSTC experiment are described in report [3]. The HIRF Effects

Characterization (HEC) experiment was intended to assess the SUT’s response to functional system 

upsets. The analysis of the HEC data is ongoing. 

The experiment was conducted at the NASA Langley Research Center’s HIRF Laboratory using 

Reverberation Chamber A of the facility to generate the HIRF environment [1, 7]. Similar to a large 

microwave oven, a reverberation chamber operates as a cavity resonator in which the electromagnetic 

field generated by a transmitting antenna reflects off the metal walls forming complex three-dimensional 

electromagnetic field patterns with low energy loss. Rotating mechanical stirrers in the chamber with

electrically conductive paddle surfaces spread the spatial energy distribution by changing the field 

structures, effectively producing a statistically uniform and isotropic electromagnetic environment. The 

diagram in Figure 1 shows the layout inside the chamber. The photos in Figures 2 and 3 show the inside 

of the chamber with the positions where SUTs could be placed on non-conductive foam blocks or tables. 

When the HSTC experiment was initially designed, we thought that the amplitude profile of the field 

experienced by an SUT in the chamber would be determined mainly by the signal driving the transmitting

antenna. For example, it was expected that a constant amplitude input signal would result in constant

amplitude radiation. However, during the experiment it was observed that the field strength amplitude

was actually time varying even when the input to the chamber was an unmodulated constant wave (CW) 

signal. Figure 4 shows an oscilloscope trace of the field strength amplitude during a radiation burst

measured at the output of a field-monitoring antenna in the chamber. The duration of the burst was 

determined by the input signal, which was a pulse of CW with duration much larger than the chamber 

time constant [1, 7, 8]. This means that the time varying field strength amplitude of the radiation burst is 

not due to transient effects in the chamber when the input pulse is applied because the duration of the 

pulse is much larger than the time required for the field strength to reach steady state. Instead, the 

observed time varying field strength amplitude is presumed to be due to changes in the boundary 

conditions in the chamber (i.e., the spatial positioning of electromagnetically reflective surfaces) as the 

stirrers rotate. In Figure 4 it can be seen that this Stirrer-Induced Modulation (SIM) has a strong 

influence on the field strength amplitude inside in the chamber. Based on this, we believe that the SIM is 

also a critical factor in the characteristics of physical faults generated by the HIRF environment and, 

consequently, on the observed system responses in the HEC experiment. This is the motivation for the 

stirrer induced modulation test and analysis presented in this report. 
2

Figure 1: Basic layout of reverberation chamber A for a HIRF experiment 

Figure 2: Photo of Reverberation Chamber A taken from the back of the chamber (Also shows SUT test articles 

placed on foam blocks and tables.) 

Test Articles 

Stirrer 

Stirrer 

Receive 

Antenna

Transmit 

Antenna 

Chamber A 

Front Door 

Side Door 
3

 Figure 3: Photo of Reverberation Chamber A taken from the front of the chamber 

Figure 4: Oscilloscope trace of the field strength amplitude during a radiation pulse measured at the output of a 

field-monitoring antenna in the reverberation chamber 
4

The purpose of the analysis presented here is to understand the relation between the radiated 

electromagnetic field in the reverberation chamber and the faults experienced by SUTs. We expect the 

results to be a critical component in the analysis of the HEC experiment data. We intend to leverage the 

relation described in Section 3 between the field strength characteristics and the error bursts at the output 

of a radiated digital device. That relation will be the basis for a high-level functional (i.e., black box) 

stimulus-response analysis to assess the severity of the effects caused by the HIRF environment on the

radiated digital devices and to rank the devices based on the relative resilience to the environment. This 

will be followed by detailed analyses of upset events to identify the low-level physical components 

directly affected by the HIRF environment and the error propagation paths from the faulty components to 

the outputs of the radiated devices and on to the outputs of the prototype onboard data network. This will 

then be used to identify error containment and recovery weaknesses in the network and propose ways to 

strengthen the design. That work is ongoing and will be the presented in future reports [11]. 

The content of the report is as follows. The next section describes the test performed in Chamber A of 

the HIRF Lab to gather SIM data suitable for a meaningful characterization. This is followed by a 

description of a useful insight about the error generation process in the HIRF environment learned during 

preliminary analysis of the HEC data. This insight is applied in the definition of the approach to analyze 

the stirrer-induced modulation. The data analysis results are presented after that. The report concludes 

with final remarks about what has been accomplished and describes how results presented here will be 

used in the analysis of the HEC experiment data. The appendices present a subset of the SIM waveforms

measured during the test, as well as additional plots of SIM features not included in the main body of the 

report. 

2. Stirrer-Induced Modulation Test 

A test was carried out using Chamber A of the HIRF Lab to gather data suitable for a characterization 

of the SIM waveforms in the chamber. Figure 5 illustrates the test setup. A computer, labeled Test 

Controller in Figure 5, was programmed to control the chamber using a GPIB bus to interact with the 

instrumentation. A signal generator drove a power amplifier which produced the input signal to the 

transmit antenna in the chamber. Only CW signals were used in this test to provide a constant input 

power while the stirrers were rotating. The calibration procedure described in report [1], Section 4, was 

used to determine the input power to the chamber. The stirrers were driven by motors set to rotate at 5.0 

seconds per revolution. The field in the chamber was measured with a receive antenna connected to a 

spectrum analyzer. The collected data consisted of field strength measurement traces, each composed of 

800 sample points uniformly spaced over a time interval of 5.05 seconds to ensure full coverage of a 

stirrer revolution. At each test frequency, 11 field strength traces were collected with a period of 

approximately 30 seconds timed by the Test Controller. The variable “revolution” is used to refer to the 

field-strength traces and the relative time at the beginning of a trace identifies individual revolutions: 0 

sec, 30 sec, etc. Table 1 lists the 14 test frequencies selected for this test. These frequencies were a 

subset of the ones used in the HSTC experiment and included only those for which HIRF susceptibility 

was observed at no higher than 300 V/m calibrated field strength [1, 3]. The rotational angular offset of 

the stirrers, illustrated in Figure 6, was changed in 45-degree increments from 0 to 315 degrees for a total 

of 8 test values. Overall, 1232 traces were collected (= 8 angular offsets x 14 test frequencies x 11

revolutions). Figure 7 shows a field strength trace at 110.07 MHz with a 45-degree stirrer angular offset. 
5

Table 1: Test frequencies for the Stirrer-Induced Modulation Test 

Test Frequency (MHz) Test Frequency (MHz)

100.00 195.73 

110.07 316.23 

121.15 383.12 

133.35 421.70 

146.78 510.90 

161.56 562.34 

177.83 908.52 

Figure 5: Setup for stirrer induced modulation test using Chamber A 

output Directional input 

Coupler

50 Ohms 

Load

RF 

Sig Gen 

Power Meter

Spectrum 

Analyzer 

Motor 

Controller

Power 

Amp 

forward Test Articles 

Directional 

Coupler 

Power 

Sensor 

Control Room(E) 

Stirrer 

Stirrer 

Receive

Ant.

Xmit 

Ant. 

1a 

1b 

1c 

1d 

1e 

2a 

2b

6a 6b 6c 

4a 

8a 

8b 

7c 7b 7a 

3a

3b

5a 

5b 

GPIB

GPIB 

GPIB 

GPIB 

GPIB

GPIB 

Chamber A 

Control Room(E) Amplifier Room(D) 

Test Controller 
6

Figure 6: Illustration of the relative rotational angular offset for field stirrers rotating at the same speed 

Figure 7: Sample field strength trace at 110.07 MHz and 45-degree stirrer angular offset 

3. Insight into the Error Generation Mechanism in a HIRF Environment 

In the HEC experiment, the SUTs were exposed to a series of 5-second radiation bursts at nominal 

calibrated peak field strengths of 0, 10 and 20 V/m above the susceptibility threshold of the SUT at each 

test frequency. A radiation burst is called a strike, a series of strikes is called a round, and the field 

strength above the susceptibility threshold of an SUT is called the over-strength of the radiation. The 

field stirrers were set to rotate at a rate of 5 seconds per revolution such that for each strike an SUT was 

exposed to the time varying field strength pattern induced by the stirrers in one full revolution. 

The plots in Figures 8 to 10 were generated during a preliminary analysis of the response of an SUT in

the HEC experiment. These plots show the output error rate of the SUT (i.e., number of output errors per 

time unit) during radiation strikes with nominal over-strengths of 0, 10, and 20 V/m. Each error rate

surge delimited by error-free intervals is called an error burst. Notice that the error bursts increase in 

amplitude and duration as the over-strength increases, but their relative positions in time remain constant. 

In addition, a higher over-strength generates more error bursts. Another interesting feature seen on the 

three largest error bursts in Figure 10 is the saturation in the error rate, which indicates that the SUT was 

completely overwhelmed by the HIRF environment. 

Relative Angular Offset 

Stirrer 1 Stirrer 2 

Reference 

Reference paddle 

paddle 

0.00

20.00

40.00

60.00

80.00

100.00

120.00

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Field Strength (V/m)
7

Figure 8: Output error rate of an SUT at 0 V/m nominal over-strength 

Figure 9: Output error rate of an SUT at 10 V/m nominal over-strength 

Error Rate During a Radiation Strike

Frequency: 121.15 MHz; Overstrength: 10 V/m

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

14.0014.1014.2014.3014.4014.5014.6014.7014.8014.9015.0015.1015.2015.3015.4015.5015.6015.7015.8015.9016.0016.1016.2016.3016.4016.5016.6016.7016.8016.9017.0017.1017.2017.3017.4017.5017.6017.7017.8017.9018.0018.1018.2018.3018.4018.5018.6018.7018.8018.9019.00

Time (sec)

Error Rate

Error bursts

Error Rate During a Radiation Strike

Frequency: 121.15 MHz; Overstrength: 0 V/m

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

12.0012.1012.2012.3012.4012.5012.6012.7012.8012.9013.0013.1013.2013.3013.4013.5013.6013.7013.8013.9014.0014.1014.2014.3014.4014.5014.6014.7014.8014.9015.0015.1015.2015.3015.4015.5015.6015.7015.8015.9016.0016.1016.2016.3016.4016.5016.6016.7016.8016.9017.00

Time (sec)

Error Rate

Error bursts
8

Figure 10: Output error rate of an SUT at 20 V/m nominal over-strength 

Now consider the field strength trace shown in Figure 11, which was generated with a constantamplitude CW input signal to the reverberation chamber. (Note that the trace in Figure 11 was taken with 

no SUTs in the chamber, and in particular, the field strength measured in Figure 11 was not the field 

strength at the time the error-rate data in Figure 8 to 10 was taken.) The amplitude of the trace in Figure 

11 has been normalized as we are interested in the shape of the waveform rather than its actual amplitude. 

A higher power CW input signal should simply cause an increase in the amplitude of the waveform, but 

the shape of the waveform should remain unchanged. The HIRF susceptibility threshold of an SUT at a 

particular test frequency is the minimum field strength at which the HIRF environment interferes with the 

operation of the SUT. In general, it is expected that as long as the field strength experienced by an SUT 

is greater than the susceptibility threshold, the operation of the SUT will be impaired. Therefore, for 

example, if an SUT were exposed to a field strength with the profile in Figure 11 and the susceptibility 

threshold of the SUT were at the level indicated by the red line, we would expect the SUT to malfunction 

at least for the duration of each of the two field strength excursions above the threshold. These 

excursions of the field strength above the susceptibility threshold are called overstrokes. Figures 12 to 

14 show the overstrokes for the waveform in Figure 11 with susceptibility threshold levels of 0.85, 0.75, 

and 0.65, respectively. A reduction of the susceptibility threshold level (also called the overstroke

reference level) on an amplitude-normalized trace corresponds to an increase in the peak field strength in 

the non-normalized waveform. Notice that the amplitude and duration of the overstrokes, as well as the 

number of overstrokes, all increase as the reference level decreases (i.e., as the field strength increases). 

Also, notice that the relative position of the overstrokes is unchanged as the reference level decreases. 

Comparing Figures 8 to 10 with Figures 12 to 14, we notice similar trends for error-rate bursts and 

overstrokes as the over-strength increases: the amplitude and duration of the bursts and overstrokes 

increase, and the number of bursts and overstrokes also increase. Based on this, we conjecture that error 

bursts are caused by overstrokes and that the amplitude of an error-rate burst is directly related to the 

amplitude of the overstroke experienced by the SUT.

This insight into the error generation process in the HIRF environment will be leveraged in the 

definition of the approach to analyze the stirrer-induced modulation traces. 

Error Rate During a Radiation Strike

Frequency: 121.15 MHz; Overstrength: 20 V/m

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

14.0014.1014.2014.3014.4014.5014.6014.7014.8014.9015.0015.1015.2015.3015.4015.5015.6015.7015.8015.9016.0016.1016.2016.3016.4016.5016.6016.7016.8016.9017.0017.1017.2017.3017.4017.5017.6017.7017.8017.9018.0018.1018.2018.3018.4018.5018.6018.7018.8018.9019.00

Time (sec)

Error Rate
9

Figure 11: Amplitude-normalized field strength trace 

Figure 12: SIM overstrokes at reference level 0.85 

Stirrer-Induced Modulation Overstrokes

Frequency: 121.15 MHz; Reference Level: 0.85

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

200.00200.10200.20200.30200.40200.50200.60200.70200.80200.90201.00201.10201.20201.30201.40201.50201.60201.70201.80201.90202.00202.10202.20202.30202.40202.50202.60202.70202.80202.90203.00203.10203.20203.30203.40203.50203.60203.70203.80203.90204.00204.10204.20204.30204.40204.50204.60204.70204.80204.90205.00

Time (sec)

Overstroke Amplitude

Normalized Field Strength Trace

Frequency: 121.15 MHz

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

1.10

0.000.130.250.380.510.630.760.881.011.141.261.391.521.641.771.892.022.152.272.402.532.652.782.903.033.163.283.413.543.663.793.914.044.174.294.424.554.674.804.92

Stirrer Position (sec)

Normalized Field Strength

Merge level (see Section 5.2.1) 

Overstrokes Susceptibility Threshold Level = 0.85 
10

Figure 13: SIM overstrokes at reference level 0.75 

Figure 14: SIM overstrokes at reference level 0.65 

Stirrer-Induced Modulation Ovestrokes

Frequency: 121.15 MHz; Reference Level: 0.75

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

200.00200.10200.20200.30200.40200.50200.60200.70200.80200.90201.00201.10201.20201.30201.40201.50201.60201.70201.80201.90202.00202.10202.20202.30202.40202.50202.60202.70202.80202.90203.00203.10203.20203.30203.40203.50203.60203.70203.80203.90204.00204.10204.20204.30204.40204.50204.60204.70204.80204.90205.00

Time (sec)

Overstroke Amplitude

Stirrer-Induced Modulation Overstrokes

Frequency: 121.15 MHz; Reference Level: 0.65

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

200.00200.10200.20200.30200.40200.50200.60200.70200.80200.90201.00201.10201.20201.30201.40201.50201.60201.70201.80201.90202.00202.10202.20202.30202.40202.50202.60202.70202.80202.90203.00203.10203.20203.30203.40203.50203.60203.70203.80203.90204.00204.10204.20204.30204.40204.50204.60204.70204.80204.90205.00

Time (sec)

Overstroke Amplitude
11

4. Approach to the Analysis of Stirrer-Induced Modulation 

The purpose of the SIM data analysis is not to describe this electromagnetic phenomenon per se. The 

SIM characterization is valuable only to the extent that it enables a meaningful analysis of observed HIRF 

effects in the HEC experiment. Given our insight into how the HIRF environment causes error bursts in

the SUTs, the SIM characterization should be viewed as an upset stimulus characterization. The existing 

detailed knowledge of the internal operation of the SUTs [2, 9, 10] should make it possible to identify 

causal relations between internal faults and observed responses at the interface. The SIM characterization 

will enable the study of complete sequences of events in the HEC experiment beginning with the applied

external stimulus of HIRF overstrokes that cause faults in an SUT, which then propagate internally 

through the SUT until reaching the external interface and produce the observed responses. 

The first part of the SIM characterization consists of a qualitative examination of SIM waveform 

features relative to the test controlled variables of stirrer revolution, angular offset, and test carrier 

frequency. Here we are simply trying to gain a high-level understanding of the effects of the controlled 

variables on the shape of the SIM waveforms. 

The second part of the SIM characterization is a quantitative analysis of SIM overstrokes with respect

to the stirrer revolution, stirrer angular offset, test frequency and overstroke reference level. For

simplicity, only two basic size features of an overstroke are measured, peak amplitude (p) and duration 

(d), as these are related to the error rate and duration of faults in SUTs. A more detailed overstroke model 

may be developed in future work if needed for a proper analysis of observed HEC responses. We are also 

interested in the relation between peak and duration, for which we define two composite measures: peak

multiplied by duration (p•d) and peak divided by duration (p/d). For sets of overstrokes defined in terms 

of particular ranges of the controlled test variables, we use scatter plots and averages (i.e., mean, standard 

deviation and root-mean-squared) to study the spread and trends in distributions. We also analyze the

variability of these set metrics across the range of stirrer angular offsets in order to estimate a bound for 

the difference of stimulus applied to different SUTs in the HEC experiment, where the angular offset was 

neither specified in the plan nor controlled during the experiment. 

In addition, we study overstroke sets with reference level profiles based on the measured susceptibility 

thresholds from the HSTC experiment. These overstroke sets represent the effective HIRF environment 

as experienced by SUTs in the HEC experiment. 

5. Results and Analysis 

The following three subsections present the SIM characterization results. 

5.1. Stirrer-Induced Modulation Waveforms 

We first examine the SIM waveforms relative to the controlled test variables of stirrer revolution, 

stirrer rotational angular offset and carrier frequency. 
12

5.1.1. Periodicity 

Figure 15 shows field strength traces taken 150 seconds apart for a carrier frequency of 110.07 MHz 

and stirrer angular offset of 0 degrees. The waveforms follow no discernible patterns and appear to be 

completely different. They are continuous but have sharp transitions and large amplitude ranges of over 

100 V/m. Recall that both field stirrers in the reverberation chamber were set to rotate at 5.0 seconds per 

revolution. If the large field-strength amplitude variations in Figure 15 were caused by the rotation of the 

stirrers, we would expect the traces to be periodic with period equal to the time for the stirrers to complete 

one revolution (i.e., 5.0 seconds). To check this, a computer program was developed to “synchronize” the 

traces by finding the circularly shifted version of one of the traces that returned the minimum sum of

squared differences between the traces. Figure 16 shows the traces after synchronization. This shows

that the waveforms are actually nearly identical and supports the hypothesis that the field-strength 

waveform is periodic and caused by the rotation of the stirrers. 

Figure 15: Field strength traces at 110.07 MHz and 0-degree stirrer angular offset 

Figure 16: Synchronized field strength traces at 110.07 MHz and 0-degree stirrer angular offset 

As stated previously, we are interested in working with amplitude-normalized traces to focus the 

analysis on the shape of the waveforms regardless of their real amplitudes. To compare multiple traces 

we need to use a common normalizing amplitude value, but as seen in Figure 16, the peak amplitude of 

the field strength can vary slightly between periods. To handle this situation for a set of traces, we chose 

the median peak amplitude as the normalizing amplitude. The median was preferred over the mean 

because the median is not affected by extreme high or low values. 

Figure 17 shows the synchronized and amplitude-normalized field-strength traces for 110.07 MHz and 

0-degree stirrer angular offset. This figure shows that the stirrer-induced modulation remains stable in 

time, but there are slight amplitude differences that appear randomly and have variable duration. Given 

the strong evidence that the SIM waveform is caused by the rotation of the stirrers, it was suspected that 

the amplitude variations were due to irregular operation of the stirrers’ drive mechanism. Indeed, an

0.000

20.000

40.000

60.000

80.000

100.000

120.000

0.000.160.320.470.630.790.951.111.261.421.581.741.902.052.212.372.532.692.843.003.163.323.483.633.793.954.114.274.424.584.744.90

Stirrer Position (seconds)

Field Strength (V/m)

0 sec

150 sec

0.00

20.00

40.00

60.00

80.00

100.00

120.00

0.000.160.320.470.630.790.951.111.261.421.581.741.902.052.212.372.532.692.843.003.163.323.483.633.793.954.114.274.424.584.744.90

Stirrer Position (seconds)

Field Strength (V/m)

0 sec

150 sec
13

inspection revealed that parts of the mechanism had degraded from normal wear after years of service. It 

is believed that the worn parts were increasing the friction in the drive mechanism, which caused random 

variations in the rotational speed of the stirrers. Replacement of the worn parts improved the operation of 

the stirrers. An unexpected outcome of this analysis is the realization that the SIM waveform could be 

used as an indirect means of checking the operating status of the stirrers. 

Figure 17: Normalized and synchronized field strength traces at 110.07 MHz and 0-degree stirrer angular offset 

5.1.2. Effect of stirrer angular offset 

Figure 18 shows SIM traces for various stirrer angular offsets at 110.07 MHz. These waveforms are 

different from each other and cannot be synchronized as described above. This is true in general: a 

change in the stirrer angular offset changes the SIM waveform. However, a closer examination of the 

waveform features, like the shape, number and time distribution of the peaks and valleys, suggests that 

the waveforms are the result of a common generation process that imposes local constrains on the shapes 

of the features but allows the waveforms to have an arbitrary global pattern, albeit constrained to be

periodic due to the rotation of the stirrers. It is believed that this behavior is an effect of the spatial field 

patterns determined by the frequency-dependent resonance modes in the reverberation chamber. With 

respect to the generation of faults in radiated systems, it is of interest to bound the differences in the fault 

sets experienced by systems tested with different stirrer angular offsets as this was not a controlled

variable in the HEC experiment. This is addressed in a later section covering the analysis of SIM 

overstrokes. 

5.1.3. Effect of frequency 

Figure 19 shows example SIM traces for test frequencies at 110.07, 316.23 and 908.52 MHz. The 

trend as the frequency increases is that the waveforms have faster transitions, the peaks have shorter

duration and there are more peaks and valleys per trace. This is consistent with a decrease in the 

wavelength of the radiation at higher frequency, where the chamber accommodates a larger number of 

resonance modes [7]. 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.000.160.320.470.630.790.951.111.261.421.581.741.902.052.212.372.532.692.843.003.163.323.483.633.793.954.114.274.424.584.744.90

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.000.160.320.470.630.790.951.111.261.421.581.741.902.052.212.372.532.692.843.003.163.323.483.633.793.954.114.274.424.584.744.90

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec
14

Figure 18: SIM traces for different stirrer angular offsets at 110.07 MHz 

5.2. Overstrokes 

In this section, we perform a quantitative examination of the SIM traces using the overstroke concept. 

The analysis centers on the relation between the independent controlled variables and the features of the 

generated overstrokes. The test-controlled variables are the frequency, stirrer angular offset and stirrer 

revolution, with the chamber input power set to achieve a desired electric field strength level (see [1] 

Section 4.3). For the analysis presented here, the overstroke reference level is another independently 

controlled variable. The basic overstroke features of interest include the peak (i.e., maximum) amplitude 

(p) and duration (d). We are also interested in the relation between the peak amplitude and the duration, 

and for this, we define the two additional overstroke metrics of peak multiplied by duration (p•d) and 

peak divided by duration (p/d). 

The population of overstrokes derived from the set of available SIM traces can be subdivided based on 

the values of the controlled variables. In the first part of the analysis in Sections 5.2.2 and 5.2.3, we 

divide the overstroke set only by frequency and overstroke reference level, and aggregate the overstrokes 

over the ranges of stirrer angular offset and revolution. Later in Section 5.2.4, we examine the effect of 

the stirrer angular offset with overstroke aggregation only for the stirrer revolution variable. 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.000.160.320.470.630.790.951.111.261.421.581.741.902.052.212.372.532.692.843.003.163.323.483.633.793.954.114.274.424.584.744.90

Normalized Field Strength 0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.000.160.320.470.630.790.951.111.261.421.581.741.902.052.212.372.532.692.843.003.163.323.483.633.793.954.114.274.424.584.744.90

Normalized Field Strength

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.000.160.320.470.630.790.951.111.261.421.581.741.902.052.212.372.532.692.843.003.163.323.483.633.793.954.114.274.424.584.744.90

Stirrer Position (seconds)

Normalized Field Strength
15

Figure 19: Examples of SIM traces for different test carrier frequencies 

5.2.1. Population Spread 

Figure 20 shows how the number of overstrokes at various frequencies varies as the reference level 

decreases. The overstrokes were generated for amplitude-normalized but unsynchronized field-strength 

traces. As expected from inspection of Figure 19, at each frequency the trend is that the number of 

overstrokes increases as the reference level decreases. Interestingly, the number of overstrokes at a

particular reference level is not always larger for higher frequencies. In particular, notice how at 908.52 

MHz the rate of increase in the overstroke count starts slow and grows very quickly as the reference level 

decreases. Given that this data is for aggregated sets over the stirrer angular offsets and revolutions, it 

appears that the SIM profile in Figure 19 for 908.52 MHz is generally valid at this frequency. That is, at 

908.52 MHz, there are very few SIM waveform peaks approaching the maximum normalizing amplitude 

and almost all of the peaks have amplitude lower than 60% of the maximum. Another way of looking at 

the trend in Figure 20 is that, as the reference level decreases, it is more likely (i.e., there are fewer 

exceptions to the pattern) that the number of overstrokes is larger at higher frequencies. 

Frequency: 110.07 MHz

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.000.160.320.470.630.790.951.111.261.421.581.741.902.052.212.372.532.692.843.003.163.323.483.633.793.954.114.274.424.584.744.90

Stirrer Position (seconds)

Normalized Field Strength

Frequency: 316.23 MHz

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.000.160.320.470.630.790.951.111.261.421.581.741.902.052.212.372.532.692.843.003.163.323.483.633.793.954.114.274.424.584.744.90

Stirrer Position (seconds)

Normalized Field Strength

Frequency: 908.52 MHz

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.000.160.320.470.630.790.951.111.261.421.581.741.902.052.212.372.532.692.843.003.163.323.483.633.793.954.114.274.424.584.744.90

Stirrer Position (seconds)

Normalized Field Strength
16

Figure 20: Number of overstrokes as the reference level decreases for various test frequencies 

Figures 21 to 23 show scatter plots of the overstroke populations for 110.07, 316.23, and 908.52 MHz 

at reference levels of 0.90, 0.75, and 0.60. The clustering effect of some points, especially at 110.07 

MHz, is probably due in part on the periodicity of SIM traces with the same frequency and angular offset 

but different stirrer revolutions. In Figure 21 at reference level 0.60, the overstrokes with duration 

between 700 and 800 ms are probably the result of the merging of overstrokes when the reference level 

drops below the lowest value of the gap separating them. This can be visualized, for example, by 

considering the overstrokes in Figure 11 at around 1.14 seconds if the reference level (indicated by the red 

reference line) drops below 0.50, at which point the overstrokes on either side of the gap become a single 

overstroke of large duration. 

From Figure 20, we know that, in general, at a particular reference level there are more overstrokes at 

higher frequency. However, from Figures 21 to 23 we see that at lower frequencies the features of the

overstrokes vary much more than at higher frequencies. For example, at reference level 0.60, the 

overstrokes with 0.2 peak amplitude vary in duration over a duration interval of about 600 ms at 110.07 

MHz, 100 ms at 316.23 MHz, and 70 ms at 908.52 MHz. 

Also, notice in Figures 22 and 23 that each frequency appears to impose a constraint on the maximum 

ratio of overstroke peak to duration as indicated by the crowding of points along a boundary line on the 

left hand side of the populated areas. This apparent peak-to-duration ratio constraint is larger at higher 

frequencies, which means that the overstrokes can have a more acute (i.e., pointy) profile. This trend can 

also be inferred from examination of the SIM traces in Figure 19. 

The significance of these scatter plots is that, based on the conjectured relation between overstrokes

and error bursts experienced by an SUT as described in Section 3, each point in Figures 21 to 23 

corresponds to a possible error burst that could be injected by the reverberation chamber into a radiated 

SUT. 

Number of Overstrokes

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0.90 0.75 0.60 0.50

Reference Level

Count

110.07 MHz

177.83 MHz

316.23 MHz

421.70 MHz

562.34 MHz

908.52 MHz
17

Figure 21: Scatter plots of overstroke peak amplitude versus duration at 110.07 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
18

Figure 22: Scatter plots of overstroke peak amplitude versus duration at 316.23 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
19

Figure 23: Scatter plots of overstroke peak amplitude versus duration at 908.52 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
20

5.2.2. Statistics of Overstroke Features for the Range of Test Frequencies 

We next examine separately the overstroke features of peak multiplied by duration, peak divided by 

duration, peak, and duration. In the following, the peak amplitude is normalized and the duration is 

measured in units of milliseconds. 

5.2.2.1. Peak amplitude multiplied by duration 

The metric of peak multiplied by duration (aka “peak times duration”) is related to the area of an 

overstroke. Figures 24 to 26 show the mean, standard deviation and root-mean-squared (RMS) values of 

the peak-times-duration overstroke metric for the full range of frequencies and overstroke reference levels 

(denoted Et) of 0.90, 0.75, and 0.60. Notice that the frequency axis is on an ordinal scale, not a linear or 

logarithmic scale. Also, note that the RMS is a compound statistical average that combines the mean and 

standard deviation. To see this, let Xrms, Xmean, and Xsd denote the RMS, mean and standard deviation of a 

value set, respectively. Then these statistical averages are related as follows: Xrms

2

 = Xmean

2

 + Xsd

2

. 

The overall trend in Figure 24 is that the mean area of the overstrokes decreases as the frequency 

increases. However, rather than decreasing monotonically, at every reference level the curves follow an 

undulating pattern by which the area can increase locally from one frequency to the next. We have no 

insight into the cause of this pattern, which is probably due to the resonance characteristics of the 

reverberation chamber. Interestingly, the standard deviation and, of course, the RMS value follow a 

similar trend across the frequency range. Also, notice that at every frequency, the magnitude of the 

standard deviation is similar to the mean, which implies that the spread of the distribution is to some 

extent proportional to its mean. 

Figure 24: Mean overstroke peak multiplied by duration for the range of test frequencies 

Mean of Overstroke Peak Amplitude Multiplied by Duration

0

10

20

30

40

50

60

70

80

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

OS Peak times Duration

Et = 0.90

Et = 0.75

Et = 0.60
21

Figure 25: Standard deviation of overstroke peak multiplied by duration for the range of test frequencies 

Figure 26: RMS overstroke peak multiplied by duration for the range of test frequencies 

Standard Deviation of Overstroke Peak Amplitude Multiplied by Duration

0

10

20

30

40

50

60

70

80

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

OS Peak times Duration

Et = 0.90

Et = 0.75

Et = 0.60

RMS of Overstroke Peak Amplitude Multiplied by Duration

0

10

20

30

40

50

60

70

80

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

OS Peak times Duration

Et = 0.90

Et = 0.75

Et = 0.60
22

5.2.2.2. Peak Amplitude Divided by Duration 

Figures 27 to 29 show the mean, standard deviation and RMS value of the overstroke peak amplitude 

divided by duration for the frequency range at selected reference levels. The peak-over-duration metric is 

related to the acuteness (i.e., pointiness) of the overstroke. Again, note that in these figures the values on 

the frequency axis are on an ordinal scale. Figure 27 shows that the acuteness of the overstrokes 

increases with the frequency, although locally from one frequency to the next the relation may be the 

opposite due to the resonance characteristics of the reverberation chamber. This global trend over the 

frequency range implies that the overstroke duration tends to decrease faster than the peak value. Also, 

notice in Figure 28 that the spread of the overstroke distribution with frequency is smaller than the mean 

value in Figure 29. This is interpreted to mean that the spread of the peak values grows larger with 

frequency than the spread of the durations. A comparison of Figures 27 and 28 shows that the spread of 

the peak-over-duration distribution is smaller than the mean by about one third, and in that sense, the 

spread is also smaller than for the peak-multiplied-by-duration distribution. The RMS curves in Figure 

29 are determined mostly by the mean values, as the standard deviation values are smaller. 

Figure 27: Mean overstroke peak divided by duration for the range of test frequencies 

Mean of Overstroke Peak Amplitude Divided by Duration

0

1

2

3

4

5

6

7

8

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

OS Peak over Duration (x1e3)

Et = 0.90

Et = 0.75

Et = 0.60
23

Figure 28: Standard deviation of overstroke peak divided by duration for the range of test frequencies

Figure 29: RMS overstroke peak divided by duration for the range of test frequencies 

Standard Deviation of Overstroke Peak Amplitude Divided by Duration

0

1

2

3

4

5

6

7

8

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

OS Peak over Duration (x1e3)

Et = 0.90

Et = 0.75

Et = 0.60

RMS of Overstroke Peak Amplitude Divided by Duration

0

1

2

3

4

5

6

7

8

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

OS Peak over Duration (x1e3)

Et = 0.90

Et = 0.75

Et = 0.60
24

5.2.2.3. Peak Amplitude 

The mean, standard deviation and RMS of the overstroke peak amplitude over the frequency range are 

shown in Figure 30 to 32. Overall, the averages of the overstroke peak do not change much across the 

frequency range for any reference level. The range of the mean value in Figure 30 varies from about 23% 

of the maximum at reference level 0.90 to about 34% at reference level 0.60. The general trends of the 

mean value are that it decreases with frequency and it grows faster at lower frequencies with decreasing 

reference level. As the nominal overstroke maximum peak value increases 4 times with the range of 0.1

to 0.4 over the reference level range of 0.9 to 0.6, the increase in the mean peak value is about 2.6 at 100 

MHz and about 2.0 at 908.52 MHz. This shows that, in general, the mean peak value grows faster at 

lower frequencies and about half as fast as the nominal maximum peak value as the reference level 

decreases. 

The standard deviation curves in Figure 31 show that the spread remains nearly constant over the 

frequency range, but it increases as the reference level decreases. The trends in the RMS curves in Figure 

32 are determined mainly by the mean value of the distribution. 

Figure 30: Mean overstroke peak across the test frequency range 

Mean of Overstroke Peak Amplitude Across Frequency Range

0

0.05

0.1

0.15

0.2

0.25

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

OS Peak Amplitude

Et = 0.90

Et = 0.75

Et = 0.60
25

Figure 31: Standard deviation of overstroke peak across the test frequency range 

Figure 32: RMS overstroke peak across the frequency range 

Standard Deviation of Overstroke Peak Amplitude Across Frequency Range

0

0.05

0.1

0.15

0.2

0.25

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

OS Peak Amplitude

Et = 0.90

Et = 0.75

Et = 0.60

RMS of Overstroke Peak Amplitude Across Frequency Range

0

0.05

0.1

0.15

0.2

0.25

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

OS Peak Amplitude

Et = 0.90

Et = 0.75

Et = 0.60
26

5.2.2.4. Duration 

Figures 33 to 35 show the mean, standard deviation and RMS values of the overstroke duration over 

the test frequency range for decreasing values of the reference level. For these figures, the frequency is 

given on a linear scale. Overall, the overstroke duration seems to decrease exponentially over the 

frequency range. The features in these figures can be divided into two frequency intervals: below 200

MHz and above 300 MHz. Below 200 MHz, the mean overstroke duration varies widely and decreases 

quickly from about 121.15 MHz onward. Above 300 MHz, the mean overstroke duration decreases much 

more slowly and appears to approach a minimum value asymptotically. Notice that the standard deviation 

decreases as the mean value decreases and it too seems to approach a minimum value at higher 

frequencies. We believe that this overstroke duration profile is directly related to the number of 

resonance modes generated in the reverberation chamber, with more modes being generated at higher 

frequencies, which results in more dynamic SIM waveforms. 

Figure 33: Mean overstroke duration over the frequency range on a linear scale 

Mean of Overstroke Duration Across Frequency Range

0

50

100

150

200

250

0 100 200 300 400 500 600 700 800 900 1000

Frequency (MHz)

OS Duration (ms)

Et = 0.90

Et = 0.75

Et = 0.60
27

Figure 34: Standard deviation of overstroke duration over the frequency range on a linear scale 

Figure 35: RMS overstroke duration over the frequency range on a linear scale 

Standard Deviation of Overstroke Duration Across Frequency Range

0

50

100

150

200

250

0 100 200 300 400 500 600 700 800 900 1000

Frequency (MHz)

OS Duration (ms)

Et = 0.90

Et = 0.75

Et = 0.60

RMS of Overstroke Duration Across Frequency Range

0

50

100

150

200

250

0 100 200 300 400 500 600 700 800 900 1000

Frequency (MHz)

OS Duration (ms)

Et = 0.90

Et = 0.75

Et = 0.60
28

5.2.3. Statistics of Overstroke Features for the Range of Reference Levels 

We next examine the statistical averages of the overstroke population for the features of peak 

amplitude and duration over a range of reference levels. 

5.2.3.1. Peak Amplitude 

Figures 36 to 38 show the mean, standard deviation and RMS values of the overstroke peak amplitude 

for reference levels in the range of 95% to 50% of the median maximum SIM amplitude. The curves are 

given only for three test frequencies, with 110.07 MHz representing the frequencies under 200 MHz, and

316.23 MHz and 908.52 MHz covering the much larger range above 300 MHz. We use Et to denote a 

particular reference level, with 0 ≤ Et ≤ 1. The maximum overstroke peak amplitude is equal to 1 - Et, 

and the maximum peak amplitude grows at a rate (i.e., slope) of approximately 1.0 over the decreasing 1-

to-0 range of Et. In Figure 36, the mean peak amplitude grows at a rate of approximately 0.43 at 110.07 

MHz and 0.23 at 908.52 MHz over the reference level range. At 95% reference level, the mean peak 

amplitude is about 86% of the maximum peak at 110.0 MHz and 908.52 MHz, but at 50% reference level, 

the mean is only about 48% of the maximum at 110.07 MHz and 29% at 908.52 MHz. This is consistent 

with the overstroke counts in Figure 20 in the sense that at higher frequencies and as the reference level 

decreases, many more overstrokes are generated with relatively small peak amplitudes, thus weighing 

down the overall mean value. 

Figure 37 shows that the standard deviation of the peak amplitude increase essentially linearly with the 

reference level, which means that the population spread is proportional to the mean value. The RMS 

value in Figure 38 is determined mainly by the mean value. 

Figure 36: Mean overstroke peak amplitude for the range of reference levels 

Mean of Overstroke Peak Amplitude Across Reference Level Range

0.00

0.05

0.10

0.15

0.20

0.25

0.30

95.0 90.0 85.0 80.0 75.0 70.0 65.0 60.0 55.0 50.0

OS Reference Level (%)

OS Peak Amplitude

110.07 MHz

316.23 MHz

908.52 MHz
29

Figure 37: Standard deviation of overstroke peak amplitude for the range of reference levels 

Figure 38: RMS overstroke peak amplitude for the range of reference levels 

Standard Deviation of Overstroke Peak Amplitude Across Reference Level Range

0.00

0.05

0.10

0.15

0.20

0.25

0.30

95.0 90.0 85.0 80.0 75.0 70.0 65.0 60.0 55.0 50.0

OS Reference Level (%)

OS Peak Amplitude

110.07 MHz

316.23 MHz

908.52 MHz

RMS of Overstroke Peak Amplitude Across Reference Level Range

0.00

0.05

0.10

0.15

0.20

0.25

0.30

95.0 90.0 85.0 80.0 75.0 70.0 65.0 60.0 55.0 50.0

OS Reference Level (%)

OS Peak Amplitude

110.07 MHz

316.23 MHz

908.52 MHz
30

5.2.3.2. Duration 

The mean, standard deviation and RMS overstroke duration for the range of reference levels are given 

in Figures 39 to 41. Figure 39 shows that the overstroke duration at low frequency is much more 

sensitive to the change in the reference level. The increases in the mean duration over the reference level 

range relative to the minimum durations at the 95% reference level are 2.58 times at 110.07 MHz, 1.17 at 

316.23 MHz, and 1.46 at 908.52 MHz. These measures of overstroke duration are consistent with the 

SIM traces in Figure 19 in that, near the top of the SIM peaks, the field amplitude changes with a slower 

time rate at lower frequencies, which increases the overstroke duration; as we travel down the SIM peaks, 

the field amplitude changes much more slowly at lower frequencies, which causes the duration to increase 

faster; and as the frequency increases, the amplitude rate of change seems to asymptotically approach a 

bound, which causes the duration versus reference level profile to be very similar at different high 

frequencies. 

As the reference level decreases, the standard deviations in Figure 40 increase not only in absolute 

value but also with respect to their corresponding mean values from 0.44 to 0.71 at 110.07 MHz, from 

0.40 to 0.72 to 316.23 MHz, and from 0.44 to 0.67 at 908.52 MHz. This indicates that the spread of 

overstroke duration increases faster than the mean as the reference level decreases. 

The RMS duration curves in Figure 41 follow the same trends as the curves for the mean and standard 

deviation values. 

Figure 39: Mean overstroke duration for the range of reference levels 

Mean of Overstroke Duration Across Reference Level Range

0

50

100

150

200

250

300

350

95.0 90.0 85.0 80.0 75.0 70.0 65.0 60.0 55.0 50.0

OS Reference Level (%)

OS Duration (ms)

110.07 MHz

316.23 MHz

908.52 MHz
31

Figure 40: Standard deviation of overstroke duration for the range of reference levels 

Figure 41: RMS overstroke duration for the range of reference levels 

Standard Deviation of Overstroke Duration Across Reference Level Range

0

50

100

150

200

250

300

350

95.0 90.0 85.0 80.0 75.0 70.0 65.0 60.0 55.0 50.0

OS Reference Level (%)

OS Duration (ms)

110.07 MHz

316.23 MHz

908.52 MHz

RMS of Overstroke Duration Across Reference Level Range

0

50

100

150

200

250

300

350

95.0 90.0 85.0 80.0 75.0 70.0 65.0 60.0 55.0 50.0

OS Reference Level (%)

OS Duration (ms)

110.07 MHz

316.23 MHz

908.52 MHz
32

5.2.4. Variability of Statistics with Respect to Relative Stirrer Angular Offset 

In the HEC experiment, the 5-second duration of the strikes was the same as the revolution period of 

the stirrers, and the strike period was 10 seconds (i.e., one 5-second strike was applied every 10 seconds). 

The timing of the strikes was independently controlled by a dedicated RF (Radio Frequency) signal 

generator, as illustrated in Figure 5. Due to the high timing accuracy of the signal generator and of the 

stirrer motor controller (which resulted in a near constant stirrer angular offset), the SIM waveforms were 

repeated identically for all the strikes in an HEC round. This means that for any two strikes in a round, 

the field strength traces were synchronized as shown in Figure 16, rather than unsynchronized as in 

Figure 15. Therefore, an SUT was exposed to approximately same set of overstrokes for each strike in a 

round. 

As the stirrer angular offset was not a controlled variable in the HEC experiments (other than being 

constant in each round), it is likely that, for a given physical location in the chamber, different SUTs were 

exposed to different overstroke sets even when tested at the same frequency and nominal over-strength 

level. Given the direct relation between the overstrokes and the error bursts as shown in Section 3, it is of 

interest to determine how much can the overstroke feature statistics vary for overstroke sets generated 

with different stirrer angular offsets. 

To evaluate this using the available SIM data, at each test frequency and stirrer angular offset, the SIM 

traces for the available stirrer revolutions were synchronized and the overstroke feature statistics were 

computed for the aggregate set of overstrokes at each reference level. We define the variation of a 

statistical average (i.e., mean, standard deviation or RMS value) of an overstroke feature as the difference 

between the maximum and minimum values across the range of stirrer angular offsets. For a given 

overstroke feature and statistical average, the variation is denoted by V and the maximum and minimum 

of the feature’s statistical average are denoted by Amax and Amin, respectively. Then V is given by: 

V = Amax - Amin (1) 

As shown in preceding sections, the statistics of the overstroke features are dependent on the 

frequency and reference level. To enable a meaningful comparison of variation across the ranges of 

frequency and reference levels, we define the variability of an overstroke feature’s statistical average 

across the range of stirrer angular offsets at a particular frequency and reference level as the ratio of the 

variation divided by the feature’s same statistical average for the overstroke set formed by aggregation 

over the range of stirrer angular offsets and revolutions with unsynchronized SIM traces. The overstroke 

aggregation conditions for this reference statistical average are the same used in the analysis in the

preceding sections. With Vn denoting variability and Aall denoting the total aggregate value, then: 

Vn = (Amax - Amin)/Aall (2) 

The following sections examine the variability of overstroke peak amplitude and duration across the 

ranges of frequency and reference level. 

5.2.4.1. Variability Across the Frequency Range 

Figures 42 to 44 show the variability of the mean, standard deviation and RMS peak amplitude for the 

range of test frequencies. Neither the mean nor the RMS statistical average has a clearly discernible trend 

with respect to either frequency or reference level. The variability curves for these averages follow

seemingly random patterns bounded between 0.2 and 1.2 for the mean and between 0.18 and 0.8 for the 

RMS. The variability curves for the standard deviation also seem essentially random, but there is an 
33

apparent trend by which the variability value and the bound interval of the variability decrease as the 

reference level decreases across the frequency range. We have no insight into this pattern of the standard 

deviation variability. 

Figure 42: Variability of mean overstroke peak amplitude for the range of test frequencies 

Figure 43: Variability of the standard deviation of overstroke peak amplitude for the range of test frequencies 

Variability of Mean Overstroke Peak Amplitude with Respect to Angular Offset 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

Variability of Mean Peak Amplitude

Et = 0.90

Et = 0.75

Et = 0.60

Variability of Std Deviation of Overstroke Peak Amplitude with Respect to Angular 

Offset 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

Variability of Std Deviation of Peak 

Amplitude

Et = 0.90

Et = 0.75

Et = 0.60
34

Figure 44: Variability of the RMS peak amplitude for the range of test frequencies 

The variability of the mean, standard deviation and RMS overstroke duration for the range of test 

frequencies are shown in Figures 45 to 47. None of the figures shows a clear trend of the variability with 

respect to the reference level. However, although there is a lot of variation across the frequency range, 

there seems to be a pattern of decreasing variability as the frequency increases for all the statistical 

averages. This patterns expands the trends observed previously, which show the duration to vary over an 

increasingly small range as the frequency increases. 

Figure 45: Variability of mean overstroke duration across the range of test frequencies 

Variability of RMS Overstroke Peak Amplitude with Respect to Angular Offset 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

Variability of RMS Peak Amplitude

Et = 0.90

Et = 0.75

Et = 0.60

Variability of Mean Overstroke Duration with Respect to Angular Offset 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

Variability of Mean Duration

Et = 0.90

Et = 0.75

Et = 0.60
35

Figure 46: Variability of the standard deviation of overstroke duration across the range of test frequencies 

Figure 47: Variability of RMS overstroke duration across the range of test frequencies 

Variability of Std Deviation of Overstroke Duration with Respect to Angular Offset 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

Variability of Std Deviation of Duration

Et = 0.90

Et = 0.75

Et = 0.60

Variability of RMS Overstroke Duration with Respect to Angular Offset 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

100 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.7 510.9 562.34 908.52

Frequency (MHz)

Variability of RMS Duration

Et = 0.90

Et = 0.75

Et = 0.60
36

5.2.4.2. Variability Across the Reference-Level Range 

Figures 48 to 50 show the variability of the mean, standard deviation and RMS overstroke peak 

amplitude across the range of reference levels. The variability of the mean is contained between 0.2 and 

1.3 for all the frequencies. There appears to be a common convex interval in the variability of the mean 

between the reference levels of 95.0% and around 65.0%, but this could be a coincidence and we have no

insight into what this curve feature represents. Additionally, notice that the variability of the standard 

deviation decreases as the reference level decreases, which induces a slightly similar decreasing pattern 

on the variability of the RMS average. 

Figures 51 to 53 show the variability of the averages for the overstroke duration across the range of 

reference levels. The variability of the mean shows the previously observed general (but not always 

consistent) trend of decreasing variability as the frequency increases. The most significant information 

from these figures are the bounds on the variability of between 0.2 and 1.2 for the mean, between 0.4 and 

1.4 for the standard deviation, and between 0.3 and 1.1 for the RMS. 

Figure 48: Variability of mean overstroke peak amplitude across the range of reference levels 

Variability of Mean Overstroke Peak Amplitude with Respect to Angular Offset 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

95.0 90.0 85.0 80.0 75.0 70.0 65.0 60.0 55.0 50.0

Reference Level (Et %)

Variability of Mean Peak Amplitude

110.07 MHz

316.23 MHz

908.52 MHz
37

Figure 49: Variability of the standard deviation of overstroke peak amplitude across the range reference levels 

Figure 50: Variability of RMS overstroke peak amplitude across the range reference levels 

Variability of Std Deviation of Overstroke Peak Amplitude with Respect to Angular 

Offset 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

95.0 90.0 85.0 80.0 75.0 70.0 65.0 60.0 55.0 50.0

Reference Level (Et %)

Variability of Std Deviation of Peak 

Amplitude

110.07 MHz

316.23 MHz

908.52 MHz

Variability of RMS Overstroke Peak Amplitude with Respect to Angular Offset 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

95.0 90.0 85.0 80.0 75.0 70.0 65.0 60.0 55.0 50.0

Reference Level (Et %)

Variability of RMS Peak Amplitude

110.07 MHz

316.23 MHz

908.52 MHz
38

Figure 51: Variability of mean overstroke duration across the range reference levels 

Figure 52: Variability of the standard deviation of overstroke duration across the range reference levels 

Variability of Mean Overstroke Duration with Respect to Angular Offset 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

95.0 90.0 85.0 80.0 75.0 70.0 65.0 60.0 55.0 50.0

Reference Level (Et %)

Variability of Mean Duration

110.07 MHz

316.23 MHz

908.52 MHz

Variability of Std Deviation of Overstroke Duration with Respect to Angular Offset 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

95.0 90.0 85.0 80.0 75.0 70.0 65.0 60.0 55.0 50.0

Reference Level (Et %)

Variability of Std Deviation of Duration

110.07 MHz

316.23 MHz

908.52 MHz
39

Figure 53: Variability of RMS overstroke duration across the range reference levels 

5.3. Agregated Overstrokes for Mean HSTC Node Susceptibility Threshold Profile 

As described in a previous section, in the HEC experiment, the SUTs were exposed to radiation bursts 

at nominal field over-strengths of 0, 10 and 20 V/m at each test frequency. If we aggregate overstrokes 

over the frequency range, the HEC experiment can be modeled as a stimulus-response experiment in 

which the field over-strength is the primary controlled variable of the stimulus and variables like test 

frequency, stirrer angular offset and revolution are secondary variables. In this section, we consider the 

SIM overstroke populations aggregated over the frequency range using the HSTC susceptibility 

thresholds to specify the overstroke reference-level profile. 

Figure 54 shows the measured susceptibility threshold results in the HSTC experiment for the eight 

physical nodes tested [3]. The figure shows the test frequencies at which none of the nodes experienced 

detectable susceptibility at or below nominal field strength of 300 V/m. In the following analysis, we 

determine the overstroke reference level by using the mean susceptibility threshold at the frequencies with 

demonstrated susceptibility. This HSTC mean-susceptibility-threshold profile is given in Figure 55, 

where the frequencies at which no susceptibility was observed have been removed from the set. The 

remaining frequencies shown in Figure 55 are also the ones listed in Table 1. Let Et

 denote the 

susceptibility threshold at a particular frequency and EOS denote the nominal overstroke over-strength. 

The normalized overstroke reference level, denoted ST, is then computed as follows: 

ST = Et/(Et + EOS) (3) 

Figure 56 shows the overstroke reference-level profiles for the nominal over-strengths. These 

reference levels were applied to the SIM waveforms across the frequency range to generate aggregate 

overstroke sets for each over-strength level. We analyze these overstroke sets by first considering their 

spread over the space of peak amplitude and duration. We then examine the set statistics for the 

overstroke features of peak time duration, peak over duration, peak and duration. 

Variability of RMS Overstroke Duration with Respect to Angular Offset 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

95.0 90.0 85.0 80.0 75.0 70.0 65.0 60.0 55.0 50.0

Reference Level (Et %)

Variability of RMS Duration

110.07 MHz

316.23 MHz

908.52 MHz
40

Figure 54: Measured susceptibility thresholds in the HSTC experiment for the full set of physical nodes 

Figure 55: Mean HSTC node susceptibility thresholds for the set of test frequencies 

Susceptibility Threshold: All Nodes, Position 5, CW

0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

100.000110.069121.153133.352146.780161.560177.828195.734215.443237.137261.016287.298316.228348.070383.119421.697464.159510.897562.341618.966681.292749.894825.404908.518

1000.000

Frequency (MHz)

Field Strength (V/m)

Node 5

Node 6

Node 7

Node 8

Node 1

Node 2

Node 3

Node 4

Hardware Configuration: HC3 for Nodes 5-8 and HC4 for Nodes 1-4, Modulation: CW

Maximum Field Strength: 300.0 V/m

No upsets

Mean Susceptibility Threshold: All Nodes, Position 5, CW

0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

100.00110.07121.15133.35146.78161.56177.83195.73316.23383.12421.70510.90562.34908.52

Frequency (MHz)

Field Strength (V/m)

Hardware Configuration: HC3 for Nodes 5-8 and HC4 for Nodes 1-4, Modulation: CW

Maximum Field Strength: 300.0 V/m
41

Figure 56: Reference levels across the frequency range for the nominal overstroke over-strengths 

5.3.1. Population Spread 

The number of overstrokes at each over-strength level is shown in Figure 57. Interestingly, the 

overstroke count increases linearly in this over-strength range, with about 1740 additional overstrokes for 

every 10 V/m step in nominal over-strength. This is not completely surprising when we consider that, 

based on Figure 20, at most frequencies the relation between overstroke count and reference level is 

approximately linear, and that the counts in Figure 57 are the result of a sum of overstrokes across the 

frequency range with the contribution at each frequency determined by the reference level profiles in 

Figure 56. 

Figure 57: Number of overstrokes for the range of over-strength values 

Overstroke Reference Level Profile for Nominal Overstrengths

0.000

0.200

0.400

0.600

0.800

1.000

1.200

100.00 110.07 121.15 133.35 146.78 161.56 177.83 195.73 316.23 383.12 421.70 510.90 562.34 908.52

Frequency (MHz)

Reference Level

0 V/m

10 V/m

20 V/m

Number of Overstrokes

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20

Overstrength (V/m)

Count
42

Figure 58 shows the scatter plots of overstroke peak amplitude and duration. Compared to the plots in

Figures 21 to 23, the overstrokes in Figure 58 have a larger and more uniform range of coverage, 

especially within the area for overstrokes of less than 0.20 peak amplitude and 150 ms duration. Notice in 

Figure 58 that as the over-strength decreases, the overstroke set for a lower over-strength seems to be a 

subset of the overstroke set at the next higher over-strength. Increasing the over-strength simply increases 

the overstroke spread to a larger area that includes the area covered by overstrokes at lower over-strength. 

Figure 58: Scatter plots of overstroke peak amplitude versus duration for the set of over-strength values 

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Over-strength: 0 V/m 

Over-strength: 10 V/m 

Over-strength: 20 V/m 
43

5.3.2. Statistics of Overstroke Features for the Range of HEC Nominal Overstrengths 

We now consider the set averages, including mean, standard deviation and RMS, for the overstroke 

features of peak amplitude multiplied by duration, peak amplitude divided by duration, peak amplitude 

and duration. 

5.3.2.1. Peak Amplitude Multiplied by Duration 

The set averages of the overstroke normalized peak amplitude multiplied by duration (in ms) for the 

range of nominal over-strength levels are shown in Figure 59. The RMS value is clearly driven by the 

standard deviation, which is about twice as large as the mean across the over-strength range. The 

standard deviation grows faster than linear relative to the over-strength because of the simultaneous 

increase in the spread of the basic overstroke dimensions of peak amplitude and duration for larger overstrength, as can be seen in the scatter plots in Figure 58. The relatively small value of the mean is related 

to the high density clustering of overstrokes at the low end of the peak amplitude and duration where, as 

seen in Figure 58, the area coverage is also very high compared to other areas of the plots. 

Figure 59: Averages of the overstroke peak amplitude multiplied by the duration for the range of over-strength 

values 

5.3.2.2. Peak Amplitude Divided by Duration 

Figure 60 shows the statistical averages for the overstroke peak amplitude divided by the duration for

the range of over-strengths. The sub-linear increase in the mean is an indication that the overstroke

duration increases faster than the peak amplitude as the over-strength increases. The standard deviation 

increases by a small amount from one end to the other of the over-strength range, but it actually decreases 

slightly in going from 0 to 10 V/m. From comparing the curves in Figures 37 and 40, we suspect that this 

trend in the standard deviation is the result of the interplay between the standard deviations of the peak 

amplitude and the duration as the reference level decreases (i.e., as the over-strength increases). Another 

possibility is that the values at 0 V/m (i.e., 100% reference level) are not representative of overstrokes 

Statistics of Overstroke Peak Amplitude Multiplied by Duration for Range of Overstrength Values

0

5

10

15

20

25

30

0 10 20

Overstrength (V/m)

OS Peak times Duration 

RMS

Average

Std Deviation
44

generated by the full set of available SIM waveforms because those with absolute peak amplitude smaller 

than the normalizing median peak amplitude do not contribute overstrokes to the 0 V/m set. Further 

analysis would be required to explain the pattern in Figure 60. Finally, the RMS profile is mainly 

determined by the mean value. 

Figure 60: Averages of the overstroke peak amplitude divided by the duration for the range of over-strength levels 

5.3.2.3. Peak Amplitude 

The statistical averages of the overstroke peak amplitude across the over-strength levels are shown in

Figure 61. The pattern of these curves is consistent with the plots of peak amplitude averages versus

reference level in Figures 36 to 38. An interesting feature of the statistical mean in Figure 61 is the 

reduction in the rate of increase as the over-strength increases. This trend may be related to the slower 

rate of increase of the peak amplitude as the reference level decreases for high frequencies, as shown in 

Figure 36. However, more in-depth analysis is needed to gain insight into the cause of this trend. 

5.3.2.4. Duration 

Figure 62 shows the statistical averages for the overstroke duration over the range of over-strengths. 

The trends for the duration are similar to those for the peak amplitude in Figure 61, though there is a 

larger reduction in the rate of increase of the mean. Based on the results in Figure 39 to 41, we were 

expecting the duration averages in Figure 61 to maintain the rate of increase as the over-strength 

increases. The reduction actually shown in Figure 61 may be related to the reference level profile in

Figure 56. Here again, more detailed analysis is needed to understand the cause of this trend. 

Statistics of Overstroke Peak Amplitude Divided by Duration for Range of Overstrength Values

0.00

0.50

1.00

1.50

2.00

2.50

0 10 20

Overstrength (V/m)

OS Peak divided by Duration (1e3)

RMS

Average

Std Deviation
45

Figure 61: Averages of the overstroke peak amplitude for the range of over-strength levels 

Figure 62: Averages of the overstroke duration for the range of over-strength levels 

Statistics of Overstroke Peak Amplitude for Range of Overstrength Values

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0 10 20

Overstrength (V/m)

Overstroke Peak Amplitude (normalized)

RMS

Average

Std Deviation

Statistics of Overstroke Duration for Range of Overstrength Values

0

20

40

60

80

100

120

0 10 20

Overstrength (V/m)

Overstroke Duration (milliseconds)

RMS

Average

Std Deviation
46

6. Final Remarks 

In this report, we have analyzed the radiated field strength in an electromagnetic reverberation 

chamber as an upset-inducing stimulus for digital systems. It has been shown that, for a given input 

power and test frequency, the field strength at a point in the chamber varies as a function of the stirrer 

angular position and relative angular offset between the stirrers, and that it is cyclic with period equal to 

the time for the stirrers to complete a revolution. We have given strong evidence that the magnitude of 

the field strength beyond the susceptibility threshold of the SUT has a causal relation with the 

characteristics of the error bursts observed at the outputs of the SUT. The statistics of the field overstroke 

features of peak amplitude and duration have been analyzed, and it was shown how the features are 

dependent on the test frequency and overstroke reference level, which is equal to the ratio of the SUT’s 

susceptibility threshold divided by the peak field strength. We have determined bounds for the 

differences in the statistical averages of the overstroke features between tests with different stirrer angular 

offsets. Finally, for a representative susceptibility profile across the test frequency range, it was shown 

how the statistics of the overstroke features vary as a function of the nominal field over-strength. 

The analysis presented here is for field strength measurements taken at the fixed position of the 

receive antenna in the reverberation chamber, as shown in Figures 1 to 3. At this time, we have no direct 

evidence that these measurements are applicable to other areas of the chamber. However, the fact that the 

measured susceptibility thresholds in the HSTC experiment followed a similar profile when the SUTs 

were located at different positions in the chamber, and the previously measured field strength uniformity 

given in report [7], both serve as indirect evidence that the results given here apply throughout the test 

volume of the chamber. We believe that the effect of a change in position is similar to the effect of a 

change in stirrer angular offset. This may be investigated in future tests. 
47

Appendix A. Stirrer-Induced Modulation Waveforms 

This appendix contains some of the field strength traces gathered during the Stirrer Induced 

Modulation Test. The traces are given for every test frequency at 0-degree stirrer angular offset and

include all the revolution samples taken at intervals of 30 seconds. The traces are amplitude normalized 

and synchronized. 

Figure A.1: Stirrer induced modulation at 100.00 MHz 

Figure A.2: Stirrer induced modulation at 110.07 MHz 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec
48

Figure A.3: Stirrer induced modulation at 121.15 MHz 

Figure A.4: Stirrer induced modulation at 133.35 MHz 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec
49

Figure A.5: Stirrer induced modulation at 146.78 MHz 

Figure A.6: Stirrer induced modulation at 161.56 MHz 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec
50

Figure A.7: Stirrer induced modulation at 177.83 MHz 

Figure A.8: Stirrer induced modulation at 195.73 MHz 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec
51

Figure A.9: Stirrer induced modulation at 316.23 MHz 

Figure A.10: Stirrer induced modulation at 383.12 MHz 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec
52

Figure A.11: Stirrer induced modulation at 421.70 MHz 

Figure A.12: Stirrer induced modulation at 510.90 MHz 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec
53

Figure A.13: Stirrer induced modulation at 562.34 MHz 

Figure A.14: Stirrer induced modulation at 908.52 MHz 

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

0 sec

30 sec

60 sec

90 sec

120 sec

150 sec

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 0.32 0.63 0.95 1.26 1.58 1.90 2.21 2.53 2.84 3.16 3.48 3.79 4.11 4.42 4.74

Stirrer Position (seconds)

Normalized Field Strength

180 sec

210 sec

240 sec

270 sec

300 sec
54

Appendix B. Overstroke Population at Test Frequencies 

This appendix contains scatter plots of overstroke peak amplitude versus duration for the full set of the 

frequencies at reference levels of 0.90, 0.75, and 0.60. The overstroke sets were formed by aggregation 

over the range of stirrer angular offsets and revolutions. SIM traces with the same frequency and angular 

but for different revolutions were not synchronized prior to generation of the overstrokes. 

Figure B.1: Scatter plots for overstroke peak amplitude versus duration at 100.00 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
55

Figure B.2: Scatter plots for overstroke peak amplitude versus duration at 110.07 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
56

Figure B.3: Scatter plots for overstroke peak amplitude versus duration at 121.15 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.60 

Reference Level: 0.90 

Reference Level: 0.75 
57

Figure B.4: Scatter plots for overstroke peak amplitude versus duration at 133.35 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
58

Figure B.5: Scatter plots for overstroke peak amplitude versus duration at 146.78 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
59

Figure B.6: Scatter plots for overstroke peak amplitude versus duration at 161.56 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
60

Figure B.7: Scatter plots for overstroke peak amplitude versus duration at 177.83 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.75 

Reference Level: 0.60 

Reference Level: 0.90 
61

Figure B.8: Scatter plots for overstroke peak amplitude versus duration at 195.73 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
62

Figure B.9: Scatter plots for overstroke peak amplitude versus duration at 316.23 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
63

Figure B.10: Scatter plots for overstroke peak amplitude versus duration at 383.12 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
64

Figure B.11: Scatter plots for overstroke peak amplitude versus duration at 421.70 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
65

Figure B.12: Scatter plots for overstroke peak amplitude versus duration at 510.90 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
66

Figure B.13: Scatter plots for overstroke peak amplitude versus duration at 562.34 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
67

Figure B.14: Scatter plots for overstroke peak amplitude versus duration at 908.52 MHz 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Peak Amplitude (normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 100 200 300 400 500 600 700 800 900 1000

Duration (ms)

Peak Amplitude (normalized)

Reference Level: 0.90 

Reference Level: 0.75 

Reference Level: 0.60 
68

References

[1] Torres-Pomales, W.; et al: Plan for the Characterization of HIRF Effects on a Fault-Tolerant Computer 

Communication System. NASA-TM-2008-215306, May 2008. 

[2] Torres-Pomales, W.; et al: Design of Test Articles and Monitoring System for the Characterization of 

HIRF Effects on a Fault-Tolerant Computer Communication Systems. NASA-TM-2008-215322, July 

2008. 

[3] Torres-Pomales, W.: Characterization of HIRF Susceptibility Threshold for a Prototype 

Implementation of an Onboard Data Network. NASA/TM-2012-217754, August 2012. 

[4] Belcastro, Celeste M.: Laboratory Test Methodology for Evaluating the Effects of Electromagnetic 

Disturbances on Fault-Tolerant Control Systems. NASA Technical Memorandum 101665, November 

1989. 

[5] Fuller, Gerald L.: Understanding HIRF – High Intensity Radiated Fields. Aviation Communications, 

Inc., Leesburg, VA, 1995, p. 7-2. 

[6] Hess, Richard: Computing Platform Architectures for Robust Operation in the Presence of Lightning 

and Other Electromagnetic Threats. 16th Digital Avionics Systems Conference (DASC), 1997. 

[7] Ladbury, J.; Koepke, G.; Camell, D.: “Evaluation of the NASA Langley Research Center Mode-Stirred

Chamber Facility”, NIST Technical Note 1508, January 1999. 

[8] Ely, Jay J.; Nguyen, Truong X.; and Scearce, Stephen A.: The Influence of Modulated Signal Risetime 

in Flight Electronics Radiated Immunity Testing with Mode-Stirred Chamber. NASA/TM-2000-

209844, January 2000. 

[9] Torres-Pomales, Wilfredo; et al: ROBUS-2: A Fault-Tolerant Broadcast Communication System. 

NASA/TM-2005-213540, March 2005. 

[10] Torres-Pomales, Wilfredo; et al: Design of the Protocol Processor for the ROBUS-2 Communication 

System. NASA/TM-2005-213934, November 2005. 

[11] Torres-Pomales, Wilfredo: An Approach for the Assessment of System Upset Resilience. NASA/TM, 

2012, under review. 

 
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

2. REPORT TYPE 

Technical Memorandum

 4. TITLE AND SUBTITLE

Analysis of the Radiated Field in an Electromagnetic Reverberation 

Chamber as an Upset-Inducing Stimulus for Digital Systems

5a. CONTRACT NUMBER

 6. AUTHOR(S)

Torres-Pomales, Wilfredo

 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

NASA Langley Research Center

Hampton, VA 23681-2199

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14. ABSTRACT

Preliminary data analysis for a physical fault injection experiment of a digital system exposed to High Intensity Radiated 

Fields (HIRF) in an electromagnetic reverberation chamber suggests a direct causal relation between the time profile of the 

field strength amplitude in the chamber and the severity of observed effects at the outputs of the radiated system. This report

presents an analysis of the field strength modulation induced by the movement of the field stirrers in the reverberation 

chamber. The analysis is framed as a characterization of the discrete features of the field strength waveform responsible for the 

faults experienced by a radiated digital system. The results presented here will serve as a basis to refine the approach for a 

detailed analysis of HIRF-induced upsets observed during the radiation experiment. This work offers a novel perspective into 

the use of an electromagnetic reverberation chamber to generate upset-inducing stimili for the study of fault effects in digital

systems.

15. SUBJECT TERMS

Avionics; Data network; Electromagnetic field; Resilience; Safety

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