NISTIR 89-3928

FACILITIES FOR

IMPROVING EVALUATIONS OF

ELECTROMAGNETIC SUSCEPTIBILITIES

OF WEAPON SYSTEMS AND

ELECTRONIC EQUIPMENT

M.T. Ma

M.L. Crawford

National Institute of Standards and Technology

U.S. Department of Commerce

Boulder, Colorado 80303-3328

November 1989
u.

.

-J.
NISTIR 89-3928

FACILITIES FOR

IMPROVING EVALUATIONS OF

ELECTROMAGNETIC SUSCEPTIBILITIES

OF WEAPON SYSTEMS AND

ELECTRONIC EQUIPMENT

MX. Ma

M.L. Crawford

Electromagnetic Fields Division

Center for Electronics and Electrical Engineering

National Engineering Laboratory

National Institute of Standards and Technology

Bouideiv Colorado 80303-3328

November 1989

Sponsored, in part, by

Naval Sea Systems Command

Washington, DC 20362-5101

U.S. DEPARTMENT OF COMMERCE, Robert A. Mosbacher, Secretary

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY, Raymond G. Kammer, Acting Director

CONTENTS

Page

Abstract 1

1. Introduction 1

2. Design Requirements and Sample Results . 2

3. Potential Options 5

4. Conclusions and Recommendations 7

5. Acknowledgments 8

6 . References 8

iii

FACILITIES FOR IMPROVING EVALUATIONS OF ELECTROMAGNETIC SUSCEPTIBILITIES

OF WEAPON SYSTEMS AND ELECTRONIC EQUIPMENT

M. T. Ma and M. L. Crawford

Electromagnetic Fields Division

National Institute of Standards and Technology

Boulder, CO 80303

A preliminary design of an improved testing facility for evaluating

the electromagetic susceptibility of weapon systems and electronic

equipment is presented. This facility features a combination of the

transverse electromagnetic (TEM) cell for low-frequency testing and

the reverberating chamber for high-frequency operation. As a system,

a coverage of the wide spectrum from 10 kHz to 18 GHz or even to 40

GHz is possible. The TEM/reverberating combination is designed for

an input impedance of 50, 75, or 100 Cl to generate a cw electric

field up to 200 V/m, or a pulsed electric field up to 50 kV/m with

an approximate rise time of 10 ns. The average field for the

reverberating mode of operation is described in a statistical sense.

Theoretical characteristics for a case study, to meet a given set of

requirements, are given.

Key words: EMC test; reverberating chamber; TEM cell; susceptibility.

1. Introduction

The ability to simulate an operating electromagnetic (EM) environment for

accurately assessing the cw and pulsed susceptibilities of weapon and

electronic systems is fundamental to ensuring the system's compatibility.

In recent years, the Fields and Interference Metrology Group of the National

Institute of Standards and Technology (NIST) has been developing two

facilities, based on sound theoretical understanding of the problem, for

this task [1]. They are the transverse electromagnetic (TEM) cell [2] and

the reverberating chamber [3, 4, 5]. Each facility has its advantages and

limitations

The TEM cell, shown in figure 1, is an expanded rectangular coaxial

transmission line with tapered sections at each end. It provides a shielded

environment for measuring both EM susceptibility and emissions of equipment

under test (EUT) [6, 7, 8]. Ideally, the TEM cell generates only the TEM

mode to simulate the free-space planar field by^neans of a source suppJLied

at one end with a matched load connected to the other end. To support such

a TEM mode, the cell is necessarily a two-conductor system with the region

between the inner and outer conductors (either chamber) used as the test

zone. Although the center septum (inner conductor) is normally designed to

be midway between the outer conductors, its position can be modified to have

an offset to allow a larger test zone in one of the chambers [9, 10], The

cell is generally limited to upper frequencies below a few hundred

megahertz, depending on the EUT size, to avoid the appearance of the higher

order modes [11]. The volume available for testing is inversely

proportional to the upper frequency limit. For a given TEM cell size,

higher order modes will appear when the operating frequency increases. The

1
cutoff frequencies of the first few higher order modes generated inside a

cell with an infinitely long central section can be determined numerically

[10, 11]. Since the length of the central section is finite in practice, the

transitional sections near the ends will act as a cavity to produce resonant

frequencies associated with these cutoff frequencies. In addition, because

the polarization of the field generated inside the cell is fixed, systematic

rotations of the EUT may be necessary to fully evaluate the EUT's

transmitting and receiving characteristics [7, 8].

The reverberating (or mode stirred) chamber, shown in figure 2, is also a

shielded room with a rotating stirrer to mix the field generated by a

transmitting antenna. This field is very complex, and is described in terms

of simple statistics such as maximum and average amplitudes for a large

number of different stirrer positions. It is considered uniformly

homogeneous and isotropic when averaged. Because of this, the EUT is not

required to undergo physical rotations, so this method of testing is very

cost effective. However, this facility is restricted to frequencies above a

few hundred megahertz, again depending on the chamber size. This

restriction is a consequence of requiring the chamber to be electrically

large so that there will be enough modes to ensure adequate mode mixing and,

hence, spatial uniformity for testing purposes [12, 13].

We are currently investigating the possibility of combining these two

measurement concepts to produce a single facility that can be used for EMC

testing over a much wider frequency range [14]. Design considerations for

a particular model based on this experience, and preliminary results for

this model with an assumed set of requirements, are given in Section 2.

Other alternative facilities existing elsewhere are suggested in Section 3

and may also be considered for mee.ting specific measurement needs.

Concluding remarks and recommendations are summarized in Section 4.

2. Design Requirements and Sample Results

When evaluating the EMC susceptibility of weapon systems and electronic

equipment by a combined TEM cell and reverberating chamber as typically

required by a military agency, it is quite common to specify:

(a) frequency of interest from 10 kHz to 18 GHz with a capability of

extending to 40 GHz

(b) cw electric field up to 200 V/m,

(c) pulsed electric field up to 50 kV/m with approximately 10 ns rise

time

(d) possible workable test volume inside the full-scale chamber to be

occupied by an EUT as large as 6mx9mxl2m,

(e) shielding effectiveness of the chamber walls no less than 100 dB,

and

(f) different types of modulations (AM or FM)

2
Based on the tentative requirements listed above, design considerations

for the TEM cell consist of a suitable cell size, materials to be selected

for constructing the cell, the input impedance as a function of the cell

geometry, relative field distribution inside the empty cell, the power

required from the signal source, and the cutoff and resonant frequencies of

the first few higher order modes. Design parameters for the reverberating

mode of operation are the available volume and total surface area of the

chamber, the number of possible modes generated inside the chamber as a

function of frequency, the mode density necessary to yield uniform fields

after averaging, and the quality factor, which is important to determine the

trade-off between power requirement and bandwidth for proper operation of

the facility.

To provide a large test zone as specified in (d) above and at the same

time to require that the original uniform field generated inside the chamber

by the TEM mode of operation for lower frequencies not be seriously

disturbed by the presence of EUT, it is estimated that the full-scale

physical size of the facility will take at least 18 m x 21 . 34 m x 53 m. A

scaled model (1/17.8) will have the dimension of 101 cm x 120 cm x 298 cm,

as shown in figure 3. The unique feature is a vertically offset center

septum used for the TEM cell to provide a larger usable test volume than the

ordinary symmetrical TEM cell for the same overall size.

Any one of the three commonly available metals: aluminum, steel, or zinccoated steel, may be used in construction. Once a metal with known values

of conductivity and permeability is chosen, the skin depth of the chamber

walls can be calculated and an adequate thickness for the chamber walls can

be determined to provide a shielding protection of at least 100 dB.

The input impedance of the TEM cell may be designed at 50 fl, 75 0, or 100

Q, depending on the choice of center conductor width [10]. Because of the

particular choice of offset for the center conductor shown in figure 3, we

propose to use the dimensions given in figure 4 for the cell's cross

section. For the full-sized cell with 2a (cell width) - 18 m, 2b (over cell

height) - 21.34 m, and h^ (center conductor- to -ground height) — 16 m, we

require

2w (width of the center conductor) in m Input impedance in Q

13.5 50

10.8 75

9.0 100

For the scaled cell model, 2a = 101 cm, 2b =* 120 cm, tu - 89 cm, and

75.8 cm for an input impedance of 50 0,

2w - 60.6 cm for an input impedance of 75 0,

50.5 cm for an input impedance of 100 0.

The estimated relative electric-field distribution in the cross sectional

testing area, based only on the TEM mode, is similar to that given in figure

5 , where V is the voltage between the center and outer conductors . Thus

for a net input power of 1 W supplied to the full-sized cell, we have:

3
Voltage between center Input impedance Electric field generated

and outer conductors in G at midway of the test

in V zone, in V/m

7.07 50 0.44

8.67 75 0.54

10.00 100 0.63

The net power required to produce an electric field of 200 V/m at the

midway of the test zone ranges between 0.1 to 0.2 MW, depending on the

designed input impedance.

The corresponding electric fields at the midway of the test zone for the

scaled model with a net input power of 1 W will be respectively 7.94, 9.74,

and 11.24 V/m when the input impedance is designed at 50 0, 75 G, and 100 G.

To generate a field of 200 V/m at the test center of the scaled model will,

therefore, require a net input power from 300 to 600 W.

The first few higher order modes which may occur inside the TEM cell are

TEq^, te ^q> and TE-q modes [1]. The TEq^ mode will appear at approximately,

for the full-sized cell, 5.3 MHz with 50 G, 6.5 MHz with 75 G, and 7.3 MHz

with 100 G. For the scaled model, these frequencies become respectively

94.3 MHz, 115.7 MHz, and 130.0 MHz. The TE^q mode appears approximately at

8.3 MHz for the full-sized and 148.3 MHz for scaled model, regardless of the

input impedance. For the TE^ mode, the cutoff frequencies are 11.1 MHz for

the full size and 197.6 MHz for the scaled model. Thus, the TEM mode of

operation is estimated to be good from dc to 5.3 MHz (50 0) , to 6.5 MHz (75

G), or to 7.3 MHz (100 G) for the full-sized model; and from dc to 94.3 MHz

(50 G)

to 115.7 MHz (75 G) , or to 130.0 MHz (100 G) for the scaled model.

If, however, some absorbing materials are installed inside the cell, the

cutoff frequencies could be increased to 10 MHz for the full-sized and to

180 MHz for the scaled model [15]

In general, a longer width chosen for the center conductor will result in

lower input impedance, a more uniform field distribution, a higher input

power requirement, and a lower cutoff frequency.

For the mode-stirred operation, the total volume of the full-sized

chamber is approximately 14 277 m

3 and the surface area is about 3 170 m

2

. The number of modes existing in this volume at 18 MHz is about 25 which is

considered a minimum required for producing a statistically uniform average

field distribution. The corresponding volume and surface area for the

scaled model, and its equivalent frequency to produce a minimum of 25 modes

are respectively 2.531 m

3

, 10.005 m

2

, and 320 MHz. Thus, the transitional

frequency regions between the TEM mode operation and the mode -stirred

operation are approximately from 10 MHz to 18 MHz for the full-sized and

from 180 MHz to 320 MHz for the scaled model. At higher frequencies, the

number of modes to be generated inside the chamber will also be increased

[12, 13], In fact, the number of modes is proportional to the third power

of frequency.

4
Another important factor to consider in the design of a reverberating

chamber is the mode density [1]. It represents the change in the number of

modes in a given frequency interval. The smoothed mode density function for

the designed full-sized model is shown in figure 6.

A third design criterion for a reverberating chamber is the quality

factor, which helps to determine the power required to generate a desired

average field at the test zone. For the full-sized model, the theoretically

estimated composite quality factors [1] at 18 MHz are respectively 35.20 x

10 4

, 23.27 x 10 4

, and 13.95 x 10 4 for the chambers made of aluminum, zinccoated steel, and steel. This composite factor is considered the upper

limit. In practice, because of possible rf leaks and/or absorption by

equipment placed inside the chamber, the realistic quality factor will be

reduced. At sufficiently high frequencies (> 100 MHz) , the composite

quality factor is reduced approximately by a factor of 2 to 5 [12].

Therefore, the net powers required to generate an average electric field

level of 200 V/m at frequencies above 100 MHz are about 27.0 W, 40.9 W, and

68.2 W respectively for aluminum, zinc-coated steel, and steel chambers.

This required net power will be increased somewhat for frequencies below 100

MHz and at frequencies above a few gigahertz. For the scaled model, the

composite quality factors at 1.7 GHz are estimated to be 1.92 x 10 s

, 1.27 x

10 s

, and 0.76 x 10 s respectively for aluminum, zinc-coated steel, and steel.

The corresponding required net powers for generating an electric field of

200 V/m are 0.5 W, 0.7 W, and 1.3 W at frequencies above 1.7 GHz.

Because of the space limitation, the stirrer size inside the scaled model

as indicated in figure 3 is about 52 cm in length. According to our

estimation based on a theoretical study of a one -dimensional stirrer, it

will be effective to produce a uniform average field inside the chamber when

it is about 2.4A or greater, whefe A is the wavelength [16]. In terms of

frequency, this stirrer size is a good design for 1.38 GHz or higher. Since

our proposed stirrer is two-dimensional with a narrow width, the lowest

frequency for it to be effective is estimated at 1 GHz. For the full-sized

chamber, the stirrer is 9.25 m long and 2.85 m wide. It should meet the

requirement for frequencies higher than 60 MHz.

To generate an electric field up to 50 kV/m with ,a 10 ns rise time, we

need a pulsed voltage source of 800 kV for the full chamber, or a pulsed

voltage source of 50 kV for the scaled model. Each model will require

special transitional input sections to prevent high-voltage arcing.

The above preliminary design results are, pf course, good specifically

for the chamber size (whether full or scaled) we assumed at the beginning of

this section. Chamber size and geometry will be adjusted by a similar set

of design guidelines when the required workable test volume is changed.

3. Potential Options

The TEM cell configuration proposed above has a section of rectangular

coaxial transmission line tapered at each end to adapt to standard coaxial

connectors. This design of three different sections is the reason for

resonances as mentioned in Section 2. The travelling wave excited by the

source does not reach the load simultaneously, thus causing some reflections

5
or even creating some non-TEM modes. An alternative to this is the ABB cell,

model 1500 (called GTEM-1500) as shown in figure 7 [17]. This particular

model was designed for EUTs up to the size oflmxlmx0.5min order to

ensure a good field uniformity and small load effect. The height^ of the

center conductor is 1.5 m. The overall dimensions are 3mx2mx6.5m.

The high-power load resistors are installed to allow a maximum cw power of 1

kW, resulting in an electric field of at least 200 V/m. A pulsed voltage of

100 kV can also be applied to generate a pulsed electric field of more than

50 kV/m. The measured reflections are within +2 % and -5 %. The input

impedance varies from 45 Q to 52 Q. Measured pulsed fields also indicate

good fidelity. This model is currently available in the United States.

Tests, however, are needed to confirm these figures and may be conducted

through an arrangement with the manufacturer. Presumably this model could

also be scaled up to accommodate larger test volumes with proportionally

greater input powers to generate cw fields up to 200 V/m or pulsed fields up

to 50 kV/m.

Another alternative is the symmetrical end- loaded TEM cell shown in

figure 8. This facility is available elsewhere [18]. This model offers a

reduced length for the tapered section and uses absorbers for wave

termination. An arrangment for NIST to make some tests inside this cell

for determining its applicability to the task specified in Section 2 is also

possible

A third option is the TEM-driven reverberating chamber currently being

designed and investigated at NIST for the U.S. Army [14]. This chamber is

also a shielded facility. The TEM cell has three individual orthogonal

center conductors (top, back, and end), so that we do not need to rotate the

EUT physically inside the cell. The input impedance of this ceil is

designed at 100 Q. The test volume in this full-sized chamber, when used in

the reverberating mode, is 8 m x 16 m x 30 m. A scaled model (1/10) with

the overall size of 1.31 m x 2.41 m x 3.87 m has been constructed for

evaluation. The cross section with a top plate as the center conductor has

the dimensions of 2a = 3.87 m, 2b = 1.31 m, 2w = 0.46 m, and h. = 1.06 m

l

(referred to figure 4). The theoretically estimated electric - field

amplitude (square root of the sum of the squares of the x- and ycomponents) distribution inside this cross section, relative to the center

value at x = 0 and y — tu/2 may be summarized as follows [19]:

x - 0 ± a/3 ± a/2 ± 2a/3 ± a

3h./4 1.117 0.983 0.811 0.636 0.438

V2 1.000 0.864 0.706 0.522 0.257

V4 0.931 0.799 0.645 0.459 0.118

0 0.908 0.779 0.629 0.439 0.000

For the cross section with a back plate as the center conductor, we have

2a - 1.31 m, 2b — 2.41 m, 2w - 0.46 m, tu - 2.11 m, and the normalized

electric-field amplitude distribution as follows:

6
x “ 0 ± a/3 ± a/2 ± 2a/3 ± a

3h

t

/4 3.477 3.517 3.550 3.5853 3.610

h./2

y

- if

1.000 0.999 0.999 0.998 0.997

h./4 0.305 0.295 0.217 0 . 154 0.026

0 0.159 0.138 0.113 0.080 0.000

For the cross section with an end plate as the center conductor, we

2a - 1.31 m, 2b “3.87 m, 2w =* 0.46 m, h - 3.57 m, and the normalized

electric-field amplitude distribution as follows:

x - 0 ± a/3 ± a/2 ± 2a/3 ± a

3h

t

/4 8.475 8.489 8.503 8.516 8.530

h./2

y

- * 1.000 1.000 1.000 1.000 1.000

h./4 0.118 0.118 0.118 0.118 0.118

0 0.028 0.024 0.020 0.014 0.000

Two stirrers will also be installed in this facility. Each is operated

independently under computer control to select appropriate stirrer position

and its revolution rate. As a whole, the operation of this chamber will be

divided into three distinct regions in frequencies: (1) the TEM mode ranging

from 10 kHz to 10 MHz, (2) the transition approximately from 10 to 30 MHz,

and (3) the mode-stirred region from 30 MHz to 18 GHz or higher. Test

fields will be excited in the chamber at frequencies up to 1 GHz by using

either the transmission lines or transmitting antennas such as biconic, logspiral, or log-periodic antennas. At frequencies above 1 GHz, ridged horn

antennas will be used. A 10 kW source should be sufficient to generate a

test field up to 100 V/m for the TEM mode of operation, and a 200 W

amplifier should generate a test field up to 200 V/m for the reverberating

operation.

If test results confirm the theoretical predictions, the chamber may be

used directly or modified to meet the need for the hypothetical sample

considered in Section 2.

4. Conclusions and Recommendations

A preliminary design of an improved testing facility for evaluating the

EM susceptibility of weapon systems and electronic equipment has been

presented. The facility consists of a combination of the TEM cell and the

reverberating (mode -stirred) chamber. The TEM mode of operation is intended

for lower frequency range from 10 kHz to perhaps 10 MHz, and the modestirred mode of operation is for higher frequency band from 23 MHz to 18 GHz

with a possible extension to 40 GHz. The transitional region is from 10 MHz

to 23 MHz, in which the first few higher order modes may be excited but are

not sufficient in number for the chamber to reverberate properly. The scaled

7
model specifically discussed in Section 2 should be constructed for

evaluating its characteristics. If satisfactory, the full-sized model may

then be considered. In the meantime, evaluation and necessary tests with

the alternative and supplementary facilities outlined in Section 3 should

also be conducted by us to derive a cost-effective and improved EMC testing

environment for meeting a given set of specific criteria.

5 . Acknowledgments

The work described in this report is partially supported by the Naval Sea

Systems Command.

6. References

[1] Ma, M. T.; Kanda, M. Electromagnetic compatibility and interference

metrology. NBS Tech. Note 1099; 1986 July.

[2] Crawford, M. L. Generation of standard EM fields using TEM

transmission cells. IEEE Trans, on Electromag. Compat. EMC- 16 (no. 4):

189-195; 1974 November.

[3] Corona, P. ; Latmiral, G. ; Paolini, E. ; Piccioli, L. Use of a

reverberating enclosure for measurements of radiated power in the

microwave range. IEEE Trans. Electromag. Compat. EMC-18 (no. 2): 54-

59; 1976 May.

[4] Bean, J. L. ; Hall, R. A. Electromagnetic susceptibility measurements

using a mode -stirred chamber. IEEE Int. Symp. on EMC; 1978 June;

Atlanta, GA.

[5] Crawford, M. L. ; Koepke, G. H. Design, evaluation and use of a

reverberation chamber for performing electromagnetic

susceptibility/vulnerability measurements. NBS Tech. Note 1092; 1986

April

[6] Crawford, M. L. ; Workman, J. L. Using a TEM cell for EMC measurements

of electronic equipment. NBS Tech. Note 1013; Revised 1981 July.

[7] Sreenivasiah, I.; Chang, D. C.; Ma, M. T. Emission characteristics of

electrically small radiating sources from tests inside a TEM cell.

IEEE Trans, on Electromag. Compat., EMC-23 (no. 3): 113 - 121; 1981

Augus t

[8] Ma, M. T. ; Koepke, G. H. A method to quantify the radiation

characteristics of an unknown interference source. NBS Tech. Note

1059; 1982 October.

[9] Crawford, M. L. ; Workman, J. L. Asymmetric versus symmetric TEM cell

for EMC measurements. IEEE Int. Symp. on EMC, 1978 June, Atlanta, GA.

[10]

Tippet, J. C. Modal characteristics of rectangular coaxial

transmission line. Ph. D. dissertation, Dept, of Electrical

Engineering, Univ. of Colorado, Boulder; 1978.

8
[11] Tippet, J. C. ; Chang, D. C. Higher order modes in rectangular coaxial

line with infinitely thin inner conductor. NBS Int. Rept. 78-873; 1978

March.

[12] Liu, B. H. ; Chang, D. C. ; Ma, M. T. Eigenmodes and the composite

quality factor of a reverberating chamber. NBS Tech. Note 1066; 1983

Augus t

[13] Liu, B. H. ; Chang, D. C.; Ma, M. T. Design consideration of

reverberating chambers for electromagnetic interference measurements.

IEEE Int. symp. on EMC; 1983 August; Arlington, VA.

[14] Crawford, M. L. TEM driven reverberating chamber design concept study:

a single facility for large system radiated EMC testing, 10 kHz - 40

GHz, EMC EXPO Symp. Record; 1989 August; Washington, DC.

[15] Crawford, M. L. ; Workman, J. L. ; Thomas, C. L. Expanding the bandwidth

of TEM cells for EMC measurements. IEEE Trans, on Electromag. Compat.

EMC -20 (no. 3): 368 - 375; 1978 August.

[16] Wu, D. I.; Chang, D. C. The effect of a large rotating scatterer in a

rectangular cavity. NBS Tech. Note 1317; 1988 March.

[17] Konigstein, D. ; Hansen, D. A new family of TEM-cells with enlarged

bandwidth and optimized working volume. Proc. 7th Symp. Tech.

Exhibition on EMC; 1987 March; Zurich, Switzerland.

[18] Pollard, N. A broadband electromagnetic environment simulator (EMES)

IEEE Int. Symp. on EMC, 1977 August, Seattle, WA.

[19] Wilson, P. F. On slot-coupled waveguide and transmission line

structures. Ph. D. dissertation, Dept, of Electrical Engineering , Univ. of Colorado, Boulder; 1983.

9
Figure 1. TEM cell for EM susceptibility testing.

Figure 2. Reverberating chamber for EM susceptibility testing.

10
Figure 3. Sketch of the scaled model of a TEM/reverberating

chamber as an EMC/EMP testing facility. Dimensions are in cm.

11
Outer conductor

2a

gure 4. Cross section of the TEM cell.

12
Position, x

(a)

(b)

Figure 5. Relative field distribution inside the cross

section of a TEN! cell, (a) general field orientation,

and (b) as a function of heights.

13
Mode

density

(sec)

X

10

1

Frequency (MHz)

Figure 6. Mode density for the full size reverberating chamber as

a function of frequency.

14
Figure 7. Schematic drawing of ABB gigahertz TEM cell.

15
Figure 8. A broadband electromagnetic environment

simulator (EMES).

16
NIST-1 14A U.S. DEPARTMENT OF COMMERCE

(REV. 3-89) NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY

BIBLIOGRAPHIC DATA SHEET

1. PUBUCATION OR REPORT NUMBER

NISTIR 89-3928

2. PERFORMING ORGANIZATION REPORT NUMBER

3. PUBUCATION DATE

November 1989

4. TITLE AND SUBTITLE

FACILITIES FOR IMPROVING EVALUATIONS OF ELECTROMAGNETIC SUSCEPTIBILITIES OF

WEAPON SYSTEMS AND ELECTRONIC EQUIPMENT

5. AUTHOR(S)

M. T.'Ma and M. L. Crawford

6. PERFORMING ORGANIZATION (IF JOINT OR OTHER THAN NIST, SEE INSTRUCTIONS)

U.S. DEPARTMENT OF COMMERCE

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY

GAITHERSBURG, MD 20899

7. CONTRACT/GRANT NUMBER

8. TYPE OF REPORT AND PERIOD COVERED

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (STREET, CITY, STATE, ZIP)

Supported, in part, by

Naval Sea Systems Command

10. SUPPLEMENTARY NOTES

DOCUMENT DESCRIBES A COMPUTER PROGRAM; SF-185, FIPS SOFTWARE SUMMARY, IS ATTACHED.

11. ABSTRACT (A 200-WORD OR LESS FACTUAL SUMMARY OF MOST SIGNIFICANT INFORMATION. IF DOCUMENT INCLUDES A SIGNIFICANT BIBLIOGRAPHY OR

UTERATURE SURVEY, MENTION IT HERE.)

A preliminary design of an improved testing facility for evaluating the electromagnetic

susceptibility of weapon systems and electronic equipment is presented. This facility

features a combination of the transverse electromagnetic (TEM) cell for low-frequency

testing and the reverberating chamber for high-frequency operation. As a system, a

coverage of the wide spectrum from 10 kHz to 18 GHz or even to 40 GHz is possible. The

TEM/ reverberating combination is designed for an input impedance of 50, 75, or 100 £7 to generate a cw electric field up to 200 V/m, or a pulsed electric field up to 50 kV/m

with an approximate rise time of 10 ns. The average field for the reverberating mode

of operation is described in a statistical sense. Theoretical characteristics for a case study, to meet a given set of requirements, are given.

12. KEY WORDS (6 TO 12 ENTRIES; ALPHABETICAL ORDER; CAPITAUZE ONLY PROPER NAMES; AND SEPARATE KEY WORDS BY SEMICOLONS)

EMC test; reverberating chamber; TEM cell; susceptibility.

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