•

,

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NBSIR 82-1662

PLANNING GUIDANCE FOR FUTURE EMI

MEASUREMENT INSTRUMENTATION

M. G. Arthur

R. D. Orr

G. R. Reeve

National Bureau of Standards

U.S. Department of Commerce

Boulder, Colorado 80303

April 1982

NBSIR 82-1662

PLANNING GUIDANCE FOR FUTURE EMI

MEASUREMENT INSTRUMENTATION

M. G. Arthur

R. D. Orr

G. R. Reeve

Electromagnetic Fields Division

National Engineering Laboratory

National Bureau of Standards

U.S. Department of Commerce

Boulder, Colorado 80303

April 1982

Sponsored by

U.S. Army Communications Electronics

Engineering Installation Agency

Fort Huachuca, Arizona 85613

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

CONTENTS

Page

1. INTRODUCTION 1

1.1 Background 1 1.2 Problem Statement 1 1.3 Purpose 2

1.4 Limitations 3

2. EMI MEASURANDS 3

2.1 Introduction 3

2.2 Circuit Quantities, Time Domain 6

2.3 Circuit Quantities, Frequency Domain 9

2.4 Field Quantities, Time Domain 11

2.5 Field Quantities, Frequency Domain 13

2.6 Generalized Approach 15

3. MEASUREMENT PRINCIPLES 16

3.1 Background 16

3.2 Basic Techniques, Circuit Quantities 18

3.3 Basic Techniques, Field Quantities 25

3.4 General Evaluation of Present Measurement Techniques 27

4. MEASUREMENT REQUIREMENTS.. 29

4.1 Introduction 29

4.2 General Summary of Findings 35

4.3 Specific New Requirements 36

5. NEW INSTRUMENTATION OPPORTUNITIES 47

5.1 Introduction 47

5.2 Instantaneous Frequency Measurement Receivers 47

5.3 VLSI and VHSIC 48

5.4 Fiber Optics 49

5.5 Magnetic Bubble Memories 49

5.6 Time Domain Metrology 50

6. CONCLUSIONS 50

6.1 Purpose 50

6.2 Specific 'EMEO Tasking 51

6.3 Impact of New Requirements 51

6.4 Impact of New Technological Advances

on EMEO Measurement Techniques and Equipment 53

6.5 Observations 54

6.6 Driving Forces in the Marketplace 54

iii

Planning Guidance for Future EMI Measurement Instrumentation

M. G. Arthur, R. D. Orr, and G. R. Reeve

Electromagnetic Fields Division

National Bureau of Standards

Boulder, Colorado 80303

The environment in which electronic apparatus of all types

must function is becoming increasingly hostile because of a burgeoning electronic technology. This increases the potential

for electromagnetic interference (EMI), and places new demands

upon those organizations who are responsible for measuring EMI.

This report (a) reviews the electrical quantities that are used to

describe and evaluate EMI, (b) discusses current EMI measurement

principles, (c) attempts to identify future EMI measurement

requirements for the post 1985-1990 time period, (d) identifies

certain expected new instrumentation opportunities, and (e)

suggests action to meet the future needs for measurement

instrumentation.

Key words: electromagnetic interference; electromagnetic

environment; EMI instrumentation; EMI measurments; future EMI

requirements; planning guidance.
.
1.

INTRODUCTION

1.1 Background

The Electromagnetic Engineering Office (EMEO) USACEEIA, Fort Huachuca,

Arizona, has asked the Electromagnetic Fields Division, National Bureau of

Standards (NBS), Boulder, Colorado, to study the future prospects of

electromagnetic interference (EMI), and provide planning guidance to EMEO for

measurement instrumentation that will help them meet their mission tasks in

the post 1985-1990 time period. The study was to be focused upon the

anticipated character of EMI in the future electromagnetic environment, and

upon the instrument specifications that will provide EMEO with the needed

measurement capability to solve both the new and continuing electromagnetic

compatibility (EMC) problems. Emphasis was to be placed upon new technologies

that offer new approaches to instrument design that improve upon presently

available equipment.

1.2 Problem Statement

One of the tasks of the EMEO is to perform certain el ectromagneti

c

interference (EMI) measurements that require the use of manportable electronic

equipment. Although EMEO has other tasks and capabilities, this planning

guidance addresses only those requiring manportable equipment.

The principal types of EMI measurements for which capabilities are required are the following:

1. Spectrum occupancy

2. Path loss

3. Ambient noise

4. Electromagnetic pulse hazards

( 5. General EMC "trouble shooting."

The manportable equipment that EMEO currently has in their inventory to

make these measurements is inadequate in several ways:
1. It is heavy and bulky. This makes it difficult to transport,

assemble, and disassemble by only a few men; many men are required.

2. It requires manual adjustment of operating controls, and much

manual processing of measurement data. Very little automation or built-in

processing is employed.

3. It is designed for laboratory or wel 1 -shel tered environments. It

is not designed for adverse field conditions.

4. The ranges of measurement parameters are insufficient for some present requi rements, and future requirements will be even less adequately

met

Items 1 and 2 above cause the use of this equipment to be very manpower

intensive. More men are required than if it were lighter, smaller, more automated, and simpler to operate. One result is that measurement missions

are very expensive, especially when they require air transportation to remote

regions of the world. Also, reaction time is slower, and the time required to

gather data is longer, adding to the cost. Furthermore, insufficient data is

sometimes taken because of the slowness with which it can be gathered and

processed. Item 3 results in poor performance reliability, and creates the

need for spares that aggravates the transportation and cost problems. Item 4

also results in insufficient data, and makes it impossible to adequately

survey or evaluate the EMC conditions in a given field situation.

1.3 Purpose

The purpose of this report is to provide planning guidance to EMEO so that they may prepare themselves to meet their EMI measurement requirements in

the post 1985-1990 time period. To do this, we have endeavored to:

a. Identify the relevant EMI quantities to be measured by EMEO.

b. Review the adequacies and inadequacies of presently-used EMI

measurement techniques and instruments.

2
c. Review the anticipated measurement requirements that will exist in

the post 1985-1990 time period.

d. Review the present and anticipated new measurement technologies

that can be employed to meet EMEO's mission requirements.

e. Recommend technical solutions and a possible course of action that

will help EMEO meet its future mission requirements.

1.4 Limitations

This report is limited to those topics which EMEO personnel, in

conversations with NBS personnel, have identified as being relevant to their

mission. It is not intended as a comprehensive review or assessment of the

larger field of EMI metrology, nor does it address the measurement

requirements of agencies, either civilian or military, other than EMEO.

The EMI ineasurands discussed in section 2 are only a sub-set of a somewhat larger group of EMI measurands. Furthermore, these discussions,

along with the discussions in section 3, are slanted in directions that relate

to the particular ways which EMEO normally encounters those quantities.

The recommendations in section 6 are based upon the findings reported in

sections 4 and 5. Those findings are the result of a modest and limited

search for information, and are not to be considered to be exhaustive.

However, we believe they are representative, and any further search is

unlikely to significantly alter the picture that has been assembled here.

2. EMI MEASURANDS

2.1 Introduction

A measurand is a physical or electrical quantity, property, or condition

that is to be measured (IEEE Std. 100-1977, p. 410). EMI measurands depict

properties of interference waveforms that are needed by the EMC engineer to

solve compatibility problems. They fall into two broad categories, each of

3
which is further divided into two additional categories (see figure 1). The

first two categories are (1) circuit quantities and (2) field quantities.

Circuit Quantities Field Quantities

Figure 1. Categories of EMI Measurands

The second two categories are (3) time domain quantities and (4) frequency

domain quantities. The first two categories are related through some sort of

transducer transfer characteristic such as antenna factor or coupling

coefficient (see figure 2). The relationship between the second two

categories is expressed by a suitable mathematical transform pair, most

commonly the Fourier transform and its inverse.

Antenna Factor ^

Coupling Coefficient

^

Fourier Transform ^

2. Relationships between quantities

Table 1 is a list of the basic measurands and their basic electrical

units that are in common use by EMC engineers. In practice, the units are often modified by scaling factors; for example, volts per meter per hertz

becomes microvolts per meter per megahertz. Also, engineers commonly express

certain of the quantities as a decibel ratio relative to a reference value;

for example, microvolts per meter per megahertz becomes decibels above one microvolt per meter per megahertz, abbreviated dByV/mHz.

Circuit

Quantities

Time

Domai

n

Figure

Field

Quantities

Frequency

Domai

n

4
Table 1. EMI Measurands and Units

I.

II.

Circuit Quantities

A. Time Domain

Measurand Units

a. Amplitude

b. Power

volts, amperes

watts

B. Frequency Domain

Measurand Units

a. Frequency

b. Bandwidth

c. Spectrum amplitude

d. Power density

hertz

hertz

volts per hertz

watts per hertz

Field Quantities

A. Time Domain

Measurand Uni ts

a. Field strength

b. Power flux density

c. Energy density

volts per meter;

amperes per meter

watts per square meter

joules per cubic meter

B. Frequency Domain

Measurand Units

a. Frequency hertz

b. Bandwidth hertz

c. Broadband field strength volts per meter per hertz

amperes per meter per hertz

d. Broadband power flux density watts per square meter

per hertz

5
2.2 Circuit Quantities, Time Domain

2.2.1 Amplitude

The amplitude of an arbitrary electrical waveform in the time domain is

subject to a variety of definitions. These are discussed below.

Technically, the single term amplitude applies only to a sinusoidal

waveform. For a sinusoidal voltage waveform, v

s (t), where

v

s

( t ) = Vsin (2nft + <}>)

,

( 1 )

the various quantities are defined as follows:

v

$ (t) = instantaneous voltage at time t

V = amplitude

f = frequency

= phase angle at t = 0.

By the addition of modifiers, other amplitudes are defined that apply to both

sinusoidal and non-si nusoi dal periodic waveforms, v

p (t). These are:

a. Instantaneous amplitude , v^(t): the voltage value of a waveform at

any specified time instant.

b. Average amplitude , vavg

:

where T = period.

T

f v (t) dt,

J o p

v ' * ( 2 )

6
c. RMS amplitude , v pms

:

v = [ 4 / v 2( t )dt]

1/2 . (3) rms

L T J o p

v J v '

Note that the rms and average amplitudes are defined in terms of one full

period, T, and do not vary with time.

d. Peak amplitude, V„: the maximum (positive or negative)

r instantaneous amplitude that occurs in an observation time interval.

e. Quasi -peak amplitude , V q

: the output voltage from a rectifier

network that has specified charge and discharge time constants. (See the

appropriate ANSI and CISPR standards for the values of these constants.)

Note that the peak and quasi -peak amplitudes may depend upon the observation

time interval.

For a sinusoidal waveform, the average amplitude is zero by the above

definition. Therefore it is redefined to be the average over T/2, in which case it is 0.6366 V. The rms amplitude is 0.7071 V. The peak amplitude is

synonymous with its simple amplitude, V. The quasi-peak amplitude may vary

with frequency and observation time.

If the voltage waveform is not periodic, only the following amplitude

definitions strictly apply:

a. Instantaneous amplitude

b. Peak amplitude

c. Quasi -peak amplitude

Average and rms amplitudes are not defined for non-periodic waveforms because

they may vary with the observation (integration) time interval. However, an electrical instrument that is designed to measure the true rms and true

average amplitudes of an arbitrary periodic waveform may give useful

7
information about non-periodic waveforms, at least for the duration of the

measurement time interval.

If the waveform is a current instead of a voltage as used in the above

discussion, the same definitions apply with current replacing voltage. EMI

instruments are more commonly designed to measure voltage amplitude than

current amplitude. The discussions in this report use voltage amplitude for

illustration purposes only.

2.2.2 Power

The power of an arbitrary electrical waveform in the time domain is also

subject to a variety of definitions. In general, power is the time rate of

transferring or transforming energy (IEEE Std. 100-1977, p. 510). Of the

various specific types of power, the following are of principal value to the

EMC engineer:

a. Instantaneous real power , P^(t): the power dissipated in a resistive termination at any specified time instant.

b. Average real power , P av g^

1 T

P = -f- f P. (t) dt, (4)

avg T J o w ' ’ v '

where T is the period over which the power is averaged.

c. Peak real power , Pp : the maximum instantaneous real power that occurs in an observation time interval.

d. Available power , P av ]

: the maximum average real power that can be

transferred from a port to a termination which is adjusted for this condition.

Note 1. These definitions deal with real power as distinct from reactive

power, which is normally of little interest to the EMC engineer as a circuit

measurand.

8
Note 2. These definitions apply to any arbitrary waveform. However, if

the waveform is non-stationary, average real power may vary with the

observation time interval.

The frequency of a periodic waveform is the number of periods per unit

time. For a non-sinusoidal periodic waveform, frequency refers to its

fundamental component, unless otherwise stated. For a non-periodic waveform,

frequency refers to the sinusoidal components into which the waveform may be

analyzed.

As an EMI measurand, bandwidth refers to signal bandwidth. It is the

least frequency interval outside of which the power spectrum of the

time-varying quantity is everywhere less than some specified fraction of its

value at a reference frequency (IEEE Std. 100-1977, p. 52). Unless otherwise

stated, the reference frequency is that at which the spectrum has its maximum

val ue.

Mathematically, spectrum amplitude, S(f), is twice the magnitude of the

Fourier transform, V(f), of an arbitrary time-domain waveform, v(t). That is.

2.3 Circuit Quantities, Frequency Domain

2.3.1 Frequency

2.3.2 Bandwidth

2.3.3 Spectrum Amplitude

S(f) = 2 | V(f ) |

,

(5)

where

V(f) = / v(t)e'j2nft

dt. ( 6 )

9
Conceptually, spectrum amplitude is the value of the spectrum of a signal at

any specified frequency.

There is a dualism between instantaneous amplitude (in the time domain)

and spectrum amplitude (in the frequency domain). The distribution of

instantaneous amplitudes of a signal in the time domain is called its

(amplitude) waveform . The distribution of spectrum amplitudes of a signal In

the frequency domain is called its (amplitude) spectrum . Thus, instantaneous

amplitude, v^t), and spectrum amplitude, S(f), are equivalent quantities for

describing the amplitude of a signal. However, note that because of the

transformation defined by eq. (6), spectrum amplitude has (for example) the

units of volt-seconds or volts per hertz in contrast to the units of

instantaneous amplitude which is simply volts .

By definition, spectrum amplitude does not vary with time (see eqs. (5)

and (6)). However, because of the finite time required to measure spectrum

amplitude, its measured value may vary with time, particularly for

non-periodic or very long-period waveforms.

Mathematically, the frequency domain power density (power per unit

bandwidth), P(f), of a waveform, v(t), is defined from the energy density,

E(f). The total energy, E^, in joules, is given by the equations

where S(f) is the spectrum amplitude of v(t), and R is the circuit

resistance. The energy density (energy per unit bandwidth), E(f), is given by

the equation

2.3.4 Power Density

/ v

2 (t)dt = -i-

/ IS(f)l 2 df,

— 00 —00 (7)

( 8 )

10
where the integration of eq. (7) is over a one-hertz bandwidth at frequency

f. Power density is given by the equation

_ E(f) _ |S(f)| 2 K 1 T

1

AT RAT » (9)

where AT is the time interval during which the energy is transferred or transformed.

Conceptually, power density is the power in the spectrum of a signal at

any specified frequency. It has the dimensional units of watts per hertz.

2.4 Field Quantities, Time Domain

2.4.1 Field Strength

Field strength is the magnitude of the electric (or magnetic) field

vector of an electromagnetic field at a point in space.

The dimensional units of field strength are volts per meter or amperes

per meter. The discussion of amplitude in section 2.2.1 above applies also to

field strength.

2.4.2 Power Flux Density

The power flux density, P, of an electromagnetic field is the value of

the Poynting vector at a point in space. It is the rate of energy flow per

unit area at the point. For a plane wave in free space, P is given by the

equation

P = t X fi ( 10 )

11
where

E = electric field strength

H = magnetic field strength.

P, E, and H are vector quantities, and P is the cross product of E and H.

For a sinusoidal field, the instantaneous power flux density, P^, is

given by the equation

e o

1/2 Pi = (7^) £

0

2 sin2 (u/t - <(>) (11)

M o

where

E Q = amplitude of the electric field

e 0

= permittivity of free space

y 0

= permeability of free space.

The average power flux density, P av g> is

P avg

= V2(^)

VV ( 12 )

and the peak power flux density, Pp, is

l/2 Ox <- Pn = (—) E 2 = (-^) H 2, Ox

1/2

P has the dimensional units of watts per square meter.

(13)

12

|
2.4.3 Energy Density

The energy density, W, at a point in an electromagnetic field is the sum

of the electric energy density and magnetic energy density. For a plane wave

in free space, W is given by the equations

w - \ e

0

E2 + 1/2 U 0H2

= E E2 = „ H2

0 0

The dimensional units of W are joules per cubic meter,

(14)

For a non-planar wave, and for fields in an inhomogeneous lossy

dielectric medium, the energy density may be difficult to calculate or measure.

2.5 Field Quantities, Frequency Domain

2.5.1 Frequency

The frequency of a periodic waveform is the number of periods per unit

time. For a non-sinusoidal periodic waveform, frequency refers to its

fundamental component, unless otherwise stated. For a non-periodic waveform,

frequency refers to the sinusoidal components into which the waveform may be

analyzed.

2.5.2 Bandwidth

As an EMI measurand, bandwidth refers to signal bandwidth. It is the

least frequency interval outside of which the power spectrum of the

time-varying quantity is everywhere less than some specified fraction of its

value at a reference frequency (IEEE Std. 100-1977, p. 52). Unless otherwise

stated, the reference frequency is that at which the spectrum has its maximum

val ue.

13
2.5.3 Broadband Field Strength

Mathematically, broadband field strength is twice the magnitude of the

Fourier transform of the electric or magnetic field vector of an electromagnetic field at a point in space. Conceptually, it is the value of

the spectrum of the field strength of a signal at any specified frequency.

The dimensional units of broadband field strength are volts per meter per

hertz.

The discussion in section 2.3.3 about the dualism between instantaneous

amplitude (in this case, field strength) and spectrum amplitude (in this case,

broadband field strength) also applies here.

2.5.4 Broadband Power Flux Density

Mathematically, the frequency domain power flux density (power per unit

area per unit bandwidth), P(f), is defined from the frequency domain energy

density, W(f). The total energy density, W

t

, in joules per square meter, is

giver, by the equations

e 1/2 00 e n V2 w

t

= (-/) / e2(t)dt = (7^) / |E(f) I 2 df (15)

u yO -00 U0

where e(t) is the electric-field strength and E(f) is the Fourier transform of

e(t). The energy density per unit bandwidth, W(f), is given by the equation

e o

1/2 w(f ) = (—) |E(f)|2 (16)

where the integration of eq. (15) is over a one-hertz bandwidth at frequency

f. Power density is given by the equation

14
pm ( 17 ) _ wjLt). (l°)

/z

l E ( f )l 2 nT) " at "

y Q

AT

where aT is the time interval during which the energy is transferred or

transformed.

Conceptually, broadband power flux density is the power per unit area in

the spectrum of a signal at any specified frequency. It has the dimensional

units of watts per square meter per hertz.

2.6 Generalized Approach

There has been an increased recognition of the need for a statistical

approach to the solutions of many electromagnetic inteference problems. This

trend reflects the realization that the noise source and the environment are

often best described in statistical terms.

Basically, the electromagnetic interference problems may be considered to

consist of three major parts: namely, the source, the environment, and the

receiver. A recent approach is to characterize each of these three parts in

terms of the so-called mutual coherence function. For example, the noise

source may be described by the correlation function in time and space or in

terms of the temporal and angular spectra.

Similarly, the electromagnetic environment from source to the observation

point may be characterized by a general time-varying and dispersive transfer

function. Then the correlation function for the received signal may be

expressed in terms of these coherence function and the specific receiver

characteri sties.

15
Furthermore, the field strength appearing at a given point in space and

time can also be expressed as a sum of the coherent (average) field strength

and the incoherent (fluctuating) field strength. The average field may be

obtained by measuring the average in-phase and quadrature components of the

field. The variance of the fluctuation yields a measure of the incoherent

field. Theoretical models for calculating these component fields are also

possible.

Detailed studies of time, space, frequency and angular characteri sties of

the mutual coherence functions and of the component fields should give a good

picture of the electromagnetic interference problem.

3. MEASUREMENT PRINCIPLES

3.1 Background

Historically, the two basic instruments for measuring electromagnetic

interference have been the field intensity meter (FIM) and the spectrum

analyzer (SA). They are augmented by a variety of antennas, probes, couplers,

recorders, printers, and controllers to perform a wide range of measurements.

Both the FIM and SA are two-port devices that respond to an

electromagnetic signal and deliver certain information about the signal in one

form or another. The basic distinction between the two is that the FIM is

considered to be an instrument that processes information in the time domain,

whereas the SA is considered to process information in the frequency domain.

Actually, both instruments function in the time domain only, but the SA is

arranged to analyze the time domain information in terms of its spectral

equivalent representation.

16
Functionally, both the FIM and SA are "radio receivers" in that they (1)

"receive" an electromagnetic signal either from a circuit by direct connection

or from a field by inductive/capacitive coupling, (2) process a replica of the

signal through various filters, amplifiers, limiters, rectifiers, etc., and

(3) deliver one (or more) output signal (s) to a transducer such as a

voltmeter, loudspeaker, CRT, pen recorder, tape recorder, etc., which either

displays it in real time, stores it for later use, or processes it further

into still other forms. In fact, the early FIM's were closely similar to the

communications receivers of their day.

Operationally, the essential difference between the FIM and the SA has

been (1) in the method used to tune the instrument to the desired reception

frequency, and (2) in the display format which the output transducer

employs. Historically, FIM's were tuned manually by the operator, whereas

SA's were electronically tuned; the output format for FIM's was a quantity

that ran in real time, whereas for SA's the quantity was expressed as a

function of reception frequency. Modern methods of tuning and control have

largely removed the first distinction, and the second distinction has become

irrelevant as FIM's are fitted with X-Y plotters whose X-axis is related to

reception frequency, and SA's can be operated in an osci 1 loscopic mode.

The purpose of this background review is to point out that the FIM and

the SA represent two essentially different approaches to signal measurement

and analysis, but through the use of modern technology they have both evolved

to the point where either instrument can be used to obtain both time domain

and frequency domain information about the signal.

In addition to the FIM and SA, a third approach is widely used in which

the signal is processed by a wideband or untuned instrument. This has the

17
advantage of operating simplicity, but may sacrifice sensitivity and

measurement accuracy.

3.2 Basic Techniques, Circuit Quantities

3.2.1 Amplitude

When an FIM or an SA is used to measure amplitude, it is operating as a

narrowband tuned voltmeter. To measure voltage amplitude in a circuit, the

instrument is connected through a suitable cable and voltage probe to the

point at which the voltage is to be measured. The ordinary principles of

voltage measurement apply. To measure current amplitude, the instrument still

operates as a tuned voltmeter, and the current being measured is converted to

a voltage either by the use of a transducer such as a current probe or by

passing it through a calibrated resistor. Again, the ordinary principles of

current measurement apply.

The five types of amplitude discussed in section 2.2.1 are measured as

fol 1 ows

a. Instantaneous amplitude : This cannot be measured with an FIM or SA

because these instruments do not respond rapidly enough to radiofrequency

waveforms. Instead, an oscilloscope must be used.

b. Average amplitude : This is measured by designing the detector

network in the FIM or SA in one of three ways. One is to use a linear

rectifier circuit in which the component values are selected to produce a dc

voltage that is proportional (or equal) to the average value of a sinusoidal

voltage. A second way is to use a square-law rectifier circuit, again

18
selecting component values to produce a dc voltage proportional to the average

value of a sinusoidal voltage. The third method is to sample the voltage

waveform and compute the average value by means of a programmed electronic

computer built into the FIM or SA.

The first two methods give accurate results for sinusoidal voltages, but

may not be accurate for non-si nusoi dal waveforms. The third method gives the

best accuracy for arbitrary waveforms as long as the sampling rate is fast

enough to provide a faithful representation of the waveform to the electronic

computer.

c. RMS amplitude : This is measured by designing the detector network

in one of the three ways discussed in b above except that the component values

and the computer program are selected to produce an output voltage that is

proportional to the rms amplitude of the waveform. A linear rectifier will

give accurate results only for sinusoidal voltages. The square-law rectifier

and the sampling technique will give accurate results for arbitrary waveforms

that fall within the amplitude and frequency ranges over which these

characteristics hold.

d. Peak amplitude : This is measured by designing the detector network

to have a short (e.g., a few microseconds) charge time constant and a very

long (e.g., many seconds) discharge time constant. Alternatively, an

oscilloscope with a very long persistence phosphor CRT may be used.

e. Quasi -peak amplitude : This is measured by designing the detector

network to have a specified charge time constant and a specified discharge

time constant. These time constants differ between American standards (ANSI)

19
and European standards (CISPR), and also vary with frequency range. Refer to

those standards for specific values.

Insofar as the F IM and SA are narrowband tuned voltmeters, their

predetection voltage waveform, r(t), is the result of frequency filtering.

Mathematically, this instantaneous waveform is the convolution of the input

voltage waveform, v^t), and the impulse response function, h(t), of the

cascade of networks preceding the detector. See eq. (18).

r(t) = Vi (t) * h(t) (18)

Thus, the detector output is proportional to the amplitude (average, rms,

etc., whichever) of the filtered waveform, which is not necessarily the same

as the input waveform to the FIM or SA. If the bandwidth of the input

waveform is small (narrowband signal) compared with that of the predetection

circuit bandwidth, the predetection waveform will be essentially the same as

the input waveform and the detector output will represent the total input

waveform. However, if the input waveform bandwidth is large (broadband

signal) compared with the predetection bandwidth, the predetection waveform

will differ from the input waveform and the detector output will represent

only a part of the input waveform; specifically, that part that lies in the

bandpass of the tuned circuits. Thus, the resulting measured value of

amplitude depends upon the relative bandwidths of the input waveform and the

predetection filters. For a sinusoidal input waveform, this bandwidth effect

does not produce a measurement error; for non-sinusoidal wideband signals

20
(noise. Impulsive, modulated, etc.), an error may occur If the bandwidth

factor Is not taken Into account.

In the spectrum analyzer, tuning over a range of frequencies Is achieved

rapidly and repeatedly (If desired), and the output display has the form of

voltage (or current) amplitude as a function of frequency. The trace is,

point-by-point, the amplitude of the predetection filtered waveform which,

except for a sinusoidal waveform, has a certain bandwidth and therefore is

subject to the variations cited in the previous paragraph. It is necessary to

select the correct combination of SA bandwidth and tuning (sweep) rate in

order to get an accurate measure of waveform amplitude.

A word of caution is needed concerning the SA output display. Although

the output appears to be in terms of amplitude as a function of frequency, it

is not a frequency-domain display in the sense of the spectrum amplitude

discussed in section 2.3.3 The dimensional unit of the SA output is volts (or

amperes), whereas the dimensional units of spectrum amplitude are volt-seconds

or volts per hertz. The former quantity is analogous to the Fourier

components of a periodic waveform; the latter quantity requires the infinite

summation ( i . e . , integration; see eq. (6)) of the product of v^t) and an

eternal exponential function of time. If the measured waveform is periodic,

the shape of the SA output display function and the shape of the spectrum

amplitude function are closely similar. But they represent distinctly

different quantities. To repeat, the SA output display is a time-domain

measurement, but arranged to show this quantity (amplitude) as a function of

the frequency to which the SA is tuned.

21
The technique for measuring spectrum amplitude, a frequency-domain

measurement, involves the fast Fourier transform (FFT) and is discussed in

section 3.2.4.

In order to prevent the distortion of input waveform by predetection

filtering and its accompanying effects on the measured amplitude, a very

broadband (untuned) voltmeter is used. Because of its smaller sensitivity,

such a technique is used principally when the waveform amplitude is large

(e.g., high-level and/or hazard-level signals).

3.2.2 Power

The power transferred by a waveform is not normally measured directly;

that is, an electromagnetic wattmeter is not used. Instead, it is computed

from data obtained from the measurement of waveform amplitude and circuit

impedance. Amplitude is measured by the techniques discussed in section

3.2.1.; impedance is measured by conventional techniques. Power is computed

by well-established formulas. In some instances, the scale on the output

meter of an amplitude-measuring instrument is calibrated in units of power, in

which case a specific circuit impedance is assumed (e.g., 50 ohms).

3.2.3 Frequency and Bandwidth

The frequency and bandwidth of a waveform are measured with either an FIM

or an SA which are used as a calibrated frequency meter. The individual

sinusoidal components of a complex periodic waveform are measured using narrow

bandpass filter networks in the FIM or SA for best resolution. Nonperiodic

22
random waveforms and very broadband waveforms (e.g., pulse trains, etc.) are

best measured with an SA. Bandwidth is usually specified in terms of the

half-power (-3 dB) frequencies of the waveform's spectrum.

3.2.4 Spectrum Amplitude

Spectrum amplitude is measured in either of two ways. The first is more

suited to field conditions, whereas the second is normally limited to the

laboratory because of the instruments required.

The first technique uses the FIM or SA as a transfer standard. A test

signal whose spectrum amplitude is known is used to calibrate the FIM or SA.

The test signal waveform is a pulse train in which the width of each pulse is

very short, e.g., 10 ns or less. The repetition rate varies from 60 pps to

over 1 Mpps, depending upon the design of the generator. For very short pulse

widths (<0.5 ns), the spectrum amplitude is constant with frequency to within

±5 dB from dc to over 1 GHz.

In this technique, the assumption is made that the response of the FIM or

SA to arbitrary broadband EMI waveforms is the same as their response to the

test signal. That is, if the FIM or SA measures the same (time-domain)

amplitude within a given bandwidth when two different broadband signals are

applied, then the two signals must have the same (frequency-domai n) spectrum

amplitude. Strictly speaking, the spectrum amplitude of an arbitrary waveform

depends upon its instantaneous amplitude. For example, the spectrum amplitude

of a rectangular pulse differs from that of a cosine-squared pulse of the same

amplitude and pulse width. Correspondingly, the FIM or SA response likewise

depends upon the input waveform's instantaneous amplitude. In practice, many

of the broadband EMI waveforms encountered are enough similar to the test

23
signal that this technique is useful. However, it is not highly accurate,

with typical measurement errors between 6 dB and 40 dB, depending upon

ci rcumstances

Bear in mind that, although the FIM or SA is calibrated in terms of a

frequency-domain quantity (spectrum amplitude, in units of dBpV/MHz), the

connection between the two domains, metrological ly speaking, is the assumption

stated in the previous paragraph.

The second technique for measuring spectrum amplitude is as follows:

a. The signal waveform, v(t), is recorded by sampling techniques, and

waveform data is stored in computer memory.

b. Spectrum amplitude is computed by an electronic computer using the

fast Fourier transform algorithm based on eqs. (5) and (6).

This technique is capable of high accuracy (approximately 1 dB or less),

but requires laboratory-qual i ty instrumentation.

3.2.5 Power Density

Power density (frequency domain) is not measured directly, but is

computed from spectrum amplitude and circuit impedance using eq. (9). In some

instances, the scale of the output meter of a FIM is calibrated in units of

power density (e.g., dBm/MHz), in which case a specific circuit impedance is

assumed (e.g., 50 ohms).

24
3.3 Basic Techniques, Field Quantities

3.3.1 Field Strength

Field strength is measured by transforming the electromagnetic field

energy into circuit energy by means of a suitable transducer, such as an

antenna or probe, and measuring the circuit amplitude by the techniques

discussed in section 3.2.1. The antenna or probe may be of various types:

rod antenna, dipole antenna, horn antenna, loop antenna, directional antenna

arrays of various designs, or combinations of these.

The measurement of E-field strength using a traveling-wave linear antenna

is based on the following formula:

v e(t) = kl e E(t), (19)

where

v e (t) = instantaneous voltage at antenna output port

k = antenna factor (dimensionless ratio)

l e

= effective antenna length

E(t) = E-field strength (volts per meter)

25
Factors k and 1 e

, or their product, are measured by a calibration procedure.

For other types of antennas, the coefficient of E ( t ) in eq. (19) may take a

different algebraic form, but the basic concept remains.

Similarly, H-field strength measurement is based upon the general

equation

v

h

(t) = A H(t) (20)

where H(t) is the H-field strength and A is a constant found by calibration of

the loop antenna or probe.

An FIM or SA is then used to measure the amplitude of v e (t) or v

h (t).

3.3.2 Power Flux Density

Power flux density is determined by calculation using eqs. (11), (12), or

(13). Although in principle the Poynting vector can be measured directly,

such as with a combined E-field and H-field antenna structure or a Hall-effect

device, this approach has not been developed into a practical technique.

In some instances, the scale of the output meter of an FIM is calibrated

in units of power flux density (e.g., dBm/m^). This is more commonly found on

high-level, broadband meters such as EM hazard meters.
3.3.3

Energy Density

Energy density is determined by calculation using eq. (14). As with

power flux density, practical instrumentation has not been developed to

measure energy density directly. Likewise, the output meter scale of some

FIM's has been calibrated to read in units of energy density (e.g., J/m2

).

3.3.4

Broadband Field Strength

Broadband field strength is measured by the same techniques discussed in

sections 3.2.1 and 3.2.4. 3.3.5

Broadband Power Flux Density

Broadband power flux density is measured by the same techniques discussed

in sections 3.2.2 and 3.2.4, using eq. (17) of section 2.5.4.

3.4 General Evaluation of Present Measurement Techniques

The measurement techniques discussed above have evolved during

approximately 40 years of EMI measurement experience. As new instrumentation

and measurement technology have been developed, they have been incorporated in

EMI instrumentation. But there has always been a lag between available

technology and its deployment.

Present-day commercial instrumentation represents, for the most part,

technology that was state-of-the-art in the early 1970's. Generally, it has

27
the following characteristics that become limitations in the context of this

report:

a. The equipment is not capable of instantaneous wideband operation.

It is based upon frequency-sweeping techniques that require a finite time to

gather data over a large frequency range.

b. The equipment is not capable of storing large amounts of data

within its own internal memory banks. Data is normally transferred to

accessory storage units either promptly or with a small time delay.

c. The equipment is not capable of performing complicated data

processing with its own internal computer system so as to directly provide

output information in its desired final form. Data is normally processed

outside the FIM or SA, for example, to obtain amplitude and time statistics of

EMI waveforms.

d. The equipment is not capable of directly measuring certain EMI

measurands such as involve the energy or power associated with EMI

waveforms. They must be computed from amplitude data. Phase information is

notably lacking.

e. The equipment is not capable of making accurate measurements of

frequency-domain quantities. Because by necessity we exist and operate in

real time, a transformation of some sort is required to describe the signal in

the frequency domain.

( Present techniques for implementing this transformation

produce only approximations to the whole truth.

28
f. The equipment is not capable of making entirely satisfactory

measurements of electromagnetic fields without disturbing the very fields

being probed. In many cases, this disturbance is unacceptably great; only in

a few cases have special techniques (optical fibers, high-resistance lines)

been employed to reduce this problem.

These shortcomings must be removed in order to improve upon the basic

measurement techniques that are presently available.

4. MEASUREMENT REQUIREMENTS

4.1 Introduction

To determine what measurement instrumentation will be needed in the post

1985-1990 time period requires some knowledge or forecasting of the

measurements that will be required to be made. This section contains a

summary of new requirements as determined from a survey of literature and

knowledgeable persons. In addition to new requirements, most if not all of

the present requirements will most likely continue to exist in this time

period.

Two basic sources supplied the information in this section:

(1) technical literature, and (2) knowledgeable persons. The process called

literature search was used to access printed material. Sources consulted

include the following:

1. Computer accessed data bases:

a. Science Abstracts from the Institution of Electrical Engineers

(INSPEC)

29
b. Smithsonian Science Information Exchange (SSIE)

c. National Telecommunication Information Service (NTIS)

d. Defense Documentation Center (DDC)

e. Comprehensive Di ssertati ons Index (CDI)

2. Professional journals:

a

.

Proceedings of the IEEE

b. IEEE Transactions on Aerospace and Electronic Systems

c. IEEE Transactions on Communications

d. IEEE Transactions on Computers

e. IEEE Transactions on Electron Devices

f. IEEE Transactions on Instrumentati on and Measurement

g. IEEE Transactions on Microwave Theory and Techniques

3. Technical Journals:

a. Electrical Communications

b. El ectro-Optical Systems Design

c. Electronic Design (ED)

d. Electronic Design News (EDN)

e.. Electronics Letters

f. Electronics Magazine

g. Electronic Warfare/Defense Electronics

h. IEEE Spectrum

i

.

Microwave Journal

j. Microwave System News (MSN)

k. Mi crowaves

1

.

Science

m. Science News

n. Systems (Stelsels) (So. Africa)

30
4. Special /miscellaneous publications

a. "A Forecast of Space Technology, 1980-2000", NASA

b. Advanced Space Systems Concepts and their Orbital Support Needs

(1980-2000), The Aerospace Corporation, April 1976

c. Air Force Aero Propulsion Laboratory Technology Plan, FY 77-81

d. Air Force Materials Laboratory Research and Technology Plan,

FY 77

e. Air Force Systems Command Research Planning Guide, May 1975

f. Final Acts of the World Administrative Radio Conference,

Geneva, 1979

g. International Conference on Communications (ICC) Conference

Records (recent years)

h. International EMC Symposium Records (recent years)

i. National Aerospace Electronics Conference (NAECON) Records

(recent years)

j. Newsweek Magazine

k. Technology Tomorrow

Knowledgeable persons* contacted during 1979-1980 included the following:

1. Allen W. Anderson

(Formerly, Army Spectrum Manager)

Spectrum Management Division

Office of the Assistant Chief of Staff For Automation and

Communications

Department of the Army

Washington, DC 20310)

Now retired

202-530-3643 (home)

2. W. Murray Bull is

Chief, Electron Devices Division

Center for Electronics and Electrical Engineering

National Engineering Laboratory

National Bureau of Standards

Washington, DC 20234

301-921-3786

31
3 . Jean Caffiaux

VP for Government Division

Electronic Industries Association

Washington, DC 20006

202-457-4940

4. William J. Cook

Technical Policy and Operations

Office of the Assistant Secretary of Defense for Communications,

Command, Control and Intelligence

Department of Defense

Washington, DC 20301

202-695-2844

5. Harry A. Feigleson

Director, Electromagnetic Spectrum Management

Office of Chief of Naval Operations

Department of the Navy

Washington, DC 20350

202-695-2710

6. William D. Gamble

Spectrum Plans and Policies

National Telecommunications and Information Administration

U.S. Department of Commerce

Washington, DC 20005

202-724-3301

7. James F. Garrett

Shipboard EMC Improvement Program

Naval Sea Systems Command

Department of the Navy

Washington, DC 20362

202-692-1871

8. George H. Hagn

Assistant Director, Program Development

Stanford Research Institute

SRI - Washington

Arlington, VA 22209

202-524-2053

9. Eldon S. Hughes

Chairman, EIA Committee G-46 on Aerospace EMC

Space Division

Rockwell International

Downey, CA 90241

213-594-3151

10. Christopher Kendall

Private Consultant, EMC

Running Springs, CA 92382

714-867-2540

32
11. Warren A. Kesselman

Army Communications R&D Command

Department of the Army

Fort Monmouth, NJ 07703

201-544-4703

12. Frank K. Koide

Senior Project Engineer

Rockwell International

Anaheim, CA 92803

714-632-3932

13. William S. Lambdin

General Manager

Electro-Metrics Division of Penril Corporation

Amsterdam, NY 12012

518-843-2600

14. Paul Major

Army Communications R&D Command

Department of the Army

Fort Monmouth, NJ 07703

201-544-4605

15. Tadeo Mukaihata

Manager, Primary Standards Laboratory

Hughes Aircraft Company

Culver City, CA 90230

213-391-0711, ext 7543

16. Norris N. Nahman

Chief, Time Domain Metrology Group

Electromagnetic Technology Division

Center for Electronic and Electrical Engineering

National Engineering Laboratory

National Bureau of Standards

Boulder, CO 80303

303-497-3806

17. Leray Olson

Manager, Product Applications Engineering

CEI Division

Watkins-Johnson Company

Gaithersburg, MD 20760

301-948-7550

18. John Osborne

Director of Engineering

Don White Consultants, Inc.

Gainesville, VA 22065

703-347-0030

33
19. Robert J. Phelan

Optical Electronic Metrology Group

Electromagnetic Technology Division

Center for Electronics and Electrical Engineering

National Engineering Laboratory

Boulder, CO 80303

302-

497-3696

20. Paul J. Phillips

Spectrum Management

Office of the Assistant Chief of Staff for Automation and

Communications

Department of the Army

Washington, DC 20310

202-695-3533

21. Robert C. Powers

Technical Planning Staff

Office of Chief Scientist

Federal Communications Commission

Washington, DC 20554

202-632-7060

22. Robert P. Rafuse

Senior Staff Member

MIT Lincoln Laboratory

Lexington, MA 02173

617-862-5500, ext 5877

23. Jerry Rothhammer

Manager, Product Line Sales

AILTECH

Los Angeles, CA 90066

213-822-3061

24. Theodore S. Saad

President

Sage Laboratories , Inc.

Natick, MA 01760

617-653-0844

25. Richard B. Schulz

Editor, IEEE Transactions on Electromagnetic Compatibility

Electromagnetic Compatibility Analysis Center

ITT Research Institute

Annapolis, MD 21402

301-267-2258

26. Arthur D. Spaulding

Spectrum Utilization Division

Institute for Telecommunications Sciences

Department of Commerce

Boulder, CO 80303

303-

497-5201

34
27. Larry Toller

Applications Engineer

AILTECH

Los Angeles, CA 90066

213-822-3061

28. Charles E. White

Editor, Telecommunications Magazine

Horizon House Publishing Company

Dedham, MA 02026

617-326-8220

29. Donald R.J. White

President

Don White Consultants, Inc.

Gainesville, VA 22065

703-347-0030

30. Major J. Wiggen

Frequency Management Office

Air Force Systems Command

Andrews Air Force Base

Washington, DC 20334

202-981-4673

31. John Williams

Spectrum Allocation Division

Federal Comuni cations Commission

Washington, DC 20554

202-632-6350

4.2 General Summary of Findings

The picture that has emerged from the information gathering task is the

fol 1 owi ng

The future EMI problems are not going to be of a different basic type

than those at present. The post 1985-1990 era will be characterized by

technological evolution rather than revolution. No radically new breakthroughs will occur that will significantly alter what we know at the

present time.

Future EMI problems will be different in magnitude and scope, however,

because of:

a. The prol iferation of electronic devices in every facet of our society.

35
b. Increased ease with which super-high power levels can be generated,

particularly at microwave and millimeter wave frequencies.

c. Increased speed of digital electronics, going into the

gigabit/second range.

d. Wider use of geostationary satellites for varieties of

appl i cations.

e. Employment of spread-spectrum methods of communication and target

detection, using new formats such as Walsh or other nonorthogonal functions.

f. Decreased integrated circuit size, resulting in increased circuit

density, reduced operating and breakdown voltages, and faster operating speeds

(greater bandwidths).

Metrological ly, these factors will require the following new capabilities

in EMI instrumentation:

a. Smaller size, weight, and power demands so as to make it easier and

less costly to respond to an increasing demand for measurements.

b. Dynamic measurement ranges from at least -130 dBm to over +30 dBm.

c. Frequency coverage to 140 GHz or higher.

d. Measurement bandwidths to 1 GHz or greater.

e. Instantaneous frequency measurement capability covering large

sections of the spectrum.

4.3 Specific New Requirements

In this section we discuss the new systems and those trends in present

systems that our literature searches and personal interviews indicated as likely causes of EMI through the years 1985-2000. Classified systems of the

future have not been included in this document.

36
4.3.1 Packet Radio

First a few words of introduction about packet switching, a technique

developed for rapid and efficient communication throughout a hard-wired

computer network. Digital data is sent from one network point (a computer,

terminal, data bank, etc.) to another in packets containing up to several

thousand bits. As the packet traverses the network, mi croprocessors at

successive intersections receive information on network traffic. Dispatching

circuits at each intersection read the packet's destination code and send the

packet, link by link throughout the network, over the shortest-time route.

Packet radio (PR) is a wireless form of a packet switching network. That

is, packets of computer data are broadcast from point to point on their

journey through the network. There are some experimental PR systems, though

transceiver cost will not be low enough for a practical system until the mid1980's. Then PR should become increasingly competitive with (and ultimately

more economical than) hard-wired systems for distributing low to moderate

volumes of local computer data traffic.

The primary use of PR will be for computer data transmission according to

the needs of users wishing to access data bases, manipulate files, run programs, or write and execute programs on remote computers. While the high

throughput and low delay of hard-wired computer networks are maintained, a significant new aspect of a PR network is its accessibi 1 ity to users at mobile

terminals. An individual PR may serve as a repeater, or the portal between

the network and a user, or it may broadcast information from a control

station. This station uses a packet's routing and control information to

decide the shortest-time route to the packet's destination.

A practical packet radio should have a frequency within the range from

300 MHz - 30 GHz. Above this, absorptive and scattering losses attenuate the

signals. Below 300 MHz, multipath reception produces time discrepancies of

milliseconds which limit the signal data rate. An experimental PR network in

the San Francisco area operates within a band from 1710-1850 MHz.

37
The bandwidths of a PR network will depend in part on whether or not the

system uses spread-spectrum transmi ssi ons. Without spread-spectrum, the data

rate of a system will determine the bandwidth. The data rate in turn is

arrived at from the number of bits per packet and the number of packets that

can be sent each second. A system sending 2000-bit packets with a transit

delay of 0.1 second from source to destination will have a data rate of

several hundred kilobits per second, and thus a least bandwidth of several

hundred kilohertz. In practice, this system would have a bandwidth of a few

megahertz. As in a hard-wired packet switching network, each packet tells

each PR transceiver to set its bandwidth to accommodate the transmission of

that packet over the next link of the network. Successive packets may require

different bandwidths.

The various types of spread-spectrum systems may have bandwidths ranging

from tens to hundreds of megahertz. In the previous system operating from

1710-1850 MHz, the center frequency of successive packets takes predetermined

hops within the 140 MHz range. 8y this technique, called "frequency hopping",

the bandwidth of the system becomes, in effect, the entire 140 Mhz.

4.3.2 Spread-Spectrum Systems

A spread-spectrum system is a means for distributing the power spectrum

of a signal over a much broader frequency range than that of the original

signal. The extremely large bandwidths of some spread-spectrum techniques

provide communications and data transmi ssions with multiple access, greater

security, and high resistance to jamming.

A hybrid spread-spectrum and time-di vis.ion-multiple-access (TOMA) system

is employed by the military services in their Joint Tactical Information

Distribution System (JTIDS), intended to become the major tactical

communications network sometime during the 1980's. The system will have

thousands of users and comprise transceivers on aircraft, ships, vehicles,

inanpacks, and perhaps smaller missiles. No communications center will be

needed because all users will talk to all others on a common channel.

Some other military uses for spread-spectrum techniques are in satellite

communications (tens of gigahertz), ai r-to-ground data links (12-18 GHz band).

38
packet radio (mobile communications in mid- to upper-UHF), and a Position

Location Reporting System (low UHF). The high anti-jamming and interference

rejection capability of spread-spectrum systems also make them attractive for

commercial and space versions of these military applications.

Spread-spectrum radars will appear during the next 10 years. They will

operate at lower power than present radars because they will share spectrum

space with telecommunications systems.

The bandwidth of a spread-spectrum system may be so large (e.g., 50 kHz

expanded to 40 MHz) that the signal power density is below atmospheric noise

and can be extracted only with sophisticated detectors and a knowledge of the

modulation code. Such low signal flux allows many users to share a single

band, a situation that may require specialized and highly sensitive receivers

for those who monitor EMI conditions.

Spread-spectrum and TDMA systems will be employed in all bands from HF to

SHF. The greater directivity of antennas at these frequencies may lead to

high power densities even though the transmitted power spectrum will have

lower density than in conventional transmissions. Spread-spectrum systems

being studied are so many and varied that we cannot yet predict the type of

EMI problems (if any) they may create. The National Telecommunications and

Information Administration (NTIA) has made no estimate of the probable impact

of spread-spectrum techniques because no such systems have been submitted for

NTIA evaluation.

Spread-spectrum systems require standardization. The Electromagnetic

Compatibility Analysis Center (ECAC) is working on the question of which

quantities to standardize and the measurement methods to characterize them. A

group at Ft. Monmouth is studying the properties of spread-spectrum signal

propagation, and has funded the Institute for Telecommunications Sciences of

NTIA to develop techniques for measuring these properties.

Most EMI receivers, while broadbanded, must be tuned. Monitoring the

multiple frequencies and broad spectral range of a spread-spectrum system with

such a receiver would be tedious and inefficient. A preferred approach may be

39
with a receiver of wide instantaneous bandwidth which would receive all

frequencies present over a short time interval.

Some spread-spectrum transmitters drive the antenna with Wal sh-function

current waveforms rather than a modulated sinewave carrier. Because Walsh

waveforms can be likened to irregular square waves (switching from (+) to (-)

polarity), the transmitted electromagnetic field is pulses (almost spikes) in

the same sequence as the switching times of the Walsh waveform. If two

different sets of such signals (pulses) are being received, the receiver must

be gated to accept the desired pulse series and reject the other. This is a different technique than tuning the receiver to be resonant to a sinusoidal EM

carrier wave. Thus, receivers to sense Walsh waveform transmissions will have

different features than conventional receivers.

An example of a spread-spectrum system would be one used to eliminate a central high-power transmitter by replacing it with several low-power units

located throughout the original central transmi tter ' s broadcast range. A

mobile unit would then communicate with the central station through the

nearest low-power transceiver. Because each local transceiver has its own frequency, the total system requires as many different frequencies as there

are local send-and-recei ve stations. Thus, in replacing a single-frequency

high-power source with several low-power sources, each at a different

frequency, a spread-spectrum system such as this may both relieve and

aggravate different aspects of an EMI environment.

4.3.3 Solar Power Satellite

The solar power satellite (SPS) system would comprise 60 geostationary

satellites, each about the size of Manhattan Island and each delivering a 5

GW, 2.45 GHz beam to its own receiving antenna within the United States. The

frequency is conventional, but the manner of power delivery may create

biological hazards and broadcast i nterference.

Sites for receiving antennas will be about 8 km in diameter. However,

the beam pattern and atmospheric scattering will distribute the beam power

40
over an area several times larger. The second harmonic (4.9 GHz) of the beam

will contain about 16 MW, and the fourth (9.8 GHz) about 500 W. Even the

fifth harmonic (12.25 GHz) may have upwards of 50 W. This range from 2.5-12

GHz has so many occupants that future satellite systems are being designed for

the 30 GHz region. Thus, the stray harmonic power from SPS beams may give

rise to significant EMI problems.

As of the completion of this report (September 1981) the future of the

SPS system is greatly in doubt. It has been reported, although no printed

confirmation is in hand, that the National Academy of Sciences has completed a report indicating the SPS is not a viable alternative and should not be

pursued further. In any event, if the SPS were approved, its completion would

require about 30 years from the date on which its deployment was begun. Solar

power from satellites is thus a concept of enormous magnitude and complexity,

but whose present uncertainty makes its attendant problems of little immediate

(the next 10-20 years) concern.

4.3.4 Higher Power

While solar power satellites and their high power microwave beams may not

get beyond their present conceptual stage, the gyrotron is a high power

continuous wave (cw) microwave oscillator being actively developed at several

laboratories here and abroad. The U.S. Naval Research Laboratory has tested a gyrotron traveling wave tube which produces 10 kW at 35 GHz. Refinements may

boost the power to 200 kW and give a 1 % bandwidth. NRL is also building a 240

GHz gyrotron. Varian Associates report obtaining 13 kW peak pulsed power from

a 5 GHz TWT gyrotron, and expect to scale their device to 94 GHz. Some

Russian organizations are also developing gyrotrons, and have made sales

offers to several U.S. companies.

Gyrotrons may find use in radar and communications, and as power sources

for fusion reactors. They may also be employed in electronic countermeasures

systems, and in target illuminators for passive imaging systems. High power

beams would be useful in millimeter wave communications (30-300 GHz) where

rain and atmospheric pollutants can severely attenuate transmitted beams. As

with the solar power satellite, power transmission by microwave beam is more

41
concept than accomplishment. Beamed power technology would require that

special antennas be designed for tight beams and minimal sidebands.

4.3.5 Communications Satellites

By the year 2000, as much as one-quarter of all long-distance voice

communications and one-half of all data and video traffic may be carried by

satellite, according to two studies done for the National Aeronautics and

Space Administration (NASA). This growth will saturate the present satellite

bands at 4-6 GHz and 11-14 GHz by the early 1990s, and is leading NASA to

develop satellite communications systems at 20-30 GHz.

Domestic satellites will increase their message-carrying capacity by

using high-speed satellite-switched time division multiple access systems.

Message capacity may also be increased by multiple-spot beams in which the

satellite beam is a bundle of separate beams at several frequencies, each

frequency being shared by several of the component beams. Those beams at a given frequency each carry different information. Multiple spot beams are expected to reduce interference between the satellite and other sources through the use of narrower beams and improved sidelobe control.

A proposal to relieve anticipated orbital congestion involves a satellite

called an Orbiting Antenna Farm. This large, multi-purpose satellite would

operate over a broad frequency range and assume the duties of several smaller

satel 1 i tes

.

A number of other uses are being proposed for satellite communications.

. The Navy will use radar satellites for monitoring ocean surface

conditions.

. Other Navy satellite systems may operate at 20, 40, and 45 GHz.

. Digital satellite systems may be used for local distribution of

business data.

42
. NASA is considering a satellite system with as many as 25 units,

each with a beam whose shape is controlled from a ground station.

. Another military satellite will be for video link processing in

which a TV picture is sent from an Airborne Warning and Control System

satellite to a ground station for processing.

4.3.6 Higher Frequencies

Because the present bands for microwave uses are filling, the next ten

years will see the adoption of new frequencies up to about 100 GHz with

clustering around 30, 60, 90 GHz. Today's test and measurement equipment does

not exceed 40 GHz.

The Navy is designing passive devices to detect radar signals in the 40-

60 GHz range, and is considering satellite-based radar at 95 GHz to monitor

ocean surface conditions as an indicator of local weather.

Having been squeezed from the 4-6 GHz band into 12-18 GHz, the users of

satellite systems see continued crowding forcing them into the 30 GHz region

and above. Military satellites are presently in the 7-8 GHz range though

designers expect to enter the 20-40 GHz range over the next ten years.

Operation of new military satellites above 40 GHz will come nearer 2000 AD.

In the near future, some earth communications systems (that is, not via

satellite) will operate at 20 GHz or higher between ground-based antennas and

recei vers.

The Army is considering communications systems at frequencies up to 300

GHz though the latter frequency probably won't be seen until after the turn of

the century. More immediate plans are for systems at 60 and 90 GHz.

The gyrotron, a high-power traveling-wave tube oscillator/amplifier,

attracted some interest in the late 1950s but was then shelved. Now some manufacturers and laboratories are looking closely at the gyrotron 's potential

for high power at high frequencies. The Naval Research Laboratory (NRL) has

43
tested a gyrotron at 35 GHz and 10 kW, and anticipates going to 200 kW. NRL

has built a 35 GHz gyrotron that gave 100 kW cw, and is building another to

operate at 240 GHz. A 30-month contract to Hughes Aircraft Co. should produce

a 10 kW gyrotron at 94 GHz.

Presently the primary application of gyrotrons is expected to be

microwave heating of plasmas in fusion reactors (18-120 GHz). There is also

speculation that mm waves (30-300 GHz) will propagate through the plasma of a nuclear explosion and thus allow contingency comuni cations through the blast's

fireball and turbulence.

A more mundane application may be that of the USAF which is considering

gyrotrons for use in radar and communications.

Soviet engineers have designed gyrotrons for which Russia is willing to

sell the rights. A pulsed model yields 1 MW at 100 GHz with 100 ps pulse

width. Another gives 1 kW at 330 GHz cw.

So we see the immediate intent to convert many commercial and military

systems to frequencies approaching 40 GHz, with serious thought being given to

employing the 50-100 GHz range within the next decade. Millimeter waves up to

300 GHz are foreseen in more speculative applications. Furthermore, these

systems will be capable of higher-power operation than has heretofore been

possible.

4.3.7 Proliferation

In this section, we have discussed some of the devices, systems, and

trends that the technical community sees as new or continuing sources of EMI over the next two decades. However, another and more pervasive aspect of EMI

is the phenomenon of proliferation. Advances in solid state technology are bringing an enormous and growing array of electronic devices into our domestic

lives as well as into technology and commerce. Seminal among these advances

are very large scale and high speed integrated circuits which, while providing

more powerful and compact means of measurement and control, are also heavy

contributors to the pro! iteration of the electronic circuit in our society.

44
Antennas are radiators and their radiation properties are well known.

Other devices also radiate but their fields are not evaluated and may not even

be anticipated. Such devices as personal computers, automotive electronics,

banking systems, cable and closed-circuit TV, and two-way communications often

have poorly known and controlled EM emissions as well as high susceptibility

to such emissions. A present concern is that stray fields from these devices

and systems can and do degrade the performance of nearby instruments. A

greater concern is that EMI will be increasingly deleterious as proliferation

continues.

EMI can be controlled by minimizing the EM radiation emitted by a device

and reducing its radiation susceptibility. Neither approach is practical to

carry to the point of certainty. Therefore, an essential part of any EMI

program is a monitoring system which measures the emissions from a given

device and evaluates the EM environment in which the device is to operate.

Clearly, the capabilities of such a measurement system must keep pace with

electronic prol i feration.

4.3.8 Renewed Emphasis on HF Communication

The realization that communication satellites are vulnerable to enemy

attack has led to a reassessment of the role of high frequencies (3 - 30 MHz

in military communications. Improved equipment in terms of size, portability,

power output, and reliability, plus the relative attack proof nature of the

ionosphere have led to a renewed interest in maintaining a strong military

communications capability in the 3-30 MHz range. Also, new techniques, using

"chirp sounders" which can evaluate the optimum frequency for any

communications path from one end of the circuit, combined with burst

communication systems (AN/TSC-99), have greatly increased the reliability of

HF circuits. The very presence of higher power transmitters co-located with

other vulnerable systems should ultimately mean increased EMEO tasking in this

frequency range.

4.3.9 Summary of Consequences of Anticipated EMI Sources

The preceding discussion of technologies likely to aggravate EMI problems

over the next two decades reveals nothing dramatically new compared with the

45
technologies of today. Instead, upcoming EMI aggravations are primarily

today's but evolved to higher powers and frequencies. Satellite

communications and radar are likely to be operating at several tens of

gigahertz, and the developers of the gyrotron talk about tens of kilowatts of cw power at up to 240 GHz.

Gyrotron cw power from 10-200 kW would be from 26-29 dB higher than an aircraft radar (typically about 40 kW peak pulse power) with an average cw power of 25 W. Air surveillance radar (425-550 kW peak pulse power) has an average cw power of about 400 W, and is the highest power unit at most FAA

airport installations. The 10-200 kW gyrotrons would be 14-27 dB higher than

the ASR average power. If such high rf-power sources as gyrotrons should find use in aircraft and airport radar systems, the 20-30 dB increase in their

radiated power flux density could be of concern to the EMI engineer.

The field strengths and power flux densities near a transmitting antenna

driven by a gyrotron would be an extreme, though not new, biological hazard.

Today's large radar and microwave transmitters produce power flux densities

that are equally hazardous (biological effects ranging from "rare" to "well

done" have similar consequences in an EMI context). Rather than these high

field intensities, the major EMI concern related to higher power sources is

the greater distance at which the source can commit electromagnetic

mischief. Even so, this greater pervasiveness just boosts the EMI power level

at locations remote from an antenna. A more provocative change in the EMI

environment is the appearance of frequencies higher than those which our present monitoring systems deal with. That is, the advent of higher

frequencies rather than higher powers is more likely to require the redesign

of EMI monitoring instruments.

Because packet radio and spread-spectrum systems scatter broadband

electromagnetic energy into the environment, they are further reason for

designing an EMI system with a wideband receiver.

46
5. NEW INSTRUMENTATION OPPORTUNITIES

5.1 Introduction

Advancing technology has provided new and improved devices and techniques

that can be exploited by the EMI metrologist. These include the following:

a. Instantaneous frequency measurement (IFM) techniques.

b. General improvements in solid-state devices through the development

of amorphous semiconductor technology.

c. Faster (gigabits/second) digital circuits to permit faster realtime

data processing, thus permitting more types of information to be extracted

simultaneously from a given set of input data.

d. Improvements in optical fibers and in opto-electronic devices.

e. Increased memory storage size and access speed resulting from the

further development of magnetic bubble technology.

f. Vastly greater application of time-domain metrology (as contrasted

with the present domination of frequency-domain metrology).

This section contains a brief discussion of these developments.

5.2 Instantaneous Frequency Measurement Receivers

The IFM receiver uses a comparatively recent circuit development to access large portions of the spectrum instantaneously. Most often an IFM will

give a digital display of the frequency being received. Present IFM's usually

have octave bandwidths or cover bands typically used in military

applications: 2-4 GHz, 4-8 GHz, 8-12 GHz, 12-18 GHz. Several IFM's in

parallel can cover a 0.5-18 GHz range with 100 percent intercept probability

for any signal exceeding the detection threshold. However, relative to a

47
superheterodyne receiver the IFM has lower sensitivity due to the noise

admitted by its wide bandwidth.

One manufacturer has combined digital IFM (DIFM) and superhet designs in one system which appears to successfully combine the strong points of both

receiver technologies. The system monitors a 0.5-18 GHz spectrum with high

sensitivity, fast signal acquisition, high probability of intercept, and

accurate measurement of signal parameters.

Another manufacturer has reduced the volume of its digital IFM receivers

from about 16400 cm^ to 1058 cm^ (1000 in^ to 64 in^). These receivers cover

the same bands as those mentioned above, and also the L (1-2 GHz) band.

This presently developing IFM and integrated IFM-superhet receiver

technology looks promising for EMI applications. To those interested, a spokesperson for one manufacturer advises that "systems engineers should make

an effort to determine what DIFM receivers manufacturers have built, are now building or plan to develop an IR&D programs."

In addition to these IFM circuit developments, new broadband antennas and

probes are becoming available. By resistive loading techniques, bandwidths

greater than 1 GHz with a linear phase response are possible. This permits

the accurate reception of broadband signals without serious waveform

distortion.

5.3 VLSI and VHSIC

Two of the newest developments in solid state and integrated circuit

electronics are pertinent to our inquiry into a smaller and more powerful EMI

measurement system: very large scale integration (VLSI) and very high speed

integrated circuits (VHSIC). The first help decrease circuit and component

sizes, as it has already done for the shrinking IFM two paragraphs before;, and

the second increases the speed of such circuit functions as computation and

signal processing. Between the two of them, VLSI and VHSIC are providing

smaller but more powerful devices for measurement and control. Thus, they are

48
giving electronic technology and its systems designers greater capability for

producing a compact, portable EMI metrology system which can do more things

faster.

By the greater use of CMOS technology, significant savings in power

requirements can be made. Reductions as great as 90 percent as compared with

TTL technology are possible. This can lighten the weight and reduce the size

of EMI instrumentation.

5.4 Fiber Optics

Fiber optics is another technology of high promise and rapid growth.

Optical communications (the primary fiber-optic application) has greater

bandwidth (and greater information-carrying capacity) because optical

frequencies are much higher than those of carrier waves in conventional

communications by broadcast or wire. The optical fibers themselves are dielectric "light pipes" and so are believed to be neither sources of nor susceptible to electromagnetic i nterference. With respect to EMI, fiber

optics is thus a very clean communications technology which will reduce EMI

problems as it replaces signal transmissions over wires.

Optical fibers are useful as leads which perturb an electromagnetic

environment as little as possible. They, therefore, could be of value as the

link between a probe and the rest of an EMI monitoring system.

5.5 Magnetic Bubble Memories

Since the 1967 discovery of magnetic bubble phenomena, bubble devices

have been steadily developed but only recently have received serious notice in

the marketplace. Now, magnetic bubble memories are filling the gap between

the short access time and high storage cost random access memories, and the

high access time and low storage cost moving surface memory devices (drum,

tape, disc). The appeal of bubble memories has increased with the appearance

of several commercial sources for bubble -memory test equipment.

49
A notable feature of bubble memories is their nonvol ati 1 i ty (ability to

retain stored information with power off). Thus, bubble devices are suited to

portable systems because additional battery packs are not needed for stand-by

power. In some military systems, bubble devices have contributed to extremely

small size and low weight, high untended reliability, and very low power.

Though VLSI is keeping semiconductor devices at the top of the market,

bubble chips are also compatible with and will benefit from VLSI. The future

of bubble technology is very promising, for these chips have not only memory

but also switching and logic capabilities. They are modular and offer large

data bandwidths through chips in parallel. The primary initial application

for bubble memory will be in fast auxiliary memories and in fixed-media mass storage in microcomputers.

5.6 Time Domain Metrology

The availability of higher-speed integrated circuits and switching

devices and the development of large computers and efficient software have

made time- domain measurements competitive with classic f requency-domai

n

measurements. With Josephson junction devices, it is now possible to sample

at picosecond rates with the promise of femtosecond rates in the forseeable

future. Fast computers with large computational capability make it feasible

to transform time-domain data to frequency-domain information (e.g., by FFT

algorithms) when this is desired. However, engineers are now learning to

"think" in terms of time-domain processes, even for the faster signals having

frequencies in the gigahertz range.

6. CONCLUSIONS

6.1 Purpose

The purpose of this section is to apply the information presented in

sections 1 - 5 to the mission of EMEO. The specific mission tasks of EMEO

will be compared to the new requirements and possible advances in technology

to see where impacts may occur. Lastly, some of the driving forces of the

marketplace will be examined as they affect the availability of measurement

equipment suited to the mission of EMEO.

50
6.2 Specific EMEO Tasking

In par. 1.2 the broad areas of EMI measurements in which EMEO engages

were enumerated. However, these can be more narrowly defined in an operational way by examining the specific task areas of EMEO involving EMI

measurements

a. SHF DSCS. This involves performing general spectrum occupation

surveys of a contemplated satellite ground station site for the

Defense Satellite Communications System. Occasionally measurements

to estimate ERP from a satellite are made.

b. UHF SAT. This is similar to (a) above but involves different

measurements and equipment.

c. EMRH. These measurements usually of high level fields, are made to

estimate the EMR environment to which sensitive military equipment

will be exposed.

d. ATC. Generalized interference (EMI) problems with military air

traffic control communications.

e. LOS. Measurement of path loss and fading on direct path UHF and

microwave links.

f. EMC. Generalized EMC/EMI measurement problems not specifically in one of the other categories.

g. N.T. New tasking which will arise as more complex electronic

equipment involving new technology is deployed by the Army.

6.3 Impact of New Requirements

In section 4 the technological areas of possible new requirements were

discussed. These are numbered, in the list which follows, for use in

51
table A. This table, by means of coded symbols explained below, indicates the

task area of impact.

1. Packet Radio

2. Spread Spectrum

3. Solar Power Satellites

4. Higher Power

5. New Communications Satellites

6. Higher Frequencies

7. Pro! iteration of Sources

8. Renewed Interest in HF

Technological Area

Impact Area 1 2 3 4 5 6 7 8 £ Score

SHF DSCS + + ++ + + ++ + - 8+

UHF SAT 0 + + + - - + - 1+

EMRH 0 0 ++ ++ - 0 + ++ 6+

ATC 0 + 0 + 0 0 + 0 3+

LOS ++ + 0 0 - + + - 3+

EMC + + ++ ++ 0 + ++ ++ 11+

NT ++ ++ 0 + + + + + 9+

£ Score 6+ 7+ 7+ 8+ 1- 4+ 8+ 2+

Legend ++ high impact

+ moderate impact

0 little change

reduced impact because new technology is superseding

Table A. Impact of New Requirements/Technology on EMEO Tasking.

52
6.4 Impact of New Technological Advances on EMEO

Measurement Techniques and Equipment

In section 5, new areas of instrumentation opportunities were discussed. They are enumerated below with one or two additional allied

categories added from other sections of the report. The impact of these

advances in EMI measurement technology are then compared with the different

EMEO task areas in table B using the same symbology as in table A.

I. Instantaneous Frequency Measurement Receiver

II. VLSI and VHSIC

III. Fiber Optics

IV. Magnetic Bubble Memories

V. Time Domain Metrology

VI. Generalized Techniques for Describing the

EMI Environment

VII. New Antenna Designs

Instrumentation Technological Area

Impact Area I II III IV V VI VII E Score

SHF DSCS ++ 0 0 0 + + 0 4+

UHF SAT + 0 0 0 + + 0 3+

EMRH 0 0 - + ++ ++ ++ 6+

ATC + + 0 0 + + + 5+

LOS 0 + 0 ++ 0 0 0 3+

EMC + ++ - ++ ++ ++ + 9+

NT + + + + ++ + + 8+

E Score 6+ 5+ 1- 6+ 9+ 8+ 5+

Legend ++ high impact

+ moderate impact

0 little change

reduced impact because new technology is superseding.

Table B. Impact of New Technological Advances on EMEO Measurement Techniques

and Equipment.

53
6.5 Observations

Looking at table A, it can be seen that the major EMEO areas impacted are

SHF DSCS, EMRH, general EMC measurements, and unknown new tasks. By looking

at the sums across the bottom it can be seen which technological areas will cause the most effect, namely, higher power and prol i feration of sources,

although a few other areas are close behind.

Turning to table B, we see that the areas of measurement capability

impacted by new technology (a positive score means an increased capability)

are EMRH, generalized EMC measurements, and unknown new tasking. Likewise

referring to the bottom sums, the advances in time domain metrology and

generalized techniques for describing the EMI environment should impact the

measurement process the most, although again, several other areas will also

have a major effect.

Note that the high scores in generalized EMI measurements would seem to

indicate that EMEO will have a need in this area and that there should be

adequate measurement technological advances available to meet this need.

However, before this assumption can be made the forces which control the

availability of equipment for this marketplace must be examined.

6.6 Driving Forces in the Marketplace

Since EMEO is largely constrained to obtaining equipment that is

commercially available, off the shelf, (or modifications thereof), it is

necessary to see what are the driving forces that control the development, and

hence the availability, of such equipment. This is assuming that no substantial funds are available from Military Research and Development

Commands to support specific developments.

The three main forces or needs in the marketplace that have influenced

the development of EMI/field strength measuring equipment over the past twenty

years are:

54
1. Compliance testing to MIL STD 461 mandated by government

contract requi rements.

2. Specialized needs of the security agencies of the government

such as ASA, CIA, etc.

3. Commercial measurement needs to satisfy FCC type acceptance

testing and field strength survey requirements for broadcast

stations.

Obviously, there is some overlap in the requirements of these various areas of

the user community, but definite segments of the electronics market can be

identified with these areas.

To these three areas can be added a fourth category called "modern

spectrum analyzers." Early equipment of this type was often considered

inadequate for general EMI field measurements because of lack of sensitivity

and susceptibility to overloading with strong signals. However, recent

improvements in these parameters, the addition of phase lock loops to give

accurate frequency information, and the incorporation of a microprocessor to

control and handle data, have made these instruments more useful.

Unfortunately, they are generally not designed for rugged field use, and do

not have shielding adequate to operate in strong ambient fields.

Table C examines these categories of equipment from the standpoint of

market share, size and weight, ruggedness, shielding, general quality,

flexibility and usefulness to EMEO measurement needs, willingness of the

manufacturers to produce small quantities of specialized measurement equipment

modified to a user's need, and accuracy of frequency and amplitude

measurement. The share of the marketplace estimates were arrived at by

talking with the marketing representatives of several manufacturers. Although

they show general trends no particular accuracy is claimed for the numbers

given. The estimates of the other performance parameters are those of the

authors, although they have been discussed with other engineers involved in

EMI measurements.

55
TYPE OF EQUIPMENT 1 2 3 4 5 6 7 8

FIMs - designed for 55% P E E F P P E MIL STD 461 testing G**

Specialized EMR 25% G G G F F E P security equipment +

FCC compliance and

misc. commercial field

15% F F F P P P G

measurement equipment

Modern spectrum 5% P ? P G** P G E analyzers

Notes: *, % of EMI market only

**, particulary when used with external computers.

+, at a high cost, usually

Code

1. % of marketplace (estimate) in dollars

2. Small size and weight

3. Ruggedness

4. Shielding

5. Flexibility

6. Willingness of manufacturer to modify.

7. Accuracy of frequency measurement.

8. Accuracy of amplitude measurement.

E = excellent

G = good

F = fair

P = poor

Table C. EMI Equipment Analysis.

As can be seen in table C, no one category of equipment scores high in all

desired qualities, and few, if any, manufacturers are willing to produce small

quantities of custom equipment at a reasonable price. Although technological

forecasting is difficult, it is likely that the primary driving force in the

marketplace, i.e., MIL STD 461 testing requirements, will remain dominant for

the next several years. Thus it would appear that equipment expressly

tailored to the needs of EMEO is not likely to be forthcoming without being

specifically developed with R&D funds.

56
\

U Zb. DEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. Report No. 3. Publ ication Date BIBLIOGRAPHIC DATA

SHEET (See instructions)

REPORT NO.

NBSIR 82-1662 April 1982

4. TITLE AND SUBTITLE

Planning Guidance for Future EMI Measurement Instrumentation

5. AUTHOR(S)

M. G. Arthur, R. D. Orr, G. R. Reeve

6. PERFORMING ORGANIZATION (If joint or other than NBS. see in struction s) 7. Contract/Grant No. national bureau of standards

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State. ZIP)

Command er

U.S. Army Communications Electronics

Engineering Installation Agency

Fort Huachuca, Arizona 85613

10. SUPPLEMENTARY NOTES

Document describes a computer program; SF-185, FlPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant in formation. If document includes a significant

bibliography or literature survey, mention it here) The environment in which electronic apparatus of all types must function is becoming

increasingly hostile because of a burgeoning electronic technology. This increases

the potential for electromagnetic interference (EMI), and places new demands upon

those organizations who are responsible for measuring EMI. This report (a) reviews

the electrical quantities that are used to describe and evaluate EMI, (bj discusses

current EMI measurement principles, (c) attempts to identify future EMI measurement

requirements for the post 1985-1990 time period, (d) identifies certain expected new instrumentation opportunities, and (e) suggests action to meet the future needs for

measurement instrumentation.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitali ze only proper names; and separate key words by semicolons)

Electromagnetic interference; electromagnetic environment; EMI instrumentation;

EMI measurements; future EMI requirements; planning guidance.

13.

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