THE STANDARDIZATION OF UWB WAVEFORM CHARACTERISTICS BY THE
INTERNATIONAL ELECTROTECHNICAL COMMISSION (Invited)
W. Radasky(1), D. Giri(2)
(1)
Metatech Corporation, 358 S. Fairview Ave., Suite E, Goleta, CA 93117 USA, E-mail: wradasky@aol.com
(2)
Pro-Tech, 11-C Orchard Court, Alamo, CA 94507-1541 USA, E-mail: Giri@DVGiri.com
ABSTRACT
The term ultrawideband (UWB) has been used for many years to refer to a wide range of waveform characteristics.
Recently the International Electrotechnical Commission (IEC), headquartered in Geneva, Switzerland, has been
studying the threats of high power electromagnetic fields and injected voltages/currents on elements of the civil
infrastructure. It was found that the classical definitions for “wideband” and “ultrawideband” were not sufficient for the
work at hand, and therefore a new standard was developed to classify waveforms of interest to the high-power EM
community. This paper will review the definitions of that standard, IEC 61000-2-13.
INTRODUCTION
The term ultrawideband (UWB) has been used for many years to refer to a wide range of waveform characteristics.
Recently the International Electrotechnical Commission (IEC), headquartered in Geneva, Switzerland, has been
studying the threats of high power electromagnetic fields and injected voltages/currents on elements of the civil
infrastructure. As part of that effort, two general classes of threat waveforms are under investigation – pulses and
continuous waves. Within these two general classes, some of the most interesting pulse waveforms are those that
possess a very wide bandwidth. It was found, however, that the classical definitions for wideband and ultrawideband
were not sufficient for the work at hand, and therefore a new standard was developed to classify waveforms of interest
to the high-power EM community. This paper will review in some detail the four categories of waveforms that are
contained in IEC 61000–2-13, “High-Power Electromagnetic (HPEM) Environments - Radiated and Conducted” [1].
WAVEFORM DEFINITIONS
The usual bandwidth definitions involve the percentage bandwidth (pbw), which is defined as the frequency difference
between the two 3-db points (on either side of the center frequency) divided by the center frequency.
However, we observe that the pbw definition comes from a “communications signal” viewpoint and is inadequate, in the
context of ultrawideband signals, when practical waveforms have already achieved percent bandwidths of > 190 % out
of a possible maximum of 200 %. Therefore it is recommended that one use the following definitions described in
IEC 61000-2-13:
f
bandratio = br = h
f!
(br ! 1)
pbw = 200
(br + 1)
pbw
]
200
br =
pbw
[1 !
]
200
[1 +
(1)
Using the inherent features of the above definitions, and in a manner consistent with the emerging technologies for
producing high power EM threats, the following terminologies for bandwidth classification are provided below in
Table 1.
This paper discusses these definitions in additional detail, and will provide the methodology to determine the high and
low frequencies as indicated in (1). In addition, this paper will provide examples of how the IEC standard is applied in
the field of high-power electromagnetics.
Table 1. Definitions for bandwidth classification [1]
Band type
Percent bandwidth (pbw)
Bandratio (br)
Hypoband or
narrowband
≤1%
br ≤ 1.01
Mesoband
1 % < pbw ≤ 100 %
1.01 < br ≤ 3
Sub-hyperband
100 % < pbw ≤ 163.4 %
3 < br ≤ 10
Hyperband
163.4 % < pbw ≤ 200 %
br > 10
Determination of High and Low Frequencies
At this point we define the method of determining the bandratio br for typical HPEM waveforms and contrast it with the
more common definition of 3 dB points, which are the frequencies where the spectral amplitude drops by 3 dB from the
peak value.
The criterion for the finding of f! and fh should be based on the energy content in a certain spectral interval, as follows.
(
)
(
)
Find !f fh ,f! = fh " f! such that !f fh ,f! = fh " f! becomes minimal and
fh
~
" V ( j! )
2
d!
f!
#
~
" V ( j! )
0
= 0.9
2
(2)
d!
This definition ensures that 90 % of the overall energy is contained in the interval [ f! , fh].
SIGNALS WITH A MULTIPEAKED SPECTRUM
The following example describes an important case for which the approach described in this paper works well. The
majority of the energy in Figure 1 below is clearly not contained in the 3 dB frequency interval [f1, f3]. The bandwidth
of “multipeaked” signals is much better determined using the 90 % energy definition, which is found from integrating
the frequency waveform to find the values flow and fhigh according to (2).
Figure 1. A waveform with a multipeaked spectral magnitude
SIGNALS WITH A SIGNIFICANT DC PART IN THE SPECTRUM
For the example shown in Figure 2, a spectral magnitude with a large DC value from IEC 61000-2-9 [2], one can use
the following procedure. Use 1 Hz as the lower frequency limit f ! and find the upper frequency limit fh that contains
90 % of the energy. Then calculate the bandratio. Next increase the value of fh and redetermine a new value of f ! using
the 90 % criterion. Repeat this process until the minimum value of delta f is found; then compute the bandratio using
these values.
Figure 2. A waveform spectrum with a large dc content
SUB-HYPERBAND AND HYPERBAND HPEM ENVIRONMENTS
HPEM generator and antenna technologies, which can radiate a flat electromagnetic spectrum from 10s of MHz to
several GHz, are presently capable of producing a peak time-domain (rE) product of several MV. With advancements
in high-power and fast switching technologies, the (rE) product is likely to get higher. The higher rE products enable a
generator and its antenna to produce a large EM field at a significant distance, posing a more serious threat to equipment
and systems.
It is well known from susceptibility studies with commercial electronics, that pulses with fast rise times produce
significant high-frequency content that is more easily able to penetrate slots and other apertures in the external cases of
PCs and other microproccessor equipment [3]. Therefore the bandwidth of an incident electromagnetic field is an
important factor in determining the peak field level of upset or damage of equipment.
One of the main ways of generating hyperband HPEM environments is through the use of an Impulse Radiating
Antenna (IRA) as illustrated in Figure 3. Examples of HPEM environments produced by IRAs are documented in
Table 2.
Figure 3. Line schematic of a reflector type of an Impulse Radiating Antenna (IRA)
Table 2. Examples of reflector types of Impulse Radiating Antennas (IRAs) [1]
No.
Name
Pulser
Antenna
Prototype IRA
100ps/20ns
3,66 m dia
USA
200 Hz
burst
(F/D)=0,33
Upgraded
prototype IRA
± ~ 75 kV
85 ps/20 ns
± 60 kV
1
2
USA
~ 400 Hz
2,8 kV
3
Swiss IRA
100 ps/4 ns
800 Hz
4
Netherlands
IRA
5
German IRA
9 kV
100 ps/4 ns
800 Hz
9 kV
100 ps/4 ns
800 Hz
1,83 m dia
(F/D)=0,33
1,8 m dia
(F/D)=0,28
Near field
Far field
23 kV/m
4,2 kV/m
at
at
r = 2 m
r = 304 m
41,6 kV/m
at
27,6 kV/m
at
r = 16,6 m
r = 25 m
1,4 kV/m
220 V/m
at
at
r = 5 m
r = 41 m
r E
Bandratio, b r
Band
1 280 kV
100
Hyper
690 kV
50
Hyper
10 kV
50
Hyper
34 kV
25
Hyper
34 kV
25
Hyper
7 kV/m
0,9 m dia
at
Not
(F/D)=0,37
r = 1 m
available
7 kV/m
0,9 m dia
(F/D)=0,37
at
r =1 m
Not
available
As per the definitions in Table 1, all of the systems presented in Table 2 are hyperband HPEM generators, since their
bandratios are greater than 10. However, it is observed that they can also be turned into sub-hyperband generators by
reducing the antenna diameter (increases the lower cutoff frequency) or by degrading the rise time of the voltage pulse
into the antenna (lowers the upper cutoff frequency).
CONCLUSIONS
The terminology and applications for wideband high power electromagnetic (HPEM) environments have been
standardized in IEC 61000-2-13. In addition a survey of hyperband HPEM generators that have been built and tested at
laboratories throughout the world have been presented.
REFERENCES
[1] IEC 61000-2-13, Electromagnetic Compatibility (EMC) – Part 2-13: Environment: “High-power electromagnetic
(HPEM) environments – radiated and conducted,” International Electrotechnical Commission, Geneva,
Switzerland, 2005.
[2] IEC 61000-2-9, Electromagnetic Compatibility (EMC) – Part 2: Environment – Section 9: “Description of HEMP
environment – Radiated disturbance,” International Electrotechnical Commission, Geneva, Switzerland, 1996.
[3] Nitsch, D., A. Bausen, J. Maack, R. Krzikalla, “The Effects of HEMP and UWB pulses on Complex Computer
Systems, ” Zurich EMC Symposium, February 2005, pp. 373-376.