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PARABOLOIDAL AND PROLATE-SPHEROIDAL IMPULSE RADIATING
ANTENNAS WITH ILLUSTRATIVE EXAMPLES
Dr. D. V. Giri
Pro-Tech, 11-C Orchard Court, Alamo, CA 94507-1541 USA, [email protected], www.dvgiri.com
ABSTRACT
We start this paper with a four-band classification of
high-power electromagnetic (HPEM) waveformsbased on bandwidth that has been recently proposed
and formalized. An antenna system that radiates
impulse-like waveforms making use of reflectors hasbeen called the impulse radiating antenna (IRA).
More recently prolate-spheroidal surfaces are being
considered to fabricate such antennas for specializedapplications. This paper presents these antennas along
with some representative applications.
1. INTRODUCTION
It is well established that sufficiently intenseelectromagnetic (EM) signals in the frequency range
of 200 MHz to 5 GHz can cause upset or damage in
electronic systems. This induced effect in an
electronic system is commonly referred to as
intentional electro-magnetic interference (IEMI).Such an intentional electro-magnetic
environment (IEME) can be:
a single pulse with many cycles of a singlefrequency (an intense narrowband signal that
may have some frequency agility),
a burst containing many pulses, with eachpulse containing many cycles of a single
frequency,
an ultra-wideband pulse (spectral contentfrom 100s of MHz to several GHz), or
a burst of many ultra-wideband transientpulses,
Note that all of the above EM environments could be
radiated or conducted. One way of classifying the
HPEM environments is based on the frequency
content of their spectral densities as narrowband,moderate band, ultra-moderate band and
hyperband. To characterize these environments, we
consider the bandratio of the EM spectrumas ( / )hbr f f = l . Using the inherent features of br
in a manner consistent with the emerging EM field
production technologies, the definitions forbandwidth classification presented in Table 1 has
been proposed [1, 2].
TABLE 1
HPEM CLASSIFICATION BASED ON BANDWIDTH
Band type
Percent bandwidth
1200 (%)
1
brpbw
br
=
+
Bandratio
br
Narrow< 1% < 1.01
Moderate
1%
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2. HYPERBAND SYSTEMS
(163.64 % < pbw < 200%) or ( br> 10)
Since it was the first proposed in 1989 [5] ,
paraboloidal reflectors fed by TEM transmission lines
have received a lot of attention, owing to their main
attractive property of extremely wide bandwidth,
without the adverse effects of dispersion. They havebeen called the impulse radiating antennas (IRAs) anda photograph of an example, the prototype IRA in
Figure 1.
Figure 1. Photograph of the 3.67m Prototype IRA
The bandwidth associated with time-domain antennas
is to be distinguished from the approximately 10 to 1
bandwidth of the so called frequency independentantennas such as the log-periodic antenna, which is
highly dispersive since the phase center of the
antenna is not fixed. Different CW frequencies
applied to a log-periodic antenna get radiated from
different portions of the antenna, which makes itdispersive, if all of the frequencies are applied at the
same time as in a pulsed application. Reflector IRAs
overcome this problem and even have equivalentelectric and magnetic dipole moments characterizing
the low-frequency performance. Even the dipolar
radiation at low frequencies is along the optical axis
of the reflector. Many optimal reflector IRAs hasbeen designed, fabricated and tested. Some of them
are summarized in Table 2 with various performance
parameters.
3.ILLUSTRATIVE APPLICATIONS
Hyperband systems can be built in many forms such
as reflector IRAs described above, or TEM horns [6],
and lens IRAs [7]. They have useful applications such
as:
Disrupter (Disrupting Integrated System,Releasing Ultra-PowerTransient
Electromagnetic Radiation) [8]
Buried target detection such as demining [9]
Hostile target detection and identification[10]
Space debris detection Periscope detection Source for vulnerability studies via transfer
functions [11]
high-power, hyper -wideband jammers [12] law-enforcement applications such as
seeing through walls [13] Electrical characterization of materials (e.g.,
wave propagation measurements inmaterials such as rock, concrete etc.,)
Industrial applications (detection of leaky ordefective pipes) [14]
Detection of human beings in earthquakerubble [15]
Searching for avalanche victims [16] Artillery application [17]etc.
They can be designed to operate from 10s of MHz toseveral GHz. This is an extremely wideband spectrum
where critical military and civilian operations take
place in the field of radar and communicationengineering.
We will briefly discuss three of the above
mentioned applications.
3.1 Transfer Function of Buried Facilities
The Swiss IRA described in Table 3 was employed in
measuring the responses of a buried test-bed facility
for HPEM environments. The facility was a concrete
reinforced building buried in the earth. It had a smallabove-ground concrete structure that provided
protection for the stairway leading from the surface to
the working area below, as seen in figure 2.
Figure 2. Exterior view of the underground Swisstest-bed facility
The test data was gathered for both the pulse and CWilluminations. The same IRA was used for both types
of excitations. Figure 3 represents the measuredtransient E-field from the IRA at a distance of 6 m
from the radiator.
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Table 2. Some examples of Paraboloidal reflector IRAs with performance characteristics
0 2E-008 4E-008 6E-008 8E-008 1E-007
Time (s)
-400
0
400
800
1200
E(t)(V/m)
Data File M001.datd = 6 m
Figure 3. Measured transient IRA field at a distance of 6m from the antenna
# Name Pulser Antenna Far field r E r E / Vo br
1 Prototype IRA
AFRL, KAFB, NM USA
+ 60 kV
100ps/20ns
200 Hz
3.66m dia
(F/D) = 0.33
4.2 kV/m
at r =
304m
1280 kV 10.67 100
2 Upgraded Prototype IRA
AFRL,KAFB, NM, USA
+ ~ 75 kV
85 ps/ 20 ns
~ 400 Hz
1.83 m dia
(F/D) = 0.33
27.6 kV/m
at r = 25 m
690 kV 5 to 6
(est.)
50
3 Swiss IRA, NEMP Lab,
Spiez, Switzerland
2.8 kV
100 ps/4 ns
800 Hz
1.8 m dia
(F/D) = 0.28
220 V/m
at r = 41 m
10 kV 4 50
4 TNO IRA
The Netherlands
9 kV
100 ps/ 4 ns
800 Hz
0.9 m dia
(F/D) = 0.37
Not
available
34 kV 3 to 4 24
5 Magdeburg, Germany 9 kV
100 ps/ 4 ns
800 Hz
0.9 m dia
(F/D) = 0.37
Not
available
34 kV
(est.)
3 to 4
(est.)
24
6 Pro-Tech, Alamo, CA 2.8 kV
100 ps / 4 ns
800 Hz
23 cm dia
(F/D) = 0.35
Not
available
10 kV
(est.)
3
(est.)
6
7 Pro-Tech, Alamo, CA Yet to be
measured
10 cm dia
(F/D) = 0.33
Not
available
Not
available
Not
available
2.6
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In this measurement, a number of different antenna
locations and observation points for EM fields and
induced wire currents were made. One of the first facility
measurements made was with the IRA source located atthe main entrance. The measured transient and computed
spectral E-fields inside the facility with the main dooropen and shut cases are illustrated in figure 4.
At the bottom of the stairs in the facility entrance was
a power system interconnection panel, where a groundwire was instrumented with a current probe.
0 2E-008 4E-008 6E-008 8E-008 1E-007
Time (s)
-1000
-500
0
500
1000
1500
E(t)
(V/m)
Data File M006.dat
M007.dat
(door open and shut)Door open
Door shut
1E+007 1E+008 1E+009 1E+010
Frequency (Hz)
1E-011
1E-010
1E-009
1E-008
1E-007
1E-006
1E-005
0.0001
|E()|(V/m/Hz)
Data File M006.datM007.dat
(Door open and shut)
Door openDoor shut
Figure 4. Measured E-filed inside the facility with
the door open and shut configuration
Measured transient current in this wire is shown in
Figure 5.
Figure 5. Measured transient current on a power lineneutral and the corresponding computed
spectral magnitude
The testing of this buried facility resulted in a number
of interesting results both for the EM field penetrationinto the facility, as well as for the induced currents in
power and communication lines. From these
measurements transfer functions are calculated and can
be compared with computational models. With the IRA
as a pulsed antenna, the transfer function measurements
are done by a Fourier transformation of the inducedtransient responses, thus greatly reducing the problem
complexity.
3.1 JOLT (Hyperband Radiator)The JOLT antenna is a half-IRA with a 3.05m diameter,
paraboloidal, commercial microwave reflector that has
been cut in half and flanged for attachment to the ground
plane. The transient energy source located at the focalpoint of this reflector launches a near-ideal TEM
spherical wave on to the reflector through a
polypropylene lens to be reflected as a collimated beam.
A line schematic diagram and a photograph of the JOLT
system are shown in figures 6 and 7.
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Figure 6. Schematic of a Half IRA
Figure 7. Photograph of JOLT Radiator
The JOLT is a high-voltage transient system built at
the Air Force Research Laboratory, Kirtland AFB, NM
during 1997-1999. The pulsed power system centers on a
very compact resonant transformer capable of generating
over 1 MV at a pulse repetition frequency of 600 Hz.This is switched via an integrated transfer capacitor and
an oil peaking switch onto an 85 Ohm half IRA. This
unique system will deliver a far radiated field with a full-
width half maximum (FWHM) on the order of 100 ps,and a field range product ( r E peak) of ~ 5.3 MV,
exceeding all previously reported results. Arepresentative measured far-electric field is shown in
Figure 8.
Figure 8. Measured electric field at a boresight
distance of r = 85m
It is seen that the impulse-like radiated field from the
JOLT seen in figure 8 has an extremely large bandwidth
ranging from about 40 MHz to about 4 GHz or a band
ratio of 100. Such HPEM environments are useful in
specialized applications.
3.2 Seeing Through Walls
Tatoian et al [13] have employed a reflector IRA pair
(transmit and receive) to get a one-dimensional through
the wall radar signatures of certain objects. Figure 9presents a representative sample of the measured data.
The shown signatures are the result of 2-way wave
propagation (Impulse radar- generated wave propagatesthrough-the-wall scatters from the target on the other side
of the wall, comes back through the same wall and is
received by the same radar).
Figure 9. One-dimensional through the wall radar
return signal Man only (red)M16 only (blue) Man with
M16 (black),
The test wall consisted of an 8-inch concrete slab with
two layers of 3-gage metallic rebar inside and yielded 56
dB two-way power attenuation. The targets included
Man, Man and M16 rifle, M16 rifle only. Each graph infigure 11represents true radar signature, or signal-related
voltage, S, associated with the specific test target. The
time axis corresponds to a round-trip travel distance of15.24 m. Work is in progress in this area and expected to
lead to target imaging using Impulse Synthetic Aperture
Radar (ISAR).
4. Prolate-Spheroidal IRA
Paraboloidal IRAs described above produce a beam thatis focused at infinity. There are emerging applicationsthat require focusing at a finite distance. This is possible
if the reflector is a prolate spheroid instead of a
paraboloid [18, 19, 20 and 21]. The prolate spheroid hastwo foci. The antenna is excited at one of the foci and the
energy is focused at the second focal point.
0 1 .108
2 .108
3 .108
4 .108
5 .108
2
1
0
1
2
3Through-the-Wall Sensing: Combined
Time, sec
Voltage,
V
2.36
1.699
ds1n
ds2n
ds3n
4.995108.0 timen
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5.Summary
In this paper, we have presented the 4-way classification
of HPEM environments based on bandwidth. Thisclassification is based on emerging technologies and
example systems in each of the four categories are alsodescribed. In addition, illustrative examples of
Hyperband radiators, which are finding many useful
applications both in the military and civilian sectors, are
described.
References1. D. V. Giri, Classification of Intentional
Electromagnetic Interference (EMI) Based on
Bandwidth, AMEREM 2002, Annapolis, Maryland,
2-7 June 2002.
2. D. V. Giri and F. M. Tesche, Classification ofIntentional Electromagnetic Environments (IEME),
IEEE Transactions on Electromagnetic
Compatibility, Volume 46, Number 3, August 2004.
3. V. Fortov, F. Loborev, Yu. Parfenov, V. Sizranov,B. Yankovskii,, and W. Radasky, Estimation of
Pulse Electromagnetic Disturbances Penetrating
into Computers Through Building Power andEarthing Circuits, Metatech Corporation, Meta-R-
176, December 2000.
4. V. Fortov, Yu. Parfenov, L. Zdoukhov, ,R. Borisov,S. Petrov, L. Siniy, and W. Radasky,Experimental
Data on Upsets or Failures of Electronic Systems toElectric Impulses Penetrating into Building Power
and Earthing Nets, Metatech Corporation, Meta-R-
187, December 2001.5. C. E. Baum,Radiation of Impulse-Like Transient
Fields, Sensor and Simulation Note 321,
November 25, 1989.
6. C. E. Baum, Low-Frequency Compensated TEMHorn, Sensor and Simulation Note 377, 28 Jan 1995.
7. E. G. Farr,Boresight Field of a Lens IRA, Sensor andSimulation Note 370, October 1994.
8. C. E. Baum, The Disrupter, Transient Radiating
Antenna Memo 4, 19 May 1998.
9. Humanitarian Demining at TNO Laboratory, The
Hague, The Netherlands.
10. Detection and Identification of Visually ObscuredTargets, edited by C. E. Baum, published by Taylor
and Francis, 1998.
11. F. M. Tesche, D. V. Giri, P. F. Bertholet, A. Jaquier,and A. W. Kaelin, Measurements of High-Power
Electromagnetic Field Interaction with a Buried
Facility, ICEEA Torino, 10-14 September 2001, pp99-102,
12. C. E. Baum, et. all.,JOLT: A Highly Directive, Very
Intensive, Impulse-Like Radiator, Invited Paper in theProceedings of the IEEE, Special Issue on Pulsed
Power Technology and Applications, pp 1096-1109,
July 2004.
13. J. T. Tatoian, D. V. Giri, R. Manzano, and G. Gibbs,
Feasibility of an ImpulseRadiating Antenna (IRA) forThrough the Wall Sensing, ICEAA Torino, 8-12
September 2003, pp 389-392.
14. C. Maierhofer, T. Kind, J. Woestmann, and H.Wiggenhauser, Antenna Development for ImpulseRadar Applications in Civil Engineering, EUROEM
2004, Magdeburg, Germany, 12-16 July 2004.
15. I. Akiyama, Y. Araki, M. Isozaki, M. Ohki, and A.Ohya, UWB Radar System Sensing of Human Being
Buried in Rubbles for Earthquake Disaster,EUROEM 2004, Magdeburg, Germany, 12-16 July
2004.
16. W. A. Chamma, H. Mende, and R. Robinson, UltraWideband Radar for the Search of AvalancheVictims, EUROEM 2004, Magdeburg, Germany,
12-16 July 2004.
17. H. Herlemann, M. Koch, and F. Sabath, UWBAntenna for Artillery Applications, EUROEM 2004,
Magdeburg, Germany, 12-16 July 2004.18. K. Kim and W. R. Scott, Jr, Analysis of Impulse
Radiating Antennas with Ellipsoidal Reflector,
Sensor and Simulation Note 481, 31 October 200319. C. E. Baum, Producing Large Transient
Electromagnetic Fields in a Small Region: An
Electromagnetic Implosion, Sensor and Simulation
Note 501, August 2005.
20. C. E. Baum, Focal Waveform of a Prolate-Spheroidal IRA, Sensor and Simulation Note 509,
February 2006
21. D. V. Giri, Analysis of an Impulse RadiatingAntenna with a Prolate-Spheroidal Reflector,
presented at the AMEREM 2006 Symposium held at
Albuquerque Convention Center, July 10-14,
Albuquerque, NM.
1967 and 1969, respectively. He continued his graduate
study at Harvard University receiving M.S. (Applied
Mathematics, 1973) and Ph.D (Applied Physics, 1975).
Dr. Giri has taught in the Dept. of EECS, University of
California, Berkeley campus and is presently a self-
employed consultant as Pro-Tech, in Alamo, CA, doingR&D work for U.S. Government and Industry. Dr. Giri
was a Resident Research Associate for the National
Research Council at the Air Force Research Laboratory(AFRL) Kirtland AFB, New Mexico, (1975-77). Dr. Giri
is a senior member of the IEEE Society of Antennas andPropagation, a Charter member of the ElectromagneticsSociety, and Associate member of Commission B, URSI
and member of Commission E, URSI. He has served as
an Associate Editor for the IEEE Transactions onElectromagnetic Compatibility. He is an EMP Fellow of
Summa Foundation in 1994 for his contribution to EMP
simulator design HPM antenna design. He has published
two books, one book chapter and over a hundred papers,
reports etc. He is also a recipient of the John KrausAward from the IEEE for 2006.
D. V. Giri was born in India and
is a naturalized U.S. citizen. He
received the B.Sc. degree in
Physics and Mathematics fromMysore University in 1964. He
then entered the Indian Institute of
Science and received the B. E.
and M. E. (Microwaves) in