7/28/2019 04584503

1/6

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, Giri@DVGiri.com, 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%

7/28/2019 04584503

2/6

2

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.

7/28/2019 04584503

3/6

3

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

6

7/28/2019 04584503

4/6

4

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.

7/28/2019 04584503

5/6

5

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

7/28/2019 04584503

6/6

6

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