Radiation by a Slotted Conducting Elliptic Cylinder

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IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 60, NO. 11, NOVEMBER 2012 5433

was 50.3%. Excluding the losses external to the feed and the peak ef-

ficiency was found to be 55%, which corresponds to 65% theoretical

ef ficiency, calculated using the feed radiation patterns. For furthereval-

uation, a second feed for operation at 6 GHz was also designed, fab-

ricated and used with the same reflector. The measured patterns and

ef ficiencies were similar and omitted for brevity. As the feed produces

ellipticalbeam shapes, it is suitableas a feed forilluminating a reflector

with elliptic aperture shape. Note also that as Fig. 5 shows, the feed ismore suitable for a reflector with larger f/D of 0.375.

ACKNOWLEDGMENT

The authors would like to thank C. Smit for the fabrication of the

antenna and B. Tabachnick for the antenna radiation pattern measure-

ments.

R EFERENCES

[1] A. D. Olver,P. J.B. Clarricoats,A. A.Kishk, and L.Shafai , Microwave Horns an d Feeds, ser. 39. London, U.K.: Institute of Electrical Engi-neers, 1994.

[2] P. J. B. Clarricoats and A. D. Olver , Corru gated Horn s for Microwave

Antennas. London, U.K.: Peter Peregrinus, 1994.[3] G. L. James and D. P. S. Malik, “Towards the theoretical design of splash-plate feeds,” Electron. Lett., vol. 11, no. 24, pp. 593–594,1975.

[4] P. Newham, “A high ef ficiency splash plate feed for small reflector antennas,” in Proc. IEEE Antennas Propag. Int. Symp., 1985, pp.420–423.

[5] P.-S. Kildal and S. A. Skyttemyr, “Dipole-disk antenna with beam-forming ring,” IEEE Trans. Antennas Propag., vol. 30, no.4, pp. 529–534, 1982.

[6] C. C. Cutler, “Parabolic-antenna design for microwaves,” Proc. IRE ,vol. 35, no. 11, pp. 1284–1294, 1947.

[7] G. T. Poulton and T. S. Bird, “Improved rear-radiating waveguide cupfeeds,” in Proc. IEEE Antennas Propag. Int. Symp., Mill Valley, CA,1986, vol. 1, pp. 79–82.

[8] P.-S. Kildal, “The hat feed: A dual-mode rear-radiating waveguide an-tenna having low cross polarization,” IEEE Trans. Antennas Propag.,

vol. 35, no. 9, pp. 1010–1016, 1987.[9] J. Hansen, A. A. Kishk, P.-S. Kildal, and O. Dahlsjo, “High perfor-mance reflector hat antenna with very low side lobes for radio-link applications,” in Proc. Antennas Propag. Soc. Int. Symp., 1995, vol. 2, pp. 893–896.

[10] D. M. Pozar and D. Schaubert , Microstrip Antennas: The Analysis and Design of Microstrip Antennas and Arrays. London, U.K.: Instituteof Electrical Engineers, 1994.

[11] P. S. Hall and C. J. Prior, “Microstrip feeds for prime focusfed reflector antennas,” Proc. Inst. Elect. Eng., vol. 134, no.2, pp. 185–193, 1987.

[12] A. A. Kishk and L. Shafai, “Optimization of microstrip feed geometryfor prime focus reflector antennas,” IEEE Trans. Antennas Propag.,vol. 37, no. 4, pp. 445–451, 1989.

[13] N. Kaneda, W. R. Deal, Y. Qian, R. Waterhouse, and T. Itoh, “A broad- band planar quasi-Yagi Antenna,” IEEE Trans. Antennas Propag., vol.50, no. 8, pp. 1158–1160, 2002.

[14] G. Zheng, A. A. Kishk,A. W. Glisson, andA. B. Yakovlev, “Simplifiedfeed for modified printed Yagi antenna,” Electron. Lett., vol. 40, no. 8, pp. 464–466, 2004.

[15] G. Zheng, A. A. Kishk, A. B. Yakovlev, and A. W. Glisson, “A broad band printed bow-tie antenna with a simplified feed,”in Proc. Antennas Propag. Society In t. Symp. , CA, Jun. 2004, vol. IV, pp. 4024–4027.

[16] A. A. Eldek, A. Z. Elsherbeni, and C. E. Smith, “Wideband modified printed bow-tie antenna with single and dual polarization for C andX-band applications,” IEEE Trans. Antennas Propag., vol. 53, no. 9, pp. 3067–3072, 2005.

[17] Ansoft HFSS Version 12 [Online]. Available: http://www.ansoft.com[18] C. A. Balanis , Antenna Theory: Analysis and Design, 2nd ed. New

York: Wiley, 1997.[19] S. Silver , Microwave Antenna Theory and Design. London, U.K.:

Peter Peregrinus Ltd., 1984.[20] P.-S. Kildal, “Factorization of the feed ef ficiency of paraboloids and

Cassegrain antennas,” IEEE Trans. Antennas Propag., vol. AP-33, no.

8, pp. 903–908, 1985.

Radiation by a Slotted Conducting Elliptic Cylinder

Coated by a Nonconfocal Dielectric

Biglar N. Khatir and Abdel R. Sebak

Abstract— The characteristics of a slot antenna on a perfectly conducting

elliptic cylinder coated by a nonconfocal dielectric are investigated ex-

perimentally. Tow prototypes of non-coated and dielectric-coated elliptic

slot antennas are designed, fabricated, and tested. The simulations and

measurements results of non-coated and nonconfocal coated slot antennas

are compared and discussed. It is found that the radiation patterns due to

coating material become more directive.

Index Terms— Elliptic cylinder, experiment, nonconfocal coated, slot an-

tenna.

I. I NTRODUCTION

Wireless communications technology is one of the most rapidly

growing fields. An antenna is a key element that makes wireless

communications possible. One of the most popular antennas is the slotantenna which is widely used in many wireless systems such as radar

and satellite communications, space vehicles, aircrafts, missiles, and in

standard desktop microwave sources for research purposes Depending

on the application, slot antennas are mounted on bodies which have

different shapes. The slotted elliptic cylinder is an attractive geometry

because of some advantages including extra design parameters and for

some applications where the elliptic cylinder provides a useful model

for the mounting body.

Generally, slot antennas mounted on aircrafts, space shuttles, and

missiles are coated by materials for different purposes. For example,

the slot antenna on the space shuttle is covered by heat-shielding tiles.

In some applications, the coated materials can protect slot antennas

from the oxidations or damages. Also, the electromagnetic properties

of (loaded and coated) materials can be used to further control the ra-

diated power as an extra design parameter. Therefore, extensive inves-

tigations are reported about the characteristics of slotted antennas on

elliptic [1]–[10] cylinders loaded and/or coated by confocal or noncon-

focal [9], [10] materials. The number of design parameters increases

when the coating is nonconfocal including uniform and non-uniform

coating of the slot antenna.

Some related experimental works are also reported in which the

cylindrical slot antennas are fabricated and tested [11]–[15]. However,

for those antennas the slots are mounted on rectangular or circular

cylinders. In this communication, we introduce a slot antenna in which

the slot is mounted on an elliptic cylinder with an extra degree of de-

sign parameters. In particular, design, fabrication, and testing of the

non-coated and dielectric-coated elliptic cylinder slot antennas are pre-sented. The simulations and measurements results of these antennas

are compared and discussed. The proposed antennas are very useful

in several aerospace and military communication systems and in fixed

stations for personal and beacons communication services where, for

Manuscript received March 03, 2012; revised June 02, 2012; accepted July02, 2012. Date of publication July 11, 2012; date of current version October 26,2012.

Theauthors arewith theDepartment of Electrical andComputerEngineering,Concordia University, Montreal QC, Canada (e-mail: [email protected];[email protected]).

Color versions of one or more of the figures in this communication are avail-able online at http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TAP.2012.2207938

0018-926X/$31.00 © 2012 IEEE



5434 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 60, NO. 11, NOVEMBER 2012

Fig. 1. Geometry of a non-coated elliptic cylinder slot antenna.

TABLE IDESIGN PARAMETERS FOR A NON-COATED ELLIPTIC SLOT A NTENNA at 10 GHz

example, power handling capability and rugged construction are pre-

ferred requirements.

II. DESIGN, FABRICATION AND TESTING

In analytical solutions for the axial slot antennas, it is generally as-

sumed that the line source and cylinders have infinite length and they

are uniform along the length [7]–[10]. However in practice, we deal

with the limited dimensions and the infinite length can be reduced to a

few times of . Therefore, to reduce the fabrication costs, dimensions

of geometries are estimated in theory. Then, simulation techniques are

used to have the accurate designs and optimize the antennas perfor-

mances. Using Ansoft’s HFSS Software [16], Fig. 1 shows the simu-

lated geometry of a non-coated elliptic slot antenna fed by a coaxial

line. The open-ended inner conductor of a coaxial line is located inside

the cylinder as a monopole, and the outer conductor is connected to

the cylinder. At 10 GHz, the coaxial line is located at distance 10 mm

from the bottom of cylinder and the monopole is placed on minor axis

parallel to the cylinder at distance 2 mm of its inner surface. The feed

point and monopole locations are optimized after many simulations to

find the minimum reflection power (or S11). The geometrical parame-ters for this design are given in Table I.

We use these parameters and some simple tools to fabricate this an-

tenna. A rectangular copper sheet with thickness 0.25 mm is used to

make an elliptic cylinder. A hole is made in this sheet which is lo-

cated at the width center and 10 mm to the length end. Then, this sheet

is carefully bended to make a slotted elliptic cylinder. A 90-degrees

connector is used and its inner conductor connected to the monopole

and outer one connected to the cylinder. The connector is placed at the

same hole location, so that, its inner conductor passed from the hole.

Fig. 2 shows photographs of the fabricated non-coated elliptic slot an-

tenna. After fabrication of slot antenna some measurements are done

and compared to the simulation results.

Fig. 3 shows the simulated and measured results for S11 of the non-

coated elliptic slot antenna. As shown in this figure reasonable agree-

ment is obtained with a slight shift in the resonance frequency and both

Fig. 2. Photographs of fabricated non-coated elliptic slot antenna.

Fig. 3. The simulation and measurement results of non-coated elliptic slotantenna.

resultshave almost the same 10 dB bandwidth. Fig. 4 shows thesimu-

lation and measurement radiation patternsof the non-coated elliptic slot

antenna. The main lobe of measurement result is in very good agree-

ment with the main lobe of simulation result. However, there are some

disagreements for side lobes and back lobe.

The effect of coating material on radiation pattern is measured using

partial coating geometry (same as Fig. 5) where Rogers’ standard

RT/duroid 5880 high frequency laminate is used. That is a double-side

copper clad laminate with thickness 1.575 mm and dielectric constant,

. A piece of this laminate is installed on elliptic slot antenna by tape, after removing the copper from both sides. The coated

dielectric covered slot and extended almost both sides of slot.

Fig. 6 shows the simulation and measurement results for S11 of the

partial coated elliptic slot antenna. We can see the effect of coating ma-

terial on S11 by comparison of the simulations and measurements re-

sults due to non-coated and partial coated elliptic slot antenna as shown

in Figs. 3 and 6. It is observable that the minimum values of the results

due to coated elliptic slot antenna occur at lower frequencies. This shift

for simulation result is more than the shift for measurement result.

Fig. 7 shows the corresponding simulation and measurement radia-

tion patterns of the partial coated elliptic slot antenna. Again, the main

lobe of measurement result is in very good agreement with the main

lobe of simulation result, and there are some disagreements for side

lobes and back lobe. By comparison of the results in Figs. 4 and 7, it

is observable that the radiation patterns due to partial coating become



IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 60, NO. 11, NOVEMBER 2012 5435

Fig. 4. Radiation patterns of non-coated elliptic slot antenna.

Fig. 5. Geometry of an elliptic cylinder slot antenna partial coatedby dielectric.

Fig. 6. The simulation and measurement results of partial coated elliptic slotantenna.

more directed to desire angle. The simulations results show that the

coated dielectric more affects on side lobes, while the measurements

results show it more affects on back lobe.

As shown in the results, there are some disagreements between the

simulations and measurements results. One reason for these disagree-

ments is the shape of elliptic cylinder. The elliptic cylinder is hand

made using copper sheet and some simple tools trying to make an exact

shape. However, it is not made as a perfect elliptic cylinder. A second

reason is the installation of monopole. The location of monopole inside

Fig. 7. Radiation patterns of partial coated elliptic slot antenna.

the cylinder is very important. By many simulations it is found that the

results are very sensitive to the location of monopole. Also, it must be

exactly parallel to the cylinder. The monopole is installed by a 90-de-gree connector. Since the surface of cylinder is not flat, installation of

connector was not an easy task. Therefore, the location and orientation

of monopole were not easily controllable. The third reason which may

applicable for dielectric-coated antenna is the installation of coating

material. The coating dielectric is installed by a tape which may result

in a small gap between the cylinder and dielectric.

III. CONCLUSION

Prototypes of non-coated and dielectric-coated elliptic slot antennas

are designed, fabricated, and tested. The main lobes of measured radi-

ation patterns are in very good agreement with the main lobes of sim-

ulated radiation patterns. However, there are some disagreements for

side lobes and back lobes which may be due to the imperfect fabrica-tion of slot antennas.

R EFERENCES

[1] M. Hussein, A. Sebak, and M. Hamid, “Scattering and coupling prop-erties of a slotted elliptic cylinder,” IEEE Trans. Elect. Compat., vol.36, no. 1, Feb. 1994.

[2] T. Hinata and H. Hosono, “Scattering of electromagnetic waves by anaxially slotted conducting elliptic cylinder,” in Proc. IEEE MMET’96 ,Lviv, Ukraine, Sep. 10–13, 1996, pp. 28–31.

[3] J. H. Richmond, “Axial slot antenna on dielectric-coated ellipticcylinder,” IEEE Trans. Antennas Propag., vol. 37, no. 10, Oct. 1989.

[4] M. I. Hussein and A. K. Hamid, “Radiation by axial slot elliptical an-tenna coated by a lossy dielectric material,” in Proc. IEEE EMC’03,Istanbul, May 16–16, 2003, pp. 146–149.

[5] M. I. Hussein and A. K. Hamid, “Radiation characteristics of axialslot antenna on a lossy dielectric-coated elliptic cylinder,” Can. J.

Phys., vol. 82, pp. 141–149, 2004.[6] A. K. Hamid, “Study of lossy effects on the characteristics of axi-

ally slotted circular or elliptical cylindrical antennas coated with meta-materials,” IEE Proc. Microw. Antennas Propag., vol. 152, no. 6, pp.485–490, Dec. 2005.

[7] B. N. Khatir and A. Sebak, “Coupling properties of slotted ellipticcylinder coated by dielectric/metamaterials,” presented at the URSIGA08, Chicago, IL, Aug. 7–16, 2008.

[8] B. N. Khatir and A. R. Sebak, “Slot antenna on a conducting ellipticcylinder coated by chiral media,” Electromagnetics, vol. 29, no. 7, pp.522–540, 2009.

[9] H. A. Ragheb, A. Sebak, and L. Shafai, “Radiation by axial slots on adielectric-coated nonconfocal conducting elliptic cylinder,” IEE Proc.

Microw. A ntennas Propag., vol. 143, no. 2, Apr. 1996.

[10] B. N. Khatir and A. R. Sebak, “Slot antenna on a conducting ellipticcylinder coated by nonconfocal chiral media,” in Proc. Progr. Electro-

magn. Res., PIER 93, 2009, pp. 125–143.



5436 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 60, NO. 11, NOVEMBER 2012

[11] S. J. Tetenbaum, “Experimental VSWR’s and radiation patterns of anaxial rectangular slot on conducting cylinders of varying curvature,”

IEEE Trans. Antenna s Propag., pp. 835–837, Nov. 1974.[12] Z. Wasim, R. A. Bhatti, and J. K. Kayani, “Design, fabrication and

testing of a millimeter wave slotted waveguide antenna,” in Proc. Int.

Bhurban Conf. on Applied Sciences & Technology, Islamabad, Pak-istan, Jan. 8–11, 2007, pp. 55–57.

[13] J. D. Kraus and R. J. Marhefka , Antennas for All Applications, 3rded. New York: McGraw-Hill, 2002.

[14] J. Hirokawa, S. I. Sumikawa, M. Ando, and N. Goto, “Analysis and de-sign of a circumferential wide slot cuton a thin cylinder formobile basestation antennas,” in Proc. IEEE AP-S, , Ann Arbor, MI, Jun. 28–Jul.2 1993, pp. 1842–1845.

[15] D. H. Shin andH. J. Eom, “Radiation from narrowcircumferential slotson a conducting circular cylinder,” IEEE Trans. Antennas Propag., vol.53, no. 6, Jun. 2005.

[16] Ansoft’s HFSS, Version 10.1.2 Ansoft Corporation. Pittsburg, PA,Build 28, Sep. 2006.

Complexity Versus Reliability in Arrays of

Reconfigurable Antennas

J. Costantine, Y. Tawk, and C. G. Christodoulou

Abstract— This communication discusses the complexity and reliability

of switch reconfigurable antenna arrays using frequency-dependent graph

models. Several graph models represent array configurations at various

frequencies. The correlation and the inverse proportionality between the

arrays’ complexity and reliability are derived and proven. A process for

prioritizing the variousantenna configurations to improvethe overallarray

performance is also discussed. Different examples are given to validate the

formulations and prove the concept.

Index Terms— Complexity, graph models, reconfigurable antenna

arrays, reliability.

I. I NTRODUCTION

A graph is used as an abstract model to represent physical structures

[1]. Graph modeling reconfigurable antennas transform them into soft-

ware accessible devices [2], [3] that are easy to optimize, control and

automate. In addition to these functionalities the modeling of reconfig-

urable antennas using graphs leads to a redundancy reduction approach

that eliminates unnecessary components from the antenna structure.

Thus graph models are utilized to formulate a reconfigurable antenna’s

complexity [4]. The overall complexity of an antenna system increases

with the number of p-i-n diodes [5]–[7], RF MEMS [8]–[10], varactors

[11]–[13] or optical switches [14], [15] employed.

In this communication we expand previous formulations done onsingle element reconfigurable antenna [4] to evaluate the complexity

Manuscript received August 04, 2011; revised December 09, 2011; acceptedJune 18,2012. Date of publicationJuly 10,2012; date of current version October 26, 2012.

J. Costantine is with the California State University Fullerton, EE, Fullerton,CA 92831 USA (e-mail: [email protected]).

Y. Tawk is with the Electrical and Computer Engineering Department, NotreDame University, Louaize, Lebanon (e-mail: [email protected]).

C. G. Christodoulou is with the Department of Electrical and Computer En-gineering, University of New Mexico, Albuquerque, NM 87106 USA (e-mail:[email protected]).

Color versions of one or more of the figures in this communication are avail-able online at http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TAP.2012.2207665

Fig. 1. A two element reconfigurable antenna array.

and reliability of reconfigurable antenna arrays using graphs. This is

essential to address the continuous functioning of these arrays in un-

known conditions and environments.

The graph modeling of reconfigurable antenna arrays is presented in

Section II. Section III discusses the use of graph models to formulatethe arrays’ complexity, the impact of the complexity on the reliability of

switch reconfigurable antenna arraysand theconfiguration complexity.

A technique is proposed in Section III-C to improve the performance of

reconfigurable antenna arrays. This technique is based on rearranging

antenna configurations to ensure a higher reliability. The improvement

that such rearrangement introduces to the design ef ficiency and opera-

tion is discussed. The practicality and design aspects are discussed in

Section IV while Section V presents concluding remarks.

II. THE GRAPH MODELING OF ARRAYS OF

R ECONFIGURABLE A NTENNAS

Graphs are symbolic representations of relationships between dif-ferent components of a system. They are mathematical tools used to

model complex systems in order to organize them and improve their

status. A graph is defined as a collection of vertices that are connected

by lines called edges [1]. A graph can be either directed or undirected.

The edges in a directed graph have a certaindetermineddirection, while

this is not the case in an undirected graph. Vertices may represent phys-

ical entities while the edges between them in the graph represent the

presence of a function resulting from connecting these entities. In a

switch reconfigurable antenna, an edge represents the connection that

occurs once a switch is activated. Edges may have weights associated

with them. These weights represent costs or benefits that are to be min-

imized or maximized [1].

A graph model of an array of reconfigurable antennas is very dif-

ferent than that of a single reconfigurable element. In an antenna arrayall elements are fed through a feeding network and are placed at cer-

tain spacings from each other [16], [17]. As an example, let us con-

sider the antenna array shown in Fig. 1. The array is composed of three

layers. The bottom layer constitutes a common ground plane for the

different elements. The middle layer constitutes the substrate Taconic

TLX with a dielectric constant and height 2.9 mm. The

upper layer constitutes the different element patches as well as the cor-

porate feeding network. Each element is a rectangular patch with 2

rectangular slots dividing it into 2 sections connected constantly. Two

switches are placed in each element to bridge over the upper and lower

part of the slots. The end-points of each switch are indicated by the

nodes ((1)) where i refers to the element number and j refers

to the switch position. For example represent the end-points

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Radiation by a Slotted Conducting Elliptic Cylinder