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Research of Design Methods of Antennas Based on

Curvilinear Transmission Slotline

Oleksiy Liske

Abstract - principles of design, feature of constructions ofantennas based on curvilinear transmission slotline surveyed.Results of development of mathematical models of theseantennas are analysed.

Keywords - transmission slotline, microstrip antenna.

I. INTRODUCTION

Antennas based on transmission slotline (ATSL) are knownsince 1963. They are used in many antenna systems (AS),such as: the AS of direction findings of objects, modemtelecommunication systems (Radiointemet), onboard AS ofaircrafts and ground transport, AS of a GPS navigationsystems. Wide use ofATSL is caused by its advantages: smallsizes, an possibility of electric scanning of radiation pattem,work both with linear and circular polarization, a possibilityof designing arrays of elementary radiators based ontransmission slotline.

II. PRINCIPLES OF CONSTRUCTION OF ATSL

The first ATSL has been designed for use as the onboardantenna of the plane [I]. In a metal surface of the plane a holerectangular or of any other suitable shape is cut. In this hole ismounted a smaller metal sheet of the relevant size in such away that insulated gap is of uniform width along perimeter ofa sheet. Such antenna may be fed by coaxial cable with oneconductor of the cable connected to the inner metal sheet, andother conductor of the cable connected to the outer metallicsurface of the plane. The radiation properties of such anantenna depend upon the dimensions of the structure of theantenna: width and length of radiating element and upon thepoint at which the coaxial feeder is connected.

If radiating element has a vertical axis of symmetry and thefeeder connection is made along the vertical axis ofsymmetry, the structure will radiate vertically polarizedwaves.

So-called ,,coplanar stripline antenna" [2] differs fromprevious in way of feeding: electrical signals are fed to theantenna with help of coplanar stripline. A number ofrectangular slot elements forms an antenna array, that fed withhelp of system of coplanar striplines.

Coplanar stripline antenna has several advantages: lowlosses, low mutual coupling, high gain, good variation inachievable impedance levels.The following antenna is intended for receiving signal of

GPS system [3]. The path of slotline forms some U-shapedprojections, which can be 3-5. For feeding antenna used metalstrip line, which is between two ground planes in one ofwhich slotline is cuted. If strip line is on axis of symmetry ofslotline figure, the antenna can be used for linear polarization.Circular polarization, which is necessary for GPS signalreceiving, can only be achieved if the symmetry of thegeometry is broken, i.e. if strip line is displaced from axis ofsymmetry.

For integrate into user terminals of mobile radio telephonenetworks the annular-slot antenna is designed [4]. It has smallsize and may be easily integrated into the analogue processingcircuits of the terminals. A known solution provides for theuse of a planar antenna substrate which exhibits highpermittivity making it possible to reduce the size of themicrostrip antenna. However, the performance of such smallantennas may generally be regarded as insufficient on accountof poor efficiency of structural origin and they are moreoverrelatively expensive. To obtain an appreciable size reductionwith a standard printed substrate is possible with help ofdeforming of slotline shape. In zones in which the electricfield is a minimum the slot annulus is deformed asindentations, so as to exhibit a lengthening of the slotperimeter with respect to an annular slot of correspondingcircular form, without surface extension of the substrate zonewherein the slot is made.

It is possible to provide circular polarization in the waynotching the square radiating elements portions at two comersopposing in one diagonal direction [5], [6].The problem development two-frequency antennas for use

in wireless communication systems is actual. Conventionaldual band slot antenna comprises two closed-circle slots. Forfeeding antenna used two coaxial cables, the first coaxialcable has an inner core wire and an outer shield respectivelysoldered to two sides of the first slot, and the second coaxialcable - respectively soldered to two sides of the second slot.With such a structure, the antenna can operate in two differentfrequency bands.

However, since this arrangement requires two coaxialcables, such dual band slot antenna will occupy moreinstallation space. Furthermore, the second coaxial cable addsmanufacturing cost.

Oleksiy Liske - Lviv Polytechnic National University, S. BanderyStr., 12, Lxiv, 79013, UKRAiNE.

TCSET'2006, February 28-March 4, 2006, Lviv-Slavsko, Ukraine

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The antenna, which represents two slots, which run parallelwith each other, has no these disadvantages. These slots havedifferent dimensions and can operate in different frequencybands [7]. The coaxial cable has an inner core wire and anouter shield respectively soldered to the antenna at an outerside of the first slot and at an opposite, outer side of thesecond slot. The coaxial cable acts as a common feed line ofthe first and second slots. To adapt a dual band slot antenna todifferent installation spaces, the profile of the antenna can bechanged by changing the profile of slots.

II. METHODS OF MATHEMATICAL SIMULATION OFATSL

1. Excitation ofATSL with the help of a resonator.

Radiating system of ATSL represents all surface of theantenna, on which electric (outside of the slot) and magnetic(in the slot) currents are flowing [8]. It is possible to replacethe curvilinear slot which is in ideally conducting infinite thinsurface, neglecting as a first approximation electric currentsoutside of the aperture of the curvilinear slot, indefinitely thincurvilinear radiator of the same form, as the slot and the samedistribution of a voltage along a contour of the radiator.E and H plane radiation pattems of such antenna are

determined by a relationship:

Fq, (0,p) = JU(t)4(9,p,t)dt, (1)

where U(t) - distribution of a voltage along a slotlineradiator.

2. Excitation of ATSL in one point.It is possible to consider curvilinear radiator with arbitrary

shape as a long line. The feeding line is connected to the slotin some point, with a amplitude voltage in this point U0. In

another point slotline is loaded on resistance ZH . The voltage

variation along contour of the slot depends on resistance ZH,a normalized impedance and a point of resistance loading.Radiation properties are determined by formula (1).

3. Mathematical simulation with help of decompositionmethod.Methods of the analysis of radiation properties of ATSL,

above mentioned, do not take into account limitations of sizesof the shield in which slot radiator is. It is solved with the helpof a method of decomposition. The surface of the antennasubstituted by antenna array of linear radiators fed bytraveling wave [9]. For the analysis of linear radiators arraythe method of induced EMF was applied. The comparison ofresults of mathematical analysis and experimental resultsproved the adequacy of mathematical model and itsperspectivity.

III. CONCLUSION

Principles of construction of antennas based ontransmission slotline are surveyed. Antennas of this type areused in different modem telecommunication systems.Though they are widely used, principles of work and

potential possibilities are investigated insufficiently.

REFERENCES

[1] US 3,086,204 Patented Apr. 16, 1963. Island antennainstallation on aircraft. Andrew Alford, Winchester,Mass.

[2] US 4,063,246 Patented Dec. 13, 1977. Coplanar striplineantenna. John W. Greiser, Marina del Rey, Calif.

[3] EP 1 170 704 Al Portable access authorization device,GPS receiver and antenna. Benedikt Oswald, CH-8008Zurich.

[4] EP 1 271 693 Al Compact annular-slot antenna. ThomsonLicensing S.A. 92100 Boulogne-Billancourt (FR).

[5] EP 1 434 302 Al Annular-slot antenna. Satoru Komatsu,Wako-shi Saltana (JP).

[6] US 2005/0179593 Al Pub. Date: Aug. 18, 2005. Planeantenna and its designing method. Hideaki Oshima,Tatsuo Matsushita, Tokyo (JP).

[7] US 2003/0090426 Al Pub. Date: May 15, 2003. Dualband slot antenna with single feed line. Pei-Lun Sun,Hsin Kuo Dai, Chien-Hsun Huang, Tu-Chen (TW).

[8] ,J1.H'. BocKpeceHCbKHfi, C.A. KpeMeHeUbKHA, A.IO.FpHHeB, 1O.B. KOTOB, ABTOMaTH3HpOBaHHOenpoerTHpoBaHHe aHTeHH H ycTpoflcTB CBLI, M.: Pa,jio uCBM3b 1988.

[9] V.V.Goblyk, O.M.Liske, E.I.Yakovenko, The modeling ofplane curvilinear dipole antenna arrays. 5-th InternationalConference on Antenna Theory and Techniques. 24-27May, 2005. Kyiv, Ukraine.

TCSET'2006, February 28-March 4, 2006, Lviv-Slavsko, Ukraine