Directional pattern analysis of a linear phased antenna

74 Ad ances in Elec ical and Elec onic Enginee ing DIRECTIONAL PATTERN ANALYSIS OF A LINEAR PHASED ANTENNA ARRAYS J. Ha ing 1) , N. Maje 2) , R. H onec 3) Dep . o Telecommunica ions and Mul imedia, Facul y o Elec ical Enginee ing, Uni e si y o Žilina, Uni e zi ná 1, 010 26 Žilina, Slo ak Republic mail: 1) ha ing@ el.uniza.sk, 2) maje @ el.uniza.sk, 3) h onec@ el.u c.sk Summa y: An an enna a ay is a sys em compound om simply adia o s (dipoles, mic os ip an ennas), ha oge he o m desi ed adia ion pa e n. Phased a ay an ennas consis o mul iple s a iona y an enna elemen s, ha a e ed cohe en ly and use a iable phase o ime-delay con ol a each elemen o scan a beam o gi en angles in space. Va iable ampli ude con ol is some imes also p o ided o an enna pa e n shaping. 1. INTRODUCTION An an enna a ay is a sys em compound om simply adia o s (dipoles, mic os ip an ennas), which oge he o m desi ed adia ion pa e n. The main emphasis is on he wid h, con ou and di ec ion o o ien a ion du ing o m a adia ion pa e n o an enna sys em. By he assis ance his way o c ea ed pa e ns i is possible o ou a adia ion ene gy o an enna sys em in o deside a i e di ec ion, educe in e e ence and inc ease e iciency en i e ansmission. In p ac ice a e known se e al echniques ha can o m adia ion pa e n o an enna sys em. The a icle deals wi h desc ip ion o echnique based on eeding pa icula elemen s an enna sys em by di e en phase signals. [1] 2. LINEAR ANTENNA ARRAY An an enna a ay is a con igu a ion o indi idual adia ing elemen s ha a e a anged in space and can be used o p oduce a di ec ional adia ion pa e n. Single-elemen an ennas ha e adia ion pa e ns ha a e b oad and hence ha e a low di ec i i y ha is no sui able o long dis ance communica ions. A high di ec i i y can be s ill achie ed wi h single elemen an ennas by inc easing he elec ical dimensions (in e ms o wa eleng h) and hence he physical size o he an enna. An enna a ays come in a ious geome ical con igu a ions, he mos common being; linea a ays (1D). A ays usually employ iden ical an enna elemen s. The adia ing pa e n o he a ay depends on he con igu a ion, he dis ance be ween he elemen s, he ampli ude and phase exci a ion o he elemen s, and also on he adia ion pa e n o indi idual elemen s. A uni o m linea a ay consis s o equispaced elemen s, ha a e ed wi h cu en o equal magni ude (i.e. wi h uni o m weigh ing) and can ha e p og essi e phase-shi along he a ay. [2], [3] The e is displayed schema ic diag am o linea an enna a ay in he Fig. 1. [4] Fig. 1. Schema ic diag am o linea an enna a ay The uni o m linea a ay shown in he Figu e 1 consis s o N elemen s equally spaced a dis ance d. The A ay ac o o a linea a ay o N pa allel elemen s is gi en by he ela ion (1). πθ ϕθ ϕθ ≤≤      +      + =0, cos. 2 1 sin cos. 2 sin 1 kd kd N N AF , (1) whe e: - N is he numbe o elemen s - d is he in e elemen space -  is he angle om he a ay axis -  is he phase shi Symbol k ep esen s wa ele numbe . The wa ele numbe is gi en by he ela ion (2). λ π 2 =k , (2) Whe e  is he wa eleng h. Di ec ional pa e n analysis o a end- i e an enna a ays 75 3. LINEAR PHASED ANTENNA ARRAY STEERING Phased a ay an ennas consis o mul iple s a iona y an enna elemen s ha a e ed cohe en ly and use a iable phase o ime - delay con ol a each elemen o scan a beam o gi en angles in space. Va iable ampli ude con ol is some imes also p o ided o pa e n shaping. A ays a e some imes used in place o ixed ape u e an ennas ( e lec o s, lenses), because he mul iplici y o elemen s allows mo e p ecise con ol o he adia ion pa e n, hus esul ing in lowe sidelobes o ca e ul pa e n shaping. Howe e , he p ima y eason o using a ays is o p oduce a di ec i e beam ha can be eposi ioned (scanned) elec onically. Al hough a ays wi h ixed (s a iona y) beams and mul iple s a iona y beams will be discussed in his ex , he p ima y emphasis will be on hose a ays ha a e scanned elec onically. [4] The e is displayed schema ic diag am o linea phased an enna a ay beam - s ee ing in he Figu e 2. Fig. 2. Schema ic diag am o phased linea an enna a ay beam - s ee ing The phase shi  be ween wo successi e elemen s is cons an and is called phase-inc emen . We can de i e hese o mulas om Figu e 2: ,cos.dx θ = == = (3) , x λ ϕ π = == = 2 (4) ,cos.d θ λ π ϕ 2 = == = (5) Fo mula 3 desc ibes he phase shi dependence on angle o main lobe o ien a ion. [5] 4. LINEAR PHASED ANTENNA ARRAY SIMULATIONS Phased an enna a ay simula ions a e c ea ed by he help o p og am Linea An enna A ays Simula o . This p og am was c ea ed in Bo land Delphi 7. The a ay ac o plo in he Figu e 3 shows dependency on he elemen spacing. As we can see om he Figu e 3 he an enna pa e n is changed by he a ay elemen spacing inc easing. d = 1/4  d = 1/2  Fig. 3. Se o a ay ac o plo s o in luence o mu ual elemen ’s dis ance simula ion Pa ame e s o simula ions we e N =16, = 2 GHz,  = 0°. Dis ance o elemen s d was changed om 1/4  o 1/2 . Figu e 4 shows ha he an enna pa e n wid h is no only dependen on he elemen spacing bu also on he numbe o elemen s. I can be seen om Figu e 4. he beam wid h inc eases as he numbe o elemen s in he a ay inc eases. Please no e ha he elemen spacing is kep cons an in bo h he cases. 76 Ad ances in Elec ical and Elec onic Enginee ing N = 2 N = 8 N = 32 Fig. 4. Se o a ay ac o plo s o in luence o elemen s numbe inc ease simula ion Pa ame e s o simula ions we e d = 1/2 , = 2 GHz,  = 0°. Numbe o elemen s N was changed (N = 2, 8, 16). The e is shown dependency be ween an enna pa e n o ien a ion and phase shi in Figu e 5.  = 60°  = 120°  = 180° Fig. 5. Se o a ay ac o plo s o phase shi change simula ion Pa ame e s o simula ions we e d = 1/2 , = 2 GHz, N = 16. Phase shi  was changed ( = 60°, 120°, 180°). As shown in Figu es 6 and 7, an enna pa e n wid h is he same i numbe o elemen s inc eases and elemen spacing is dec eases. Di ec ional pa e n analysis o a end- i e an enna a ays 77 A he same ime numbe o elemen s inc eases om 10 o 20 elemen s and elemen spacing is dec eases om d = 1/2 o d = 1/4 and beam wid h does no change. Fig.6 . Rela ionship be ween numbe o elemen s and he elemen spacing, d = 1/4, N=20 Fig.7. Rela ionship be ween numbe o elemen s and he elemen spacing, d=1/2, N=10 Pa ame e s o simula ions we e = 2 GHz, =0°. 5. CONCLUSION In his pape we desc ibe linea phased an enna a ay heo y, simula e his sys em and desc ibe a ay ac o . Phased an enna a ay simula ions a e c ea ed by he help o p og am Linea An enna A ays Simula o . This p og am was c ea ed in Bo land Delphi 7. The inal esul s a e desc ibed in Figu es 3, 4, 5, 6, 7. As we can see om he Figu es 3, 4, 5, 6, 7 he an enna pa e n wid h is no only dependen on he elemen spacing and on equency bu also on he numbe o an enna a ay elemen s. We can change an enna pa e n o ien a ion by phase shi a ia ion. Acknowledgemen The wo k on his pape was suppo ed by he g an VEGA 1/4067/07 o Scien i ic G an Agency o he Slo ak Republic. REFERENCES [1] HARING, J., MAJER, N., POLOHA, P., HRONEC, R.: A Mic os ip Phase Shi e as an D i en Elemen o Dynamic Phased A ay. Science & Mili a y No.2, Vol.2/2007, pp.68- 71. [2] ORFANIDIS, J.: Elec omagne ic Wa es and An ennas. USA, 2008. [3] Flo ida S a e Uni e si y.: Elec onic Theses and Disse a ions. USA, 2008, www.e d.lib. su.edu [4] MAILLOUX, R.: Phased A ay An enna Handbook. A ech House, No wood, 2005. [5] WOLFF, CH.: Rada g undlagen. Be lin, 2008, www. ada u o ial.eu