Jounal of lectomagnetic Analysis and Applications, 01, 4, 35-4 http://dx.doi.og/10.436/jemaa.01.46033 Published Online June 01 (http://www.scirp.og/jounal/jemaa) 35 Analysis of the Radiation Resistance and Gain of Full-Wave Dipole Antenna fo Diffeent Feeding Design Yahya S.. Khaisat 1, Khedhe A. mood, Anwa Al-Mofleh 3 1 lectical and lectonics Depatment, Al-uson Univesity College, Al-Balqa Applied Univesity, Ibed, Jodan; College of Technology and Innovation (UCTI), Asia Pacific Univesity, Technology Pak Malaysia (TPM), Kuala Lumpu, Malaysia; 3 lectical and lectonics Depatment, Amman Faculty of ngineeing, Al-Balqa Applied Univesity, Amman, Jodan. mail: yahya@huson.edu.jo, d.khedhe@ucti.edu.my, anwa1971@yahoo.com Received Apil 4 th, 01; evised May nd, 01; accepted May 1 th, 01 ABSTRACT This pape demonstates the analysis of antenna patten and gain fo diffeent designs of full-wave dipole antenna feeding techniques. Seven such techniques wee studied and analyzed; symmetical dual feeding in phase, symmetical dual feeding out of phase, asymmetical dual feeding in phase, asymmetical dual feeding out of phase, symmetical tiple feeding in phase and symmetical tiple feeding out of phase. Symmetical dual feeding in phase poduced high gain as compaed to the single and cente-fed antennas. An impovement of about 3 to 3.5 db was achieved compaing to cente tap fed and off cente fed. It was found that an asymmetical dual feeding in-phase povides good pefomance, consideing the diectivity, patten, and input impedance. A.46 db gain has been obtained. It was found that a symmetical tiple feeding povides an oveall best pefomance with espect to gain, adiation patten, beam width and input impedance. Keywods: Full-Wave Dipole Antenna; Radiation Patten; Gain; Double Feeding and Tiple Feeding 1. Intoduction Accoding to the thin wie appoximation and Maxwell quations, the z-component of the adiated electic field fo infinitesimal dipole is shown in Figue 1 and depicted in quation (1) [1,]. d jt jzcos c j6 I z sine dz (1) A Matlab compute code was witten to simulate the patten pefomance of the antenna at any scan angle. This pogam can be used to facilitate futhe study of the antenna. The computed pattens fom this pogam ae compaed to the measued pattens as a means fo validating the model [3]. Some special attibutes of the softwae ae: the simulation though the staight calculation of the fields, the analysis of sensitivity and the behavio against fequency changes and the use of the cuent distibution on the dipole calculated by the Method of Moments, King s Appoximation, and allen s solution. In this simulation, it was assumed that the dipole consists of two collinea wies sepaated by a small gap whee the excitation is applied. Ideally, the values of gap and the diamete of the wies have to be zeo but pactically it can be consideed as a continuous a thin filament. In the fa zone egion, the electic field was poduced by the dipole consideing an ideal sinusoidal cuent distibution. In [4] diffeent equations fo the cuent distibution wee obtained. These equations wee used to deive the adiation patten of Antenna A1, A, B1, B, C1, C, and C3. Figue 1. Coodinate system used with antennas. Copyight 01 SciRes. JMAA
36 Analysis of the Radiation Resistance and Gain of Full-Wave Dipole Antenna fo Diffeent Feeding Design. Radiation Patten of Ou Designed Antennas.1. Antenna A1 The feeding aangements fo the symmetical dual feeding in phase (Antenna A1) is shown in Figue. xpession of the cuent distibution is as given below: sin L I I, 0 max z z () sin L I I, 0 max z z (3) whee π. Substituting quations () and (3) in (1), yields 0 l sin z e l l 0 l sin j zcos dz j zcos z e z d (4) Using quation (5) solve the quation (4) gives quation (6) x e sin x dx x e sin xcosx jt (5) c jπ60i cos l cos cos l (6) sin In this study L = λ = 1 m. Substituting λ = 1 and simplifying quation (6) yields diective adiation patten on the boadside of the plane of the antenna. The two feeding points ae in-phase, and that leads the antenna to give a high pofile of gain due to cuent distibution that has two maximum peaks. The maximum peaks ae positive, esulting in adiation patten to be split into two main lobes... Antenna A The feeding aangements fo symmetical dual feeding out of phase (Antenna A) is shown in Figue 4. The mathematical expession of the cuent distibution of this antenna is shown in quations (9) and (10) I z L sin z, L z 0 (9) L I z z z sin, 0 L (10) quations (9) and (10) epesent the cuent distibution ove the thee ams of Antenna A. Substituting quations (9) and (10) in (1), yields Figue. Feeding aangements fo symmetical dual feeding in Phase antenna. jt c j60i cosπ cos 1 sin (7) jt c j60i cosπ cos 1 π sin quations (7) and (8) epesent the electic and magnetic field components of Antenna A1. The equation of the adiation patten fo Antenna A1 is depicted in quation (7) and fom this equation; the adiation patten can be plotted as shown in Figue 3. The dual feeding technique has given a adiation patten, which is diffeent fom those of cente fed and off cente fed due to the phase evesal at the midpoint of Antenna A1, and this technique splits the adiation patten into two main lobes, which contibute to a highly (8) Figue 3. Radiation patten of antenna A1. Figue 4. Feeding aangements fo symmetical dual feeding out of phase antenna. Copyight 01 SciRes. JMAA
Analysis of the Radiation Resistance and Gain of Full-Wave Dipole Antenna fo Diffeent Feeding Design 37 jt c 0 jπ60i l j zcos sin z e d l z (11) l l j zcos sin z e dz 0 Solving quation (11) using Math Cad and Matlab; we have quations (1) and (13). quations (1) and (13) epesent the electic and magnetic field components of Antenna A. jt c j60i sin π cos sin jt c j60i sin π cos π. sin (1) (13) Figue 5 shows the adiation patten of Antenna A. The technique of dual feeding out-of-phase poduced the same adiation patten as unbalanced single feeding, but still Antenna A gives high pefomance as compaed to single cente-fed, o off-cente fed antenna. The two feeding points ae out-of-phase, which makes the antenna to change its chaacteistics to give lowe pofile of gain as compaed to Antenna A1, which can be attibuted to cuent distibution. This cuent distibution has two peaks, one is positive and the othe is negative and that led the adiation patten to be split into fou lobes. Accoding to ARRL, the signal stength depends on how the signals, adiated fom the antenna s electons, add up in the obseve s antenna. Some of the signals would add up and the est cancel out. The quantity of adding and canceling depends on the phase of the eceived signals and thei elative amplitudes. Antenna A has the same chaacteistics like that of a full-wavelength antenna as composed of two half-wavelength antennas with identical adiating popeties. One excited positively and the othe, negatively, o 180 out-of-phase, it exhibits maxima along the positive and negative z-axis, and nulls, in the x-y plane whee the contibutions fom the two elements cancel out because they ae out of phase. The adiation patten of an antenna A shows what signal stength would be eceived by changing the polaity of the feeding..3. Antenna B1 The feeding aangements fo the asymmetical dual feeding out of phase (Antenna B) is shown in Figue 6. The quation fo measued cuent distibution can be expessed as shown below: L L L Iz 0.5cos cos z, z (14) Substituting quation (14) in quation (1), yields jt c jπ60i sin l L jzcos 0.5cos cosze dz l (15) Solving quation (15), we have quations (16) and (17) which epesent the electic and magnetic field components of Antenna B1 espectively. In asymmetical dual feeding configuation, one feed- jt c sin π cos cos sin π cossin 0.5 sin cos j π t c sin π cos cos sin π cos sin 0.5 sin cos Figue 5. Radiation patten of Antenna A. (16) (17) Figue 6. Feeding aangements fo asymmetical dual feeding in phase antenna. Copyight 01 SciRes. JMAA
38 Analysis of the Radiation Resistance and Gain of Full-Wave Dipole Antenna fo Diffeent Feeding Design ing point is located at quate wavelength away fom the cente and the othe is located at the cente of the fullwave dipole. The cuent distibution has thee such peaks. Two negative peaks flowing in same diection ae inphase, while the main one in the middle, flowing in opposite diection and is out-of-phase. Figue 7 shows the adiation patten of Antenna B1, which consists of fou main lobes, and two gating small lobes due to effect of the cuent stoed at the end of the antenna causing eactance impedance at the feeding points. Willad, stated that the value of the feed point eactance is not as accuate as the feed point esistance. The fou lobes in measued patten ae not shown, due to the pecentage of eo. The standad dipole has a ated accuacy of 0.5 db, which was tanslated into an accuacy of 19% [5]. oweve, it is consistency among the measued, simulated, and theoetical analyses. In Matlab simulato, the diamete was assumed to be vey small (Zeo). In this simulation, the diamete is 0.0 λ, and the diamete in King s appoximation is 10 4 λ. Fo this eason, a slight discepancy was noted between simulated and theoetical analyses..4. Antenna B The feeding aangements fo the asymmetical dual feeding out of phase (Antenna B) is shown in Figue 8. The quation fo measued cuent distibution can be expessed as shown below: L L L Iz0.1cos cos z, z (18) Substituting quation (18) in quation (1), yields jt c jπ60i sin l L j zcos 0.1cos cos π ze dz l (19) jt c sin π cos cos sin π cossin 0.1 sin cos jt (0) c (1) sin π cos cos sin π cossin 0.1 sin cos Fo Antenna B, the equation of the adiation patten has been split into fou main lobes and two mino small lobes because the cosine coefficient facto M, is 0.1, leading the equation of the cuent distibution to have two peaks in negative zone and one peak in positive zone. The capacitive chaacteistics inceased due to change in polaity of the feeding applied to Antenna B. The gain has dopped due to cuent distibution chaacteistics. The adiation patten is split into fou lobes and two nulls due to the stoed chage at the ends of the Antenna B. Figue 9 shows the adiation patten of Antenna B. Figue 7. Radiation patten of Antenna B1. Figue 8. Feeding aangements fo asymmetical dual feeding out of phase antenna. Figue 9. Radiation patten of Antenna B. Copyight 01 SciRes. JMAA
Analysis of the Radiation Resistance and Gain of Full-Wave Dipole Antenna fo Diffeent Feeding Design 39 Tang and Gunn, showed that the adiation patten of an antenna with lage capacitive load impedance changes in shape when the cuent distibution changes in shape and its peak moves away fom the feed points. The adiated powe density may fall into well-defined egions called lobes, sepaated by egions of low intensity called nulls. oweve, the nulls can only be seen fo some paticula diections [6]. Thee ae main lobes, which ae usually whee the desiable powe fom the antenna is diected, and side lobes whee the antenna sends adiated enegy. This enegy is egaded as wasted o may even intefee with othe tansmitting systems. It is possible to have moe than one main lobe having a given maximum value of gain. Fo example, a linea aay of dipoles can have main lobes 180 apat, and both having the same gain [7]..5. Antenna C1 The feeding aangements fo symmetical tiple feeding in phase (Antenna C1) is shown in Figue 10. The cuent distibution fo Antenna C1 can be expessed as in quations () and (3), whee M is the coefficient of cosine facto. M is vaiable depending on the method of feeding. Fo Antenna C1 the coefficient of cosine facto is equal to 1. sin L cos z I z z, L z 0 () L z L Izsin zcos, 0 z (3) Substituting quations () and (3) in quation (1), yields jt c sin (4) 1 L L j zcos 1 cos sin z e dz The evaluation of quation (4) yields jt c cosπ cossin cosπ cos 1 1 4cos sin (5) quations (5) and (6) epesent the electic and magnetic field components of Antenna C1 espectively. Figue 11 shows the adiation patten of Antenna C1..6. Antenna C The feeding aangements fo symmetical tiple feeding out of phase (Antenna C) is shown below in Figue 1. Fo Antenna C, the coefficient of cosine facto M is equal to 0.5. Thus, the equation of the cuent distibution fo tiple feeding Antenna C is expessed mathematically as given in quations (7) and (8). sin L 0.5cos z I z z, L z 0 (7) Figue 10. Feeding aangements fo tiple feeding full wave antenna. Figue 11. Radiation patten of antenna C1. j60i e 0 jt c π (6) cosπ cossin cos π cos 1 1 4cos sin Figue 1. Feeding aangements fo tiple feeding full wave antenna. Copyight 01 SciRes. JMAA
40 Analysis of the Radiation Resistance and Gain of Full-Wave Dipole Antenna fo Diffeent Feeding Design L z L Izsin z0.5cos, 0 z (8) The chaacteistics of cuent distibution of Antenna C is simila to that of Antenna C1, except the second function of quations (7) and (8) is multiplied by 0.5, thus the numeical analysis and the calculation of the paametes of Antenna C could be calculated following the same pocedue of analysis and calculation as of Antenna C1. Substituting quations (7) and (8) in quation (1), gives quations (9) and (30) which epesent the electic and magnetic field components of Antenna C espectively. Figue 13 shows the adiation patten of Antenna C. jt c cosπ cossin cosπ cos 1 1 4cos sin jt c π cosπ cossin cosπ cos 1 1 4cos sin.7. Antenna C3 (9) (30) The feeding aangements fo symmetical tiple feeding out of phase (Antenna C3) is shown in Figue 14. The mathematical expession fo the cuent distibution is indicated in quations (31) and (3); taking into consideation that coefficient of cosine facto is equal to 0.1 fo Antenna C3. sin L 0.1cos z I z z, L z 0 (31) L z L Iz sin z0.1cos, 0 z (3) Substituting quations (31) and (3) in quation (1), and solving following the same pocedue, yields quations (33) and (34) which epesent the electic and magnetic field components of Antenna C3 espectively. Figue 15 shows the adiation patten of Antenna C3. jt c cosπ cossin cosπ cos 1 0. 1 4cos sin jt c π cosπ cossin cosπ cos 1 0. 1 4cos sin (33) (34) The equations of the adiation patten fo Antenna C1, C and C3 ae deived based on the obtained equations of the cuent distibution. The equation of the adiation patten fo symmetical tiple feeding can be genealized as depicted in quation (35) jt c (35) M cosπ cossin cosπ cos 1 0.5 sin sin Figue 13. Radiation patten of antenna C. Figue 14. Feeding aangements fo tiple feeding full wave antenna. Figue 15. Radiation patten of antenna C3. Copyight 01 SciRes. JMAA
Analysis of the Radiation Resistance and Gain of Full-Wave Dipole Antenna fo Diffeent Feeding Design 41 Table 1. Measued and theoetical paametes of full wave antenna. Paametes Ant A1 Ant A Ant B1 Ant B Ant C1 Ant C Ant C3 Gain db Measued (powe gain) 3.1.1.3 1.9 5. 5.01 3.6 Gain db Theoetical (diectivity) 3.8.479 1.66.469 6.7 6.35 4.6 Z in Ω Measued 160 - j10 130 - j1 135 - j5 140 - j8 160 - j7 18 - j15 159 - j8 R ad Ω Theoetical 199.1 93.48 6.64 33.35 401. 50 03 fficiency 84% 91% 86% 88% 70% 73% 79% quation (35) is deived fo the adiation patten of symmetical tiple feeding, which is valid fo symmetical tiple feeding fo full-wave antenna egadless of the length and width of antenna. The validity of this quation fo asymmetical tiple feeding needs futhe examining, and stict investigations as is mentioned in pevious section. Moeove, accoding to [8], the asymmetical feeding poduces the input impedance, which is a combination of eal and imaginay values. Wheeas, fo symmetical tiple feeding antenna poduces the input impedance, which is pue esistance. Since, in asymmetical feeding, the atio between the peak cuent and the dive cuent can be even geate than and the cuent doesn t fall to the zeo at the end of the antenna. oweve, the analysis of the adiation patten shows an appeciable ageement among the measued, simulated and theoetical analyses. 3. Gain and fficiency Fo Antenna A1, the symmetical dual feeding technique poduced high gain as compaed to the single and centefed antennas. An impovement of about 3 to 3.5 db was achieved compaing to cente tap fed and off cente fed. oweve, this incease in diectivity is at the cost of inceasing the feed of the antenna. Fo Antenna A, when the polaity of feeding changes, the gain dops because the adiation patten is split into fou lobes, but Antenna A still gives bette esults as compaed to single-fed, with espect to gain and input impedance. The effects of the asymmetical feeding on adiation chaacteistics wee investigated. As shown in Table 1 and compaing to single off-cente feeding, it was found that an asymmetical dual feeding in-phase (Antenna B) povides good pefomance, consideing the diectivity, patten, and input impedance. A.46 db gain has been obtained. The investigation of the asymmetical dual feeding out-of-phase indicated that this antenna actually has a lesse gain than the single cente-fed and single off-cente fed and lowe input impedance at the input feeding pots. oweve, the gain of Antenna B1 is dopped appaently because the adiation patten has 6 lobes. It was found that a symmetical tiple feeding povides an oveall best pefomance with espect to gain, adiation patten, beam width, and input impedance an expession fo efficiency is given: G measued fficiency eff 100% 5.94 D theoetical whee D is the theoetical gain (Diectivity) of the antenna, and G is the measued gain (Powe Gain). The efficiency of Antennas A1, A, B1, B, C1, C, and C3 is indicated in Table 1 4. Conclusion The Analysis of the adiation patten and gain of diffeent feeding design of full-wave dipole antenna wee discussed and pesented. The symmetical dual feeding in phase as well as the symmetical tiple feeding in phase povided the best pefomance and esults compaing to cente tap fed and off cente fed. The theoetical and measued esults of both gain and input impedance wee pesented. RFRNCS [1] C. A. Balanis, Antenna Theoy: Analysis and Design, ape and Row Publishes, New Yok, 198. [] S.. Idis and C. M. adze, Analysis of the Radiation Resistance and Gain of Full-Wave Dipole, I Antennas and Popagation Magazine, Vol. 36. No. 5, 1994, pp. 45-47. doi:10.1109/74.33493 [3] K. M. Lambet, G. Anzic, R. J. Zakajsek and A. J. Zaman, An Oveview of the Antenna Measuement Facilities at the NASA Glenn Reseach Cente, NASA Technical Memoandum, Washington DC, 00. [4] Y. S.. Khaisat, K. A. mood and Al-M. Anwa, The Cuent Distibution of Symmetical Dual and Tiple Feeding Full Wave Dipole Antenna, Moden Applied Science, Vol. 5, No. 6, 011, pp. 16-13. doi:10.5539/mas.v5n6p16 [5] R. W. Lewallen, Baluns: What They Do and ow They Do It, The ARRL Antenna Compendium, atfod, 1985. [6] R.. Collin, Theoy and Design of Wide Band Multisection Quatewave Tansfomes, Poceedings of the IR, Vol. 43, No., 1955, pp. 179-185. Copyight 01 SciRes. JMAA
4 Analysis of the Radiation Resistance and Gain of Full-Wave Dipole Antenna fo Diffeent Feeding Design doi:10.1109/jrproc.1955.78076 [7] S. gashia, M. Taguchi and. Kitajima, The ffect of the nd Suface Cuent on the Numeical Solution of Wie Antennas, Tansactions of the Institute of lectonics and Communication nginees of Japan, Vol. 6, 1985, pp. 714-71. [8] N. K. Nikolova, The Oigin of Nonuniqueness in Invese lectomagnetic Poblems: A Review, Wokshop on Field-Based Synthesis and Compute Aided Design of lectomagnetic Stuctues, 16th Intenational Zuich Symposium & xhibition on lectomagnetic Compatibility, Zuich, 14-18 Febuay 005. Copyight 01 SciRes. JMAA