Wide-Angle X-Band Antenna Array with Novel Radiating Elements

Transcription

1 72 R. CHERNOBROVKIN, I. IVANCHENKO, L. P. LIGTHART, A. KOROLEV, N. POPENKO, WIDE-ANGLE X-BAND ANTENNA ARRAY Wide-Angle X-Bnd Antenn Arry with Novel Rditing Elements Romn CHERNOBROVKIN 1, Igor IVANCHENKO 1, Leo P. LIGTHART 2, Aleksey KOROLEV 3, Nin POPENKO 1 1 Usikov Inst. for Rdiophys. nd Electronics, Ntionl Acd. of Sciences, 12 Ac. Proskur St., Khrkov, 6185, Ukrine, 2 Int. Reserch Centre for Telecommunictions nd Rdr, Fculty of Electricl Engg., Mthemtics nd Computer Science, Delft University of Technology, Mekelweg 4, 2628 GA Delft, the Netherlnds 3 Inst. of Rdiostronomy, Ntionl Acdemy of Sciences of Ukrine, 4 Krsnoznmenny st., 6185, Khrkov, Ukrine ireurn@yhoo.com Astrct. An ntenn rry with wide-ngle em steering is presented in this pper. The ntenn consists of dielectriclly filled open-ended wveguides with new type of excittion s individul rditors. The chrcteristics of the rditor hve een nlyzed. The novel rditor hs wide emwidth nd the frequency nd of round 21%. Following the computtionl modeling nd experimentl investigtions the chrcteristics of the ntenn rry for scn ngles up to 5 re discussed. Keywords Antenn rry, open-ended wveguide, ner-field urements,rdition pttern. 1. Introduction The current progress in dvnced communiction systems leds to prticulr interest in rodnd phsed rry ntenns with lrge scn ngles [1-4]. It is worth noting, tht there re chllenging spects to e solved in ntenn rrys such s side loe level decrese, s well s reduction of oth ntenn size nd costs. The following requirements imposed to the individul rditors of the ntenn rry should e stisfied: 1. The element ndwidth should e more thn 2%; 2. The ntenn rry should ensure scn ngles over more thn 45 in oth principl plnes; 3. The polriztion should e liner. The structure of the ntenn element consists of n open-ended wveguide with dielectric insertion comprising specil pin for excittion. The pper focuses on modeling of the individul rditor nd the ntenn rry llowing for scn ngles up to 5, s well s the experimentl investigtions of the individul rditor nd ntenn rry prototype. 2. Modeling of the Antenn Arry The ntenn rry chrcteristics re investigted in the frequency rnge 8-11GHz. The computtionl modeling ws performed y using the softwre pckge HFSS. The rdition pttern urements were crried out y the technique developed erlier [5] nd llowed us to nlyze quickly the rdition chrcteristics of the ntenn under testing over the entire opertionl frequency nd. The ner-field distriutions were ured y the proe descried in [6]. 2.1 The individul Element of the Antenn Arry The open-ended wveguide filled with dielectric ws chosen s individul rditor to provide n element spcing in the ntenn rry less thn hlf wvelength t 1 GHz. One of the novelties of the individul rditor is the trnsition from SMA to wveguide using n originl excittion pin (Fig. 1). Fig. 1. Design of the individul rditor. At first, we exmined the prmeter S 11 of the semi-infinite rectngulr wveguide filled with dielectric (ε=2.5) nd perture dimensions 14mm 7mm. The wveguide excittion is relized y mens of long coxil trnsmission

2 RADIOENGINEERING, VOL. 17, NO. 2, JUNE line terminted with the pin (Fig. 1). The fundmentl H 1 mode propgtes in the rectngulr wveguide. In this cse the pin dimensions equl length l=4mm nd height h=5mm. Field mps in Fig. 2 demonstrte the wve process in such system nd the electromgnetic field distriution close to the excittion pin. [db] H-plne: θ [degree] -1 Fig. 2. Field mps for the semi-infinite wveguide excited y the coxil trnsmission line. In the frme of this reserch we nlyzed the prmeter S 11 s function of the following prmeters: pin height h, pin length l, length of the wveguide regulr prt nd height of the dielectric prism. These prmeters hve een chnged within the limits: 2 mm < h < 4.5 mm, 2 mm < l < 13 mm, 5 mm < < 15 mm, mm < < 3 mm. According to the results of computtionl modeling the individul rditor with prmeters h = 4.5 mm, l = 2.5 mm, =5 mm, = 2 mm ws chosen s sic element in the ntenn rry. Such rditor exhiits for S 11 < -1 db ndwidth 8.3 GHz < f < 13. GHz with the centre frequency round 9 GHz (see Fig. 3, the theoreticl curve). S 11 [db] frequency [GHz] Fig. 3. Input reflection coefficient of the individul rditor excited y coxil feeding line. For the individul rditor with the given prmeters the rdition ptterns in oth principl plnes hve een clculted. As cn e seen from Fig. 4, the rdition pttern of the individul rditor hs wide emwidth in oth H- plne ( θ=86 ) nd E-plne ( θ=96 ) with pek directivity oriented round zenith. [RP] E-plne: θ [degree] Fig. 4. Clculted nd ured rdition ptterns of the rditor prototype t 9 GHz in the H-plne (top) nd E-plne (ottom). Following the results of computtionl modeling the individul rditor with the selected prmeters ws mnufctured (Fig. 5) nd its chrcteristics were investigted experimentlly. We note tht the ured nd ulted input reflection coefficients re in good greement. However, the experimentl ndwidth of the rditor is less thn the theoreticl one ( f=21% in the experiment, f=3% in the theory, see Fig. 3). The pttern experiments hve shown tht the emwidth of the rditor in the H-plne remins virtully the sme over the opertionl frequency nd (see Fig. 4). In contrst to the theory mplitude ripples of round 1 db re oserved in the experimentl rdition ptterns in the E-plne. Furthermore, the ured emwidth is roder ( θ=13 in experiment nd θ=96 in theory). The min dvntges of the novel individul rditor cn e summrized s follows: A wide opertionl frequency nd; A wide emwidth in oth principl plnes over the entire opertionl frequency nd; The originl excittion pin llows for designing compct ntenn rry with element spcing less thn hlf of the smllest wvelength.

3 74 R. CHERNOBROVKIN, I. IVANCHENKO, L. P. LIGTHART, A. KOROLEV, N. POPENKO, WIDE-ANGLE X-BAND ANTENNA ARRAY Fig. 5. Relized individul rditor. 2.2 The Antenn Arry Bsed on our results of theoreticl nd experimentl investigtions we mnufctured the liner rry prototype, depicted in Fig. 6. The ntenn rry consists of 1 rditors with the sme chrcteristics s mentioned erlier. The rry elements re locted in the H-plne t mutul distnce of 15mm. The minimum spcing etween two djcent rditors is therefore ounded y the thickness of the metllic wlls ssocited to the wveguides. The ggregte length of the ntenn mounts 3mm (SMA connector excluded). Fig. 6. Liner rry prototype. We hve ured nd nlyzed the EM field distriutions in the rditing region of ech elementry rditor integrted in the ntenn rry. Co- nd cross-polriztions per element hve een investigted y hving ll other rditors terminted with mtched lods. As n exmple, the ner-field distriutions of rditors 6 nd 1 re shown in Fig. 7. It ws found tht the (co-polriztion) ner-field distriution in the XOY plne of ech rditor is widened long the OY xis (Fig.7, Fig.7c) due to the finite ground plne (width of the ground plne in the OY direction is 7 mm). It cn lso e seen tht when exciting the centrl element 6 the field intensity decreses slowly to -13 db t the ntenn ends (Fig. 7). From this study we hve lso lerned tht for the edge element 1 the mximl level of cross-polriztion is higher (-13 db) thn tht of the centrl element 6 (-18 db). However, the shpe of the ner-field remins virtully the sme in oth cses (Fig. 7 nd Fig. 7d). Fig. 7. Ner-field distriutions of two elements 6 nd 1 within the rry configurtion in the XOY plne t 8.45 GHz; element 6: - co-polriztion, - cross-polriztion, element 1: c - co-polriztion, d - cross-polriztion. c d

4 RADIOENGINEERING, VOL. 17, NO. 2, JUNE Clculted rdition ptterns of the ntenn rry for different scnning ngles were determined s follows. First, the rry fctor of the liner rry prototype ws ulted under the ssumption of sence of mutul coupling etween ntenn rry elements. After tht, the clculted rdition ptterns of the individul rditor (Fig. 4, ulted) were ccumulted tking into ccount the pth-length difference from different prts of the ntenn rry. As result we otined set of rdition ptterns for different scnning ngles s given in Fig. 8 (.). More specificlly, we derived from Fig. 8 tht: the ntenn exhiits emwidth of Δθ=1 (t db from the mximum); with incresing scnning ngle the emwidth slightly increses, too (T. 1). the side loes re -17 db for scnning ngle θ= nd mximum side loe level is oserved for scnning ngle θ=5. Scnning ngle θ Δθ Clcultion Side loe level Mesurement Δθ Side loe level 1-17dB 1-17dB dB 12-13dB 5 14 db 14-14dB T. 1. Rdition pttern prmeters of the ntenn rry. The rdition ptterns of elementry rditors in the rry configurtion were ured in the H-plne t 8.45 GHz nd hving ll other rditors terminted with 5 Ω mtched lods (Fig. 9). In this cse the rdition ptterns (Fig. 8) of the ntenn rry clculted from ured nd ulted dt hve the sme emwidths for ll scnning ngles (T. 1). A minimum side loe level is oserved for scnning ngle θ = (-17 db) nd it increses up to db for mximum scnning ngle. From comprison of ured with ulted results it is noted tht the level of side loes for scnning ngle θ = is the sme for the first two side loes nd the level of residul side loes is higher. At the sme time for other scnning ngles the clculted rdition ptterns hve side loe levels of the first four side loes (θ = 3 ) nd the first six side loes (θ = 5 ) which re higher thn in the ntenn prototype (see Fig. 8) Fig. 8. Rdition ptterns of the ntenn rry in the H- plne for different scnning ngles: () scnning ngle ; () scnning ngle 3 ; (c) scnning ngle 5. RP element ¹ 1-18 RP element ¹ RP element ¹ 1 RP element ¹ Fig. 9. Rdition ptterns of the elements 1 nd 1 () nd 5 nd 6 () in the H-plne t 8.45 GHz. c

5 76 R. CHERNOBROVKIN, I. IVANCHENKO, L. P. LIGTHART, A. KOROLEV, N. POPENKO, WIDE-ANGLE X-BAND ANTENNA ARRAY As cn e seen, the clculted nd ured results demonstrte tht the ntenn rry is le to provide em steering in the limits of ±5. 3. Conclusions A new type of individul rditor consisting of dielectric filled wveguide ntenn with specil excittion pin hs een proposed. The commercil Ansoft HFSS finite element sed code hs een used for rditor prmeters optimiztion. As result, the rditor prototype with n optimized geometricl configurtion hs een mnufctured. The numericl ultions were vlidted y comprison with urements performed on the physicl model. The sic chrcteristics of the rditor prototype re s follows: (i) the emwidth in the H-plne is Δθ=1 nd in the E-plne is Δθ=13 ; (ii) the crosspolriztion level is less thn db over the entire opertionl frequency nd. The liner ntenn prototype consisting of 1 individul rditors deployed in uniform rry configurtion hs een mnufctured. The urements of EM field distriutions of individul elements of the rry hve een crried out in the rditing nd fr-field regions. In greement with the ultions, the scnning ngle of the plnr ntenn rry consisting of 1 elements is round ±5 in H-plne nd the side loes level does not exceed db. Acknowledgements This prticulr reserch ws performed in the frme of the STCU Project P#217 titled Theory nd design of ntenn rrys, nd supported y the Interntionl Reserch Center for Telecommunictions nd Rdr, Delft University of Technology, Netherlnds. The responsiility for this puliction is held y the uthors only. References [1] HOLTER, H. Dul-polrized rry ntenn with BOR-elements, mechnicl design nd urements. IEEE Trnsctions on Antenns nd Propgtion, 27, vol. 55, no. 2, p [2] LEE, J. J., LIVINGSTONE, S., KOENING, R., NAGATA, D., LAI, L. L. Compct light weight UHF rrys using long slot pertures. IEEE Trnsctions on Antenns nd Propgtion, 26, vol. 54, no. 7, p [3] THORS, B., STEYSKAL, H., HOLTER, H. Brodnd frgmented perture phsed rry element optimiztion using genetic lgorism. IEEE Trnsctions on Antenns nd Propgtion, 25, vol. 53, no. 1, p [4] MC.GRATH, D. T., BAUM, C. B. Numericl nlysis of plnr icone nd TEM horn ntenns. IEEE Interntionl Antenns nd Propgtion Symposium Digest, June 1997, vol. 35, p [5] ANDRENKO, A. S., IVANCHENKO, I. V., IVANCHENKO, D. I.,. KARELIN, S. Y., KOROLEV, A. M., LAZ KO, E. P., POPENKO, N. A. Active rod X-nd circulr ptch ntenn. IEEE Antenns nd Wireless Propgtion Letters, 26, vol. 5, p [6] CHERNOBROVKIN R., IVANCHENKO I., POPENKO N. Novel V-nd ntenn for nondestructive testing techniques. Microwve nd Opticl Technology Letters, July 27, vol. 49, no. 7, p 1732 to Aout Authors... Romn CHERNOBROVKIN ws orn in Khrkov, Ukrine, in In June 25 he grduted from the Khrkov Ntionl University nd received the MS degree in Rdio Physics. From 25 to the present he works t the Institute for Rdio-Physics & Electronics of the Ntionl Acdemy of Sciences of Ukrine (IRE NASU). From 27 he is Junior Resercher Assistnt with the Deprtment of Rdio-Spectroscopy in the IRE NASU. He hs uthored nd co-uthored 8 pulictions in the fields of micro - nd millimeter wve ntenns. R. Chernorovkin is the Student Memer of IEEE. Igor IVANCHENKO for iogrphy, see pge 65 of this issue. Leo P. LIGTHART ws orn in Rotterdm, the Netherlnds, on Septemer 15, He received n Engineer's degree (cum lude) nd Doctor of Technology degree from Delft University of Technology in 1969 nd 1985, respectively. He is fellow of IEE nd IEEE. He received Doctortes (honoris cus) t Moscow Stte Technicl University of Civil Avition in 1999 nd Tomsk Stte University of Control Systems nd Rdioelectronics in 21. He is cdemicin of the Russin Acdemy of Trnsport. Since 1992, he hs held the chir of Microwve Trnsmission, Rdr nd Remote Sensing in the Deprtment of Electricl Engineering, Mthemtics nd Computer Science, Delft University of Technology. In 1994, he founded the Interntionl Reserch Center for Telecommunictions nd Rdr (IRCTR) nd is the director of IRCTR. Prof. Ligthrt's principl res of speciliztion include ntenns nd propgtion, rdr nd remote sensing, ut he hs lso een ctive in stellite, moile nd rdio communictions. He hs pulished over 5 ppers nd 2 ooks. Alexey KOROLEV nd Nin POPENKO for iogrphies, see pge 65 of this issue.