Leaky Wave Antennas Designed on a Substrate Integrated Waveguide

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Leky Wve Antenns Designed on Sustrte Integrted Wveguide Jn Mchc Czech Technicl University in Prgue, Fculty of Electricl Engineering Technick 2 16627 Prgue 6, Czech Repulic mchc@fel.cvut.

1 Leky Wve Antenns Designed on Sustrte Integrted Wveguide Jn Mchc Czech Technicl University in Prgue, Fculty of Electricl Engineering Technick Prgue 6, Czech Repulic mchc@fel.cvut.cz Astrct This pper presents the results of n investigtion of leky wve ntenns designed on sustrte integrted wveguide. The ntenns re of the following types: ntenn rditing from slot in the top wveguide wll, CRLH nd dul nd CRLH leky wve ntenns. The sustrte integrted wveguide cn esily e integrted with plnr microwve circuits. Antenns designed on this trnsmission line hve plnr structure, nd cn e fricted y stndrd PCB technology, so they re suitle for mss production. Keywords surfce integrted wveguide; leky wve ntenn; plnr trnsmission line min em y chnging the frequency from nerly ckwrd direction to forwrd direction [6, 7]. A line offering CRLH ehvior in two frequency nds ws proposed in [8], where the condition for this feture ws derived. Bsed on these results, new dul nd SIW LWA working in two frequency nds ws designed nd fricted [9, 10]. The ntenn rdites one min em tht cn e steered from the ckwrd direction to the forwrd direction y chnging the frequency in oth frequency nds. Rdition occurs through mender slots etched in the top metlliztion wll. I. INTRODUCTION Low-profile plnr ntenns cn e integrted with other circuits nd cn e esily fricted. They re therefore suitle for chep mss production. They hve een of gret interest to reserchers nd designers for more thn thirty yers. There re two kinds of low-profile plnr ntenns, which differ in the wy tht they rdite. Resonnt structures re in principle nrrow nd, nd their rdition ptterns re more or less fixed, defined y the ntenn structure. Trveling wve ntenns leky wve ntenns (LWA) re rod nd, nd their rdition pttern cn e steered y chnging the frequency. In recent yers, new concept for the design of microwve nd millimeter-wve wveguide structures nd components hs een proposed [1, 2]. Sustrte integrted wveguide (SIW) structures, lso known s lminted wveguide or post-wll wveguide structures, use this concept. SIWs re sed on the equivlence etween well-known metllic wveguide structures [3] (usully wveguide of rectngulr crosssection) nd wveguiding structures on dielectric sustrte using rows of metl posts (vis), see Fig. 1. Cost-effective microwve SIW circuits re simple to design using this pproch [1, 2]. The SIW leky wve ntenn concept ws proposed in [4]. This ntenn rdites energy through the SIW side wll with sprsely locted shortening vis. The concept of n LWA sed on rdition through the wide slot in the SIW top wll due to leky wve of the first order ws proposed in [5]. The SIW designed s lnced right/left-hnded (CRLH) trnsmission line ws used s n LWA le to steer the rdition pttern Fig. 1. Sustrte integrted wveguide structure (), post dimensions nd geometry (). Another novel form of dul nd SIW LWA ws presented in [11]. The structure ws designed on the sis of circuit model tht predicts its ehvior. This pper summrizes the results of SIW LWA reserch done y the uthor nd pulished nmely in [5, 9, 10]. The im is to design ntenns with plnr structure tht cn e integrted simply with trnsmitter/receiver circuits nd cn esily e mounted on surfces of lrge odies without deteriorting their shpes. II. SUBSTRATE INTEGRATED WAVEGUIDE A sustrte integrted wveguide is synthetic rectngulr electromgnetic wveguide formed in dielectric sustrte y two rows of metllized posts or vi-holes which connect the upper nd lower metl pltes of the sustrte. This is direct nlogy to the rectngulr shpe wveguide with metllic wlls [3], where the side wlls re creted y the two rows of posts, d p

The min guidelines for the SIW design were presented in [12, 13

2 see Fig. 1 [1]. The wveguide cn e fricted esily with low-cost nd mss-production, using through-hole techniques. The SIW hs similr guided wve nd mode chrcteristics to the conventionl rectngulr wveguide with the equivlent guided wvelength. The discontinuous side wlls prevent the SIW from guiding TM modes. The min guidelines for the SIW design were presented in [12, 13]. This involves designing SIW width, post dimeter d, nd post spcing p, Fig. 1. The SIW width defines the cutoff frequency c [3], which is determined y the effective width the width of the equivlent rectngulr wveguide e, tht is [13] 2 2 e d d (1) p For given d/ c, keeping nturlly p > d, the post spcing hs to e chosen within the intervl p , (2) c where the lower limit is defined y the mechnicl firmness of the sustrte, nd the upper limit is defined y omitting the stop-nd working regime [12] defined y Brgg condition. Post dimeter d is then defined y the lekge losses [12]. III. ANTENNA RADIATING FROM A SLOT IN THE BROAD WALL An SIW LWA rditing from longitudinl slot etched in the upper wide wll ws designed nd fricted [5]. The ntenn is fed through microstrip line, Fig. 2, nd the first spce leky mode with odd symmetry is excited long the line. The ntenn rdites em tht cn e steered s in the cse of stndrd LWAs in the forwrd direction y chnging the frequency. The Rogers 4350B sustrte with h = mm in thickness with reltive permittivity r = 3.48 nd loss fctor tn = ws used. To get the mximum rdition in the frequency nd round 19 GHz we chose ccording to the dispersion chrcteristics shown in [5, 14] SIW width = 9 mm nd slot width w = 5 mm, see the ntenn crosssection in Fig. 2. h r1 r2 w z y x The chosen ntenn length ws l = 100 mm, mesured long the slot with the full width, see Fig. 2, due to the requirement tht the mplitude of the spce leky mode t the end of the ntenn should e 10% of its mgnitude on the feeding tip t men operting frequency 19 GHz. The ntenn gin might e incresed y prolonging the ntenn, since with the fricted structure out 10% of the power coupled to the ntenn is lost in the terminting impednce. The rditing slot ws terminted y wedges to minimize reflections. The finl ntenn width g ws chosen three times wider thn the SIW width. The mesured S-prmeters, nd the S-prmeters clculted y the CST Microwve Studio, of the SIW LWA re plotted in Fig. 3. For the simultion, no dielectric losses nd no electric losses were considered, which cn e seen in the difference etween the mesured results nd the simulted results. The operting frequency nd defined y reflection coefficient lower thn -10 db strts t 18 GHz, nd from ove it is limited y the existence of the spce leky mode documented in the dispersion chrcteristics [5], which is out 20.5 GHz. A comprison of the mesured nd clculted rdition ptterns t 20 GHz is shown in Fig. 4, with very good greement. The mesured rdition ptterns normlized to 0 db re plotted in Fig. 5. The ntenn rdites em steered in the verticl plne from 48 t 18 GHz to 15 t 21 GHz, mesured from the forwrd direction. The full width t hlf power of the min ntenn em in the verticl plne vries from round 13 t 18 GHz to 21 t 21 GHz. The side loes re out 10 db elow the level of the mximum rdition. Fig. 3. Mesured nd simulted (CST Microwve Studio) scttering prmeters of the ntenn from Fig. 2 [5]. Fig. 2. Antenn cross-section (), fricted ntenn rditing from slot in the rod wll () [5].

Fig. 4. Mesured nd simulted rdition ptterns of the ntenn from Fig. 2 t 20 GHz [5]. Fig. 6.

The prmeters of the fricted ntenn specimen were deteriorted y improperly mounted SMA connectors to reltively wide 50 microstrip trnsmission lines, see Fig. 6.

AN ANTENNA BASED ON CRLH SIW An SIW-sed ntenn similr in form to the ntenn lredy pulished in [6] ws designed for ppliction in n ntimissile rdr system.

The ntenn structure composed of 26 CRLH cells is shown in Fig. 5. The SIW cell is 9.5 mm in length nd = 9 mm.

3 Fig. 4. Mesured nd simulted rdition ptterns of the ntenn from Fig. 2 t 20 GHz [5]. Fig. 6. Fricted CRLH SIW LWA (), detil of the structure with the trnsition to the microstrip nd widened SIW tht works ove its cut off (). The prmeters of the fricted ntenn specimen were deteriorted y improperly mounted SMA connectors to reltively wide 50 microstrip trnsmission lines, see Fig. 6. However, pir of these ntenns works well in the designed rdr system. Fig. 5. Mesured rdition ptterns of the ntenn from Fig. 2 [5]. IV. AN ANTENNA BASED ON CRLH SIW An SIW-sed ntenn similr in form to the ntenn lredy pulished in [6] ws designed for ppliction in n ntimissile rdr system. The dvntge ws the ility to steer the ngle of the min rdition em simply y chnging the frequency. The SIW is designed on the Rogers RO4003C sustrte mm in thickness nd with permittivity The ntenn structure composed of 26 CRLH cells is shown in Fig. 5. The SIW cell is 9.5 mm in length nd = 9 mm. The ntenn rdites through mender slots tht represent series cpcitors of the CRLH equivlent circuit. Shunt inductors re represented y two shunt inductive posts locted in ech SIW cell. The frequency nd of this ntenn opertion is documented y the dispersion chrcteristic clculted y the CST Microwve Studio eigen mode solver in Fig. 7. The SIW CRLH line is lnced, with no nd gp. The free spce propgtion constnt k o limits the frequency nd of the rdition from out 8.6 GHz to 11.7 GHz. This nd is verified y the frequency chrcteristic of the scttering prmeters plotted in Fig. 8. The clculted rdition ptterns nd the rdition ptterns simulted y the CST Microwve Studio re compred in Fig. 9. They re normlized to 15 db. The ntenn rdition pttern min loe vries continuously with chnging frequency from -50 to 70 mesured from the rodnd direction. The steering of the rdition pttern y chnging the frequency is documented in Fig. 10, where the clculted rdition ptterns re plotted. Fig. 7. Dispersion chrcteristic of the ntenn from Fig. 6, clculted y the CST Microwve Studio. Fig. 8. Clculted (CST Microwve Studio) S 11 nd S 21 of the ntenn shown in Fig. 6.

Fig. 9. Mesured nd simulted rdition ptterns of the ntenn from Fig. 6 t 11

Fricted CRLH SIW LWA (), detil of the structure showing prticulr cells nd the mtching circuit with the trnsition to the microstrip line (), [9]. 0 11.5 GHz 11 GHz 10.5 GHz 10 GHz 9.6 GHz 9.

5 GHz -90-20 20 directivity (db) 180 An nlysis of the SIW ntenn structure ws mde y the CST Microwve Studio using solid PEC wlls terminting the SIW from the sides in order to simplify the computtion

4 Fig. 9. Mesured nd simulted rdition ptterns of the ntenn from Fig. 6 t 11 GHz. 90 corresponds to the rod side, 180 corresponds to the forwrd direction. 90 Fig. 11. Fricted CRLH SIW LWA (), detil of the structure showing prticulr cells nd the mtching circuit with the trnsition to the microstrip line (), [9] GHz 11 GHz 10.5 GHz 10 GHz 9.6 GHz 9.3 GHz 9 GHz 8.5 GHz directivity (db) 180 An nlysis of the SIW ntenn structure ws mde y the CST Microwve Studio using solid PEC wlls terminting the SIW from the sides in order to simplify the computtion process [9, 10]. A Rogers RO4003C sustrte mm in thickness with reltive permittivity 3.38 ± 0.05 nd loss fctor ws used. The design of the ntenn ws performed y corse optimiztion performed in the CST Microwve Studio, imed t closing the nd gps etween the LH nd RH nds. However, there re finlly some gps left. For the structure presented here, with the cell 12 mm in length nd 10.8 mm in width, the gps re t 25 nd 85 MHz in width. The complex dispersion chrcteristics of this ntenn were clculted y the method introduced in [10] nd show clerly the two ntenn working nds, Fig. 12. Fig. 10. Steering of the rdition pttern (normlized) of the ntenn shown in Fig corresponds to the rod side, 180 corresponds to the forwrd direction. V. DUAL BAND CRLH SIW ANTENNA The design of the ntenn is sed on the conclusions of [8] concerning the dul nd/qud nd opertion of the CRLH trnsmission line. The equivlent circuit (EQC) of such line is composed of comintions of series nd prllel resonnt L-C circuits oth in the through rnch nd in the shunt rnch. This is tken into ccount y the proposed ntenn unit cell structure shown in Fig. 11. The series elements re represented minly y the mender slots through which the ntenn rdites, see Fig. 11. The prllel elements re represented y four conducting vis. All these elements re however mutully coupled, nd the EQC of the cell derived from its dispersion chrcteristic [9] fully corresponds to the EQC presented in [8]. The designed ntenn ws fricted y plnr printed circuit ord technology in two specimens hving 15 nd 25 cells. Fig. 11 shows photogrph of the longer ntenn. Fig. 12. Complex dispersion chrcteristics phse nd ttenution constnts of the ntenn from Fig. 11 [10]. The rdition ptterns of the longer ntenn with 25 cells tken in the longitudinl plne norml to the ntenn surfce were clculted y CST MWS, nd were lso mesured; see Fig. 13. Angle ws mesured from the ckwrd direction, nd equls 90 t the rod side. The ptterns show the min dvntge of this LWA sed on the CRLH line, steering the direction of the min loe from ckwrd direction to forwrd direction y chnging the frequency in the two frequency nds. The ehvior of the shorter ntenn is similr, except tht the ems re wider.

The nrrow min em is rdited from out 8.6 up to 9.5 GHz in the lower CRLH nd. The min loe of the rdition pttern cn e steered from 65 to 125 in this frequency nd.

These loes re cused y spurious rdition of the SMA microstrip trnsition, s chrcteristics clculted for the ntenn model without these trnsitions re free of this spurious rdition.

5 The nrrow min em is rdited from out 8.6 up to 9.5 GHz in the lower CRLH nd. The min loe of the rdition pttern cn e steered from 65 to 125 in this frequency nd. The rdition ptterns exhiit side loes round 150 tht re only out 6 to 10 db lower thn the min loes. These loes re cused y spurious rdition of the SMA microstrip trnsition, s chrcteristics clculted for the ntenn model without these trnsitions re free of this spurious rdition. The second CRLH nd is wider thn the first nd, nd spns from out 15 up to 19 GHz. The em is nrrower thn in the lower nd. The em steering is less sensitive here, nd cn e done in the spn of 65 to 105. The rdition ptterns suffer from the existence of side loe, directed in elevtion ngles etween 130 nd 170, which is out 6 to 12 db smller in the mesured plots thn the min em. The decrese in ntenn efficiency with incresing frequency my e due to residul rdition of the feeding cles used in the mesurement setup ut not included in the EM model. The ntenn gin ws evluted y the comprison method, which uses mesurements performed y DRH20 doule ridge horns, see [15]. This gin is 6.5 dbi t 8.8 GHz, nd 16 dbi t GHz. c d Fig. 13. Clculted nd mesured rdition ptterns for vrying frequency in the first nd (), (), nd in the second nd, (c), (d), respectively, of the ntenn from Fig. 11 [10]. VI. CONCLUSIONS This pper hs summrized the results of the uthor s investigtion of leky wve ntenns designed on sustrte integrted wveguide. The ntenns re: n ntenn rditing from slot in the rod wll flt wveguide LWA, CRLH sustrte integrted wveguide ntenn, nd CRLH sustrte integrted wveguide ntenn rditing two frequency nds. A sustrte integrted wveguide leky wve ntenn rditing from slot in the rod wll prllel to its xis ws designed nd fricted. The initil dimensions of the SIW nd of the slot were otined from nlyticl expressions for equivlent rectngulr wveguides nd from the dispersion chrcteristics. The SIW, the ntenn lyout nd the feeding circuit were then optimized, using the CST Microwve Studio. The mesured S-prmeters nd ntenn chrcteristics fit well with the clculted results. The operting frequency nd is from 18 GHz to 21 GHz, nd the gin is out 7 db t 19 GHz. The ntenn rdites em steered in the verticl plne from 48 t 18 GHz to 15 t 21 GHz mesured from the forwrd direction. A CRLH sustrte integrted wveguide leky wve ntenn ws designed nd fricted. This ntenn operted in the frequency nd from 8.6 GHz to 11.7 GHz, nd the min em of the rdition pttern cn e steered y chnging the frequency from -50 to 70 mesured from the rod side direction. This ntenn works in n ntimissile rdr system.

6 A dul nd sustrte integrted wveguide leky wve ntenn ws designed, fricted nd mesured. The lnced CRLH sustrte integrted wveguide ws used to provide the possiility to scn the rdited em from ckwrd direction to forwrd direction y chnging the frequency. The ntenn rdites the nrrow em in two frequency nds spnned from pprox. 8.6 up to 9.5 GHz nd from 15.0 up to 19.0 GHz. The exct scnning ility is 60 cross the rod side direction in the lower nd, nd out 40 cross the rod side direction in the upper nd. The nlysis performed y CST Microwve Studio verifies the mesured ntenn chrcteristics well. The designed flt - plnr ntenns re intended to e integrted into ntenn rrys, nd directly into T/R systems where em scnning is required. The flt ntenn cn esily e mounted on surfces of lrge odies (e.g., ircrft) without deteriorting their shpe. The ntenns re fricted y simple PCB process, nd re therefore chep nd suitle for mss production. ACKNOWLEDGMENT This work ws supported in prt y the Grnt Agency of the Czech Repulic under project 102/09/0314, nd y the Czech Technicl University in Prgue under project SGS 10/271/OHK3/3T/13 (mesurements). REFERENCES [1] D. Deslndes nd K. Wu: Integrted Microstrip nd Rectngulr Wveguide in Plnr Form, IEEE Microwve Wireless Component Letters, Vol. 11, No. 2, pp , Fe [2] D. Deslndes nd K. Wu, Single-Sustrte Integrtion Technique of Plnr Circuits nd Wveguide Filters, IEEE Trns. on Microw. Theory nd Tech., Vol. 51, No. 2, Fe. 2003, pp [3] N. Mrcuvitz, Wveguide Hndook. Dover, [4] D. Deslndes nd K. Wu, Sustrte Integrted Wveguide Leky-Wve Antenn: Concept nd Design Considertions, 2005 Asi Pcific Microw. Conf. Proc., Dec. 2005, Suzhou, Chin. [5] J. Mchc, P. Lorenz, M. Sglm, C.-T. Bui, nd W. Kremer, Sustrte Integrted Wveguide Leky Wve Antenn Rditing from Slot in the Brod Wll, 2010 IEEE MTT-S Int. Microw. Symp. Digest, TU1A-2, My [6] Y. D. Dong, nd T. Itoh, Composite Right/Left-Hnded Sustrte Integrted Wveguide nd Hlf Mode Sustrte Integrted Wveguide Leky-Wve Structures, IEEE Trns. on Antenns Propgt., Vol. 59, No. 3, Mrch 2011, pp [7] Y. Weitsch nd T. F. Eiert, Composite Right-/Left-Hnded Interdigitl Leky-Wve Antenn on Sustrte Integrted Wveguide, EUCAP 2010: The 4th Eur. Conf. Antenns Propgt., April 2010, Brcelon, Spin. [8] G. V. Eleftherides, A Generlized Negtive-Refrctive-Index Trnsmission-Line (NRI-TL) Metmteril for Dul-Bnd nd Qud- Bnd Applictions, IEEE Microw. nd Wireless Compon. Lett., Vol. 17, No. 6, June 2007, pp [9] J. Mchc, M. Polivk, A Dul Bnd SIW Leky Wve Antenn, 2012 IEEE MTT-S Int. Microwve Symp. Digest, WE4J-4, June [10] J. Mchc, M. Polivk, K. Zemlykov: A Dul Bnd Leky Wve Antenn on CRLH Sustrte Integrted Wveguide, IEEE Trns. Antenns nd Propgtion, Vol. 61, No. 7, July 2013, pp [11] M. Durn-Sindreu, J. Choi, J. Bonche, F. Mrtin, T. Itoh: Dul-Bnd Leky Wve Antenn with Filtering Cpility Bsed on Extended/Composite Right/Left-Hnded Trnsmission Lines, 2013 IEEE MTT-S Int. Microw. Symp. Digest, TH3F-3, June [12] D. Deslndes nd K. Wu, Accurte Modeling, Wve Mechnisms, nd Design Considertions of Sustrte Integrted Wveguide, IEEE Trns. on Microw. Theory nd Tech., Vol. 54, No. 6, June 2003, pp [13] F. Xu, K. Wu: Guided-Wve nd Lekge Chrcteristics of Sustrte Integrted Wveguide, IEEE Trns. on Microw. Theory nd Tech., Vol. 53, No. 1, Jn. 2005, pp [14] Zehentner J., Mcháč J., Zloudil P.: Novel Entire Top Surfce Plnr Leky Wve Antenn, 37th Europen Microwve Conference, Octoer 2007, Munich, Germny, CD-ROM, pp [15] Dtsheet of doule ridged wveguide horn model DRH20. RFspin, s.r.o., Prgue, Czech Repulic [Online]. Aville:

Design and Modeling of Substrate Integrated Waveguide based Antenna to Study the Effect of Different Dielectric Materials

Design and Modeling of Substrate Integrated Waveguide based Antenna to Study the Effect of Different Dielectric Materials Design nd Modeling of Substrte Integrted Wveguide bsed Antenn to Study the Effect of Different Dielectric Mterils Jgmeet Kour 1, Gurpdm Singh 1, Sndeep Ary 2 1Deprtment of Electronics nd Communiction Engineering,