In this letter, an empty substrate integrated waveguide
H-plane sectorial horn antenna is presented. The antenna
is integrated within a planar substrate and is fed by means of a
microstrip transmission line. It is composed of a partially empty
substrate layer stacked between two cover metallic plates. Results
obtained for a prototipe designed and fabricated at Ku-band
show a measured efficiency close to 90% and matched responses.
No extra loading elements are needed in order to reduce reflection
at the end of the aperture conversely to previous designs.
Moreover, the structure is quite simple, cheap and does not
depend on substrate characteristics i.e. dielectric permitivity or
loss tangent. This new methodology for manufacturing substrate
integrated antennas without dielectric considerably improves the
performance of conventional substrate integrated horn antennas

Belenguer, Angel

Borja, Alejandro L.

Mateo Sotos, Jorge

Torres Aranda, Ana María

Universidad de Castilla-La Mancha: Repositorio Universitario Institucional de Recursos Abiertos (RUIdeRA)

1Highly Efficient and Well-Matched Empty SubstrateIntegrated Waveguide H-plane Horn AntennaJorge Mateo, Ana M. Torres, Angel Belenguer, Senior Member, IEEE, and Alejandro L. Borja, Member, IEEEAbstract—In this letter, an empty substrate integrated waveg-uide H-plane sectorial horn antenna is presented. The antennais integrated within a planar substrate and is fed by means of amicrostrip transmission line. It is composed of a partially emptysubstrate layer stacked between two cover metallic plates. Resultsobtained for a prototipe designed and fabricated at Ku-bandshow a measured efficiency close to 90% and matched responses.No extra loading elements are needed in order to reduce reflectionat the end of the aperture conversely to previous designs.Moreover, the structure is quite simple, cheap and does notdepend on substrate characteristics i.e. dielectric permitivity orloss tangent. This new methodology for manufacturing substrateintegrated antennas without dielectric considerably improves theperformance of conventional substrate integrated horn antennas.Index Terms—Empty substrate integrated waveguide, sub-strate integrated waveguide, H-plane sectoral horn antenna, highefficiency.I. INTRODUCTIONDURING the last years, a great number of substrate inte-grated circuits have been developed. These new circuitscombine the advantages of classical non planar technologies(waveguide or coaxial transmission lines for instance) such ashigh quality factors, and the benefits of planar circuits such aslow cost and easy compact integration. In this regard, substrateintegrated waveguide (SIW) technology allows to constructseveral types of commonly used antennas in a planar way[1], [2]. However, different limitations associated to the useof the substrate appear in the implementation of certain typesof antennas, i.e. low efficiency as frequency is increased dueto dielectric loss, strong mismatch as a consequence of theuse of thin substrate layers, and high reflection at the endof the aperture caused by the impedance difference betweenthe dielectric and air. Several strategies have been developedto overcome these problems, and to optimize the design ofdielectric-loaded horn antennas [3]–[7]. Some of them requirethe use of non-printed elements making the building proceduremore complicated. Solutions based on integrated dielectriclenses have also been proposed but their performances arelimited by the thickness of the substrate [8]–[12]. Nevertheless,the drawback related to losses introduced by the dielectric, andconsequently low efficiency, has not been solved yet.We present in this letter, a H-plane horn antenna withimproved performance. The topology of the antenna is basedThis work was supported by the Ministerio de Economı́a y Competitividad,Spanish Goverment, under Research Project TEC2013-47037-C05-3-R.All authors are with Departamento de Ingenierı́a Eléctrica, Electrónica,Automática y Comunicaciones, Universidad de Castilla-La Mancha, EscuelaPolitécnica de Cuenca, Campus Universitario, 16071 Cuenca, Spain (e-mail: jorge.mateo@uclm.es, ana.torres@uclm.es, angel.belenguer@uclm.es,alejandro.lucas@uclm.es.on the novel structure proposed in [13]. In this work, a newmethodology for manufacturing empty substrate waveguides,without dielectric, but at the same time completely integratedin a planar substrate is proposed. The empty substrate in-tegrated waveguide (ESIW) has an easy fabrication processwhile keeping the advantages of non planar structures such ashigh quality factor, quick simulation and optimization analisysand low loss. By this mean, horn integrated antennas withhigh radiation efficiency and good matched responses can beobtained.The letter is structured as follows: Section II introduces thedesign and simulations of an ESIW horn antenna. Experimen-tal results are discussed in Section III. Finally, Section IV isdevoted to the conclusions of the paper.II. ESIW H-PLANE SECTORIAL HORN ANTENNA DESIGNThe geometry of the ESIW H-plane sectorial horn antennaand the parameters used in the subsequent analysis are givenin Fig. 1. As it can be seen, a  /4 adapter has been used tomatch the waveguide at 15 GHz. This ensures that almost allthe energy that provides the microstrip line is transmitted tothe horn antenna.yxatRHlguiaAalt1R0lHlmsDHFig. 1: Geometry of the ESIW H-plane sectorial hornantenna (x-y cut).Next, the antenna design procedure followed is described.First, the size of the horn is chosen to obtain the desireddirectivity. In order to provide minimum phase error alongthe horn aperture the following expressions have been used[14]:l2H = R20 +✓A2◆2, (1)This is the author's version of an article that has been published in this journal. Changes were made to this version by the publisher prior to publication.The final version of record is available at                                                                             .http://dx.doi.org/10.1109/LAWP.2016.25161032↵H = arctan✓A2R0◆2, (2)RH = (A  at)s✓lHA◆  14, (3)where A is the dimension of the horn antenna at the opening,RH is the radius of the horn and lH is the length of theantenna.Then, a first version of the horn without transformer isanalyzed. To do this, the horn antenna is directly fed by theguide of width a. In this step, the dimensions of the hornare calculated in terms of a, i.e. at must be replaced by a in(3). The results obtained serve to identify the resonances ofthe horn antenna. However, near the resonances, the field inthe horn is distorted and the radiation pattern differs from thetheoretical. As a result, it is more appropriate to match the hornbetween resonances, where the infield is stable and providesdiagrams very similar to the theoretical radiation patterns.Therefore, the horn is rescaled so that the identified reso-nances in the previous step are far from the design frequency.In this way, it must be ensured that the horn, with its new size,still fulfills the requirement of directivity. If this is not the case,the horn is rescaled again making it larger, but maintainingthe resonances far from the design frequency. The next step isto analyze the horn antenna without transformer and estimateits input impedance. The reference plane to calculate the Sparameters is situated at the beginning of the horn and, in thatcase, its input impedance is:Zin =(1 + S11)(1  S11). (4)1234Fig. 2: ESIW layout (3D view).The following is to design a transformer to adapt thisimpedance. In such a way at and lt1 will be calculated.Finally the transformer dimensions and the radius of thehorn antenna are optimized: at, lt1 and R0. To make thehorn antenna optimal, its dimensions are calculated usingat, because now it is fed with that guide. The rectangularwaveguide and sectorial horn antenna are integrated by usingthe same single substrate based on the ESIW technology (seeFig. 2). This figure is the model used for the simulation. Thisstructure is designed by emptying an appropriate hole in aplanar substrate which is closed with two thin upper and lowercovers (numbers 2 and 4 in Fig.2). A secondary cover, on thetop of the structure (number 1 in Fig.2) prevents undesiredradiaton from the microstrip line and the SMA conector thatfeeds the antenna. The taper has been designed followingthe procedure highlighted in [13]. It is optimized with thefollowing objetives (S11 <  15 dB and S21 >  2 dB) for afrequency range of 12 GHz to 18 GHz. The final dimensionsof the horn antenna are listed in Table I. In a traditional SIW,the electromagnetic waves are confined in a dielectric bodyenclosed by the upper and lower metallic walls of the substrate,and by lateral metallized circular holes. However, in the ESIW,the electromagnetic fields travel in the vacuum, and they areconfined by upper, lower, and lateral metallic layers. Thereforethe electromagnetic waves are propagated in the air, whichimplies low losses.TABLE I: Parameters of the H-Plane Horn Antenna.Parameter Valuea(mm) 15.79at(mm) 10.53lt1(mm) 14.33A(mm) 42.49R0(mm) 30.118RH (mm) 22.65lms(mm) 20lguia(mm) 65III. EXPERIMENTAL AND SIMULATED RESULTSIn order to validate the proposed design a prototype hasbeen fabricated and measured. This structure is manufacturedby emptying a hole in a planar substrate. Next, the substrate ismetallized so that the lateral walls of the empty horn antennaare created. After that, the microstrip-to-ESIW taper is cut,and, finally, two thin upper and lower metallic walls aresoldered to the substrate in order to confine the fields inside thehorn. To fabricate this ESIW horn antenna, a LPKF ProtomatS103 circuit board plotter was used. This machine providesa manufacturing resolution of 0.5 µm and a repeatability of±0.001mm. The LPKF Mini Contac RS system was used forthe electroplating. Fig. 3 shows the antenna prototype.The commercial simulator Computer Simulation Technology(CST) Studio Suite 2014 has been used for the full-wavesimulations. The simulated and measured reflection coefficientis shown in Fig. 4. As it can be seen, a good agreement isobtained between both responses. However, a small frequencyThis is the author's version of an article that has been published in this journal. Changes were made to this version by the publisher prior to publication.The final version of record is available at                                                                             .http://dx.doi.org/10.1109/LAWP.2016.25161033shift of 41 MHz is observed. Differences between simula-tion and measurements are due to the manufacturing processattributed to substrate permittivity variations, imperfectionsduring the metallization and soldering and dimensions errorsoccurred during the milling. A narrow bandwidth around268 MHZ and 207 MHz for simulations and measurements,respectively, is obtained. The best return loss is 50 dB at 15GHz and 30 dB at 14.96 GHz for simulated and measuredresults. Therefore, the antenna is well matched without use ofexternal elements due to the absence of substrate.Fig. 3: a) ESIW 15 GHz H-plane sectoral horn an-tenna before assembling and b) Fabricated ESIW hornantenna prototype.14 1514.5 15.5 1650403020100Frequency (GHz)Magnitud (dB)S11 measuredS11 simulatedFig. 4: Simulated and measured |S11| parameters.The normalized 3D and E-plane radiation patterns are shownin Fig. 5. The radiation patterns have been obtained for thedesign frequency. A typical radiation pattern for H-planesectorial horn antennas is obtained, see Fig. 5 a). However,some discrepancies can be observed due to the imperfectionsraised during the fabrication process. The most crucial pointis the assembling of the different layers as a consequence ofthe generation of undesired resonances and air gaps insidethe structure. Both effects can modify the radiation in certaindirections and can also produce a strong ripple in the radiationpattern. In order to avoid the effects of these resonances and airgaps, a high quantity of soldering paste have been employedduring the manufacturing of the antenna.0-45-5-10-15-20-25-30-35-40zxyMeasureddBa)-180 -120 -60-60-50-40-30-20-10060 120 1800-70dB(º)Measured Normalized H-plane radiation patternb) SimulatedISimulatedNormalized 3D radiation pattern Fig. 5: Normalized radiation pattern. a) 3D plot and b)E-plane plot.The maximum of radiation is obtained along the x-axis withmeasured directivity 8.94 dBi and measured total efficiency89.1%. In Fig. 5 b), the maximum appears at ✓ = 0 , asexpected. Besides, the measured side lobe level (SLL) is 8.55dBi, the -3 dB beamwidth and the beamwidth between firstnulls are 15  and 20 , respectively. In addition, an efficiencyanalysis including the values obtained for different ESIW andSIW antenna configurations, i.e. taking into account or notThis is the author's version of an article that has been published in this journal. Changes were made to this version by the publisher prior to publication.The final version of record is available at                                                                             .http://dx.doi.org/10.1109/LAWP.2016.25161034the micrsotrip feeding and SMA connector, has been carriedout, see Table II. The simulated efficiency for the ESIWhorn antenna including the microstrip feeding and the SMAconnector is 92.9%. The difference between measured andsimulated results is due to quality of the electro-depositedcopper that closes the structure. In the real device this metallicenclosure shows high degree of granularity while in simu-lations a perfectly plane copper layer has been considered.This fact increases the conduction losses in the metal, thusthe efficiency is slightly worse (around 3.8%) in experimentalresults. In order to compare the performance of this novelESIW arrangement, an equivalent SIW horn antenna hasbeen designed working at the same frequency. Both antennashave been simulated without considering the feeding linesconnectors and transitions, so that only the target devices havebeen actually analyzed. The efficiency of the ESIW antenna is99.9% while the efficiency of the equivalent SIW antenna isonly 69.3%. A third part of the input power, i.e. a 30.6%, is lostduring the propagation inside the SIW antenna. Simulationsalso prove that approximately a 7% of the total radiationefficiency is lost when the feeding elements are considered(SMA connector, microstrip feeding line and transition toESIW). Since, the measured efficiency for the whole antennais 89.1%, it is expected that the ESIW horn antenna itself willbe able to provide a total radiation efficiency above 95%.Finally, it is worthwhile to mention that the high efficiencyobtained for the proposed structure cannot be achieved withcurrent SIW planar horn antennas due to substrate losses. Thisfact limit the use of substrate filled antennas to medium andlow frequency ranges of operation.TABLE II: Total efficiency for different ESIW andSIW antenna configurations.Antenna Configuration Total efficiencyMeasured ESIW with microstrip feeding and SMA 89.1%Simulated ESIW with microstrip feeding and SMA 92.9%Simulated ESIW with microstrip feeding 94.8%Simulated ESIW without microstrip feeding 99.9%Simulated SIW without microstrip feeding 69.3%IV. CONCLUSIONSAn ESIW horn antenna with high efficiency and well-matched is presented in this paper. This novel horn antennahas been designed and manufactured successfully. Simulatedand experimental results show a radiation efficiency close to89% and return losses around 30 dB. The structure proposedimproves the performance of previous SIW antennas. Potentialuse of these sort of antennas can be foreseen in a wide numberof applications due to its easy integration and low cost.REFERENCES[1] Z. Li, K. Wu, and T. Denidni, “An new approach to integrated hornantenna,” pp. 535–538, 2004.[2] Z. Li, X.-P. Chen, and K. Wu, “A surface mountable pyramidal hornantenna and transition to substrate integrated waveguide,” pp. 607–610,2007.[3] M. Esquius-Morote, B. Fuchs, J. Zurcher, and J. Mosig, “A printedtransition for matching improvement of siw horn antennas,” Antennasand Propagation, IEEE Transactions on, vol. 61, no. 4, pp. 1923–1930,2013.[4] J. Liu, D. R. Jackson, and Y. Long, “Substrate integrated waveguide(siw) leaky-wave antenna with transverse slots,” Antennas and Propa-gation, IEEE Transactions on, vol. 60, no. 1, pp. 20–29, 2012.[5] A. R. Mallahzadeh and S. Esfandiarpour, “Wideband h-plane hornantenna based on ridge substrate integrated waveguide (rsiw),” Antennasand Wireless Propagation Letters, IEEE, vol. 11, pp. 85–88, 2012.[6] W. Che, B. Fu, P. Yao, Y. Chow, and E. K. Yung, “A compactsubstrate integrated waveguide h-plane horn antenna with dielectricarc lens,” International Journal of RF and Microwave Computer-AidedEngineering, vol. 17, no. 5, pp. 473–479, 2007.[7] L. Xue and V. Fusco, “Patch fed planar dielectric slab extended hemi-elliptical lens antenna,” Antennas and Propagation, IEEE Transactionson, vol. 56, no. 3, pp. 661–666, 2008.[8] H. Wang, D.-G. Fang, B. Zhang, and W.-Q. Che, “Dielectric loadedsubstrate integrated waveguide (siw)-plane horn antennas,” Antennas andPropagation, IEEE Transactions on, vol. 58, no. 3, pp. 640–647, 2010.[9] M. Bozzi, A. Georgiadis, and K. Wu, “Review of substrate-integratedwaveguide circuits and antennas,” Microwaves, Antennas & Propaga-tion, IET, vol. 5, no. 8, pp. 909–920, 2011.[10] J. Yu, Y. Jiang, X. Lin, Z. Zhu, and Y. Fan, “A four-way half-mode siwpower divider with improved impedance match,” pp. 306–308, 2011.[11] M. E. Morote, B. Fuchs, and R. J. Mosig, “Analytical model of a printedtransition for siw antennas,” in Proc. 6th EuCAP, pp. 414–417, March2012.[12] M. E. Morote, B. Fuchs, J.-F. Zurcher, and R. J. Mosig, “Novel thin andcompact h-plane siw horn antenna,” IEEE Trans. on Antennas, vol. 61,no. 6, pp. 2911–2920, June 2013.[13] A. Belenguer, H. Esteban, and V. Boria, “Novel empty substrate inte-grated waveguide for high-performance microwave integrated circuits,”Microwave Theory and Techniques, IEEE Transactions on, vol. 62, no. 4,pp. 832–839, April 2014.[14] D. M. Pozar, Microwave engineering. John Wiley & Sons, 2009.This is the author's version of an article that has been published in this journal. Changes were made to this version by the publisher prior to publication.The final version of record is available at                                                                             .http://dx.doi.org/10.1109/LAWP.2016.2516103

Highly Efficient and Well-Matched Empty Substrate Integrated Waveguide H-plane Horn Antenna

https://ruidera.uclm.es/xmlui/bitstream/10578/21838/1/IEEEletters2019.pdf

Highly Efficient and Well-Matched Empty Substrate Integrated Waveguide H-plane Horn Antenna

Abstract

Similar works

Full text

Available Versions

Universidad de Castilla-La Mancha: Repositorio Universitario Institucional de Recursos Abiertos (RUIdeRA)