基片集成波导天线设计

The Research of Broadband Millimeter-Wave Vivaldi Array Antenna Using SIW TechniqueLi Bin Dong Liang Zhao Jiao-cheng(Xi’an Electronic Engineering Research Institute, Xi’an 710100)Abstract-A compact millimeter wave Vivaldi antenna array printed on thick substrate and fed by a substrate integrated waveguide (SIW) structure was proposed in this paper. It consists ofa compact SIW binary divider, which has minimize significantly the feed structure insertion losses and achieve a broadband performance in millimeter wave range, and four-elements printed Vivaldi array. The whole antenna array was designed, fabricated, and thoroughly investigated. The whole antenna and feed net were designed, fabricated on single substrate, which takes the advantages of small size, low profile, low cost and high performance etc. The simulation results show that the design is effective and right.I.I NTRODUCTIONThe Vivaldi array antenna with broadband capability [1] plays a increasingly important position in radar, communication and electronic counter measures (ECM) fields[2,3], which the performance and design have been making an intensive study since 1980s’. With the development of planar integrated circuits, the planar Vivaldi array antenna which is light in weight, low in cost, and intergraded easily, has attracted considerable attention in antenna design filed. The planar Vivaldi array antenna has been based on structure of microstrip[4] or stripline[5], which have been restricted at relatively low frequencies for transmission loss or complex structure. For example, Yang et al.[4] developed a Vivaldi array antenna to cover the 8~12GHz bandwidth, but it was based on the microstrip technology and demonstrated an high insertion loss (over 3.5 dB) for feeding network. Schaubert et al [5] has designed a Vivaldi array antenna with stripline-fed, which has a relatively low insertion loss, but its structure has become very complex.Substrate integrated waveguide (SIW) technology has been proposed for many years [6][7]. Due to the advantages of this technology, such as low cost, high Q-factor, low insertion loss, easy to be integrated and high density layout, SIW is widely used in many areas, for example, planar slot antenna array [8], filter [9], diplexer, hybrid coupler[10], power splitter [11]and so on. The whole SIW structure is composed by metallized via array, so it can be realized accurately by PCB or LTCC technology and can be combined seamlessly with microstrip circuit, which is well suitable for millimeter-wave integrate system design and manufacture.In this paper, a compact millimeter wave vivaldi antenna array with SIW feeding network was presented, which can achieve a broadband performance and offer several advantages over other counterparts such as relatively low insertion loss, good design tolerance and circuit size compactness at the millimeter wave (MMW) range. This antenna configuration can be easily adapted to millimeter wave applications with a conventional low-cost PCB fabrication process. The simulation results indicate that the antenna has good performance in all Ka-band.II.D ESIGN OF BROADBAND MILLIMETER WAVEVIVALDI ANTENNA ELEMENTSIW structures are fabricated on printed circuit boards, which is similar as conventional metallic waveguide structure. The metal layer on surface can be viewed as upper and lower wallof waveguide, and the two lines of metalized via can be viewed as two side-wall of waveguide. Utilizing SIW technology, a number of UWB antenna structure can be used [12].The uniplanar tapered slot antenna also called Vivaldi antenna, which can be easily integrated with the rest of the circuits on a single substrate, has been implemented in many applications [4] since these years for its salient features such as narrow beam width, high element gain, wide bandwidth, and small transverse spacing between array elements. Therefore, it has been widely applied in the development of millimeter-wave integrated circuits and systems.A novel SIW feeding architecture based on the scheme of Vivaldi antenna is proposed and demonstrated with excellent performances in millimeter-wave ka-band. The Vivaldi antenna element is generally easier to match over awideband due to the relatively large tapered slot. Instead of using the wideband balun, a SIW has been employed to feed a Vivaldi antenna. The millimeter-wave Vivaldi antenna by using SIW technology design detailed of the single elementFig.1 millimeter-wave Vivaldi antenna Element structureThe vivadli antenna is assumed to befabricated on Rogers 5880 substrate with athickness of 0.508mm and a relative permittivityof 2.2. The SIW structure is designed to supportTE10 mode in the operating frequency band.This structure is simulated by using AnsoftHFSS and the simulation results are depicted inFig.2. After optimization with Ansoft HFSS, thegeometry parameters for a millimeter-waveVivaldi antenna Element for the 26.5–40 GHzfrequency band are decided as follow: The SIWwide is 4.8mm, the metalized via hole’s diameteris 0.25mm, the space between the via holes is0.5mm, the fifty ohm micorstrip line width is1.6mm，the port width of microstrip matchingsegment is 2.1mm, and the Vivaldi edge curvefunction is y=±0.2e (0.2659x).(a) Electric field distribution in 35GHz(b) VSWR(c) Patterns in different frequency pointFig.2 Simulation results of Vivaldi antenna elementFig.2 (a) shows the field distribution whenantenna working in 35GHz. From the figure,electromagnetic field enter form SMA port andtransmit to SIW feeding port through microstripmatching part then go to Vivaldi antenna.Fig.2(b) is the VSWR curve adjusting to thefrequency change, which is less than 2 infrequency range of 26.5~40GHz. Fig.2 (c) givesthe different work frequency patterns Thesimulation results indicate that the gain in eachfrequency point is a high level, which is form6dB to 10dB, and the 3dB beam width isrelatively wide. So this kind of element issuitable for array design.III.D ESIGN OF BROADBAND MILLIMETER WAVEPOWER DIVISION NETWORKThe developed binary feed networkconstruction is based on the extensive use ofoptimized compact T-junction designs. Basicrules of T-junction designs were previouslydeveloped by [12] through direct translationfrom its metallic waveguide version [13,14] toSIW. The SIW T-power-division is combined ofSIW T-junction and the pin, which the pin hasbeen realized by metalized vias. In thisimplementation, an equivalent “a” dimension ofSIW has been selected to give a relatively widebandwidth for a single stage T-junction, as wellas an acceptable insertion loss. Next, the spacingbetween the combining stages was judiciously selected to achieve a wideband, compact, 1 to 4 power divider in two stages connected in cascade, shown in Fig.3(a). Fig.3(b) shows that the VSWR of the divider is less than 2.5 in frequency range of 26.5~40GHz. The simulation results of divider show that the insertion loss is less than 1.5dB, and the phase balance is less than ±5º in all work frequency, which are shown in Fig.3(c) and (d).This insertion loss is much lower than similar measurements reported by [10]. As mentioned in [16], this type of SIW feeding network can provide a balanced power division over a wide band. Both the balanced power split and low insertion loss should assist with increasing the gain and overall efficiency of the antenna array.(a)1 to 4 wideband power divider structure(b)VSWR(c) Four ports output amplitude(d) Four Ports output phaseFig.3 The simulation results of SIW broadband powerdivider networkIV.F OUR ELEMNTS ARRAY DESIGNThe Vivaldi antenna array is designed andsimulated to operate over a 26.5 to 40GHzfrequency range. It was printed on a 0.508mmthick Rogers RT/duroid 5880 substrate with adielectric constant of 2.2 and a loss tangent of0.001. Fig.4 shows the simulation structuremodel of the four-element Vivaldi array, wherefour Vivaldi antenna elements are fed using aSIW structure feeding network.Fig.4 the antenna simulation structure modelAn E-plane uniform distribution, with abinary feed network, has been chosen to allow auniform excitation over the required wideband.The gain of array increases as the elementsspacing increases. If the antenna has the gratinglobes occurred, the antenna gain drops quickly.The optimum design would be to set the spacingbetween the elements to 0.9λ at the highestoperating frequency. No grating lobes wouldthen appear over the operating band whileachieving the maximum possible gain.The simulation input VSWR and radiationpatterns are shown in Fig. 5(a), (b), (c) & (d).The input VSWR of the array is, for the mostpart, better than 2 over a 13.5GHz bandwidth,which is acceptable. A gain of 12 dB is thelowest over the 13.5GHz bandwidth for thefour-element array. The efficiency of the Vivaldiarray has exceeded 75%. The conductor loss hasbeen significantly reduced in this case. Thereduction in the radiation efficiency is actuallydue to reflection loss rather than conductor loss.(a)Simulation result of VSWR(b) 26.5 GHz pattern(c) 34 GHz pattern(d) 39 GHz patternFig.5 The simulation results of SIW millimeter wavebroadband Vivaldi array antennaV.C ONCLUSIONPerformance of Vivaldi antenna arrays can beenhanced using low-loss feed networks in millimeterwave. SIW technology with emulated waveguides canbe utilized to minimize such losses, especially whencompared to similar structures built using microstriplines. In our implementation, a millimeter wavebroadband Vivaldi array antenna base on SIWstructure was designed and simulated. The simulationresults show that the design is effective and right.The developed Vivaldi antenna array in millimeterwave frequency has high gain, narrow beam width,and a relatively wide bandwidth. The technology isextremely useful for high resolution radar、passiveelectronic detection r and active electronic interferingdue to its low insertion loss and wide bandwidthperformance.R EFERENCES[1] Ehud Gazit. “Improved Design of the Vivaldi Antenna.”IEEE Proceeding ,1988 135 (2) :89~92.[2] Schaubert D H. “Wide Band Phased Arrays of VivaldiNotch Antenna”. IEEE Trans. AntennaPropgat. ,1997 1 :14~17.[3]HiroshiU, Takeshi T, FujiiM. “Development of aintegrated waveguide”, IEEE Trans on MicrowTheory Tech, 1998, 46 (12) : 2438～2443.[4]Cassivi Y, Perregrini L, Arcioni P, BressanM, Wu K.“Dispersion characteristics of substrate integratedrectangular rwaveguide”, IEEEMicrowave WirelessCompon Lett, 2002, 12 (9) : 333～335.[5] Wu, L.-S., R. Wang, and X.-L. Zhou, “Compact foldedsubstrate integrated waveguide cavities and bandpassfilter,” Progress In Electromagnetics Research, PIER84, 135–147, 2008.[6].Zhang, X.-C., Z.-Y. Yu, and J. 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