2022年微带耦合器的中英文对照翻译借鉴 .pdf
Design and Analysis of Wideband Nonuniform Branch Line Coupler and Its Application in a Wideband Butler Matrix Yuli K.Ningsih,1,2 M.Asvial,1 and E.T.Rahardjo Antenna Propagation and Microwave Research Group(AMRG),Department of Electrical Engineering,Universitas Indonesia,New Campus UI,West Java,Depok 16424,Indonesia Department of Electrical Engineering,Trisakti University,Kyai Tapa,Grogol,West Jakarta 11440,Indonesia Received 10 August 2011;Accepted 2 December 2011 Academic Editor:Tayeb A.Denwdny Copyright?2012 Yuli K.Ningsih et al.This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use,distribution,and reproduction in any medium,provided the original work is properly cited.Abstract This paper presents a novel wideband nonuniform branch line coupler.An exponential impedance taper is inserted,at the series arms of the branch line coupler,to enhance the bandwidth.The behavior of the nonuniform coupler was mathematically analyzed,and its design of scattering matrix was derived.For a return loss better than 10?dB,it achieved 61.1%bandwidth centered at 9GHz.Measured coupling magnitudes and phase exhibit good dispersive characteristic.For the 1dB magnitude difference and phase error within 3,it achieved 22.2%bandwidth centered at 9GHz.Furthermore,the novel branch line coupler was implemented for a wideband crossover.Crossover was constructed by cascading two wideband nonuniform branch line couplers.These components were employed to design a wideband Butler Matrix working at 9.4GHz.The measurement results show that the reflection coefficient between the output ports is better than 18dB across 8.0GHz 9.6GHz,and the overall phase error is less than 7.1.Introduction Recently,a switched-beam antenna system has been widely used in numerous applications,such as in mobile communication system,satellite system,and modern multifunction radar.This is due to the ability of the switched-beam antenna to decrease the interference and to improve the quality of transmission and also to increase gain and diversity.The switched-beam system consists of a multibeam switching network and antenna array.The principle of a switched-beam is based on feeding a signal into an array of antenna with equal power and phase difference.Different structures of multibeam switching networks have been proposed,such as the Blass Matrix,the Nolen Matrix,the Rotman Lens,and the Butler Matrix.名师资料总结-精品资料欢迎下载-名师精心整理-第 1 页，共 19 页 -One of the most widely known multibeam switching networks with a linear antenna is the Butler Matrix.Indeed,it seems to be the most attractive option due to its design simplicity and low power loss.In general,the Butler Matrix is an N N passive feeding network,composed of branch line coupler,crossover,and phase shifter.The bandwidth of the Butler Matrix is greatly dependent on the performance of the components.However,the Butler Matrix has a narrow bandwidth characteristic due to branch line coupler and crossover has a limited bandwidth.As there is an increased demand to provide high data throughput,it is essential that the Butler Matrix has to operate over a wide frequency band when used for angle diversity.Therefore,many papers have reported for the bandwidth enhancement of branch line coupler.In reference,design and realization of branch line coupler on multilayer microstrip structure was reported.These designs can achieve a wideband characteristic.However,the disadvantages of these designs are large in dimension and bulk.Reference introduces a compact coupler in an N-section tandem-connected structure.The design resulted in a wide bandwidth.Another design,two elliptically shaped microstrip lines which are broadside coupled through an elliptically shaped slot,was employed in.This design was used in a UWB coupler with high return loss and isolation.However,these designs require a more complex manufacturing.In this paper,nonuniform branch line coupler using exponential impedance taper is proposed which can enhance bandwidth and can be implemented for Butler Matrix,as shown in Figure 1.Moreover,it is a simple design without needs of using multilayer technology.This will lead in cost reduction and in design simplification.Figure 1:Geometry structure of a new nonuniform branch line coupler design with exponential impedance taper at the series arm.To design the new branch line coupler,firstly,the series arm s impedance is modified.The shunt arm remains unchanged.Reduced of the width of the transmission line at this arm is desired by modifying the series arm.Next,by exponential impedance taper at the series arm,a good match over a high frequency can be achieved.2.Mathematical Analysis of Nonuniform Branch Line Coupler The proposed nonuniform branch line coupler use /4 branches with impedance of 50 at the shunt arms and use the exponential impedance taper at the series arms,as shown in Figure 1.Since branch line coupler has a symmetric structure,the even-odd mode theory can be employed to analyze the nonuniform characteristics.The four ports can be simplified to a two-port problem in which the even and odd mode signals are fed to two collinear inputs 22.Figure 2 shows the schematic of circuit the nonuniform branch line coupiers.名师资料总结-精品资料欢迎下载-名师精心整理-第 2 页，共 19 页 -Figure 2:Circuit of the nonuniform branch line coupler.The circuit of Figure 2 can be decomposed into the superposition of an even-mode excitation and an odd-mode excitation is shown in Figures and.Figure 3:Decomposition of the nonuniform branch line coupler into even and odd modes of excitation.The ABCD matrices of each mode can be expressed following.In the case of nonuniform branch line coupler,the matrices for the even and odd modes become:A branch line coupler has been designed based on the theory of small reflection,by the continuously tapered line with exponential tapers,as indicated in Figure 1,where which determines the constant as:名师资料总结-精品资料欢迎下载-名师精心整理-第 3 页，共 19 页 -Useful conversions for two-port network parameters for the even and odd modes of S11and S21 can be defined as follows:whereSince the amplitude of the incident waves for these two ports are 1/2,the amplitudes of the emerging wave at each port of the nonuniform branch line coupler can be expressed as Parameters even and odd modes of S11 nonuniform branch line coupler can be expressed as and as follows:名师资料总结-精品资料欢迎下载-名师精心整理-第 4 页，共 19 页 -An ideal branch line coupler is designed to have zero reflection power and splits the input power in port 1(P1)into equal powers in port 3(P3)and port 4(P4).Considering to,a number of properties of the ideal branch line coupler maybe deduced from the symmetry and unitary properties of its scattering matrix.If the series and shunt arm are one-quarter wavelength,by using,resulted in S11=0.As both the even and odd modes of S11 are 0,the values of S11 and S21 are also 0.The magnitude of the signal at the coupled port is then the same as that of the input port.Calculating and under the same,the even and odd modes of S21 nonuniform branch line coupler will be expressed as follows in Based on,S11 can be expressed as follows Following,S41 nonuniform branch line coupler can be calculating as follows From this result,both S31 and S41 nonuniform branch line couplers have equal magnitudes of-3dB.Therefore,due to symmetry property,we also have thatS11=S22=S33=S44=0,S13=S31，S14=S41，S21=S34,and.Therefore,the nonuniform branch line coupler has the following scattering matrix in 名师资料总结-精品资料欢迎下载-名师精心整理-第 5 页，共 19 页 -3.Fabrication and Measurement Result of Wideband Nonuniform Branch Line Coupler To verify the equation,the nonuniform branch line coupler was implemented and its-parameter was measured.It was integrated on TLY substrate,which has a thickness of 1.57mm.Figure 4 shows a photograph of a wideband nonuniform branch line coupler.Each branch at the series arm comprises an exponentially tapered microstrip line which transforms the impedance from ohms to ohms.This impedance transformation has been designed across a discrete step length mm.Figure 4:Photograph of a proposed nonuniform branch line coupler.Figure 5 shows the measured result frequency response of the novel nonuniform branch line coupler.For a return loss and isolation better than 10dB,it has a bandwidth of about 61.1%;it extends from 7 to 12.5GHz.In this bandwidth,the coupling ratio varies between 2.6?dB up to 5.1dB.If the coupling ratio is supposed approximately 3 1dB,the bandwidth of about 22.2%centered at 9GHz.Figure 5:Measurement result for nonuniform branch line coupler.As expected,the phase difference between port 3(P3)and port 4(P4)is 90 .At 9?GHz,the phases of and are 85.54 and 171 ,respectively.These values differ from ideal value by 4.54.The average phase error or phase unbalance between two branch line coupler outputs is about 3.But even the phase varies with frequency;the phase difference is almost constant and very close to ideal value of 90 as shown in Figure 6.Figure 6:Phase characteristic of nonuniform branch line coupler.4.Design and Fabrication of the Wideband Butler Matrix Figure 7 shows the basic schematic of the Butler Matrix.Crossover also known as 0dB couplers is a four-port device and must provide for a very good matching and isolation,while the transmitted signal should not be affected.In order to achieve wideband characteristic crossover,this paper proposes the cascade of two nonuniform branch line couplers.名师资料总结-精品资料欢迎下载-名师精心整理-第 6 页，共 19 页 -Figure 7:Basic schematic of the Butler Matrix.Figure 8 shows the microstrip layout of the optimized crossover.The crossover has a frequency bandwidth of 1.3GHz with VSWR=2,which is about 22.2%of its centre frequency at 9?GHz.Thus,it is clear from these results that a nonuniform crossover fulfills most of the required specifications,as shown in Figure 9.Figure 8:Photograph of microstrip nonuniform crossover.Figure 9:Measurement result for nonuniform crossover.Figure 10 shows the layout of the proposed wideband Butler Matrix.This matrix uses wideband nonuniform branch line coupler,wideband nonuniform crossover,and phase-shift transmission lines.Figure 10:Final layout of the proposed wideband Butler Matrix.The wideband Butler Matrix was measured using Network Analyzer.Figure 11 shows the simulation and measurement results of insertion loss when a signal was fed into port 1,port 2,port 3,and port 4,respectively.The insertion loss are varies between 5dB up to 10dB.For the ideal Butler matrix,it should be better than 6dB.Imperfection of fabrication could contribute to reduction of the insertion loss.Figure 11:Insertion loss of the proposed Butler Matrix when different ports are fed.The simulated and measured results of the return loss at each port of the widedend Butler Matrix is shown in Figure 12.For a return loss better than 10dB,it has a bandwidth about 名师资料总结-精品资料欢迎下载-名师精心整理-第 7 页，共 19 页 -17%centered at 9.4GHz.Figure 12:Return loss of the proposed Butler Matrix when different ports are fed.Figure 13 shows the phase difference of measured results when a signal was fed into port 1,port 2,port 3,and port 4,respectively.The overall phase error was less than 7.There are several possible reasons for this phase error.A lot of bends in high frequency can produce phase error.Moreover,the imperfection of soldering,etching,alignment,and fastening also could contribute to deviation of the phase error.Figure 13:Phase difference of the proposed Butler Matrix when different ports are fed.Table 1 shows that each input port was resulted a specific linear phase at the output ports.The phase differences each between the output ports are of the same value.The phase difference can generate a different beam().If port 1(P1)is excited,the phase difference was 45,the direction of generated beam()will be 14.4 for 1L.It is summarized in Table 1.Table 1:Output phase difference and estimated direction of generated beam.5.Conclusion A novel nonuniform branch line coupler has been employed to achieve a wideband characteristic by exponential impedance taper technique.It is a simple design without needs of using multilayer technology and this will lead to cost reduction and design simplification.The scattering matrix of the nonuniform branch line coupler was derived and it was proved that the nonuniform branch line coupler has equal magnitude of-3dB.Moreover,the novel nonuniform branch line coupler has been employed to achieve a wideband 0dB crossover.Furthermore,these components have been implemented in the Butler Matrix and that achieves wideband characteristics.References T.A.Denidni and T.E.Libar,“Wide band four-port butler matrix for switched multibeam antenna arrays,”in Proceedings of the IEEE International Symposium on Personal,Indoor and Mobile Radio Communications(PIMRC 03),vol.3,pp.2461 2464,2003.View at Publisher View at Google Scholar 名师资料总结-精品资料欢迎下载-名师精心整理-第 8 页，共 19 页 -E.Siachalou,E.Vafiadis,S.S.Goudos,T.Samaras,C.S.Koukourlis,and 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