毕业论文外文翻译-双频微型贴片天线的H-MRTD模拟.docx

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1、外 文 翻 译毕业设计题目：GPS抗干扰天线技术多频带高增益微带天线单元的仿真与设计原文1：H-MRTD simulation of dual-frequency miniature patch antenna译文1：双频微型贴片天线的H-MRTD模拟原文2：A Novel Method for Designing Dual-Frequency Slot Patch Antennas with Two Polarizations译文2：新的双频双极化开槽微带天线的设计方法H-MRTD simulation of dual-frequency miniature patch antennaYU

2、Wen-ge1 , 2, ZHONG Xian-xin1, LI Xiao-yi1, CHEN Shuai1(1. The Key Lab for Optoelectronic Technology &Systems of Ministry of Education ,Chongqing University , Chongqing 400044 , China ;2. Basic Logistical Engineering University , Chongqing 400016 , China)Abstract: A novel MEMS dual-band patch antenna

3、 is designed using slot-loaded and short-circuited size-reduction techniques. By controlling the short-plane width , f10 and f 30 , two resonant frequencies, can be significantly reduced and the frequency radio ( f30/ f10) is tunable in the range 1.72.3.The Haar-Wavelet-Based multiresolution time do

4、main (H-MRTD) is used for modeling and analyzing the antenna for the first time. In addition , the mathematical formulae are extended to an inhomogenous media. Numerical simulation results are compared to those achieved using the conventional 3-D finite-difference time-domain (FDTD) method and measu

5、red. It has been demonstrated that , with this technique , space discretization with only a few cells per wavelength gives accurate results , leading to a reduction of both memory requirements and computation time.Key words : dual-frequency antenna; H-MRTD method ; FDTD method ; MEMS; UPML absorbing

6、 boundary conditions1 Introduction1Recently, patch antenna research has focused on reducing the size of the patch, which is important in many commercial and military applications. It has been shown that the resonant frequency of a microstrip antenna can be significantly reduced by introducing a Shor

7、t-circuited plane or a partly short-circuited plane where the electric field of the resonant mode is zero1-3 , or a short-pin near the feed probe4 . Using two stacked short-circuited patches, dual-frequency operation has been obtained5 . However, the use of a stacked geometry leads to increases in t

8、he thickness and complexity of the patch. In this paper, we demonstrate that by short-circuiting the zero potential plane of a slotted patch excited with a dominant mode (TM10), the resonant frequencies , f 10 and f 30 , of the two operating modes can be approximately halved and can even be signific

9、antly reduced by decreasing the shorted-plane width. This indicates that a large reduction in antenna size can be obtained by using the proposed design , as compared to that of a regular slot-loaded patch.The finite-difference time-domain ( FDTD )method6 is widely used for solving problems related t

10、o electromagnetism. However , there still exist many restrictive factors , such as memory shortage and CPU time , etc. we first adopted the method of the Haar-Wavelet-Based Multiresolution Time Domain ( H-MRTD)7-9with compactly supported scaling function for a full three-dimensional (3-D) wave to Ye

11、e s staggered cell to analyze and simulate the dual frequency microstrip antenna. The major advantage of the MRTD algorithms is their capability to develop real-time time and space adaptive grids through the efficient thresholding of the wavelet coefficients. Using this technique, space discretizati

12、on with only a few cells per wavelength gives accurate results , leading to a reduction of both memory requirement and computation time. Associated with practical model , a uniaxial perfectly matched layer (UPML ) absorbing boundary conditions10 was developed , a three-dimensional formulation of the

13、 discrete difference equations arising from the Maxwell s system is first extended to an inhomogenous medium , it is applied to the analysis of dual-frequency miniature patch antenna.2 Dual-frequency slot-loaded patch antenna2. 1 Design of slot-loaded patch antennaThe lay out of the slot-loaded patc

14、h antenna designed in this paper is shown in Fig. 1. A single slot with dimensions L W is cut in a rectangular patch with dimensions a b with a short-circuited plane of width placed at its other side. The parameters of the antenna are a = 38mm , b = 25mm , L = 36mm ,W =1mm , d = 2mm , h = 3mm , r =

15、1mm , respectively. Owing to being compatible with standard IC technology , and prone to integration with other components ,silicon wafer (r = 11.7) was selected as a layer of microstrip substrate. Between the ground plate and the wafer there is a layer of foam ( r = 1.07) , which could suppress sur

16、face wave induced in the wafer substrate , as a result , the efficiency and the bandwidth of the antenna were increased , and the radiation pattern improved.Fig.1 Geometry of dual-band slot-loaded microstrip antenna2. 2 Measured resultsThe parameters of the slot antenna are selected as above mention

17、ed. The measurements carried out on an Agilent 8720C vector network analyzer. It is then found that, by controlling the shorted-plane width, both the TM10 and TM30 modes are strongly perturbed. Fig. 2 shows typical results of the measured return loss for the cases with s/ a = 1, 0.25, and 0. 1. Rega

18、rding the results shown in Fig. 2, it can be seen that the perturbed TM10 and TM30 modes are excited with good impedance matching. However, when s/ a 0. 1, there no feed point can be found for exciting the two frequencies with good impedance matching. This indicates that there are limitations to the

19、 present dual-band design. It can be seen that the obtained frequency ratio( f 30/ f 10 ) of the two frequencies for present design varies in the range 1. 72. 3. On the other hand, for the case s/ a = 0. 1, shown in Fig. 2, the frequency f10 occurring at 1.562GHz is 0.31 times that (5.038GHz) for a

20、regular half-wavelength patch with the same patch size. In other words, the size of the designed antenna in this paper is much smaller than regular half-wavelength patch antenna.Fig.2 Measured return loss for different shorted-plane widths3 3-D H-MRTD algorithm3. 1 Numerical formulations of the 3-D

21、H-MRTD methodMaxwell s curl equations in an isotropic medium: , (1)where is permittivity, is permeability, is electric conductivity. Each field component is expanded into scaling functions: , (2)And wavelets:, (3)Where, and.Expansion and testing is performed for each spatial coordinate s=x, y, z wit

22、h corresponding discretization indices u=k, l, m,as well as for time with rectangular pulse hn(t). In compact notations, the x-directed electric field component in the staggered Yees grid of size x, y, z is represented as, (4)where x = kx, y = ly, z = mz, t = nt .The summation over includes eight te

23、rms stemming from all the permutations of scaling functions and wavelets: .The representation of the other field components is easily derived through permutation of the indices and follows the same rule as for standard FDTD scheme. Inserting the above expressions into the difference equation and per

24、forming a Galerkin test procedure12 leads to the following expressions for the electric field within each cell k,l,m:, (5)where0 ,1 ,2 ,3denotes , respectively , u , u + 1/ 2 ,u - 1/ 2 , u + 1for each u = k , l , m , n. In formula (5) , there are three different x values within one time step , this

25、brings about inconvenience for program design. In order to avoid the shortcoming, we can adopt approximation as follows:, (6)Similar expressions are obtained for the other field components.3. 2 Absorbing boundary conditionThe field computation domain must be limited in size because the computer can

26、not store an unlimited amount of data. The computation domain must be large enough to enclose the structure of interest. In this paper, we adopted uniaxial perfectly matched layer (UPML) absorbing boundary conditions. Consider one dimension wave equation propagated along + z direction:， (7)where =/,

27、 v is the phase velocity in the concerned volume. Because the conductivity is projected in computation domain, it will result in numeric dispersion if we use directly discrete approximation for formula (7) , Let ，then, its finite difference form is , (9)The difference form of formula (7) is where ar

28、e the MRTD coefficients. The UPML material parameters are chosen to be for the inner computation region. The maximum value of at the end of the UPML region is chosen to be, where is the cell dimension perpendicular to the UMPL interface to the regular region. The UMPL region is backed by a perfect e

29、lectric conductor wall implemented using the mirror principle.4 Computed resultsIn microwave circuit analysis, Gauss impulse is generally selected as an excitation for smoothness in time domain and easy spectrum width setting. The width of Gauss pulse is T = 18ps, assume that the time delay t0 = 3 T

30、 = 54ps, The response value of the frequency domain can be calculated by Fourier transforming the time domain value.The circle wave losses of the antenna computed are shown in Fig. 3 and Fig. 4 for s/ a = 1 and s/ a =0.25, respectively. The computed curves based computation domain 100 120 60 and x=y

31、=0.15mm, z=0.015mm. From Fig. 3 and Fig. 4 , we can find the computed results by using FDTD method , and H-MRTD method are in good agreement with measured results. The drifts between them ensured value and the computed value by using FDTD and H-MRTD are about 2%and 2. 5% in fine-grid, respectively.

32、The length of the novel patch antenna is less than 1/ 7 wavelength, the efficiency this novel antenna arrive at 70%. The characteristic parameters such as effective dielectric constant, the characteristic impedance in spectrum domain could be worked out by Fourier transform.Fig.3 Computed return los

33、s for s/a=1Fig.4 Computed return loss for s/a=0.25These simulations were performed by XFDTD, the information about dual-frequency antenna simulations is shown in Tab. 1. We can find when using different space cell sizes, there will be different simulation results. For FDTD method, Although time-step

34、 selected satisfied the Courant-Friedrich-Levy (CFL) condition13 , the accuracy of the simulation results appears diverse when we adopt fine-grid and coarse-grid , respectively, it makes clear the numeric errors arrive at 12% in coarse-grid case for FDTD method. It manifests not only time-step but a

35、lso the size of space-steps affect greatly the numeric errors of FDTD method. If the space-steps change more and more larger, its numeric precision can not be assured. For H-MRTD method, because of the capability of the MRTD algorithms to develop real-time and space adaptive grids through the effici

36、ent thresholding of the wavelet coefficients. Space discretization with only a few cells per wavelength gives accurate results, the influence of the space-steps is smaller than FDTD method, but there are larger numeric errors compared with FDTD method in fine-grid case. Although the time-step of FDT

37、D method is nearly 3 times that of H-MRTD method , The CPU time is quite approximation. This fact is proved to be a serious drawback that the addition of wavelets does not improve significantly the numeric accuracy of the FDTD scheme. I t is a hot and highlighted now to study how to improve the nume

38、ric accuracy of the H-MRTD method.Tab.1 Information on the dual-frequency antennaNO. of Yees cellConditionsFDTDH-MRTD10012060t0.0915ns0.0315nsError(%)2%3.5%CPU time(s)5300s5340s202412t0.1385ns0.0895nsError(%)12%4.5%CPU time(s)39002000s563t_0.1nsError(%)_5.7%CPU time(s)_10005 Conclusion A dual-freque

39、ncy miniature patch antenna is presented in this paper, it performs excellently and especially in miniaturization. H-MRTD method was used to model the structure of the antenna. The algorithm of the method is real-time time and space adaptive grids through the efficient thresholding of the wavelet co

40、efficients. Thus, space discretization with only a few cells per wavelength gives accurate results, leading to a reduction of both memory requirement and computation time. The fact that there is a good agreement between the H-MRTD computed values and the measured results or FDTD computed values mani

41、fests that the 3-D H-MRTD method is more efficient than the conventional FDTD method. But yet, there still exist some problems, such as the accuracy of numeric simulation and the far field radiation patterns at the two operating frequencies et al , which need to be solved , They will bediscussed in

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