共查询到20条相似文献,搜索用时 187 毫秒
1.
Guo Y.J. Paez A. Sadeghzadeh R.A. Barton S.K. 《Antennas and Propagation, IEEE Transactions on》1997,45(1):177-178
A TM02-mode circular patch antenna for the application of radio LANs is reported. An experimental prototype operating at 5.2 GHz is designed and tested. The antenna pattern is omnidirectional in azimuth and has a notch in the normal direction. A 3.3% bandwidth of VSWR ⩽2 and 4.2-dB antenna gain were measured. Experimental results agree well with theoretical predictions 相似文献
2.
In this paper, we report the design methodology and numerical results for two mode converters that are suitable for high-power microwave applications. Both converters are designed to operate at 11.424 GHz and utilize periodic serpentine structures to convert between modes with different azimuthal-mode indexes. The first converts about 98.5% of an incident linearly polarized TE12 mode to the TE 01 mode when oriented as an H-plane bend, but has just 1% mode conversion to all modes when oriented as an E-plane bend. The second device converts a linearly polarized TE11 mode to a TM 01 mode with over 99.99% effectiveness. The performance of both devices with respect to parametric variations is detailed. Experimental measurements of the radiation patterns from the TE12 -to-TE01-mode converter are consistent with the theoretical predictions 相似文献
3.
Numerical solution of higher order mode cutoff frequencies inasymmetric TEM cells by Galerkin method
Jaehoon Yun Hyuckjae Lee Jungki Kim 《Electromagnetic Compatibility, IEEE Transactions on》1999,41(4):273-279
The authors describe a Galerkin method (GM), which determines efficiently the basis functions satisfying the edge conditions and the size of the elements on the Neumann boundaries in this paper. The calculated higher order mode cutoff frequencies in both symmetric and asymmetric TEM cells by the GM are presented. The authors could then solve the technical debate for TE12-, TE03-, TM 11-, and TM12-mode cutoff frequencies in the symmetric TEM cell. It is also shown that the measured resonant frequencies of a designed asymmetric TEM cell agree well with the predicted data by the GM 相似文献
4.
Perturbation formulas for TE011-mode dielectric rod resonator and for a TE011-mode circular cavity resonator are derived to determine the surface impedance Z s of superconductors from measured values of resonant frequencies and unloaded Q . The relation between the maximum surface current density of a superconductor, J s, and output power from a signal generator is derived. On the basis of these analytical results, a measurement technique is proposed to evaluate the temperature and J s dependencies of Z s for superconductors. The measured results of the temperature dependence of Z s for YBCO and copper plates are presented. From these results, it is verified that the dielectric resonator is suitable for measuring the surface reactance for YBCO. From these Z s values the temperature dependences of the skin depth and the penetration depth and those of the complex conductivity are obtained on the basis of the two-fluid model. These measured values agree well with the theoretical curves 相似文献
5.
Commonly, the classical formulas are suitable for designing the TE21-mode coupler for the operating frequency under Ka-band by ignoring the wall thickness. However, in practice, for the one operated in the Ka-band, such classical formulas are not valid and the effect of wall thicknesses should be considered. Herein, we propose a design method for the Ka-band TE21-mode coupler via computer simulations, taking into account the wall thickness. The experimental results show that using the linear twice-weighted algorithm to optimize the coupling hole size can improve the coupler performance. And the bandwidth of such coupler increases by 10% with lower coupling loss (<0.5 dB) and higher isolation (> 40 dB). 相似文献
6.
The TE11-mode excitation of a concentric circular iris of finite thickness in a circular waveguide is analyzed by Galerkin's method with even and odd excitation. Agreement between calculated and measured dominant mode scattering parameters is generally within experimental accuracy 相似文献
7.
Kwok Wa Leung 《Microwave Theory and Techniques》2001,49(3):524-531
The probe-fed hemispherical dielectric-resonator antenna (DRA) with a concentric conductor is studied theoretically in this paper. Using the mode-matching method, the exact Green's functions for evaluation of the input impedance and radiation patterns are found, with the functions presented in computationally efficient forms. The moment method is used to determine the probe current and, hence, the input impedance as well as the radiation patterns. The results are verified by special cases available in the literature. In this paper, the effects of the conductor radius, dielectric constant, probe length, and probe displacement on the input impedance are investigated. The theory is very general and, by taking appropriate limits, can be used to study the solid DRA and the conductor-loaded wire antenna. To aid the DRA design engineer, the TE111-mode characteristic equation of the DRA is also studied, from which the simple formulas for the resonant frequency and Q-factor are obtained 相似文献
8.
Vermeulen F.E. Wang T. James C.R. Robinson A.M. 《Lightwave Technology, Journal of》1993,11(12):1956-1964
Theoretical and numerical results are presented on the propagation of infrared radiation in TE01-, TM01-, and TE11-like modes in an empty cylindrical, gold-coated waveguide of micron dimensions. Low-loss propagation is possible for the TE01-like mode, whose configuration is similar to that of the TE01 mode in a guide with perfectly conducting walls. Propagation is more lossy for the TM01- and TE11-like modes. While for small guide radii these modes resemble the TM01 and TE11 modes in a guide with perfectly conducting walls, they transform into surface waves as the guide radius is increased, with losses that are independent of guide radius 相似文献
9.
The design and analysis of iris-coupled and dielectric-loaded 1/8-cut TE01-mode filters is performed using globalized local solutions of Maxwell's equations as basis functions. It is found that this set of basis functions outperforms other edge-conditioned basis functions. To reduce the size of the filter and increase the Q factor of the resonators, dielectric rings with high dielectric constant are employed in the same design technique. The dimensions of the resonators are determined to accurately take into account the effect of coupling on their resonant frequencies, thereby reducing the need of tuning. Numerical results are compared with those obtained from the finite-element method (HP HFSS) and the mode-matching technique. Good agreement is demonstrated 相似文献
10.
近年来,为解决传统介质谐振器天线(dielectric resonator antenna, DRA)体积庞大等问题,新颖的低剖面DRA如介质贴片天线和平面介质天线被提出并迅速成为研究热点.然而,现有的低剖面DRA设计要么平面尺寸较大(>0.5λ0×0.5λ0),要么带宽较窄(<10%),限制了它们的实际应用.文中提出了一种具有小型化平面尺寸的宽带低剖面DRA.本天线采用介质贴片设计,顶部为高介电常数的介质贴片,中间为低介电常数的介质基板,底部为缝隙馈电结构.缝隙馈电结构可激励起介质贴片谐振器的基模TE111和高次模TE131两种工作模式,这两种模式的场分布在贴片边缘部分存在基模场强较弱而高次模场强较强的显著区别.本设计巧妙地利用了该区域的模式场强区别,通过略微增加贴片边缘部分高度来显著影响高次模谐振频率而轻微影响基模谐振频率,从而将高次模TE131的谐振频率迅速下拉并与基模TE111的谐振频率靠近合并,在不增大介质贴片平面尺寸的前提条件下获得宽带工作效果.本天线的三维尺寸为0.35λ0×0.35λ0×0.08λ0 (λ0为中心频率处的空气中波长),线极化实物案例测试结果表... 相似文献
11.
Tien-Jung Chen Shu-Hsia Chen 《Lightwave Technology, Journal of》1995,13(8):1698-1705
The propagation behavior of the four lower-order modes, HE11 , TE01, TM01, and HE21, in a radially anisotropic cylindrical waveguide with liquid crystal cladding is studied both theoretically and experimentally. The cylindrical waveguide is a doubly-clad fiber with an isotropic core and inner cladding and a radially anisotropic outer cladding made of nematic liquid crystal. Theoretically, the propagation and decay constants for the TE01 and TM01 modes are obtained by solving the wave equations exactly, while those for the HE11 and HE 21 modes are derived using perturbation techniques under the weakly guiding approximation. It is predicted that in such a structure the guided TE01 mode can be separated from the leaky HE11, TM01, and HE21 modes. The theoretical results show good agreement with the experimental observations for a 3 cm long fiber cell with a 5 μm inner cladding radius 相似文献
12.
The result of Yee et al. (1968) for the parallel-plane TE10 -mode reflection coefficient, used in Jull's (1972) formulation for the reflection coefficient of a long E-plane sectoral horn, is replaced by the Boersma's (1974) corresponding result. At longer wavelengths, the expression that emerges displays a much better match with experiments than Jull's original expressions 相似文献
13.
This paper presents the first systematic evaluation and analysis of 60-GHz-band TE01δ-mode cylindrical dielectric resonators coupled to a microstrip line on a GaAs substrate. The loss components of the unloaded Q are analyzed using simple numerical techniques. The distance between the resonator center and the microstrip line which gives the maximum coupling coefficient is found to be approximately 3/5 of the resonator radius, whose ratio is almost constant for all practical cases. The temperature characteristics are also demonstrated and the origins of temperature dependences of the unloaded Q and the coupling coefficient are discussed. An equivalent circuit model for the dielectric resonator coupled to the microstrip line is presented, whose element parameters can express the dependences of the resonant frequency, the unloaded Q, and the coupling coefficient on the structural parameters and the temperature 相似文献
14.
Designs of compact quasi-periodic and aperiodic TE0n-TE 0n-1 circular waveguide converters for use with gyrotrons in an electron cyclotron heating (ECH) system are developed by analytically and numerically solving the coupled-mode differential equations. Quasi-periodic mode transducer designs which convert the TE02 mode to the TE01 mode, and in some cases also include a taper (waveguide radius reduction), are developed. A 60-GHz aperiodic mode converter-taper combines a 6.35-cm-2.779-cm waveguide diameter taper and a TE02-TE01 mode converter. A 140-GHz aperiodic mode converter-taper combines a 6.35-cm-2.779-cm waveguide diameter taper and a TE03-TE02-TE01 mode converter. The resulting designs are highly efficient (conversion efficiencies ⩾99.4%), are shorter, have a broader bandwidth than previous designs, and have a waveguide radius greater than or equal to 1.389 cm over the entire length of the transducer to allow for high-power transmission. Experimental results consistent with theoretical calculations are presented 相似文献
15.
An integral equation for the transverse electric (TE) field in the aperture of a concentric circular iris in a transverse plane of a circular waveguide is approximately solved using Galerkin's method. The aperture field is represented by a finite sum of normal TE and TM (transverse magnetic) circular waveguide modes that fit the circular aperture. The numerical convergence of the Galerkin solution is demonstrated using the resultant aperture field distributions and equivalent shunt susceptance for the case of dominant TE11-mode excitation. The resultant aperture electric field distribution closely resembles that of the TE11 aperture mode alone, except for edge contribution behavior at the edge of the iris. A resonant or capacitive iris is possible over a restricted range of frequencies 相似文献
16.
A moment method is used to plot the electromagnetic field of an inductive window in a TE10-mode rectangular waveguide. Green's dyadic functions are derived based on Tai's approach, which is a modified form of Hansen's vector wave functions. Based on the computed electric fields, the S matrix and the equivalent aperture reactance of the waveguide window are calculated. This calculation agrees with the previously published closed-form results of N. Marcuvitz (1964) 相似文献
17.
Xiao-Hui Zhu Dai-Zong Chen Shi-Jin Wang 《Microwave Theory and Techniques》1991,39(10):1762-1766
A moment method technique for solving obstacle problems in a waveguide is presented. Instead of using a multifilament current representation, which leads to a slowly converging series, a multistrip representation of the current is proposed. In the procedure, the matrix elements are determined by a series involving integrals of mode functions over the strips and the convergence is improved. The true currents on obstacle surfaces are replaced by equivalent planar currents in a number of waveguide cross sections inside the obstacle. The technique is applied to a pair of metallic posts in the TE11-mode circular waveguide. Numerical results are compared with experimental data 相似文献
18.
Leung K.W. Luk K.M. Lai K.Y.A. Lin D. 《Antennas and Propagation, IEEE Transactions on》1993,41(10):1390-1398
A hemispherical dielectric resonator antenna fed by a coaxial probe is studied both theoretically and experimentally. The Green's function for the evaluation of the input impedance is derived rigorously and expressed in a form convenient for numerical computations. The method of moments is used to obtain the probe current from which the input impedance of the DR antenna is calculated. Both delta gap and magnetic frill source models are considered. Moreover, the results using a reduced kernel as well as the exact kernel are presented. Both entire basis (EB) and piecewise sinusoidal (PWS) expansion modes are used and the results are compared. The effects of the probe length, feed position, and dielectric constant on the input impedance are discussed. Finally, the theoretical radiation patterns for the first three resonant modes (TE111, TM101, and TE221) of the DR antenna are presented 相似文献
19.
It is shown that due to the similarity of the structures of the TEM cell and the finned waveguide, the closed-form expression for the cutoff frequency of the TE10 mode in the finned waveguides can be used to calculate the cutoff frequency of the TE01 mode in the symmetric TEM cells. The results obtained by the expression given agree with various numerical methods to within 1%. The results calculated by this expression are compared with those obtained by an approximate analytical expression 相似文献
20.
Shanjia Xu Jianhua Min Song-Tsuen Peng Schwering F.K. 《Antennas and Propagation, IEEE Transactions on》1991,39(7):883-891
A millimetre-wave omnidirectional circular dielectric rod grating antenna is investigated theoretically and experimentally. As an eigenvalue problem, the antenna is analyzed with the rigorous mode matching method. The radiation characteristics of the antenna are calculated and measured in the Ka -band frequency range. A comparison between the experimental results and the theoretical predictions is made and good agreement is found. The practicality of the omnidirectional antenna and the effectiveness of the theory are thus justified 相似文献