Scattering at an N-Furcated Parallel-Plate Waveguide Junction (Short Paper)

Using the conservation of complex power technique (CCPT), this paper presents a solution to the problem of EM scattering at the junction of a parallel-plate waveguide and an N-furcated parallel-plate waveguide with arbitrarily spaced thick septa. Although this junction can be regarded as an (N + 1)-port configuration, the problem is formulated so that it is viewed mathematically as a generalized 2-port. This leads to very simple expressions for the scattering parameters of the junction. Convergent numerical results are presented for bifurcated, trifurcated, and 4-furcated structures, and the effects of varying the thickness of the septa are investigated. The formulation is directly applicable to N-furcated rectangular waveguide junctions having TE/sub n0/ excitation, with application in the design of E-plane filters.     

The Synthesis of Symmetrical Waveguide Circulators

A method for synthesizing symmetrical waveguide circulators by adjusting the eigenvalues of the scattering matrix is described. This procedure is particularly useful for the design of very compact circulators in the form of waveguide junctions containing ferrite obstacles. Permissible structural symmetries for a circulator are listed, and a standard form for the scattering matrix of a symmetrical circulator is defined. The synthesis procedure is then described in detail, stating the conditions to be imposed on the scattering matrix eigenvalues, and an expression is obtained for the changes in the eigenvalues due to the placing of anisotropic material within the junction. By applying the theory to Allen's 4-port turnstile circulator, it is shown that the use of a matched turnstile junction and a reflectionless Faraday rotator is not essential. The theory is also applied to the design of novel 3- and 4-port circulators, and two 6-port circulators, one of which may be used as a 5-position waveguide switch, are described. Some experimental results are presented for a compact 3-port circulator in the form of an H-plane Y junction, in 1 inch by 1/2 inch waveguide, containing a ferrite post obstacle. This circulator, which operates with a bias field of approximately 25 oersted, has a useful bandwidth of 3 per cent. Greater bandwidths would be expected in a Stripline or a fin-line version of this device.     

Matching Considerations of Lossless Reciprocal 5-Port Waveguide Junctions (Short Papers)

Some of the restrictions imposed on general 5-port junctions (or networks) by losslessness and reciprocity are discussed as well as considerations of restrictions due to physical symmetry. It is proven that if a lossless reciprocal 5-port junction (or network) is completely matched, then all off-diagonal elements of the scattering matrix are nonzero; i.e., if the junction is matched, no port is decoupled from any of the others. It is also shown that all off-diagonal scattering coefficients of a lossless reciprocal 5-port junction (or network) have a magnitude of one half if and only if the junction is completely matched. Those physical symmetries which preclude complete matching of 5-port junctions are given and a general theorem concerning the matching of junctions and physical symmetry is proven.     

Simulated performance of SIS and SIN junctions as heterodyne receivers in waveguide and open antenna mixer mounts

Tucker's quantum theory of mixing (in the 3-port approximation) is employed to calculate the gain over a wide range of frequencies of model mixers employing SIS and SIN junctions with both real and idealI–V characteristics. A comparison is made between the performance of junctions in waveguide and open antenna mounts. It is concluded that ideal junctions give gain 1.5 to 2 times higher than real ones, SIS junctions have gain approximately three times greater than otherwise similar SIN junctions, and that junction areas need to be typically three times smaller in open antenna structures to provide comparable gain to those in waveguide mounts.     

一种判断波导接头模匹配解相对收敛程度的方法

本文从模式隅合的概念出发,详细探讨了波导接头模匹配解的物理意义,并根据Auda和Harrington(1983)的结论导出了一个重要的关系式。该式可用于判断波导接头参数模匹配解的相对收敛程度和确定接头两侧波导模式数的正确比例,从而使为修正而必须进行的两次计算的工作量与一次计算的工作量相当。本文通过两例不同脊高的脊波导接头的模匹配解的具体过程,说明该方法具有较高的实用性和广阔的应用范围。     

Vector-FEM Analysis of Millimeter Wave Circulator with SOC Truncation Technique

In this paper, the application of the edge-based vector finite element method combined with the short-open calibration (SOC) technique to waveguide junction circulators was presented. By applying permittivity and permeability tensors, the functional formula for tetrahedral vector elements are analytically derived in terms of the electric field strength. And the SOC technique is directly accommodated in the FEM algorithm and used to truncate the computational domain. The SOC technique removes or separates unwanted parasitics brought by the approximation of the impressed voltage source and also the problem of resulting inconsistency between different simulations. Truncation of computational domain by SOC technique makes the iterative solvers for large-sparse linear matrix equations from FEM converge much faster than by perfectly matching layers (PML). The analysis of three 2-port networks is sufficient to form the admittance matrix of the corresponding three-port waveguide junction circulators. To validate the theory, typical three-dimensional numerical results of isotropic dielectric-filled discontinuity are first presented and compared with other hybrid numerical techniques. Further, the ferrite filled waveguide junction circulators are analysed and compared with the measured and available publications. The comparison shows that good agreement is obtained.     

Electrodynamical Model of Composite Cylindrical Structure with Laminated Dielectric

The article is devoted to the problem of the natural electromagnetic modes, the regions of their existence and the relationship with all possible types of resonances in the waveguide junction of a cylindrical and radial waveguides with a layered (laminated) filling of the radial waveguide with dielectric material. An electrodynamic model is created on the basis of a rigorous method of modal matching technique, with the separation of the common waveguide coupling region and the representation of the field in it in the form of a superposition of the fields of the partial waveguide eigenmodes. The structure under investigation can be used to measure the electrical parameters of dielectric samples of a cylindrical cross-section. It is shown that the measurements will have a local character, since the spectral characteristics of the junctions are determined mainly by the size of the central coupling region of the waveguides and by the electrical parameters of the dielectric that is in the junction. The problem of edge effects for samples of finite length (partial filling of a radial waveguide with dielectric) is investigated. Taking into account the edge effect enables reducing the error in measuring the permittivity for samples of arbitrary sizes in the investigated structure.     

Frequency Response of Quarter-Wave Coupled Reciprocal Stripline Junctions

The frequency response of quarter-wave coupled reciprocal 3-port symmetrical junctions for which the reference eigennetwork appears as a short circuit at the reference terminals is presented. The equivalent circuit of such reciprocal junctions is constructed in terms of the reciprocal parts of the split admittance eigenvalues of the ideal 3-port circulator. Since the two circuits are related, the element values selected for the matching networks are the ones which apply to an ideal circulator with an overall Chebyshev response. This is done for n=1, 2, and 3. An important conclusion of this paper is that the design of wideband circulators is closely related to the design of wideband reciprocal 3-port junctions. The paper includes experimental results obtained on a stripline device in its magnetized and demagnetized states.     

Efficient analysis of general waveguide multi-port junctions using a segmentation technique and hybrid matrix formulations

In this paper a segmentation technique, based on hybrid (admittance and impedance) matrix representations, is proposed for the efficient and accurate analysis of rectangular waveguide multi-port junctions with arbitrarily shaped waveguide access ports. The technique is completely outlined, and a new method for solving the connection of hybrid matrices without intermediate inversions is derived. To validate the theory, results for a magic-T junction and a six-port cross junction are compared with experimental data from literature. The new method proposed is also successfully applied to H- and E-plane T-junctions with rounded corners in the side arms.     

Application of Deschamps' Graphical Method to Measurements of the Scattering Coefficients of Multiport Waveguide Junctions

A method for measuring scattering coefficients of a multiport waveguide junction is presented. It is based on the application of Deschamps' graphical technique to reduced multiport junctions, and analysis of measurements done with either matched or nearly matched loads terminated at all but the input and output ports. Averaging and least-square fitting are introduced to reduce errors from measurements.     

Scattering at Circular-to-Rectangular Waveguide Junctions

A formally exact solution is given for the problem of scattering at a circular-to-rectangular waveguide junction and at a thick diaphragm, with a centered circular aperture, in a rectangular waveguide. The method uses normal TE and TM mode expansions of the waveguide fields and traditional mode matching of the transverse electric and magnetic fields at the junction boundary. Exact closed-form expressions are obtained for the electric field mode-matching coefficients which couple the TE(TM) modes in the rectangular guide to the TE(TM) and TM(TE) modes in the circular guide. Numerical results are presented for the case of TE/sub 10/ mode propagation in the larger rectangular guide with all other modes cutoff. Convergent numerical results for the equivalent shunt susceptances of such junctions are obtained when about 12 modes (eight TE and four TM) are retained in the circular waveguide or in the circular aperture of the diaphragm. The results are graphically compared with formulas and curves due to the quasi-static theory of Bethe and the variational theory given in the Waveguide Handbook [2].     

一种宽带正交模耦合器的设计

介绍了一种基于对称五端口分支形式的宽带正交模耦合器.对称五端口分支将方波导内的双极化波分离成为水平和垂直2个相互垂直的分量.其特点为:相对于公共波导对称放置的一对相同的波导双接头分配给每一主模,因此每个接头传输主模提供信号一半的能量,双接头的3 dB信号必须用附加的元件适当组合,以便在一个界面端口上提供给定极化总的信号能量.文中介绍的宽带正交模耦合器主要由对称五端口分支、功率合成器及相应的变换段组成.利用阻抗变换原理进行仿真计算,在理论分析的基础上进行了大量的实验研究.最后给出了正交模耦合器在X波段大于90%波导带宽工作的电性能测量结果.     

Numerical analysis of waveguide discontinuity problems using thenetwork model decomposition method

The use of the network model decomposition method for analyzing arbitrarily shaped H- and E-plane waveguide junctions is discussed. By using the polygon discretization technique previously introduced by the author (1990), the waveguide discontinuity region, which is surrounded by a metallic wall and the reference planes chosen, is first discretized; the topological model and the corresponding network model for the waveguide discontinuity are then established. In the formulation, equivalent current sources connected to the nodes on the boundary of the region are introduced to replace the effect of the field external to the region. The field internal to the region is approximated by the nodal voltage distribution of the network model, which can then be used to determine the scattering parameters of the waveguide junction. A diakoptic algorithm for the solution of the network model is also developed. Numerical results for various H- and E-plane junctions are given, and it is shown that the method compares favorably compares with other theories     

A low noise 230 GHz heterodyne receiver employing 0.25-μm2 area Nb-AlOx-Nb tunnel junctions

The authors report recent results for a full-height rectangular waveguide mixer with an integrated IF matching network. Two 0.25 μm ² Nb-AlO_x-Nb superconducting-insulating-superconducting (SIS) tunnel junctions with a current density of ≈8500 A/cm² and ωRC of ≈2.5 at 230 GHz have been tested. One of these quasiparticle tunnel junctions is currently being used at the Caltech Submillimeter Observatory in Hawaii. Detailed measurement of the receiver noise have been made from 200-290 GHz for both junctions at 4.2 K. The lowest receiver noise temperatures were recorded at 239 GHz, measuring 48 K DSB at 4.2 K and 40 K DSB at 2.1 K. The 230-GHz receiver incorporates a one-octave-wide integrated low-pass filter and matching network which transforms the pumped IF junction impedance to 50 Ω over a wide range of impedances     

On Solving TM0n Modal Excitation in a Ka-Band Overmoded Circular Waveguide by the Conservation of Complex Power Technique

To measure the radiation properties of relativistic diffraction generator (RDG) in Ka-band, a TM0n modal excitation model is established, which consists of an overmoded circular waveguide and a coaxial line feeding probe. Using the transverse E-field mode matching and the conservation of complex power technique (CCPT), we deduce the scattering matrix at coaxial line to coaxial line and coaxial line to circular waveguide junctions. Then using the overall cascaded junction scattering matrix, the numerical results for the reflection coefficient of the coaxial line and the power distribution of TM0n multi-modal are presented. The numerical results are in agreement with HFSS simulation results and experimental results. The analysis shows that by choosing the appropriate position of coaxial line probe, the power proportion of the device operating mode excited in circular waveguide could be the largest.     

A Method for Calculating the Frequency-Dependent Properties of Microstrip Discontinuities

A method is described for calculating the dynamical (frequency-dependent) properties of various microstrip discontinuities such as unsymmetrical crossings, T junctions, right-angle bends, impedance steps, and filter elements. The method is applied to an unsymmetrical T junction with three different linewidths. Using a waveguide model with frequency-dependent parameters, a field matching method proposed by Kuhn is employed to compute the scattering matrix of the structures. The elements of the scattering matrix calculated in this way differ from those derived from static methods by a higher frequency dependence, especially for frequencies near the cutoff frequencies of the higher order modes on the microstrip lines. The theoretical results are compared with measurements, and theory and experiment are found to correspond closely.     

On Solving TM0n Modal Excitation in a Ka-Band Overmoded Circular Waveguide by the Conservation of Complex Power Technique

To measure the radiation properties of relativistic diffraction generator (RDG) in Ka-band, a TM0n modal excitation model is established, which consists of an overmoded circular waveguide and a coaxial line feeding probe. Using the transverse E-field mode matching and the conservation of complex power technique (CCPT), we deduce the scattering matrix at coaxial line to coaxial line and coaxial line to circular waveguide junctions. Then using the overall cascaded junction scattering matrix, the numerical results for the reflection coefficient of the coaxial line and the power distribution of TM0n multi-modal are presented. The numerical results are in agreement with HFSS simulation results and experimental results. The analysis shows that by choosing the appropriate position of coaxial line probe, the power proportion of the device operating mode excited in circular waveguide could be the largest.     

A Moment Solution for Waveguide Junction Problems

A moment procedure for solving waveguide junction problems is given using the generalized network formulation for aperture problems. As an illustration, the procedure is applied to a transverse planar junction between two uniform cylindrical waveguides. The generalized admittance network representation of the junction is first obtained. Its scattering matrix representation is then deduced from the former representation. A discussion shows that the conservation of complex power technique, which handles the same class of junctions, is, a specialization of the moment procedure.     

关于模式匹配法相对收敛性问题的研究

本文论证了模式匹配法相对收敛性问题是由于没有取本征模完备正交集中连续的前N项所致。为了解决这一问题,本文提出首先对本征模完备集进行排序,然后进行模式匹配。数值例子计算结果表明,这种先排序的模式匹配法不但很好地解决了相对收敛性问题?而且加快了收敛速度,在本征模个数相同的情况下,能有效地提高解的精度。将这种方法应用于波导接头不连续性问题的分析,结果表明,这种方法具有稳定、精度高和收敛快等优点。     

The Numerical Solution of Rectangular Waveguide Junctions and Discontinuities of Arbitrary Cross Section

A method is described of calculating automatically the performance of junctions of rectangular waveguides including conducting cylinders of arbitrary shape. The only restriction is that the overall problem should he effectively two-dimensional, i.e., the structure be uniform in some cross section. The one basic approximation made (which could be removed) is shown to give useful results for the devices tested, viz., for various shaped irises (inductive and capacitive) and the 4-port H-plane junction.