Multiport Junctions Research Articles

Concurrent Dual-Band Heterodyne Interferometric Receiver for Multistandard and Multifunction Wireless Systems

Radio frequency (RF), microwave, and millimeter-wave (mmW) multiport interferometric receivers present a competitive solution for the front-end reception of low-power multistandard and multifunction wireless applications. The systematic generation of rectified waves in a conventional direct-conversion interferometric receiver is highly related to temporal and power changes and the number of subsignals in the frequency band of interest. It can cause the receiver to saturate and, thus, requires auxiliary power-hungry tunable amplifiers and a data converter for compensation. This work presents a heterodyne detection in an RF/microwave interferometric receiver, the first of its kind, which separates the desired frequency signals from the rectified wave components with two output ports through a frequency offset. This architecture also makes use of the field-effect transistor (FET)-based power detectors to combine the received and reference signals, which reduces a theoretical multiport junction loss of 6 dB to 3 dB. In this way, the proposed receiver is set to support the development of an ultralow-power concurrent dual-band wireless system using a single wave-correlator circuit. A mathematical model of the proposed system is derived and subsequently prototyped using off-the-shelf components to evaluate its carrier-to-noise power ratio (CNR) and error vector magnitude (EVM) performances, which can be extended for integrated circuits (ICs) implementation, such as CMOS and III–V ICs. The power detectors only require a bias voltage at gate terminals with zero direct current (dc) power consumption for optimum voltage responsivity and CNR performances. The demodulation of various modulated digital signals, including QPSK, QAM-16, QAM-32, and QAM-64, has been successfully demonstrated in the 24- and 28-GHz mmW frequency bands at 4 MSps of the symbol rate with a maximum EVM of 11.43% root-mean-square (rms) free from any postprocessing linearization and calibration.

Steady State Response of Linear Time Invariant Systems Modeledby Multibond Graphs

The direct determination of the steady state response for linear time invariant (LTI) systems modeled by multibond graphs is presented. Firstly, a multiport junction structure of a multibond graph in an integral causality assignment (MBGI) to get the state space of the system is introduced. By assigning a derivative causality to the multiport storage elements, the multibond graph in a derivative causality (MBGD) is proposed. Based on this MBGD, a theorem to obtain the steady state response is presented. Two case studies to get the steady state of the state variables are applied. Both cases are modeled by multibond graphs, and the symbolic determination of the steady state is obtained. The simulation results using the 20-SIM software are numerically verified.

Miniaturized Single-Ended and Balanced Dual-Band Diplexers Using Dielectric Resonators

Compact dual-band diplexers with single-ended and balanced ports based on quad-mode dielectric resonators (DRs) are proposed in this article. Two pairs of orthogonal degenerate modes are employed not only to form four frequency channels but also to achieve high isolation of dual-band diplexer. Quad-mode field distributions and couplings with input and output probes are analyzed in detail to realize dual-band diplexer characteristics. Due to the couplings of straight probes and sharing of common input and output quad-mode DRs, multiport junctions in conventional designs are saved, and the number of resonators is remarkably reduced. Therefore, miniaturized sizes are obtained in both single-ended and balanced designs. For verification, Sub-6-GHz dual-band diplexers with single-ended and balanced ports are fabricated and measured. With only two cuboid DRs and three sets of probes, low losses in all four bands and isolations that better than 34 dB are achieved in both two designs. Moreover, the common-mode (CM) suppression of the balanced diplexer is better than 50 dB. The exhibited high in- and out-of-band performance of the diplexers demonstrates the proposed method.

$K$ -Band Phase Discriminator Using Multiport Downconversion for Monopulse Tracker

In this letter, K-band phase discriminator based on multiport downconversion for monopulse tracking system is presented. The proposed architecture adopts multiple six-port junctions to individually process elevation and azimuth difference signals delivered from a multibeam antenna feed network. To produce accurate 2-D angular information, elevation and azimuth difference channel path calibration by reflection-type phase shifters and attenuators are also used. The proposed hybrid multiport junction was implemented with microstrip passive circuits and GaAs monolithic microwave integrated circuits. The performance was verified at the satellite downlink frequency of 20 GHz by successful generations of quadrature I/Q signals according to elevation or azimuth difference signal variations.

Ключевой алгоритм метода частичных областей в анализе резонансных штырей, тройниковых, турникетных и некоторых других многоплечих соединений

Ключевой алгоритм метода частичных областей в анализе резонансных штырей, тройниковых, турникетных и некоторых других многоплечих соединений

Compensation of the impact of low‐cost manufacturing techniques in the design of E‐plane multiport waveguide junctions

AbstractIn this work, a full‐wave tool for the accurate analysis and design of compensated E‐plane multiport junctions is proposed. The implemented tool is capable of evaluating the undesired effects related to the use of low‐cost manufacturing techniques, which are mostly due to the introduction of rounded corners in the cross section of the rectangular waveguides of the device. The obtained results show that, although stringent mechanical effects are imposed, it is possible to compensate for the impact of the cited low‐cost manufacturing techniques by redesigning the matching elements considered in the original device. Several new designs concerning a great variety of E‐plane components (such as right‐angled bends, T‐junctions and magic‐Ts) are presented, and useful design guidelines are provided. The implemented tool, which is mainly based on the boundary integral‐resonant mode expansion technique, has been successfully validated by comparing the obtained results to simulated data provided by a commercial software based on the finite element method.

Modelling and Characterization of Planar Components

An approach for modeling and numerical simulation of planar components using the edge line concept is developed. With this method, we develop an efficient modeling technique for microstrip discontinuities. The structure presents an arbitrary number of ports, each one with different orientation and dimensions. This article presents a hybrid method based on multimode contour integral and mode matching techniques. The process is based on segmentation and dividing the structure into key building blocks. We use the multimode contour integral method to analyze the blocks including irregular shape discontinuities. Finally, the multimode scattering matrix of the whole structure can be found by cascading the blocks. Therefore, the new method is suitable for analysis of a wide range of waveguide problems. Therefore the present approach can be applied easily to the analysis of any multiport junctions and cascade blocks. The accuracy of the method is validated comparing with results for several complex problems found in the literature. CPU times are also included showing the efficiency of the new method proposed.

Modeling and Simulation of Microwave Circuits

A new and efficient method is presented for the analysis of arbitrarily shaped discontinuities. The technique obtains closed form expressions for the equivalent circuits which are used to model these discontinuities. Then it would be easy to handle and to characterize complicated structures like T and Y junctions, truncated junctions, arbitrarily shaped junctions, cascading junctions and more generally planar multiport junctions. Another advantage of this method is that the edge line concept for arbitrary shape junctions operates with real parameters circuits. The validity of the method was further confirmed by comparing our results for various discontinuities (bend, filters) with those from HFSS as well as from other published sources.

Determination of the complex acoustic scattering matrix of a right-angled duct

A method for determining the complete higher-order scattering matrix of an acoustic discontinuity is developed. The method is demonstrated for a right-angled waveguide bend, and the magnitude and phase of the reflection and transmission coefficients are extracted precisely. The procedure is straightforward and based on the solutions to the Helmholtz equation by the finite element method (FEM). The consistency of the scattering coefficients found by this method is verified by their properties of symmetry, and their accuracy is established by the conservation of energy. The reliability of the new technique is further proved by means of an arbitrary sound source and by comparing the direct FEM response to the reflection matrix calculation. Some features of the scattering matrix as a function of frequency are surprising, such as the steps and reversion of the phase evolution or the complete loss of transmission of the incoming wave. The methodology detailed in this paper can be extended to other multiport junctions, such as T-junctions or size discontinuities in ducts.

ANALYSIS AND DESIGN OF MULTIPORT WAVEGUIDE JUNCTIONS WITH ARTIFICIAL INCLUSIONS FORMED OF CONDUCTING STRIPS

A rigorous electromagnetic theory is developed to analyze multiport waveguide junctions with artificial inclusions formed of the conducting strips and dielectric layers. The method is based on the Fourier transform technique combined with the mode matching method technique that takes into account the edge conditions in vicinity of the strip edges. The scattering characteristics of a 3-port junction are discussed with the numerical examples for the SWR maps, the power reflection and transmission coefficients, and the 2D plots of near fields distributions inside the junction area. A strategy of optimize matching properties of the 3-port waveguide junctions is also presented.

Direct computation of the admittance parameters of a cubic junction with arbitrarily shaped access ports using the BI–RME method

The admittance matrix representation of a six-port cubic junction with arbitrarily shaped access ports is investigated. An alternative technique, based on the theory of cavities and the boundary integral–resonant mode expansion (BI–RME) method, is proposed for the direct computation of the admittance parameters of this general waveguide multiport junction. The application of this procedure completely avoids the physical segmentation of the junction, thus always providing stable numerical results. Furthermore, the numerical efficiency of this direct technique has been increased by closing analytically some of the infinite series present in the formulation. To show the advantages of this analysis technique, first the efficient connection of an H- and an E-plane T-junction through a common side port with rounded corners has been considered. A magic-T junction with rounded corners in the two side arms has also been studied. Prototypes of these two novel devices have been manufactured and measured for verification purposes.

Multiport analysis of arbitrary circular-rod insets in rectangular waveguide by the generalized admittance matrix

An original generalized-admittance-matrix (GAM) approach for the analysis of multiport junctions in rectangular waveguide having an arbitrary circular-rod inset is presented in this paper. The method is based on an efficient computation of the GAM for the blocks that compose the structure. The efficiency is due to the fact that, for each block, the full three-dimensional GAM is obtained by solving a set of uncoupled two-dimensional problems. The accuracy and efficiency of the method developed have been assessed by comparing the results obtained with some measured data and with data obtained by the finite-element method.

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

Dans cet article on propose une technique de segmentation basee sur des representations matricielles hybrides (impedance et admitance) pour ľanalyse efficace et exacte de jonctions multi-port de guides ľondes rectangulaires aux ports de forme arbitraire. La technique est expliqee en detail et ľon en deduit une nouvelle methode pour resoudre la connection de matrices hybrides sans inversions intermediaires. Pour valider la theorie, on compare les resultats obtenus avec une jonction T-magique et avec une jonction a six ports avec des donnees experimentales de la litterature. La nouvelle methode proposee est aussi employee avec succes pour resoudre des jonctions T des plans E et H ayant des coins arrondis dans les bras lateraux.

Efficient analysis of cubic junction of rectangular waveguides using admittance-matrix representation

In the paper an efficient and accurate method, based on the multimode-admittance-matrix representation and the theory of cavities, is proposed for the analysis of a six-port ‘cubic’ junction composed of the orthogonal intersection of three rectangular waveguides. Very simple closed-form analytical expressions are explicitly detailed for all matrix elements of this basic key building block. More general waveguide multiport junctions, composed of a central cubic junction with arbitrarily shaped waveguide access ports, are also studied using a segmentation procedure. To validate the theory, numerical results are first discussed for a standard rectangular waveguide six-port cross junction. Finally, the analysis method proposed is also successfully applied to H- and E-plane T-junctions whose side arms are waveguides with rounded corners.

Rigorous Analysis of E-/H-Plane Junctions in Rectangular Waveguides Using Fourier Transform Technique - Abstract *

A rigorous and efficient method for characterizing E-/H-plane multiport junctions in rectangular waveguides is presented by using the mode-matching method combined with Fourier transform technique. The method is based on a field-theoretical full-wave approach. The electric and magnetic fields of a main waveguide in the junction are expressed in terms of Fourier integrals and matched in the Fourier transformed domain to the aperture fields expanded by the normal modes in each of arm waveguides. This yields a set of linear equations in analytically closed form to calculate the scattering parameters of the multiport systems. The numerical examples for a Magic-T junction and an asymmetric E-/H-plane three-port junction verify the accuracy and usefulness of the present method.

GENERALIZED MODAL SCATTERING MATRIX OF DISCONTINUITY-DISTORTED WAVEGUIDE MULTIPORT JUNCTIONS

A generalized modal scattering matrix formulation is presented for the calculation of discontinuity-distorted waveguide multiport junctions. Unlike common approaches based on three-plane mode-matching techniques, and modifications thereof, which calculate only the fundamental-mode scattering matrix, this algorithm computes the generalized modal scattering matrix of the junction. Therefore, the method allows the computation of components in which other structures are connected as closely as possible to the discontinuity-distorted junction as follows directly from the rigorous incorporation of all higher-order mode interactions. The method is demonstrated at three selected examples: the waveguide corner, the T-junction power divider and the orthomode transducer. Comparison with results obtained by other numerical techniques or measurements available from the literature are found to be in good agreement. © 1997 John Wiley & Sons, Ltd.

Analysis of microstrip discontinuities using the method of integral equations for overlapping regions

The method of integral equations for overlapping regions (MIEOR) in conjunction with a planar dispersive waveguide model is proposed for the investigation of microstrip discontinuity problems. A general formulation for a microstrip multiport junction and the numerical solution for the scattering matrix of T- and right-angled bend junctions with and without matching stubs are presented. The proposed technique directly leads to Fredholm's integral equation of the second kind or a coupled set of integral equations for the electric field components defined in overlapping subregions of the planar dispersive waveguide model. The Galerkin's method is employed to find the unknown coefficients in the electric field series expansion which represent the S-parameters of the junctions. The mathematical substantiation of the algorithm is provided. Numerical results are presented for T- and right-angled microstrip junctions showing good agreement with results already published.

Errata to “analysis of microstrip multiport junctions using the multimode boundary integral method”

Errata to “analysis of microstrip multiport junctions using the multimode boundary integral method”

Analysis of multiport discontinuities in waveguide using a pulsed FDTD approach

A pulsed finite-difference time-domain (FDTD) approach for computing the scattering parameters of multiport waveguide discontinuities and junctions is presented. Wideband absorbing boundary conditions (ABC's) necessary for implementation of the technique are derived. Applications of the technique are presented, and computed results are compared to measurements for several examples. >

Analysis of microstrip multiport junctions using the multimode boundary integral method

AbstractThe Boundary integral method (BIM) is applied to a number of planar microstrip multiport junctions. The E fields for coupling ports are expressed as multimode series, enabling direct calculation of S parameters from the resulting matrix equation. Results obtained for cross junctions, T junctions, Y junctions, and 90° bends agree very well with those obtained from full‐wave analysis and other methods. © 1994 John Wiley & Sons, Inc.