Marat Davidovitz

Reconstruction of the S-matrix for a 3-port using measurements at only two ports

A complete S-parameter characterization of a 3-port device is extracted from vector network analyzer measurements made on only two of its ports. The third port is terminated with three known standards, appropriate to the associated transmission medium. Unique extraction of the 3-port matrix from the measured data sets is shown to be possible. This method is particularly useful for devices having incompatible ports, some of which cannot be directly connected to the analyzer. >

Wide-band waveguide-to-microstrip transition and power divider

A waveguide-to-microstrip transition is proposed, modeled, and validated through a prototypical design. The transition is shown to possess characteristics required in many high-frequency systems, namely wide-band response, ease of construction and hermetic isolation of the two transmission media. Implementation in a waveguide-to microstrip power divider (three-port) form is detailed here, but other feasible variants are mentioned. Favorable agreement between the proposed model and measured results is observed.

A compact planar magic-T junction with aperture-coupled difference port

The operating principles of a compact planar magic-T junction are described and experimentally validated. The distinguishing feature of this component is the placement of the difference port on a layer separated from the other three ports by a ground plane. Moreover, the two parts of the component are electromagnetically coupled through a slot-aperture in the ground plane. The component is inherently multilayer, i.e., the transition between the circuit layers is a functional part of the device. The tested microstrip prototype performs well over a frequency range of about 40%.

A non-contact interconnection through an electrically thick ground plate common to two microstrip lines

Coupling between two microstrip lines through a rectangular slot in a common, electrically thick ground plate is analyzed. The results are applied to examine the properties of a vertical, noncontact line-to-line transition. An efficient and accurate design model is constructed. The model allows insight into the coupling characteristics of the device with minimal computational effort. Measured results are used to verify the efficacy of the solution. Analytical or highly convergent forms of the model parameters are derived whenever possible. >

Cutoff Wavenumbers and Modes for Annular-Cross-Section Waveguide with Eccentric Inner Conductor of Small Radius

Analytical expressions are derived for the cutoff wavenumbers and the corresponding modes in annnlar-cross-section waveguides having inner conductors of small radius. Waveguides with circular and rectangular outer boundary are considered. In tbe case of the circular eccentric annular waveguide, comparison is made between the values of cutoff wavenumbers computed from the expressions derived in this paper and data obtained by a more rigorous numerical technique.

Extension of the E-plane scanning range in large microstrip arrays by substrate modification

The effect of the substrate structure modification on the E-plane scanning performance in large microstrip arrays is studied with the aid of a two-dimensional model. The goal is to alleviate scan blindness effects. The finite-element method of lines is used to solve the electromagnetic equations, thus demonstrating its applicability to open, periodic structures.<<ETX>>

A low-loss thermal isolator for waveguides and coaxial transmission lines

A low-loss element insertable into microwave coaxial transmission lines and waveguides is designed to provide a thermal isolation barrier at the point of insertion.

Twenty-GHz broadband microstrip array with electromagnetically coupled high T/sub c/ superconducting feed network

The use of high-temperature superconducting (HTS) feed lines and phase shifters can substantially improve the performance of microwave and millimeter-wave printed phased array antennas. A novel antenna architecture is described that provides a broadband radiating aperture to be used as a scanning array with compatible low-loss HTS phase shifters. The approach follows an earlier design demonstrated at 12 GHz, and this work extends the approach to 20 GHz. The antenna design, radiation patterns, bandwidth measurements, and thermal analysis are reported. A prototype thermal isolator design is described that reduces the heat load of coaxial interconnections between cryocooled and room temperature systems.

Calculation of multiconductor microstrip line capacitances using the semidiscrete finite element method

In this analysis partial finite-element discretization of the Poisson equation is implemented. The governing partial differential equation is thus reduced to a coupled set of ordinary differential equations, which is solved analytically. Formulation of the solution with this technique is more general and versatile than with the method of lines. The method of lines is derived as a special case of the semidiscrete finite-element method.<<ETX>>

An approach to analysis of waveguide arrays with shaped dielectric inserts and protrusions

The classical moment method solution of the waveguide-array problem is extended to allow for generally shaped dielectric matching inserts in the waveguide-to-free-space transition region. The aperture electric field is represented in terms of waveguide modes. To account for the presence of the matching inserts, the aperture fields are numerically propagated through the dielectric regions. Novel matching configurations, which extend the scanning range of waveguide elements or can be used to shape the element pattern in limited-scan applications, are proposed and analyzed.