J. Helszajn

Bio: J. Helszajn is an academic researcher. The author has contributed to research in topics: Susceptance & Circulator. The author has an hindex of 1, co-authored 1 publications receiving 28 citations.

Resonant Frequencies, Q-Factor, and Susceptance Slope Parameter of Waveguide Circulators Using Weakly Magnetized Open Resonators

Abstract: A useful quantity in the description of junction circulators is the difference between the split frequencies of the magnetized ferrite resonator. A knowledge of this quantity allows the loaded Q-factor of a junction using a weakly magnetized resonator to be determined. This paper derives an exact description of the former quantity in the case of the open quarter-wave long (partial-height) disk resonator used in the construction of commercial turnstile waveguide circulators. This is done by employing duality between a ferrite-filled circular waveguide having ideal electric wall boundary conditions and one having ideal magnetic wall boundaries. The effect of an image wall on the open flat face of the open resonator is considered separately. The paper includes some remarks about the susceptance slope parameters of disk and triangular open resonators.

Substrate-Integrated-Waveguide Circulators Suitable for Millimeter-Wave Integration

Abstract: Over the years, many millimeter-wave circulator techniques have been presented, such as nonradiative dielectric and fin-line circulators. Although excellent results have been demonstrated in the literature, their proliferation in commercial devices has been hindered by complex assembly cost. This paper presents a study of substrate-integrated millimeter-wave degree-2 circulators. Although the substrate integrated-circuits technique may be applied to virtually any planar transmission medium, the one adopted in this paper is the substrate integrated waveguide (SIW). Two design configurations are possible: a planar one that is suitable for thin substrate materials and a turnstile one for thicker substrate materials. The turnstile circulator is ideal for systems where the conductor losses associated with the thin SIW cannot be tolerated. The design methodology adopted in this paper is to characterize the complex gyrator circuit as a preamble to design. This is done via a commercial finite-element package

Analysis and development of millimeter-wave waveguide-junction circulator with a ferrite sphere

Abstract: This paper presents a class of new easy-to-fabricate ferrite-sphere-based waveguide Y-junction circulators for potentially low-cost millimeter-wave applications. A new three-dimensional modeling strategy using a self-inconsistent mixed-coordinates-based modal field-matching procedure is developed to characterize electrical performance of the proposed circulator. It is found that the circulating mechanism of the ferrite-sphere post is different from its full-height ferrite counterpart in that the new structure operates in a turnstile fashion with resonant characteristics, while the conventional device operates on a transmission cavity model. Extensive comparable studies between the new and conventional circulators are made to show that the electrical behaviors of the new structure are also distinct and radial power-density profiles are not stationary, as in the case of the full-height ferrite post circulator for different geometrical parameters. Results obtained by the analysis technique are compared with the available results for a full/partial-height ferrite circulator, showing an excellent agreement. Our calculated and measured results are also presented for W-band circulators with the proposed ferrite-sphere technique, indicating some interesting characteristics such as the frequency offset behavior of the isolation and reflection curves. In addition, radial power-density profiles are plotted inside and outside the ferrite sphere to illustrate its intrinsic circulating mechanism, as well as its difference, as compared to its full-height ferrite structure.

An efficient method to analyze the H-plane waveguide junction circulator with a ferrite sphere

Abstract: This paper presents an approximate, but efficient field treatment of the new easy-to-fabricate ferrite-sphere-based H-plane waveguide circulator for potentially low-cost millimeter-wave communication systems. A new three-dimensional modeling strategy using a self-inconsistent mixed-coordinates-based mode-matching technique is developed, i.e., the solutions of the Helmholtz wave equations in the ferrite sphere and in the surrounding areas are deduced in the form of infinite summation of spherical, cylindrical, and general Cartesian modes, respectively. The point-matching method is then used on the interface between the ferrite sphere and air within the cylindrical junction, as well as the interface between the junction and waveguides to numerically obtain the coefficients of different orders of basis functions of the field. Therefore, the field distributions, as well as the characteristics of the circulator, are numerically calculated and good agreement is observed between the numerical results and measured data.

Design of Waveguide Circulators with Chebyshev Characteristics Using Partial-Height Ferrite Resonators

Abstract: This paper outlines a step-by-step approach to the design of waveguide circulators using partial-height resonators, which incorporates every linear dimension of the device, The approach used consists of defining the physical variables of the ferrite region in terms of the frequency, VSWR, and bandwidth specification. It also incorporates the definition of the length and admittance level of the radial transformer. The model employed is essentially a two-mode one, with the third mode separately adjusted to exhibit an ideal electric-wall boundary condltion at the terminals of the junction.

Adjustment of In-Phase Mode in Circulators Using Turnstile Junctions

Abstract: The adjustment of the counter-rotating modes of waveguide circulators using weakly magnetized turnstile junctions is fairly well understood, but some uncertainty about the definition of the in-phase mode still remains. The purpose of this paper is to remedy this situation by experimentally evaluating the in-phase eigenvalue s/sub 0/ for different filling factors and radial wavenumbers of the in-phase resonator. This is done by using the unitary condition to derive four possible relationships between the in-phase and counter-rotating eigenvalues s/sub 0/ and s/sub 1/, and the scattering variable S/sub 11/, and using one or another of them to form s/sub 0/. The situation for which s/sub 0/ is in anti-phase to s/sub 1/ corresporrds to the first classic circulation condition of this class of device and is also derived.