Joseph Helszajn

Planar Triangular Resonators with Magnetic Walls

This paper gives the field patterns in triangular planar resonators having no variation of the fields along the substrate thickness. The TM fields in such resonators with magnetic boundary conditions are obtained by duality from the TE modes with electric boundaries. The theoretical description includes the cutoff numbers of the first few modes. The radiation Q factor of fundamental microstrip resonators of this type was found experimentally to be higher than that associated with conventional disk resonators. The performance of a microstrip circulator using a triangular resonator is also described.

Design Data for Radial-Waveguide Circulators Using Partial-Height Ferrite Resonators

This paper derives the eigennetworks of radial-waveguide circulators using partial-height ferrite resonators with n=2 Chebyshev characteristics. To obtain a Chebyshev response with such junctions it is necessary to establish the proper phase angles and admittance levels of the three eigennetworks of the device. This paper derives the phase angles for the eigennetworks but relies on experiments to establish the admittance levels. The configurations dealt with include the standard circulators using either half-wave-long ferrite resonators open circuited (OC) at both ends or coupled quarter-wave-long ferrite resonators OC at one end and short circuited (SQ) at the other. It also includes the design of a new single quarter-wave-long version, which is likely to replace the two more conventional arrangements in common usage. It is observed that the eigennetworks of any one of the geometries is sufficient to characterize the other two.

Cutoff space of cloverleaf resonators with electric and magnetic walls

A planar resonator that has the symmetry of a junction circulator is the cloverleaf resonator. The isotropic cutoff space of this class of resonator is described using the finite-element approach. Circuits with threefold and fourfold symmetries and with a magnetic or an electric sidewall are separately dealt with. Standing-wave solutions are included for completeness. The gyromagnetic problem is separately investigated. >

Finite element solution of longitudinally magnetized elliptical gyromagnetic waveguides

The classic method used to derive a functional is to construct a quadratic form by premultiplying the wave equation by the conjugate field and then integrating this quantity over the cross section of the problem region. This procedure is utilized to construct a solution of the longitudinally magnetized gyromagnetic problem using the z-directed coupled wave equations. It is used in conjunction with the finite-element method to evaluate the propagation constants of an elliptical gyromagnetic waveguide with either an electric or a magnetic wall. The well-known functionals associated with the four possible planar circuits made up of electric and magnetic side, and top and bottom walls, are obtained directly from those of the related waveguide problems. >

Normal mode nomenclature of quadrupole gyromagnetic waveguides

The normal mode nomenclature of quadruple gyromagnetic waveguides is reviewed. A perturbation and anisotropic formulation of the normal modes of this type of waveguide is given which is in keeping with previously published work. A closed-form formulation of the problem is described. The field distributions in this type of waveguide are shown to display a classic edge mode effect. >

First-Order Nonlinear Theory in Hexagonal Ferrites with Planar Anisotropy under Perpendicular Pumping

The first-order spinwave instability under perpendicular pumping at large signal power in an hexagonal ferrite ellipsoid with planar anisotropy biased in the easy plane is studied. The nonlinear coupling coefficient is obtained in terms of the physical variables of the unstable spinwaves and the uniform mode magnetization such as the orientation and ellipticity of the unstable spinwaves, the coordinates of the spinwave propagation vector k, and the uniform mode ellipticity. Results obtained using a computer in the case of a sphere are included. Also included are experimental results on the coincidence region with the dc field in the easy plane and with the dc field out of the easy plane. This latter arrangement leads to a new tunable coincidence limiter.

Verification of first circulation conditions of turnstile waveguide circulators using a finite-element solver

One means of adjusting the first circulation condition of any waveguide circulator is to have recourse to a finite-element (FE) solver. The purpose of this paper is to do so for each of the three possible geometries of the turnstile waveguide circulator. A complete statement of the first circulation condition also requires one of the susceptance slope parameter of the junction. This quantity is separately evaluated. The resonators under consideration are the side and apex coupled half-wave-long prism structures open circuited at each flat face and the conventional cylindrical geometry. The classic E-plane turnstile circulator using a prism resonator is also dealt with. The agreement between the existing literature and the FE adjustment is excellent.

A nonreciprocal tunable waveguide directional filter using a turnstile open gyromagnetic resonator

The 4-port waveguide directional filter is a classic network in microwave engineering. The purpose of this paper is to describe one gyromagnetic version using an open gyromagnetic resonator in a dielectric-filled cavity. A property of the circuit is that it behaves as a 4-port circulator with one direction of circulation at one split frequency of the resonator and with the other direction for the other split frequency. An insertion loss between the coupled ports below 1.50 dB and an attenuation or isolation of typically 15 dB between the decoupled ports over most of the tuning range of the filter have been achieved. Its 3-dB bandwidth is typically 65 MHz. A typical tuning range of more than 1 GHz centered at about 10.5 GHz has been separately realized for each split branch. >

Reflection angles of in-phase and split counter-rotating eigenvalues of the three-port circulator

The reflection angle of the in-phase eigenvalue and that of the reflection coefficient at port 1 of a terminated circulator are equal at a unique frequency at which the gyrotropy produces a return loss of 9.5 dB. The frequency response of the terminated circulator, beyond that value of gyrotropy, displays four such frequencies. The angles of the reflection coefficients at the inner two frequencies also coincide with the in-phase reflection angle. The two outside frequencies at which the return loss at port 1 are 9.5 dB coincide with the counter-rotating reflection angles. Below this value of gyrotropy, the angles of the reflection coefficient are equal to those of the split counter-rotating eigenvalues under these same conditions. A knowledge of the three reflection angles is both necessary and sufficient for the characterization of this class of circuit at both its midband and split frequencies.

Synthesis of wide-band planar circulators using narrow coupling angles and undersized disk resonators

Circulators using radial/lumped-element resonators with narrow coupling angles that result in gyrator circuits that are as good as, if not better than, those obtained with the classic approach are presented. The form of the lumped element variable is not unique and can be realized by making use of the fringing capacitance at the interface between a dielectric resonator and a substrate with a higher relative dielectric constant than that of the resonator. The topology requires the adjustment of electromagnetic, electrostatic, and network conditions with common parameters, so that a solution that relies on fringing effects only is not generally ensured. The synthesis of octave-band circulators using two quarter-wave-long impedance transformers is reported. A 1-2-GHz circulator based on one such solution with an insertion loss of no more than 0.35 dB between any two ports and typical return loss of 20 dB is described. >