Nonreciprocal Components Research Articles

Utilisation of surface magnetoplasmons in the millimetre wavelength range

Sophisticated communication and radar systems in the submillimetre wavelength bands will only be realised when the designers have access to the same diversity of devices available at lower frequencies such as circulators, differential phase shifters and nonreciprocal isolators. Below 100 GHz these devices depend on high quality ferrites. However, despite considerable investment in research and development, ferrites materials have not been realised that will yield acceptable performance at higher frequencies. This prompted the author to start investigating the possibility of using surface magnetoplasmons on high quality lightly doped semiconducting substrates as the vehicle for the design of nonreciprocal components in the submillimetre regime. This paper chronicles investigations pursued during the period 1976–1986, principally by faculty and students at Brown University and Lehigh University, into the behaviour of surface magnetoplasmons in a variety of canonical structures germane to nonreciprocal devices in the millimetre and submillimetre wavelength ranges. Interest focused on performance characteristics for such devices as differential phase shifters and nonreciprocal isolators. Critical to obtaining acceptable performance parameters such as insertion loss are, of course, the loss characteristics of the semiconducting materials. The latest results, based on studies of our canonical device models and presuming the use of the best available materials, indicate that acceptable device performance should be attainable. Results are presented that show insertion loss as well as isolation ratio for representative nonreciprocal isolator structures and the attained differential phase shift per unit insertion loss for a canonical differential phase shift configuration.

Nonreciprocal propagation characteristics of transversely magnetised metal–insulator–semiconductor coplanar waveguides

The propagation characteristics of a transversely magnetised MIS coplanar waveguide are studied. It is shown how the low-loss and slow-wave effects are efficiently combined with a relevant nonreciprocal propagation phenomenon. This fact could be used for the design of nonreciprocal components suitable for integration.

Nonreciprocal devices using ferrite ring resonators

Novel nonreciprocal components based on hollow ferrite discs, i.e. ferrite ring resonators, are discussed. Some three-port and four-port components are analysed, and some design guidelines are presented. It is shown that a ring structure requires a smaller diameter and ferrite thickness than a disc structure for the same frequency. A ring also provides another variable in design and permits ports to be connected to the inside as well as the outside. Novel components and increased component density may therefore be possible at the expense of bandwidth.

A unipolar transistor with negative output resistance

In this work a three-terminal active solid state device, that operates well into submillimeter-wave frequencies is proposed. The activity of this device is due to negative output resistance. The origin of the negative output resistance is shown to be injection and transit-time delays that any finite sized device possesses. Generating proper injection delays utilizing specially designed tunneling junctions and combining these injection delays with transit-time delays a novel hot electron transit time transistor (HETT) is introduced and its small signal analysis is carried out. Having three terminals in an active device provides isolation between input and output and completely integrated monolithic negative resistance amplifiers can be fabricated, without the need for non-reciprocal circuit components, like circulators. It is shown that negative output resistance should also be observed in transistors due to inherent intrinsic delays.

Field effect transistor circulators

Field-effect-transistor circulators that are compatible with monolithic microwave integrated circuit technology are described. These passive nonreciprocal components are formed with inductors, capacitors, transmission line sections, and microwave transistors, and all can be integrated on a single IC chip the size of a pinhead. The operating principle, power-handling capability, and noise performance of these components are discussed for both narrowband and wideband applications, and examples of their practical implementation are given. The transistor-based 2-, 3-, and 4-port passive nonreciprocal components described offer an alternative to ferrite miniature circulators with potential advantages of small size and lower cost in production volume.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Microwave/mm wave magnetics and MMIC compatibility (invited) (abstract)

Ferrite devices can be loosely classified into three different categories, namely: control components using polycrystalline ferrites, tunable filters and oscillators using YIG spheres, and devices based on epitaxial YIG or ferrite films. Ferrite control components such as circulators, isolators, and switches are used in almost all microwave and millimeter wave systems. Tunable YIG sphere devices see more limited use in radar and EW systems, and microwave test equipment while epitaxial YIG devices have yet to make a significant systems impact. GaAs chips for phased array modules are under development by several companies for both radar and EW applications. The GaAs chips can contain small signal and power gain, phase shifters, filters, mixers, and switches. The modules are usually designed, however, with discrete circulators or isolators which are often significantly larger than the MMIC chips. Further reduction in module size and cost will require the design of the module without nonreciprocal components, or the development of ferrite devices which are more compatible with the size, bandwidth, and fabrication of the GaAs device. Integration of nonreciprocal ferrite components on the GaAs chip could have a large impact but presents a significant challenge both in terms of processing compatibility between the ferrite and the GaAs and in terms of cost. The impact in the areas of tunable YIG filters and oscillators and MSW devices are smaller but, fortunately, so are the difficulties. Here the YIG films or spheres, or hexagonal ferrite films can be laid on the GaAs substrate thus forming a hybrid device. Having integrated the ferrite with the GaAs it is necessary to consider the magnetic bias field requirement. Bias fields are not required in latching devices and can be minimized in other devices by use of hexagonal ferrite films with their large anisotropy fields. It may even be possible to integrate a permanent magnet film onto the GaAs chip.

Millimetric Nonreciprocal Coupled-Slot Finline Components (Comments)

A statement is made concerning the feasibility of nonreciprocal components with ferrites magnetized in the direction of propagation.

Phase matching in symmetrical single-mode magneto-optic waveguides by application of stress

Tuning of the propagation constant difference Δβ=βTM−βTE in single-mode symmetrical yttrium iron garnet (YIG) film waveguides over a range of 250°/cm by means of external stress is demonstrated. An a posteriori, precise setting of phase match Δβ→0, which is a precondition for nonreciprocal mode coupling type components, can be achieved by this method.

Thick-Film Ferrimagnetic Pastes Using Lithium Ferrite

The preparation of a thick-film ferrimagnetic paste using lithium ferrite powders and its physical, electrical, and magnetic properties are described. A resonance technique for the measurement of the dielectric constant, saturation magnetization, loss tangents, and resonance linewidth of the ferrite films at microwave frequencies is presented. Applicability of the ferrite pastes developed for the fabrication of nonreciprocal microwave components such as isolators and circulators is described.

Fabrication of nonreciprocal microwave components using thick film ferrimagnetic pastes: Chinmay K. Maiti, D. Bhattacharyya and N. B. Chakrabarti Electrocomponent Sci. Technol.8, 111 (1981)

Fabrication of nonreciprocal microwave components using thick film ferrimagnetic pastes: Chinmay K. Maiti, D. Bhattacharyya and N. B. Chakrabarti Electrocomponent Sci. Technol.8, 111 (1981)

A Noise Temperature Measurement System for Mismatched Noise Sources

A measurement system is described which allows us to determine the noise temperature of mismatched noise sources with unknown reflection coefficients. The system consists of a null-balancing radiometer extended by a circuit to compensate for the reduced noise power emitted by the mismatched one-port. In this circuit, no passive nonreciprocal components are necessary. Special consideration is given to measurement errors that are caused by the correlation of the input and output noise waves of the radiometer preamplifiers. Several methods to eliminate these errors are described. Furthermore, a circuit is given by which the measurement range is extended down to 0 K without the use of cold reference noise sources. Finally, a practical setup, operating in the 20-40-MHz range, is described together with corresponding measurement results.

Combined reciprocal and non-reciprocal birefringence in optical monomode fibres

We analyse the overall birefringence which arises from the combined effects of Faraday rotation (non-reciprocal) and bending stress (reciprocal) applied to a monomode optical fibre loop. The theory is substantiated by numerical evaluations and appropriate experimental data are reported. These indicate how it is possible to build non-reciprocal birefringent components, i.e. rotators and isolators, by means of monomode coils.

Frequency-selective combline directional couplers designed as novel filters and multiplexers

Combline directional couplers may be designed to have useful frequency-dependent transfer characteristics. The normal modes are optimised by a numerical technique to show that novel nonreflective filters and band-branching multiplexers may be achieved without the use of nonreciprocal components such as isolators and circulators.

Development of Yttrium Iron Garnet Paste and Fabrication of Non-Reciprocal Microwave Components

Development of Yttrium Iron Garnet (YIG) paste from pre-sintered green powders of YIG and the feasibility of fabricating microwave components using these pastes have been discussed. Transmission loss of a 50-ohm microstripline on YIG films was studied with different externally applied magnetic fields. Non-reciprocal field displacement isolator was fabricated on the YIG films and insertion loss, isolation and VSWR were measured. The results indicate that the devices made using YIG paste give better performance than those with ferrite pastes.

Experimental study of magnetodynamic edge-guided waves on a microwave ferrite substrate

This paper describes a microwave experimental study of the phase coefficient of magnetodynamic waves guided along a circular convex edge of a conducting film on a perpendicularly-magnetised ferrimagnetic substrate. The experiment consists of measuring the microwave resonance frequencies of a 10 mm radius gold disc on a O.5mm thick polycrystalline YIG plate, and identifying the azimuthal mode numbers 'n'. The measured dispersion curves for the edge-guided waves are compared with the theoretical results of de Santis. The measured phase velocities are found to be significantly greater than the theoretical values. The discrepancy may be caused by the theoretical assumption of a perfect magnetic wall at the disc edge. The experimental study is relevant to the design of miniature edge-wave nonreciprocal components that are being realised with instantaneous bandwidths much greater than an octave, e.g., 5-15 GHz.

A New Class of Nonreciprocal Components Using Slot Line (Short Papers)

The authors present an experimental and theoretical study of edge modes in a ferrite-loaded slot line. Nonreciprocal properties are obtained over a broad frequency band. Added microstrip lines provide suitable transitions. A theory based on magnetic boundary conditions shows good agreement with the experimental results and allows a comparison with stripline devices described by Hines. In particular, the characteristics of the slot-line isolators are satisfactorily explained by this theory.

Nonreciprocal Magnetostatic Surface Waves with Independently Controllable Propagation and Decay Constants

The characteristics of inhomogeneous TE eigenwaves propagating in a transversely magnetized uniform gyromagnetic medium are presented-with special emphasis given to the magnetostatic region of the dispersion relation. It is shown that when the magnetization is not parallel to the electric field, the tensor nature of the medium constrains and thereby controls the relationship between the propagation and decay constants. In addition, the eigenwaves are nonreciprocal in the field displacement sense allowing novel magnetic control to be exercised over them. As a consequence it should be possible to vary the depth of penetration of such a wave and in fact cause propagation to switch from one to the other surface of a gyromagnetic slab provided the faces are terminated in suitable surface impedances that allow the desired eigenwave to propagate as a bound surface wave mode. Such modes may form the basis for novel filters and nonreciprocal components constructed with convenient planar geometries.

Ring-laser bias using reciprocal optical components

Ring-laser biasing, to reduce nonlinear rotation sensitivity, normally requires either nonreciprocal optical components or rotation of the whole laser. It is shown that biasing can be achieved by using the finite transit time of light propagation between two time-varying optical phase shifters.

Minimum-scattering antennas

Antennas with identical radiation patterns can differ in the manner and extent to which they modify an incident wave, i.e., in the way they scatter. This paper enlarges on the work of Dicke [1] on this subject, employing, as he does, a scattering representation based on spherical modes. However, the approach is more physical and includes antennas with nonreciprocal components and with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> (local) ports. A canonical minimum-scattering antenna is defined as one which becomes "invisible" when the accessible waveguide terminals are open-circuited. The scattering matrix of such an antenna is shown to be unique once <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> arbitrary orthogonal radiation patterns have been specified. Neither an impedance nor an admittance matrix for such an antenna exists. It is demonstrated for a large class of antennas terminated by matched receivers that the scattered power is generally greater than the absorbed power, equality being attained for minimum-scattering antennas.

New Topological Formulas for Linear Networks

A new method of topological analysis for networks containing nonreciprocal components and mutual inductance is presented. The components are required to have two, three, or four terminals and an admittance matrix. The difference between the present method and other known methods is the result of allowing tree and two-tree admittance parameters to be a function of the shape and element content of corresponding trees and two-trees. No modification of the original network is required and for node determinant and diagonal cofactor calculations, no sign is appended to tree and two-tree parameters. The method is illustrated with a transistor amplifier.