| EPSRC Reference: |
GR/H82853/01 |
| Title: |
NOVEL STRUCTURES FOR THE DEVELOPMENT OF NONRECIPROCAL PLANAR DEVICES |
| Principal Investigator: |
Davis, Professor L |
| Other Investigators: |
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| Department: |
Electrical Engineering & Electronics |
| Organisation: |
UMIST |
| Scheme: |
Standard Research (Pre-FEC) |
| Starts: |
27 April 1993 |
Ends: |
31 March 1995 |
Value (£): |
87,007
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| EPSRC Research Topic Classifications: |
| RF & Microwave Technology |
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Summary on Grant Application Form |
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1) To establish a theoretical foundation for new types of nonreciprocal components, based on coupled lines, that may reduce the need for precision machining techniques and be compatible with planar technology.2) To develop models for ferrite-coupled microstrips and slotlines magnetised in an arbitrary direction, and to use such models to assist the development of design guidelines.Progress:Investigations have recently been reported of coupled planar waveguides with ferrite loading which is magnetised either parallel with or perpendicular to the direction of propagation. Depending on the arrangement of the structure and the direction of magnetisation, the waveguide system may be reciprocal (+=-) or nonreciprocal (+-), where is the phase coefficient in the z-direction. The principles of such systems have been described in terms of coupled-mode theory, but no work has been reported on the effect on propagation of structural parameters such as material properties, dimensions, magnitude and direction of the static magnetic bias field, and signal frequency. These are the factors which will lead eventually to design guidelines. The Finite-Element Method (FEM) with edge elements has been adopted in this work. A model in which the static magnetic field (assumed uniform in the sample) can be arbitrarily orientated has been developed to enable any of the three principle directions of magnetisation (with respect to the direction of propagation) to be investigated using the same computer program. An expression for the tensor permeability of a ferrite with an arbitrary direction of magnetisation has been developed. The frequency dependence is included as usual, and the medium is assumed lossless. Using this tensor, and edge elements, FEM formulae for both E and H fields have been developed for the first time. To follow a practical and intuitive approach to the solution of the eigenvalue equation we have adapted an iterative procedure which has been successfully used previously in FEM solutions for nonlinear optical waveguides. When the static magnetic field is arbitrarily directed a quadratic eigenvalue equation is obtained which contains both and 2. Instead of reducing the quadratic equation to a linear one (with a matrix order twice that of the original), an iteration method has been used again. The iteration is not stopped until the difference in two consecutive solutions is less than a given tolerance. To test the numerical analysis, it has been applied initially to a classical structure consisting of a rectangular waveguide loaded with an asymmetric full-height ferrite slab. With the (transverse) magnetisation parallel to the narrow waveguide dimension exact analytical solutions for + and - are available against which the numerical solutions have been compared. Excellent agreement has been obtained. Results have also been computed for as a function of angle in the x-z plane, and as a function of angle in the y-z plane. To describe the new theoretical approach in more detail a paper is being prepared for publication. Work on the planar structures described above is in hand.
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Potential use in non-academic contexts |
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Impacts |
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| Description |
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Sectors submitted by the Researcher |
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