Radiation from Ferrite-Filled Apertures

The properties of ferrites at microwave may be used in antennas to produce some interesting effects. A rectangular waveguide termininating in the plane of an infinite ground screen and radiating into a half space has a ferrite slab located at the aperture. With a TE10 mode of 9365 mc sent through the waveguide the far-zone radiation pattern in the H plane has been measured as a function of a transversely applied static magnetic field. It was discovered that for certain thicknesses of the ferrite slab the radiation lobe deviated considerably from the normal to the infinite screen with only small changes in the applied magnetic field. For some of these resonance points and their neighborhoods more detailed investigations were carried out in order to determine: a) the amplitude and phase distributions of the electric field in the aperture; b) reciprocity relationships. Small holes backed with a ferrite slab also exhibit a pattern shift with applied magnetic field. When an axial magnetic field is applied to a ferrite rod protruding from an open circular guide, the radiation pattern of the rod antenna may be shifted considerably. This effect has cylindrical symmetry.