Abstract: A planar oscillator (9, 109) having a dielectric cavity (25, 125) and which is operative at microwave frequencies, said oscillator consisting of a dielectric material base (10, 110) one surface of which has, superposed thereto, a continuous layer (11,111) of a conductive material which coats portions of said face; the remaining portions (10A, 10B, 110A', 110A", 110B) of the surface have, superposed thereto, strips of a conductive material (12,13,14,112,113,114) which are separate from each other and are electrically connected to an active element (19, 119), a dielectric cavity (25,125) adhering to the opposite surface of the dielectric material base (10,110), the layer of conductive material (11,111) providing a grounding plane and the strips of conductive material (12,13,14,112,113,114) providing transmission and output lines for the oscillator.

Abstract: A device capable of measuring the position of the level surface of a molten metal bath by exploiting a microwave signal emerging from a waveguide which impinges perpendicularly onto the molten metal so as to originate a standing wave, the position of which is determined by the position of the level surface. The parameters of the standing wave are detected so as to obtain an indication as to the level.

Abstract: The transmission structure comprises at least two parallel conducting bands placed on an support of semi-insulating semiconductor material. Said conducting bands are electrically interconnected by concentrated capacities, which are spaced apart at predetermined distances, which are less than the wavelength of the signal to be transmitted.

Abstract: The oscillator comprises a main cavity housing a Gunn diode and auxiliary cavity branching laterally and allowing only inlet of the harmonic components.The auxiliary cavity is provided with harmonic tuning means for varying the reactance of the auxiliary cavity to the harmonic components. The load impedance seen by the Gunn diode is thus varied.

Abstract: This invention relates to a new type of instrument for measuring the moisture in materials, particularly in earth and sand. According to the invention, the instrument comprises a constant amplitude microwave signal generator, a waveguide container for a sample of moist material, a microwave signal amplitude detector and a directional coupler of high directivity disposed between said generator, said container and said detector.By means of said directional coupler the constant amplitude microwave signals are transmitted to the sample, which reflects to same, and reflected signals are transmitted to the detector.