Abstract: A method of identifying and tracking a target is described, in which seismic data relating to a target is passively detected and processed using statistical means. The statistical manipulation of the data includes frequency information extraction, dynamical mixture model construction based on existing known data and identification of an unknown target by the convergence of this model to a state characteristic of that target.

Abstract: A method of identifying and tracking a target is described, in which seismic data relating to a target is passively detected and processed using statistical means. The statistical manipulation of the data includes frequency information extraction, dynamical mixture model construction based on existing known data and identification of an unknown target by the convergence of this model to a state characteristic of that target.

Abstract: In a method of forming a micron-size field emitter, an array of conductive tips is formed on a substrate. A layer of dielectric material is formed on the substrate to a thickness substantially equal to the height of the tips, but forming a protuberance over each tip. A conductive grid layer is deposited over the dielectric layer, forming corresponding protuberances, followed by a layer of resist material which is of sufficiently low viscosity so that it flows off the grid layer at the protuberances leaving the protuberances substantially unprotected. The grid and dielectric layers in the protuberances are then etched away to reveal the tips through the resulting apertures in the grid and dielectric layers. The apertures are thereby automatically aligned with the tips without the need for lithographic processes.

Abstract: In the production of micron-size pyramid emitters for field emission devices, a first layer of electrically-conductive material, such as single crystal silicon or metal, is etched to form column-like structures each of which tapers from each end of the column towards an intermediate portion along its length. A second conductive layer is formed in contact with the free ends of the columns, and etching of the columns is then resumed until the intermediate portion of each column is etched through, leaving a pair of pyramid emitters pointing towards one another and supported by the respective conductive layer.

Abstract: A klystron device comprises an array of cold-cathode field emission elements arranged to form a distributed amplifier which further comprises a modulation strip line and a catcher strip line. A collector electrode is spaced from the catcher strip line. The device may include a deflector for returning electrons emitted by the elements back to the modulation strip line so that the device acts as an oscillator.

Abstract: In a method of forming a field-induced emission device, a cathode is provided on a substrate, for example by etching away the substrate to leave a pointed projection. The projection may be covered with a metallic layer to enhance the field-induced cathode emission. A first insulating layer is formed over the substrate, with an aperture therein corresponding to the cathode position. An apertured control grid layer is formed over the first insulating layer and an apertured second insulating layer is formed thereon. A tunnel formed by the apertures in the insulating and conductive layers is filled with a plug of soluble material. An anode strip is formed on the second insulating layer and over the plug, and the plug is then dissolved through gaps at the edges of the anode strip, thereby leaving an unsupported area of anode strip over the cathode. The tunnel may then be evacuated or may be filled with gas and the gaps at the edges of the anode strip will then be sealed to retain the vacuum or gas.

Abstract: A vacuum valve device comprises a substrate on which is formed an updoped silicon layer from which a silicon dioxide layer is grown. First, second and third electrode structures are formed on the silicon dioxide layer by depositing a metallic layer and etching away unwanted portions of the layer. The first electrode structure has a pointed end and/or a sharp edge and/or is formed of low work function material so that, when a suitable voltage is applied between the first and third electrode structures, electrons are emitted from the first electrode structure due to a field emission process. Electrons therefore flow from the first to the third electrode structure substantially parallel to the substrate. The second electrode structure acts as a control electrode.