Abstract: A novel method of fabrication of periodic dielectric composites involving a flexible computer design stage, rapid growth of a second dielectric component. Laser stereolithography is used to form the polymer material layer by layer by photopolymerisation of a liquid. Certain materials constructed in this fashion exhibit a complete loss-free barrier to microwave propagation through the material for a desired band of frequencies and are commonly known as photonic band gap crystals. Such materials could provide a novel medium for all-angle wide- and narrow-band blocking filters, narrow-band transmission filters, reflective and loss-free substrates for planar antennas, and novel loss-free media for oscillator cavities and waveguides. In addition a novel crystal structure, particularly suited to the fabrication method mentioned above and consisting of concatenated polyhedrons, is revealed.

Abstract: A signal processing apparatus (200) comprises a plurality of receive antennas (216a-m) arranged to receive a composite signal containing a plurality of transmitted symbols. A joint detector-decoder (218) iteratively enumerates most probable symbols received at the receive antennas (216am) using an enumeration constraint. A processor (220) determines a bit stream corresponding to each most probable received symbol.

Abstract: Signal processing with reduced combinatorial complexity for tracking evolving phenomena such as radar tracks associated with weighted measurement parameters includes selecting a current phenomenon and obtaining a set of measurement parameters associated with it. Beginning at a start node providing a first parent node having an identity, an identity for a child node of the patent is produced from the sets of parameters, the parent identity and a parameter selected from the set and corresponding to the child. This is iterated for other parameters in the set. Child nodes of like identity for the phenomenon are treated as a single node with multiple parameter relationships associated with at lest one parent node, whereas child nodes with differing identities are represented as separate nodes. The process is iterated for other phenomena and associated sets of measurement parameters, but child nodes of a previously processed phenomenon are not treated as parent nodes of a phenomenon processed immediately following.

Abstract: A method for detecting perturbation of a physical system from a reference state associated with a reference parameter (?0) to a perturbed state associated with a perturbed parameter (?) includes firstly deriving the reference parameter (?0). A reference vector (F) is then derived which describes the system's state at the reference parameter (?0). A measurement-related vector (Z) associated with a perturbed state of the system is then subtracted from the reference vector (F) to provide an error vector (E). The error vector members are summed and normalised by division of a summation of elements of a vector (F?) representing a derivative (f(?0??)e) of a reference itself represented by the reference vector (F), the derivative (f(?0??)e) being evaluated at the reference parameter (?0). This provides a result equal to the difference (??(?0) between the perturbed parameter (?) and the reference parameter (?0).

Abstract: A hollow core multi-mode interference (MMI) device is described that comprises a multi-mode waveguide (10, 14) optically coupled to at least two fundamental mode waveguides (8, 12, 16). The device is characterised in that it comprises a means for varying the internal cross-sectional dimensions of a portion of one or more of said at least two fundamental mode waveguides. In particular, the side wall of a fundamental mode waveguide having a substantially square cross-section can be moved using micro-electro mechanical systems (MEMS). Various optical routing devices incorporating such MMI devices are described.

Abstract: A buffer structure comprising a compositionally graded layer of a nitride alloy comprising two or more Group IIIB elements, for example La, Y, Sc or Ac, is used to modify a silicon substrate to produce a universal substrate on which a range of target materials, for example GaN, may be deposited to produce semiconductor devices for electronic and optical applications. The resulting lattice parameter L varies with thickness T through the structure.

Abstract: This invention relates to a pattern recognition correlator and method for correlating input data with one or more reference data sets. The input data, which may be for instance digital amplitude modulated optical data, is used to modulate an optical signal to form a phase modulated optical signal. This temporal phase modulated optical signal is then converted into a parallel optical phase signal, preferably through use of an optical delay, and modulated by an optical phase modulator. When there is a correlation between the input data and the reference data the emerging wavefront is plane and can be strongly coupled to a detector. In the absence of correlation the emergent wavefront is not plane and so is not coupled as strongly to the detector. The detector output can therefore be used as an indication of correlation.

Abstract: An optical amplifier is described that comprises at least two sections of amplifying optical fibre and pumping means for optically pumping the amplifying optical fibre. Optical fibre support means, for example a channel or channels in a substrate, are also provided to hold the two or more sections of amplifying optical fibre substantially straight during use. The optical fibre support means also includes a means for coupling light between the at least two sections of amplifying optical fibre. The at least one amplifying optical fibre may comprise an Erbium doped core to provide an erbium doped fibre amplifier (EDFA).

Abstract: A phoretic display having a liquid crystal suspension medium and a relief structure alignment layer comprising a relief structure surface incorporating a plurality of indentations. The relief structure alignment layer is adapted to generate a preferred alignment of the liquid crystal suspension medium within the display by creating defects within the alignment of the liquid crystal director at the base of each indentation. The relief structure alignment layer provides a substantially planar liquid crystal director alignment in the vicinity of the internal surface of each indentation and a substantially homeotropic liquid crystal director alignment in the vicinity of the relief structure surface and in the bulk of the liquid crystal material.

Abstract: A Human-Computer Interface that comprises a set of sensors, actuators and computer generated controls is characterised in that the controls are projected in three spatial dimensions by a three dimensional display device and are manipulated by means of an operator interacting with them by movements of the operator's body, these movements being detected using the sensor system, where characteristics of a displayed target volume change according to the movement made, and actuators worn on the body, react according to how the body interacts with the computer generated controls.

Abstract: A buoyant platform apparatus, such as a buoy, is described that comprises a laser radar (lidar) wind speed measurement device. The lidar is arranged to make wind velocity measurements at one or more remote probe volumes of known position relative to said platform. The wind speed measurement apparatus may further comprise motion sensing means that, in use, monitor motion of the platform allowing wind speed at an absolute position in space to be measured. Wind velocity data may also be compensated for platform movement.

Abstract: A method and apparatus for reducing the effects of motion of a subject during image acquisition is presented. The method is particularly suitable for correcting the motion during magnetic resonance imaging. The method involves comparing an image with a reference image in the spatial frequency domain to determine the extent of any rotational and/or translational motion and then apply an appropriate correction. Any motion is modeled by comparison with the reference image but the corrected image is produced using information from the corrupted image alone.

Abstract: A gear change mechanism coupling a pair of shafts employs a planetary gear set comprising a sun gear fast with a first of the shafts, planet gears in a planet carrier, and an annulus or ring gear, the latter being fixed. A selector hub slidable on the other of the shafts has sets of radially spaced dogs to engage with corresponding dogs on the planet carrier and sun gear respectively, so as to couple the shafts at two different ratios depending on the axial position of the selector hub. This results in a more axially compact package than conventional dog clutch gear changers. In an alternative embodiment a reversing mechanism is provided by fixing the planet carrier and engaging the selector hub with the sun gear or annulus depending on its axial position.

Abstract: Measuring apparatus for providing information on the relative location of a target site which is radiating a target signal that includes a predetermined pulse signal, comprises receiver means for providing a pair of temporally spaced output pulses in response to a single received said predetermined pulse signal and cross-correlation means coupled to said receiver means for cross-correlating said pair of output pulses or signals derived therefrom.

Abstract: An apparatus for detecting the presence of one or more images of a known kind in a scene is disclosed which comprises a digital input means and an optical output means. The digital input means comprises a capture means which passes a capture image to a first electronic processing means to produce a scene pattern corresponding to a Fourier Transform of the scene image. This pattern is then digitally combined with one or more reference patterns corresponding to Fourier Transforms of a reference image. The resulting combined patterns are then used to modulate a beam of light which may be focused to perform an inverse Fourier Transform providing correlation information. In a preferred embodiment, the combined pattern is displayed on a spatial light modulator.

Abstract: A method of strongly decorrelating signals comprising processing input signals to determine delay and rotation parameters which implement at least one elementary paraunitary matrix. The parameters transform the input signals into output signals with improvement in a measure of strong decorrelation. The improvement in the measure of strong decorrelation is then assessed: if it is significant the latest output signals are, designated as input signals and the process is iterated. Iteration continues until the measure of strong decorrelation ceases to improve significantly, at which point the latest output signals are designated as signals decorrelated in a wide sense.

Abstract: An optical element (3) is mechanically retained within a slot of (2) in a rigid substrate (1), e.g. of a ceramic or crystalline material, by contact with the sides of the slot. Where the difference between a dimension of the optical element and the slot width at ambient temperature is a very small and positive, it may be removed by heating the substrate and/or cooling the element (differential thermal expansion) to allow insertion of the element. Then the temperature difference is removed so that the element is mechanically retained under compression by the slot sides. Alternatively, where the element may be directly inserted so that it is in contact with or immediately adjacent the slot wall, the material of the substrate and/or the optical element is the oxidized in the region of contact so as to increase the dimension of the oxidized material and mechanically retain the element.

Abstract: An adaptive filter is implemented by a computer (10) processing an input signal using a recursive least squares lattice (RLSL) algorithm (12) to obtain forward and backward least squares prediction residuals. A prediction residual is the difference between a data element in a sequence of elements and a prediction of that element from other sequence elements. Forward and backward residuals are converted at (14) to interpolation residuals which are unnormalized Kalman gain vector coefficients. Interpolation residuals are normalized to produce the Kalman gain vector at (16). The Kalman gain vector is combined at (18) with input and reference signals x(t) and y(t), which provides updates for the filter coefficients or weights to reflect these signals as required to provide adaptive filtering.

Abstract: Autocatalytic plating is a form of electrode-less plating in which a metal, for example, cobalt, nickel, gold, silver or copper, is deposited onto a substrate via a chemical reduction process. Coatings derived from this process are usually more uniform and adherent than from other processes and can be applied to unusually shaped surfaces. Non-metallic surfaces can only usually be coated via this process following suitable sensitisation of the substrate. This invention therefore provides a method of preparing a substrate material for subsequent autocatalytic deposition of a metal coating reducing the need for surface preparation by using a reducible silver salt with a suitable filler in a printable ink formulation. Autocatalytic deposition may be used to coat whole surfaces or pre-determined patterns may be deposited by known printing methods.

Abstract: A drill resistant lock (30) comprises a bolt member (33) for fitting into a similar sized and shaped slot (35) to secure closure of entry to a property, a locking mechanism (31, 32) associated with a bolt member (33), whereby release and/or closure of the bolt member (33) into the slot (35) is effected by insertion and rotation of an appropriate key in the locking mechanism (31, 32), wherein the bolt member (33) is provided with a core (34) containing a material with different mechanical properties to the main body of the bolt member (33), the material of the core (34) being more drill resistant than the material of the main body.