Abstract: A multifilar antenna comprises n spaced antenna filaments, where n is an integer greater than 1; a matching circuit for matching the characteristic impedance of the antenna to that of a transmitting and/or receiving apparatus; a weighting circuit for applying gain and phase adjustments to signals passed to or from the n filaments; switch means associated with at least some of the filaments for selectively altering the electrical length and/or interconnections for the filaments; means for detecting electrical properties of the multifilar antenna with respect to the frequency, polarization and/or direction of propagation of a signal to be received or transmitted by the multifilar antenna and/or impedance matching of the antenna; and control means, responsive to the detecting means, for controlling the operation of the matching circuit, the weighting circuit and the switch means to adjust the properties of the multifilar antenna to suit better a current signal to be received or transmitted.

Abstract: A mobile station positioning method for a cellular communications system includes evaluating an initial position estimate of a target mobile station having an initial area of uncertainty, evaluating a position estimate of a further mobile station of the system, estimating distance between the target and further mobile stations and using the position and distance estimates to evaluate a new position estimate of the target mobile station having a reduced area of uncertainty. Bi-circular and tri-circular methods are described.

Abstract: A surface-light-emitting device including a semiconductor substrate, and a laminar semiconductor structure consisting of a plurality of semiconductor layers formed by epitaxial growth on the semiconductor substrate, the laminar semiconductor structure including a light-generating layer, and two multi-film reflecting layers between which the light-generating layer is interposed and which constitute a light resonator for reflecting a light generated by the light-generating layer, the structure having a light-emitting surface at one of opposite ends thereof remote from the substrate, so that the light generated by the light-generating layer is emitted from the light-emitting surface, wherein the two multi-film reflecting layers consist of a first multi-film reflecting layer formed principally of AlGaInP on the substrate, and a second multi-film reflecting layer formed principally of AlGaAs on one of opposite sides of the light-generating layer which is remote from the substrate.

Abstract: A speech coder includes an encoder using an analysis and synthesis approach. The encoder uses a pitch determination algorithm requiring analysis in both the frequency domain and the time domain, a voicing determination algorithm and an algorithm for determining spectral amplitudes and means for quantising the values determined. A decoder is also described.

Abstract: An optoelectronic semiconductor device in the form of an LED comprises a silicon p-n junction having a photoactive region containing beta-iron disilicide (&bgr;-FeSi2). The LED produces electroluminescence at a wavelength of about 1.5 &mgr;m.

Abstract: A phase noise reduction circuit for reducing phase noise in an input pulse train consisting of pulses which are all of the same length and which, in the absence of phase noise, have a nominal frequency f, includes a DC removal circuit for removing a DC level from the input pulse train, an integrator for integrating the input pulse train after a DC level has been removed therefrom by the DC removal circuit and a comparator for deriving from the integrated pulse train an output pulse train containing periodic transitions at said nominal frequency. The input pulse train may be derived using a monostable circuit.

Abstract: A process is provided for forming a silicon material which exhibits room temperature photoluminescence and/or electroluminescence. It comprises the steps of implanting silicon ions into a silicon oxide (SiO.sub.2) substrate and subsequently annealing the substrate at an elevated temperature for a period such as to bring about Si nanocrystal formation, the nanocrystals being dispersed through the SiO.sub.2 substrate. Photoluminescence of visible light from the resulting substrate is induced on irradiation of the substrate with e.g. ultraviolet light, and the substrate can also be incorporated into an electroluminescent device. The process is characterised by the features of implanting silicon ions at a dose from 1.times.10.sup.17 /cm.sup.2 to less than that required to produce saturation and by the use of an implantation energy of 100 keV or more. The resulting silicon nanocrystals dispersed through the SiO.sub.2 substrate have an average particle size of about 30 .ANG..

Abstract: A radiation detector has a dual-capacitive structure comprising an array A of first capacitors (10) including discrete electrodes (13) arranged in rows and columns and a second capacitor (20). The second capacitor (20) incorporates a radiation converter (21) which co-operates with the first capacitors (10) to cause an accumulation of charge on the discrete electrodes (13) according to the spatial distribution of radiation to which the radiation converter is exposed. Read-out means (30) is provided to output a signal representative of the accumulated charge.

Abstract: A structural connection between a tubular thermosetting plastics member and a thermoplastics end cap is described. An end of the tubular member is inserted into an annular, axially extending gap in the thermoplastics end cap. The inner and outer wall surfaces of the gap are threaded. Adhesive fills the space between the end of the tubular member and the threaded surfaces of the gap.

Abstract: A weight-coated pipe has an innermost anti-corrosion layer, a helically-wound covering of a cementitious sheeting having a reinforcement of organic fibrillated film network arranged as a plurality of superposed layers. This covering is applied in a post-cracked condition so that constituent parts of the next layer of concrete penetrate the micro-cracks and form a good bond. An outer layer of helically-wound sheeting similar to the first-mentioned covering serves to protect the weight-coating of concrete from impact damage.

Abstract: A method and apparatus are provided for classifying areas on a raster-type display unit. The problem is to identify areas defined by a closed boundary--e.g. for filling in such areas. Boundary data are entered into a first "polygon" store which has a plurality of memory locations each corresponding to a respective dot position of the display field, and at least one seed point is identified. Each dot position is then examined to see whether there exists a connected path, not including a boundary position, from it to a seed point, and if there is, this fact is recorded. The criterion for deciding whether or not a path is connected depends on the definition of what constitutes a closed boundary.

Abstract: A material primarily for replacing asbestos-cement products includes a reinforcing network of continuous, fibrillated organic film and a water-hardened mass such as Portland cement and sand or alternatively gypsum. The organic film may be a polyolefin such as polypropylene or high modulus polyethylene. The reinforcement may be incorporated as a woven or non-woven network.A process for making such a material is also described.The material has, in some respects, superior properties in relation to those of asbestos-cement.