Abstract: A receiver-transmitter for a target identification system having a particular but not necessarily an exclusive application for the identification of aircraft which utilizes laser vibrometry and a coherent array receiver including an array of photodetectors adapted to receive signals from different parts of the target and to use a corresponding array of frequency-offset reference beams to provide coherent detection of each of the received signals.

Abstract: In a process and apparatus for annealing a substance, such as polysilicon, which is deposited on a substrate, such as a glass plate, the annealing temperature is required to be greater than the softening temperature of the substrate. To prevent deformation of the substrate it is supported on a liquid of density greater than that of the substrate. The liquid is preferably molten tin.

Abstract: A device for measuring the relative proportions of gas, oil and water in a conductive pipe includes at least one open-ended, conductive tube having a radius different from the pipe, disposed within the pipe. Microwave transmission structure transmits microwave signals along the pipe and the at least one tube at a plurality of frequencies, the pipe and the at least one conductive tube acting as waveguides for the microwave signals. At least two microwave receiving devices are disposed at separate positions having different respective radii, spaced apart along the pipe and at least one tube, for receiving the microwave signals transmitted by the transmission structure. Determining circuitry determines the relative proportions of gas, water and oil in the pipe by comparing the transmitted and received signals.

Abstract: Radar reflector structure is disclosed including a plurality of reflector elements which in use are arranged in a non-planar configuration, the reflector elements include a thin flexible member extending between adjacent reflector elements substantially at or below the surface of the elements, the thin flexible member thereby providing a flexible hinge between the elements.

Abstract: An analog-to-digital converter includes a filter having an input for receiving, via a summing node, a signal derived from the analog input signal. A first quantizer produces a first digital signal from a signal derived from the output of the filter. A feedback loop feeds a signal derived from the first digital signal to be combined in analog form with the signal derived from the analog input signal at the summing node, so that the filter in use receives an error signal representing the difference between the signal derived from the analog input signal and the analog representation of the first digital signal. An error signal filter filters the error signal to remove noise outside the passband of the analog-to-digital converter. A second quantizer produces a second digital signal representative of the filtered error signal, and a combining circuitry combines the first and second digital signals to produce a digital output signal representative of the analog input signal.

Abstract: A transponder system comprising an interrogating source of HF electromagnetic radiation, and a plurality of transponders which each include a token reader unit to receive a removable token, e.g., a smart card, including onboard data processing capability. The transponders, or a group of transponders, are each arranged when interrogated to transmit a unique HF response modulated by information taken upon the token.

Abstract: In a process for producing a narrow groove in a layer of, for example, silicon nitride, a wide groove is first formed in the layer. A layer of a metal, for example aluminium, is evaporated on to one side of the wide groove. The remainder of the wide groove is then filled with a material such a silicon nitride. The metal layer is then etched away, leaving a narrow groove in the silicon nitride equal to the thickness of the metal layer.

Abstract: An electrical apparatus has a number of units (1 to 6), each of which is capable of presenting a transfer function of a different value to an input signal. It also includes control circuitry (7, 9) whereby a desired selection of units (1 to 6) can be made so as to present to the input signal a total value of desired transfer function. The values of the units are chosen such that the ratio (B) between a function value and the next smaller value is less than 2:1.

Abstract: A sensor, for use in determining physical properties of fluid, comprises a flexible diaphragm having a plane. Two tines depend from the diaphragm substantially at right angles to the plane. First and second substantially planar transducers are each bonded to the diaphragm so that the plane of the transducers are parallel to that of the diaphragm. A first one of the transducers is operative, in use, to flex between in its plane and to couple an alternating driving force into the plane of the diaphragm such that the tines vibrate in an oscillatory motion. Second of the transducers is operative to detect vibrations of the diaphragm.

Abstract: An optical fiber arrangement providing uniform illumination of a region in a plane beyond the end of an optical fiber and normal to the fiber axis. An array (12) of four prisms (A,B,C,D) is disposed adjacent to, but spaced from, an end (11) of an optical fiber (5). By appropriate choice of the prism angle (.theta.) and its spacing (d) from the fiber (5), the prism array (12) modifies the angular distribution of light from the fiber (5) in two ways. The shape of the illuminated region is changed from circular to square and the illumination becomes substantially constant over the square region. In an assembly of fibers, each modified in this way, the amount of overlap needed between the outputs of neighbouring fibers can thus be reduced and a more uniform light output can be achieved. Other non-circular regions of illumination, for example of pentagonal and hexagonal shape, can be produced using different optical components and the same benefits obtained.

Abstract: A superconducting ceramic composition which is free of thallium, the composition having a unit cell containing two perovskite structure copper-oxygen planes and a rocksalt structure layer having a single plane containing cadmium.

Abstract: An electrically-controllable wave plate comprises a layer of liquid crystal material having positive dielectric anisotropy, the layer being contained between two transparent plates. An alignment layer is provided on each plate for causing homeotropic alignment of the LC molecules adjacent the plate. Electrodes are so positioned that they apply an electric field substantially along the plane of the LC layer so that the molecules acquire variable tilt through the thickness of the layer, resulting in birefringence of the layer. The wave plate may be used in a polarisation controller.

Abstract: An optical device comprising a length of optical waveguide (1) having incorporated therein an extended sequence of coupled single resonator structures (9) so as to form an optical slow wave structure. The sequence of resonator structures is suitably formed by a Bragg diffraction grating pattern (7) extending along the waveguide.

Abstract: The invention provides a method of determining the range of a radar signal reflecting object by utilizing a radar frequency carrier wave modulated by a first short code having a first repetition rate and a second code having a bit rate equal to the first code repetition rate. A received echo is first passed to an analogue correlator for correlation against a delayed version of the first code, and the output of the analogue correlator is fed to a digital correlator for correlation therein against the second code. In this way, the high bandwidth (greater range resolution) of analogue correlation can be combined with the lower bandwidth (longer ambiguity function) of digital correlation to provide high resolution target detection without ambiguity and at a fast rate without the need for a very large number of correlators.

Abstract: An imager for the implementation of microscan comprises a member 18 for interrupting radiation between a lens and an array of imaging elements 13. The member 18 comprising alternate refractive transmissive regions 25 and non-transmissive regions 24. The transmissive regions 25 refracting radiation transmitted through them in the direction shown by the arrows. As the disc rotates across the array 13 the image focused on it moves giving successive frames which are shifted relative to one another.

Abstract: A radio receiver 1 has a device for reducing interference in an r.f. received signal, for example an HF signal conveying high speed data, including a channel estimator 3 for estimating the transmitted signal by comparing the received signal with locally generated signals processed in dependence on the response of the communication channel, together with a filter 2 for filtering interfering signals from the received signal. The use of the channel estimator for compensating for the response of the communication channel as opposed to an equaliser enables interfering signals to be filtered from the received signal.

Abstract: This method enables two components (1, 3) to be joined by soldering using heat generated by a laser beam, without the use of flux. A layer (5) of a material which has a lower melting point than the material of one of the components (3) is formed on that component and forms a bond therewith on resolidifying after melting. Solder (7) is interposed between the layer (5) and the other component (1) to form, on resolidification after melting, bonds with the material of the layer (5) and the other component (1). A coating (11) of a further material between the layer (5) and the solder (7) is dispersed when the adjacent layer material becomes molten and is not wetted by the solder (7) when molten. On applying heat to a region (15) of the layer using a laser beam, the layer is melted in this region (15) as is the adjacent solder (7) to form, on resolidification of the solder (7) and molten layer material (15 ), bonds between the solder (7) and the two components (1, 3).

Abstract: A thermal imager system comprises a scanning system 1 for scanning a required scene 2 and an anamorphic optical system 3 for focusing the scanned scene onto a Sprite detector 4, the optical anamorphic system comprises a pair of optical prisms 17, 19 disposed between a collimating element 15 and a focusing element 21, one or both of the prisms 17, 19 being pivotally mounted whereby the anamorphic ratio and hence the focal length of said optical system 3 may be changed. (FIG. 1).

Abstract: A unit for detecting a moving person or object by means of doppler frequency shift. The unit comprises a microwave circuit board (1) accommodating an oscillator and a mixer, and an antenna board (2) carrying transmit (8) and receive (9) patch arrays. In the assembled unit the two boards (1,2) are disposed adjacent one another. Coupling between the microwave circuit and the antenna arrays is achieved by two slots (6,11) resonant at the oscillator fundamental frequency and formed in a ground plane (5) on the microwave board (1). Feed striplines (7,10,12) on the two boards (1,2) lie orthogonal to the slots (6,11) and are terminated in T-sections (15,14). The stripline/slot arrangement suppresses emission at the oscillator second harmonic frequency. The antenna board (2) has no electrical connection to the microwave circuit, enabling the radiated beam shape to be changed by simply replacing the antenna board with one having a different patch array pattern.

Abstract: A clamp mechanism (19) for clamping the edge (17) of a printed circuit board (11) between the side walls (91a, 91b) of a slot in a wall (93) of an enclosure for housing the board in parallel spaced relationship with other boards. The mechanism (19) comprises an elongated element (21) of resilient material having corrugations (23) whose crests are at regularly spaced positions along its length. An actuator (25) coupled with the elongated element for relative longitudinal motion therewith is provided with riser elements (31b) spaced like the corrugations and positioned so as to move on such relative motion into engagement with the crests to effect the required clamping action. The riser elements (31b) are in the form of rollers (31b) to minimize functional resistance to operation. A spigot arrangement (89, 95) on a lever 75 for operates the mechanism which provides positive locking of the board (11) when clamped.