Abstract: High power fibre amplifier systems avoid inadvertent generation of Stimulated Brillion Scattering (SBS) that causes optical losses and, if large enough, may damage the system. The standard active technique used to suppress SBS is to modulate the seed beam with a radio frequency line width broadening signal, e.g. white noise, to increase the spectral linewidth of the seed beam. This significantly increases the threshold power at which SBS becomes a problem by significantly reducing the coherence length. The problem accompanying a reduced coherence length is that the tolerance in variations in optical path length reduces markedly. The solution provided to this problem is to delay the line width broadening signal by predetermined amount to compensate for the difference in optical path lengths.

Abstract: Sinuous and log-periodic antennas are wideband frequency independent antennas which provide a similar beam width at all frequencies of operation. They can have improved directivity characteristics when formed over a conical or similar surface. Fabrication of these three-dimensional antenna structures is difficult. Exemplary embodiments disclosed herein include a dielectric sheet formed as a single integral piece that defines a central common region and radially extending arms. The flexible dielectric sheet carries a metallic patterned layer that defines, on each arm, a conductive antenna element each fed by a conductive trace provided by a portion of the metallic pattern layer formed on the common region. Each arm can be bent at its join (e.g., joint) with the common region to conform with the shape of the former without affecting the alignment between the arms.

Abstract: An active imaging system including a laser to illuminate a scene and an imaging device to receive returns reflected from the scene. The imaging device including an array of pixel circuits, each pixel circuit including a photodiode connected to multiple track and hold circuits and a timing circuit configured to operate the track and hold circuits in quick succession such that each track and hold circuit captures an information signal indicative of returns arriving during different successive time periods during a gate period and thus provides 3D image data based on the arrival times of returns from the scene during the gate period.

Abstract: An active imaging system including a laser to illuminate a scene and an imaging device to receive returns reflected from the scene. The imaging device including an array of pixel circuits, each pixel circuit including a photodiode connected to multiple track and hold circuits and a timing circuit configured to operate the track and hold circuits in quick succession such that each track and hold circuit captures an information signal indicative of returns arriving during different successive time periods during a gate period and thus provides 3D image data based on the arrival times of returns from the scene during the gate period.

Abstract: An optical amplifier system as disclosed includes a gain medium and a pump mechanism configured to amplify first and second optical beams when they pass through the gain medium. The first and second beams, which have the same wavelength, take different paths through the gain medium such that the beams are neither parallel nor coaxial when they exit and/or enter through a first side of the gain medium. A prism having a facet positioned on the first side of the gain medium is in the path of both beams. The facet is orientated to cause total internal refection of the one of the beams within the prism but be transmissive to the other, so that paths of the two beams can be altered relative to one another allowing the beams to be either brought closer together or separated out.

Abstract: A method of simulating radar ground or sea clutter for testing and designing of radar by providing a terrain model including discrete flat ground patches each having a reflectivity, area, surface normal vector, and position within a global coordinate frame, calculating triplet values of reflected energy, range and Doppler shift for each discrete patch of the terrain model for a given position and pose of an antenna with known gain and phase characteristics within the global coordinate frame; and for a given radar receiver sample rate and Pulse repetition frequency (PRF), resampling and integrating over all patches through carrying out a 2D transformation using a non-uniform Fast Fourier Transform. The method can correct the lack of spatial correlation and increase the speed at which realistic ground clutter modelling can be generated.

Abstract: A laser system having an optical ring resonator, a beam splitter that directs a first beam travelling in a first direction around the ring resonator, out of the resonator towards a reflector that reflects the first beam back into the resonator to travel in an opposite direction around the optical ring resonator that is in the same direction as a second beam travelling around the optical ring resonator; and a beam modifier configured and adapted to modify a spatial distribution of phase across an aperture of the first beam such as to cause it to become more similar or substantially match that of a spatial distribution of phase across an aperture of the second beam.

Abstract: There is described a dielectric polariser for a bicone antenna. The polariser can include radiating vanes that are spaced circumferentially around an aperture of the bicone antenna. The vanes are orientated at 45° to the polarised waves propagated from the antenna in order to circularly polarise the linearly polarised waves. The polariser can be configured for manufacture using a 3D printing process. Surfaces of a central hub of the polariser can be metallised to provide the radiating surfaces of the antenna. This removes the need to use separate antenna elements. Alternative arrangements of 3D printed dielectric polariser are disclosed for use with antenna horns.

Abstract: A balanced amplifier system having input and output quadrature couplers or equivalents thereof and two amplifiers there between. An RF signal is presented to a first input of an input quadrature coupler such that an amplified RF signal is output at a first output of the output quadrature coupler. A RF control signal is presented to a second input of the quadrature coupler such that an amplified control signal is outputted at the other output of the output quadrature coupler. The system is configured to reflect the amplified signal back into the second port of the output quadrature coupler in order to vary an impedance seen by the amplifiers of the balanced amplifier.

Abstract: Improving the signal to noise ratio in an optical link involves either reducing the noise or increasing the RF power coupled into the optical link by lowing the voltage, V?, required to induce a phase change of ? of the optical beam passing through the optical modulator. The present disclosure relates to methods and architectures for increasing the optical power through a link through providing one or more laser sources, additional modulators or photodiode receivers and dividing the optical power through these components so that none are overloaded.

Abstract: An active imaging system including a laser to illuminate a scene and an imaging device to receive returns reflected from the scene. The imaging device including an array of pixel circuits, each pixel circuit including a photodiode connected to multiple track and hold circuits and a timing circuit configured to operate the track and hold circuits in quick succession such that each track and hold circuit captures an information signal indicative of returns arriving during different successive time periods during a gate period and thus provides 3D image data based on the arrival times of returns from the scene during the gate period.

Abstract: A gas-liquid separator includes a chamber having an inlet for liquid to enter and at least one outlet for expulsion gas and/or vapour that has separated from the liquid within the chamber under gravity. For some applications the chamber will also have an outlet for the liquid. These systems can rely on the chamber remaining in a static orientation with the gas outlet arranged uppermost. Exemplary embodiments provide the chamber with multiple spaced apart outlets and an ability to sense orientation and/or acceleration of the chamber. A controller uses the output of the sensors to determine the spatial arrangement of the liquid phase and gas phase within the chamber relative to the outlets and selectively opens the multiple outlets to allow one of the liquid phase or gas phase to escape the chamber in preference to the other.

Abstract: The system includes first and second laser illuminators to illuminate a scene, including a target. The pulses of light emitted from the first laser illuminator having a relatively broad spectral linewidth and a relatively long pulse duration compared with pulses of light from the second laser illuminator. A camera system uses a relatively long gate period for receiving returns from the first laser illuminator to obtain a first image of the scene and to use a relatively short gate period together with ranging information of the target to receive returns from the second laser illuminator to obtain a second image of the target that selectively excludes non-target elements within the scene. The second image is used as a template to selectively remove the non-target elements from the first image.

Abstract: Many electro-optical systems include an environmental window that shield the sensor and optical train from environmental conditions. Where the electro-optical system is mounted on a high speed platform it can be necessary to shape the window away from the ideal optical shape of a hemisphere to one that is more aerodynamic. The optical train can include corrector elements to correct aberrations resulting from the non-ideal shape of the window. The exterior surface is configured to a specific biconic equation and that specified biconic equation is used to define the surfaces of the corrector element(s) of the optical train. This provides a more uniform wavefront error and magnification across the field of regard.

Abstract: A radar system includes two circuit boards, a first carries an array of antenna elements and the second carries power circuitry to power the circuitry of the first board. To provide adequate cooling whilst minimising the size of the system the two circuit boards are mounted in a sandwich arrangement on opposite sides of a heat sink. Data and power connections between the two boards are provided by a plurality of electrical cables that extend through apertures in the heat sink.

Abstract: Mercury cadmium telluride (MCT) dual band photodiode elements are described that include an n-type barrier region interposed between first and second p-type regions. The first p-type region is arranged to absorb different IR wavelengths to the second p-type region in order that the photodiode element can sense two IR bands. A portion of the second p-type region is type converted using ion-beam milling to produce a n-type region that interfaces with the second p-type region and the n-type barrier region.

Abstract: Mercury cadmium telluride (MCT) dual band photodiode elements are described that include an n-type barrier region interposed between first and second p-type regions. The first p-type region is arranged to absorb different IR wavelengths to the second p-type region in order that the photodiode element can sense two IR bands. A portion of the second p-type region is type converted using ion-beam milling to produce a n-type region that interfaces with the second p-type region and the n-type barrier region.

Abstract: The present disclosure relates to manufacture of an active array antenna from a combination of modular sub-arrays, nominally of equal size; each sub-array being associated with a separate receiver and/or transmitter. A solution to calibrating a modular array is the inclusion of a calibration manifold having multiple 1st ports that connect to respective sub-arrays between their passive network and their respective receiver and/or transmitter. Each of the first ports communicate with a common second port through which a signal can be introduced in order to be received at each element of each sub array, or through which a signal from any element of any sub-array can be received. This allows any element of the sub array to be calibrated at any time including during operation.

Abstract: A laser is disclosed having a housing formed of a block of glass-ceramic. The block is machined (or otherwise formed) to define one or more channels that act as a waveguide in two dimensions for light within the laser resonator. The channels extend between cavities also formed within the block which retain optical components of the laser, e.g. one or more of the gain medium, cavity mirrors, intermediate reflectors etc. The positioning, shape and size of each cavity is bespoke for the optical component it holds in order that each optical component is retained in optical alignment rigidly against the sides of the cavity.

Abstract: Mercury cadmium telluride (MCT) dual band photodiode elements are described that include an n-type barrier region interposed between first and second p-type regions. The first p-type region is arranged to absorb different IR wavelengths to the second p-type region in order that the photodiode element can sense two IR bands. A portion of the second p-type region is type converted using ion-beam milling to produce a n-type region that interfaces with the second p-type region and the n-type barrier region.