Abstract: A method of measuring the contents of a search volume.

Abstract: A method of measuring the contents of a search volume.

Abstract: Various methods and apparatus are described for reducing signal artifacts resulting from reflections from the surface of the object. In one method, a similar paths algorithm is used to create a calibration signal to reduce signal artefacts. In another method, an equivalent location algorithm is used to create calibration data to reduce signal artefacts. In another method, blocking screens are positioned in contact with, or closely adjacent to, the surface. In another method, an anti-reflective layer is employed. The methods may be employed singly or jointly in a breast tumour imaging device.

Abstract: A technique for adapting receiver thresholds to improve rate-based flow control in a data communications network. With this invention, the flow control process becomes self-calibrating such that threshold values are dynamically adjusted to adapt to current network conditions, without requiring user intervention. Several different indicators of network conditions are monitored, and appropriate adjustments are made to the threshold(s) upon detecting these specific indicators. One monitor enables the threshold to increase when the network is uncongested, enabling the sender to increase its transmission rate. Conversely, the threshold is lowered if the network is congested, so that the transmission rate will be decreased. Another monitor balances bandwidth allocation among connections sharing a bottleneck resource, by lowering the threshold (and therefore decreasing the send rate) when a connection uses a high share of the resource.

Abstract: A screening system for screening items, such as aircraft-hold luggage, uses a conveyer system for carrying the items along a path and an array of sensors spaced along and around the path for determining the opacity to radiation in planes intersecting the path and the items. A signal processor uses signals from the sensors to detect contours of maximum local rate of change in opacity and from these reconstruct boundaries between the regions having different opacity to radiation and then determines whether or not one or more predetermined screening criteria are met.

Abstract: An apparatus is provided in which a phased transmitting array (21) is arranged to irradiate a selected voxel within a search volume. Energy reflected from the voxel is received by a further antenna and the signals received from a plurality of voxels are analysed to search for reflectors or discontinuities within the search space.

Abstract: An apparatus is provided in which individual transmit elements (18) of a transmit array are actuated in turn in order to interrogate a search volume Signals reflected from the volume are received by one or more reception elements (20) of a receive array and are recorded. The propagation parts to a selected cell are calculated and appropriate phase and or time shifts are inserted into the recorded data to simulate, post reception, the shifts that would have occurred if either or both of the transmit and receive arrays had been focused on the cell using phased array beam steering techniques.

Abstract: A method of generating images of a specimen containing at least two regions of different opacity to the passage of radiation comprises irradiating the specimen with radiation from a radiation source, detecting the radiation to produce a plurality of signals indicative of the amplitude of the radiation passing through the specimen in a corresponding plurality of different directions and processing the signals to derive further signals indicative of contours of maximum local discontinuity in opacity or texture thereby providing an indication of the position of the three-dimensional boundary surface between the two regions.

Abstract: A reflector antenna comprising a reflector system, and a feed system, for instance a log-periodic feed system, the phase center of which moves with frequency, for illuminating the reflector system to produce a substantially focussed antenna beam. To compensate for frequency variations in the position of the phase-center of the feed system, the reflector system includes a frequency dependent reflector the effective surface of reflection of which varies with frequency to cause the focus of the reflector system to move with the phase-center of the feed system. A number of different forms of suitable frequency dependent reflectors are described, employing composite arrangements frequency selective mesh or grid reflector elements, or arrays of reflecting horns or wedges.