Abstract: A passive mm-wave imager comprises an optical immersion lens arrangement which is illuminated by front end optics and an array of detectors (12a) to (12d) located in the focal plane of the immersion lens arrangement. The detectors comprise antennae coupled high temperature superconductor weak links, in particular C-axis cross-over or step microbridges.

Abstract: A method and apparatus for processing of a signal in which a variation in phase between a transmitted and reflected pulse is modeled, as is the amplitude of the pulse. The modeled phase and amplitude are used to smooth the data by reducing phase noise present on the signal thereby enhancing the signal to noise ratio.

Abstract: A passive mm-wave imager comprises an optical immersion lens arrangement which is illuminated by front end optics and an array of direct detectors (12a) to (12d) located in the focal plane of the immersion lens arrangement. The detectors comprise antennae coupled high temperature superconductor weak links, in particular C-axis cross-over or step microbridges.

Abstract: A method and apparatus for processing of a signal in which a variation in phase between a transmitted and reflected pulse is modelled, as is the amplitude of the pulse. The modelled phase and amplitude are used to smooth the data by reducing phase noise present on the signal thereby enhancing the signal to noise ratio.

Abstract: A radiation sensor for the microwave and millimeter-wave regions incorporates a lens having two parallel focal planes, these being defined by a polarization-selective reflector grid within the lens. One focal plane is occupied by a receive array of crossed dipole antennas with respective mixer diodes. One dipole of each antenna couples to a local oscillator signal and the other couples to a receive signal reflected by the grid. These signals are mixed by the diodes to produce intermediate frequency signals for subsequent processing. The other focal plane is occupied by a transmit array of separately activatable polarization switching antennas arranged to define a range of transmit beam directions. This focal plane may alternatively be occupied by a second receive array.

Abstract: An infrared detector comprises a thin film of photo-responsive material on transparent dielectric material with an array of planar antennae adjacent to the film surface. The antennae are separate from ohmic contacts arranged to connect the film to an external circuit. The antennae concentrate radiation in fringe fields at antenna edges and extremities interacting with the photo-responsive material. The detectors may be photovoltaic or photoconductive. The antennae may be rectangular, bow-tie, cruciform, elliptic, circular or square, and are dimensioned for resonance (preferably half-wavelength resonance) at frequencies within the photo-responsive material absorption band. Half-wavelength resonant antennae are best matched by F/0.7 optics. The detector may be a reticulated array. The dielectric material may be formed as a lens.

Abstract: A radiation sensor for centimeter, millimeter or sub-millimeter waveband receiption, comprising a metal antenna located close to a supporting dielectric body of intermediate to high dielectric constant value and having a mixer located in between and connected to the limbs of the antenna. The supporting body may itself be of semiconductor material, or if of insulating dielectric material, semiconductor material may be incorporated adjacent the antenna; and the mixer components, diodes, integrated in the semiconductor material. Antennae, as above, may be arranged in close-packed array, and the supporting body configured as, or as part of, a lens.

Abstract: A radiation sensor for centimeter, millimeter or sub-millimeter waveband receiption, comprising a metal antenna located close to a supporting dielectric body of intermediate to high dielectric constant value and having a mixer located in between and connected to the limbs of the antenna. The supporting body may itself be of semiconductor material, or if of insulating dielectric material, semiconductor material may be incorporated adjacent the antenna; and the mixer components, diodes, integrated in the semiconductor material. Antennae, as above, may be arranged in close-packed array, and the supporting body configured as, or as part of, a lens.

Abstract: An electromagnetic radiation sensor for use at microwave frequencies compes a sheet substrate bearing an array of dipolar antennas. The antennas have respective mixer diodes connected between adjacent dipole limbs, and the antenna array is located in the focal plane of a dielectric lens. Individual antenna center positions correspond to different beam directions for radiation incident on the lens, and the antenna center positions are in accordance with the Rayleigh resolved spot criterion. The dimensions, dielectric properties and relative positioning of the lens and substrate are such as to provide for the antennas to couple predominantly to radiation passing through the lens. The substrate thickness may lie between the lens and antenna array, or alternatively the array may lie between the substrtate and lens. In the latter case, the lens is of higher dielectric constant material than the substrate, at least in the lens region adjacent the array.

Abstract: An antenna device comprises a dielectric sheet substrate having an antenna patch on one surface and a ground plane on the other surface. A hemispherical dielectric lens is arranged over the antenna patch in intimate contact with it. The substrate and the lens are of low and high permittivity material respectively. The lens couples the antenna patch radiation away from the substrate. This avoids the inefficiency arising from power trapping in the substrate of a prior art microstrip patch antenna. The antenna device radiates into a comparatively narrow cone axially perpendicular to the antenna patch, and coupling of radiation from a power source to free space can theoretically be 100%. The antenna impedance is a function of its structural geometry, and is easily designed for impedance matching to a power source.

Abstract: A transferred electron device includes a novel cathode giving improvement in the dc to microwave conversion efficiency over a wide temperature range. The cathode comprises a narrow n.sup.+ semiconductor zone next to the device active region or layer and, next to the n.sup.+ zone, a high field contact which includes a region of semiconductor.

Abstract: A field effect transistor for operation at temperatures below 150.degree. K. is capable of operating at low voltage and current levels at high speed. The transistor is fabricated by deposition of metal source drain and gate electrodes upon a layer of semi-conductor having a concentration of free carriers less than 10.sup.16 cm.sup.-3 formed on a substrate having a resistivity greater than 10.sup.4 ohm-cm.