Abstract: A time sharing jammer comprises two sources of jamming signals 1 and a switch 4 for coupling the sources of jamming signals to a microwave power amplifier 6, such as a travelling wave tube. A pseudo random code generator 8 is provided which is arranged to cause operation of the switch 4 whereby the sources of jamming signals 2 are coupled to the power amplifier 6 in accordance with the pseudo random code.

Abstract: A continuous wave ranging system, comprising a modulator 2 for modulating an r.f. carrier wave in accordance with a pseudo-random code 3, a transmitting antenna 5 for radiating the modulated signal towards a target, a receiving antenna 6 and receiver 7 for detecting the signal reflected back from the target, a correlator 8 for correlating the reflected signal with a transmitted code with a selected phase shift 9 corresponding to the current range gate to be tested, and means 10, 11, 12 for processing the range/amplitude data from the correlator 8 to discriminate between reflections due to the target and those due to other objects adjacent to the target.

Abstract: A system for correcting the effect of radome aberration on line-of-sight signals indicating target position. The aberration is in fact dependent upon both operating frequency and ‘angle-of-look’ and the essence of the present invention is to separate the corrections appropriate to each of these factors. The apparent line-of-sight signals are subjected to a frequency dependent amplification the result being used to address a store of error correction data. The apparent line of sight signals are also used to address a second store of error correction data and the two sets of correction data are added into the apparent line-of-sight signals to give true line-of-sight.

Abstract: A dual mode radar seeker comprising a wide-band passive anti-radar antenna system (3) at the rear of a radome (1), operating at relatively low radar frequencies in an amplitude comparison tracking mode, and a high-frequency (W-band) active amplitude-comparison antenna system (5) in the nose of the radome (1) and having a common boresight with the anti-radar system. The active system employs coarse phase shift steering (31, 41) of the antenna ‘beam’ for the transmit and, optionally, also, the receive ‘beam’. The high frequency and the use of phase shift steering both help to keep down the size of the active radar thus enabling it (5, 7, 9) to be positioned far forward in the nose of the radome (1) so as not to obscure the field of the anti-radar system (3).

Abstract: A wave-form generator drives a number of microwave generating devices each operating at different frequency bands. The output of each microwave generator is connected to its own transmission channel of limited bandwidth which contains all the non-linear components necessary for transmission such as an amplifier, T/R switch, rotary joint and beam switch. These individual channels are finally combined onto a common wideband channel which contains only substantially linear components such as a single waveguide and the antenna itself. Because of the isolation between channels there is little or no opportunity for the generation of harmonics or intermodulation distortions which would otherwise occur in a transmitter capable of operating over a very wide bandwidth.

Abstract: A support actuator 20 comprises an electro-magnet 21 having an input current 22, provided through a current controller 23, and which is arranged to generate a magnetic field 24 having a variable intensity proportional to a variable current 25 supplied by the controller 23. The intensity of the field 24 is controlled to ensure that the magnet 21 is separated from a support armature 26 arranged to carry a load by an operational gap 27. A load cell 28 is connected between the armature 26 and a mounting position 29 for the armature 26. The cell 28 produces a control signal 30 representing variations in force generated by the magnetic field 24 which acts on the load, and the signal 30 is fed backward, along a feedback control path 31 to the controller 23 so as to control the variable current 25 such that it is made substantially equal to a gain demand force D.

Abstract: A combiner (10) has a glass reflector (11) with first and second curved surfaces (12, 13) each having an optical coating. A first prism (14) has a surface (15) which complements the surface (12) of the reflector (11) and a second prism (16) has a surface (17) which complements the surface (13) of the reflector (11). The surfaces (12 and 13) and the surfaces (15 and 17) are each primed and allowed to dry before being polished. The reflector (11) and prisms (14 and 16) are arranged with respect to one another such that surface (12) forms a well (18) with surface (15) and similarly surface (13) forms a well (19) with surface (17). The wells (18, 19) are completed with a seal (20) at a lower end (21) and bonding agent (22, 23) is injected into the wells (18, 19). The combiner (10) is placed in a vacuum chamber to remove trapped air bubbles and the agent (22, 23) is allowed to cool at a temperature which does not unduly stress the reflector (11) and prisms (14 and 16).

Abstract: Detection of remote acoustic signals is achieved using a pulse to pulse coherent laser beam which is projected from a telescope to a remote region that contains acoustic signals from a nearby source. Light from the beam is scanned in the region and a resultant signal collected by a telescope. The signal and a reference are applied to an interferometer and the resultant interference pattern applied to a photoreceiver. An alternating current is produced across the photoreceiver which corresponds to the scattered light from the beam caused by the periodic movement of acoustic signals through a region. The detector can be used to determine the curvature of an acoustic signal wavefront and to detect the location of a source producing the acoustic signals.

Abstract: A support actuator 20 comprises an electro-magnet 21 having an input current 22, provided through a current controller 23, and which is arranged to generate a magnetic field 24 having a variable intensity proportional to a variable current 25 supplied by the controller 23. The intensity of the field 24 is controlled to ensure that the magnet 21 is separated from a support armature 26 arranged to carry a load by an operational gap 27.

Abstract: A coherent radar detection system (2) comprises a radar signal transmitter (4) and a correlation receiver (6). The transmitter (4) comprises a waveform generator which generates a signal at an intermediate frequency. The signal is divided into two divided signals by a coupler, and then the divided signals are mixed together in a mixer to generate an output signal which has a wider bandwidth than the intermediate frequency. The bandwidth can be increased further by repeating the coupler/mixer stage. The system generates very wide bandwidth signals coherently, allowing coherent processing in high resolution range gates.

Abstract: An aircraft radar and altimeter system, comprising a radio transmitter and a transmitting antenna for radiating a beam of radio energy, a radio receiver and receiving antenna for receiving radio energy reflected from the ground, processing means for comparing the signal received by the receiver with the signal transmitted by the transmitter and determined from the comparison the instantaneous altitude of the aircraft above the ground, and means for changing the direction of radiation of the beam relative to the aircraft to compensate for changes in the attitude of the aircraft relative to the horizontal about at least one of the fore and aft and side-to-side axes.

Abstract: A weapon system comprising a mobile platform (1) e.g. an aircraft incorporating a first three-axis attitude reference sub-system (13), and a guidable vehicle (3) launchable from the platform (1) and incorporating a guidance sub-system (15) incorporating gyros (17) wherein correction of gyro parameters, i.e. scale factor and zero offset, of the vehicle attitude reference sub-system (15) is effected prior to launch of the vehicle (3) on the basis of repetitive comparisons of attitude data as measured by the platform and vehicle sub-systems (13, 15). The vehicle (3) may comprise a dispenser of a number of munitions (5) each itself incorporating a guidance sub-system (25) incorporating gyros (27), in which case corrections of gyro parameters of the missile guidance sub-system (25) may be effected prior to missile launch on the basis of repetitive comparisons of attitude data as measured by the dispenser and munition sub-systems (15, 25).

Abstract: A housing for a microwave circuit is formed from a base made of metal matrix composite material and walls made of sheet metal. The base and the walls are joined together by diffusion soldering. Some holes to receive feedthroughs are formed at the junction of the base and a wall.

Abstract: An electro-magnet (11) is spatially coupled with respect to a support armature (15) by an operational gap (16) and their relative movement is automatically compensated by controlling a current (14) supplied to the electromagnet (11). The current (14) and hence a magnetic field (F) are controlled by a current controller (13) which incorporates a transfer function and is operated in a feedforward path (19) by a signal (18) from a sensor (17) which detects variations in the gap (16) between the electro-magnet (11) and the support armature (12). The current controller (13) is also operated in a feedback path (22) by a signal (21) from a sensor (20) which detects variations in the flux intensity of the magnetic field (F).

Abstract: A thermal imaging device comprises an array of microbridges(10) disposed on a silicon readout circuit substrate (12). Each microbridge (10) is supported above the substrate (12) by electrodes (14 and 16) so that a cavity (26) is present between the microbridge (10) and the substrate (12). Each microbridge (10) has a collecting area, a region of which is occupied by a ferroelectric active element (20) which converts to received thermal radiation into an electrical response. Radiation which is received by regions of the collecting area not occupied by the active element (20) is converted into heat energy and then transmitted to the active element (20) by conduction.

Abstract: A device for changing the divergence of a beam of microwave radiation comprises a ferrite body having an aperture through which the beam passes. Magnetic wires pass both through the body and across the aperture, or a magnetic coil on either side of the aperture, causes a differential phase delay as the beam passes through the aperture which broadens or narrows the beam.

Abstract: A microwave receiving antenna system (30) is described which is used to determine an originating direction of microwave radiation. The system has a birefringement phase plate (34) which splits radiation incident on it into two components which undergo a differential phase delay as they pass through it. The amount of differential phase delay induced varies with angular position around the phase plate (34) from 0 at an angular position of 0° to &lgr; an angular position of 360°. By determining the differential phase delay (assuming a previously existing relationship) the originating direction of the radiation can be determined.

Abstract: A head up display system 10 comprises an image generator 11 supported and boresighted within a cockpit. The system 10 includes a housing 13 to support the generator 11 and a holographic combiner 14 which is upstandingly supported on top of the housing 13. In operation, the generator 11 forms an image at object surface 17 and a relay lens arrangement 16 receives, collimates and conveys the image along an optical pathway 19 and through an exit pupil 18. A prism 20 and a mirror 21 are arranged along the pathway 19 to fold the pathway 19 from a generally horizontal direction to a generally vertical direction towards the combiner 14.

Abstract: A head tracker system for determining a user's head orientation relative to a datum comprises: a head mounting, preferably a helmet (2), for attachment to the user's head and a sensor system (10,12) for sensing the orientation of the head mounting (2) relative and the datum. A distinguishable marking (26) is provided at a first known point fixed relative to the head mounting or a second known point fixed relative to the datum. At the other known point an optical sensor (18), preferably a video camera, is mounted. The system further comprises processing means (28) for determining when the marking is within the field of view of the optical sensor and the output of the processing means is used to correct for drift in the sensor system or to provide an independent verification that the system is functioning within preselected tolerances.

Abstract: A display arrangement particularly suitable for replacing a conventional CRT in a pilot's helmet mounted display includes a light source having a modulated output which is scanned by a scanner across a screen to produce an image. The image is transferred into the pilot's field of view by relay optics. The scanner and screen are mounted on the pilot's helmet and the light source is remote therefrom.