Abstract: A radar seeker employing a 4-element antenna and amplitude or phase comparison target location. The azimuth (C and D) and elevation (A and B) elements share two channels alternately by means of cycling switches (S1, S2). Sum (31) and difference (29) signals are derived from the two channels and then the difference channel is re-distributed (S4) to dedicated azimuth and elevation channels. The shared channels (G, H) are interchanged cyclically (S3) so that mismatches between them are cancelled out.

Abstract: A target tracking radar system for a guided missile wherein sum and difference signals from a reception antenna are multiplexed at a variable rate into a single channel receiver, the multiplexing rate depending on an alternating reference signal. The output of the receiver is applied to a phase sensitive detector operating in synchronism with the alternating reference signal and whose output is utilised to guide the missile towards the target. The detector output is also integrated and applied to circuit means which produces the reference signal, thereby forming a closed loop. The integrated detector output is also applied to a servo motor which drives the antenna to track the target.

Abstract: A lithium-water reactor for use in a motor, comprises a combustion chamber having means for spraying water onto a charge of lithium so as to cause combustion. The lithium can be provided as separate body or coating on the wall of the combustion chamber and conveniently includes a combustion initiator. The motor can be used in a torpedo propulsion unit, or any other marine application requiring an energy source.

Abstract: In an antenna array of large dimensions, such as might be used for high frequency radar, the antennas 1a, 1b, will be connected by short feeders 2a, 2b, to receivers 3a, 3b, which will consequently be distributed over a considerable distance. Calibration of such an antenna array to compensate for variations in the transfer functions of the receivers will necessitate the same test signal being fed into each element in turn to measure the receiver output, and this could be time consuming and hence reduce the time available for use of the array. To overcome this disadvantage, a loop 5 is connected at various tappings to the feeders 2a, 2b, the respective antennas are disconnected, and sinusoidal tones are injected into the left hand and right hand ends of the loop. The outputs of the receivers are measured, and provide a measure of the transfer functions of the receivers and hence enables discrepancies between them to be corrected.

Abstract: A method of assessing radar pulses in a passive, i.e. receive-only, radar system to distinguish pulses due to a particular target from pulses due to other targets from noise, interference, etc. Received pulses are assessed, without reference to pulse transmission information, in respect of a number of characteristics by comparing each characteristic of a pulse with the mean value of the respective characteristic for pulses previously received. Using a probability process, confidence values for the pulse can be calculated. By combining the confidence values for each characteristic, an overall confidence value is obtained for the pulse so that it can be determined whether it arises from the particular target.

Abstract: A tracking radar system comprising an aerial arrangement having a plurality of outputs, means for deriving from the aerial outputs a sum signal representative of the sum of the aerial outputs and a difference signal representative of the direction of a target relative to the aerial, a receiver for processing said sum and difference signals to produce corresponding intermediate frequency sum and difference signals, means for comparing the intermediate frequency sum signal with the output of an oscillator in a first phase-locked loop and using the resulting signal to control the oscillator frequency so as to cause the oscillator to lock on to the frequency of the intermediate frequency sum signal, a phase-sensitive detector for comparing the intermediate frequency difference signal with the output of the oscillator to produce an output signal representative of the phase difference between the sum and difference signals, and bandwidth alteration means responsive to the sum signal to alter the bandwidth of the fi

Abstract: FMCW radar return signals are converted to i.f. in a front end section, digitised in an A-D converter, and reduced to in-phase and quadrature base band components at a lower sampling rate in a filter section. Returns are compared with a separate reference waveform signal from a generator for each range cell by a multiplier and an accumulate and dump function. The reference waveforms for subsequent range cells are delayed by one sample period. The provision of separate correlation of de-ramping for each range cell enables non-linear sweep wave forms to be employed, whereas the conventional method using a single Fourier Transform for all range cells simultaneously restricts operation to a linear sweep waveform.

Abstract: A missile radome (1) has an acutely pointed profile and includes an antenna array of four elements (A, B) toe'd out around the boresight (5) for an amplitude comparison system. Certain received signals strike the antenna elements (A & B) after grazing the internal radome surface, and after single multiple reflections. The tracking characteristic consequently suffers perturbations. A layer (6) of surface wave absorbent material is provided on the inside of the radome (1) in combination with a mass of radar absorbent material (7) enclosed by this layer. The combination considerably improves the position.

Abstract: A signal carrying structure comprising a planar conductive member having a major surface, a dielectric layer having a substantially constant thickness, and a conductive track. A first major surface of the dielectric layer is in contact with the major surface of the planar conductive member, and the conductive track is in contact with a second major surface of the dielectric layer. The conductive track is spaced from the major surface of the planar conductive member by the dielectric layer. The dielectric layer has a plurality of apertures which extend between the first and second major surfaces thereof in the region between the conductive track and the planar conductive member. The proportion of dielectric material in the dielectric layer is less in this region than in the other regions of the dielectric layer. The structure is used for propagating microwave electromagnetic radiation, and is applicable to strip line, triplate and phased array antenna applications.

Abstract: A data processing apparatus for controlling an equipment by operating control devices (1, 3) of the equipment in dependence on signals produced by sensors (5, 7) wherein the sensor signals are processed in three stages. In the first stage the signals are processed in a processor (11) of high operational speed, i.e. number crunching capabilities, and low decision capability. In the second stage processors (19) of lower operational speed and higher decision capability are used. In the third stage processors (27) of still lower speed but higher decision capability are used. This architecture allows the apparatus to be easily reconfigured for use in a wide variety of different applications.

Abstract: In a television transmitter having separate picture- and sync-modulated r.f. amplification, the sync-modulated r.f. signal is derived from the picture-modulated signal using a modulator controlled by the video sync signal conventionally present in the transmitter. This simplifies the construction of the transmitter, and is particularly applicable to solid-state amplifier transmitters.

Abstract: A high frequency SSB radio transmitter has an envelope amplitude modulator for varying the envelope of an r.f. signal source based on an error signal from envelope detectors detecting the envelope of the input and output waveform. It also has a phase modulator for varying the phase of the input waveform based on differences detected in a second amplitude modulator between the instantaneous phase of the input and output r.f. signal. A signal derived from the error signal controls the second amplitude modulator in a subsidiary feedback loop to maintain the size of the envelopes detected by the detectors the same, in order that a difference amplifier may operate effectively. Rapid discrepancies between the detected envelopes occurring within an envelope can then be corrected by the envelope amplitude modulator.

Abstract: A planar microwave antenna having a resonant back structure (22) constituting a common back plane cavity for an array (20, 27) of resonant slots (21). The back structure (22) comprises a sheet of metal having an arrangement of mechanically pressed projections forming lands (23). The projections extend towards the regions between the slots (21) of the array (20) and are so shaped and positioned that the lands (23) do not intrude into areas of the back plane exposed by the slots (21). The lands (23) provide a rigid support for the slot array (20) and reduce the dimensional tolerance problems encountered in antennas having a single flat back plate. Further, the projections reduce the number of possible degenerate waveguide modes to give an improved antenna performance. The provision of a common back cavity also enables a closer slot spacing than can be achieved when using individual cavities for each pair of slots.

Abstract: A linearity correction circuit for television transmission operates at intermediate frequency to introduce appropriate pre-distortion into the amplitude envelope to compensate for non-linearity in the power amplifier states. An array of parallel current sources (11), each of which is independently adjustable in response to the perceived requirement for pre-distortion over a corresponding amplitude band, to inject a current sufficient to introduce an appropriate differential voltage at the output. The circuit provides for the independent correction of each amplitude band, so that it is capable of operation under microprocessor control in real time.

Abstract: A radar transmitter chain employing injection locked oscillator, e.g., a magnetron, as an output stage. Problems arise with maintaining the injection locking bandwidth centered on the radar source transmit frequency. This alignment is maintained by allowing the magnetron (38) free running frequency to drift, along with its injection locking bandwidth and then to force the radar source frequency (30) to follow the magnetron frequency. A phase difference measurement (44) between the injection signal (35) and the magnetron output signal (37) provides the control for a feedback loop (60) which may control a tunable VCO (48) or selection from a bank of fixed frequency oscillators (78).

Abstract: Direction finding apparatus comprising at least ten antenna channels for connection to respective antennae in use, at least five receiver channels each coupled to at least two different antenna channels constituting a group, and circuitry for receiving and comparing the outputs of the receiver channels to determine the angular location of the signal source; the arrangement being such that in use the antennae of each group of antenna channels have a sufficient angular separation such that only one is capable of detecting the signal source at one time, and the nearest neighboring antennae of each group are coupled to respective different receiver channels different from the receiver channel of that group.

Abstract: When there is relative movement, at a speed above a critical value, between the trailing edge of a body, such as a hydrofoil or aerofoil section, and a fluid, the fluid flow tends to form a pattern of discrete swirling vortices. Vortex shedding at each side of the trailing edge alternately can cause resonance or "singing" of the section. The effect of this phenomenon is reduced by forming contiguous triangular flat-faced notches in the major surfaces of the section, adjacent the trailing edge, but leaving the profile of the leading edge substantially undistrubed. The notches in one major surface are preferably staggered relative to those in the other major surface.

Abstract: A weapon system particularly for an armored vehicle and comprising a main gun turret (3) for use against tanks and other land-based targets, a secondary turret (1) mounted on the main gun turret (3) and carrying one or more rapid-fire machine guns (9), and a millimetric surveillance and tracking radar mounted on the secondary turret, the radar being adapted to control the secondary turret (1) and machine gun (9) to aim and fire directly at an on-coming missile at close range preferably to destroy the missile or damage it to such an extent that any impact does not cause substantial penetration of the vehicle.

Abstract: An exponentially tapered slot (Vivaldi) antenna for producing an end-fire beam. The antenna features a novel balun for coupling with a feed line. The conventional Vivaldi antenna is fed by means of a stripline section (1) underlying the ground plane (5) and lying perpendicular to the axis of the slot line (3). This balun arrangement has an inherent narrow bandwidth. In the proposed antenna arrangement the slot line (14) and the stripline (16) each have a 45.degree. twist centered on a common cross-over point (X.sub.o,Y.sub.o). The stripline (16) is terminated by a short-circuit to the ground plane (12) and the slot line (14) is terminated by an open-circuit in the form of a circular slot (15). The E-plane and H-plane radiation characteristics are similar to those of the conventional Vivaldi antenna, but the arrangement has a broadband capability enabling operation over any 3 to 1 bandwidth in the frequency range 1 to 40 GHz.

Abstract: A cavity-backed dual-slot antenna element for circular polarization having a single probe extending from the end of the feed line for the element and arranged to couple energy into the resonant slots. The probe lies in the plane of the feed line and has the form of an open circle having a circumference of approximately one wavelength at the operative frequency. The probe is constrained to lie within the boundary of the resonant slots as projected onto the plane of the feed line. The arrangement produces a circular polarization having a greater axial-ratio bandwidth than that of conventional antennas using two orthogonal probes or using a single probe feeding a resonant patch. An antenna comprising a flat array of the elements is suitable for use in DBS (Direct Broadcast by Satellite) TV reception. However, the probe itself is not limited to use in slot antennas and it has applications in other antennas or couplers for circular polarization.