Abstract: An extendable/retractable link apparatus 10 defines a fluid passage therethrough and may be connected between two relatively moveable components, e.g. an aircraft ejector seat and the adjacent fixed airframe, so that, when there is relative movement within pre-set limits, there is no significant displacement of fluid and no significant pressure force generated. The apparatus comprises a body 12 defining a fluid inlet/outlet port 16 and slidably receiving a piston 18 having a central bore which defines a fluid inlet/outlet port 24. The fluid passage is defined between said inlet and outlet ports 16 and 24. Relative movement of the piston 18 and the body 12 does not cause significant displacement of the fluid into or out of the fluid passage.

Abstract: In a jamming cancellation system wherein a balanced modulator receives as two inputs thereto: the desired plus jamming signals, and the AM difference frequency produced by the beating of the desired and jamming signals, jamming suppression, in an environment containing two jamming signals, is achieved by peak detecting the output from the AM difference frequency producing means and applying same directly to the receiver video input or upconverting same to the receiver r.f. frequency and applying same to the system receiver.

Abstract: Modified configurations for electrical connectors to ceramic transducers are designed to reduce failure rates due to fatigue during transducer operation. These modifications eliminate or reduce one or both of the problems causing the fatigue, tensile forces acting on electrical wires connected to ceramic electrodes and unreliable solder joints. Star and pin configurations of wire soldered to ceramic transducers control the position of the wires, thus reducing the tensile forces on the wire. Plug connectors use pressure contacts between the ceramics, eliminating the need for solder joints.

Abstract: In a radar system it is necessary to distinguish signals reflected from wanted targets such as aircraft from those reflected from fixed terrain features, known as clutter. The clutter signals can in some cases be significantly stronger than the wanted signals. One method for dealing with land clutter is the use of a high resolution clutter map. The area around the radar is considered to be divided into cells, and an array of background signal estimates is maintained for these cells. Whenever a signal is received by the radar, it is compared with the stored background level for the cell it occupies, and a detection is only reported if the signal exceeds the background by a pre-set threshold. Received signals are also used to modify the stored background levels so that the clutter map adapts to the reflections from clutter which are present over long periods. Clutter maps have so far only been used successfully for radars at fixed locations.

Abstract: One aspect of the invention relates to a laser ranging system.

Abstract: For broadcast transmission of Differential GPS data signals, a vertical array antenna provides broad band omnidirective phase-progressive radiation with elliptical polarization. Four-dipole sub-arrays use diagonally aligned two-piece cut and bend dipoles with isolated conductive frontal strip. With these vertically arrayed sub-arrays, lower and upper sub-arrays are excited at 70 percent amplitude and respective plus and minus 90 degree phase rotation relative to middle sub-array, for optimized performance with low elevation lobing. Divided transmission line operation provided by the frontal strip of appropriate length achieves double-tuned dipole performance with very low VSWR over the operating band.

Abstract: In a sense amplifier for reading out memory cells of a memory comprising a set of P-FETs and N-FETs, complementary input signals received from the memory cell being read out are applied to input junctions connected to gates of N-FETs. The input junctions are charged to 0.8 volts by a precharging circuit comprising P-FETs connecting the input junctions to ground and an N-FET shunting the input junctions together. The P-FETs and N-FETs of the precharging circuit are rendered conductive between memory cells readouts to precharge the input junctions and are rendered nonconducting during memory cell readouts. A second precharging circuit precharges an output junction of the sense amplifier circuit. The output junction is connected to an output amplification stage including a CMOS circuit. Because of the low equalization voltage to which the input junctions are precharged, the time to precharge the input junctions is dramatically reduced and a reduction in the memory access time is achieved.

Abstract: A combiner assembly 20 has an optical combiner 21 mounted to a housing 22 which is further arranged for mounting to a roof structure of a flight deck of an aircraft. The combiner 21 is mounted within a frame 23 which is mounted to the housing 22. The frame 23 has first pivot point 24 which is attached to a first arm 25 which is also attached to the housing 22 at a second pivot point 26 located at a position remote from the first pivot point 24. First arm 25 is arranged to allow the combiner 21 to rotate around the housing 22 between a deployed position and a stowed position. A second arm 27 is pivotally connected to the frame 22 at a third pivot point 28, at a position spaced from the first pivot point 24, and to the housing 22 at a fourth pivot point 29, located at a position remote from the third pivot point 28 and at a position spaced from the second pivot point 26.

Abstract: A method is provided for correcting errors in position derived from an inertial measurement unit (IMU), by performing a first zero velocity update at a time when the IMU is at rest, recording the time and position of the IMU at a subsequent start of a period of interest after the first zero velocity update, recording the time and position of the IMU at the end of the period of interest, performing a second zero velocity update at the end of the period of interest with the IMU at rest, and then recording a velocity indicated from the IMU, and deriving an accumulated error in position from the recorded data, by approximating errors in velocity by a function of time with a parameter determined from the recorded indicated velocity, and integrating the function over the period of interest to determine the accumulated error in position during the period of interest.

Abstract: An infrared countermeasures system is provided by ganging a plurality of modulators each of which modulates the output of a radiant source to generate at least one collimated beam of radiation. The modulators are so disposed with respect to each other that the beams generated the reby are staggered in angular phase. When the modulators are rotated together they will provide at a point in space remote therefrom a signal comprising a burst of pulses followed by a dead time when no signal is present.

Abstract: The slat 16 is mounted to extend and retract relative to the aerofoil 10 and a data line 28 supported on a mounting cable 20 extends between the slat 16 and the aerofoil 10. The data line 28 is arranged to wrap around the leading edge 12 of the aerofoil 10 in the fully retracted position of the slat 16 and to extend substantially along a straight line between the aerofoil 10 and the slat 16 when the slat is in its fully extended position.

Abstract: The signal to noise ratio in non-destructive testing or evaluation of a sample (1) by in phase stepped optical inspection systems such as the optical shearography system using a shearing interferometer involves production of correlated speckle images successively stepped in phase by illuminating with coherent radiation a sample in an unstressed state, illuminating the sample with coherent radiation, stressing it incrementally at predetermined stress increments, and generating and capturing correlated speckle images successively stepped in phase of the incrementally stressed sample at the predetermined stress increments, using the phase stepped speckle images of the unstressed and incrementally stressed sample to calculate the phase before and after stressing and differencing the images to extract the incremental phase change, inspecting the magnitude and sign of each incremental phase change and if the phase difference between successive measurements increases by more than &pgr; subtracting 2 &pgr; from the m

Abstract: A single event upset hardened memory cell to be utilized in static random access memories is disclosed. The single event upset hardened memory cell includes a first set of cross-coupled transistors, a second set of cross-coupled transistors, and a set of isolation transistors. The set of isolation transistors is coupled to the first set of cross-coupled transistors such that two inversion paths are formed between the cross-coupled transistors and the isolation transistors.

Abstract: An angular rate sensor or gyro includes a ring-like resonator (1) mounted by support beams (2) extending from the inner periphery of the ring (1) to a boss (4) on a base (3). The support beams (2) are flexible and allow the resonator (1) to vibrate in response to an electrostatic drive (6, 8) in a substantially undamped oscillation mode to permit the resonator to move relative to the support in response to turning rate. The support beams (2) and resonator (1) are made from crystalline silicon. Electrostatic sensors (7, 9) are provided for sensing movement of the resonator (1). The drive (6, 8) and sensors (7, 9) have plate-like elements made from crystalline silicon having surfaces located substantially normal to the plane of the resonator (1) at a spacing from the adjacent outer periphery of the resonator (1).

Abstract: A multiplexor having a single event upset (SEU) hardened data keeper circuit is disclosed. The multiplexor includes a precharge transistor, an isolation transistor, an invertor, and an SEU immune storage cell. Both the gate of the precharge transistor and the gate of the isolation transistor are connected to a clock signal. The SEU immune storage cell has a first access node and a second access node. The first access node is complementary to the second access node. The first access node is connected to the precharge transistor and the second access node is connected to the isolation transistor. The invertor is coupled between the precharge transistor and the isolation transistor.

Abstract: An aircraft undercarriage mechanism 20 comprising a first lock member 22 mounted on the undercarriage 14, the first lock member being engageable with a second lock member 24 mounted on a wing 10 of the aircraft. The first lock member 22 comprises a pivotable arm 26 which carries a roller 36. The roller 36 is rotatable and slidable on the arm 26 and is engageable with a catch 48 on the second lock member 24. The provision of the pivotable arm 26 and slidable roller 36 permits relative movement between the lock members 22, 24 when the undercarriage 14 is retracted with the lock members interengaged to minimise transmission of forces created by wing deflection from one lock member to the other.

Abstract: A pulse generator comprises a pulse forming line having a helical core winding surrounded by an outer winding, and a transformer having primary and secondary windings. The secondary winding is arranged about the core winding and the primary winding is arranged to co-act with the secondary winding such that the primary winding energizes the secondary winding when a suitable voltage is applied to the primary winding by a charging circuit connected to either end of the winding. The secondary winding through transformer action charges the pulse forming line. The pulse forming line has a load and a switch connected between the core winding and the outer winding. At the appropriate time the switch is closed such that energy stored in the line is discharged to the load as a pulse.

Abstract: A digital control system for a vibrating structure gyroscope having a vibrating structure (3), at least a primary drive (4) for putting and maintaining the vibrating structure (3) in vibratory resonance, and at least a primary pickoff (2) for detecting vibration of the vibrating structure (3), includes a digital processing unit (22) for receiving output signals from the pickoff (2) for processing the received signals and for passing them to the primary drive (4) via digital to analogue converters (20). The system includes sampling at selected intervals of time the output signals before passage to the digital processing unit (22) and a variable frequency oscillator (23) connected to and under the control of the digital processing unit (22) for controlling the sampling intervals.

Abstract: A method of measuring load applied to a pin bearing and a pin bearing arrangement for use on an aircraft landing gear are provided. Relieving one or more of two adjacent bushes (4, 5, 6) bearing on a pin (1) of the pin bearing to create a zone of constant shear stress enables measurement of load and avoids cutting the pin.

Abstract: An enhanced single event upset immune CMOS latch circuit is formed of a first and a second cross-coupled invertor having isolation transistors in the path coupling the drains of the transistors in the first invertor.