Abstract: A generally planar antenna formed in strip transmission line comprises a two-dimensional array of antenna elements (11) coupled to a plurality of secondary feeders (10) each coupled at at least one end to a primary feeder (4). In order that the level of coupling between the primary feeder (4) and each secondary feeder (10) should be well-defined and, when there is a large number of elements, suitably low, the coupling means therebetween are shielded and non-conductive, suitably a directional coupler (17). To provide the shielding, the primary feeder (4) and coupling means may be formed in double-ground-plane line. In an arrangement suitable for an antenna wherein power may be supplied to either end of the primary feeder (4) to give radiation patterns having single main lobes with different angular orientations, for example for a Doppler navigation system, one port of each directional coupler (17) may have an open-circuit reflective termination.

Abstract: A tracked vehicle of narrow aspect suitable for unmanned operation both in hazardous environments and on routes normally accessible only to pedestrians, comprises two identical vehicle units (1, 2) each having an independently drivable, full width track (3), the units being interconnected in tandem configuration by an articulation mechanism (9) permitting relative rotation about a yaw axis (Y). In one aspect the articulation mechanism is passive, being arranged with an offset yaw axis, thereby permitting steering by application of a velocity differential to the two tracks. In a second aspect the articulation mechanism is active being powered by an actuator (94) to provide articulation steering. The articulated units may also be secured in parallel configuration for conventional skid-steering operation.

Abstract: A broadband balun, suitable for feeding a spiral antenna, has a balanced port (20) comprising two adjacent strip conductors (16,17; 36,37) which are coupled to the unbalanced port (6) by respective paths of the same effective electrical lengths. The paths comprise respective strip transmission lines (9,10) having a common ground conductor (3; 44) which terminates in a transition to the balanced line (19), and further comprise slot line means (11; 21) and strip transmission line-to-slot line coupling means (14,15) so arranged as in operation to provide in the two strip conductors (16,17; 36,37) from an RF signal at the unbalanced port (6) signals of mutually opposite phases with respect to the common ground conductor (3; 44).

Abstract: A coplanar patch antenna is formed, e.g as a printed circuit, on a dielectric support (1) by a metal patch (2) spaced from a coplanar ground plane (3) by a peripheral slot (4), and in the improvement is series fed by means of a slot line (5). The slot (4) can be made resonant by having a periphery of one wavelength or an odd multiple thereof, and a second slot line (7) can be fed into the slot (4) at a distance of one or an odd multiple of a quarter wavelength from the slot line (5) to provide an independent feed. The arrangement presents a feedpoint impedance of about 50 ohms at the ports (6,8) instead of about 400 ohms in prior arrangements.Balancing loads or 180 degree hybrid feeds to other quadrature ports (11,12) can be used to correct beam asymmetry due to the slot line feeders (5 and 7).

Abstract: This invention relates to a skeletal implant designed to provide a structure which bone can fill so as to biologically anchor the implant in position. A series of cutting edges are aligned on at least part of the surface and directed in a direction of relative movement between implant and bone. Bone removed by these edges is urged into a series of interconnecting spaces beneath the surface. Preferably a porous surface and the cutting edges are provided by perforated microcontoured sheet material. The three dimensional porosity formed by the perforations and contours results in bone debris impacted into the voids particularly at the time of implantation which will subsequently become integral with surrounding bone.

Abstract: A tracked vehicle with a rearwardly extending ram (13) and an energizing means (14) for the ram, for assisting the vehicle in mounting precipitous objects. A preferred vehicle configuration uses only three, track direction changing rollers (6, 7, 8) so as to locate the center of gravity (16) of the vehicle as far forward as possible.

Abstract: A wide track vehicle with improved skid steering by having a chassis (1) supported upon two independently drivable tracks (2) by side support wheels (3) engaged with each track adjacent the outer edges only. Downwardly projecting rubbing strips (11, 12, 13) are attached to the underside of the chassis (1) to engage slideably with each track only when the track is upwardly deflected by uneven terrain. The tracks (2) each rotate upon a plurality of full width direction-changing rollers attached to the chassis and each having a rolling surface which is provided with mud-cutting, helical ridges (18).

Abstract: A waveguide/microstrip mode transducer operable over a broad frequency range comprises a dielectric substrate (3) extending along an E-plane of a waveguide and having a conductive layer on each major surface, the two layers having three successive pairs of portions. A first pair (10, 11) form a microstrip line, a second pair (12, 13) form a balanced transmission line, and a third pair (14, 15) couple the portions (14, 15) of the balanced line to opposite walls (6, 7) of the waveguide.

Abstract: A microwave detector arrangement operable over a broad range of frequencies including the series resonant frequency of a detector diode (9) for detecting microwave energy in a transmission line of characteristic impedance Z.sub.o, suitably a coplanar line. A first portion of line, including a strip conductor (3), is terminated by a network, including a capacitance (4) and a first resistance (5) in series with one another and with the parallel combination of a second resistance (6) and the diode (9). The capacitance (4) provides D.C. isolation, while the detector output is taken across a capacitance (10) in series with the diode (9). The first and second resistances (5,6) are respectively 2Z.sub.o /3 and 3Z.sub.o /2, so that the terminating impedance provides a reasonable match to the line over a broad frequency range.

Abstract: A transmission system is disclosed in which a stepped-ratio system having a conventional gearbox is combined with a short range, smoothly adjustable-ratio system to give a continuous range of transmission ratios through and beyond the fixed ratio steps of the gearbox.An arrangement is described in which all the variable parameters of the system are commanded by an electrically operated control system in response to a single demand signal from an operator.

Abstract: The present invention relates to a process for expanding thermoplastic polymer compositions, notably those containing polymers having processing temperatures in excess of 200.degree. C. and/or containing an ingredient which is susceptible to ammonia, characterized in that as the blowing agent certain carbonates (notably zinc carbonate) are used. Preferably a nucleating agent and a weak acid are present to aid cell formation.The invention also includes expandable polymer compositions and blowing agent formulations containing the carbonates.