GB2276436A

GB2276436A - Sensor arrangement for munition

Info

Publication number: GB2276436A
Application number: GB8606156A
Authority: GB
Inventors: Gunther Trummer
Original assignee: Diehl GmbH and Co
Current assignee: Diehl Verwaltungs Stiftung
Priority date: 1985-05-03
Filing date: 1986-03-12
Publication date: 1994-09-28
Anticipated expiration: 2006-03-12
Also published as: FR2699268A1; DE3515861C1; GB2276436B; GB8606156D0

Abstract

In a sensor arrangement (10) for articles of munition e.g. seeker fuze submunitions (1) having a hollow-charge insert (4) in front of a combat charge (6), a waveguide (17) extends forwards from a microwave frequency part (18) and terminates at or adjacent the centre of the reflecting front face (15) of the insert (4). The surface (15) is caused, at a distance of about one-quarter of the wave length of linearly polarised radiation energy, with a polarisation deflection grid (47), in front of which, approximately at half the focal point distance (53) and thus approximately in the plane of the insert edge, a disc-shaped polarisation filter (42) is held, the polarisation direction of which corresponds with that at the feed, but is deviated through 45{ relative to the polarisation direction of the deflection grid (47). <IMAGE>

Description

A SENSOR ARRANGEMENT FOR MUNITION The invention relates to a sensor arrangement in accordance with the definition of the species of claim 1, preferably designed for articles of seeker-fuze submunition.

A sensor arrangement of the kind in accordance with the species is known from FR-PS 12 93 794, from DE-OS 32 37 483 or from EP-OS 131 744. More especially with reference to the design for articles of armour-piercing munition with an insert transformed by the explosive of the combat charge into a projectile that is to be fired, the previously known sensor arrangements have the considerable disadvantage of influencing detrimentally the centre, very sensitive for the transformation kinetics and the flight dynamics of the projectile, of the insert, with respect to the desired penetration effect of the projectile even over a fairly great combat distance; because the sensor arrangement, in matters relating to apparatus, stresses a comparatively large region around the vertex of the insert or respectively because this apex of the insert has to be penetrated by a component part which protrudes to a relatively great extent. From this it namely results that a comparatively large-calibre insert is not transformed into the compact, flow-dynamically favourably shaped projectile which is necessary for the effect in the target, but sunders for example in flight and thereby does not have the desired effect in the target. It is further detrimental to this effect, that is to be striven after in munitiontechnology respects, if, to influence the antenna characteristic of the sensor arrangement, at a fairly great distance in front of the insert massive construction elements such as holders for a sub-reflector are arranged, which have to be pierced by the projectile.

One could indeed blast off such projecting (translator's note: "vorbauend" literally means "built in front") construction elements immediately prior to the onset of the explosive transformation of the insert; which, however, raises considerable additional constructional and control-technology problems respecting a functionally-reliable article of munition that can be produced economically as a mass-produced product. Added to which, in order to reduce effective overall length of a number of articles of submunition that are to be delivered in an axially stacked manner by means of a carrier, widely protruding components dictate that the projecting construction parts should engage coaxially into the rear side of the article of munition situated in front thereof; with the result that, after ejection from the carrier, the radial movement of separation of the articles of submunition from one another can be hindered and can lead to damage to the projecting construction parts. A disadjustment of antenna parts and thus the inability of the sensor arrangement to function can then result therefrom.

In recognition of these factors, the problem underlying the invention is to develop a sensor arrangement in accordance with the species in such a way that it yields the desired beam-parallel antenna characteristic without structural parts which protrude far from the apex of the insert or which project beyond the front of the structure of the actual article of munition and which are solely necessary for the antenna characteristic.

In the case of a sensor arrangement of the kind in accordance with the species, this problem is essentially solved in that it is developed in accordance with the characterising part of claim 1.

In the case of this solution, use is made of the fact that also linearly-polarised radiation is suitable for the evaluation of reflected energy. The opening of an insert designed as a main reflector is now covered by a disc-shaped polarisation filter which serves as a subreflector and which co-operates with a polarisation deflecting grid on the reflecting surface of the insert in such a way that the radiation energy that is to be emitted has only after reflection at the insert the polarisation direction for a passage through the filter.

For this solution, the radiation opening of the wave guide connected to the rearward high-frequency part does not need (or at all events if need be minimally) to pass in the region of the apex through the insert, so that to this extent practically all negative influences on the optimum explosive transformation thereof into the projectile that is to be fired are avoided. The filter held in front of the insert can be a thin plastics disc, which can be pierced without any problem by the projectile, with thin, embedded or applied electrical conductors, in other words it practically no longer impairs the effect of the projectile in the target. This filter is completely flat if it is arranged at half the effective focal point distance in front of the reflecting front surface of the insert; in which respect this effective focal point distance depends upon the geometry of the arching of the polarisation deflecting grid in comparison with the geometry of the insert front surface situated therebehind. Even if the filter does not lie exactly at the location of half the focal point distance, because it is intended, through slight arching, to compensate for non-linearities upon the beam reflection, still no substantial disturbing superstructure of the article of munition in its effective direction thereby occurs. An arching-out of the filter contrary to the direction of the effective direction of the munition and antenna yields above all also the constructional advantage of greater stability against an oppositelydirected high firing acceleration of the munition, for example in a carrier projectile. If such an arching-in (or arching-out) towards the plane of separation of the article of munition is foam-filled to the plane, there results therefrom an influencing of the geometric behaviour of the electromagnetic energy passing through, in other words of the antenna diagram.

The hollow frequency part itself is expediently embedded directly into the explosive of the combat charge behind the insert and so configurated that, in collaboration with the geometry of the surrounding structure walling of the article of munition, it acts as detonation wave deflector for optimum transformation of the insert into the projectile that is to be fired.

Additional alternatives and further developments as well as further features and advantages of the invention will become apparent from the further claims and from the following description of a preferred exemplified embodiment regarding the solution in accordance with the invention which is sketched in the drawings, along with a restriction to that which is essential, in a highly abstracted manner and not quite true to scale.

FIGURE 1 shows a sensor arrangement in the case of target-seeking munition, in axial longitudinal section transversely to the longitudinal extent of the conductors in the polarisation filter; FIGURE 2 shows the article of munition in accordance with FIGURE 1 in front view, towards its polarisation filter; and FIGURE 3 shows a vector diagram to explain the polarisation influence in the case of the consecutive illumination of the polarisation filter and of the polarisation deflecting grid.

In the case of the article of munition 1 sketched in FIG. 1 in longitudinal section with broken-away representation it is a matter of so-called seeker-fuze submunition. It consists substantially of a hollow cylinder 2 which is closed off in the effective direction 3 by an insert 4 made of plastically deformable material.

Enclosed between the insert 4 and a rearward tamping wall 5 is the explosive of the combat charge 6. Its fuze 7, dimensioned for example as a booster (translator's note: "Ubertragungs" can also mean "primer") charge, is arranged in the longitudinal axis 8, coinciding with the effective direction 3, of the hollow cylinder 2 in the rearward wall 5. It is controlled from an electronic circuit (not taken into consideration in the drawing) situated behind the wall 5 when the sensor arrangement 10 in the effective direction 3 has acquired a target object, to be combatted, as such.

Basically the frequency range of the radiation energy which is radiated from the sensor arrangement 10 and after reflection in the target area is picked up again and evaluated is arbitrary. In the interests of high resolution capability and small-size transmission and reception electronics despite only limitedly available aperture installation space for the sensor arrangement 10, preferably electromagnetic radiation energy in the millimetre-wave spectral region is used, which (by reason of appropriate design of the highfrequency part 18 designed as transmitter and receiver) is linearly polarised. The emission and reception of radiation energy is effected by means of the radiation opening 13 of a wave guide 17 connected to the highfrequency part 18. This (translator's note: meaning the "wave guide") extends from the high-frequency part 18, embedded into the combat charge 6 and designed in its configuration as a detonation-wave deflector, along the axis 8 right into the vicinity of the apex 41 of the parabolically curved insert 4, in or close to which the wave guide 17 ends. The opening angle of the funnelshaped radiation opening 13 determines the radiation angle of the radiation energy towards a polarisation filter 42 which acts to a certain extent as a subreflector and which is held in front of the insert 4 in the hollow cylinder 2. The angle of the opening 13 emerges, in the specific case, through the geometric factors of the arrangement of the polarisation filter 42 with respect to the focal point of the antenna characteristic 12 in front of the insert 4 acting as a hollow mirror. In order to be able to operate the sensor arrangement 10 not only actively (as a radar set), but also to be able to use it effectively in passive operation (as a radiometer), namely more especially a large dynamics range is to be striven after, in other words a great difference between minimum picked-up radiation power over maximum distance and maximum radiation power with minimum distance. The dynamics range can be enlarged by a good minor lobe damping of the antenna characteristic 12, since then less radiation temperature of the cltter from the surroundings of an acquired target object is also measured. The minor lobe damping is 'inter alia' impressed by the size of this shaded partial region inside the transverse extend of the antenna characteristic 12, for example as a result of the arrangement of a centrally shading Cassegrain subreflector.

This central shading in front of the hollow-mirror main reflector (in the form of the insert 4) is, in the case of the present invention, practically avoided, in any event reduced to a minimum, since only just the front end of the wave guide 17 (so-called feed) shades; the diameter thereof anyway becomes minimum, since it is, in accordance with the microwave antenna theory, directly proportional to the wave length and inversely proportional to the opening angle of the feed irridiation (translator's note: "Einstrahlung" can also mean "incident radiation") waves 45, with large opening angle with short-size distance between main reflector (insert 4) and sub-reflector (here in the form of the polar filter 42).

The polarisation filter 42 has a large number of linear conductors 43, the mutual spacing 44 of which lies for example in the order of magnitude of 10% of the wave length of the radiation energy that is to be evaluated for the target acquisition. The diameter of the conductors 43 can, upon use of etching techniques, by all means lie in the order of magnitude of 100 /um; in any event it is to be selected small as compared with the spacing 44.

For the exemplified embodiment sketched in the drawings it is assumed that the high-frequency part 18, by virtue of its internal structure and its orientation inside the hollow cylinder 2, radiates by way of the wave guide 17 horizontally linearly-polarised radiation energy through the opening 13. If the conductors 43 contained in the polarisation filter 42 likewise extend horizontally (in other words transversely to the plane of representation of Fig. 1), the filter 42 acts as a reflector for the wave 45 radiated in, which is thus deflected into a reflecting wave 46 with similarly linear horizontal polarisation.

The front surface 15, pointing in the effective direction 3, of the insert 4 carries a polarisation deflection grid 47. This has, like the polarisation filter 42, elongate conductors 43 at a mutual spacing 44 in the order of magnitude of about 10% of the wave length of the radiation energy, with on the contrary small transverse dimensions of the conductors 43. The conductors 43 of the polarisation deflection grid 47 extend, however so that - related to the projection into the plane of the polarisation filter 42 (see the front view in accordance with Fig. 2) - they do indeed appear linear, but swung in that filter plane by 45" around the central axis 8.

The wave 46 reflected without change in polarisation by the polarisation filter 42 experiences, upon striking against the deflection grid 47 inclined by 45" thereagainst, the vectorial decomposition, shown symbolically in Fig. 3, into a reflected portion 48 swung about 45" and a portion 49 passing through the grid 47.

This portion 49 passing through (through the grid 47 orientated transversly hereto) passes as far as onto the metallic front surface 15 - in other words reflecting radiation energy of arbitrary polarisation without change in polarisation - of the insert 4. If the effective distance from the grid conductor 43 to the reflector surface 15 amounts to precisely a quarter of the wave length of the portion 49 passing through, then, relative to this portion 49, the reflected wave 51 is dephased through precisely 1800.

From the vectorial addition thereof with the portion 48 previously reflected at the grid 47 there emerges a radiated wave 52 which (see Fig. 3) is no longer in the initial orientation (horizontal), but is orientated transversely thereto. This thus vertically polarised departure wave 52 can therefore, contrary to the factors for the incident-radiation wve 45, pass unhindered through the horizontally orientated conductors 43 and thus the polarisation filter 42 (parallel to the effective direction 3 of the article of munition 1 and thus of its sensor arrangement 10).

As a whole the arrangement consisting of polarisation filter 42 in front of the insert 4 acting as reflector and carrying a polarisation deflection grid 47 thus yields, taking into account the change in polarisation, the beam geometry similar to a Cassegrain antenna arrangement with the advantage of the good parallel-bunching and minor lobe damping by reason of beam-geometrically large effective aperture; but now with slight axial overall length as a result of illumination of a sub-reflector, designed as a polarisation filter 42, at a relatively small spacing in front of a main reflector, as which the front surface 15 of the parabolic insert 4 serves. In the ideal case, the polarisation filter 42 is arranged as a flat disc at a distance in front of the apex 41 of the insert front surface 15 which lies exactly at half the focal point distance 53 of the parabolic surface 15. Thus, despite optimally bunched radiation course of the departure waves 52, a flat front side 54 of the article of munition 1 is achieved; with the result that an axial stack of several such articles of sub-munition 1-1, upon jetissoning from a carrier (not shown in the drawing), can be separated from one another without any problem by aerodynamic aids, without (by reason of parts, protruding for instance beyond the front side 54, with axial engagement over the jointing plane 55 between two articles of submunition 1-1 lying in front of one another ) the sensor arrangement being subjected, upon the scattering out of the initially common submunition longitudinal axis 8, to any risks of damage, or even the desirable kinematics of the separation of the initially axially packed articles of submunition 1-1 being able top be impaired.

For the mechanical construction of the polarisation filter 42 or respectively of the polarisation deflection grid 47, thin wires can be cast or foamed into plastics materials which are known and proven as materials for radomes in radar technology because they combine high mechanical stability with slight dielectric losses. For a radome, such materials are on the market for example as "Teflon" or "Nuryl"; suitable for foaming-out (translator's note: "Ausschaumung" might also be intended to mean "foam-filling") the space between the front surface 15 and the grid conductors 43 are commercially available polyethylene or "Polystyrene".

The conductors 43 can, however, also be applied to such carrier materials and be mechanically fixed for example by melting-in or bonding; or they are printed-on or vaporised-on as narrow conductive coatings, or respectively are etched from conductive facings.

In practice, the idealised conditions in accordance with Fig. 1/Fig. 3 are only approximately present. The reason for this is more especially that, by reason of the geometric factors between the conductors 43 of the polarisation deflection grid 47 and the reflector surface 15, not necessarily over the entire front surface 15 of the insert does there take place at all times exactly the phase rotation for the transition of the portion 49 into the wave 51 phase-shifted through 180 ; especially since also each of the illuminated conductors 43 of the filter 42 or respectively of the grid 47 again acts as a radially radiating cylindrical primary radiator without preferential orientation. In this respect, these effects are superimposed on one another, so that actually considerable components of the linearly polarised incident-radiation wave 45 pass as a departure wave 52, linearly polarised transversely thereto, through the polarisation filter 42.

For the rest, the influence caused by the non-ideal radiation factors can largely be compensated for by an empirically determinable variation of the beam geometry over the insert front surface 15. Thus, provision can be made for enlarging the spacing of the grid conductors 43 with regard to the reflector surface 15 with the displacement of the apex 41 towards the edge, in other words designing the grid curvature more strongly than in the case of the parabolic course of the surface 15. A still more favourable radiation power emerges if the grid 47 and the reflector surface 15 do indeed extend parallel, in other words have throughout the same curvatures; but the filter 47 designed as a flat disc is arranged advanced somewhat in the effective direction in front of half the focal point distance 53.

A further compensation possibility consists in arranging the polarisation filter 42 contrary to the idealised conditions in accordance with Fig. 1 not as a flat disc approximately at half the effective focal point distance 53, but weakly convexly arched at a somewhat greater distance, in front of the apex 41. In order, in the first-mentioned case, again to achieve an engagementfree plane of separation 55 between articles of submunition 1-1 situated axially in front of one another, then possibly the front edges 56 thereof would have to be drawn forwards slightly (not taken into account in the drawing). A correspondingly parabolically arched-out polarisation filter 42 then also has the advantage of high acceleration strength, contrary to this arching-out.

Claims

Patent Claims

1. A sensor arrangement (10) for articles of munition (1) having a hollow-charge insert (4) in front of a combat charge (6), in which a feed line for radiation energy to be radiated or respectively received radiation energy extends, characterised in that a radiation opening (13) for linearly-polarised radiation energy lies in the immediate vicinity of the apex (41) of the parabolically shaped front surface (15) of the insert (4), which is covered at a distance of about one-quarter of the length of the waves (45) of this radiation energy with a polarisation deflection grid (47), and in that arranged in front of the insert (4) is a polarisation filter (42) which is rotated through 45" relative to the orientation of the deflection grid (47) and the orientation of which is parallel to the polarisation of the radiation energy of the incident-radiation waves (45).

2. A sensor arrangement as claimed in Claim 1, characterised in that the deflection grid (47) and the filter (42) in each case have elongate conductors (43) at the mutual spacing (44) of about 10% of the wave length of the electromagnetic radiation energy in the microwave spectral region, in which respect the width of the conductors (43) is small in relation to this spacing (44).

3. A sensor arrangement as claimed in Claim 2, characterised in that the conductors (43) are embedded into a dielectrically low-loss carrier material.

4. A sensor arrangement as claimed in Claim 2, characterised in that the conductors (43) are fashioned on a dielectrically low-loss carrier material.

5. A sensor arrangement as claimed in one of the preceding claims, characterised in that the filter (42) is designed as a flat disc above the chord of the insert (4).

6. A sensor arrangement as claimed in claim 5, characterised in that the disc is arranged at half the focal point distance (53) of the parabolic surface (15) and the grid (47) has a greater curvature than the surface (15).

7. A sensor arrangement as claimed in Claim 5, characterised in that the disc is arranged offset in the effective direction (3) out of half the focal point distance of the surface (15) and the grid (47) has the same curvature as the surface (15).

8. A sensor arrangement as claimed in one of claims 1 to 4, characterised in that the filter (42) is arched.

9. A sensor arrangement as claimed in one of the preceding claims, characterised in that a wave guide (17) extends along the axis (18), extending through the apex (41) of the insert (4), between the insert (4) and a high-frequency part (18) which is embedded into the combat charge (6) and is configurated as a detonationwave deflection.

Amendments to the claims have been filed as follows 1. A sensor arrangement, for an article of munition having a hollow-charge insert in front of a combat charge, wherein a wave-guide for linearly polarised electro-magnetic microwave radiation extends forwards from a microwave frequency part to terminate at a radiation opening, in or adjacent to the centre of a parabolically shaped radiation-reflective concave front surface of the insert, which radiation opening is arranged to receive or emit radiation in a predetermined plane of polarisation; .wherein a polarisation deflection grid, comprising conductors which extend at an angle of 45C to said predetermined plane, is disposed in front of the front surface, said grid and front surface being separated by a distance of about one-quarter of the wavelength of the microwave radiation so that radiation polarised in said plane incident upon said grid and front surface becomes substantially polarised in a plane transverse to said predetermined plane; and wherein a polarisation filter is disposed in front of the polarisation deflection grid and comprises conductors which extend parallel to said predetermined plane to reflect radiation polarised in said predetermined plane and to pass radiation polarised in said transverse plane.

2. A sensor arrangement as claimed in Claim 1, wherein in each of the deflection grid and the filter, the conductors are disposed at a mutual spacing of about 10% of said wave-length; and wherein the width of each conductors is small in relation to this spacing.

3. A sensor arrangement as claimed in Claim 2, wherein the conductors are embedded into a dielectrically lowloss carrier material.

4. A sensor arrangement as claimed in Claim 2, wherein the conductors are provided on a dielectrically low-loss carrier material.

5. A sensor arrangement as claimed in any one of the preceding claims, wherein the filter is of flat disc form.

6. A sensor arrangement as claimed in claim 5, wherein the filter is arranged at half the focal point distance of the reflector front surface, and the grid has an aberration reducing lesser radius of curvature than the surface.

7. A sensor arrangement as claimed in Claim 5, wherein the disc is arranged offset in the effective direction from half the focal point distance of the reflective front surface, and the grid has the same curvature as said surface.

8. A sensor arrangement as claimed in any one of claims 1 to 4, wherein the filter is arched.

9. A sensor arrangement as claimed in one of the preceding claims, wherein the wave guide extends through the centre of the insert and along an axis of the arrangement between the insert and the microwave paL, frequency part which part is-rreceiver/transmitter part, is embedded in the combat charge and is configurated to serve as a detonation-wave deflector.

10. A sensor arrangement substantially as hereinbefore described with reference to the accompanying drawings.