Communications: directive radio wave systems and devices (e.g. – Return signal controls external device – Gun
Patent
1995-07-17
1996-11-12
Sotomayor, John B.
Communications: directive radio wave systems and devices (e.g.,
Return signal controls external device
Gun
342 75, 342153, G01S 1372
Patent
active
055744613
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the invention
The invention relates to a radar apparatus provided with an antenna for connecting to a substantially non-recoiling part of a gun barrel, of a gun equipped with servo motors, with a radar transmission device coupled to the antenna, a radar reception device coupled to the antenna, a radar data processor and servo control means, for controlling the servo motors such that in a first operational mode the gun with the antenna mounted on it is fit for automatically tracking a target.
2. Discussion of the Background
A radar apparatus of this kind is known from EP-A-0.198.964. In this known radar apparatus the gun center line and the line of sight of the antenna is fixed. The disadvantage is that a possible lead angle for the gun cannot be chosen dependent upon a set of target parameters, well known in the art. This limits the application of the known apparatus to situations where the distance between the target and the gun s small or the target is nonmoving.
SUMMARY OF THE INVENTION
The radar apparatus according to the invention eliminates this disadvantage and is characterized in that the antenna is a Cassegrain antenna provided with a flat mirror controlled with actuators, for generating in a second operational mode an angular offset between a gun center line and a line of sight of the antenna. A Cassegrain antenna having a flat mirror is known per se from U.S. Pat. No. 4,450,451, as part of a projectile provided with radar means. A possible disadvantage of mounting the Cassegrain antenna to the gun is that, when firing a salvo, vibrations from the gun may be propagated to the antenna. This may cause a rotational vibration around the center of gravity of the Cassegrain antenna and consequently adversely affect the accuracy of the target position measurement. The measurement of the error angles of a target using a monopulse or a conical scan radar reception device is known to be susceptible to this. An additional favourable embodiment of the radar apparatus according to the invention is therefore characterized in that the Cassegrain antenna is provided with rotation sensors for the detection of rotational vibrations induced by gun fire and in that the dataprocessor is capable of generating control signals on the basis of the rotation sensors output signals for controlling the actuators such that the line of sight of the Cassegrain antenna is at least substantially independent of the rotational vibrations. Besides causing a rotation of the Cassegrain antenna, vibrations may also bring about a translation in the direction of the line of sight. This translation will cause stationary objects to have an apparent Doppler velocity and may cause an apparent change in the Doppler velocity of a target. Both effects may degrade the performance of the radar apparatus that is always of the Doppler radar type in the application as described here. This especially holds true if the radar apparatus operates at relatively short wavelengths. This is also true for the radar apparatus described here. Only for short wavelengths the parabolic reflector will be so small that mounting to a gun becomes attractive. An other favourable embodiment is therefore characterized in that the Cassegrain antenna is provided with translation sensors for the detection of gunfire-induced, translational vibrations in a direction of the line of sight and in that the dataprocessor is capable of generating control signals on the basis of translation sensor output signals for controlling the actuators such that for the transmitted and received radar radiation, the translation is at least substantially compensated.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be further described with reference to the following figures, of which: FIG. 1 indicates how a Cassegrain antenna and a gun can be built as one assembly; FIG. 2 represents a possible version of a Cassegrain antenna according to the invention; FIG. 3 represents a diagram of a first embodiment of the radar apparatus in operation wit
REFERENCES:
patent: H205 (1987-02-01), Green et al.
patent: 3683387 (1972-08-01), Meek
patent: 3924235 (1975-12-01), Heller et al.
patent: 4224507 (1980-09-01), Gendreu
patent: 5073782 (1991-12-01), Huguenin et al.
patent: 5075680 (1991-12-01), Dabbs
patent: 5281815 (1994-01-01), Even-Tov
Cool Peter J.
Fischer Henk
Withag Antonius J. M.
Hollandse Signaalapparaten B.V.
Sotomayor John B.
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