Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Reexamination Certificate
2000-05-19
2001-11-27
Blum, Theodore M. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
C342S019000, C342S383000
Reexamination Certificate
active
06323806
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an antenna with an omni-directional antenna and with a (first) auxiliary antenna, the received signals of which are combined in respect of amplitude and phase in such a way that a reception minimum results in a desired spatial direction.
2. Discussion of Background
Such an arrangement with two electrically connected antennae and a single reception minimum is known from EP 0 124 047 A2. The reception minimum serves to attenuate the signals from a jammer (jamming transmitter) which is interfering with reception by the antenna installation, sufficiently so that useful signals can be received from a direction other than that of the jammer.
Omni-directional antennae particularly with an almost hemispherical receiving range are well suited for the receipt of signals transmitted from satellites, in particular from satellites traversing the earth's surface. These include, for example, location and navigation satellites, e.g. GPS satellites (GPS=Global Positioning System). It can be assumed that the jamming capacity of the jammer is greater or even very much greater than the capacity of the individual satellites to be received at a ground station. Known modern GPS receivers, certainly tolerate interference levels up to a certain extent greater than the GPS receiving capacity. However, where the interfering capacity is too great, a reduction of the interfering capacity is required.
The use of an omni-directional antenna with a single auxiliary antenna for the production of a single reception minimum produces a funnel shaped reception minimum and not a point reception minimum. The effect of this is that with sufficiently strong suppression of the jamming, reception of a satellite cannot be recieved with suffiecient strength, not only when it is exactly in the same direction as the interference, but also when it is in a spatial angular region in the vicinity of the jammer, due to the strong attenuation of the reception signal.
SUMMARY OF INVENTION
The object of the invention is to provide a possibility in which the spatial angle region with marked attenuation of the reception signal in the neighbourhood of the jammer, more generally the region in the neighbourhood of the spatial direction, in which a reception minimum is to be produced, is reduced, compared with that of known antenna installations. This object is met by the features of Claim
1
and through the features of the independent Claim
7
.
In accordance with the invention, the arrangement can be found so that the first named auxiliary antenna in combination with the main antenna produces in operation only a single reception minimum or several reception minima. In addition, the further auxiliary antennae can, in combination with the main antenna, produce only a single reception minimum or several reception minima. It is preferred that one of the auxiliary antennae (in the example the first named auxiliary antenna) produces only a single reception minimum and that other auxiliary antenna produces a plurality of reception minima. The further explanations relate first to this preferred embodiment. Other embodiments will be discussed in the conclusion.
In accordance with the invention both the attenuation which is achieved by the first named auxiliary antenna alone (if necessary in combination with the omni-directional antenna) and the attenuation achieved by the additional auxiliary antennae alone (if necessary again in combination with the omni-directional antenna) are designed in such a way that even in the region of the reception minimum of the first named auxiliary antenna or of all reception minima of the further auxiliary antennae the receipt of the desired useful signals, e.g. of satellites, in particular of location satellites, can still be reliable. Only in an individual spatial direction, namely in that spatial direction in which the first named auxiliary antenna produces a reception minimum, is its reception minimum overlain by one of the reception minima of the additional auxiliary antennae and there produces a strong attenuation in a greatly reduced angular region such that practically only a point jammer of reception by the antenna installation is excluded. In connection with the circulating satellite this means that the signals from a satellite can only not be received in that very short time period in which it may find itself precisely behind the jammer.
One advantage of the invention is that the availability of satellite signals is increased compared with the state of the art so that the invention is suitable in particular even for security relevant installations for example for the continuous provision of precise positioning signals to aircraft approaching an airport.
The first named auxiliary antenna and/or the additional auxiliary antennae may likewise be an omni-directional antenna, in particular with a hemi-spherical receiving range. Here the advantage is that the direction of the combined reception minimum can be set over a wide spatial angular area by electrical means alone (alteration of amplification or attenuation, setting of a suitable phase displacement between the signals and the auxiliary antennae and the omni-directional antenna). It may also be possible, in certain cases, to employ as auxiliary antennae those which already provide a certain directivity, particularly if the jammer is not mobile so that mechanical tracking of the antenna is not necessary. Such antennae are however possibly less suitable for the attenuation of interference signals from other directions. Since a jammer is generally located close to the horizon, those omni-directional antennae which have a reception minimum in the vertically upwards direction can be used as auxiliary antennae.
If several jammers have to be faded out at the same time then, in the simplest case, an additional auxiliary antenna of the first named type and an additional further auxiliary antenna is required for each additional jammer.
REFERENCES:
patent: H740 (1990-02-01), Gutleber
Airsys Navigation Systems GmbH
Blum Theodore M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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