Note: Descriptions are shown in the official language in which they were submitted.
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l~licl~o w~lve anterln~l
This inven~ion relatcs to ~Intenn~ls of the kind including
a reflectillg surface collecting or focusing ~he radiation.
Antennas of this kind are ror instance radar antennas,
so-called p.lr~bolic antennas for transmitting and receiv-
ing for instance s.ltellite television as well as antenna~for telephone communication. Antennas of this kind have
been known for several years and these antennas have been
made in different ways. Up to now these antennas have had
a tendency to be comparatively expensive to make or of
bad quality due to the fact that the reflecting ~urface
must be very careully shaped in order to allow an opti-
mum output. Already very small deviations rom the ideal
surface result in essential power losses. One fabrication
method used for the fabrication of antennas of this kind
is the enclosing of a metal net in a glassfiber reinforced
plastic, which for instance has been shown in the US patent
2 948 896.
Yet another method of fabrication is to coat the reflecto-
ry surface of the antenna with a metal, which for instance
20 has been shown in the French patent 2 502 852, which like
the device according to the US patent mentioned above is
'a sandwich-construction, i.e. a construction with several
different la~ers in order to a'chieve a sufficient strength.
These two constructions mentioned are however comparative-
ly expensive to fabricate due to the great number of fab-
rication steps as well as the amount of used parts. Nor is
the desired exactness for the reflectory surface obtained.
This exactness in its turn is very important in order to
ensure maximum gain for the antenna.
The object of the invention is therefore to define an em-
bodiment and a method for fabrication of parabolic anten-
nas, which is essentially simpler than known technique and
at the same time, results in an improved exactness in the
reflecting surface.
In accordance with the invention this object is obtained
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by vacuum l`olmi~ tl~e antellna or sh~ping this in a heat~.t
state from for il~t;lllCe ~ lstiC, W]liCh before the sha~ g
can be coatc~ ~ith ~ metal l~yer. ]n this way a very exact
reflecting su~ ce l~or the micro wave in question is ob-
ta~ned with .I conlp.lratively cheap method. The reflectorcan either be m~de with a reflecting layer, "preferably
of metal" on its front side or on the back side of a p];l5-
tic layer.
In case the metal layer is arranged on the outside it c~n
1!~ not be left in tl~is con~ition, but must suitably be co~ted
or in some other way covered with a protective layer, not
only to protect the metal layer, but also to prevent the
parabolic antenna from functioning as a sun reflector which
might burn the recei~ing means in the focus point.
It is important that the layer in front of the reflectin~
surface is very thin or has a thickness related to the wavc
length of the radiation that is to be reflected in order to
prevent power loss.
In an embodiment of the invention the shaping does not only
include the metal layer and a supporting plastic layer, but
also a third layer, so that the metal layer is enclosed
~between two plastic layers, a thin one and a thicker one,
in front of and behind the metal layer respectively. This
shaping can take place in one common concurrent operation or
in separate operations.
Several different types of material can be used for the
fabrication of an antenna in accordance with the inven-
tion. For example acrylic can be used and for instance a
mixture consisting of 25~ impact resistant acrylic and
75~ of a not impact resistant acrylic.
In an antenna particularily adapted to northern latitudes
it is possible to arrange heating of the antenna in a known
manner behind the shell comprising the above mentionedl~rs
and to arran~e a further shell behind the heatin~ device paltly in
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order to en(io~ tll~ he~t ~In~ p.lrtly in order to prot~t
the heating device. 1`he~e ~hells enclose a Closed intel-
mediate space ror the he~ing device, which space also
serves to distribute the heated air. In one embodiment of
the invention the he~til1g layer, that can consist of re-
sistance wires, }1e~ting cloth or tl1e like, and the rear
enclosing shel] cal- I)e s11~}>~ in the same operation. Al-
ternatively the method of foaming can be used. By appro-
priately enclosing the heating device in this way or
another whicl1 will be exempli~ied below it will be possi-
ble to feed the heating device directly with a net vol-
tage without an intermediate transformer and without safe-
ty risks.
The shaping of the antenna preferably can be made against
a positive mould, i.e. that the surface brought in contact
with the mouId is the front side of the antenna. In this
way one also obtains the advantage that the same tool can
be used independently of how many layers or how thick the
antenna is to be made. In case the heating device is also
enclosed in the shaping it is possible, if this consists
of radial spokes holding the resistance wires, to obtain
'radially extending projections in the rear shell or layer,
which further increases the st~ffness of the antenna. Of
course similar reinforcements can be obtained in other
ways, for instance by the shaping of a rear shell in a
separate operation, a suitable amount of space being
i~c.
provided for the heating device between the front and rcar
shell of the antenna.
It is of course ~llso possible, in order to place a heating
device between the front and rear shell, to include dist-
ance elements of a suitable material, e.g. polyurethane.
Within the scope of the invention it is of course also
possible to carry out the shaping in two steps, so that ~
the front layer or shell is first shaped according to the
mould, rhen the rear shell or layer~s) is heated and sh.lped
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by suction ()r l-r(~urc over thc lir~t rront shell.
The invention i~ o~ to he described bv way of examl)]e
with referc~nc~ to thc dr;~ 1s. Iig l shows a section
through a l~art ol .lll antel~ in accordance with the in-
vention whi~c fi~s ~ ~nd 3 5]10W the susl)endin7 of theantenna.
The antenna shown in fig 1 includes a front shel', which
has been given the reference numeral 1. This shell, in its
turn has a rear supporting plastic layer 2, a metallic
layer 3 applied on the front side of this and about
12~1n thick, and a protecting layer in front of the metal layer
the protecti~e layer being 130-150/~-m and given the re-
ference number 4. Instead of being built up in this way
the front layer can be relatively thin, preferably 1,5 n~
at the most, and coated with metal, which on the rear side
will be protected in this way in the interior of the antcn-
na. The antenna further includes a rear shell having the
reference numeral 5. The front shell 1 and the rear shell
5 are then at the circumference thereof arranged close to
each other and sealed with a seal 6 (or by glueing), that
runs around the circumference of the antenna. The antenna
~can either be an unbroken surface or provided with a hole
in the middle as is shown. The hole in the middle can be
closed in the same way as at the outer edge or in the way
shown with a ring 15 between the antenna shells and a ruh-
ber mold 22 gripping this distance ring 15 as well as the
two antenna shells.
As can be seen the shells 1 and 5 are so shaped that thcy
define between themselves a space, in which a resistance
wire 7 is placed. This is in the left part of the figure
shown as secured in a holder 8 extending like spokes and
provided with oblique cuts, so that the resistance wire
cannot lose its grip. The parts 8 arranged like spokes
are fastened to the rear antenna shell, e.g. by rivets
23 of plastic. In the right part of fig 1 the resistance
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- wire 7 i~ p~ ol~ ~)3` ii~ .tn insul~ting ~llsc 9, which
further impro~c~ tl~ he~lting of the front side of the all-
tenna, since th~ l from the resistance wire 7 is pre-
vented by the ins~ tiol) I`rom being led hackwards. Since
in the rig~t .~s ~ell as in the lert embodiment an air s~
ce is present for air circuiation behin~ the front shell
of the antenn~ ~n everl heating of the antenna front shell
is ensured.
The antenna is at its outer edge elastically suspended in
l() a circular rramc. lhis elastic fastening is achieved by
the aid of rubher elements 10, at which bolts are fastene~l
that in turn are fastened at the antenna and the support-
ing construction, respectively, which in fig 1 in parti-
cular constitutes a frame 11. At the fastening point of
lS the elastic e]ement 10 at the antenna special washers are
adapted to the circu]ar shape of the antenna, partly to
achieve a good seal and partly to allow as much freedom
of movement as possible between the antenna and the sup-
porting frame. Since several elastic fastening elements
10 are arranged around the antenna, the antenna always
retains the same amount of directional stability as the
'supporting frame, so that in spite of the elastic arrange-
ment of the antenna, permitting movement due to tempera-
ture differences, the antenna always maintains its direc-
tion, which is very important in order to achieve a goodreception.
Fig 2 shows the supporting frame of the antenna shown in
fig 1 which is shown here only schematically and giYen
the reference numeral 12. The circular frame 11 is con-
nected with further details of framework constructionthat is journalled in an upper journalling point 13 and
can be adjusted with a screw 14 to its elevation. The
journal 13, as can be seen in particular from fig 3,
consists of two ears 17 and 18, a strut 16 arranged be-
tween these ears and journal not shown therebetween. Since
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the ears 17 an~ ale rel.ltively far apclrt a good sta-
bility is obt.~ od even il` a play should occur in the
journal 13. 'Ihe strut 16 is in i~s tu-rn fastened to a
vertical strut 1~ ich in turll constitutes a journal
for movement- i n the llorisont~ll plane in a ixed frame,
that has been g-iven the reference numeral 20 and which
is intended to be fastened to a wall or mast.
At one of the ears 18 is further Eastened a latent strut
21 extending to a frame part 20, with which a fine adjust-
ment or change of the direction of the antenna in thehorizontal plane can be achieved. By mounting the strut
19 in a way known per se in parallel with the axis of
the earth it is possible to use the antenna for receiving
or emitting signals from several different satellites.
The antenna is changed ~rom one satellite to another only
by a small change of the adjustment means 21. The adjust-
ment means 21 can even be replaced by a device driven by
an electrical motor.
Finally it should be mentioned that the better precision
and the improved design of the antenna in accordance with
the invention results in a far stronger signal than wh~t
'is the case with the known antennas, which in turn means
that the antenna in accordance with the invention can be
made with approximately 30~ smaller diameter than what else
should have been possible.
Within the scope of the invention it is also possible to
apply the reflective coating after the shaping or forming,
e.g. by metal spray.
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