Wave transmission lines and networks – Wave mode converters
Reexamination Certificate
2000-10-16
2002-11-19
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Wave mode converters
C343S771000
Reexamination Certificate
active
06483392
ABSTRACT:
The invention relates to a polarizer for electromagnetic radiation, wherein the polarizer has electrical conductive elements arranged in parallel and in specific distances to one another.
In order to obtain a dual circular right or left polarized electromagnetic wave, planar polarizers that are situated above the radiating antenna opening are used for planar antennas that are arranged as dual linear polarized antennas.
The polarizer breaks up the E-vector of an impinging wave into two orthogonal components and produces a phase difference [spacing phase] of ±90 degrees between the components and which, with subsequent overlay, results in a circular polarization. The mode of action likewise applies to the conversion of a circular into a linear polarization.
Two constructively different types of polarization are known. The one type of polarization uses several Polarization structures arranged in an interval of &lgr;/4 (quarter lambda) that act on the one hand inductively and on the other hand capacitatively on the respective E-field components and thus produce the phase difference. These polarization structures are often carried out as etched complex folded line circuits on a matrix (foil). In this situation at least two such structures (inductive, capacitative) are required for a polarizer. The required witch or spacing is created by the use of a low dielectric material. The disadvantage in this embodiment is its high sensitivity to engineering tolerances. Likewise, good flatness and very precise positioning of the foils used must be assured. This frequently leads to additional expense in the form of positioning guides for gluing and bonding and where [com]pression of the layers is required.
Another polarization type also uses electrically conductive elements in the form of metal struts [sic] which are arranged at a 45 degree angle to the linear polarization. Due to the different electrical constraints two different field types form and are expanded by the polarizer. Due to the different propagation times a phase difference of ±90 degrees is produced at the output of the polarizer at superpositioning of these phase types and, consequently, a right or left circular wave is produced. The electrical characteristics are determined by the spacing of the metal struts relative to one another and their length in the principal direction of antenna radiation. The metal struts are enclosed in a metal frame and their ends are either bonded or soldered to the frame. The advantage of this type of polarizer is the electrical simplicity and the satisfactory electrical characteristics such as, for example, large frequency bandwidth, relative insensitivity to engineering tolerances, very low insertion loss, very good elliptical [wave] values and adaptation. The disadvantage in this polarizer type is the costly and consequently the expensive fastenings of the metal struts to the frame, since either two bonding- or soldering steps are involved for each metal strut. Moreover, frequently metal stresses are created that are caused by the engineering tolerances at the time of manufacturing the metal struts and when inserting the metal struts into the mounting frame. The mounting frame weight is disproportionally high, since it is most often made of metal.
The purpose of the present invention is, therefore, to provide a polarizer that is simple in construction and economical to manufacture.
The solution to this problem presented on the one hand by a polarizer of the type described earlier and pursuant to the invention in which the elements are held in position by at least one spacer element, wherein each spacer element is made of a low dielectric material. A further solution is offered if the elements are removably or unremovably inserted into a board or strip shaped spacer and are held in position relative to one another by at least one spacer element.
In the polarizer described in the invention the mounting frame is eliminated completely. By doing so, the weight of the polarizer is advantageously reduced. The positioning of the conductive elements which are most frequently fashioned from metal struts or metal strips is achieved by the spacer made of a particularly low dielectric material. Since the recesses provided for accepting the conductive elements are milled, etched or otherwise produced at the same time in the form of grooves, slots or bore holes in the low dielectric material, the spacing and the width or pitch of the grooves or slots relative to one another is always the same and is subject to only low engineering tolerances. This solution represents an essential improvement of the electrical characteristics of the polarizer.
Polystyrol in its foam form, for example, is suitable as the low dielectric material.
It is advantageous to realize the grooves or slots, that are arranged at a 45 degree angle to the linear polarization, somewhat narrower than the conductive elements to assure that the conductive elements do not fall out of the spacer element. By inserting the conductive elements into the grooves or slots the side walls of the slots are pushed apart whereby a compression force is produced which prevents the elements from falling out of the slots. However, this procedure can also result in the occurrence of very high tensions in the spacer that is preferably constructed as a plate or strip. These tensions can be reduced or completely eliminated if additional recesses are provided in the spacer. Said recesses can be placed on the side containing the grooves or slots and/or on the side opposite to same. In this manner, the material that is displaced by the inserted conductive elements can expand without the occurrence of internal stresses within the spacer that would tend to deform it [lit. to “bend” it]. The supplemental recesses can, for example, also be grooves or slots. The shape of the recesses is optional and can be adapted to local requirements.
In order to prevent the metal struts from falling out as conductive elements there is the additional possibility of covering or enveloping the polarizer with the same low dielectric material used in the spacer. This can be done by a bonding process or by coating, application of a foam, or foaming over the surfaces of the grooves or slots.
It is also possible to bond the elements together with the spacer element. In a further advantageous embodiment of the invention the conductive elements do not rest in grooves or slots, but in bore holes into the low dielectric material. Depending on the cross-sectional shape of the conductive elements the borings can be replaced by the recesses adapted to that shape.
The conductive elements can be advantageously prevented from falling out of the grooves or slots in that the depth of the grooves or slots may be larger than the height of the conductive elements in such a manner that each groove or slot together with the element situated in it can be filled or covered with a sealant or filler material and preferably done to be flush with the surface of the spacer element. In this way a flat surface of the polarizer is made possible whereby at the same time the conductive elements are protected from corrosion.
The necessary spacing between the antenna and the conductive elements of the polarizer can be integrated into the overall level of the low dielectric material.
In order to fasten the polarizer to a planar [flat, bedspring] antenna it is sufficient that the already existing external edges of the planar antenna housing be extended and after placement of the polarizer on the antenna it be folded over it so that the polarizer forms a unit with the antenna.
A further advantageous embodiment of the polarizer would be if the interspaces between the conductive elements were partially or completely filled with a low dielectric material. The low dielectric material The low dielectric material can, but does not have to be, the same low dielectric material as that used in the spacer element. It can be pushed in or filled in between the elemen
Fischer Frank
Hennemann Martin
Chang Joseph
Pascal Robert
PATES Technology Patentverwertungsgesellschaft fur Satelliten- u
Woodbridge & Associates P.C.
Woodridge, Esq. Richard C.
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