|Title of Invention||
"A METHOD OF MANUFACTURING A WAVEGUIDE CHANNEL FOR ELECTROMAGNETIC WAVES AND A WAVEGUIDE CHANNEL THEREOF"
|Abstract||When manufacturing waveguides, for example densely located waveguide channels, for electromagnetic waves such as microwaves, the channels are produced from rod-shaped bodies (1) of a material permeable to the waves and non significantly attenuating the waves. The bodies (1) can for example project from a base plate (3) and their side surfaces are coated with electrically conducting material but not their free end surfaces (5). The interior of the bodies form the waveguiding channels, which have their walls formed from the layer of electrically conducting material. By giving the rod-shaped bodies suitable shapes for example an antenna side or half of a waveguide antenna can be manufactured. The rod-shaped bodies can before applying the electrically conducting material be coated with one or several layers of non-attenuating and non-conducting lacquer filling pores and smoothing the surface of the bodies. Thereby, the layer of electrically conducting material obtains a smooth transition surface to the material of the bodies giving the channels good waveguiding characteristics. If the material used in the bodies has a strong surface porosity, the channels formed from the rod-shaped bodies become strongly attenuating to the electromagnetic waves. A set of such bodies located at the sides of each other and having suitable dimensions of the bodies gives an element working strongly attenuating to the electromagnetic waves.|
|Full Text||The present invention relates to a method of manufacturing a waveguide channel for electromagnetic waves and a waveguide channel thereof.
The present application relates to a method of manufacturing waveguide channels for microwaves, in particular wavegnide channels arranged closely at or ai the sides. of each other,
and furthermore a method of manufacturing elements for attenuating microwaves.
In waveguide antennas for receiving and transmitting electromagnetic radiation having frequencies in for example the GHz range the largest possible portion of the surface of the antennas should consist of open channels that are densely packed, i.e. are located closely at or at the sides of each other. This results in that the walls between the channels become long and narrow. Mannfacruring such long channels is impossible using the technology which at present is available for mass production. Wavegnide antennas having such channels are for example disclosed m the published international patent application WO 94/11920.
Waveguide channels for microwaves are generally often made as metal tubes haying accurate internal dimensions. Due to the required high accuracy the manufacture is costly and such channels therefore have high prices
SUMMARY OF THE INVENTION
It is an object of the invention to provide a low-cost method of manufacturing
waveguiding channels for electromagnetic waves snch as microwaves.
It is another object of the invention to provide a simple method of roannfacturing panels
attenuating electromagnetic waves snch as microwaves.
Thus, a body can be made from a material permeable for electromagnetic waves and thereafter be coated with electrically condnctmg material such as being metallized on some of its surfaces. For a suitable shape of the body and suitably selected metallized surfaces thereof then me interior of the body forms a waveguiding channel haying wall surfaces constituted by the interior surfaces of the electrically conducting metal layer. The body can be given a suitable geometric shape so that different waveguiding devices can be obtained such as simple separate channels, waveguide lenses and filters.
If the material of me body has a surface porosity, suitably' the surfaces of the body are first coated with a surface smoothing or evening material that does not significantly affect the propagation of the electromagnetic waves. This material can either be permanent or made to evaporate after coating with the electrically conducting material.
The surface porosity can also be employed for mannfacixaing a. structure attenuating electromagnetic waves, in particular microwaves. The a plate shaped body can be produced having cut-outs or recesses made in a first large surface of the body. Thereafter the first large surface is coated with electrically conducting material for forming an electrically conducting surface layer having a rough lower surface at the continuation' to -the. permeable or non-artenuating material haying a surface porosity. The inferior surface of the conducting material obtains such a roughness that it works strongly attenuating to waves incoming to the second,-
opposite large surface of the body. The cut-outs or recesses are suitably given such shapes that between them projecting rods are formed, the dimensions of the cross-sections of which somewhere are larger than half the wavelength of the electromagnetic waves in the material having a surface porosity. In addition to the attenuating effect resulting from the rough lower surface the waves are also hindered because of. the dimensions of the cross-sections of the channels formed in the rods.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of non limiting embodiments with reference to the accompanying drawings in which:
- Fig. 1 is a perspective view of a portion of a half of a waveguide antenna,
- fig. 2a is a cross-sectional view of a portion of a waveguide antenna,
- Fig. 2b is a cross-sectional view corresponding to Fig. 2a in a larger scale,
- Fig. 3 is a perspective view of a waveguide antenna in which half of an antenna side is removed,
- Fig. 4 is a perspective view of waveguides placed at the side of each other having special cross-sections, and
- Fig. 5 is a view of an attenuating panel.
Materials exist which have such a low attenuation of electromagnetic waves that they can approximately be considered as air in spite of the fact that they in other respects have characteristics of solids. An example of such a material is EPS (Expanded Polystyrene) that has an attenuation coefficient smaller than 0.1 dB/dm. This material, can be easily used for manufacturing bodies having very varying shapes. In Fig. 1 is in a perspective view shown a portion of a waveguide antenna made from such a material having an insignificant attenuation for electromagnetic radiation, see also the part cross-sectional view of Fig. 2a. The waveguide antenna is formed from rods 1 that project to one side from a for example flat base plate 3 keeping the antenna together to form one unit. The rods 1 are on their side surfaces coated with an electrically conducting layer, see the description hereinafter. The end surfaces 5 of the rods have no such coating but in contrast there is a conducting coating on the free surface portions 7 of the base plate which are located between the rods 1. Thereby the interior of the rods, i.e. the regions inside them, interior of the electrically conducting surface layers, waveguiding channels. The rods 1 have furthermore geometric shapes adapted to the refracting function of the waveguide antenna so that the waveguiding channels together give the desired lens function. The rods can thus be tapering in a direction away from the base plate 3, as seen in the figures.
When using the above mentioned material EPS and similar expanded polymer materials such as expanded polyurethane for manufacturing waveguiding channels according to the description above, bodies of the material can be first produced by expansion caused by a suitable heating of an adapted amount of non-expanded material placed in a close mould
cavity. Then the produced bodies can be coated with an electrically conducting paint for producing the conducting surface layer. The material of bodies produced in that way is however at the same time often porous, and if bodies made therefrom are directly coated with a conducting paint, pores 9 at the surface of the bodies are filled with the conducting paint. These pores can extend a good distance into the expanded polymer bodies, see Fig. 2b. A surface having such pores filled with an electrically conducting material is>. rough and attenuates electromagnetic wave propagating inside the bodies. The result is - particularly in the case where the bodies of the material contains pores extending deeply from the surface -that the interior of the bodies do not obtain any waveguiding properties for electromagnetic waves and thus do not work as waveguides due to the fact that the interior of the bodies have metal walls which are strongly attenuating for electromagnetic waves inside the bodies.
To avoid such attenuating effects the bodies of the structural material used, for example EPS, are first coated with one or several layers of an electrically non-conducting lacquer that does not work significantly artertuating for electromagnetic waves and that both fills the surfaces pores and smooths the surface of the bodies. Thereafter the electrically conducting lacquer is applied and it then forms a completely smooth outer-most layer on the bodies having in particular a smooth interior surface where this lacquer continues into the next underlying layer of non attenuating lacquer. The layer of electrically non-conducting lacquer can be applied to the bodies by dipping or immersing or by inmould-methods.
Alternatively the bodies can be first coated with an electrically non conducting liquid mat also both fills surface pores of the bodies and smooths the surface of the bodies. The liquid can be selected so that it prevents the electrically conducting lacquer from penetrating into the bodies and so that it is evaporated or evaporates after applying the electrically conducting lacquer. Such a liquid can include a liquid, for example water, that is completely non-miscible with the electrically conducting lacquer.
To mass marnrfacture waveguiding structures for for example antenna function often several moulds are required, for example one mould for one side and another one for the opposite side. In Fig. 3 a waveguide antenna is shown in which half of an antenna side is removed. Using this manufacturing method it is possible to make channels having adjacent sides in common and a more narrow interior portion. In such a case, as has been described above with reference to Figs. 1 and 2, the sides of the rods 1, which then correspond to portions of waveguide channels, and the common surfaces 7 between two rods are coated with conducting material but not the surface 5, at which two halves are to be joined to each other. Thereafter opposite surface of the antenna sides are joined to each other and continuous channels having optimized entrance and exit sides are obtained.
Devices having different kinds of waveguiding channels can be manufactured. In Fig. 4 for example waveguides are shown that are obtained from rods located at the sides of each other and having T-shaped cross-sections. The rods 1 generally have different shapes depending on the intended application. Thus they can have substantially square cross-sections,
such as for waveguide channels for general use, or rectangular cross-sections, such as for waveguide lenses, filters and plan/circular-rotating arrays intended for only one of the polarisations of an electromagnetic wave.
Reflecting waveguides, not shown, can be manufactured by first producing suitable rod-shaped bodies according to the description above and that then one of the end surfaces of the bodies are coated with electrically conducting material in addition to the side surfaces. This gives a reflection, so mat an incoming electromagnetic wave first enters the channels formed by the bodies from the uncoated ends of the rods and then turns and exits the same channels.
If suitable rod-shaped bodies are first produced according to the description above and men only two opposite side surfaces of the bodies are coated with electrically conducting surface layers, lenses or filters formed from parallel plates can be obtained which are intended for electromagnetic waves having a single polarisation.
The rods should generally have cross-sectional dimensions larger than half the largest wavelength for which their waveguiding functions are to be utilized for amplifying or filtering.
Simple waveguide channels, not shown, can be manufactured in the similar way. A simple straight body having for example a uniform rectangular cross-section is first produced. The body is bent to the desired shape and is then coated with one or several layers of electrically non-conducting lacquers, for example of an epoxy polymer, and finally with a layer of electrically conducting material. The coating with lacquers and in particular with a polymer material results in that the body will permanently maintain its shape.
The property of attenuating electromagnetic waves of bodies of the mentioned materials directly coated with an electrically conducting lacquer can be used for manufacturing attenuating surface panels. An example of such a panel is shown in Fig. 5 and includes a plurality of conically shaped or pyramidal recesses located at the sides of each other and formed in one of the large surfaces of an otherwise flat body. The recesses are thus directly coated with electrically conducting paint. The panel works, for a suitable shape of the recssses and provided that the lacquer has well penetrated into the surface pores of the panel, attenuating to electromagnetic waves which are incident to the opposite large surface of the panel that can be substantially fiat and is not coated with an electrically conducting layer. If a closed space is lagged with such panels, the flat surfaces of the panels directed to the interior of the space, a space is obtained in which possible electromagnetic waves are efficiently attenuated. The portions of the recesses located between the panels that correspond to the waveguide channels according to the description above should generally somewhere, for example at their entrances or at their central portions, have cross-sectional dimensions larger than half the largest wavelength for which their attenuating function is to be used.
1. A method of manufacturing a waveguide channel for electromagnetic
waves and a waveguide channel, the said method comprising the steps of:
producing a rod (1) from a material which is not attenuating the
electromagnetic waves, giving the said road a shape corresponding to the
shape of the waveguide channel, characterized by
coating exterior surfaces of the road (1) with at least one layer of
electrically non-conducting liquid as herein described, lacquer or paint
that is not attenuating to the electromagnetic waves, and
that fills pores and smooths the surfaces of the rod (1), and
thereafter coating with electrically conducted material, on top of said at
least one layer of electrically non-conducting lacquer or paint, the rod (1).
2. A method as claimed in claim 1, wherein, in the step of coating exterior surfaces of the rod (1), the electrically non-conducting liquid, lacquer or paint liquid, is selected to be an electrically non-conducting liquid that prevents the electrically conducting material from penetrating into the rod, and is evaporated after coating with the electrically conducting material.
3. A method as claimed in any of claims 1 and 2, wherein said at least one layer of electrically non-conducting liquid, lacquer or paint is coated using dipping.
4. A method as claimed in any of claims 1 and 2, wherein said at least one layer of electrically non-conducting liquid, lacquer or paint is coated using an inmould-process.
5. A method as claimed in any of claims 1 to 4, wherein a plurality of rods (1) are produced as a multitude of rod-shaped bodies located at each other, each of said plurality of rods (1) given a shape corresponding to the shape of a waveguide channel for the electromagnetic waves.
6. A method as claimed in any of claims 1 to 4, wherein a plurality of rods (1) are produced as a plurality of rod-shaped bodies located at each other and projecting from a base plate (3).
7. A method as claimed in any of claims 1 to 6, wherein the rod (1), rods is produced from an expanded polymer material.
8. A method as claimed in any of claim 7, wherein the body (1), rods is produced from expanded polystyrene.
9. A method as claimed in any of claims 1 to 8, wherein the rod (1), is produced from a polymer material having a surface porosity.
10. A method as claimed in any of claims 1 to 9, wherein a plurality of coated rods (1) are separately produced, each forming a waveguide channel for the electromagnetic waves, and thereafter said coated rods (1) are joined to each other.
11. A method as claimed in any of claims 1 to 10, wherein side surfaces and only one end surface of the rods (1), are coated with said electrically conducting material to give a reflection, so that incoming electromagnetic waves first pass into the channel formed by the coated rod (1) through the uncoated end surface (5) and then turn and pass out of the same channel.
12. A method as claimed in any of claims 1 to 10, wherein only two opposite side surfaces of the rod (1), rods are coated with said electrically conducting material in order to obtain lenses or filters intended for only a single polarization of the electromagnetic waves.
13. A method as claimed in claim 1, wherein
- in the step of producing the rod (1), a plate-shaped rod is produced having a surface porosity having cut-outs or recesses made in a first large surface of the plate-shaped rod, and
- in the step of coating exterior surfaces of the rod (1), the first large surface of the plate-shaped rod is coated with the electrically conducting material in order to form an electrically conducting surface layer having a rough lower surface at the continuation the non-attenuating material, so that for electromagnetic waves incoming to the plate-shaped rod, to a second, opposite large surface of the plate-shaped rod, the rough lower surface works attenuating.
14. A method as claimed in claim 13, wherein in the step of producing the
plate-shaped body, the cut-outs or recesses are made to form there
between projecting rods (1), the dimensions of the cross-sections of which
somewhere are larger than half the wavelength of the electromagnetic
waves in the material having a surface porosity so that, in addition to the
attenuating effect produced by the rough lower surface, the
electromagnetic waves are also prevented because of the cross-sectional
dimensions of the channels formed by the projecting rods into which they
15. A waveguide channel using the method as claimed in claim 1, for
attenuating electromagnetic waves comprising a plate-shaped rod of a
material which is not attenuating the electromagnetic waves and having a
surface porosity, the plate-shaped rod having cut-outs or recesses made
in a first large surface of the plate-shaped rod and the first large surface
being coated with an electrically conducting surface layer of electrically
conducting material, that has a lower surface at the continuation to the
|Indian Patent Application Number||IN/PCT/2002/01115/DEL|
|PG Journal Number||43/2010|
|Date of Filing||12-Nov-2002|
|Name of Patentee||STIG ANDERS PETERSSON|
|Applicant Address||HOKMARK 1585, S-930 10 LOVANGER, SWEDEN|
|PCT International Classification Number||H01P 11/00|
|PCT International Application Number||PCT/SE2001/00991|
|PCT International Filing date||2001-05-07|