ES2238128B1 - Transparent parabolic antenna. - Google Patents

Transparent parabolic antenna.

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Publication number
ES2238128B1
ES2238128B1 ES200300122A ES200300122A ES2238128B1 ES 2238128 B1 ES2238128 B1 ES 2238128B1 ES 200300122 A ES200300122 A ES 200300122A ES 200300122 A ES200300122 A ES 200300122A ES 2238128 B1 ES2238128 B1 ES 2238128B1
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ES
Spain
Prior art keywords
transparent
antenna
reflector
conductor layer
layer
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Expired - Fee Related
Application number
ES200300122A
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Spanish (es)
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ES2238128A1 (en
Inventor
Juan Pablo Sarasa Delgado
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Juan Pablo Sarasa Delgado
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Abstract

Transparent satellite dish. To avoid the aesthetic degradation caused by satellite dishes, the author proposes the creation of a new antenna with a fully transparent concave or parabolic reflector (1). The main difficulty of this invention lies in making a transparent reflector (1). For this, it is necessary to find a material that is transparent to visible light and that reflects the radio frequency signals used by the antenna by concentrating them on the focus where the RF head (2) is located. This property is owned by a family of materials called "transparent conductors." The antenna has a concave or parabolic reflector (1) transparent to visible light and made entirely or with at least one layer of one or more transparent conductors. The transparent conductor layer is intended to reflect the electromagnetic waves belonging to the useful frequency band.

Description

Transparent satellite dish.

Field of the Invention

The present invention refers to the domain of telecommunications, more specifically to the field of radiocommunications and refers particularly to the realization of a transparent concave or parabolic reflector for an antenna intended for the reception and / or transmission of signals from radio frequency such as television, radio, etc.

Object of the invention

With the arrival of satellite television, the satellite dishes have been multiplied by the rooftops, facades, walls, terraces, balconies, etc. of the towns and cities coming in many cases to degrade its aesthetics. It is indisputable that a satellite dish 50 cm to 120 cm in diameter like the ones They are currently used for this type of application, it is very difficult to hide and therefore has a high visual impact. Some neighborhood communities have come to ban their installation depriving its residents of the technical advances for the benefit of the aesthetics of real estate.

In public buildings, such as embassies, consulates or ministries, satellite dishes up to 7 u 8 meters in diameter are sometimes necessary to ensure a Alternative communication path. Needless to say, many of these buildings belong to the historical heritage of the cities and that these antennas spoil its architectural beauty.

To avoid the aesthetic degradation they cause the satellite dishes, the author proposes the realization of a new antenna with a concave or parabolic reflector (1) totally transparent.

Background of the invention

An antenna of the parabolic type is an antenna of high gain in a specific direction of space. Their Applications are diverse: radars, microwave systems, satellite communication, radio astronomy, etc. An antenna Satellite dish like the ones we currently use to receive Satellite television consists of two distinct parts: the radiofrequency head (2) located in the focus of the parabola whose function is to receive and / or transmit RF signals (radiofrequency) and the parabolic reflector (1), commonly called parabolic, which simply reflects passively these signals. The parabolic is used to focus on a space direction the electromagnetic energy of the RF head in the case of transmission and to concentrate the waves electromagnetic at a single point or focus in the case of reception.

The main function of the parabolic reflector can be explained with the help of the geometric properties that It presents the parabolic curve (Figure 2). In the system of Cartesian coordinates x-y a parabolic curve It can be expressed as:

and 2 = 4fx,

where f is the distance from the vertex to the focus of the parabola. According to intrinsic properties of this type of curves, we can affirm that the sum of the distances from any point (such as A, B and C) of the parabola to focus F and to the points of the line y_ {1} -y_ {2} parallel to the guideline is a constant, it is tell:

FA + AA '= FB + BB '= FC + CC' = Constant,

A parabolic reflector is the curved surface which results from turning a parabolic curve along the x axis. This surface is called paraboloid. A part of the field of antennas, paraboloids are commonly used in flashlights and in the headlights of cars to focus the light in one direction from space.

For an electromagnetic wave to reflect totally or almost entirely on a surface, it has to Be made with conductive materials. So, all metals They are excellent candidates to be used as surfaces reflective The satellite dishes known by the author are not an exception: either they are made entirely of metal, or they are of a non-conductive material but contain a metallic layer.

There is another type of parabolic reflector that is made from a very fine metal grid inserted in a material that shapes while stiffness. So that one surface of this type reflects the electromagnetic waves, the grid holes have to be relatively smaller than the minimum wavelength on which the antenna works. Else, the parable would not fulfill its reflective surface role and not it would concentrate the radio frequency signals in its focus. When he material used to shape and stiffen the metal grid is transparent, these antennas seen from afar are translucent and by therefore its visual impact is less. However they present the great drawback that its translucency depends on the frequency of job. So, in the Ka-band systems where the frequency Working is very high and the wavelength is of the order of centimeter, the metal grid they should use would have about holes so small that the antenna would be practically opaque.

Bibliographic references

i)
Hung-Piu Ip and Yahya Ramat-Samii, Analysis and Characterization of Multilayered Reflector Antenna: Rain / Snow Accumulation and Deployable Membrane, IEEE Transactions on Antennas and Propagation , vol. 46, pp. 1593-1605, November 1998 .

ii)
Roy G. Gordon , Criteria for Choosing Transparent Conductors, Materials Research Society Bulletin pp. 52-57, August 2000 .

iii)
Ángel Cardama Aznar , Lluís Jofre Roca , Juan Manual Rius Casals , Jordi Romeu Robert and Sebastián Blanch Boris , Antenas , second edition, Edicions UPC, Barcelona 1994 .

US 6184840 B1 (Lin Hsin-Loug, Lee Ta-Lun) Parabolic Reflector Antenna.

Description of the invention

The main difficulty of this invention resides in finding a material that is transparent to visible light and that reflects the radio frequency signals used by the antenna concentrating them in the focus where the RF head (2) is located. Is that is, it is necessary to find a type of material that acts as filter of electromagnetic waves as a function of frequency. This type of material is characterized by a border from the which all electromagnetic waves whose frequency is less than that of the border are reflected and yet all the waves Electromagnetic with greater frequency pass through the material. This border frequency is known in Electromagnetism as the plasma resonance frequency or simply frequency of plasma (Ref. iii).

As we mentioned before, the materials commonly used for the construction of reflectors Satellite dishes are metals. Most metals have a plasma frequency much higher than light frequencies visible. These parabolics reflect the light and therefore not They are transparent.

The type of material we are looking for should have a plasma frequency greater than the frequency band useful (for example, around 12 GHz in Ku band or around 30 GHz in Ka band). At the same time, this frequency has to be low enough for the light frequency band visible (from 400 THz for red to 750 THz for violet) go through it in an adequate percentage so that the material is transparent to the naked eye. This property is owned by a family of materials called "transparent conductors" whose use is already widespread in flat screens, screens touch screens, oven doors, invisible safety circuits, windows for cars and buildings, solar cells and a long etc. From now on we will call "driver transparent "to all conductive material that has a frequency of plasma resonance low enough for the light visible through it in an adequate percentage so that the material is transparent to the naked eye and high enough so that the useful frequency band is reflected.

The present invention is composed of a antenna with a light-transparent concave or parabolic reflector visible and made entirely or with at least one layer of one or several transparent conductors. The conductor layer (or layers) transparent is intended to reflect electromagnetic waves belonging to the useful frequency band. The layer (or layers) of transparent conductor can fully cover the surface of the reflector or can have any form such as for example grid or thickness not constant.

Brief description of the drawings

To help the understanding of the invention described herein, some drawings are attached in the that, just as an example and in no case limiting, they represent practical cases of realization of the satellite dish transparent.

In said drawings, Figure 1 is a view in antenna perspective to differentiate its parts: reflector parabolic (1), RF head (2), head support (3) and the antenna (4). Figure 2 is a parabolic axis curve Cartesians that exists in the state of the art (US 6184840 B1) and which has been annexed in order to explain more easily the properties of this type of curves and therefore those of a parabolic reflector. Figures 3 to 5 are cross sections of the transparent concave or parabolic reflector showing possible Embodiments: Substrate with a transparent conductor layer (Figure 3), Substrate with a transparent conductor layer and a protective layer (figure 4) and transparent conductor between two layers of substrate (figure 5). Finally, Figure 6 is a graph that Calculate the percentage of increase to be applied to the diameter of the antenna to recover the losses in dB caused by the transparent conductor layer.

\ newpage
Description of a preferred embodiment

In this section of the present report, by way of example and in no case limiting, the realization of a transparent satellite dish used for satellite television reception is described. It can also be used for broadband multimedia services or any other type of application where a satellite dish is needed for transmission, reception or both at the same time. The reflector will be asymmetric (offset) although any type of concave or parabolic reflector can be used such as symmetrical, cassegrain, Gregorian, etc. The offset has been chosen because this is the type of reflector that is currently used for this type of
application.

The reflector will consist of several layers such as those depicted in the cuts of figures 3 to 5. No there is a configuration that is generally better than another, this It depends on the materials used in the conductor layer transparent or in the substrate layer. If the driver transparent is not weatherproof, as is the case with the  silver, a distribution of layers like that of the Figures 4 or 5. If the substrate has losses in the band of useful frequency of the antenna a distribution like the of figures 3 or 4. As illustrated, the distribution of Layers depend on the choice of materials to use.

The transparent conductor layer has for aim to reflect the useful frequency band. To carry perform this mission as well as possible, we must take into account two parameters that are fundamental: the width of the layer and the conductivity (sig) of the transparent conductor chosen. In the Ref. I, we found a study of the maximum gain of an antenna parabolic at the frequency of 1.4 GHz depending on the width of the metallic layer and metal conductivity. A layer of aluminum with a thickness of 1000 Å (100 nm) does not show losses of maximum gain appreciable at the frequency of 1.4 GHz the we compare with a perfect electrical conductor layer (\ sigma = \ infty S / m). The same layer with a thickness of 10 nm, although It is much less than the driver's film depth, just it presents a loss in the maximum gain of 0.1 dB. But nevertheless, conductivity is a very critical parameter: a 100 nm layer of mercury (around sig = 10 6 S / m) only has a few losses of 0.45 dB but graphite (around \ sigma = 10 5 S / m) would reduce the maximum gain of the antenna (3.7 dB of losses).

Typical thicknesses of conductor layers transparent in commercial products range between 150 nm and 0.2 mm and the conductivity of the transparent conductors more They are usually noted in the following table taken from ref. ii:

Driver Conductivity Transparent Ag 62.5 • 10 6 S / m TiN 5 · 10 6 S / m In_ {2} O_ {3}: Sn 1 · 10 6 Ye Cd_ {2} SnO_ {4} 0.77 ? 10 6 S / m ZnO: Al 0.66 • 10 6 S / m SnO 2: F 0.5 • 10 6 Ye ZnO: F 0.25 \ cdot 10 6 S / m

If for the construction of the parabolic reflector transparent we use a layer with a thickness of 100 nm of one of the first three transparent conductors of the table: silver (Ag), the TiN or the ITO (In_ {2} O_ {3}: Sn), as they have a conductivity greater than or equal to that of mercury (around sig = 10 6 S / m), we can affirm that the losses of maximum antenna gain will be very small (≤ 0.45 dB). Yes on the contrary the layer is one of the last four, the losses will be more important but never higher than those of graphite (around \ sigma = 10 5 S / m) since the four Materials have a higher conductivity.

To compensate for this maximum gain loss, one of the possible solutions is to increase the diameter of the antenna. If we approximate the projection of the parabolic reflector by a circle, in figure 6 we can find the percentage of increase to be applied to the antenna diameter depending on of losses caused by the transparent conductor layer. We can see that if the losses are less than 0.8 dB, the diameter would require an increase of less than 10% to recover losses and obtain a reflector equivalent to aluminum.

Returning to the offset reflector, we can manufacture it using a layer configuration like the one in figure 4, using for example acrylic, polycarbonate, polyester, or glass transparent as a substrate thick enough for the reflector be rigid. A 10 nm layer will be applied to the substrate of silver (= = 62.5.10 6 S / m) and a film for protect silver from the weather. A reflector of these features show losses of only 0.1 dB at 1.4 GHz. According to figure 6 this represents an increase in diameter of a one%.

Another possibility among many would be that of use a configuration like the one in figure 3, using the same substrate that we have described before to which a 100 nm layer of ITO (In_ {2} {3}: Sn) (around \ sigma = 10 6 S / m). This reflector would present approximate losses from 0.45 dB to 1.4 GHz, that is, an increase in diameter of 5%.

To the concave or parabolic reflector (1) you we will add an antenna support (4) and a head support (3) preferably made of a transparent material, for example  methacrylate, rigid enough to meet your function. The RF head (2) will be the only non-transparent part of the antenna together with the screws that we will use to join the different parts although we will limit its use to strictly necesary.

Claims (9)

1. Antenna with a concave or parabolic reflector (1) transparent to visible light and made entirely or with at least one layer of one or more transparent conductors. The transparent conductor layer (or layers) is intended to reflect electromagnetic waves belonging to the frequency band Useful.
Understanding "transparent driver" to any conductive material that has a resonant frequency of plasma low enough for visible light to pass through in an adequate percentage so that the material is transparent at a glance and high enough for the band to Useful frequency is reflected.
2. Antenna according to claim 1, characterized by having the transparent conductor layer (or layers) of the reflector partially covering its surface.
3. Antenna according to claim 1 or 2, characterized by having the transparent conductor layer (or layers) of the reflector with a variable thickness.
4. Antenna according to any one of claims 1 to 3, characterized in that it is of the symmetrical, offset, cassegrain or Gregorian type.
5. Antenna according to any one of claims 1 to 4, characterized by having a transparent antenna support (4).
6. Antenna according to any one of claims 1 to 5, characterized by having a transparent head support (3).
7. Antenna according to any one of claims 1 to 6, characterized in that it has a reflector with a transparent substrate that gives rigidity to the transparent conductor layer and the reflector.
8. Antenna according to any one of claims 1 to 7, characterized by having a reflector with a transparent layer that protects the transparent conductor from the weather.
9. Antenna according to any one of claims 1 to 8, characterized in that it has a reflector with a transparent conductor layer between two layers of transparent substrate.
ES200300122A 2003-01-17 2003-01-17 Transparent parabolic antenna. Expired - Fee Related ES2238128B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
ES200300122A ES2238128B1 (en) 2003-01-17 2003-01-17 Transparent parabolic antenna.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
ES200300122A ES2238128B1 (en) 2003-01-17 2003-01-17 Transparent parabolic antenna.

Publications (2)

Publication Number Publication Date
ES2238128A1 ES2238128A1 (en) 2005-08-16
ES2238128B1 true ES2238128B1 (en) 2006-07-01

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ES200300122A Expired - Fee Related ES2238128B1 (en) 2003-01-17 2003-01-17 Transparent parabolic antenna.

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Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE9001255U1 (en) * 1990-02-03 1990-04-05 Hagenbusch, Guenther, 7313 Reichenbach, De
JPH098543A (en) * 1995-06-20 1997-01-10 Koito Mfg Co Ltd Electromagnetic wave reflector and its manufacture
JPH11298234A (en) * 1998-04-13 1999-10-29 Dx Antenna Co Ltd Parabolic antenna
JP2001136014A (en) * 1999-11-04 2001-05-18 Ricoh Elemex Corp Transparent conductor antenna and radio unit provided with the same

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
BASE DE DATOS PAJ en Oficina de Patentes de Japón, JP 09008543 A (KOITO MFG CO LTD), resumen. *
BASE DE DATOS PAJ en Oficina de Patentes de Japón, JP 11298234 A (DX ANTENNA CO LTD), resumen. \\ Y 7-9 *
BASE DE DATOS PAJ en Oficina de Patentes de Japón, JP 2001136014 A (RICOH ELEMEX CORP), resumen. *

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Publication number Publication date
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