EP1876673B1 - Directional antenna for transmitting and/or receiving audio/video signals - Google Patents

Abstract

The antenna has identical antenna elements supplied by currents of same phase and same amplitude, in a radio electric manner. Each element comprises a radiation element (1) that is formed of two quadrilaterals that are connected by a common top, a supply center (2) and a reflector (3). A coupling connects the radiation elements, which are coplanar and separated, where the quadrilateral of one of the elements has sides parallel to one side corresponding to other elements of the coupling. The supply centers are aligned along a straight line that does not cut the quadrilaterals. An independent claim is also included for a mobile radiotelephony relay antenna comprising a directional antenna.

Description

The present invention relates generally to a directional antenna for transmitting and / or receiving audio and / or video signals.

More specifically, the invention relates to a directional antenna for transmitting and / or receiving audio and / or video signals, of the kind comprising a plurality of identical antenna elements, electrically powered by currents of substantially the same phase and likewise amplitude, each antenna element comprising a radiating element formed of two quadrilaterals joined by a common vertex, a feed center and a reflector associated with this radiating element.

The mobile telephony network known as GSM ("Global System for Mobile Communication") comprises high-gain omnidirectional fixed antennas capable of transmitting and receiving electromagnetic signals at 890-960 MHz towards handsets. laptops or cell phones nearby.

However, despite a significant geographic network, certain obstacles, particularly urban or natural, caused for example by field accidents create operating anomalies such as propagation fading due mainly to multiple reflections of electromagnetic waves.

Antennas are already known comprising radiating elements of biquad type essentially omnidirectional antennas.

In this connection, we can mention the US Patent 4479127 wherein a horizontally polarized omnidirectional antenna is described formed of four antenna elements each comprising a radiating element consisting of two quadrilaterals united by a common vertex. These four antenna elements are respectively arranged in a first and a second pair of parallel elements, these first and second pair of elements being orthogonal to each other and the elements of each pair being equidistant from the axis of the assembly.

On the other hand, it was reported in the application for EP1523062 an omnidirectional antenna comprising four identical antenna elements and in vertical rectilinear polarization. Each antenna element comprises a biquad radiating element and a feeding center, each of the feeding centers being on a common circle and at the intersection points of two diameters orthogonal to this circle. In addition, the main radiation lobe of each antenna element has an aperture of substantially 90 ° in the vertical and horizontal planes while the centers of supply of two adjacent antenna radiating elements are separated by a length of λ working wave.

Nevertheless, these known omnidirectional antennas could not provide an appropriate solution to the problems mentioned above.

The object of the present invention is to propose a directional antenna of the type indicated previously that can be used for example in the GSM / GPRS band, that is to say at frequencies of the order of 880 to 1830 Mhz and which makes it possible, when it is used alone or in combination with other types of antennas, to disadvantages of the state of the art including improving the performance of known antennas. (GPRS: "General Pocket Radio Service" ie General Packet Radio Service).

To achieve this goal, the antenna according to the invention is characterized in that it comprises a coupling of at least two coplanar and separate radiating elements, each side of the quadrilaterals of a radiating element being parallel to the corresponding side of the other radiating elements of the coupling and in that the respective feeding centers are aligned along a line that does not intersect any quadrilateral.

Thus, each antenna element comprises a radiating element or radiator consisting of a double continuous loop taking the geometric form of two squares located in the same plane, having a common vertex and perimeter substantially equal to two wavelengths (2λ ).

Such a radiating element may be designated later in the description as in the claims by the name "biquad".

Generally, the coupling in question may comprise from 2 to 8, in particular from 2 to 4 and preferably, 4 radiating elements as described above.

In addition, according to a particular and advantageous feature of the invention, the line of alignment of the feed centers is orthogonal to the longitudinal axis of each of the biquads, that is to say the axis passing through the vertices. the farthest from the two quadrilaterals forming each biquad.

This biquad is usually made from a wire, preferably copper, disposed at a small distance from the reflector to which it is attached. However, this wire may be replaced by a printed circuit on a dielectric support according to known methods.

In order to record the best performance of the antenna according to the invention, the power centers are far apart from each other sufficiently and appropriately to avoid a maximum of interference.

To this end, and according to a further feature of the invention, two adjacent feeding centers are spaced from each other by a distance substantially equal to λ / 2.

Likewise, according to a further characteristic of the invention, the different biquads are connected, via their respective supply centers, to a coupler via a coaxial power supply cable.

The distance between the supply center of a radiating element and its reflector being the same for each of the biquads constituting the antenna according to the invention, the different reflectors will also be coplanar. Therefore, in a usual and preferred manner, the reflectors of the various biquads in question are merged by their edges into a continuous reflector forming a single reflector. This usually takes the form of a single panel configured to support these biquads.

Thus, according to another characteristic of the invention, the radiating elements are associated with a single reflector forming a support panel for all of these elements.

This or these reflectors are formed of a metal plate generally made of copper or aluminum. Steel, especially stainless steel or polychlorinated biphenyl ("PCB") can be used as well. In this case and in known manner, it may be advantageous to solder, for example copper to the coaxial cable orifice, orifice formed in this reflector so as to ensure a good physical and electrical connection.

The antenna according to the invention, thus conceived, can be implemented in horizontal or vertical rectilinear polarization. However, according to a particularly preferred mode of use, this antenna is used in vertical rectilinear polarization in which case the feeding centers of the biquads are aligned in a vertical, the longitudinal axis of the biquads being horizontal.

In this mode of use in vertical polarization, the antenna according to the invention makes it possible to obtain a main lobe of large aperture in the horizontal plane but weak in the vertical plane, accompanied by a large gain.

Thus, according to an advantageous characteristic of the invention, each main lobe of radiation has an opening substantially of 55 ° to 60 ° in the horizontal plane and substantially of 20 ° to 40 ° in the vertical plane, accompanied by a gain of 12 dBi at 16 dBi in particular from 12.5 to 14.5 dBi.

• deux biquads présente :
  1. a) dans le plan horizontal
     un angle d'ouverture du lobe principal de 57,7°, une direction du lobe principal de 0°, un lobe secondaire dont le niveau est situé à -21,3 dBi et un gain (amplitude du lobe principal) de 12,5 dBi, tel qu'illustré à la figure 1 en annexe,
  2. b) dans le plan horizontal
     un angle d'ouverture du lobe principal de 33,7°, une direction du lobe principal de 90°, un lobe secondaire dont le niveau est situé à -18,9 dBi et un gain de 12,5 dBi, tel qu'illustré à la figure 2 en annexe,
• quatre biquads présente :
  1. a) dans le plan horizontal
     un angle d'ouverture du lobe principal de 58,9 dBi, une direction du lobe principal de 0°, un lobe secondaire dont le niveau est situé à -18,9 dBi et un gain de 14,1 dBi, tel qu'illustré à la figure 3 en annexe,
  2. b) dans le plan vertical
     un angle d'ouverture du lobe principal de 21,8°, une direction du lobe principal de 90°, un lobe secondaire dont le niveau est situé à -13,1 dBi et un gain de 14,1 dBi, tel qu'illustré à la figure 4 en annexe.

In particular, the opening angle of the main lobe in the horizontal plane varies from 57 ° to 59 ° in the horizontal plane and from 20 ° to 35 ° in the vertical plane. For example, a 925 Mhz antenna according to the invention comprising:

• two biquads present:
  1. a) in the horizontal plane
     a main lobe opening angle of 57.7 °, a main lobe direction of 0 °, a secondary lobe with a level of -21.3 dBi and a gain (main lobe amplitude) of 12.5 dBi, as illustrated in figure 1 in the appendix,
  2. b) in the horizontal plane
     a main lobe opening angle of 33.7 °, a main lobe direction of 90 °, a secondary lobe with a level of -18.9 dBi and a gain of 12.5 dBi, as illustrated to the figure 2 in the appendix,
• four biquads present:
  1. a) in the horizontal plane
     a main lobe opening angle of 58.9 dBi, a principal lobe direction of 0 °, a secondary lobe with a level of -18.9 dBi and a gain of 14.1 dBi, as illustrated to the figure 3 in the appendix,
  2. b) in the vertical plane
     a main lobe opening angle of 21.8 °, a main lobe direction of 90 °, a secondary lobe with a level of -13.1 dBi and a gain of 14.1 dBi, as illustrated to the figure 4 in annex.

The antenna according to the invention has particularly advantageous characteristics resulting in both a large opening of the main lobe in the horizontal plane, a small opening in the vertical plane, a large gain and a low radiated power.

By way of example, the main radiation lobe in the horizontal plane of a quadruple biquad antenna according to the invention has, as mentioned above, an opening of approximately 60 ° (-3 dBi) conferring on it a effective range of not less than 400 m, sufficient aperture of approximately 20 ° to 400 m in the vertical plane and a maximum gain of 14,1 dBi so as to cover a geographical area over a distance greater than 400 m . In addition, the radiated power is only about +13 dBm in each direction.

The directional antenna according to the invention can find application in the field of GSM mobile telephony and / or transmission and reception of GPRS data. It can be used in particular for the implementation of a method of recovering an external signal, in particular GSM by means of a gain antenna, for example of the Yagi type, to convey this signal via a coaxial cable to an amplifier then to diffuse, by means of an antenna according to the invention, in the geographical area to be covered, in this case a geographical area of reduced size or pico-cell.

Thus, according to another of its features, the invention provides a device for implementing this method. This device, also hereinafter referred to as "pico-relay", consists of a mobile radiotelephone relay antenna for covering a small geographic area, of the kind comprising a mat having an upper portion and a lower portion, at least a high-gain, low-aperture directional antenna, hereinafter also referred to as the "upper antenna", being attached to said upper portion, characterized in that the lower portion of the mat comprises a directional antenna with high gain and large aperture according to the invention, hereinafter also referred to as "lower antenna".

The directional antenna mounted at the upper portion of the mat is preferably of the Yagi type in horizontal polarization but preferably in vertical polarization. This comprises a sufficient number of elements in the frequency band considered in particular 10 to 16 elements in the band 890-960 MHz. Generally, the opening of this upper antenna, at -3 dBi, varies from 10 ° to 15 ° in both the vertical and horizontal plane. On the other hand, when a gain increase is desired, several directional antennas of the above type will advantageously be placed at the upper portion of the mat in question.

According to another characteristic of the invention, the relay antenna comprises a repeater, usually of the pico-repeater type, connected to the upper antenna as well as to the lower antenna, which consists of a bidirectional amplifier for frequency coverage. envisaged for example the GSM 900 or GSM 1800 band.

This pico-receiver, commercially available, receives and amplifies, the mobile signal received from a base station of an operator and the reemet, via the upper antenna, to the lower antenna, according to the invention, which distributes it in the geographical area considered in this case a pico-cell of a few hundred meters in diameter. On the other hand, the amplification bandwidth is configurable for adaptation, if necessary to a different band.

In addition, in order to ensure energy autonomy, the relay antenna according to the invention advantageously comprises at least one solar panel, preferably a single panel, coupled to at least one energy accumulator battery.

Furthermore, the pico-relay according to the invention can be equipped with a surge arrester located at the level of the upper antenna so as to provide maximum security.

• la figure 1 est une représentation du diagramme de rayonnement dans le plan horizontal d'une antenne selon l'invention comprenant 2 éléments rayonnants biquad,
• la figure 2 est une représentation du diagramme de rayonnement dans le plan vertical d'une antenne selon l'invention comprenant 2 éléments rayonnants biquad,
• la figure 3 est une représentation du diagramme de rayonnement dans le plan horizontal d'une antenne selon l'invention comprenant 4 éléments rayonnants biquad,
• la figure 4 est une représentation du diagramme de rayonnement dans le plan vertical d'une antenne selon l'invention comprenant 4 éléments rayonnants biquad,
• la figure 5 est une vue schématique frontale d'une antenne selon l'invention comprenant 4 éléments rayonnants biquad fixés à un support,
• la figure 6 est une vue frontale de l'antenne à la figure 5,
• la figure 7 est une vue frontale d'une antenne relais de téléphonie mobile ou pico-relais comprenant l'antenne à la figure 5.

The invention will be better understood and other objects, features and advantages thereof will appear more clearly in the following explanatory description with reference to the accompanying drawings given solely by way of examples illustrating various embodiments of the invention. invention and in which:

• the figure 1 is a representation of the radiation pattern in the horizontal plane of an antenna according to the invention comprising two biquad radiating elements,
• the figure 2 is a representation of the radiation pattern in the vertical plane of an antenna according to the invention comprising two biquad radiating elements,
• the figure 3 is a representation of the radiation pattern in the horizontal plane of an antenna according to the invention comprising 4 biquad radiating elements,
• the figure 4 is a representation of the radiation pattern in the vertical plane of an antenna according to the invention comprising 4 biquad radiating elements,
• the figure 5 is a schematic front view of an antenna according to the invention comprising 4 biquad radiating elements fixed to a support,
• the figure 6 is a front view of the antenna at the figure 5 ,
• the figure 7 is a front view of a mobile or pico relay relay antenna including the antenna at the figure 5 .

EXAMPLE 1 ANTENNA at 925 Mhz

As represented in Figures 5 and 6 , the antenna according to the invention, the radiation patterns of which are illustrated in FIGS. Figures 3 and 4 , comprises a set of four radiating elements 1, biquad type that is to say, configured in a closed loop forming two equal squares in the same plane and united by a common vertex. These biquads 1 each consist of a bare and continuous copper wire with a diameter of about 2.5 to 3.5 mm, preferably 3 mm, each side of the squares having a length of 79 mm (1/4 waveform = 81 mm). On the other hand, the length of each biquad, that is to say the distance separating the two farthest vertices, is 230 mm. In addition, these biquads are isolated from each other by 180 mm (λ / 2 = 162 mm) which represent the distance separating two adjacent feed centers 2, the 4 feed centers being aligned along the straight line d shown in phantom interrupted.

The figure 5 also shows that the biquads are fixed on a panel 3 forming a reflector which consists of an aluminum plate 720 mm x 360 mm and a thickness of 2 mm. Moreover, each of these biquads, 48 mm away from this reflector 3, is connected, via its feed center 2, to a 5-way coupler for frequencies of the order of 890 to 960 MHz. , which is indicated in 4. This connection is provided by means of a coaxial cable 5 with a voltage impedance of 50 Ω, semi-rigid power supply cable covered with an electrically insulating material. In addition, these biquads are welded to this coaxial cable 5, the vertices furthest from each of them being themselves secured, if necessary to the reflector panel 3 by any means so as to stiffen the assembly.

EXAMPLE 2 PICO-RELAY at 925 Mhz

In a preferred embodiment of a pico-relay in the GSM 890-960 Mhz band, as shown in FIG. figure 7 , there is a generally cylindrical mast 6 and wood, for example with a diameter of 200 mm and a height of 12 m. At the upper portion of this mat are fixed 2 Yagi directional antennas each comprising 7 elements in the band 890-960 Mhz, whose gain is 15 dBi and whose opening is 2 x 10 ° in the vertical and horizontal. These Yagi antennas, of which an example is represented in 7 at the figure 7 , are mounted in vertical polarization and preferably by a ply of 2 antennas, to obtain a gain of the order of 18 dBi and connected by a 2-way coupler (not shown) of low loss. On the other hand, a lightning arrester 8, for example of COAXSTOP® type Franklin company is placed at the output of the coupler and connected to a conductor 35 mm ² section for earthing.

The figure 7 also shows a solar panel 9 (12 V, 50 W), preferably of Sunset type, and of dimensions (980 x 450 x 35) mm. This panel is fixed on a frame 10 with galvanized steel angle, inclined at 45 ° and maintained by two flanges 11 welded to the support. The set is positioned about one meter from the top of the post and oriented south-southeast.

There is also a sealed housing 12, generally of dimensions (500 x 500 x 200) mm, welded to a flat support supporting it and fixed on the mat by two flanges. This housing comprises, not shown, a pico-repeater, batteries (12 V, 32 Ah) with a capacity of 384 W of sealed lead-acid battery type, a solar regulator (12 V, 5A), a differential circuit breaker and a thermostatically controlled ventilation (12 V).

The selective band repeater, for example of the Chiki 903 C type originating from the Retemsa company, has an output power of 13 dBm with bidirectional amplification of 52 dBi in the 900 MHz GSM band.

In addition, the figure 7 shows, attached to the lower portion of the mast, an antenna 13 as described in Example 1, that is to say comprising four radiating elements 14 in vertical polarization, each biquad type, networked on a reflector 15 and vertically coupled. This antenna 13 is in fact isolated from Yagi antennas from a distance of 8 to 10 m to obtain 70 dBi.

The pico-relay thus elaborated was subjected to various tests which provided the following results:

a) Measurement of the electric field

Tests have shown that the electric field received at 100 m from the lower antenna according to the invention gives a satisfactory result of the order of 65 dBm for an antenna gain of 14.6 dBi. On the other hand, the electric field received at a distance of 5.5 km from the higher antennas Yagi and this, between the pico-relay and the base GSM relay antenna (or BTS, ie "Base" Transceiver Station or base transceiver station), is of the order of -75 dBm.

b) Measurement of energy consumption

The pico-repeater consuming only 800 m A at 12 V (10 W), a single solar panel (55, 12V) will be enough to ensure the autonomy of the pico-relay.

In the hypothesis of an optimum sunshine of 10h, the solar panel will accumulate 360 W of electrical energy. As the entire pico-relay consumes only 0.8 A h, a total of 230 W will be consumed in 24 hours leaving a reserve of 130 W.

The pico-relay according to the invention is used in particular to overcome the lack of GSM telephony in isolated geographical areas or white areas mainly located in rural areas, mountains and forests. This one is particularly advantageous because on the one hand its energy autonomy since it is powered by solar panel, the harvested energy being saved on battery and on the other hand its very low consumption that it is about radiated power or absorbed. Moreover, this pico-relay does not require any particular external maintenance.

Claims (15)

1. Directional antenna for the transmission and/or reception of audio and/or video signals, of the type comprising several identical antenna elements, supplied radio electrically by currents of substantially the same phase and amplitude, each antenna element comprising a radiating element formed of two quadrilaterals joined by a common apex, a power centre as well as an associated reflector, characterised in that it includes a coupling of at least two coplanar and separate radiating elements, each side of the quadrilaterals of a radiating element being parallel to the corresponding side of the other radiating element(s) of the coupling and in that the respective power centres are aligned according to a straight line that does not cut any quadrilateral.
2. Antenna set forth in claim 1, characterised in that each antenna element comprises a radiating element comprised of a continuous double loop taking the geometrical form of two squares located in the same plane, having a common apex and perimeter substantially equal to 2λ.
3. Antenna set forth in claim 2, characterised in that the double loop is accomplished using a metal wire or a printed circuit on a dielectric support.
4. Antenna according to one of claims 1 to 3, characterised in that the coupling comprises 2 to 8 radiating elements.
5. Antenna set forth in claim 4, characterised in that the coupling comprises 2 radiating elements.
6. Antenna set forth in claim 4, characterised in that the coupling comprises 4 radiating elements.
7. Antenna according to one of claims 1 to 6, characterised in that the alignment line of the power centres is orthogonal to the longitudinal axis of each of the radiating elements.
8. Antenna according to one of claims 1 to 7, characterised in that two adjacent power centres are separated one from the other by a distance substantially equal to λ/2.
9. Antenna according to one of claims 1 to 8, characterised in that the radiating elements are associated to a single reflector forming a support panel for the whole of the latter.
10. Antenna according to one of claims 1 to 9, characterised in that it is used straight-line vertical polarisation.
11. Mobile telephony relay antenna for the coverage of a geographical zone of reduced area, of the type comprising a mast presenting an upper portion and a lower portion, at least one high-gain small-aperture directional antenna being fixed to said upper portion, characterised in that the lower portion of the mast includes a high-gain large-aperture directional antenna according to one of claims 1 to 10.
12. Relay antenna set forth in claim 11, characterised in that the high-gain small-aperture directional antenna is an antenna of the Yagi type comprising from 10 to 16 elements.
13. Relay antenna set forth in claim 11 or 12, characterised in that it comprises a bidirectional amplifier of the pico-repeater type connected to the high-gain small-aperture directional antenna as well as to the high-gain large-aperture directional antenna.
14. Relay antenna according to one of claims 11 to 13, characterised in that it comprises at least one solar panel coupled to at least one energy accumulator battery.
15. Relay antenna according to one of claims 11 to 14, characterised in that it comprises a lightening arrester.

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