FR3058000A1 - ANTENNA DEVICE - Google Patents

Abstract

The present invention relates to an antenna device connected to the chassis of a modem of a radio frequency transceiver. This device is characterized in that it comprises at least two planar antennas oriented substantially perpendicularly to one another and whose ground planes are connected, said antennas each comprising on a first face of a first portion (2) of a dielectric substrate (5) a first conductive surface (1) forming an antenna and connected by a strand (3) to a connection (6) for connection to coaxial cable signal transmission means (7) and on the second face and in a second portion (4) of the substrate (5) a second conductive surface forming a ground plane located on the back of the strand (3).

Description

Holder (s): JAMING CHRISTOPHE, MAURICE CLAUDE, MICHAUX BENOIT, SIEBEN MICHEL, TOUSSAINT MADELEINE.

Extension request (s)

Agent (s): CABINET BLEGER-RHEIN-POUPON.

FR 3 058 000 - A1 (54) ANTENNA DEVICE.

The present invention relates to an antenna device i to the chassis of a modem of a radiofrequency transceiver.

This device is characterized in that it comprises at least two planar antennas oriented substantially perpendicular to one another and whose ground planes are connected, said antennas each comprising on a first face of a first part (2) of a dielectric substrate (5) a first conductive surface (1) forming an antenna and connected by a strand (3) to a connection (6) for connection to signal transmission means of the coaxial cable type (7) and on the second face and in a second part (4) of the substrate (5) a second conductive surface forming a ground plane located on the back of the strand (3).

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Antenna device

The present invention relates to an antenna device intended to equip radio frequency transmission / reception boxes in particular in the frequency domains of the UHF bands, used in wireless data transmission networks, for example in the context of mobile telephony. These frequencies are suitable for the transport of data of all kinds, including of course the voice but more particularly the more significant data such as texts, images and videos notably accessible via local and general networks of the internet type.

In this regard, the transceiver devices include modems, a designation now customary for modulator-demodulator devices which transform the analog signals picked up by the antennas into digital data usable by a downstream processing system, or which convert the digital data into output. of these multi-purpose processing systems into analog signals ready to be transmitted by the antennas.

More specifically, the connection to cellular networks in a given territory obviously depends mainly on the existence of transmission / retransmission devices, then secondarily on their density (number) and location (location), these parameters having in particular an impact on the quality of final signal reception. This quality depends of course also and ultimately on the nature of the data (weight) and finally on the relative positioning of transmitters and users equipped with their terminals (cell phones, tablets or computers, GSM / UMTS operator boxes, retransmission devices WIFI etc.).

Thus, by taking the example of relay antennas scattered over a territory, and which these operators use, they each belong to a cell which is a well-defined geographical area notably in relation to the ranges of the transmitters and the information capacities to convey. Unsurprisingly, the cells are larger in the countryside as opposed to the urban grid. This looser network has the consequence that it can remain, in general far from cities, geographic areas which are not properly covered by mobile networks, and cause access difficulties, especially as soon as the data weighs a certain weight. In the worst-case scenario, there continue to exist today regions with very little coverage, which are referred to as "gray areas" or "gray areas".

The evolution is in the direction of a constant increase in broadcasting services and a continuous increase in bit rate, certainly allowing more data to be conveyed to the greatest number, but which turns out to be concomitantly technologically much more demanding for this. which concerns all the technological links of the chain, at the level of both transmission and reception. In other words, mobile data is growing rapidly, which is roughly parallel to the number of people who consume the content associated with them, implying a constant technological effort to keep the equation as it is. The race for mobile internet is a perfect illustration of this.

However, the UHF band, already implemented in a more successful manner on other continents, is an adapted frequency range which is therefore already commonly used, and which is moreover anticipated for the extension of mobile broadband, in particular because that it allows a quality of reception of information which corresponds to current expectations. It is therefore a question of increasing the frequency band traditionally allocated to cellular data.

The current reflection to convey more and better data is not complete, however, if it stops at the normative and institutional aspect and the technical mesh which follows via the cells. In other words, reflection is largely unsuccessful if it confines itself to considering what results directly or indirectly from a state or para-state policy which comes "from above", that is to say possibly from political will and also technical capacity at the broadcast stage. It must be carried out in conjunction with thinking at the other end of the technical chain, at the reception level. The aim is in particular to aim to optimize the components which participate in the reception, for example at the level of the terminals, mobile or not. The idea is in a word to improve the receiver systems in order to overcome as much as possible the shortcomings noted during the transmission.

In this regard, the present invention provides an innovative antenna device which considerably improves the performance of the antenna on reception, conveying to the modem arranged downstream of the antenna analog signals restoring the cellular data with a much higher amplitude and quality. to existing antennas.

To this end, and this secondarily generates many other technical advantages which will appear in the rest of this description, the antenna device of the invention, conventionally connected to the chassis of a modem of a radiofrequency transceiver, is such that it comprises at least two planar antennas oriented substantially perpendicular to each other and whose ground planes are connected, said antennas each comprising on a first face of a first part of a dielectric substrate a first conductive surface forming an antenna and connected by a strand to a connection for connection to signal transmission means of the coaxial cable type, and on the second face and in a second part of the substrate a second conductive surface forming a ground plane situated on the back of the strand.

The double orientation of the antennas makes it possible to pick up the signals in perpendicular directions, which has the effect of considerably widening the scanning field: the device of the invention works in practice in a way that is both omnidirectional, which is the preferred mode , and default directive. When this does not work in omnidirectional mode, some optimization can nevertheless be carried out by setting in directive mode.

According to a preferred configuration, the first surface has an elliptical appearance, this shape making it possible to make the antenna device of the invention work naturally in the two desired positions, perpendicular to one another, with characteristics of equivalent reception. In practice, the dimension along the major axis of the ellipse is between 1.5 and 2.5 times the dimension along the minor axis, constituting a relative dimensioning adapted to said optimization for the capture of signals in the two dimensions.

In the configuration of the invention, the strand connecting the active antenna to the connecting cable is oriented parallel to the major axis of the ellipse, preferably coaxial with said axis, or perpendicular to the major axis. The strand passes through the second part of the substrate, on the side opposite to the ground plane, that is to say in a neutral location, which does not emit due to the existence of mass at this level. Only the first elliptical conductive surface, calibrated for the wavelengths envisaged in the cellular data transmission / reception applications, is active in this regard.

According to one possibility, the second conductive surface in the second part of the insulating substrate can be rectangular, even square, a practical shape for implementing the superposition of the masses, if necessary. More precisely still, the sides of the second rectangular surface are parallel or perpendicular to the axes of the ellipse, which contributes to optimizing the superposition of the ground planes when the planar antennas are arranged perpendicular to one another.

According to a possible configuration, for each planar antenna of the invention, said first and second conductive surfaces have no overlap but are close to or tangent in projection on a surface parallel to the mean plane of the insulating substrate, although located on both sides opposite of the substrate.

More precisely, they develop well on two different faces and therefore cannot touch each other, but if they are projected on a plane parallel to the planar antenna, they are close to or in contact with each other tangentially. or almost tangential.

Preferably, according to the invention, the two planar antennas are identical, so that the scanning in the two orientations can be done in a completely equivalent manner, for frequencies themselves identical or almost identical.

When the invention has a pair of antennas arranged perpendicular to each other, the two antennas are oriented, for example when they are fixed

to the chassis, of so that their plans of masses overlap without contact . They are since then related contact with the frame , without touch to not

modify the mass surface and its relation to the strand. The thickness of the mass is however increased by this particular configuration, helping to improve the overall efficiency of the ground plane, which plays an essential role because the currents flowing in the antennas produce currents induced in the ground planes, creating in turn fields which are added to those created by antenna currents. The resulting field ends up approaching that which is created by a dipole, giving the whole a corresponding antenna efficiency. Hence the importance of conductive metallic planes such as those which are used as ground planes in the invention.

According to an alternative configuration, the two perpendicular planar antennas can be arranged on the same dielectric substrate comprising a single ground plane, the dimensions of their first surfaces, that is to say the antennas themselves, and their strands, being substantially identical. . Such a solution therefore only involves a single ground plane which is shared between the two antennas.

According to yet another variant, the antennas can be fixed to at least one device allowing their rotation relative to the chassis. This can for example be carried out in a conventional manner with brooms, coals etc. sliding on a collector secured to the antenna. It is then easy to optimize reception by modifying their respective setting.

Preferably, according to the invention and for the envisaged applications, the planar antennas have the following characteristics:

- input impedance: 50 ohms

- maximum input power: 30 W

- bandwidth between: 600 MHz and 2700 MHz

- yield: 5dBi.

The impedance is linked to that of the connecting cable, and the bandwidth depends on the application, in this case it is the range of UHF frequencies and L and S bands used for the transmission of cellular mobile data. .

Advantageously, under these conditions and for these applications, the dimensions of the antenna have the following characteristics:

- major axis of the first elliptical surface: between 90 mm to 100 mm

- minor axis of the ellipse: between 45 mm to 50 mm

- width of the strand: between 3 mm to 5 mm

- length of the strand: between 50 mm to 60 mm

- dimension of the sides of the second rectangular surface parallel to the major axis of the ellipse: between 50 mm to 60 mm

- dimension of the sides of the second rectangular surface perpendicular to the major axis of the ellipse: between 50 mm to 60 mm.

The antenna device of the invention then operates, in connection with the modem, in a conventional manner with the sending by the modem of a brief signal intended for the relay antennas of the operators which are located in the vicinity, to access the communication network. .

A gateway is then established between them, based on an IP communication protocol, a MAC physical address and a GSM number. In the event of signal attenuation, the antenna device of the invention allows operational efficiency without common measure with the devices which exist to date.

The invention will now be described in more detail, with reference to the appended figures, for which:

- Figure 1 shows a perspective view of one of the antennas constituting the antenna device of the invention, seen from the antenna side;

- Figure 2 is a perspective view of the same antenna, viewed from the ground plane side; and

- Figure 3 shows a view of a double antenna according to the invention, in the version in which the two perpendicular planar antennas are arranged on the same dielectric substrate.

Referring to Figure 1, the active part of each planar antenna consists of a first conductive surface of elliptical shape (1) disposed on a first part or portion (2) of an insulating substrate (5). The conductive surface (1) can simply be a layer of copper of the chosen shape, placed on an insulating plate (5) for example of insulating resin, the manufacture of the antenna then obeying well-known techniques for manufacturing printed circuits, in this case a double-sided printed circuit.

The strand (3) of the antenna develops axially in the extension of the major axis of the ellipse in the direction and, for most if not all of its extension, in a second part (4) of the substrate (5) , on the back of which extends the second conductive surface or ground plane (10) of said antenna (see in Figure 2). At its distal end of the elliptical surface (1) of the antenna, the strand (3) is soldered at (6) to a coaxial cable (7) which is connected to a modem processing the signal inputs / outputs respectively from / and to the antenna. Coaxial cables conventionally have an impedance of 50 Ohm to which the antenna impedance must be tuned. The core of the coaxial cable is welded to the strand (3), while the twisted braid surrounding said core is welded to the ground plane (10).

In the configuration shown in Figure 1 (which is not to scale), the first elliptical surface (1) of the antenna has a length (along the major axis) of approximately 92 mm, while the width ( along the minor axis) is ίο the order of 45 mm. The strand (3) extends over approximately 56 mm and has a width of the order of 4 mm.

The dimensions of the ground plane (10) relative to the second part (4) of the insulating substrate (5) appear mainly in Figure 2 (and are shown for information by a transverse line in Figure 1).

It is in particular visible, in FIG. 1, that the strand (3) has a length such that it "crosses" the

all of the surface of the plan of mass , on the face opposite, the welding point (6) being in the neighbourhood immediate of the border of said plan of mass (10) distal to

the elliptical surface (1) of the antenna.

The two figures show that the ground plane (10) and the first elliptical surface (1) of the antenna have no overlap zone, so that the antenna does not emit at the level of the strand (3) " covered ”by the ground plan (10).

The antenna device of the invention preferably operates with two antennas, for example identical to that which is shown in Figures 1 and 2 arranged perpendicular to each other. It should be noted that the second part (4) of the substrate (5) receiving on one side most of the strand (3) and on the other the ground plane (10) is such that its shape is not only rectangular but square, allowing very complete overlap and superimposition when two antennas of this type are associated perpendicularly and in close proximity to each other in the chassis of the modem.

In the version of Figure 3, the two antennas are arranged perpendicularly on the same substrate (5), in this case a single printed circuit (PCB) provided on a first face with two elliptical surfaces (1, 1 ') connected π

to strands (3, 3 ') which "cross" a ground plane (10) which is on the second face of the PCB. We find again the idea of perpendicularity of the two antennas, namely the two conductive surfaces (1, 1 ') and the access to two strands (3, 3'), in this case parallel, on the same side of the substrate insulator (5). The antennas (1, 1 ') and the strands (3, 3') are of the same surface or of approximate surfaces. The characteristics mentioned above on the welding of a cable and / or the existence of a connector are always true and implemented in exactly the same conditions. In particular, the first part (2) of the PCB is indeed the one which sees the first conductive surfaces forming the elliptical antennas (1, 1 ′), while the second part (4) of this substrate in the form of PCB comprises a side the strands (3, 3 ') and on the other the second conductive surface forming the single ground plane (10).

The shape and the dimensions given allow good electrical compatibility of the antenna with the transmission connections between it and the modem, notably preserving a correct standing wave rate (TOS). From the point of view of the impedance compatibility calculations, it may be thought that the two antennas forming the antenna device of the invention are envisaged independently of one another, in particular also because they are each connected to the chassis of the modem by its own connection (by plug or cable): in reality, their proximity allowing the superimposition of the ground planes, connected via said chassis, allows a combined operation of the two antennas in particular due to the interactions of the electric fields generated by the different parts of the two antennas.

The association of antennas, which results in omnidirectional operation by allowing a much larger scanning field by picking up signals in two directions, also increases the spectrum of possible operations since, as already mentioned, a directional operating mode is also possible, if the gain of the combined configuration is insufficient.

Optimization can then also be carried out by setting the directional antenna by any means, including motorized and automated means via a collector and brushes.

In general, if the shapes described with reference to the examples illustrated lead to excellent results which make them preferential shapes, they are not limitative of the invention, the structures, materials and shapes of the antenna, of the plane and mass etc. can change while remaining within the scope of the present invention.

Claims (15)

1. Antenna device connected to the chassis of a modem of a radiofrequency transceiver, characterized in that it comprises at least two planar antennas oriented substantially perpendicular to one another and whose ground planes are connected, said antennas each comprising on a first face of a first part ( 2) a dielectric substrate (5) a first conductive surface (1, 1 ')) forming an antenna and connected by a strand ( 3, 3 ') to a connection (6) for connection to signal transmission means of the coaxial cable type (7) and on the second face and in a second part (4) of the substrate (5) a second conductive surface ( 10) forming a ground plane located on the back of the strand (3, 3 '). 2. Device antenna according to the claim previous, characterized in that the first surface (1, 1 ') looks good elliptical. 3. Device antenna according to the claim previous, characterized in that the dimension along the major axis of the ellipse is between 1.5 and 2.5 times the dimension along the minor axis. 4. Antenna device according to one of claims 2 and 3, characterized in that the strand (3) is oriented parallel to the major axis of the ellipse, preferably coaxial with said axis, or perpendicular (3 ') to the major axis. 5. An antenna device according to one of the preceding claims, characterized in that the second conductive surface (10) in the second part (4) of the insulating substrate (5) is rectangular, even square. 6. antenna device according to one of claims 2 to 5, characterized in that the sides of the second rectangular surface (10) are parallel or perpendicular to the axes of the ellipse. 7. antenna device according to one of the preceding claims, characterized in that said first and second conductive surfaces (1, 1 ′, 10) do not have an overlap but are close to or tangent in projection on a surface parallel to the mean plane of the insulating substrate (5). 8. Antenna device according to one of the preceding claims, characterized in that the two antennas are oriented so that their ground planes (10) are superimposed without contact. 9. Antenna device according to one of the preceding claims, characterized in that the two planar antennas are identical. 10. Antenna device according to one of claims 1 to 7, characterized in that the two perpendicular planar antennas are arranged on the same dielectric substrate (5) comprising a single ground plane (10), the dimensions of their first surfaces (1, 1 ') and their strands ( 3, 3 ') being substantially identical. 11. Antenna device according to one of the preceding claims, characterized in that the two antennas are oriented respectively one vertically and the other horizontally. 12. Antenna device according to one of the preceding claims, characterized in that the two antennas are fixed on at least one device allowing their rotation relative to the chassis. 13. Antenna device according to one of the preceding claims, characterized in that the planar antennas have the following characteristics: - input impedance: 50 ohms - maximum input power: 30 W - bandwidth between: 600 MHz and 2700 MHz - efficiency: 5dBi 14. Antenna device according to one of claims 2 to 13, characterized in that the dimensions of the antenna 5 have the following characteristics: - major axis of the first elliptical surface: between 90 mm to 100 mm - minor axis of the ellipse: between 45 mm to 50 mm - width of the strand: between 3 mm to 5 mm 10 - length of the strand: between 50 mm to 60 mm dimension of sides of the second surface rectangular parallel at tall axis of the ellipse: between 50 mm to 60 mm dimension of sides of the second surface 15 rectangular perpendicular to the long axis of the ellipse: between 50 mm and 60 mm. 1/1