EP1872436B1 - Wide band dipole antenna - Google Patents

Description

The present invention relates to a broadband antenna of dipole type, more particularly an antenna for receiving television signals, in particular the reception of digital television signals on a portable electronic device such as a laptop, a PVA (Personal Assistant) or other similar device.

There is currently on the market equipment to receive digital terrestrial television or TNT on laptops or PCs. The reception of TNT signals on a portable computer makes it possible to benefit from the calculation power of the PC for the decoding of the flow of digital images. Most often, these devices are sold in the form of a housing with two interfaces, namely an RF (Radio Frequency) interface for connection to an indoor or outdoor VHF-UHF antenna and a USB interface for connection to the computer. Examples of this type are given in particular in the patent application US 2004/0263417 on behalf of MICROSOFT Corporation or in the patent US 6544075 on behalf of ACCTON Technology Corporation. However, these two documents describe a device comprising an independent antenna, most often a whip or loop type antenna, mounted on a USB box. The patent US2004 / 0145533 discloses a dipole antenna which comprises two arms which are housings which comprise electronic cards.

On the other hand, it has long been known to use dipoles as receiving antenna, see in particular the patent US 2002/0109639 . In general, a conventional dipole comprises two identical arms having a length substantially equal to λ / 4 and placed vis-a-vis. The arms are powered by a differential generator. This type of antenna has been studied since the beginnings of electromagnetism and is used in particular for UHF reception and even, more recently, in WLAN type wireless networks. Therefore, it is also known to use dipole antennas whose arms are rotatably mounted to be folded into radio telephony, see in particular the patent US 5,561,437 .

The present invention therefore uses the concept of the dipole type antenna to realize a compact broadband antenna covering the whole of the UHF band and associated with an electronic card that can connect to a portable device using, in particular, a USB type connector.

Thus, the present invention relates to a broadband dipole antenna comprising a first and a second differential-fed conductive arm, the first and the second arms being rotated relative to one another at a zone of articulation located at one end of each arm and having a connection element.

According to the invention each arm has a generally rectangular shape with a curved profile at the area of articulation.

According to a first embodiment, the first arm has the shape of a housing in which is inserted an electronic card.

According to a second embodiment, the first arm comprises an upper face covering the electronic card. At this upper face may be associated two side faces.

The profiles are preferably complementary so as to fold the two arms against each other and to obtain a compact antenna, easily transportable.

According to a characteristic of the present invention, the electronic card comprises, at one end, a connection port for the supply of the antenna and at the other end a connection port to an electronic device. Preferably, the connection port to the electronic device is a USB connection port. In addition, the electronic card includes circuitry for processing television signals.

• Figure 1 est une vue en perspective de côté d'un premier mode de réalisation d'une antenne conforme à la présente invention.
• Figure 2 est une vue en perspective de l'antenne de figure 1.
• Figure 3 représente des courbes d'adaptation S11 en fonction de la fréquence pour l'antenne de la figure 2, respectivement avec et sans circuit d'adaptation.
• Figure 4 représente un abaque de Smith de l'antenne de figure 2 avec et sans circuit d'adaptation.
• Figure 5 représente des courbes donnant l'efficacité de l'antenne en fonction de la fréquence avec ou sans circuit d'adaptation.
• Figure 6 est un diagramme de rayonnement en gain de l'antenne de figure 2.
• Figure 7 est une représentation identique à la représentation de la figure 1 dans laquelle le second bras prend différentes positions.
• Figure 8 représente des courbes donnant l'adaptation en fonction de la fréquence pour les différentes positions du bras 2 représentées à la figure 7.
• Figure 9 représente des courbes donnant l'adaptation de l'antenne en fonction de la fréquence pour les différentes positions du bras 2 représentées à la figure 7 lorsque l'antenne est suivie d'un circuit d'adaptation.
• Figure 10 représente les diagrammes de rayonnement en gain de l'antenne de figure 7, pour les différentes positions du bras 2.
• Figure 11 représente schématiquement un circuit d'adaptation prévu en sortie d'antenne.
• Figure 12 est une vue schématique en perspective d'un second mode de réalisation d'une antenne conforme à la présente invention.
• Figure 13 et figure 14 représentent respectivement des courbe s donnant l'adaptation en fonction de la fréquence et des courbe s donnant l'efficacité de l'antenne en fonction de la fréquence, respectivement pour l'antenne de la figure 12 par comparaison avec l'antenne de la figure 2.
• Figure 15 est une vue en perspective schématique d'un troisième mode de réalisation de la présente invention.
• Figure 16 et figure 17 représentent respectivement des courbes donnant l'adaptation en fonction de la fréquence et l'efficacité de l'antenne en fonction de la fréquence pour l'antenne de la figure 15 par comparaison avec l'antenne de la figure 2.
• Figure 18 représente une vue en perspective schématique d'un quatrième mode de réalisation de la présente invention, et
• figure 19 est une vue schématique d'une carte électronique utilisée dans la présente invention.

Other characteristics and advantages of the present invention will appear on reading the description of various embodiments, this description being made with reference to the attached drawings in which:

• Figure 1 is a side perspective view of a first embodiment of an antenna according to the present invention.
• Figure 2 is a perspective view of the antenna of figure 1 .
• Figure 3 represents S11 matching curves as a function of frequency for the antenna of the figure 2 , respectively with and without matching circuit.
• Figure 4 represents a Smith chart of the antenna of figure 2 with and without adaptive circuit.
• Figure 5 represents curves giving the efficiency of the antenna as a function of frequency with or without matching circuit.
• Figure 6 is a radiation pattern in gain of the antenna of figure 2 .
• Figure 7 is a representation identical to the representation of the figure 1 wherein the second arm takes different positions.
• Figure 8 represents curves giving the adaptation as a function of the frequency for the different positions of the arm 2 represented in FIG. figure 7 .
• Figure 9 represents curves giving the adaptation of the antenna as a function of the frequency for the different positions of the arm 2 represented in FIG. figure 7 when the antenna is followed by an adaptation circuit.
• Figure 10 represents the radiation patterns in gain of the antenna of figure 7 , for the different positions of the arm 2.
• Figure 11 schematically represents an adaptation circuit provided at the antenna output.
• Figure 12 is a schematic perspective view of a second embodiment of an antenna according to the present invention.
• Figure 13 and Figure 14 respectively represent curves giving the adaptation as a function of the frequency and curves giving the efficiency of the antenna as a function of the frequency, respectively for the antenna of the figure 12 compared with the antenna of the figure 2 .
• Figure 15 is a schematic perspective view of a third embodiment of the present invention.
• Figure 16 and figure 17 respectively represent frequency matching curves and antenna efficiency as a function of frequency for the antenna of the antenna. figure 15 compared with the antenna of the figure 2 .
• Figure 18 is a schematic perspective view of a fourth embodiment of the present invention, and
• figure 19 is a schematic view of an electronic card used in the present invention.

To simplify the description in the figures, the same elements bear the same references.

We will first describe with reference to Figures 1 and 2 , a first embodiment of a compact broadband antenna usable for receiving digital terrestrial television on a portable computer according to the present invention.

As shown schematically on Figures 1 and 2 this dipole antenna essentially comprises a first conducting arm 1 and a second conducting arm 2, the two arms being connected to each other via a hinge zone 3 located at one end of the each arm.

More specifically, the arm 2 is constituted by a rectangular plate made of a metallic, metallized or other conductive material and has a length close to λ / 4 at the central operating frequency, namely close to 112 mm for operation in the UHF band (band between 460 and 870 MHz). This arm 2 has a rectilinear portion 2a and a curved portion 2b allowing the connection at the zone 3 to the other arm 1. The arm 1 has a shape such that it can be used at least as a cover for an electronic card which will be described in detail below.

More specifically, the arm 1 shown in FIGS. Figures 1 and 2 has a rectangular portion 1a forming a housing in which can inserting said electronic card and it is extended by a curved portion 1b forming a progressive flare which allows the energy to be radiated gradually and, in this way, promotes adaptation over a wider frequency band. The length of the arm 1 is also substantially equal to λ / 4. The arm 1 is made of a metallic conductive material, metallized or otherwise.

As shown on the figure 1 the arms 1 and 2 have nearly identical total lengths, i.e., a length of 118.7 mm in the embodiment shown. More precisely, the rectilinear part has a length of 70 mm and a width of 25 mm. In addition, the arm 1 in the form of housing has a height of 10 mm. The two arms 1 and 2 are connected to one another at a hinge zone 3 which comprises at 3a a connection element for connecting the antenna to a generator or receiver circuit for processing electromagnetic signals. . In order not to disturb the electromagnetic operation of the antenna, the hinge zone comprises connection elements made using material relatively transparent to the radio waves while the electrical connection is provided by a metal wire, a coaxial or similarly connected to the generator circuit or the electromagnetic signal processing receiver. In order to avoid a short circuit between the metal wire and the arm 2, an opening is necessary in the arm 2.

As mentioned above, the two arms 1 and 2 are made of a conductive material, in particular metal. Thus, they can be made from metal plates by cutting these plates.

The antenna of the figure 2 having the dimensioning given above, was simulated using a commercial electromagnetic software (IE3D). In these simulations, the antenna is assumed in the air and consists of a conductive material having good conductivity (σ> = 5.10 ⁷ S / m). The results of the simulations are given on the curves of Figures 3 to 6 which mainly concern a simulation made on the antenna alone and a simulation made when the antenna is connected to an adaptation circuit such as that which will be described with reference to the figure 11 .

The figure 3 represents the impedance matching curves of the antenna of the figure 2 with and without adaptive circuit. On these curves, it can be seen that the adaptation cell makes it possible to obtain a good adaptation over the entire UHF band, namely the frequency band between 460 - 870 MHz while the curve obtained without an adaptation circuit makes it possible to get a good adaptation on a more restricted frequency band. This is confirmed on Smith's chart of the figure 4 .

The figure 5 represents the curves giving the efficiency of the antenna with and without adaptation circuit. The curves obtained confirm the previous results and show that an antenna efficiency greater than 80% is obtained over the entire UHF band in the case of the use of a matching circuit.

The radiation pattern of the figure 6 is a radiation pattern in gain that confirms that the antenna of the figure 2 works like a dipole.

As mentioned above, the arm 2 of the antenna is rotatably mounted relative to the arm 1, so as to orient the antenna for optimal reception. On the figure 7 , various positions of the arm 2 with respect to the arm 1 have been represented, namely a position in which the angle α between the two arms is equal to 0 ° referenced 20, a position in which the angle α between the two arms is substantially equal to 30 ° referenced 21, a position in which the angle α that the two arms make is substantially equal to 45 ° referenced 22, a position in which the angle α between the two arms is substantially equal to 60 ° referenced 23 and a position in which the angle α between the two arms is substantially equal to 90 ° referenced 24.

To know the influence of the inclination of the arm 2 relative to the arm 1, simulations were performed for the different positions of the arm. The results of the simulations are given respectively on the figures 8 , 9 and 10 .

The figure 8 represents the different curves giving the impedance matching as a function of the frequency for the different positions of the arm 2. It will be noted that the antenna is naturally adapted for high frequencies when the value α of the angle is small and vice versa. versa. In fact, the electric field E can easily be established at low frequencies when the angle α = 0 ° respectively at high frequencies when the angle α = 90 °.

The figure 8 gives the results for the antenna alone. In this case, the antenna is not adapted to the entire UHF frequency. If an adaptation cell such as the one shown in figure 11 In this case, we obtain the adaptation curves of the figure 9 . According to these curves, the upper band is well adapted with a coefficient S11 of less than -6 dB for all the positions of the arm 2 and the lower band is well adapted with S11 less than -6 dB for the positions of the arm 2 between 0 ° and 60 °.

On the other hand, we have shown on the figure 10 the radiation patterns at a frequency of 660 MHz for the different positions of the arm 2 of the antenna. The radiation patterns are inclined as a function of the angle of inclination α. This inclination optimizes the reception of the digital television signal.

An adaptation cell that can be used in the present invention is shown schematically in FIG. figure 11 . In this figure, the antenna A is connected to the cell constituted by an inductance L and a capacitance C. The antenna is connected in series with the capacitor C which is connected to a low noise amplifier LNA, while the inductor L is mounted between the ground and the point of connection of the antenna to the capacitor C.

To obtain a good adaptation, the value of the capacitance C and the inductance L are such that C = 5 pF and L = 15 nH. This adaptation cell has been optimized for an inclined arm with an angle α equal to 60 °.

We will now describe with reference to figures 12 , 13 and 14 , a first embodiment of the present invention. As shown on the figure 12 , in this case the antenna comprises an arm 2 identical to the arm 2 of the figure 2 and an arm 1 formed only by the upper face 12 of the housing forming the arm 1 of the figure 2 . In this case, we obtain the adaptation and efficiency curves represented respectively on the Figures 13 and 14 . The curves of the figure 13 which compares the impedance matching of the antenna of the figure 12 with the antenna of the figure 2 shows that we still get a good adaptation on the entire UHF band. The curves of the figure 14 shows that, in this case, the efficiency of the antenna of the figure 12 is less than that of the antenna of the figure 2 in the lower band due to the elimination of the side and bottom walls of the arm 1 of the figure 2 .

We will now describe with reference to Figures 15, 16 and 17 , a third embodiment of the present invention. In this case, the arm 2 is identical to the arm 2 of the antenna of the figures 2 and 12 while the arm 1 has only the upper face 1c and the two side faces 1d. In this case, the arm 1 forms a cover fitting on the electronic card. The results of the simulation represented on the figures 16 and 17 show that this embodiment gives results that are substantially identical to the embodiment of the figure 2 . This embodiment has the advantage of being easier to industrialize than the embodiment of the figure 2 .

We will describe now, with reference to figure 18 , another embodiment of an antenna according to the present invention. In this case, the arm 10 consists of an element having the shape of a rectangular housing whose upper surface is stamped so as to obtain a portion 10c. This stamped portion allows to receive the arm 20 when the latter is folded for transport. The arm 20 has a shape corresponding substantially to a half-ellipse. The dimensions of the arms 10 and 20 are substantially identical and correspond to approximately λ / 4 at the desired operating frequency. As in the case of the other figures, the arm 10 and the arm 20 are interconnected at an interconnection zone 30 so as to be rotatable relative to each other.

We will now describe with reference to the figure 19 an embodiment of an electronic card according to the present invention, the arm 1 of the antenna forming a cover or a housing for this electronic card. This electronic card may include all the integrated circuits necessary for the processing of a digital television signal. As shown on the figure 14 this card 100 thus comprises a low noise amplifier 101 connected to the output of the antenna at the rotation zone 3 or 30 of the antenna, the signal from the LNA amplifier is sent to a tuner 102 and then to a demodulator 103 connected to a USB interface 104. The electronic card being provided with a USB connection port 105. If necessary, the electronic card may be provided with a shielding of the RE part.

It is obvious to those skilled in the art that other types of connection port, allowing to connect to an electronic device, can be used, such as, for example, the formats used for memory cards (Compact Flash , SD, XD ...)

It is possible to make this electronic card so that it has a length of between 70-80 mm and a width of between 15-25 mm so that it can be easily inserted into the arm 1 forming a housing, as shown on the figure 2 .

It is obvious that the electronic card described above is only one example of an electronic card that can be used in the case of the present invention. According to alternative embodiments, this card can also be integrated into a conventional USB key used for the transport of personal data, photos or music.

Claims (6)

1. Broadband dipole antenna comprising
   a first (1,10) and a second (2,20) conductor arm, differentially supplied,
   an electronic board (100),
   the first arm (1) having the shape of a box (10) wherein the electronic board is inserted,
   the first (1) and second (2) arms being mounted in rotation with respect to each other, in an articulation zone (3) located at one of the extremities of each of the arms and comprising a connection element, characterised in that
   each of the first and second arms (1,21) has a general rectangular shape with a curved profile (1a) in the articulation zone so that the antenna operates in broadband.
2. Antenna according to claim 1, characterised in that the first arm comprises an upper face (1c) and two side faces.
3. Antenna according to one of claims 1 to 2, characterised in that the first (1,10) and the second (2,20) arms each have a length equal to λ/4 at the operating central frequency of the antenna.
4. Antenna according to one of claims 1 to 3, characterised in that the first (1,10) and the second (2,20) arms have complementary profiles enabling them to be folded into each other.
5. Antenna according to one of claims 1 to 4, characterised in that the electronic board (100) comprises, at one end, a connection port for supplying the antenna and at the other end a connection port configured to be connected to an electronic appliance.
6. Antenna according to claim 5, characterised in that the connection port is configured to be connected to the electronic appliance is a USB connection port (105).

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