EP0736924A1 - Portable receiver with an antenna - Google Patents

Abstract

The receiver is mounted in a flat case which contains an LCD flat TV screen (20) with an RF integrated circuit mounted behind. Two electrically conductive lid sections (4,5), one on either side of the box, swing on pivots (6,7) to form an antenna when opened. The lids sections are parallel to the screen and are opened to provide good screen viewing. A fixed triangular antenna section lies over the top of the circuit and forms a yagi array which provides connection to the integrated circuit.

Description

The present invention relates to a portable receiver provided with an antenna for the reception of electromagnetic waves, comprising a housing in which an electronic circuit is placed.

Such a receiver is for example a radio receiver or a flat screen television receiver, or a flat screen teletext receiver, for example provided with a liquid crystal screen.

A particular antenna is known from document JP-A-56 144 645. In general, the reception diagram of a symmetrical antenna, for example a so-called YAGI antenna, is itself symmetrical, with two lobes separated by two hollows, this is ie two directions of reception of waves for which the gain of the antenna is zero. The arrangement described by this document uses two antennas of the so-called "butterfly" type, each made of a pair of flat and triangular strands and placed flat along two opposite insulating faces of a box of which the other four faces are metallic. , in order to obtain an invariably stable reception in all directions, and to take advantage of the presence of the metal faces to form a reflective element for the antenna.

An object of the invention is to obtain a perfectly omnidirectional reception diagram, with a high gain.

• deux plaques dites principales électriquement conductrices, chacune attachée le long d'une ligne à l'extérieur et de part et d'autre du boîtier, de façon pratiquement symétrique,
• et deux plaques dites parallèles, qui sont pratiquement triangulaires avec leurs pointes tournées l'une vers l'autre et qui sont contenues dans un même plan symétriquement l'une par rapport à l'autre, et qui sont respectivement reliées, par un de leurs côtés, au côté tourné vers le boîtier de chacune des plaques principales,

et une articulation est prévue au niveau de la ligne d'attache de chaque plaque principale et, en position d'utilisation, les plaques principales et les plaques parallèles font un angle entre elles.To this end, a receiver according to the invention is remarkable in that, for use in the so-called UHF frequency range, the antenna comprises:

• two so-called electrically conductive main plates, each attached along a line on the outside and on either side of the housing, in a substantially symmetrical manner,
• and two so-called parallel plates, which are practically triangular with their points facing one another and which are contained in the same plane symmetrically with respect to each other, and which are respectively connected, by one of their sides, to the side facing the housing of each of the main plates,

and an articulation is provided at the line of attachment of each main plate and, in the position of use, the main plates and the parallel plates form an angle between them.

The invention is therefore based on the idea of subdividing each of the strands of a "butterfly" antenna into two parts articulated with respect to each other, and of placing the housing between the two most distant parts. one from the other, these parts then appearing as elements of the housing.

Thus the omnidirectional character is improved, and in addition this arrangement makes it possible to fold the plates in front of or behind the housing, to reduce the dimensions of the receiver when it is not in use.

Preferably, the distance, measured along the antenna plates, between the ends, the furthest from each other, of the two plates is of the order of a wavelength λ of a frequency to receive.

With an antenna located inside a box, a length equal to λ would lead to a box that is too bulky, while such a length becomes possible with the arrangement according to the invention, and the results are thus better because 'a "butterfly" antenna receives a wider frequency band when it is full-wave than when it is half-wave.

Advantageously, the practically triangular parallel plates have an asymmetrical design with respect to a horizontal axis.

This allows better operation when the housing is tilted.

In a particular embodiment, a parallel plate is connected to a main plate via a plate connector making an angle both with the main plate and with the connection plate.

This makes it possible to "plug" the troughs of the directional diagram even better.

The main plates and the housing advantageously have, in a direction parallel to the attachment line of a plate, practically the same maximum dimension.

In one embodiment, the plates are made of plastic, and are covered with a flexible metallized sheet.

Such a flexible metallized sheet is capable of ensuring continuity at the level of the joints, by bending when the joint is played, or even may by itself constitute a hinge.

A portable receiver according to the invention is advantageously an image receiver provided with an image screen.

In a particular embodiment, the image screen is placed between the tips of the practically triangular parallel plates.

These aspects of the invention as well as other more detailed aspects will become more clearly apparent from the following description of an embodiment constituting a nonlimiting example.
Figures 1 and 2 schematically represent a receiver according to the invention, seen respectively from the front and from above. Figure 3 shows a top view of a variant.

The portable image receiver 1 illustrated in the figures comprises a box 8 in which an electronic circuit 11-16 is placed. This housing 8, which could as well have any shape, is here practically flat and rectangular. It is practically symmetrical with respect to a plane of symmetry 19 perpendicular to its large faces, and perpendicular to the plane of the drawing sheet.

The housing 8 is provided with an image screen 20 (FIG. 2), for example with liquid crystals, which occupies part of its large flat face which is turned downwards in the figure.

The receiver is intended for the reception of waves in the frequency range called UHF, and in particular for the reception of teletext broadcasts.

It is provided with an antenna which comprises two plates 4 and 5, electrically conductive. These two plates are arranged on either side of the housing 8 and attached in a practically symmetrical manner with respect to this housing 8, and with respect to the plane of symmetry 19. The plates 4 and 5 here form an angle, the apex of which S is behind the screen, for an observer located in front of the screen, this arrangement being visible in FIG. 2, where the planes of the plates 4, 5 are perpendicular to the drawing sheet.

The distance between the ends 21 and 22, the most distant from each other, of the plates 4 and 5 is of the order of a wavelength λ of the central frequency of the range of frequencies to be received, measured by following the surface of the plates between points 21 and 22.

The antenna further comprises two plates 2, 3 called parallel which are placed parallel to the flat housing 8 and electrically and mechanically connected to the first plate 4 and to the second plate 5, respectively.

One can also imagine an arrangement of the same elements in which the box 8 would be turned over recto-verso with respect to the position which it occupies in FIG. 2, that is to say that the screen would be turned upwards. the figure, the housing being placed above the plates 2 and 3, the top S then being in front of the screen.

The liquid crystal screen 20 is located near the plates 2, 3, but it does not play the role of a ground plane, because it is not a good conductor for the frequencies in play. does it approximate a role of directing element, in the sense of this word in the yagi antennas. Similarly, in order not to disturb the operation of the antenna, the electronic circuit in the housing 8 is divided into several subsets 11, 12, 13, 14, 15, 16, the ground planes of which are electrically connected to each other via inductors 161, 112, 114, 134, 145.

The parallel plates 2 and 3 have a roughly triangular design (Figure 1). The triangles are asymmetrical, in other words they are not isosceles. For example, the point to the right of the plate 2 and the point to the left of the plate 3 in FIG. 1 are higher than the middle of the plates and of the housing. This asymmetry is not always necessary. Instead of triangular plates, semi-circular or semi-elliptical plates could be used without making much difference, such forms being comparable to triangular "blunt" forms.

An electrical link to the electronic circuit can be connected to the antenna at a point 9 near the tip of the parallel plate 2 which faces the other parallel plate 3, and at a point 10 near the tip of the plate parallel 3 which faces the other parallel plate 2. In practice, an impedance adapter balun of a known type (not shown) is connected between the points 9 and 10 of the antenna, and the electrical connection to the the electronic circuit can therefore be connected at only one of the points 9 or 10. The tuner connected to one of these points is for example the element 11.

The antenna may further comprise (FIG. 2) a connection plate 17 disposed between the plates 4 and 2 and which connects them electrically and mechanically. Another electrically conductive connection plate 18 is arranged in the same way between the plates 3 and 5, which it connects mechanically and electrically. These plates make with the plates 2, 3 an angle of 90 ° and with the plates 4, 5 an angle of approximately 45 °, in the position which is shown, but which is adjustable as will be explained below.

The main plates 4 and 5, as well as the connection plates 17, 18 are for example rectangular and they have a height approximately equal to that of the housing.

One could also imagine for example main trapezoidal plates, or also semi-circular plates (connected to the connection plates along a vertical diameter), with however slightly degraded characteristics in the latter case.

The two plates 4 and 17 (or the two plates 5 and 18) can be rigidly fixed to one another. However, it is preferable to provide electrically conductive joints 6 and 7 respectively between the two adjacent plates 4 and 17 and between the two adjacent plates 5 and 18. This makes it possible to adjust the angle between the plates 4 and 17, or 5 and 18, and also to fold the plates for transporting the receiver.

In another arrangement which is illustrated in FIG. 3, the triangular antenna parts 2 and 3 are placed in front of the housing, on either side of the screen 20. Furthermore, the connection parts 17 and 18 are absent . Again, screen 8 could be turned up. Electrically conductive joints 6 and 7 are provided between the two adjacent plates 4 and 2 and the two adjacent plates 5 and 3 respectively.

The plates 17, 2 (or 18, 3) can be made of a single sheet, for example of aluminum, folded. In the case where no articulation 6 (or 7) is provided, it is even the set of plates 4, 17, 2 (or 5, 18, 3) which can be made of a single sheet folded. The metal plates can be sheathed in plastic or painted to improve their appearance.

Alternatively, the plates and the joints can be made of plastic, the plates being covered with a flexible metallized sheet, for example glued to the plastic plates.

Claims (9)

Portable receiver provided with an antenna for the reception of electromagnetic waves, comprising a box in which an electronic circuit is placed, characterized in that, for use in the frequency range called UHF, the antenna comprises: - two so-called electrically conductive main plates, each attached along a line to the outside and on either side of the housing, in a practically symmetrical manner, - And two so-called parallel plates, which are practically triangular with their points facing one another and which are contained in the same plane symmetrically with respect to each other, and which are respectively connected, by one of their sides, on the side facing the housing of each of the main plates, and an articulation is provided at the line of attachment of each main plate and, in the position of use, the main plates and the parallel plates form an angle between them. Portable receiver according to claim 1, characterized in that the distance, measured along the antenna plates, between the ends, the most distant from each other, of the two plates is of the order of one wavelength of the frequency to receive. Portable receiver according to one of claims 1 or 2, characterized in that the substantially triangular parallel plates each have an asymmetrical design with respect to a horizontal axis. Portable receiver according to any one of the preceding claims, characterized in that the main plates and the housing have, in a direction parallel to the line of attachment of the plates to the housing, substantially the same maximum dimension. Portable receiver according to any one of the preceding claims, characterized in that a parallel plate is connected to a main plate via a connection plate making an angle both with the main plate and with the connection plate. Portable receiver according to any one of the preceding claims, characterized in that the plates are made of plastic, and are covered with a flexible metallized sheet. Portable receiver according to any one of the preceding claims, characterized in that it is an image receiver provided with an image screen. Portable receiver according to claim 7, characterized in that the substantially triangular parallel plates are placed behind the receiver. Portable receiver according to claim 7, characterized in that the substantially triangular parallel plates leave sufficient space between their tips to accommodate the image screen therein.

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