FR2847725A1 - Miniaturised mobile phone radio equipment has circuit board linked to patch antenna constructed with ground plane extension of flexible printed circuit - Google Patents

Abstract

A miniaturised mobile phone radio equipment has a circuit board linked to a transmit/receive slotted (28) patch (12) antenna made by folding three sections (26a, b, c) of a flexible printed circuit with feed (14) connection track (32) and ground plane (22) connection (18).

Description

"'-A" Electronic device comprising an antenna and a ground circuit

  printed on a flexible circuit "The invention proposes a portable electronic device of the type which comprises: - a plate which carries electronic components - an antenna for transmitting and / or receiving signals to / from a remote electronic device ; and - a flexible printed circuit on at least one face of which a layer of conductive material, forming an extension of a ground circuit of the component-holding plate, is printed, and of the type of which the antenna comprises an emitting element overall plan, a power supply element which connects the transmitter element to a transmission / reception circuit of the component-holder board and a ground conductor element which connects

  the transmitter element to the ground circuit of the component-carrying plate via the flexible printed circuit.

  The antennas of current portable electronic devices, in particular portable radiotelephones, are arranged inside the outer casing of the device for aesthetic reasons and so as to be protected from attack

external, in particular shocks.

  The use of antennas called "PIFA" (for Planar Inverted F Antenna) has spread in the radio telecommunications field to equip devices with integrated antenna (s). There is shown diagrammatically in FIG. 1 an antenna 10 of the "PIFA" type according to a known embodiment of

the state of the art.

  This antenna 10 comprises a generally planar transmitting element 12 from which the electromagnetic waves are emitted, a first conductive supply element 14 by which the waves to be emitted, or received by the emitting element 12 are transmitted from, to an electronic component. of the component-carrying plate 16 of the electronic device, or PCB (for Printed Circuit Board), and a second conductive element 18, called "ground", which connects the emitter element 12 to the circuit

  mass of the component-holder plate 16.

  The efficiency of such an antenna 10 is determined on the one hand by the components of the component-carrying plate 16, but

  also by the surface of the earth circuit of the component carrier plate 16.

  The current trend, particularly with regard to portable radiotelephones, is to reduce the external dimensions of the radiotelephone. The dimensions of the component carrying plate 16 are therefore also reduced to dimensions

maximum around 40 mm.

  The reduction in the dimensions of the component bearing plate 16 causes a reduction in the performance of the antenna for certain frequency ranges, in particular for the frequency range close to 900 MHz, which is most often

  used for portable radiotelephones.

  To overcome this drawback, it has been proposed to use a flexible printed circuit on which an extension of the

  component holder circuit 16.

  The power supply element 14 is then produced by a coaxial cable which connects the transmitter element 12, which is of conventional structure, to the electronic components of the

component holder plate 16.

  However, the use of a coaxial cable proves to be particularly expensive, and the means for making the connection between on the one hand the extension of the ground circuit and the component-carrying plate 16 and on the other hand the connection between the extension of the ground circuit and the emitting element 12, prove to be particularly complex to produce, which implies

  also an increase in the cost of manufacturing the radiotelephone.

  The object of the invention is to propose a portable radiotelephone for which the structure of the assembly formed by the extension of the ground circuit and the antenna is simplified, and

therefore less expensive.

  To this end, the invention provides a portable electronic device of the type described above, characterized in that s the emitting element, the mass conducting element and the supply conducting element each consist of a layer of conductive material which is printed on at least one side of a

  section of the flexible printed circuit.

  According to other characteristics of the invention, - a connecting track of the power supply element with the transmission / reception circuit is printed on at least one face of a section of the flexible printed circuit so as to be electrically isolated from the extension of the earth circuit; the printed circuit comprises a first section on which the transmitter element of the antenna is printed, a second intermediate section on which the supply conductive element and the ground conductive element of the antenna are printed, and a third section on which the extension of the ground circuit and the connecting track are printed; - The three sections of the flexible printed circuit consist of three consecutive sections of a flexible strip; the connecting track, the emitting element, the supply conducting element and the mass conducting element consist of zones of the same layer of conductive material which is printed on the same face of the printed circuit, and what they are connected to each other when they are printed; - A free edge of the third section comprises means of connection to complementary connection means carried by the component-carrying plate; - a first part of the extension of the ground circuit is printed on the whole of a first face of the third section, and a second part of the extension of the

B 1025 "

  ground circuit is printed on a part of the second opposite face of the third section; - The connecting track is printed on the second face of the third section; - The flexible printed circuit is curved so that the first section extends horizontally above and vertically away from the third section in a position in which it is held by a support element made of insulating material; the transmitting element comprises at least one slot of predetermined shape which extends in the plane of the element

transmitter.

  Other characteristics and advantages of the invention

  will appear on reading the following detailed description for the

  understanding of which reference will be made to the appended figures in which: - Figure 1 is a schematic perspective representation of an assembly formed by the component-carrying plate and a PIFA type antenna, according to an embodiment in accordance with the teachings of the 'state of the art; - Figure 2 is a view similar to that of Figure 1, showing an antenna and an extension of the ground circuit according to the invention; - Figure 3 is a plan view of the flexible printed circuit shown in Figure 2, on which are printed the section of the ground circuit and the antenna; - Figure 4 is a section along a longitudinal plane

  vertical of the flexible printed circuit shown in Figure 2.

  We will adopt the orientation from back to front as the longitudinal direction and from left to right, referring to the

figure 1.

  In the description which follows, identical elements,

  similar or analogous will be designated by the same numbers

reference.

  FIG. 2 shows an antenna 10, of the PIFA type and an electronic component holder plate 16 of a portable electronic device, in particular a radiotelephone of the GSM type. As mentioned above, to compensate for the reductions in the efficiency of the antenna 10, due to the reduction in the surface of the component-carrying plate 16, an extension 22 of the ground circuit of the carrying plate -components 16 connect the ground conductor element 18 of the antenna 10 to the ground circuit of the

component holder plate 16.

  This extension 22 consists of a layer of is conductive material which is printed on a flexible printed circuit 24 which can be bent at will, so that it is possible to reduce the size of the extension 22 inside the radiotelephone. To avoid using additional elements for connection of the antenna 10 to the electronic component of the component-holding plate 16, and of connection of the antenna 10 to the extension 22, and in accordance with the invention, each element of the antenna 10, that is to say the transmitting element 12, the supply conducting element 14 and the ground conducting element 18 consists of a layer of conductive material which is printed

  on at least one side of the flexible printed circuit 24.

  According to a preferred embodiment of the invention, the flexible printed circuit 24 consists of a horizontal strip

  flexible which extends longitudinally.

  The extension 22, as well as the various elements of the antenna 10 are distributed over this flexible longitudinal strip of

  so as to form three consecutive sections 26a, 26b and 26c.

  The transmitter element 12 of the antenna 10 is printed on the whole of one face of a first front section 26a of the flexible printed circuit 24. In addition, the transmitter element 12 comprises at least one groove or slot 28 which s 'extends in the plane of the transmitter element 12 and which is of predetermined shape, to allow the antenna 10 to operate for different frequency ranges. The supply conductive element 14 and the mass conductive element 18 are printed on the same face of the second intermediate section 26b of the flexible printed circuit 24, and they are printed so as to be electrically insulated one

the other.

  The extension 22 is printed on the third rear section 26c of the flexible printed circuit 24 and, according to a preferred embodiment of the invention, it is produced in two portions 22a, 22b which are each printed on one of the upper or lower faces of the third rear section 26c, which makes it possible to have a large surface area of the extension 22, while retaining relatively small dimensions of the third

rear section 26c.

  Furthermore, the two portions 22a, 22b of the extension 22 are electrically connected to each other by needles, commonly called "vias" 30 of conductive material which pass through the third rear section 26c of the printed circuit

flexible 24.

  The connection between the component-carrying plate 16 and the printed circuit 24 is made at a free edge of the third rear section 26c and, according to a preferred embodiment, the connection is made at the longitudinal edge

  rear of the third rear section 26c.

  The connection is made by connection means 20 which consist of first connection means which are carried by the rear edge of the third rear section 26c and which cooperate with complementary connection means which

  are carried by the front edge of the component-holding plate 16.

  According to a preferred embodiment of the invention, the means 20 for connecting the extension 22 to the component carrier plate 16 consist of a connector of the ZIF type (for "Zero Insertion Force"), which is carried by the front edge of the plate component holder 16, and into which the free longitudinal edge of the third rear section 26c is introduced. However, the connection between the third rear section 26c and the component-holding plate 16 can be made by any other means such as for example by bonding using a conductive adhesive,

io or by welding.

  The supply conductive element 14 and the ground conductive element 18 being printed on the second section 26b of the flexible printed circuit 24, they are arranged between the

  extension 22 and the transmitting element 12 of the antenna 10.

  Thus, the mass conducting element 18 consists of a longitudinal strip of conducting material, one end of which is connected to the emitting element 12 and the second end of which

is connected to extension 22.

  The supply conductive element 14 also consists of a strip of conductive material which extends longitudinally rearwards from the emitter element 12. However, the supply conductive element 14 must be connected to the electronic component of the component-holder plate 16, and the connection between the component-holder plate 16 and the flexible printed circuit 24 is made at the rear longitudinal end of the third rear section 26c of the flexible printed circuit 24. Thus, the extension 22 is arranged between the connection means 20 with the component-carrying plate 16 and the conductive element

supply 14.

  This is why, according to another aspect of the invention, and as can be seen in particular in FIG. 3, a connecting track 32 is printed on one face of the third rear section 26c of the flexible printed circuit 24. The track connection 32 consists of a longitudinal strip of conductive material which extends over the third rear section 26c from the rear end of the supply conductive element 14, to the rear longitudinal edge of the third rear section 26c, so as to to be isolated

electrically from extension 22.

  Here, the connecting track 32 crosses the extension 22, dividing it into two parts. The connecting track is then surrounded by the two parts of the extension, which makes it possible to achieve its electromagnetic isolation. However, according to an alternative embodiment not shown, the connecting track 32 is arranged on

  along a longitudinal edge of the third rear section 26c.

  Thus, the extension 22 consists of a first portion 22a which is printed on a part of a face of the third rear section 26c of the flexible printed circuit 24, the other part of this face being covered by the connecting track 32, and in a second portion 22b which is printed on the whole of a second face of the third rear section 26c of the printed circuit

  flexible 24 which is opposite the first face.

  According to a preferred embodiment of the invention, the transmitting element 12, the supply conducting element 14, the ground conducting element 18, the connecting track 32 and a portion 22a of the extension 22 each consist of a area of the same layer of conductive material which is printed on

  the same face 24a of the flexible printed circuit 24.

  Thus, during the printing of this layer of conductive material, these elements are connected together, which avoids the use of additional connection means, or an additional step to connect these elements, this results

  a significant reduction in the manufacturing cost.

  According to an embodiment of the invention shown in Figures 2 and 4, the flexible printed circuit 24 is curved in the manner of a U, so that the first section 26a and the third rear section 26c of the flexible printed circuit 24 s 'extend horizontally at a distance from each other, the first re section 26a extending above the third rear section 26c. Here, as shown in FIG. 4, the printed circuit 24 is curved so that the face of the first front section 26a, on which the emitter element 12 is printed, is opposite the face of the third rear section 26c on which

  the connecting track 32 is printed.

  According to another alternative embodiment of the invention, the printed circuit 24 is curved differently, so that the face of the first front section 26a which carries the transmitter element 12 and the face of the third rear section 26c which carries the track

link 32 are opposite.

  In addition, here, the third rear section 26c extends entirely horizontally. However, the third rear section 26c can also be curved so that its longitudinal dimensions inside the radiotelephone are reduced. For the efficiency of the antenna 10 to be constant whatever the use of the radiotelephone, the element must

  transmitter 12 is stationary relative to the extension 22.

  This is why, as can be seen in FIG. 4, a support element 34, which is made of an insulating material, is interposed vertically between the first front section 26a and the third rear section 26c so as to maintain the curvature of the printed circuit 24. Furthermore, according to a preferred embodiment of the invention, the printed circuit 24 is curved so that the first front section 26a, and the third rear section 26c extend horizontally, in parallel with one

to the other.

  Since the antenna 10 and the extension 22 are produced on the same flexible printed circuit 24, it is possible to size and / or position the extension 22, the power supply element 14, the inside of the radiotelephone. ground conductor element 16 and the slots 28 so as to guarantee optimum efficiency of the antenna 10, independently

  dimensions of the component-holding plate 16.

  It is then possible to produce the various elements of the radiotelephone, in particular the component-carrying plate 16 and the flexible printed circuit 24 on which the antenna 10 and the extension 22 are printed, in the form of separate modules which can be manufactured independently. from each other so that they can then be assembled according to the characteristics

wanted from the radiotelephone.

  In addition, the method of printing certain elements of the radiotelephone on a printed circuit, whether flexible or not, is relatively more precise than the method of machining a metal plate, for example

antenna 10.

  Thus, the transmitting element 12 of an antenna 10 produced in accordance with the invention may comprise one or more slots 28, which makes it possible to operate the antenna 10 in different frequency ranges and thus to increase its performance. The invention has been described as comprising a flexible printed circuit 24 on both sides of which the extension 22 is printed. However, it will be understood that the invention can also be applied to a flexible printed circuit on a single face of which the extension 22 is printed, without departing from the field of

the invention.

  In addition, the flexible printed circuit has been described as consisting of three aligned sections. However, it will be understood that the flexible printed circuit can also consist of sections which are not aligned, and which for example form an "L", one branch of which is formed by the first section 26a on which the emitting element 12 is printed. and the other branch of which is formed by the third section 26c on which the

  extension 22, the second section 26b connecting the other two.

he

Claims (10)

  1. Portable electronic device of the type which comprises - a plate (16) which carries electronic components; s - an antenna (10) for transmitting and / or receiving signals to / from a remote electronic device; and - a flexible printed circuit (24) on at least one face of which a layer of conductive material, forming an extension of a ground circuit (22) of the component carrier plate (16), is printed, and of the type of which l antenna (10) comprises a generally planar transmitter element (12), a supply conductor element (14) which connects the transmitter element (12) to a circuit for transmitting / receiving the component-holder board (16) and a ground conductor element (18) which connects the emitter element (12) to the ground circuit of the component carrier plate (16) via the flexible printed circuit (24), characterized in that the emitter element ( 12), the earth conductive element (18) and the supply conductive element (14) each consist of a layer of conductive material which is printed on at least one face of a section of the circuit flexible print (24).   2. Electronic device according to the preceding claim, characterized in that a connection track (32) of the supply conductive element (14) with the transmission / reception circuit is printed on at least one side of a section (26c) of the flexible printed circuit (24) so as to be electrically isolated from the   extension of the earth circuit (22).   3. Electronic device according to any one of   previous claims, characterized in that the circuit   printed comprises a first section (26a) on which is printed the transmitter element (12) of the antenna (10), a second intermediate section (26b) on which are printed the supply conductive element (14) and the 'ground conductor element (18) of the antenna (10), and a third section (26c) on which are printed the extension of the ground circuit (22) and the track link (32).   4. Electronic device according to the preceding claim, characterized in that the three sections (26a, 26b, 26c) of the flexible printed circuit (24) consist of three consecutive sections flexible band.   5. Electronic device according to one of claims 3   or 4, characterized in that the connecting track (32), the emitting element 1o (12), the supply conducting element (14) and the ground conducting element (18) consist of zones of the same layer of conductive material which is printed on the same side of the printed circuit, and in that they are connected between them when they were printed.   6. Electronic device according to one of claims 3 to   , characterized in that a free edge of the third section (26c) comprises connection means (20) to means   additional connections carried by the component carrier plate (16).   7. Electronic device according to one of claims 3 to   6, characterized in that a first part of the extension of the ground circuit (22) is printed on the whole of a first face of the third section (26c), and in that a second part of the extension of the ground circuit ( 22) is printed on a   part of the second opposite face of the third section (26c).   8. Electronic device according to the preceding claim, in combination with claim 2, characterized in that the connecting track (32) is printed on the second face of the third section (26c).   9. Electronic device according to any one of   Claims 4 to 8, characterized in that the printed circuit   flexible (24) is curved so that the first section (26a) extends horizontally above and vertically away from the third section (26c) in a position in which it is held by a support element (34) made in insulating material. 10. Electronic device according to any one of   previous claims, characterized in that the element   s transmitter (12) has at least one slot (28) of predetermined shape which extends in the plane of the transmitter element (1 2).