FR2724263A1 - ANTENNA USED FOR THE TRANSMISSION OR RECEPTION OF A RADIOFREQUENCY SIGNAL, A REMOTE CONTROL TRANSMITTER AND RECEIVER AND A REMOTE CONTROL SYSTEM FOR VEHICLE INCORPORATED - Google Patents

Abstract

The present invention relates to an antenna comprising for transmitting or receiving a radio frequency signal in a remote control transmitter or receiver, such as a radio frequency remote control for access to a motor vehicle. The first part (21, 31), called primary, consists of a conductive track made for example in microstrip technology and is physically connected to the receiver (20, 30). The second part (22, 32), called secondary or also “tuning pattern”, is arranged relative to said first part (21, 31) so as to perform an impedance transformation and / or to produce a better pattern. electromagnetic radiation for the antenna as well as better gain. The invention also relates to a receiver and a remote control system incorporating such an antenna.

Description

The present invention relates to an antenna used for transmitting or

  receiving a radio frequency signal, a transmitter and a remote control receiver, and a vehicle remote control system incorporating it. It applies to the field of remote controls

  radio frequencies for access to a motor vehicle.

  Such remotes have many advantages over remote controls

  infrared. Indeed they are not directives that is

  that is, it is not necessary for the user to direct the transmitter to the receiver to operate

  the opening of the vehicle doors.

  In addition, the radiofrequency link is not necessarily stopped by the presence of a wall or any other

  another obstacle between the transmitter and the receiver.

  Moreover, the range of a radio frequency remote control is of the order of twice the range of an infrared remote control for transmitting power and substantially equivalent power. Finally, from the point of view of the installation in the vehicle, it is not necessary for the receiver to be in a visible position from the outside of the vehicle, which may constitute an advantage especially with respect to

  problems with vehicle theft.

  By using a technology in the frequency spectrum included in the band 100MHz 1Ghz that is to say around 500MHz, the average wavelength (in the air) of the emitted signal is 60cm. 1/4 of this length

wave is 15cm.

  The realization of a quarter-wave antenna, in particular of such a receiving antenna intended to be used in the receiver of the remote control therefore requires obtaining for the antenna a magnitude

  characteristic of the order of 15cm.

  In the state of the art, a whip antenna located outside the vehicle is conventionally used. This type of antenna requires a connection and a wiring due to the distance of the antenna with respect to the receiver which weighs substantially at the same time the

  complexity and cost of the receiving facility.

  This is why solutions have been proposed in which the antenna is integrated in a window of a vehicle. This type of realization is certainly more aesthetic but the problem of the connection and the length of the wiring son that are needed remains

the same.

  It has also been proposed to use an insert, sometimes called an overhead, which is constituted by a coil which is welded on a coplanar circuit such as a printed circuit of the transmitter (or receiver) incorporating it, and which one uses the best

radiation performance.

  However this use of a reported element causes difficulties of mechanical implantation increased, not conducive to industrial production in large series, and a larger footprint in the housing of the emitter (or receiver) inducing

  in particular a greater thickness of said housing.

  Given the characteristic length of the receiving antenna, which is as we have seen in the order of 15 cm, it has appeared possible to realize the receiving antenna in microstrip or planar technology in the type of application located in the that is to say,

  for frequencies of the order of 500MHz.

  The problem related to the connection and wiring length disappears since the antenna can be placed advantageously in the same housing receiver. In addition this type of antenna is easily achievable industrially in that it involves making conductive tracks, for example copper according to a method well controlled by the skilled person. Moreover, the calculation of the impedances is easy and allows an effective adaptation between the antenna thus constituted by the copper tracks on the one hand and the input of the receiver on the other hand. However, such antennas used in the abovementioned frequency range have weak characteristics, both in gain and in width of the diagram.

of radiation.

  The present invention aims to solve

  prior art problems mentioned above.

  Indeed it proposes an antenna, such as an antenna used in the transmitter or the receiver of a radio frequency remote control, this transmitter, respectively this receiver, being made on a printed circuit placed in a closure housing, the latter being made in

  a moldable material such as a plastics material.

  The invention is characterized in that the antenna comprises two parts in cascade: - a first part, called primary, constituted by at least one conductive track made for example in microstrip technology, which is physically connected to the transmitter, respectively to the receiver, via two terminals; and a second part, called secondary, which is not physically connected to the transmitter or to the receiver, and which is arranged relative to said first part so as to carry out an impedance transformation to make an adaptation between the transmitter and the propagation medium, respectively between the propagation medium and the receiver, and / or to produce a better electromagnetic radiation diagram and a better gain

for the antenna.

  The antenna according to the invention has the advantage of being of sufficiently small size to be housed entirely in the receiver closure box,

  while having good reception performance.

  Moreover this antenna is simple of realization and adapts well to the constraints of industrial manufacture

  in large series. Finally, it is cheap.

  According to other characteristics of the invention, taken separately or in combination: the antenna primer is produced using microstrip or coplanar technology on a first face of said printed circuit; the secondary of the antenna is made in microstrip or coplanar technology on a second face of said printed circuit so as to be focused on the primary; the secondary is made in the form of at least one conductive track engraved on the housing of

  closing so as to be focused on the primary.

  the secondary of the antenna is made in the form of at least one conductive track which is embedded in the closure housing so as to be focused on the

primary.

  the secondary is made in the form of at least one conductive track disposed on an adhesive label intended to be glued to the housing of

  closing so as to be focused on the primary.

  is made on a second printed circuit disposed inside the closure housing parallel to the first printed circuit on which is disposed the primary as well as the electronics of the transmitter, respectively of the receiver, said second printed circuit being arranged relative to to the circuit board carrying the primary so that the

  secondary focus on the primary.

  It will be appreciated that, in all possible embodiments, the first and second portions of the antenna are located relative to one another so as to achieve impedance matching, i.e.

  desired, hence its name of reason for agreement.

  The invention also relates to a transmitter and a remote control receiver incorporating an antenna as defined above. Finally, it relates to a remote control system incorporating such a transmitter or a

such receiver.

  Other features and advantages of the present invention will appear on reading the

  description which follows with reference to the drawings

  appended which are: In Figure 1: several possible embodiments of the primary antenna according to the invention; In Figure 2: two possible embodiments of an antenna according to the invention considered in schematic view; In FIG. 3: a method of fixing the secondary of the antenna according to the invention, via a

  adhesive label stuck on a remote control box.

  In Figure 4, a possible embodiment of the

  secondary antenna according to the invention.

  The following description is intended for

  illustrate the principle of the invention and should in no way be construed as limiting the scope. In particular, the antenna which is the subject of the invention is subsequently presented as a receiving antenna used in a radiofrequency remote control receiver, but, by virtue of the reciprocity theorem of antenna theory, the principle of the invention stay fully

  applicable to a transmitting antenna.

  In the four views of FIGS. 1 (a) to 1 (d), there are shown four possible embodiments, in microstrip technology or equivalent, of a conventional antenna that is to say comprising only a part and not two. In these four figures, the reference 10 denotes the circuit of a remote control receiver which comprises in particular a reception and processing electronics, and which will not be described in more detail in the

description below.

  The receiver circuit has two terminals 12 and 14 for connection to an antenna outside the circuit. The receiver circuit is implanted on a not shown electronic substrate which also carries a conventional antenna made of microstrip technology or equivalent. In Figure l (a) the antenna is a doublet antenna which has two branches respectively 11 and 13 respectively connected to terminals 12 and 14 of the receiver circuit. These are located close to each other, and on both sides of an angle of the circuit 10 of the receiver. Each branch 11 and 13 is bent at right angles as it leaves terminals 12 and 14, each being arranged in a direction parallel to a given side of the receiver circuit.

along this one.

  In FIG. 1 (b), in which the same elements as in FIG. 1 (a) bear the same references, the antenna is a doublet antenna whose two branches 11 and 13 run along the same side of the receiver circuit 10 ,

but in opposite directions.

  In Fig. 1 (c), a loop antenna 15 is connected to both terminals 12 and 14 of the receiver circuit 10. The loop is oriented clear of the receiver circuit, as opposed to the antenna shown in FIG. 1 (d) on which the same elements as in FIG. 1 (c) bear the same references, and on which the loop 15 is closes around the receiver circuit 10. All the radiating elements or antennas consisting of a single part and shown in Figures l (a) to l (d) differ from each other by their characteristics such as

radiation and gain in particular.

  However none of these antennas, taken alone, having revealed good enough characteristics for our application, it was imagined to use a second radiating element which would form the secondary of a two-part antenna whose primary would be constituted by a first radiating element such as one

  of those shown in Figures l (a) to l (d).

  Thus, both the primary and secondary of the antenna in two parts object of the invention can be made according to any one of the embodiments presented above, or in any other mode

known to the skilled person.

  The physical principle of the invention is similar to the principle used in an antenna intended for very long-range telecommunications, such as a parabolic antenna which consists of a primary source such as a horn antenna placed at the focus of a parabolic reflector constituting the secondary of the antenna, so that the radiation emitted by the primary source is transmitted with characteristics defined by the secondary, that is to say by the reflector. These features are related to the diagram

  of radiation and the gain of said reflector.

  The specificity of our application, whose purpose is to realize an antenna for the reception of a control signal emitted by a vehicle remote control transmitter, which is fully integrable in the receiver housing, is described below with regard to

Figures 2, 3 and 4.

  FIG. 2 (a) schematically shows a rectangular parallelepiped, a receiver 20 mounted on a substrate or printed circuit 23, on which is disposed a first radiating element of the type of a whip antenna 21 such that the one described more

  in detail above with reference to Figure l (b).

  The presence of a second radiating element 22 or 24 disposed respectively above or below the printed circuit 23, so as to be tuned with said first radiating element 21, defines an antenna according to the principle of the invention, it is possible to ie consisting of two parts 21,22 respectively 21,24 tuned to each other to present, from the point of view of the single antenna thus formed, performance in terms of radiation pattern and gain that are much higher to those that would present a conventional antenna consisting of the first radiating element 21 if

was used alone.

  The first radiating element 21 is also called primary and the second radiating element 22 (respectively 24) is also called secondary

  the antenna in two parts 21,22 (respectively 21,24).

  In FIG. 2 (b), in which the same elements as in FIG. 2 (a) bear the same references, the primary is constituted by a loop antenna whose structure has been described in more detail with reference to FIG. 1 (c), and which is connected to two terminals of the receiver

provided for this purpose.

  In fact all possible combinations are possible for the structure of the primary and secondary respectively, the choice being determined by the desired performance of the antenna in two parts that one wishes to achieve, and that one dimensioned according to characteristics imposed by the intended application. It is conceivable to make the secondary 22 on the printed circuit directly, next to the primary 21. If the printed circuit is a double-sided circuit can also be considered to achieve the secondary 24 on the face of the printed circuit opposite to that is located the

primary 21.

  According to a preferred embodiment of the invention, the secondary is made on a different medium of the printed circuit 23 on which is located the

primary 21.

  This support may be constituted by a second printed circuit carrying the secondary 22 (respectively 24) and which is held above (respectively below) said printed circuit 23, or first printed circuit, on which is the primary 21. The second circuit The printed circuit may be maintained in a predetermined position with respect to the first printed circuit, and at a determined distance therefrom, for example by securing them by means of screwed columns, as well as

is known to those skilled in the art.

  The two printed circuits can thus also be held relative to each other by placing them in specific housings provided for this purpose in a closure housing not shown in Figures 2 (a) and 2 (b). Furthermore, according to another possible embodiment of the invention, the secondary is made directly on the housing. If the secondary has the structure of a loop, this loop is cast on the bottom or the cover of the housing, for example in a

gutter provided for this purpose.

  According to another possible embodiment of the invention, the secondary is embedded in the body of the housing. Indeed, it is made of plastic material which is molded around a copper loop or any other conductive metal constituting the secondary

of the antenna.

  It is obvious that in all these possible embodiments of the antenna according to the invention, as well as in the embodiment which will be described below with reference to FIG. 3, the relative positions of the primary and the secondary are determined by the tuning or electromagnetic matching constraints, to achieve an electromagnetic energy transfer between the two which is determined to produce the characteristics

  global search of the antenna in two parts.

  By analogy with a reflector antenna where the primary source is located at the secondary focus constituted by the reflector, it will sometimes be said in the following that the secondary of the two-part antenna is

  focused on the primary or vice versa.

  In all cases, it is found that the secondary, which is not physically connected to the receiver circuit, in other words not connected to the receiver circuit by an electrical connection, constitutes a transition element between the propagation medium. and the primary which is physically connected to the receiver circuit, ie connected by an electrical connection to the two terminals

  receiver provided for this purpose.

  Indeed, the electromagnetic energy present in the propagation medium is captured, in other words it is collected, and concentrated by the secondary, the primary sensing the electromagnetic energy present

in the secondary.

  It is obvious that the phenomenon described above is reciprocal, the operation of the antenna in a transmission configuration, ie in a transmitter, being symmetrical. In other words, the emitter circuit emits electromagnetic energy in the primary, this electromagnetic energy being captured then

  radiated by the secondary in the propagation medium.

  In Figure 3, there is shown a preferred embodiment of the antenna in two parts according to the invention. In this embodiment, the receiver circuit not shown is disposed in a closure and sealing housing 30. Only the primary 31 of the antenna is shown in dotted line, in that it is inside the housing for example disposed on the printed circuit 23 of Figure 2 (b) which also carries

the receiver circuit 20.

  An adhesive label 33, which is glued to the outer surface of the housing 30, carries the secondary 32 of the antenna in two portions 31,32. The secondary 32 is made in the form of a conductive track, loop or not, which is arranged, according to any screen printing method known to those skilled in the art, on the adhesive label 33. Said adhesive label is then glued on the housing in a determined position with respect to a predetermined position of the primary 31 which is at

the inside of the case.

  According to a preferred embodiment, the adhesive label is in fact glued on an inner face of the casing, so as to be protected from the attacks of the external environment, which, in an application for

  the automobile is considered particularly severe.

  In Figure 4, there is shown a possible embodiment of the secondary 40 of the antenna. Indeed, in the previous figures, it has been shown as a closed conductive loop, constituting a radiating element for the transmission or reception of electromagnetic energy, received or transmitted to the antenna primary by magnetic coupling. A certain advantage of the two-part structure of the antenna according to the invention lies in the fact that the secondary contributes to achieving the adaptation between the propagation medium, which is here the air

  ambient, and the receiver circuit.

  This adaptation induces a receiver structure that requires a compromise with the constraints imposed by the desired performance of the antenna,

  in terms of radiation pattern and gain.

  The principle of impedance matching of the antenna according to the invention is inspired by the theoretical principle of adaptation using two inductances, a primary inductance and a secondary inductance to achieve the electromagnetic adaptation and therefore the maximum of

energy transfer.

  It is for this reason that the secondary is also called "motive of agreement", in that it realizes

  the agreement between the propagation medium and the receiver.

  The calculations required by the design of the complete system call for the general theory of transmission lines. In particular, the tuning is realized a frequency or a frequency range determined around a resonant frequency of

the antenna in two parts.

  The value of this resonant frequency is determined mainly according to the components

  capacitive and inductive radiating elements.

  In FIG. 4, the secondary 40 is thus constituted by a non-closed loop comprising an inductive part 41 corresponding to the loop itself, and by a capacitive part 42 corresponding to a zone where the two ends of the non-closed loop extend

parallel to each other.

  It is known to those skilled in the art to calculate, at the working frequency under consideration, the theoretical value of the capacity of the loop 40 as a function of the length of the zone 42 where the two ends of the loop constitute the equivalent of two electrodes of a capacitor, and as a function of the width of the dielectric space separating them, as well as of calculating, always at the working frequency considered, the value of the equivalent inductance of the loop 40 in function

  the length of the portion 41 of said loop 40.

Claims (11)

  1. An antenna, such as an antenna used in the transmitter or the receiver of a radio frequency remote control, this transmitter, respectively this receiver, being made on a printed circuit (23) placed in a closure housing (30), that -ci being made of a moldable material such as a plastic material, characterized in that it comprises two parts in cascade: - a first part (21,31), called primary, constituted by at least one conductive track made for example in microstrip technology, which is physically connected to the transmitter, respectively to the receiver (20,30), via two terminals (12,14); and - a second part (22,32), called secondary, which is not physically connected to the transmitter, respectively to the receiver (20, 30), and which is arranged relative to said first part (21,31) of to perform an impedance transformation to achieve an adaptation between the transmitter and the propagation medium, respectively between the propagation medium and the receiver, and / or to produce a better electromagnetic radiation pattern and a better gain for the antenna.   2. Antenna according to claim 1 characterized in that the primer is made microstrip technology or coplanar on a first face of said printed circuit board (23).   3. Antenna according to claim 1 characterized in that the secondary (22) is made in microstrip or coplanar technology on a second side of said printed circuit (23) so as to be focused on the primary (21); 4. Antenna according to claim 1 characterized in that the secondary (22) is formed in the form of at least one conductive track etched on the housing of   closing so as to be focused on the primary.   5. Antenna according to claim 1 characterized in that the secondary (22) of the antenna is formed in the form of at least one conductive track which is embedded in the closure housing (30) so as to be focused on the primary.   6. Antenna according to claim 1 characterized in that the secondary (32) is in the form of at least one conductive track disposed on an adhesive label (33) which is glued to the closure housing (30) so as to be focused on the primary (31).   7. Antenna according to claim 1 characterized in that the secondary (22) is formed on a second printed circuit arranged inside the closure housing parallel to the first printed circuit (23) on which is disposed the primary (21) and the electronics of the transmitter, respectively the receiver (20), said second printed circuit being arranged relative to the printed circuit (23) carrying the primary so that the secondary is focused on the primary. 8. Remote control transmitter, of the type of a radio frequency remote control used for locking and unlocking the opening of a motor vehicle, characterized in that it comprises an antenna   according to any one of claims 1 to 7.   9. Remote control receiver, of the type of a radiofrequency remote control used for locking and unlocking the opening of a motor vehicle, characterized in that it comprises an antenna   according to any one of claims 1 to 7.   10. Remote control system, of the type of a radiofrequency remote control used for locking and unlocking the opening of a motor vehicle, comprising a transmitter and a receiver, characterized in that the transmitter is a transmitter according to the claim 8.   11. Remote control system, of the type of a radiofrequency remote control used for locking and unlocking the opening of a motor vehicle, comprising a transmitter and a receiver, characterized in that the receiver is a receiver according to claim 9.