The invention concerns the field of radio-frequency devices featuring a transmission antenna and a receiving antenna.
It concerns in particular but not restrictively such devices for which the distance between the transmission antenna and the receiving antenna is short, compared to the wavelength λ of a carrier wave circulating between the transmission antenna and the receiving antenna, this distance being less than or of the same order of magnitude as λ/2Π.
It is known that a transmission antenna and a receiving antenna can be used operating in a close or distant field. Operating with a close field corresponds to the case indicated above, in which the distance between the antennas is less than or of the same order of magnitude as λ/2Π. It uses the model that is virtually stationary. On the contrary, the distant field for which the distance between the transmission antenna and the receiving antenna is significantly greater than λ/2Π uses propagation operation.
The amplitude of the electromagnetic induction decreases in the case of close field operation, according to a law of 1/dn and of 1/d in the case of distant field operation. d designates the distance between the transmission and receiving antennas and the exponent n is a number between 1 and 3 that depends on the directivity of the antennas and the distance between the antennas.
In the case of close field operation, used for the transmission of information as well as for the transmission of energy, it follows that the efficiency of the transmission decreases very rapidly with distance. One known solution is to increase the power emitted in order to have an energy or signal level that can be used at the receiving antenna.
The possibilities in this option of increasing the power emitted are however limited due to the applicable standards, in particular on platforms such as aircraft where there are a large number of items of electronic equipment that is sensitive to jamming due to white noise.
According to the invention, it is planned to increase the efficiency of the transmission without increasing too much the power emitted, to have one or more resonant circuits on the direct path or on the walls between the receiving antenna and the transmission antenna.
In this way, the invention concerns a radio-frequency transmission device comprising a receiving antenna and a transmission antenna characterised in that it comprises one or more passive resonant circuit(s) positioned between the receiving and transmission antennas.
Preferably, the passive resonant circuit is tuned to a frequency equal or close to a frequency circulating between the receiving and transmission antennas.
When we say that the passive resonant circuit is positioned between the receiving and transmission antennas, it is meant that it is situated in a volume defined by two planes parallel to one another, one passing through the transmission antenna, and the other through the receiving antenna and perpendicular to the direction joining the two receiving and transmission antennas. Preferably, and if there is nothing disturbing the passive resonant circuit, the latter will be positioned on the direct path between the receiving and transmission antennas. If there are walls positioned between the receiving and transmission antennas, in particular walls that are electrically conductive, forming an obstruction to the propagation of the electromagnetic waves, the passive resonant circuit will be positioned so that part of it is located on one side of the wall and part of it on the other side of the wall. If the wall is small in size defining a finite dimensioned volume positioned between the receiving and transmission antennas, the passive resonant circuit may be positioned so that one part of it is situated towards the transmission antenna and another part facing towards the receiving antenna. Of course, it is possible to position several passive resonant circuits between the receiving and transmission antennas, in particular at each electrically conductive wall located between the receiving and transmission antennas.
The invention, and examples of embodiments and application of the invention will now be described with reference to the appended drawings in which:
In the figures, identical reference numbers are attributed to elements that have the same function.
One particularly interesting embodiment of the invention will now be described with reference to
The coupling obtained by such a connection through a conductive wall 8 on which is mounted such a passive resonant circuit 5 is illustrated in a second part of the appendix to the first description.
Therefore, according to this embodiment, the passive resonant circuit is physically split into a first 15 and a second 16 part, connected to one another by electrical conductors 12 passing through a wall 8 with two faces, 9 and 11, a first face 9 and a second face 11, the first part 15 of the passive resonant circuit 5 being located on the same side as the first face 9 and the second part 16 of the passive resonant circuit 5 being located on the same side as the second face 11.
One interesting application of this embodiment will now be described with reference to
The wire connection 22 between the sensor and the rotating antenna is fragile and there is a resulting fragility of the transmission between the sensor 21 and the processing means 100. Furthermore, when dismantling for maintenance operations or to change a tyre, precautions must be taken in order to avoid making the connection fragile and to check that the connection is still made after reassembly. In short, such a connection is not very reliable and complicates maintenance work. The use of a passive resonant circuit 5 as described with reference to
The assembly using the invention is shown in part B of
Thus in general, the invention concerns the use of a radiofrequency transmission device to make a radiofrequency transmission through a wall between a transmission antenna and a receiving antenna which rotate with respect to one another, in which a passive resonant circuit 5 is physically divided into a first 15 and a second 16 part connected to one another by insulated electrical conductors 12 which traverse the electrically conductive wall 8, which has two faces 9 and 11, a first 9 and a second 11, the first 15 part of the passive resonant circuit 5 being located on the same side as the first face 9, and the second part 16 of the passive resonant circuit 5 being located on the same side as the second face 11.
A second advantageous use of the invention concerns the case where the connection between the transmission and receiving antennas is obstructed not by a large wall 8 positioned between the antennas or enclosing possibly with other walls the transmission antenna or the receiving antenna, as described in the cases above, but by one or more small conductive surfaces or by curved or angular surfaces. For example, this could be walls forming part of a dihedron. Another example of such a case is given for example by a transmission between a transmission antenna and a receiving antenna separated from one another by metal cans. These cans form an obstacle to the transmission. Of course, it can be envisaged to equip these cans with two resonant circuits, the first positioned to traverse the first wall and the second to traverse the second wall, for example diametrically opposed to the first. However, one embodiment of the passive resonant circuit located between the two antennas permits just a single circuit to be used for a curved surface. This embodiment will now be described with reference to
In summary, in this embodiment, the transmission and receiving antennas are separated by one or more conductive walls which have an inside and an outside face, at least partially defining a volume. One or more passive resonant circuits are physically divided into a first and a second part connected to one another by electrical conductors, the first and second parts and the electrical conductor connecting them, of each passive resonant circuit in two parts, are entirely located on the outside face of one or more of the said walls positioned between the transmission and the receiving antennas. The first and second parts are on opposed zones of the said outside faces of the said walls.
The result is symbolised by
Concept of Resonant Circuit Coupling
Take the basic circuit represented in
With the hypothesis that the coupling kij between an antenna i and an antenna j depends on the distance dij between the antennas i and j according to the relationship:
kij=a/dijn (1)
With the coupling mutual Mij between the inductance Li and Lj of the antennas i and j:
Mij=kij(LiLj)1/2 (2)
In the case of the intermediate resonant circuit 5, L2C2 {acute over (ω)}2=1, where {acute over (ω)}=2Πf, where f is the frequency of the signal emitted by the antenna 2 L2, the voltage surge factor Q=L2{acute over (ω)}/R2; the addition of this circuit is translated by a gain G in the induced electromotive force E3 at the receiving antenna L3.
G=1−jQ(k12k23/k13)
With the simplifying hypothesis d12=d23=d13/2=d/2 expressing that the circuit 5 is located halfway between the antennas, and the modulus of G>>1
G=k13 Q 4n
In this case, the direct coupling is nil: k13=0. The relay circuit is formed by two inductances coupled with a capacitor C2.
The resonance condition is expressed by the relationship:
C2 ω2(L′2 L2/(L′2+L2)=1,
With the simplifying hypothesis in which the inductances L2 and L2′ are identical: L2=L2′ and R2=R2′
The voltage surge factor:
Q=L2 {acute over (ω)}/R2=2/R2 C2 {acute over (ω)}
With the same hypotheses as we have already seen concerning the distances, the efficiency E (in this case, we do not speak of gain as the direct coupling is nil) corresponds to the ratio between the coupling through the wall via the resonant circuit and a reference system of direct coupling without a wall of factor k13.
E=2/Q (k13 K23/k12)
The efficiency is half of the gain for the system without walls with a resonant coupling circuit. With the hypothesis that the coupling between the antennas depends on the distance according to the relationship:
Kij=a/dijn
This application is a continuation and claims priority of U.S. patent application Ser. No. 10/495,068, entitled “PASSIVE DEVICE FOR INCREASING THE TRANSMISSION EFFICIENCY OF RADIO-FREQUENCY SYSTEMS” by Marcel Locatelli, filed on May 4, 2004 now U.S. Pat. No. 7,267,743.
Number | Name | Date | Kind |
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3657652 | Smith | Apr 1972 | A |
4642786 | Hansen | Feb 1987 | A |
5181043 | Cooper | Jan 1993 | A |
Number | Date | Country |
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197 00 110 | Jul 1998 | DE |
2 288 103 | Oct 1995 | GB |
WO 0026989 | May 2000 | WO |
Number | Date | Country | |
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20070182650 A1 | Aug 2007 | US |
Number | Date | Country | |
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Parent | 10495068 | May 2004 | US |
Child | 11726630 | US |