WO2007119031A1 - Device for distribution signals - Google Patents

Abstract

In the invention, in order to improve the distributing of electrical signals in a small structure, of the order of 100 metres of deployment, there is provision to convey the electrical signals to be distributed with a coaxial cable (2). From place to place, at the location of the distribution sites, there is provision to make small openings (7) in the cable. These small openings lead to local removal of the screening (5), the braid of the coaxial cable, but to the retaining of the insulant (4) of the core (3) of the coaxial cable. A small antenna element (8) is then placed opposite the opening. With the signal thus picked up, and additionally amplified, it is possible to distribute, both when sending and receiving, multiple channels on one and the same coaxial cable.

Description

 DEVICE FOR DISTRIBUTING SIGNALS

The present invention relates to a hybrid signal distribution device, preferably used at short range but high speed. The invention relates more particularly to aircraft in which it is necessary to distribute control and / or measurement signals all along the aircraft, as well as to the ends of the wings. The invention would also be applicable to residential or office buildings, typically for the development of local networks for distributing computer data or television data signals. A main advantage of the invention is to furthermore combine an electrical signal distribution circuit with a power supply circuit, or even a power supply power circuit, hence the hybrid name.

In the field of transmission of electrical signals and power supply, various means of transport are known. On the one hand the existence of differentiated means for power supply and signal transmission is known. However, it leads to the use of differentiated electrical connections. There is therefore in this case the existence of a power supply network spreading in concert, side by side, of a distribution network of electrical signals. The latter, in most cases, may consist of twisted pair links. Possibly the transmission of electrical signals is performed by coaxial cable. The disadvantage presented by double networks of this type is the weight of the equipment installed (particularly unacceptable inside the aircraft), as well as the cost of installation and material.

We know the carrier current systems that can convey on the one hand the power supply and on the other hand the digitized data signals on the same connection. The disadvantage presented by these known power line transmission systems lies in the flow rate. Indeed, at most with networks of this type, on links of the order of a hundred meters, and in compliance with the constraints of electromagnetic compatibility aircraft (EMC), we can not exceed speeds of 20 mega bits per second. In the field of avionics, as well as in the field of broadcasting television signals, much higher data rates, typically of the order of or greater than one gigabyte, are envisaged. For such data rates, and in this context, any system based on links other than shielded twisted pairs, in point-to-point connection, can not be suitable. In practice, if you want to reach these high speeds with specific cables, for a dozen distribution points, you need ten links: ten times the weight, ten times the material price, ten times the installation price.

In contrast, the coaxial links allow to distribute information at very high speed. But the realization of sampling points requires adaptation devices, and ultimately a loss of 3 dB each time a bifurcation is encountered. For ten distributions located on the same cable, one thus achieves a loss at the end of 30 dB and thus of 300 dB if there are 100 distribution points. Such a solution is not conceivable. Especially since, moreover, it remains to solve the problem of the power supply.

Furthermore, European patent application EP-A-0 153 239 discloses an embodiment comprising a leaky coaxial cable that can be installed in the roof of a tunnel, in order to allow broadcasting to vehicles traveling in the tunnel. The proposed system, low frequency because intended for waves from 150 KHz to 1700 KHz, provides the existence of two coaxial cables leak and radiated, fed in parallel, and arranged on both sides of the tunnel vault. Such a solution is not suitable for aircraft structures, especially metal structures in which multiple reflections can produce diffusion deficits incompatible with the expected security of the transmission of the digitized data. In addition, the broadcast mode prevents the design of point-to-point links with particular data exchanges at the two connected points.

The patent application US-A-2003/0052771 also proposes to combine an electrical power supply with a signal transmission using the same coaxial cable. Such a solution described for supplying only two ends would also suffer from the drawbacks mentioned above of the loss of power for the last distribution point if there were several.

The object of the invention is to remedy these drawbacks by proposing a distribution by coaxial cable in which, instead of providing samples by electrical connections, sampling is provided. by radio waves. The radiations are not diffused along the cable, they are organized only at the point of distribution points, in particular by making small openings in a braid or shielding of the cable, so as not to disturb the characteristics of the cable. impedance of the cable. As a result, from one end to the other, the coaxial cable, which can be loaded by a characteristic impedance at the end, allows only very small quantities of radioelectric energy to pass locally to the distribution points. These very small local losses do not modify the impedance or the propagation of the signal in the cable. According to the invention, at the location of each local opening, an antenna is then produced which picks up the radioelectric radiation. The signal thus taken is conducted on a connection which leads to the distribution point. In practice, it is possible to make as many sampling points as desired, all along the cable, in any part of an aircraft served by a single cable. By doing so, the problem of distributing electrical signals everywhere is effectively solved. Moreover, by way of improvement, the coaxial cable, in particular its shielding or its outer braid, is used as a connection for transmitting a phase or a polarity (continuous or alternating) of a power supply. The other phase or polarity is conveyed either by a mass of a carcass of the structure of the aircraft (or the building) or by another coaxial cable. But in both cases, the number of cables installed in the building is reduced.

The subject of the invention is therefore a signal distribution device comprising a first coaxial cable formed by a conductive core, extended in a dielectric cylindrical wall, itself surrounded by a shield, characterized in that it comprises an opening made in a the shielding on a current part of the cable, the opening leaving present dielectric material interposed, an antenna disposed in the opening and an electrical connection connected to the antenna. The invention will be better understood on reading the description which follows and the examination of the figures which accompany it. These are presented only as an indication and in no way limitative of the invention. The figures show:

- Figures 1a and 1b: an electrical signal distribution device according to the invention; - Figure 2: a schematic sectional view of details of implementation and use of the dispensing device of the invention;

- Figure 3: an alternative embodiment of a local distribution point according to the invention; - Figure 4: the schematic representation of a use of the device of the invention in an aircraft.

FIG. 1a and FIG. 1b show a signal distribution device 1 according to the invention. This device 1 comprises a first coaxial cable 2. The cable 2 comprises a conductive core 3 extended within a cylindrical dielectric wall 4 itself surrounded by a shield 5, typically a metal braid, in particular copper. However, it would be conceivable to carry out the shield 5 in the form of a continuous wide band wound helically around the wall 4. In practice, the conductive core 3 is generally made of copper, the dielectric cylindrical wall 4 being in silicone, and copper shielding as well. Aluminum can also be used. The cable 2 has a certain flexibility and, in a known manner, the braid 5 is contained in an insulating sheath 6, typically made of plastic.

The signal distribution device is characterized by an opening 7 made in the shield 5, after having been made in the sheath 6. Preferably, the opening 7 is flush with the wall 4. However, it is possible that at the time of opening, for practical reasons and cutting the braid 5, a surface portion of the wall 4 is torn off. In all cases, the opening 7 leaves present dielectric material of the wall 4 so that the core 3 is not electrically connectable through the opening 7. The distribution device also comprises an antenna 8 made here under in the form of a cane connected to a connection 9. At the location of the opening 7, the signals resulting from the current flowing in the core 3 radiate a radio field captured in the near field by the antenna 8 Given the small size of the aperture 7 the impedance of the coaxial cable 2 and therefore its mode of propagation are not affected.

The shape of the opening 7 can be any. In practice, it may have an elongated shape, Figure 1a, oriented in the direction of elongation of the core 3, or, Figure 1b, oriented perpendicularly to 3. In a variant, rather than being limited by a narrow spindle, the opening 7 may be arranged around the entire periphery of the cable 2, as will be seen later. Limits, 10 and 11, give an idea of the maximum longitudinal extension that can have the opening 7. Typically, this extension is of the order at most, plus or minus 20%, of the diameter of the coaxial cable 2.

The particularity of the antenna 8 is to have an elongation direction, with the cane, in an example substantially parallel to the extension of the core 3 in the cable 2. In practical terms, the electrical connection 9 is in the form of a second coaxial cable 12 having, as the first cable 2, a core 13 forming the connection 9, a cylindrical dielectric wall 14, a shield 15 and a sheath 16. Preferably in this case, the shielding 15 is electrically connected by a galvanic connection 17 to the shielding 5 of the cable 2.

In FIG. 2, it is shown that, preferably, the galvanic connection 17 forms a continuous shield all around the connection 9 and the antenna 7. In practice in this case, the opening 7, especially if it is made longitudinally between the limits 10 and 1 1, results from the peripheral removal of the sheath 6 at its place and from the localized removal, only inside the opening 7, the shielding 5. In practice, the device 1 of distribution comprises structurally two half-shells 18 and 19 embedding the cable 2 at the location of the opening 7. The two half-shells 18 and 19 further comprise means for being pressed against each other around the cable 2. Preferably, a half-shell 19, located on the side of the opening 7, has on the one hand means for guiding a tapping tool for precisely tapping the opening 7, in the sheath 6 d '. one hand, and in the shield 5 on the other hand. Once this tapping is done, the shell 19 has reliefs to maintain a mechanical connector 20 containing on the one hand a shield 17 surrounding a cylindrical dielectric wall 21 which holds the connection 9 and the antenna 7. The connector mechanical 20 is adapted to receive a mechanically complementary connector which itself is attached to a coaxial cable 12. The coaxial connector 20 may be of different types, for example, it may be BNC type. By doing so, it is ensured that the sampling of electrical signals in the aperture 7 by the antenna 8 results only from a production or diffusion of a small amount of energy of radio signals.

A local use member of these signals may be a measurement circuit or a control circuit.

In order to ensure the proper functioning of this measurement circuit or this control circuit, it is expected that the shield 5, and therefore the shield 17 and the shield 15 of the cable 12, serve to distribute a phase or a polarity, here positive , a power supply 22, here continues. Preferably in this case, the current return will occur by a mass 23 of the structure in which the cable 2 winds. The power supply could, however, rather than a continuous power supply, be a low frequency AC power supply, typically between 50 Hz and 60 Hz, 220 V or 380 V. Such a structure will be in this case, especially an aircraft since its metal casing lends itself well to ensure the return of current 23. Alternatively, rather than having a only coaxial cable 2 which runs all along the structure, one can predict two. In this case, the second cable can be used to convey the second phase or the second polarity of the power supply. One could possibly provide three in the context of a three-phase power supply. In these cases, coaxial power cables travel together in the structure. In all cases, preferably, the power supply is conveyed by the shielding of cables whose surface is larger and leads to be able to carry more power than the core 3. Indeed the power transportable by the latter is limited by the length of its periphery.

FIG. 3 shows an alternative embodiment of the antenna 8. In the coaxial cable 2 between the limits 10 and 11, it is anticipated that the coaxial cable 12 is connected or using a wheelbase 24, with an allowance, only at the location of 7. For example, while the sheath 6 may have been removed all around the periphery of the cable 2, the shield 5, the braid 5, has not been removed, or more exactly has been straightened only at 7. On the other diametrical side of the cable 2, the braid 7 at the location 25 continues to remain pressed against the dielectric wall 4. In the over-wheelbase 24 the antenna 8a a wired form of a very flattened oval, with a strand 26 pressed against the wall 4 and two return connection strands 27 and 28, remote from this wall 4. It forms an electric loop. The strand 27 is preferably connected to a raised end of the shield 5, while the strand 28 does not come into contact with the shield 5 but is instead connected to the connection 9 forming the core 13 of the cable 12. Typically, the The shield 17 is also connected, at the location 29 of the connection of the strand 27, to the shield 5. Such an embodiment can of course be made in a traditional manner. Preferably, a base 30, shown by the hatching, is made of silicone. It comprises the antenna 8, partially flush with its strand 26, its connection 9 and the core 13, the wall 12 and the shield 17. The base 30 is able to receive, once it is introduced into the opening 7 and plated on the dielectric 4, a folding of the shield 5 also connected to the shield 17.

FIG. 4 shows, in a schematic manner, the introduction of such a coaxial cable in an aircraft 31. At the location of each local distribution point 32 to 34, a device connected to it 35 to 37 comprises an amplifier A. The amplifier A can be placed at the beginning of the connection 9. It takes its electrical amplification power on the power supply conveyed by the coaxial cable 2 and the mass 23 in the aircraft. The ends of the link 13 17 are in all cases adapted to avoid any reflections and standing waves. The device connected, in transmission or reception, further comprises means for coding the signals to be distributed at high speed. In practice, these signals will be coded by preferably using GSM type coding typically with the same frequency bands between 900 MHz, 1800 MHz or 2100 MHz, both in transmission and in reception. In practice, such a protocol makes it possible, by the differences of the rising and falling frequencies, to multiplex the transmissions. For simplicity, it can be assumed that each connected device can transmit around a frequency fi, for example here, f1, f2, f3 for the connected devices 35 to 37. Alternatively, rather than having a frequency multiplexing, the devices connected 35 to 37 will implement a time multiplexing, typically of the type provided in the context of the GSM protocol (Global System for Mobile - telecommunications system for mobile phones).

Claims

1 - Device (1) for distributing signals comprising a first coaxial cable (2) formed by a conductive core (3) extended in a dielectric cylindrical wall (4), itself surrounded by a shield (5), characterized in it comprises an opening (7) made in the shield on a running part of the cable, the opening leaving present dielectric material interposed, an antenna (8) having a cane with a direction substantially parallel to the extension the conductive core of said cable and disposed in the opening and an electrical connection (9) connected to the antenna. 2 - Device according to claim 1, characterized in that the opening is flush over the dielectric wall of the coaxial cable. 3 - Device according to one of claims 1 to 2, characterized in that the electrical connection (17) comprises another cable (12) coaxial, the shield (15) is connected to the shield of the first coaxial cable and forms a shielding continuous at the junction of this first cable with this other cable. 4 - Device according to one of claims 1 to 3, characterized in that the electrical connection comprises a coaxial connector (20). 5 - Device according to one of claims 1 to 4, characterized in that the shielding of the coaxial cable is traversed by an electric supply current (22), a return of this power supply current being carried by a mass (23) a structure in which this dispensing device is mounted. 6 - Device according to one of claims 1 to 5, characterized in that it comprises a second coaxial cable running together with the first coaxial cable in a structure, a shield of a first coaxial cable carrying a first phase polarity a power supply signal, a shield of a second coaxial cable carrying a second polarity or phase of this power supply signal. 7 - Device according to one of claims 5 to 6, characterized in that it comprises an amplifier (A) in the connection connected to the antenna. 8 - Device according to one of claims 5 to 7, characterized in that it comprises means for coding the signals to be distributed according to a GSM protocol. 9 - Device according to one of claims 1 to 8, characterized in that the opening is formed in part on an entire periphery (10 - 1 1) of the cable. 10 - Device according to one of claims 1 to 9, characterized in that it comprises a plurality of openings (32 - 34) formed on the first coaxial cable and means of time multiplexing and or frequency of signals carried by the coaxial cable, in transmission and / or reception. 1 1 - Device according to one of claims 1 to 10, characterized in that the antenna comprises an electric loop (26 - 28) connecting the shielding of the cable to the connection. 12 - Device according to one of claims 1 to 1 1, characterized in that the antenna comprises a base (30) against the cylindrical wall.