FR2776145A1 - Signal transmission system for satellite broadcast signals relayed within building - Google Patents

Abstract

The system uses repeaters and additional aerials to enable signals to reach within buildings. There are transmission aerials and user receiving aerials between them. The user receiving aerials transmit in opposite directions but with the same frequency and are supplied with the same signal. There is also a repeater connected to one of the aerials.- DETAILED DESCRIPTION - The system includes at least a first (5') and a second (14) transmission aerial, with user receiving aerials (8') being situated within a region between the transmission aerials. The user receiving aerials are directive and are each orientated towards one of the available transmission aerials (5'14). These two aerials transmit in opposite directions but with the same frequency and are supplied with the same signal. These aerials are shifted w.r.t. each other in a direction which is perpendicular to their direction of transmission. The transmission system may include a repeater (13) connected to one of the aerials, the repeater comprising a low noise amplifier, pass-band filter, and power amplifier

Description

-I

  SYSTEM AND METHOD FOR TRANSMITTING SIGNALS

  The present invention relates to a system and method for transmitting point-to-multipoint signals. It relates more particularly to the transmission of video services for users located in an environment close to the source of transmission of services, it being understood that the term "user" is taken here in the broad sense of user services. Such transmission systems can be used for operating digital and / or analog services from satellite links for home applications. These are point-to-multipoint links, the signal being received by a receiving antenna,

  usually located on the roof of a building, before distribution.

  An example of an aerial transmission system in a building of a signal received in a given frequency band, including a frequency transposition circuit which performs a frequency conversion of the signal received from the satellite antenna, the antenna emission and the user antennas being placed outside

of the building.

  The transmission is carried out after a transposition in frequency of the whole of the satellite band received in a different frequency band. The users have reception antennas, in

general of small dimensions.

  This system has the main advantage of providing a solution to

  low cost for transmitting satellite signals to apartments.

  The transmission device, simple because without wire connection, is also discreet and inexpensive. It is very compact for the user, the antennas can be very small,

the order of a few centimeters.

  For optimum transmission and coverage of the building, the emission antenna illuminating the user antennas should have a narrow section of radiation in the plane perpendicular to the main facade of the building to minimize reflections on the walls of the building. the facade, and wide cut in

  the plane parallel to this facade to illuminate the latter as much as possible.

  However, for products subject in particular to low space requirements and low cost manufacturing, the beam width of the transmitting antenna in the plane parallel to the

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  facade is limited. Therefore, from a certain building width, a single transmitting antenna can no longer cover the entire building. Figure 1 shows a possible solution to illuminate a building facade can not be illuminated by a single transmitting antenna. The assembly 1 represents a building consisting of apartments 2. A satellite antenna 3 adapted to receive the satellite signals is installed on the roof of the building 1 and is coupled to a first frequency transposition circuit 4 whose output is connected to a transmitting antenna 5 and a second frequency transposition circuit 6 whose output is connected to a transmitting antenna 7. These two transmitting antennas 5, 7 are arranged vertically to a part of the facade their own, so that they can be covered by

  superimposition of their respective radiation patterns the near

  the entire facade of the building 1. The signals emitted by the antennas, 7 are picked up at each apartment 2 by a receiving antenna directive called in the following antenna user 8 installed by

  example on the facade of the building 1 at the level of the apartment 2.

  For optimum reception of the signals, each user antenna 8 has its radiation pattern oriented according to its location on the facade of the building 1 either towards the antenna 6 or towards the antenna 7 so as to

  get the maximum gain in reception.

  However, as shown in FIG. 1, in this configuration, interference between the adjacent beams 9, 10 of the two transmitting antennas 5, 7 occur. The direct beam from a transmitting antenna to a subscriber antenna 8 is represented in solid line while the interfering beam coming from a secondary lobe of

  the other transmitting antenna is shown in broken lines.

  The same problem arises during the transmission from signal transmission antennas to user antennas in the context of a fixed cellular network, in particular of the type of a multichannel multi-point distribution system called MMDS (multi-channel). point Multi-channel Distribution System in English), a local multipoint distribution system called LMDS (Local Multi-point Distribution System in 3 5 English language) or a multipoint video distribution system said

  MVDS (Multi-point Video Distribution System in English).

  Existing solutions to this type of problem lie in the use of orthogonal polarizations (so-called diversity technique).

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  polarization) or different frequencies for the respective emissions

transmitting antennas 5, 7.

  However, generally, the entire available frequency spectrum is used for transmission by each of the antennas 5, 7. Moreover, since the satellite can transmit with a bandwidth of 2 GHz in both polarizations, the reception channel is often doubled to receive the satellite signals in the two polarizations, which may require transmission antennas 5, 7 and users 8 double polarization. Therefore, the above-mentioned solutions, because they imply a reduction in the transmission capacity of the transmitting antennas 5, 7 and subscribers 8, can prevent compatibility with the transmission capability.

satellite transmission.

  The invention overcomes the aforementioned drawbacks.

  The subject of the invention is a signal transmission system comprising at least a first and a second transmitting antenna, user receiving antennas being placed in a zone situated between said transmitting antennas, characterized in that the user antennas are directed and are each directed towards one of said at least two transmitting antennas, in that the first and the second transmitting antennas emit in opposite directions on said area at the same frequency while being powered with a same signal, the first and the second transmitting antennas being offset perpendicularly by

  report to their issuing management.

  Thus, by virtue of the 180 inversion of the illumination direction of the second transmitting antenna with respect to the illumination direction of the first transmitting antenna and knowing that the user antennas are each directed towards the first transmit antennas, each user antenna is angularly isolated from the influence of the main lobe of the beam of the transmitting antenna towards which said user antenna is not oriented. The solution provided by the invention makes it possible to widen the coverage of the transmission system without undergoing a reduction in the capacity of the system by spectral division or polarization diversity, the second transmitting antenna reusing the frequency band of the first antenna. In addition, the system as arranged avoids interference in

transmission of the prior art.

  According to one embodiment of the invention, the system comprises an antenna for receiving the signals transmitted by the first transmitting antenna, the signals thus received being transmitted by

  transmission means to at least the second transmitting antenna.

  Advantageously, for optimal restitution of the signals,

  said transmission means comprise a repeater.

  According to one embodiment, said repeater comprises at least one low-noise amplifier, a band-pass filter and a power amplifier. According to one embodiment, the first transmitting antenna is disposed on one side of the area to be covered by the transmitting antennas while the second transmitting antenna is disposed on the opposite side.

of it.

  According to one embodiment, said area covered by the

  Transmitting antennas is at least one building facade.

  Preferably, in the case of a building facade, the first transmitting antenna is disposed on the roof of the building while

  that the second collective antenna is arranged at the foot of it.

  According to another embodiment, said transmission zone

is a fixed cellular network.

  Another subject of the invention is the use of a transmitting antenna, characterized in that it is implemented in a

  signal transmission system as defined above.

  Another object of the invention is a method of transmitting signals to user antennas located on a given zone, characterized in that it comprises the following steps: a step of transmitting signals between a first transmitting antenna and antennas used in a given transmission frequency band, - a step of receiving said signals by an antenna for receiving and transmitting them to a second transmitting antenna, - a step of transmitting said signals in said transmitting band from the second transmitting antenna, said first and second transmitting antennas emitting substantially in opposite directions on said area at the same

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  frequency by being fed with the same signal, the first and the second transmitting antennas being offset perpendicularly by

  report to their issuing management.

  Advantageously, in order to increase the directivity of the first transmitting antenna, the above method comprises, as a preliminary step, a step of converting the signals in a band of

higher frequency.

  Other features and advantages of the present invention

  will emerge from the description of the embodiments that follow,

  taken as non-limiting examples, with reference to the appended figures in which: FIG. 1 represents a system for transmitting signals in a building; FIG. 2 represents a system for transmitting signals in a building according to a method of embodiment of the invention; FIG. 3 represents a frequency transposition circuit operated by the transmission system according to the invention; FIG. 4 represents a repeater according to the invention; FIGS. 5a and 5b represent respectively a first and a second transmitting antennas according to embodiments of the invention, - Figure 6 represents a user antenna according to one embodiment of the invention, - Figure 7 represents another embodiment of the invention.

  system according to the invention in a fixed cellular network.

  Figure 2 shows a signal transmission system

  in a building 1 'according to one embodiment of the invention.

  Building 1 'consists of 2' apartments. A satellite antenna 3 'able to receive the satellite signals is installed on the roof of the building 1' and is coupled to a frequency transposition circuit 4 '

  whose output is connected to a transmitting antenna 5 '.

  Figure 3 gives a schematic description of the circuit of

  frequency transposition 4 'operated by the transmission system

according to the invention.

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  The signals received from the satellite by the satellite antenna 3 'are converted via a low noise converter block 22 (generally integral and part of the antenna) or LNB ("Low Noise Block" in English). These signals are then transmitted to the input of the frequency transposition circuit 4 'which is the first input of a mixer 23, the second input of this mixer being supplied by a local oscillator 24. The output of the mixer 23 is connected. , via a band-pass filter 25, to a first input of a second mixer 26 whose second input comes from a second local oscillator 27. The output of the mixer 26 is connected to a power amplifier 28 which transmits the amplified signal to the transmitting antenna 5 '. The output of the power amplifier 28 is

  the output of the frequency transposition circuit 4 '.

  According to one embodiment, the signal received by the antenna 3 ', for example in the frequency band [10.7 Ghz-12.7 Ghz l, is converted a first time in the intermediate frequency band [950

  Mhz-2150 Mhz] via the low noise converter block 22.

  Thanks to the mixer 23, the local oscillator 24 providing it, on its second input, a signal at the frequency of 11 Ghz, the signal is converted a second time around the frequency of 12 Ghz. The signal at the intermediate frequency thus obtained is then filtered thanks to the filter 25 which eliminates the image frequency, then transmitted to a second mixer 26. This mixer 26 receives on the second input, the signal of the local oscillator 27 at the frequency of 27.5 Ghz to convert the incident 2D signal in the frequency band [40.5 GHz - 42.5 Ghz]. It is this signal that is amplified by the amplifier 28 to power the antenna 5 'with sufficient power to be picked up by all the

subscribers of the building.

  The power transmitted at the air level may be limited to a predefined value to allow a choice of frequencies if the standards and regulations for use of frequencies of the radio spectrum allow the free use of frequencies for powers lower than specified values, when such standards

and permissions exist.

  The signals emitted by the antenna 5 'are picked up at each apartment 2' by a user antenna 8 'which is a directional receiving antenna installed for example on the facade of the building 1'

at the level of the apartment 2 '.

  A receiving antenna 12 is placed at the foot of the building 1 ', facing the antenna 5' and in the field of the radiation pattern thereof, preferably in the direction of the maximum power of the diagram. of radiation of the antenna 5 '. The signals that the latter receives are transmitted to a repeater 13 whose output signals are delivered to a transmitting antenna 14. This antenna 14 transmits towards the building 1 ', in the direction opposite to that of the antenna 5 'to be able to illuminate at least the complementary part of the building 1' compared to that already illuminated by the antenna 5 '. Each user antenna 8 is arranged in such a way that its radiation pattern is oriented either towards the antenna 5 or towards the antenna 14. In this way, the user antennas 8 fully capture the beams 9 and

  the beams 10 do not interfere with these.

  FIG. 4 represents the repeater 13 according to one embodiment of the invention. The antenna 12 is connected to the input of the repeater 13 by the input of a low noise amplifier 15 ("Low Noise Amplifier" in English) whose output signals are filtered by a bandpass filter 16 centered on the transmission frequency of the carrier. The signals thus filtered at the output of the filter 16 are amplified by a power amplifier 17 to be filtered again on the transmission frequency by a bandpass filter 18 whose output corresponds to the output of the repeater 13 and is connected to the transmission antenna 14. According to a not shown variant of the repeater 13, the latter comprises, in addition to the structure previously described and illustrated in FIG. 3, a signal demodulation circuit followed by a carrier regeneration circuit of which the output signals are modulated by a

modulation circuit known per se.

  FIGS. 5a and 5b respectively represent transmitting antennas 5 ', 14 according to two embodiments of the invention, whereas FIG. 6 represents a user antenna 8' according to one embodiment of the invention. invention. The technology chosen for the transmitting antennas 5 ', 14 and the user antennas 8' is that of the microstrip printed array antennas in the English language thanks to their small dimensions, their small weight, their ease integration into other reception / transmission circuits and their high flexibility to synthesize radiation models of different shapes. A microwave substrate,

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  dielectric permitivity of 2.6 and height of 0.8 cm for example,

  could be suitable for producing such antennas 5 ', 8', 14.

  FIG. 5.a illustrates the transmission antenna 5 'comprising a linear array of N square pellets interconnected (N being equal to 20 in the present case), this network providing a beam of radiation broad in the plane parallel to the facade of building 1 to illuminate the latter as much as possible. The width of the beam in the plane parallel to the facade is determined by the width of the beam in the plane H of a single pellet 19, namely the plane defined by the direction of the radiation (that is to say the perpendicular to the surface of the network) and the direction of the field H. In this definition of the plane H, it is understood that the radiated fields have linear polarizations, which can not be a limitation within the scope of the present invention. The width of the beam in the plane perpendicular to said facade is in turn determined by the number N of pellets 19. For the substrate parameters defined above, the beam width in the plane parallel to the facade is such that the an angle of 3dB is obtained in the latter plane of 83, while in the plane perpendicular to said facade, a 3 dB angle of 3.7 is obtained. The gain of

  the transmission antenna 5 is approximately 20 dB.

  In FIG. 5.b is illustrated the transmission antenna 14 comprising an array of 2xN square pellets. The width of the beam in the plane parallel to the facade is determined by the width of the beam in the plane H of a pair of pellets 19 while the width of the beam in the plane perpendicular to said facade is determined, as previously, by the number N of pellets 19. For the substrate parameters defined above, the beam width in the plane parallel to the facade is such that an angle is obtained at 3dB in the latter plane of, while similarly, in the plane perpendicular to said facade, a 3 dB angle of 3.7. The gain of the transmitting antenna is approximately 22 dB. The choice of the structure of the two transmitting antennas 5 ', 14 is made taking into account the width of the building 1'. Indeed, it is noted that the first transmitting antenna 'can cover a wide coverage area, the second transmitting antenna 14 to cover a more restricted area. Those skilled in the art know that the angle at 3dB in a plane defined by a section of the radiation surface according to the width I of the antenna is proportional to the ratio

  X / 1 and that the gain G of an antenna is proportional to the ratio 4f-S / X2 ,.

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  representing the wavelength of the waves received or transmitted and S the area of the antenna defined in this case by the product Lxl, L being the second dimension of the antenna. In this case, which does not require a large coverage for the second transmitting antenna, the width I of the transmitting antenna 14 is increased, which reduces the angle to 3 dB in the plane of the facade and therefore the coverage of the second transmitting antenna 14 but increases the gain of said antenna 14. Of course, in the case of a very large building or we need a maximum coverage for the transmit antennas 5 ', 14, we will take a linear network of N pellets 19, which allows an optimization at the coverage level of the combination of the two

transmitting antennas 5 ', 14.

  FIG. 6 represents an embodiment of the antenna of

  receiving 8 'formed of a network antenna of 16x16 pellets 19' square.

  The gain of such an antenna is approximately 28 dB. For example, for a building with a height of 100m, we can take reception antennas 8 'of a size of 8cm by 8cm and a thickness of 0.1cm, a first transmitting antenna 5 with a length L of 10 cm over a width I of 1 cm, and a second transmitting antenna 14 of length L of 10 cm and width 1 'of 1.5 cm. It is obvious that the technology borrowed for the 5 ', 14' and the 8 'transmit antennas is not necessarily a printed technology but can use waveguide antennas or any other type of antenna capable of emitting respectively receive signals. FIG. 7 represents a fixed cellular network 20 covering dwellings 21. The first transmitting antenna 5 'covers a first given geographical area. Placed vis-à-vis the latter antenna 5 'and offset along the perpendicular to the direction of their radiation, two receiving antennas 12 pick up the signals sent by the antenna' and transmit respectively to the repeaters 13 which provide without degradation to the transmitting antennas 14 the signals received by the antennas 12. The receiving antennas 8 'disposed generally on the roof of the house 21 are oriented according to their location either towards the antenna 5' or towards one transmit antennas 14. This system makes it possible to enlarge the transmission coverage area with a frequency reuse technique. It should be noted that antennas 14 must

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  be placed and their radiation patterns must be configured so that the latter relating to the antennas 14 can not overlap. The signal transmission system according to the invention operates as follows: The satellite signals are received at the satellite antenna 3 'and converted into an intermediate frequency at the first low-noise frequency converter 22. The signals Thus, the converts 10 are advantageously transmitted to the frequency transposition circuit 4 'which transposes the signals into a higher frequency range, around 40 Ghz. The signals thus transposed at high frequencies are sent to the transmitting antenna 5 'which is responsible for transmitting said signals over its coverage area. The receiving antenna 12 disposed opposite the antenna 5 'receives the transmitted signals, transmits them to the repeater 13 which filters and amplifies on the band of

  transmission frequency and provides the signals to the transmitting antenna 14.

  The signals emitted by the antenna 14 make it possible to complete the coverage area of the antenna 5 '. Depending on their location, the receiving antennas 8 'which are chosen sufficiently directed are oriented either towards the antenna 5' or towards the antenna 14. If an antenna 8 'is oriented towards the antenna 5', then the main lobe of its beam of radiation points towards the antenna 5 ', which means that the beam emitted by the antenna 14 disturbs only secondary lobes of overflow which can be considered negligible. The same principle is applicable for the antennas 8 'directed towards the antenna 14. The antennas 8' thus do not undergo any interference between the respective beams of the antennas 5 ', 14. The user antennas 8' are chosen such that they are guidelines with a predominant main lobe and negligible side lobes. Thus, the beams of the antennas 14 are generated so that each of them has a sufficient gain in its coverage area to route the traffic and a sufficient rejection in the other areas to avoid unacceptable interference. The required discrimination between the wanted signal and the interfering signal is obtained by providing a given minimum spacing between the beams of the two antennas 14. This minimum spacing is even lower than the angle

  the opening of the beams of the antennas 14 is weak.

  Of course, the invention is not limited to the embodiments described in this patent application. Thus, the repeater 13, the transmitting antennas 5 ', 14 and the frequency transposition circuit 4' may be of a structure different from those mentioned above in that they fulfill the function which

assigned to them respectively.

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Claims (10)

  A signal transmission system comprising at least a first (5 ') and a second (14) transmitting antennas, user receiving antennas (8') being placed in an area between said transmitting antennas (5 ', 14), characterized in that the user antennas (8') are directional and are each directed towards one of said at least two transmitting antennas (5 ', 14), in that the first ( 5 ') and the second (14) transmit antennas transmit in opposite directions on said area at the same frequency while being fed with the same signal, the first (5') and the second (14) transmitting antennas being offset perpendicular to their direction of emission. 2. System according to claim 1, characterized in that it comprises an antenna for receiving (12) signals emitted by the first transmitting antenna (5 '), the signals thus received being transmitted by   transmission means to at least the second transmitting antenna (14).   3. System according to claim 2, characterized in that   said transmission means comprise a repeater (13).   4. System according to claim 3, characterized in that said repeater (1 3) comprises at least one low noise amplifier (15), a   bandpass filter (1 6) and a power amplifier (17).   5. System according to one of claims 1 to 4, characterized in   the first transmitting antenna (5 ') is arranged on one side of the r area to be covered by the transmitting antennas (5', 14) while the second transmitting antenna (14) is arranged on the opposite side of said antenna (5 ').   6. System according to one of claims 1 to 5, characterized in   this area covered by the transmitting antennas (5 ', 14) is at less a building facade (1 ').   7. System according to one of claims 1 to 5, characterized in   said transmission zone is a fixed cellular network.   8. Use of a transmitting antenna (5 ', 14), characterized in that said transmitting antenna (5', 14) is implemented in a   signal transmission system according to one of Claims 1 to 7.   9. A method of transmitting signals to user antennas (8 ') located on a given area, characterized in that it comprises the following steps 13 2776145   a step of transmitting signals between a first transmitting antenna (5 ') and user antennas (8') in a given transmission frequency band; - a step of receiving said signals by a receiving antenna (12 ) and transmitting them to a second transmitting antenna (14), - a step of transmitting said signals in said transmission band from the second transmitting antenna (14), said first and second transmitting antennas (5 ', 14) emitting substantially in opposite directions on said area at the same frequency being fed with the same signal, the first <5') and the second (14) transmitting antennas being shifted   perpendicular to their direction of emission.   10. The method of claim 9, characterized in that it comprises as a preliminary step a step of converting the satellite signals in a higher frequency band to increase the   directivity of the first transmitting antenna (5 ').