MULTI-CHANNEL ACQUISITION DEVICE FOR RADIO TRANSMITTERS
In general terms, the present invention relates to a fixed reception system for a radio channel, fixed network transmission system for information emitted at a single wavelength A by a plurality of emitters generally associated with measurement sensors, the emitters being spread over a geographic area, to the reception system for the collection of all the information emitted in said geographic area.
Companies having to manage distributed property - for example a stock of water meters, or a set of garbage dumpsters - have an increasing need to know at all times or at regular intervals the state of their stock - the index of a counter, or the position of a garbage dumpster - so as to ensure optimized and responsive management - leak warning on a meter, or theft of a dumpster.
Information is most often transmitted by radio channel from sensors, relayed by emitters to reception systems which are themselves directly connected to the computer network of the company (WAN or Wide Area Network).
In an urban environment, radio channel transmission is difficult because the waves meet many obstacles on their passage and are therefore partially reflected, re-emitted or absorbed many times before finally reaching the receiving antenna. The denser the urban environment, and the more difficult the conditions in which the transmitters (emitters or receivers) are located (basements, underground parking lots, etc.), the greater this difficulty in propagation is. It is extremely rare for the emitting antenna to be in direct view of the receiving antenna.

The reflections and re-emissions of signals result in the appearance of a distribution of standing waves in three dimensions. The signal level at every point in space is determined by the amplitude and phase sum of the direct signal and of the signals reflected or re-emitted by the obstacles encountered. Thus it occurs that at certain points in space the signal will be very weak (the various waves cancelling each other out) , which is called a "null spot" or a dead zone in the world of radio.
In addition, the position of these null spots evolves permanently due to changes in the environment - some objects are moved infrequently (furniture, walls, etc.), others move permanently (vehicles, people, etc.), particularly in a dense urban environment.
It is therefore very difficult to determine with precision the signal level received at a point and to protect against the null-spot effect.
The aim of the invention, above all, is to provide an effective, while relatively economical, solution to the problem of dead zones or null spots.
According to the invention, a fixed reception system for a radio channel, fixed network transmission system for information emitted at a single wavelength A by a plurality of emitters generally associated with measurement sensors, the emitters being spread over a geographic area, to the reception system for the collection of all the information emitted in said geographic area, is characterized in that it comprises at least two antenna-receiver pairs, each receiver of said pair being associated with only a single antenna of the same pair, the output from each receiver being connected to a single information-acquisition automaton, the antenna of a pair being placed at a distance of at least A/4 from the antenna of the other

pair so as to protect against the effects of null spots resulting from the mutual cancellation of waves coming from the same emitter but having followed different propagation paths and having undergone different, or even opposing, amplitude and phase transformations.
Advantageously, the antennas of the various pairs are installed at the distant edges of the same roof of a building.
Preferably, the frequency associated with the wavelength A of the system is chosen among the free frequencies or the dedicated frequencies.
More preferably, said frequency is between 100 MHz and 900 MHz inclusive.
More particularly still, the system according to the invention also comprises other antennas and other receivers, either directly coupled or not coupled to each other.
Advantageously, said acquisition automaton is associated with a communications card for sending the information collected to a communications network.
Generally speaking, the data collected come from any type of measurement sensor.
In particular, said sensors are volume, temperature, pressure, speed and/or position sensors.
Advantageously, the system according to the invention is used for the remote reading of water meters, or for the management of a stock of garbage dumpsters, each dumpster being equipped with a sensor/emitter.

The invention will be better understood on reading the following detailed description with reference to the drawings, in which:
the single figure shows a diagram of the reception system according to the invention.
The object of the present invention is therefore to equip a fixed reception system A for a radio channel, fixed network transmission system for information emitted at a single wavelength A by a plurality of emitters (not shown) associated with measurement sensors.
The emitters are spread over a geographic area and each send the information collected to the reception system A for the collection of all the information emitted in said geographic area. The information is generally emitted in digital form.
The reception system A comprises at least two antenna 1 - receiver 2 pairs I, II.
The antenna 1 and the receiver 2 of a pair I or II are connected to each other by a coaxial cable 3.
In the example shown in the drawing, the system A comprises two antenna 1 - receiver 2 pairs I and II. Each receiver 2 of a pair I or II is associated with only a single antenna 2 of the same pair I or II.
In the particular context of the invention as shown, the two antennas 1 of the two pairs I and II should be separated from each other by a suitable distance of more than a quarter of the wavelength so as not to interfere mutually, for example by coupling, and so as not to be situated in the same null spot. The use of more than two antennas might be envisioned, even though the improvement to be expected will be less marked.

This configuration allows in particular protection against the effects of null spots resulting from the mutual cancellation of waves coming from the same emitter and having followed different propagation paths and having undergone different, or even opposing, amplitude and phase transformations.
Thus, the performance of the receivers with identical emitter characteristics is significantly increased.
In the example shown in the drawing, the system A also comprises another antenna 1' - receiver 2' pair III, but this is not designed to intervene in cancelling the null-spot effect.
It might, for example, consist of a directional antenna 1' intended specifically to gather the information from a particular geographic area in the general geographic area of coverage of the reception system.
In the example shown, the antenna 1' and the receiver 2' are also directly associated with each other by a coaxial cable 3. Moreover, the antenna 1' of the pair
II is associated with only a single receiver 2' of the
same pair. Of course, the system A according to the
invention might also comprise other antennas and other
receivers directly coupled or not coupled to each
other, according to requirements. These other antennas
and these other receivers will not intervene in the
cancellation of the null-spot effect.
In practice, the antennas of the various pairs I, II or
III will be able to be installed at the distant edges
of the same roof of a building.
As shown in detail in the figure, the output from each receiver 2 is connected to a single information-acquisition automaton 4 provided in order to organize and process the information received.

The acquisition automaton 4 will equally receive the decoded messages from one or the other of the receivers 3 and will ensure, if necessary, the deduplication of data so as not to preserve the redundant data pointlessly. This processing might equally well be carried out by a central information system receiving the data collected and transmitted to it by the acquisition automaton 4.
The receivers 3 are connected to the acquisition automaton 4 by series connections 5.
The acquisition automaton 4 might equally be powered directly from the mains 6 or else from one or more batteries 7, depending on what is available at the site of installation of the reception system of the invention.
Finally, the acquisition automaton 4 is connected to a communications card 8 that effects the connection between the reception system of the invention and the communications network of the company that has installed it (represented by the arrow B).

CLAIMS
1. A fixed reception system (A) for a radio channel,
fixed network transmission system for information
emitted at a single wavelength A by a plurality of
emitters generally associated with measurement sensors,
the emitters being spread over a geographic area, to
the reception system (A) for the collection of all the
information emitted in said geographic area,
characterized in that it comprises at least two antenna
(1) - receiver (2) pairs (I, II), each receiver (2) of
said pair (I, II) being associated with only a single
antenna (1) of the same pair (I, II), the output from
each receiver (2) being connected to a single
information-acquisition automaton (4), the antenna (1)
of a pair (I, II) being placed at a distance of at
least A/4 from the antenna (1) of the other pair (I,
II), so as to protect against the effects of null spots
resulting from the mutual cancellation of waves coming
from the same emitter but having followed different
propagation paths and having undergone different, or
even opposing, amplitude and phase transformations.
2. The system as claimed in claim 1, characterized in
that the antennas of the various pairs (I, II) are
installed at the distant edges of the same roof of a
building.
3. The system as claimed in one of claims 1 or 2,
characterized in that the frequency associated with the
wavelength A of the system is chosen among the free
frequencies.
4. The system as claimed in one of claims 1 or 2,
characterized in that the frequency associated with the
wavelength A of the system is chosen among the
dedicated frequencies.

5. The system as claimed in claim 2 to 4, characterized
in that said frequency is between 100 MHz and 900 MHz
inclusive.
6. The system as claimed in any one of claims 1 to 5,
characterized in that it also comprises other antennas
(!') and other receivers (2').
7. The system as claimed in claim 6, characterized in
that the other antennas (!') and the other receivers
(2') are directly coupled to each other (III).
8. The system as claimed in any one of claims 1 to 7,
characterized in that said acquisition automaton (4) is
associated with a communications card (8) for sending
the information collected to a communications network
(B) .
9. The system as claimed in any one of claims 1 to 8,
characterized in that the data collected come from any
type of measurement sensor.

10. The system as claimed in claim 9, characterized in
that said sensors are volume, temperature, pressure,
speed and/or position sensors.
11. The system as claimed in any one of claims 1 to 10,
characterized in that it is used for the remote reading
of water meters.
12. The system as claimed in any one of claims 1 to 10,
characterized in that it is used for the management of
a stock of garbage dumpsters, each dumpster being
equipped with a sensor/emitter.