FR2571151A1 - MULTIFUNCTION INTEGRATED SYSTEM FOR IDENTIFICATION, NAVIGATION, TRAFFIC CONTROL, ANTICOLLISION AND COMMUNICATIONS - Google Patents

Abstract

INTEGRATED MULTIFUNCTIONAL SYSTEM TRANSMITTING MESSAGES INCLUDING A PREAMBLE USED FOR THE ACQUISITION OF THE SYNCHRONIZATION AND A TEXT FOLLOWING THE PREAMBLE CONTAINING THE INFORMATION TO BE TRANSMITTED. PREAMBLE PULSES ARE MODULATED WITH WIDEBAND SPECTRUM SPREAD, TEXT PULSES ARE MODULATED WITH LOWER BAND SPECTRUM SPREAD USING FREQUENCY JUMPED WIDEBAND DISPERSION. PREAMBLE AND TEXT RECEPTION IS DONE IN SPECIFIC RECEIVERS AND ONLY PREAMBLE RECEIVERS ARE PRESET ON A DESIRED CHANNEL. APPLICATION TO IDENTIFICATION, NAVIGATION, TRAFFIC CONTROL, ANTI-COLLISION.

Description

EIS.BOU 2571151

  The present invention relates to a multi-system integrated

  function, identification, navigation, traffic control, anti-

collision and communications.

  The need for an integrated multifunctional system appeared a few years ago, offering a relatively economic solution and an increased capacity to deal with the problem posed by the various functions required to support a mobile phone. air, land, sea, from its point of departure to its point of arrival and the execution of the mission entrusted to it. Thus, an air mobile is supported from his departure from the parking area until his return to another parking area, the system intervening successively for all the functions that occur between these two moments. All these functions, the most important of which are mentioned in the title of the application, are fulfilled by already existing and operational systems, and the primary radars for the detection of a mobile operating in the airspace covered by its antenna will be recalled for the record. secondary radars which interrogate according to a given code an aircraft equipped with an answering machine, on its altitude and its identity, the interferometric bases allowing the location of the aerial mobiles and all the systems of navigation and aids to the landing. All these particularized systems are obviously susceptible of progress and have been perfected, but their grouping so that the various evoked functions are assumed proves to provide a solution more expensive than a system.

integrated multifunction.

  An integrated multifunction system provides a solution

  advantageous to the complex problem posed, facilitating communication

  cations and the design of interfaces, also facilitating

  changeability of equipment and functions, allowing the organization

  sequential operation to operate the equipment at full load and reconfigure the system according to its state by the hierarchy of functions according to the mission or phase of the flight or

missions in the general case.

  In general, in multifunctional integrated systems, the information exchanges, taken in their broad form, between the ground and the mobiles or between the mobiles are done by coded signals c of the same type, whatever the function envisaged, and the transmitted messages are divided into time, code and frequency, the transmission frequencies being distributed in a wide band. Means are obviously provided, both on the ground and on board mobiles to ensure a perfect synchronization of the various elements of the system in the establishment of different functions

that he provides.

  According to the prior art, there may be mentioned a system called "Sintac

  1 "developed by the Applicant, for a multi-system integrated

  function fulfilling the functions of identification, navigation,

  traffic control, collision avoidance and communications in which the emissions are organized by division in time, code and frequency in recurrences of fixed length, such recurrence being a so-called basic recurrence or in recurrences of length sub-multiple of the basic recurrence . The transmitted messages are all of the same structure and consist mainly of two parts:

  a preamble for the acquisition of the message and its synchronization

  tion and a text bearing the information of the message to be transmitted.

  The preamble consists of a number of

  each of which is coded according to a law which can be pseudo-random whose time distribution can also follow a pseudo-random law. By correlation of the pulses on the one hand and their succession in the preamble on the other, we determine

  preamble acquisition and synchronization.

  In fact, the arrival decision of the preamble and therefore its acquisition can not be taken on a single impulse. The preamble must therefore include a certain number of pulses on one or

  several frequencies known in advance and variable by a recursion

  to each other in code, frequency and time distribution also known. This variation of the frequency, the code and the relative position in the time of the pulses is done according to a pseudo-random law, as already indicated, a law which precisely makes it possible to correlate the preamble without ambiguity. This pseudo-random modulation is relatively low spread spectrum and in an example under a variant of the prior art cited, known as "Sintac 2", also developed by the Applicant, this code is 32 chips, each chips being 0.2 jas

  with a dispersion band of the order of 5 MHz.

  The text following the preamble uses pulses of the same type as before with a law of code and frequency

  also variable pseudo-random, emitted with frequency jumps

  quence in each elementary transmission interval in a band of the order of 250 MHz by way of example. These pulses are modulated, like those of the preamble with spread spectrum

relatively weak.

  The transmission of the preamble over several frequencies distributed over the entire frequency dispersion band of the system makes it possible to mitigate, to a certain extent, the inconvenience of interference, which could be done in the case of

  fixed frequency, after detection of this frequency.

  On the receiving side of the preamble, however, it is necessary to provide as many receivers as the transmission frequencies of the preamble, 8, 4, 2 or I depending on the performance of the system and

  corresponding security of the reception.

  After the acquisition of the preamble and therefore the synchronization,

  the reception of the text can be undertaken with a single receiver.

  This integrated system thus has drawbacks that are: a number of receivers in a reception chain, too large, and a protection against selective interference relatively low.

  The object of the invention is to overcome these disadvantages.

  According to the invention, the integrated multifunctional system, of identification

  fication, navigation, traffic control, anti-collision and communi

  cations, transmitting messages containing a preamble

  to the acquisition of the synchronization of the message and a text to the

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  following the preamble and bearing the information to be transmitted is characterized in that the pulses of the preamble and of the text are modulated differently, the pulses of the preamble being modulated with spreading of the broad band spectrum, and transmitted at fixed frequencies, the text pulses being modulated with more limited band-width spreading, transmitted with frequency hopping distributed in the total operating band of the system. Other features of the invention will appear during

  of the exemplary embodiment of the receiving part of the

  multifunction integrated system, given using the figures which represent: - Figure 1, the form of the message according to the invention; - Figure 2, a configuration of simultaneous reception of a preamble and two interlace texts;

  - Figure 3, the division of a basic recurrence into three sub-

  recurrences; - Figure 4, a reception cat in the multifunction system according to the invention;

  - Figure 5, a variant of a reception chain allows-

  both the simultaneous reception of two preambles in two different channels distributed in two sub-bands; - Figure 6, a variant of Figure 5 with two antennas; FIG. 7, a variant of FIG. 5 with acquisition in four channels divided into two sub-bands, and simultaneous reception of ten texts; - Figure 8, a receiving station according to the invention, of minor importance; - Figure 9, a simplified receiving station according to the invention; - and Figure 10, a very simplified station limited to the

receipt of only the preamble.

  As noted in the introduction, the multifunction integrated system according to the invention is characterized by a different modulation of the preamble pulses and text, for the purpose

  to use a reduced number of receivers for the main preamble

  payment, the number of text receivers being determined by the

  capacity of the station where the system is implanted.

  Figure I schematically shows the form of the message in the integrated system according to the invention. This message has a preamble! with a large synchronization and a text 2 with the fine synchronization 3. The preamble I consists of very broadband spread spectrum modulated pulses, transmitted at fixed frequency with pseudo-random law, distributed

  in time, this distribution being defined by a subset

  emission recurrence. Emissions are done, as following the art

  previous, by recurrences that define the pseudo-legal

  used, with this difference that according to the invention,

  only the receipt of the preamble determines the length of the recursion

  basis of the program. It is therefore possible to use according to the invention and use recurrences shorter than those of the prior art called recurrences, with the advantage of using more rationally the time and thereby increase the capacity of the system. The length of the sub-recurrences depends on the hardware of the system, defined among other things by the range; the class of material also depends on the scope of the processing capacity and

  the carrier used. According to the invention therefore, it is possible

  depending on the case, several recurrence lengths and for the scope currently envisaged, the under recurrence is of the order

  one third of the recurrence of the prior art.

  In the example cited, the fine sync 3 and the text 2 are also constituted by modulated spread spectrum pulses but with a more limited band, with frequency jumps at each segment. It is however possible to transmit the fine sync with the preamble so with a dispersion in a band

  large. In a current preferential example, the preamble is con-

  with 12 pulses of 6.4 ps, 100 MHz band, the elementary pulses or chips being 10 ns. They are divided into two groups 4 and 5 of six pulses achieving a total spread of 200

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  MHz with a fill rate of 117 in total.

  The text 2-consists of pulses having the same length 6.4 ps as those of the preamble but with a more limited spectrum spread, of the order of 5 MHz, the elementary pulses or chips having 0.200 ps, with jumps of frequency scattered in the band

  total system. The fill rate of the pulses is 1/4.

  The standard text consists of words "in the head" using the code 16/7 and information words using codes 31115 Reed Solomon.

  Fine sync 3 consists of eight pulses.

  The filling rate of the preamble and the text is

  to minimize the internal interference of the system, between the preambles and between the preamble and the texts received simultaneously, allowing their interlacing to ensure

the maximum capacity of the system.

  FIG. 2 represents a simulated reception configuration.

  tane cP a preamble 6 at fill rate 1/7 and two texts

  interlaced 7 and 8 at 1/4 fill rate.

  This simultaneous reception is made possible as a result of the criterion of acquisition of the admitted preamble, that is to say reception of a fixed number of preamble pulses on the set and the redundancy of the text. Under these conditions there is according to the invention a single preamble receiver to provide and as many receivers of

  text as messages to receive simultaneously.

  However, it is possible with a lower message fill rate (1/8) instead of 1/4, to receive two texts

  with interleaving in the same receiver.

  It is also possible to receive simulta-

  ambules in the different channels defined by the pseudo-

  random. It is then necessary to have as many circuits of

  correlation of impulses and preamble, only channels considered.

  To avoid preamble emissions at the beginning of recurrences

  In order to use time as much as possible, the recurrence is divided into sub-recurrences of sufficient length, however, to allow reception of preambles up to the limit of the system range. the lower the range, the shorter the recurrence. The recurrence determines the preamble codes following the channel and the text following the preamble; the text channel is triggered by the sync acquired by the preamble and is maintained until the end of the indicated text

in the word in mind.

  FIG. 3 represents the division of the basic recurrence 9 identical to that of the prior art into three subreprurrences 91, 92,

  93 with the receipt of a preamble 1 in each sub-recurrence.

  This results in receiving interlaced messages with as many

  receivers of text than interleaved messages to receive, that is,

  say three in the example presented. This is not limiting and it is possible to receive more than one preamble in a recurrence and to receive a higher number of interlaced messages as well, provided that the number of text receivers is increased in the same proportion. In 10 we have shown the reception capacity of a reception chain of the prior art which comprises eight receivers whereas there is only one message per recurrence of

base 9.

  It can be seen that the reception capacity of the integrated system according to the invention is clearly greater than that of the prior art for the same message redundancies. Subreprurrence emission also eliminates the possibility of selective interference over time and improves

  protection of the system against enemy interference.

  Figure 4 shows the constitution of a reception chain.

  in the multifunctional integrated system according to the invention. Starting from the input E1, there is the very broadband acquisition receiver 11 processing the preamble of the message, optionally followed by a selective frequency limiter circuit 12, a pulse correlator 13, a correlator preamble 14 and an acquisition decision circuit 15 whose output feeds a circuit 16 said information processing. The input E1 is also connected to a receiver 17 called text receiver whose bandwidth is lower than that of the preamble receiver 11 but equal to that of the prior art, followed by a limiter 18, P of a correlator pulses 19 whose output is connected to the processing circuit 16. S represents the output of the reception chain. In E2 we have

  presented a control input of circuit 16.

  The operation of such a receiver cat does not pose any particular problems, the functions of the various components of the chain being clearly defined. The fact that the frequency selective limiter circuit 12 is optional simply results in the desire to suppress selective interference. Under these conditions, the circuit 12 proceeds in a known manner to the analysis of the signal from the point of view of the frequencies, using the Fourier transform, and isolating the scrambled frequencies. The connection 20 between the pulse correlator 13 and the processing circuit 16 indicates the possibility of correlating the preamble in the circuit 16. The connection 200 accounts for the possibility of

  modify the codes according to the sub-recurrences allowing the

  different preambles. The connection 21 reports the changes made to the text codes and the connection 210 to the modifications to be made to the receiver 17 to take account of the

Frequency hopping

  FIG. 5 represents a reception channel of the integrated system according to the invention allowing the simultaneous reception of the preambles in two different channels in the total band of the order of 200 MHz and of four texts in one or the other o the two channels. According to the invention, there is a receiver by

  preamble, and four text receivers, one for each text.

  From the antenna 22, there is a duplexer 23 ensuring the separation between the emission from the transmitter 24 connected to the two modulators 25 and 26 respectively, preamble and text and the receiving portion connected to the output of the preamplifier 27 at

  very wide band covering the total band of dispersion of

  system (of the order of 250 MHz). At the output of the preamplifier

  In the first embodiment, two acquisition reception channels similar to the chain described in FIG. 4, each comprising a 28-280 acquisition receiver and a limiter, are present in parallel.

selective frequency 29-290.

  At each limiter 29-290 are connected two chains in

  parallel, one per channel, each with a correlator of acqui-

  programmable broadband 30-31, 300-310, followed by a correlation

  preamble 32-33, 320-330 and a correlation peak adder or decision circuit 34-35, 340-350 whose outputs

  respective ones are connected to the information processing circuit 16.

  mation. The output of the preamplifier 27 is also connected to four text receivers 36 to -39 in parallel, each followed by a programmable correlator, with a low bandwidth in the order of

5 MHz, 40 to 43.

  Note that in the case of acquisition in several channels, only the correlation circuits are multiplied, while following

  the prior art, the complete reception chain from the pre-

  broadband amplifier 27 would have been multiplied. According to the invention

  tion, there is an advantage that it is possible to use a less

large number of circuits.

  The text receivers are used independently of the channels, their choice being determined by the circuit 16 receiving the preamble. This faculty allows when necessary, to make a certain priority play in the case of total occupation of

text receivers.

  Figure 6 shows a variant of Figure 5 in which two antennas are used, a high antenna and a low antenna. The acquisition in this case is divided between the two antennas 220 and 221, each functioning for the preamble only for half of the total band, or 100 MHz in the example considered. There are therefore two preamplifiers 27 and 270, each supplying one of the reception-acquisition chains, identical to those of FIG. 5. The receiving part of the texts is not modified with respect to FIG. 52 allows, the texts being received in the total band of each antenna, to switch to the antenna providing the best reception or to receive simultaneously on both antennas, a switch 54 allowing the transmission to switch the transmitter on the one or the other

  antenna 220-221 or transmit simultaneously on both antennas.

  FIG. 7 represents a receiving station of the integrated system according to the invention, allowing the acquisition of the four

  channels in the total band and the reception of 10 simultaneous

  ously. This imposes on the output of each frequency selective limiter 29, 290 four correlation chains for the acquisition 401-404 and 40104040 and ten reception channels 500 to 510 of text, in parallel, similar to those of FIG. . By 250 we have represented all the modulators for the emission of preambles and texts. It will be noted that the correlation and reception string circuits are not detailed, since

  similar to those in Figures 4, 5 and 6.

  As we have seen, all the receiving stations of the system according to the invention which have been described have a separation of the acquisition receivers and the text receivers in which

  decodes the texts. This arrangement makes it possible

  to what is necessary, one can thus increase the reception capacity on the one hand and reduce this capacity on the other hand, while

  retaining the desirable protection against enemy interference.

  Thus, if FIG. 7 is representative of a station of great importance, FIG. 8 represents a much smaller station as it exists on an armored vehicle for example. The acquisition is made from a single receiver 28 covering the 100 MHz band, for example, and in two channels, an asynchronous identification channel by question and answer in which the period of variation of the pseudo-random codes is long. having a pulse correlator 55, a preamble correlator 56 and an adder 57 of correlation peaks and a multifunction channel also having a pulse correlator 58, a correlator

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  it preamble 59 and a correlation peak adder 60. A

  only text receiver 61 is provided with a correlator 62.

  Transmitter 24 transmits at reduced power, for a short range, and is powered by two acquisition modulators 25 and text and fine synchronization 26. FIG. 9 represents an even more simplified station, in which one merely transmits and receive a preamble, used for identification by question and answer. The references of the circuits

are the same as figure 4.

  Figure 10, even more simplified, represents a station

  in which we simply limit ourselves to the receipt of the preamble.

  It is mainly used for question and answer identification for a carrier using a particular high-band or laser-type device for interrogation. Its use simplifies answering machines that remain identical in all identification configurations while maintaining a high level of protection

against enemy interference.

  Thus, an integrated multifunctional system has been described which pre-

  There are a number of important advantages over prior art systems, while maintaining interoperability with the prior art systems currently being developed. This interoperability can be ensured either on the side of the system according to the invention or on the side of the system falling within the prior art. In the first case, it is necessary to equip the text receivers of the system according to the prior art; in the second case, it is necessary

  to equip the terminals according to the prior art with circuits for acquiring

according to the invention.

Claims (18)

  1. Multifunctional integrated identification, navigation, traffic control, collision avoidance and communications system transmitting messages comprising a preamble for acquiring synchronization of the message and a text following the preamble and bearing the information to be transmitted , characterized in that the   impulses of the preamble (1) and of the text (2) are modulated pseudo-   randomly differently, the pulses of the preamble (1) being modulated with spreading of the broadband spectrum and transmitted at fixed frequencies, the pulses of the text being modulated with shoring of the more limited band spectrum emitted with frequency hopping distributed in the total band -use of the system. 2. System according to claim 1, characterized in that the preamble (1) contains a large synchronization, while the fine synchronization (3) and the text (2) are transmitted according to the   second type of modulation, limited band.   3. System according to claim 1, characterized in that the   fine synchronization is issued with the preamble.   4. System according to claim 1, characterized in that the pulses of the preamble are transmitted at a fixed frequency with a code according to a pseudo-random law and that they are distributed in time, this distribution being pseudo-random defined by a sub = of erection, donrtla 1hguegr is determined from   to allow the reception of the preamble alone.   5. System according to claim 4 wherein the class of the material used is defined by the range, the processing capacity.   and the carrier, characterized in that the length of a sub-   recurrence depends on the scope of the hardware class of the system.   6. System according to Claim 5, characterized in that for a maximum range, the length of a sub-recurrence is   the order of one third of the length of the recurrence.   7. System according to Claim 1, characterized in that the   preamble pulses can be sent over several   quences, these frequencies being determined in a pseudo-random   in the different recurrences.   8. System according to Claim 7, characterized in that only one preamble receiver is used in the spreading band of the pulse modulation spectrum of the preamble, the frequency   this receiver being determined by the pseudo-legal random considered.   9. System according to claim 1, characterized in that   in the case of simultaneous reception of preambles on two   In the total spread spectrum of the preamble pulse modulation spectrum, a receiver per carrier is provided. 10. System according to Claim 1, characterized in that a reception channel comprises a very wideband preamble acquisition receiver (11), a pulse correlation circuit (13), a correlation circuit of preambles (14), a circuit of   acquisition decision (15) and a processing circuit (16).   11. System according to claim 1, characterized in that a reception chain comprises a text receiver (17) of relatively narrow bandwidth with respect to that of the preamble receiver, a limiter (18), a correlation circuit c impulses   text (19) and a processing circuit (16).   System according to Claim 10, characterized in that a frequency selective limiting circuit (12) is interposed between the preamble acquisition receiver (11) and the correlation circuit. pulses (13).   13. System according to one of claims 1, 9, 10 or 11,   characterized in that, the preamble pulses being divided into two groups occupying the total spectrum spread spectrum of the preamble modulation on two different carriers, and a number of texts, the reception chain comprises a single receiver covering the total band of the system (27) feeding two preamble acquisition chains in parallel and as many strings   receipt of texts that there are texts to receive.   14. System according to Claim 13, characterized in that each of the reception channels of a preamble comprises an acquisition receiver (28, 280) and optionally a frequency selective limiter (29, 290), and two channels parallel one by   carrier, each having a pulse correlation circuit   preamble sections (30-31-300-310), a preamble correlation circuit (32 - 33 - 320 - 330) and an acquisition decision circuit (34-35-340-350).   15. System according to one of claims 13 or 14, characterized   by the fact that in the case of acquisition in several channels, only   the correlation circuits relating to the preambles are multiplied.   16. System according to claim 13, characterized in that the text receivers (36 to 39) are selected by the circuit of   treatment (16) following the acquisition of a preamble.   17. System according to claim 10, characterized in that the preamble correlation is done directly in the circuit of treatment (16).   18. System according to one of claims 1 to 17, characterized by   the fact that it is interoperable with the systems of the prior art.