EP0629059B1 - Système de transmission numérique à étalement de spectre obtenu par codage pseudo-aléatoire basse fréquence de l'information utile et procédé d'étalement et de compression de spectre utilisé un tel système - Google Patents
Système de transmission numérique à étalement de spectre obtenu par codage pseudo-aléatoire basse fréquence de l'information utile et procédé d'étalement et de compression de spectre utilisé un tel système Download PDFInfo
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- EP0629059B1 EP0629059B1 EP94401282A EP94401282A EP0629059B1 EP 0629059 B1 EP0629059 B1 EP 0629059B1 EP 94401282 A EP94401282 A EP 94401282A EP 94401282 A EP94401282 A EP 94401282A EP 0629059 B1 EP0629059 B1 EP 0629059B1
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- integer
- sequences
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- random phase
- integers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K1/00—Secret communication
- H04K1/02—Secret communication by adding a second signal to make the desired signal unintelligible
Definitions
- the field of the invention is that of modem transmission of digital signals and in particular that of spread spectrum modems. More specifically, the The present invention relates to a transmission system with spread of spectrum between a transmitter and a receiver digital signals where spread spectrum is obtained by pseudo-random coding of information useful to transmit.
- the invention is particularly applicable in wireless telecommunications in the military field.
- ECCM Electronic Counter-CounterMeasures
- code or sequence spreading the signal useful to transmit by a code, called code or sequence spreading, from a pseudo-random generator whose clock signal frequency is much higher than the maximum frequency of the wanted signal. Number of bits of useful information transmitted by Hz is therefore very low.
- Figure 1 shows a timing diagram for understand the principle of spectrum spreading by a spreading sequence.
- a useful SAT signal to be transmitted here coded in two +1 and -1 levels following NRZ coding, is multiplied by a SE cyclic spreading sequence, also coded on two levels.
- the signal resulting from the multiplication is the ST signal transmitted from the transmitter to a receiver after modulation.
- the modulated ST signal transmission medium generally consists of a radio link.
- signal multiplication received ST with the same spreading sequence SE (same phase and same frequency) makes it possible to reconstitute the useful signal SAT.
- Sequence spread spectrum transmission direct is usually used to give the signal transmitted better discretion, resistance to ECM (Electronic CounterMeasures) interference and a resistance to selective fading.
- ECM Electronic CounterMeasures
- the ratio between the chip time and bit time, the chip time corresponding to the duration of a bit of the spreading sequence and the time bit to that of the wanted signal is greater than this spreading gain higher, the more the transmitted signal is able to be transmitted discreetly and therefore resist ECM devices intended to detect it and, possibly, to jam it.
- An essential step in ECM analysis is to determine the spreading hazard of the signal received because this step allows you to penetrate the information content of the signal received, ie to reconstitute the useful signal.
- sequence generator direct must operate at the transmission frequency of chips, or at a frequency of the order of several MHz. he it is therefore necessary to install this generator in an ASIC, which increases the hardware complexity and the cost of hardware development.
- the present invention aims in particular to overcome this drawback.
- one of the objectives of the invention is to provide a signal transmission system digital, where spread spectrum is implemented, this system that does not require a hazard generator operating at the chip frequency. It is therefore more simple to make and less expensive, while allowing large spread of the useful signal spectrum intended for resist ECM devices.
- Another object of the invention is to provide a such a system where spectrum spreading is carried out from orthogonal sequences, for example using M-type sequences (also known as maximum length or Hadamard), well known in the art field of digital signal transmission.
- M-type sequences also known as maximum length or Hadamard
- An additional objective is to provide a process transmission of spread digital signals spectrum where the spreading is carried out at the bit frequency and not at the chip frequency.
- the M sequences of q integers are preferably made up of Hadamard sequences.
- the digital signal to be transmitted SN is applied, here via a serial access, to coding means 21 which supply, for each block of k bits of the signal SN, a coded sample E c taking an integer value included in the set ⁇ 0, ..., N-1 ⁇ , each integer value being representative of the k bits of the corresponding block.
- the coding means 21 can for example be constituted by a simple binary-decimal converter and the bit rate leaving the coding means is then k times lower than the bit rate entering.
- the coding means 21 can optionally also interleave the bits of the SN signal.
- the coded samples E c are applied to means 22 for combining these samples with samples E a originating from a pseudo-random generator 23, which will subsequently be called phase random generator.
- the combination means 22 comprise a transformation algorithm which transforms each coded sample E c into an integer s included in the set ⁇ 0, ..., M-1 ⁇ , with M integer greater than N.
- s f (E vs , E at ) where f is any function taking its values in ⁇ 0, ..., M-1 ⁇ and E has a sample of phase randomness.
- This modulo M addition apart from the fact that it can be implemented by a very simple algorithm to implant, provides optimal resistance performance at ECM interference.
- Each integer is then supplied to means 24 of generation of signals providing, for each integer s, a corresponding SQ sequence of q samples, each sample q being an integer.
- 24 generation means of signals transform each integer s into a SQ sequence, this transformation being bi-unequivocal, that is to say that a given integer s corresponds to a single sequence SQ and reciprocally.
- the signal generator can for example be consisting of a transcoding table.
- a transcoding table We will refer usefully to French patent n ° 2,337,465 in the name of COMPAGNIE IBM FRANCE TM which describes sequences called CAZAC which are periodic pseudo-random sequences of complex numbers that have an autocorrelation function periodic whose only the first coefficient is not zero and of which all complex numbers have an amplitude constant.
- CAZAC periodic pseudo-random sequences of complex numbers that have an autocorrelation function periodic whose only the first coefficient is not zero and of which all complex numbers have an amplitude constant.
- the generation of such sequences can be generalized to obtain sequences made up of whole numbers, these sequences being orthogonal between them, that is to say having properties optimal autocorrelation.
- Gold sequences which are quasi-orthogonal, like those of Kasami, or those called polyphases.
- the means 24 generate sequences SQ which are substantially orthogonal to one another.
- the signal generation means 24 can transform each integer s into a sequence SQ of q bits (samples each taking a value in ⁇ 0,1 ⁇ ) according to table 1 below.
- Input value s SQ Suite generated 0 0000000 1 1110100 2 0111010 3 0011101 4 1001110 5 0100111 6 1010011 7 1101001
- Each suite of q bits is produced by circular shifts of a sequence of maximum length of length 7, excluding the first suite always consisting of zeros.
- These suites have quasi-orthogonality properties, say that for two different and arbitrary sequences, the sum of the EXCLUSIVE OUs of each term is equal to 4.
- each block of k bits of signal SN has been transformed into a sequence Corresponding SQ, each SQ suite comprising a pseudo-random component.
- Useful information is coded in this SQ suite and the different suites are orthogonal or quasi-orthogonal to each other. Since then that M and q are large before k or before N, we understand that this coding operation consisted in increasing by importantly the number of samples to be transmitted and that we have therefore spread the signal spectrum useful SN using hazards provided at low frequency.
- the main advantage of the invention lies precisely in this coding which is carried out at the bit frequency and not not at the chip frequency (where the spectrum spread is performed by direct sequence).
- the working frequency of means described so far can be very weak, around 16 Kbits, compare with 10 Mchips in the case spread spectrum by direct sequence.
- samples may take larger values, depending on the modulation used in transmission means 25 to which SQ suites are provided.
- These transmission means 25 supply a signal STR transmitted to the attention of the receiver. They can be from any type, analog or digital.
- the means 25 are digital and have a phase shift modulator 28.
- This modulator 28 is by example of type MPSK (Multiple Phase Shift Keying) where M corresponds here to the number of possible values of samples q of the sequences SQ and therefore the number of states of phase of the modulated signal STR. It is for example possible to perform a BPSK modulation if the SQ suites are exclusively made up of bits, QPSK modulation if the integers of the SQ suites are each included in the set ⁇ 0, 1, 2, 3 ⁇ , and a 64-PSK modulation if the whole SQ suites are each included in the set ⁇ 0, 1, ..., 63 ⁇ .
- the phase shift modulator 28 can also be of the QAM type. It provides a modulated signal noted SM.
- the transmission means 25 may also include means 26 for spreading spectrum by spreading sequence.
- the spreading sequence SE is generated by a spreading sequence generator 27.
- the bits of the sequences SQ take their values in ⁇ 0,1 ⁇ and that the chips of the sequence d spreading SE also take their values in ⁇ 0,1 ⁇ .
- Each sample bs / i produced by the signal generation means 24 is added modulo L to G hazards e s belonging to the set ⁇ 0, 1, ..., L-1 ⁇ and coming from the generator 27, where G represents the spread gain by direct sequence.
- G represents the spread gain by direct sequence.
- the increase in bit rate caused by this processing is equal to G.
- SQE the output signal of the means 26, denoted SQE, which is applied to the modulator 28.
- Each sample a i of an SQE sequence takes its value in ⁇ 0, 1, ..., L-1 ⁇ .
- mapping function g of the modulator must respect the relationship: when a spread by direct sequence is implemented (G> 1).
- the impulse response h e of the emission filter is assumed such that:
- the means 26 of spectrum spreading by sequence direct are of course optional in the invention and are therefore shown in broken lines.
- the transmission means 25 can also include frequency escape means 29, 30, also optional and therefore shown in broken lines, suitable to modify the carrier frequency of the signal transmitted to the receiver.
- the frequency escape is to change frequently of carrier frequency in order to further broaden the spectrum of the signal transmitted to the receiver.
- the modulated signal SM in baseband or in intermediate frequency, is applied to a multiplier 29 receiving a signal from carrier frequency of a generator 30.
- phase 23 generator allows low-frequency coding of the signal to be transmitted and allows to modify in a pseudo-random way the phase of the signal transmitted when the modulation is of MPSK type.
- generator 23 and the means of combination 22 provide a phase escape function performed at low frequency. Amplitude modulation, also pseudo-random, the signal to be transmitted comes combine with this phase escape when the modulation is of the QAM type (modification of the phase and the amplitude of the transmitted signal). This is how the system transmission of the invention provides a high resistance to ECM interference.
- the output signal STR of the transmission means 28 is transmitted over the air to receiver 31 whose diagram synoptic is given in figure 3.
- the receiver 31 receives a corresponding signal STRr to the STR signal noisy by the transmission medium. he includes reception means generally referenced by 40 restoring the sequences SQ of q whole numbers, noted SQr at the receiver.
- Means of reception 40 here include means 32 for removing the carrier frequency controlled by a local oscillator 33.
- the means 32 conventionally comprise two mixers controlled by quadrature clock signals and we obtains at the output of these means two quadrature signals.
- the local oscillator 33 operates in synchronism with that of the transmitter, referenced 30. This synchronization can be obtained by known means.
- the output signal of the means 32 is noted SMr and corresponds to the transmitter SM signal.
- the signal SMr is applied to means 34 of spectrum compression to suppress spreading by direct sequence possibly performed at the transmitter 20.
- Spectrum compression means are notably described in "Digital Communications" by J.G. PROAKIS, McGraw-Hill TM, Chapter 8.
- Those depicted in the Figure 3 include a sampler 35 controlled at the frequency chip Fc followed by a module 36 for compression of spectrum.
- Module 36 includes a complex multiplier 37 followed by a summator 38.
- the multiplier 37 receives a direct sequence SE of a generator 39, this sequence direct SE being identical to that generated by the generator 27 of the transmitter 20.
- the phase timing of these two direct sequences is obtained by known means.
- the summator 38 calculates, for each block of G consecutive samples r k from the multiplier 37, the following sum: where e sk is the value of the chip at time k of the direct sequence SE and * denotes the conjugate complex. This summation eliminates spectral spreading by direct sequence.
- Each sum U k therefore corresponds to a sample ⁇ i of the signal STR transmitted to the receiver.
- modules SQr identical to the suites SQ originating from the means 24 for generating signals from the transmitter 20.
- SQr suites are applied to means 45 for processing that have the function of performing a demodulation of the received signal and removing the random phase E is introduced at the transmitter 20 by the generator 23 hazards.
- the correlation means 41 therefore receive a SR reference signal consisting of the different sequences SQ can be generated at transmitter 20, this is to say those for example represented in tables 1 or 2.
- the advantage of generating orthogonal sequences or quasi-orthogonal using the generator 24 of Figure 2 (and not any sequences) is that it is easy to detect a correlation of these signals.
- the calculated correlations provide sums C 0 to C M-1 which each correspond to one of the integers from the combining means 22 of the transmitter 20. These sums are applied to a demultiplexer 42 receiving from a generator 43 a signal E a identical to that generated by the generator 23 of the transmitter, and in phase with it.
- the demultiplexer 42 selects N sums C S from M as a function of the value of the hazard E a .
- the demultiplexer 42 performs an inverse function f -1 to remove the phase hazard introduced at low frequency on transmission.
- the demultiplexer 42 thus selects the samples C s as a function of the hazard E a .
- Each sample d i therefore corresponds to a sample E c of the emitter.
- These samples d i are then applied to decoding means 44 performing an inverse operation to that of the coding means 21 of the transmitter 20. They can also carry out a deinterlacing of the decoded samples if the coding means perform an interleaving of the samples coded.
- the output signal SNr of the decoding means 44 then corresponds to the digital signal SN of the transmitter.
- the processing means 45 then only comprise correlation means such as 41, receiving the signal E a .
- the present invention applies for example to transmission systems where error correcting codes are used and where an alphabet of orthogonal signals of very large size, larger than the alphabet used by the error correction code is available.
- the elements of the alphabet not used by the code can be used for low-frequency pseudo-random coding of signal to be transmitted, thereby improving low cost the robustness of the system with regard to interception.
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Compression, Expansion, Code Conversion, And Decoders (AREA)
- Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
- Transmission Systems Not Characterized By The Medium Used For Transmission (AREA)
Description
- l'émetteur comporte successivement :
- des moyens de codage recevant ce signal numérique et fournissant, pour chaque bloc de k bits du signal numérique, un échantillon codé prenant une valeur entière comprise dans l'intervalle [0, N-1], chaque valeur entière étant représentative des k bits du bloc dont elle est issue ;
- des moyens de combinaison des échantillons codés avec des échantillons issus d'un générateur d'aléas de phase pseudo-aléatoire, les moyens de combinaison fournissant un entier compris dans l'intervalle [0, M-1] pour chaque combinaison d'un échantillon codé et d'un échantillon d'aléa de phase issu du générateur d'aléas de phase, M étant supérieur à N ;
- des moyens de génération de signaux fournissant, pour chaque entier compris dans l'intervalle [0, M-1], une suite de q nombres entiers correspondant à cet entier, les différentes suites étant orthogonales ou quasi-orthogonales entre elles ;
- des moyens d'émission des suites de q nombres entiers à l'attention du récepteur, les moyens d'émission comprenant un modulateur à décalage de phase dont le nombre d'états est égal à M ;
- le récepteur comporte successivement :
- des moyens de réception restituant les suites de q nombres entiers ;
- des moyens de traitement recevant d'une part les suites de q nombres entiers des moyens de réception et d'autre part des échantillons d'aléas de phase issus d'un générateur d'aléa de phase synchronisé avec le générateur d'aléas de phase de l'émetteur, les moyens de traitement assurant une démodulation des suites de q nombres entiers et effectuant une opération inverse de celle des moyens de combinaison pour restituer les échantillons codés ;
- des moyens de décodage restituant le signal numérique à partir des échantillons fournis par les moyens de traitement.
- la figure 1 représente un chronogramme permettant de comprendre le principe de l'étalement de spectre par une séquence d'étalement ;
- la figure 2 est un schéma synoptique d'un émetteur du système de transmission de la présente invention ;
- la figure 3 est un schéma synoptique d'un récepteur des signaux numériques transmis par l'émetteur de la figure 2.
Valeur de l'entrée s | Suite SQ générée |
0 | 0000000 |
1 | 1110100 |
2 | 0111010 |
3 | 0011101 |
4 | 1001110 |
5 | 0100111 |
6 | 1010011 |
7 | 1101001 |
Valeur de l'entrée s | Suite SQ générée |
0 | 11111111 |
1 | 10101010 |
2 | 11001100 |
3 | 10011001 |
4 | 11110000 |
5 | 10100101 |
6 | 11000011 |
7 | 10010110 |
- en modulation BPSK, L = 2 et on a g(0) = -1 et g(1) = 1
- en modulation QPSK, L = 4 et g(0) = 1, g(1) = j,
g(2) = -1 et g(3) = -j - en modulation 8PSK, L = 8 et g(k) = e2jkπ/8
Claims (8)
- Système de transmission d'un signal numérique (SN) entre un émetteur (20) et un récepteur (31), caractérisé en ce que :ledit émetteur (20) comporte successivement :des moyens (21) de codage recevant ledit signal numérique (SN) et fournissant, pour chaque bloc de k bits dudit signal numérique (SN), un échantillon codé (Ec) prenant une valeur entière comprise dans l'intervalle [0, N-1], chaque valeur entière (Ec) étant représentative des k bits du bloc dont elle est issue ;des moyens (22) de combinaison desdits échantillons codés (Ec) avec des échantillons (Ea) issus d'un générateur (23) d'aléas de phase pseudo-aléatoire, lesdits moyens (22) de combinaison fournissant un entier (s) compris dans l'intervalle [0, M-1] pour chaque combinaison d'un échantillon codé (Ec) et d'un échantillon (Ea) d'aléa de phase issu dudit générateur (23) d'aléas de phase, M étant supérieur à N ;des moyens (24) de génération de signaux fournissant, pour chaque entier (s) compris dans l'intervalle [0, M-1], une suite (SQ) de q nombres entiers correspondant à cet entier (s), les différentes suites (SQ) étant orthogonales ou quasi-orthogonales entre elles ;des moyens (25) d'émission desdites suites (SQ) de q nombres entiers à l'attention dudit récepteur (31), lesdits moyens (25) d'émission comprenant un modulateur à décalage de phase dont le nombre d'états est égal à M ;ledit récepteur (31) comporte successivement :des moyens de réception (40) restituant lesdites suites (SQr) de q nombres entiers ;des moyens de traitement (45) recevant d'une part lesdites suites (SQr) de q nombres entiers desdits moyens de réception (40) et d'autre part des échantillons (Ea) d'aléas de phase issus d'un générateur (43) d'aléa de phase synchronisé avec ledit générateur (23) d'aléas de phase dudit émetteur (20), lesdits moyens de traitement (45) assurant une démodulation desdites suites (SQr) de q nombres entiers et effectuant une opération inverse de celle desdits moyens (22) de combinaison pour restituer lesdits échantillons codés (di) ;des moyens (44) de décodage restituant ledit signal numérique (SNr) à partir desdits échantillons fournis par lesdits moyens de traitement (45).
- Système selon la revendication 1, caractérisé en ce que lesdites M suites (SQ) de q nombres entiers sont des séquences de Hadamard.
- Système selon l'une des revendications 1 et 2, caractérisé en ce que lesdits moyens (25) d'émission comprennent des moyens (26, 27) d'étalement de spectre par séquence d'étalement (SE) et en ce que lesdits moyens de réception (40) comprennent des moyens de compression de spectre (34) fonctionnant en synchronisme avec lesdits moyens (26, 27) d'étalement de spectre desdits moyens d'émission (25).
- Système selon l'une des revendications 1 à 3, caractérisé en ce que lesdits moyens d'émission (25) comprennent des moyens (29, 30) d'évasion de fréquence aptes à modifier la fréquence porteuse dudit signal transmis audit récepteur (30) et en ce que lesdits moyens de réception (40) comprennent des moyens (32, 33) assurant une fonction inverse de celle desdits moyens (29, 30) d'évasion de fréquence, aptes à supprimer ladite évasion de fréquence introduite audit émetteur (20).
- Système selon l'une des revendications 1 à 4, caractérisé en ce que lesdits moyens de codage (21) effectuent également un entrelacement des bits dudit signal numérique (SN) et en ce que lesdits moyens de décodage (44) effectuent également un désentrelacement des échantillons décodés (di).
- Système selon l'une des revendications 1 à 5, caractérisé en ce que lesdits moyens de combinaison (22) dudit émetteur (20) fournissent, pour chaque échantillon codé (Ec), un entier (s) égal à: où:s est ledit entier fourni par lesdits moyens de combinaison (22);Ec est ledit échantillon codé;Ea est un échantillon d'aléa de phase issu dudit générateur (23) d'aléas de phase dudit émetteur (20);
- Procédé de transmission à étalement de spectre d'un signal numérique entre un émetteur (20) et un récepteur (30), caractérisé en ce qu'il consiste à :au niveau dudit émetteur (20) :générer, pour chaque bloc de k bits dudit signal numérique, un échantillon codé (Ec) prenant une valeur entière comprise dans l'intervalle [0, N-1], chaque valeur entière étant représentative des k bits du bloc correspondant ;combiner lesdits échantillons codés (Ec) avec des échantillons d'aléa de phase (Ea) pour générer un entier (S) compris dans l'intervalle [0, M-1] pour chaque combinaison d'un échantillon codé (Ec) et d'un échantillon d'aléa de phase (Ea), M étant supérieur à N ;générer pour chaque entier (s) compris dans l'intervalle [0, M-1], une suite (SQ) de q nombres entiers correspondante, selon une transformation univoque, les différentes suites (SQ) étant orthogonales ou quasi-orthogonales entre elles ;transmettre lesdites suites (SQ) de q nombres entiers audit récepteur (30) ;au niveau dudit récepteur (30) :reconstituer lesdites suites (SQr) de q nombres entiers à partir du signal reçu dudit émetteur (20) et générer, pour chaque suite (SQr) de q nombres entiers reconstituée, un entier selon une transformation inverse de celle réalisée au niveau dudit émetteur (20) ;combiner chaque entier généré avec un échantillon d'aléa de phase (Ea) identique à celui ayant permis d'obtenir cet entier au niveau dudit émetteur (20), de manière à restituer l'échantillon codé (di) correspondant, ladite combinaison supprimant ainsi ledit aléa de phase (Ea) ;décoder chaque échantillon codé (di) de manière à restituer ledit signal numérique (SNr).
- Procédé selon la revendication 7, caractérisé en ce que lesdites suites (SQ) de q nombres entiers sont des séquences de Hadamard.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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FR9306936 | 1993-06-09 | ||
FR9306936A FR2706704B1 (fr) | 1993-06-09 | 1993-06-09 | Système de transmission numérique à étalement de spectre obtenu par codage pseudo-aléatoire basse fréquence de l'information utile et procédé d'étalement et de compression de spectre utilisé dans un tel système. |
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EP0629059A1 EP0629059A1 (fr) | 1994-12-14 |
EP0629059B1 true EP0629059B1 (fr) | 2001-09-05 |
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EP94401282A Expired - Lifetime EP0629059B1 (fr) | 1993-06-09 | 1994-06-08 | Système de transmission numérique à étalement de spectre obtenu par codage pseudo-aléatoire basse fréquence de l'information utile et procédé d'étalement et de compression de spectre utilisé un tel système |
Country Status (6)
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US (1) | US5546423A (fr) |
EP (1) | EP0629059B1 (fr) |
CA (1) | CA2125444A1 (fr) |
DE (1) | DE69428155D1 (fr) |
ES (1) | ES2162846T3 (fr) |
FR (1) | FR2706704B1 (fr) |
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EP0957604B1 (fr) | 1998-05-15 | 2005-11-30 | Sony Deutschland Gmbh | Emetteur et méthode de transmission augmentant la flexibilité de l'allocation de codes |
KR100318959B1 (ko) * | 1998-07-07 | 2002-04-22 | 윤종용 | 부호분할다중접속통신시스템의서로다른부호간의간섭을제거하는장치및방법 |
RU2200366C2 (ru) * | 1998-07-20 | 2003-03-10 | Самсунг Электроникс Ко., Лтд. | Устройство для генерирования маски квазиортогонального кода в системе мобильной связи |
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US5276705A (en) * | 1993-01-06 | 1994-01-04 | The Boeing Company | CCD demodulator/correlator |
US5341396A (en) * | 1993-03-02 | 1994-08-23 | The Boeing Company | Multi-rate spread system |
US5377226A (en) * | 1993-10-19 | 1994-12-27 | Hughes Aircraft Company | Fractionally-spaced equalizer for a DS-CDMA system |
-
1993
- 1993-06-09 FR FR9306936A patent/FR2706704B1/fr not_active Expired - Lifetime
-
1994
- 1994-06-08 US US08/257,057 patent/US5546423A/en not_active Expired - Fee Related
- 1994-06-08 ES ES94401282T patent/ES2162846T3/es not_active Expired - Lifetime
- 1994-06-08 CA CA002125444A patent/CA2125444A1/fr not_active Abandoned
- 1994-06-08 EP EP94401282A patent/EP0629059B1/fr not_active Expired - Lifetime
- 1994-06-08 DE DE69428155T patent/DE69428155D1/de not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
US5546423A (en) | 1996-08-13 |
FR2706704B1 (fr) | 1995-07-13 |
EP0629059A1 (fr) | 1994-12-14 |
FR2706704A1 (fr) | 1994-12-23 |
DE69428155D1 (de) | 2001-10-11 |
ES2162846T3 (es) | 2002-01-16 |
CA2125444A1 (fr) | 1994-12-10 |
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