Showing papers by "Matra published in 1994"

Total dose effects on negative voltage regulator

Abstract: Functional failure at low dose level (4 Krad(Si)) on voltage regulators (LM137) from different manufacturers are analysed. Dose rate effects on parts hardness are evaluated, showing that lowering the dose rate degrade more the IC's in the range 55 rad(Si)/s-0.8 rad(Si)/s. A failure mechanism is proposed, mainly based on circuit analysis, voltage contrast measurements, local irradiation and local electrical measurements with probe station. A SPICE simulation was performed, providing quantitative informations on the degradation. In the light of such a failure analysis and dose rate effects, practical implications on radiation assurance are discussed. >

Radio transmission method using repeater stations with spectrum reversal

Abstract: The method is used to transmit digital signals by radio over a predefined frequency band between a base station and mobile stations. At least one repeater station is used to receive radio signals transmitted by the base station and to retransmit radio signals to the mobile stations over the same frequency band. The spectrum of the radio signals transmitted by the base station to the repeater station is reversed relative to the spectrum of the radio signals retransmitted by the repeater station to the mobile stations. The invention is particularly applicable to radiotelephone communications networks.

Method for selecting propagation paths retained for receiving messages transmitted by CDMA radiocommunication

Abstract: Each path is identified by a delay which is applied to at least one spreading sequence for determining a correlation between the received signal ans said spreading sequence. For each selected delay, a reception energy, contained in the CDMA signal consisting of a correlation between the received signal and a reference spreading sequence, is estimated. Delays to be tested are randomly chosen with a choice probability having a maximum for a delay substantially equal to the smallest selected delay. The delays thus chosen are tested by estimating the reception energy associated thereto. When the reception energy for a tested delay is greater than at least one of the reception energies associated to the previously selected delays, the tested delay is substituted for the previously selected delay having the smallest reception energy.

The impact analysis task in software maintenance: a model and a case study

Abstract: If better tools are to be developed to support the impact analysis task, greater clarity is needed about the exact nature of that task. This paper presents a definition of impact analysis and distinguishes between impact analysis and program understanding. Impact analysis is a necessarily approximate technique which must focus on the cost-effective minimization of unwanted side-effects. A key to effectiveness would be a way of precisely describing the semantics of each software change. A general model of software impacts is presented that uses flexible declarative propagation rules to describe the way software objects affect each other. Preliminary versions of the model have been implemented in an impact analysis system. A small case study was performed to gain experience in applying the model as part of a software change process. Recommendations are made for impact analysis tool support and for further research directions. >

Semiconductor memory component comprising stacked memory modules

Abstract: A memory component has a rectangular semiconductor substrate containing active memory circuits and output terminals on a major surface thereof An insulating layer on the major surface receives a plurality of metal connection leads, connecting the output terminals to connection pads located on the major surface along only one of longer sides of the substrate A plurality of additional pads are distributed between the connecting pads and are devoid of connection leads A memory module comprising several stacked memory components is also described, which uses the additional pads as relays

A digitally controlled beam former for a spacecraft

Abstract: A digitally controlled beam former for a spacecraft which includes means for periodically calibrating the feed paths of the spacecraft's antenna array by measuring the apparent movement of the centre of a reference signal and a nominal signal and utilising the measured data to compensate for at least the phase drift in the antenna feed paths. The measured data may also be used to compensate for amplitude and phase drift in the antenna feed paths.

Characterization of proton interactions in electronic components

Abstract: The responses of several np and pn diodes to 30, 100, 200 MeV protons were experimentally characterized. The results are compared with calculations using the HETC code. Well matching proton-induced SEU cross-sections are deduced. >

Method of synchronization for code division multiple access radiotelephone communications

Abstract: A synchronization method includes selecting, at a mobile station, at least one periodic pseudorandom sequence (PN) which corresponds to, and is synchronized with, the reference sequence transmitted by a base station on a pilot channel, and received by the mobile station over a propagation path, this operation being carried out regardless of the frequency deviation between the transmitter and the receiver. Various possible sequences are tested by calculating the quantities E[s(t)·s*(t-τ)] and E[s(t)·s*(t)], where E[·] designates the mean value calculated over a predetermined integration time, τ designates a predetermined delay, and s(t)=r(t)·c(t) designates the product of the received base band signal r(t) and the value (c(t)) of the tested sequence, and by calculating the ratio |E[s(t)·s*(t-τ)][|/Es(t)·s*(t)]. The sequence under test is selected if the ratio exceeds a predetermined threshold.

Characterization of single hard errors (SHE) in 1 M-bit SRAMs from single ion

Abstract: A Single Hard Error (SHE) characterization was performed on two types of 1 Mbit SRAMs:MT5C1008 from MICRON and MSM8128 from HITACHI. On both types, test results showed that one single ion is sufficient to create a stuck bit. An orbit SHE rate calculation showed that the probability to have a stuck bit in space on a single 1 Mbit SRAM is rather low. >

Position adjusting device for motor vehicle seats

Abstract: The device comprises at least two parallel rails (12) fixed to the floor of the vehicle and two slides (14) integral with the seat, which can slide on the rails (12) and are equipped with means, which can be deactivated with the aid of a manual control borne by the frame of the seat, for locking the slides in any one of several longitudinal positions. The locking means comprise housings distributed along the rails, these being intended to receive a lock bolt borne by the slides (14) and pushed back towards a position of engagement in one of the housings. The manual control includes a member which can be displaced along the slide from a position of rest in which it leaves the lock bolt free to engage in one of the housings towards a position in which it moves the lock bolt away from the housings.

Transmission method for CDMA radiotelephone communications, and apparatuses for implementing such method

Abstract: A base station constructs CDMA channels, each defined by a respective spreading sequence which modulates information bits to be transmitted for forming a respective channel signal. The different channel signals are combined, and then modulated on a carrier frequency, so as to produce a phase shift keyed radio signal which is transmitted towards mobile stations. Each spreading sequence has only one real component. For producing the radio signal, a relative phase shift is applied between different channel signals.

Removable and adjustable vehicle seat

Abstract: The seat, usable especially in the back rows of public-transport vehicles, includes a seat cushion equipped with front legs (16) and rear legs (20) which are intended to bear on transverse rings (18, 22) carried by the floor and which are equipped with dearmable bolts (26, 32) for fastening onto the rings. The rings (18, 22) are fixed to a moving element mounted so that it can slide in longitudinal slideways (50) fixed to the floor and the moving element contains means (52) for longitudinally retaining this element on the slideways, the said means being releasable through action on control means (56, 60) provided on the seat.

Effects of a refractive atmosphere on interferometric processing

Abstract: An application of synthetic aperture radar (SAR) interferometry is the production of digital elevation models (DEM). Once an interferogram is unwrapped, the altitude of each point on the interferogram is calculated thanks to the two satellite positions. The underlying hypothesis in this derivation is that the propagation of the wave through the atmosphere follows a straight line. In fact, the atmosphere is refractive and the ray is bent. In this paper the authors try to assess the effects of ray bending on DEM generation. At first, they model the wave propagation through a refractive medium and model the interferometric processing. Then, they study the refractive index distribution in both the troposphere and ionosphere. They also study spatial and time fluctuations of the refractive index at scales of interest in interferometry. Finally, they simulate different cases of atmospheric disturbances on an interferogram. They show in which cases a refractive atmosphere creates artifacts on an interferogram. In each case, they determine the order of magnitude of the expected error and its signature on the interferogram. Finally they establish which processing method could minimize the effect of the atmosphere on DEM generation. >

Possibility theory in "Fault mode effect analyses". A satellite fault diagnosis application

Abstract: Matra Marconi Space (MMS) has been developing spacecraft diagnostic support systems for eight years. Keeping in mind the operational constraints of scale and efficiency that guided the design of the first systems, the reasoning paradigms are now refined, in order to improve the solutions. The FMECA, Fault Mode Effects and Criticality Analyses, form a very important category of knowledge compiled during the design phase of a satellite, and used also for diagnosis activities. This paper proposes their extension, allowing a finer representation of the available knowledge, at approximately the same cost, through the introduction of an appropriate representation of uncertainty and incompleteness based on possibility theory. Efficient discriminization techniques exploiting uncertain observations are introduced, and an example illustrates the mechanisms involved in this approach. >

Clock recovery circuit with matched oscillators

Abstract: The circuit comprises a first and a second voltage-controlled oscillator (4, 14) having identical characteristics. The first oscillator (4) is incorporated into a frequency synthesis loop (3) in such a way as to oscillate, in response to a first control voltage (V₁), at a frequency equal to a reference frequency multiplied by a number N. The second voltage-controlled oscillator (14) is incorporated into a phase tracking loop (13) which, when it is activated, locks its oscillation phase relative to that of the received data signal (SD). The second oscillator (14) delivers the recovered clock signal (CLK₂). A comparator (20) determines whether the frequency of the second oscillator (14), divided by N, satisfies the condition of not deviating from the reference frequency by more than a predetermined limit value. The phase tracking loop (13) is activated only when the said condition is satisfied, and the first control voltage (V₁) is fed to the control input of the second oscillator when the said condition is not satisfied.

The SOUT optical intersatellite communication terminal

Abstract: Optical communications links between satellites promise to become an important element of future space infrastructure and are the subject of considerable development in Europe. Major advantages over conventional microwave links are low mass and power and smaller size leading to easier accommodation on the satellite. The Small Optical User Terminal (SOUT) is an optical communications package for interconnecting a low earth orbiting satellite to future optical data relay terminals and is the subject of an ESA development programme led by MMS (UK). The baseline terminal has a data rate of 2 Mbps over the return interorbit link and a mass of around 25 kg. The terminal configuration uses a unique combination of a periscopic coarse pointing assembly, refractive telescope, passive antivibration mount, combined acquisition and tracking sensor, and fibre coupled lasers and receivers. The paper discusses the design aspects for an asymmetric optical link based on the SOUT, covering link budgets, pointing, acquisition, and tracking and communications performance. Key SOUT subsystems are described and the structural and thermal configuration which allows these features to be combined in a compact unit is reported.

Method and apparatus for active damping of vibration

Abstract: For active damping of vibration at a location subjected to a primary vibration field, a vibratory wave is generated by adaptive filtering of a reference signal and interferes with the primary field at the location. The residual amplitude of vibration at the location is measured, and filtering is adapted automatically to cancel the residual amplitude as measured. The reference signal is divided into a plurality of individual reference signals that are sine-shaped each containing only one of the plurality of frequencies at which the primary field presents a significant energy, with each individual signal being subjected to a respective adaptive digital filter, and the vibratory wave is generated from the sum of the individual filtered signals. An apparatus for implementing the method comprises n processing paths or channels, each having an actuator driving a digital filter, fed with a sine-shaped signal at a frequency corresponding to a concentration of vibratory energy to be damped.

Lessons Learned from Formalizing and Implementing a Large Process Model

Abstract: This paper describes the early results of the PROMESSE project conducted for the European Space Agency, which aims at formalizing and implementing ESA software development processes, and more specifically the lessons learned from this experiment. Following the logic of the study, it presents the lessons learned from the formalization task, then those learned from the implementation. It concludes with a presentation of the method which will be applied for the validation of the implementation (at the time this paper is written, validation is still going on).

Combining image analysis and thermal models for infrared scene simulations

Abstract: This paper describes an analysis/synthesis simulation procedure for the generation of realistic infrared images of outdoor scenes. The approach is based on combining synthetic scenes with real images using segmentation algorithms and region analysis. At the analysis stage, the image is segmented into homogeneous regions. Each surface region is then attributed material properties and its orientation is computed. Next, a texture signal is extracted from the original image. At the synthesis stage, thermal models are used to predict surface temperatures and to compute the radiometries of the thermal image. Finally, the extracted texture signal is combined with the synthetic radiometries. Temporal variations of the texture signal are also studied in order to generate the same scene at a different time of day. >

Telescope for infrared or visible imaging.

Abstract: The telescope comprises at least one primary concave mirror (M1) for receiving an incoming image and relay optics for enlarging the image reflected by the primary mirror. The relay optics comprise a secondary mirror (M2) and a tertiary mirror (M3), each having a central aperture (12, 13) and each being positioned coaxially with the primary mirror (M1). The secondary mirror (M2) receives the image reflected by the primary mirror (M1) through the central aperture (13) of the tertiary mirror (M3). The tertiary mirror (M3), positioned close to the focal plane of the primary mirror (M1), receives the image reflected by the secondary mirror (M2) and reflects that image through the central aperture of the secondary mirror (M2).

Root adaptive homomorphic deconvolution schemes for speech recognition in noise

Abstract: In this contribution we address the problem of speech recognition in noise and mismatch (there is mismatch when the conditions of training are different from those of testing). We extend our previously reported work in two directions. First, a comparison of normalisation functions demonstrates that the root-based cepstral representation can still be significantly enhanced by an appropriate reinforcement of the most energetic speech portions, leading to a 10-15% increase in performance on raw data Second, we extend this concept and propose two root-adaptive schemes. Recognition tests demonstrate the noise robustness of the proposed analysis that further improves the results by a significant amount. >

Residual stresses in silicon dioxide thin films prepared by reactive electron beam evaporation

Abstract: In this study, residual stresses and optical properties of SiO2 films prepared by reactive electron gun evaporation have been investigated as a function of process parameters. The purpose of this work was to find process conditions resulting in SiO2 stress free films or in a stress level balancing the high index material stress in a multilayer structure. We have found that stress in SiO2 films becomes more compressive with conditions resulting in denser coatings (such as high substrate temperatures or low gas pressures). Using an in situ measurement technique, stress stabilities of these films were also studied under vacuum or heated environments. These experiences have confirmed the porous structure of evaporated coatings and have underlined the great importance of water in their final state of stress.

Device for cooling a satellite-mounted travelling-wave tube

Abstract: The cooling device for cooling a travelling-wave tube is deigned to be mounted on board a geostationary telecommunications satellite. The collector of the tube is thermally insulated from the remainder of the tube and it is thermally connected to a radiator by means of a link part passing through a north or a south panel of the satellite structure and insulated from the panel.

Earth orbiting satellite having electrical energy storage batteries

Abstract: A three axis stabilized geostationary satellite comprises a structure having walls that face North and South when the satellite is on station and carrying at a storage battery of large capacity. The storage battery is constituted by cells mounted on a chassis having a base plate oriented North-South and mechanically secured to sides that face North and South when the satellite is on station. The sides carry thermal radiators that are thermally connected to each other and to the cells. Typically sides are in alignment with North and South faces of the structure and extend away from the Earth.

Apparatus for driving an electrical load from a principal and an auxiliary power source

Abstract: System for supplying a load (M) with electrical energy from a main source (SP) and from an auxiliary source (UC) consisting of an energy storage and recovery device of the high mass energy capacitor type, in which the auxiliary source (UC) is connected directly to the terminals of the load (M), characterised in that a power electronics interface (IEP), of the switched-mode static converter type, is interposed between the main source (SP) and the auxiliary source (UC), this interface being continuously monitored on the basis of electrical quantities characterising the system status, so as to obtain smoothing of the power supplied by the main source (SP).

Slatted bed base

Abstract: The slatted base has two spaced side rails (1, 2) running substantially lengthwise along the bed with a number of mutually spaced sprung slats (3) running transversely to the side rails, the whole forming a supporting surface for a mattress. The sprung slats are secured to the side rails by elastically deformable supporting bars (4) which are lower than said slats. The side rails are arranged below the sprung slats and the supporting strips and inset in relation to the side edges of the bed base towards the middle. At least one sprung slat and one supporting bar are joined at their facing ends (3a, 4a) by an edging component (6) to a bearing module (7). The supporting bar has an elastically deformable central region (8) between the side rails which is more elastic than its two end regions (9, 10) running from the side rails to the ends of the slats. The supporting bar is supported on the side rails and secured at the support points by clamps (11). The supporting bar can move to a limited extent transversely to the corresponding side rail at each support point, while the directions of movement at the two support points are opposite when the bed base is loaded. The edging component has a pocket-shaped retaining means for each end of the sprung slats and the supporting bar. All the retaining means are arranged side-by-side along the side rails and do not overlap in that direction. The retaining means are frictionally interlinked by a bridging cover in the form of a bearer. The individual slats are retained so as to tip in the edging component. The edging component itself can tip in relation to the supporting bar. The proposed design provides a slatted bed base ensuring above-average sleeping comfort and is aesthetically attractive.

Pluggable electrical connection device

Abstract: A pluggable electrical connection device comprises at least one pin-shaped male element of electrically conductive material and at least one female element. The female element is a metal coil spring having at least four turns sufficiently spaced apart to receive the male element between two mutually adjacent turns. The coil spring may have end portions which are bent to constitute tabs parallel to an axis of said coil spring and soldered to said support. It may also be locked between two elongated holes formed in two opposed sides of a cage and connected to a base circuit fast with said cage by pin.

Microstrip antenna with polarization switching

Abstract: In this article the principle of an elementary printed antenna connected with an active hybrid coupler able to provide right- or left-hand circular polarization is investigated. Dual-gate MESFETs are used as phase shifters, and polarization switching is obtained by changing dc voltage applied to the control gate of each MESFET. Equal-amplitude signals with identical phases can also be provided to generate linear polarization. Design and performance of a square patch with such polarization switching capability in S band is presented. © 1994 John Wiley & Sons, Inc.

Enhancement of hands-free telecommunications

Abstract: Hands-free operation is an important feature of many communication terminals such as telephones and conferencing systems. In general, the quality of speech from a hands-free terminal is degraded by ambient noise and by acoustic echo. This paper presents some of the activities in acoustic echo control of a cec Esprit consortium. A short description is given of a database collected specifically for testing acoustic echo cancellers and of a simple methodology for comparative evaluation of adaptive acoustic echo control methods. Eight methods have been investigated so far. Annotated bibliographies are given for each method and comparative performance results are presented.

Digital PSK-type demodulator having clock recovery before carrier recovery

Abstract: For demodulating a phase-modulated signal having 2M states of a carrier (M being an integer), the signal is converted into two baseband signals in quadrature. For that, they are multiplied by a signal delivered by a local oscillator at a transposed carrier frequency. Then the baseband signals are digitized by sampling at the clock frequency of the modulating signal. The clock of the signal is recovered by adjusting the phase of a local clock, stabilized at a bit frequency. For that, a minimum value of the intersymbol interference is searched. The signal clock is recovered before the carrier is recovered. Devices for implementing the method are also disclosed.