Matra

About: Matra is a based out in . It is known for research contribution in the topics: Signal & Detector. The organization has 1330 authors who have published 1216 publications receiving 17967 citations.

Frequency selective surface devices for separating multiple frequencies

Abstract: A frequency selective surface devise is described The device separates or combines two channels by using two or three spaced layers of resonant elements which may be loops or tripoles and which are coupled and which have interactive effects between layers such that the relatively broad transmission and reflection bands characteristic of resonant elements are modified by reinforcement of multiple reflection between the layers in the manner of a Fabry-Perot etalon effect in order to increase the sharpness of the transition of the transmission and reflection bands and thereby to permit combination or separation of closely spaced channels

System for detecting the presence of a possibly moving object

Abstract: A system for detecting the distance L between two objects A and B, either or both of which may be in motion, comprising approach detector means and proximity detector means operational within overlapping distance ranges; each detector means includes an emitter mounted on a first one of the objects, which radiates a primary signal toward the second object, a responder on the second object, which radiates a similar secondary signal back toward the first object, and a signal comparator for measuring the time differential between the primary and secondary signals to determine the distance L between the objects. A range switch coupled to both comparators develops an output indicative of the distance L within a comprehensive distance range encompassing both the approach range and the proximity range and extending down to zero distance.

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. >

Rotary electric motor having magnetically isolated stator and rotor groups

Abstract: A rotary direct current electric motor in which rotor and stator members are each configured as annular rings, concentric with respect to each other, about an axis of rotation. Either of the rotor or stator members is formed of groups of electromagnet pole pairs, the groups substantially equidistantly distributed along the angular extent of the annular ring, each of the groups comprising magnetic material magnetically isolated and separated from the other groups. The other member includes a plurality of permanent magnet poles substantially equidistantly distributed with alternating magnetic polarity along the angular extent of the radial air gap formed between the members, the permanent magnet poles having a discontinuous magnetic return path, thereby dividing the member into magnetically isolated groups of permanent magnet poles.

Passive and active microvibration control for very high pointing accuracy space systems

Abstract: This paper presents the results of a two-year proof-of-concept program to prepare for the foreseen needs to master microvibrations on-board high pointing accuracy platforms, through the design, prototyping and experimental validation of four microvibration control systems: (1) an elastomer-based passive isolator for six degree-of-freedom isolation of a disturbance source (reaction wheel or mechanical cooler). Attenuation performance exceeding 20 dB above 25 Hz and 40 dB above 50 Hz has been demonstrated. (2) A passive vibration damping system, based on distributed piezoceramic wafers connected to a dissipative electrical circuit. Such simple, standalone devices are shown to have interesting applications (up 20 dB attenuation) when applied to the damping of a local flexible mode with concentrated strain energy. (3) Active damping with two-dimensional smart structures by using positive position feedback on pairs of collocated piezo-electric wafers used as sensors and actuators. Modal damping from 10 to 20 dB on the best controlled modes has been demonstrated, but some less controllable modes remain essentially undamped. (4) A centralized anti-phase control scheme operating on distributed sensors and actuators to compensate for stationary harmonic disturbances. The sensors are accelerometers and the actuators piezoelectric wafers or active struts equipped with a stack of piezoceramic wafers. The harmonic disturbance (for instance a reaction wheel unbalanced force) is estimated and compensated, with demonstrated attenuation from 30 to 40 dB. Follow-on activities in the domain are focused on the development of flight prototypes of the two active control concepts, for validation through on-orbit experimentation.