FR2887337A1 - Mode-stirring reverberation chamber for use in e.g. aeronautic field, has conducting units connected to wall by connecting/disconnecting unit for establishing/breaking electrical connection between conducting unit and wall - Google Patents

Abstract

The chamber has lateral walls (10, 11), a floor (12) and a ceiling covered with conducting units spaced between the units. Each conducting unit (A-G) is connected to a wall or another conducting unit by a connecting/disconnecting unit for establishing or breaking an electrical connection between the conductor unit and the wall and/or the other conducting unit. The conducting units are units having the shape of a plate with a rectangular edge. An independent claim is also included for a method for electromagnetic stirring in a mode-stirring reverberation chamber.

Description

2887337 1

BREWING DEVICE AND METHOD

  ELECTROMAGNETIC IN A REVERBERANTE CHAMBER BREWING MODES.

  The present invention relates to a device and method for electromagnetic stirring in a mode-mixing chamber.

  Electromagnetic waves can disrupt the operation of electrical and electronic equipment, particularly such equipment in motor vehicles. It is therefore important to test electrical and electronic equipment to understand the influence of surrounding electromagnetic waves on their operation. Conversely, it is also very important to determine the electromagnetic energy emitted by these electrical and electronic equipment in their environment. This is the reason why the object of the present invention concerns both the radiation measurement tests (emission) and the so-called immunity tests.

  Such tests are most often performed in anechoic or semi-anechoic chambers, but also in enclosures known as reverberant chambers with intermittent modes (CRBM).

  In the aeronautics and military sectors, the CRBMs make it possible to qualify the immunity of electrical and electronic systems at the level of the on-board equipment or at the plane level as a whole. They also make it possible to determine, as already mentioned above, the electromagnetic energy emitted by these devices in their environment. In the automotive field, CRBMs are only beginning to be used and only for unit tests on single equipment.

  The electrical or electronic equipment to be tested is placed in a reverberation chamber when an antenna placed in the chamber emits an electromagnetic field. It may also be to determine the electromagnetic energy emitted by an electrical or electronic equipment in its environment, in which case said equipment acts as an antenna. Although more particularly described in its immunity application, the present invention applies mutatis mutandis to the emission applications of the equipment tested.

  To return to the immunity application, measurements are then made to apprehend the influence of the electromagnetic field on the equipment under test.

  The reverberant chambers are, in general, provided with an electromagnetic shield forming a Faraday cage, in order to be protected from external electromagnetic nuisances.

  The use of a Faraday cage is required to make accurate measurements in electricity and electronics. With such shielding, the outer waves circulate on the envelope, but can not penetrate.

  In the metallic cavity constituting the CRBM, there is appearance of standing waves associated with the different eigen modes of the cavity. The mixing of these modes can be carried out using a conductive element in rotation or by modulation of the frequency 2887337 3 emitted. This makes it possible to obtain a random distribution of the electromagnetic field in the CRBM and thus to carry out the electromagnetic compatibility tests on the equipment placed inside the chamber.

  The stirring is necessary to modify the electromagnetic field distribution inside the chamber in order to obtain a statistically homogeneous and isotropic electromagnetic field distribution.

  The mechanical stirring means is generally formed of a horizontal or vertical support axis supporting large wings. It is known, for example, according to French Patent No. 2,824,669, an electromagnetic stirring device for a reverberation chamber in the form of a rotating element about a horizontal or vertical axis, said element comprising an elongated hollow body of length substantially equal to the length of the reverberation chamber, provided with a plurality of edges not parallel to each other, separating metal walls non-parallel to each other, with some of these walls being provided with openings.

  Such an electromagnetic stirring device for a mode-shifting reverberation chamber has a large footprint which significantly reduces the useful test area.

  Other mechanical stirring devices are known, such as the stirrer described in US Pat. No. 6,686,818, which discloses a device comprising a plurality of electrically conductive surfaces attached to each other so as to present as a whole a configuration in the form of Z, which configuration has a longitudinal axis, two lateral edges which extend parallel to the longitudinal axis, and two leading edges which extend perpendicularly to the longitudinal axis, first and second planar substrates fixed on each side edge, third and fourth planar substrates attached to each leading edge and attached to the first and second substrates respectively, a shaft coaxial with the longitudinal axis and means for rotating the side shaft. The particular form of this brewer also has a significant footprint.

  In general, the mechanical stirrers have, in addition to the disadvantages due to their bulk in the reverberation chamber, several major disadvantages among which: - the stability period at startup, and especially the stability period 15 at rest during which the brewer continues to move and modify the electromagnetic field, - the mechanical drive which requires a powerful stepper motor at startup as well as at rest, - the need for a position sensor to locate the rotation angle of the stirrer; - the fact that the electromagnetic state for a given position of the stirrer is linked to the electromagnetic state of the preceding position; - the obligation, to go from one electromagnetic state to another, to go through other intermediate states, often undesired, 2887337 5 - a repeatability according to the amounts of mechanical positioning of the stirrer, - the trough rsée of the wall of the chamber by the axis support of rotation of the stirrer, - the fixed arrangement of the blades or only modifiable mechanically.

  The principle of electromagnetic stirring of the reverberant mode-mixing chamber is essentially based on the modification of the boundary conditions of the electromagnetic field in the space of the volume defined by the chamber. Brewing is one of the means to achieve this, but there are others.

  To obviate the aforementioned drawbacks of mechanical stirrers, electromagnetic stirring devices have been implemented without mechanical stirrer. Such a device is described in patent EP 1 141 733, according to which the reverberant chamber, made in the form of a tent, made of conducting material, does not comprise two parallel walls and comprises at least one wall perpendicular to another, and is varied at least a portion of a wall by means of a vibrator operably connected to one of the corner joints of the tent. The distribution of the electromagnetic field is the result of the variation of the geometry of the walls. In this device, there is no conductive element or stirrer in motion inside the chamber, but it is the chamber itself which is in motion by the displacement of at least a part of its walls. Thus, the majority of the disadvantages due to mechanical stirrers are found, with the exception of the space requirement in the interior space.

  It is also known, according to French Patent 2,824,669, an electromagnetic stirring device implemented in a test reverberation chamber which has no mechanical stirrer. According to this patent, the chamber comprises a set of internal conductors called septa, in number at least equal to two. Each septum is composed of at least one elementary conductor, is connected to one or two connectors passing through the wall of the chamber, and defines in the test volume, by its arrangement in the chamber, an electromagnetic coupling with the equipment to be test. At least one septum is arranged so that its electromagnetic coupling plane is distinct and not parallel to the coupling plane of at least one other septum. The electromagnetic coupling plane is defined by the electric coupling vector and the magnetic coupling vector. It is, therefore, a hybrid structure in which the plates act as sources of electromagnetic energy, can be powered individually and thus allow to polarize the electromagnetic field in three dimensions deterministically. In this device, conventional means for producing electromagnetic energy, such as antennas, are not used.

  The object of the present invention is to provide a new mode-switching reverberation chamber without a rotating mechanical device for modifying the boundary conditions of the electromagnetic field, and without modifying the use of various conventional means, such as antennas, of a source of production of the electromagnetic field.

  Another object of the present invention is to provide such a mode-shifting reverberation chamber in which the stirring device offers a very large variety of particular distributions of the electromagnetic field in the test volume of the chamber, and a very large wide variety of longer or shorter test sequences.

  Another object of the invention is to provide an electromagnetic stirring device in a rewire-mode stirring chamber for the implementation of this new method, which has great ease of use, high programmability, and high reliability. .

  To achieve these aims, the mode-switching reverberation chamber according to the present invention consists of a metal cavity having sidewalls, a floor and a ceiling, and a source for producing an electromagnetic field therein of said cavity. In this chamber, at least one wall of the side walls, the floor and the ceiling is covered with at least two conductive elements spaced apart, each conductive element being connected by at least one connection / disconnection means to a wall and or another conductive element, so as to allow to establish or interrupt the electrical connection between said conductive element and said wall and / or the other conductive element.

  According to one embodiment of the invention, at least two side walls are covered with conductive elements, spaced apart from each other, each conductive element being connected by at least one connection / disconnection means to a wall and / or to another element conductive, so as to allow to establish or to interrupt the electrical connection between said conductive element and said wall and / or the other conductive element.

  According to another embodiment, the ceiling is, in addition, covered with conductive elements, spaced apart from each other, each conductive element being connected by at least one connection / disconnection means to a wall and / or to another conductive element, so as to make it possible to establish or interrupt the electrical connection between said conductive element and said wall and / or the other conductive element.

  According to another embodiment, the floor is, moreover, covered with conductive elements, spaced apart from each other, each conductive element being connected by at least one connection / disconnection means to a wall and / or to another conductive element, so as to make it possible to establish or interrupt the electrical connection between said conductive element and said wall and / or the other conductive element.

  According to another embodiment of the invention, one or more conductor element (s) has (s) at least two connection / disconnection means for establishing or interrupting the electrical connection between said conductive element and at least two walls of the chamber.

  According to another embodiment, one or more conductor element (s) has (s) at least two connection / disconnection means for establishing or interrupting the electrical connection between said conductive element and at least two other conductive elements.

  According to yet another embodiment of the invention, one or more conductor element (s) has (s) at least two connection / disconnection means for establishing or interrupting the electrical connection between said conductive element with at least one other conductive element and at least one wall of the chamber, respectively.

  Preferably, each conductive element is mechanically connected to said corresponding wall of the metal cavity by means of a rigid support whose one end is fixed on said corresponding wall and the other end is fixed on the conductive element.

  Preferably, said conductive elements are plate-shaped elements.

  Also preferably, said conductive elements are rectangular shaped plate shaped members.

  As mentioned above, the present invention also applies to radiation measurements emitted by electrical or electronic equipment and, in this case, said source of production of the electromagnetic field inside said cavity is constituted by the equipment to be tested. in operation itself.

  Another object of the present invention is to provide a novel method for electromagnetic stirring in a mode-switching reverberation chamber of the type according to the present invention and mentioned above, in which method a first combination of electrically conductive elements to the cavity of said chamber and / or between them, - then a second combination of conductive elements is connected to said cavity of the chamber and / or between them, the connection being repeated n times with each time a combination different from the previous combination of conductive elements or different connections with the same conductive elements, so as to form a test sequence.

  Other objects, advantages and features of the invention will become apparent from the following description of an exemplary embodiment of the invention, not limiting the scope of the present invention, and accompanied by the appended drawings in which: FIG. 1 is a schematic view of a conventional mode stirring reverberation chamber; FIG. 2 is a diagrammatic view of a mode-switching reverberation chamber according to the present invention.

  In the drawing of Figure 1, there is shown schematically a reverberant chamber 1 for testing equipment 4, here for illustrative purposes a motor vehicle in its entirety. A source of production of an electromagnetic field is represented by an antenna 2. Adjacent to the cavity of the chamber subjected to the magnetic field, there is a control part 5 in which the test equipment, in particular the equipment of the equipment, is assembled. display of measurements.

  2887337 11 The mixing of modes makes use of resonances that appear naturally inside a reverberant chamber by modifying pseudo-randomly their appearance. This is achieved by operating a set of large metal blades 3 in slow rotation, so as to move the resonances inside the cavity 1 of the chamber. The electromagnetic field, on average on a revolution of the stirrer 3, is statistically uniform and isotropic. It saves time because the equipment under test 4 does not need to be rotated, and the polarizations of the field production source do not need to be changed.

  However, for the reasons indicated above, and in particular because of the size of the stirrer 3 and its actuating means, it has been sought to achieve results at least as good without a mechanical stirrer.

  A particular embodiment of a mode-switching reverberation chamber, without a mechanical stirrer, is described with reference to the following figure.

  In the drawing of Figure 2, there is shown a portion of the cavity constituting the reverberant chamber by two adjacent side wall portions 10 and 11, and a floor portion 12. The chamber also has a ceiling not shown.

  By way of example, in order to illustrate the operating principle of the invention, a plurality of conductive elements A-G remote from the walls are arranged on the side walls 10 and 11. The conductive elements are spaced apart. In addition, these conductive elements may be spaced apart from the walls at different distances from one element to another.

  Each conductive element A-G is mechanically connected individually to the corresponding wall by means of a rigid support or several rigid supports.

  Each conductive element A-G is electrically connected individually to the corresponding wall (side wall, floor and / or ceiling) by means of one or more controlled switches, not shown; accordingly, the electrical connection between each conductive element can be individually established or interrupted with one or more corresponding wall (s), therefore with the metal wall of the chamber. In the same way, electrical connections may be provided for connecting the conductive elements together, separately or in combination.

  Depending on the number of conductive element connections made, the boundary conditions of the walls of the chamber will be different. They will be modified by the opening or closing of each switch independently of each other.

  For each combination of switches in open or closed position will correspond a particular distribution of the electromagnetic field in the volume of the cavity or test volume. The complete stirring of the electromagnetic field will therefore consist in going through a more or less long sequence of combinations of switch states, each given combination being different from the combination which precedes but may however be repeated in said sequence.

  If a, b, c, .... g, are the designations of the respective switches of the conductive elements referenced A, B, C, G, in the drawing 2887337 13 of Figure 2, and if we note, so conventional, 0 the open state and 1 the closed state, an example of electromagnetic stirring can be obtained by traversing the following sequence of n or different combinations of states of switches: 1st step: a = 0 b = 0 c = 0 d = 0 e = 0 f = 0 g = 0 2ndnot: a = 1 b = 0 c = 1 d = 0 e = 0 f = 1 g = 0 3not: a = 0 b = 1 c = 1 d = 1 e = 0 f = 0 g = 1 10 ... etc ...

  nthout: a = 1 b = 1 c = 0 d = 0 e = 1 f = 1 g = 0 The number of possible combinations is 2N, where N is the number of switches.

  It goes without saying that the sequence, constituting a certain number of steps, can be freely constructed more or less long, unique or repetitive, determined or random.

  The openings / closures of the switches may be controlled by a program, particularly a computer program, depending on the requirements of the tests and trials.

  In the drawing of Figure 2 which accompanies the above description given by way of non-limiting example of the object of the invention, the conductive elements are flat plates of substantially rectangular or square shape.

  According to another embodiment, the mode-shifted reverberation chamber is identical in all respects to that described above, except that the conductive elements are not plates or are not planar plates.

  It is an important point of the present invention that the conductive elements may be of any shape, of any contour and of any volume without departing from the principle of the invention and without departing from its scope.

  On the other hand, although FIG. 2 illustrates conductive elements on two adjacent side walls for purposes of non-limiting example of the subject of the invention, the conductive elements may be located on any wall of the cavity (side wall, floor and / or ceiling) and any combination of said walls.

  As already mentioned above, each conductive element can be connected / disconnected to one or more wall (s) of the cavity, and can also be connected / disconnected to one or more other conductive element (s).

  In all cases where, according to preferred embodiments of the invention, more than one conductive element connection possibility is provided, said conductive elements may be connected to a plurality of different walls of the chamber cavity.

  When the reverberation chamber 1 is used to test equipment 4, here illustrated by the drawing of a motor vehicle, the source of production of an electromagnetic field may be an antenna 2. When the chamber 1 is used in transmission mode 2887337 to determine the radiation of an electrical or electronic equipment, the source is the equipment to be tested itself.

  The present invention also relates to a new method for electromagnetic stirring in a mode-switching reverberation chamber of type according to that described above with reference to FIG.

  According to this method: - a first combination of conductive elements is electrically connected to the cavity of said chamber and / or between them, then a second combination of conductive elements is connected to said cavity of the chamber and / or between them, the connection being repeated n times with each time a combination of conductive elements different from the above combination, so as to thereby form a test sequence.

  However, a combination may optionally be repeated in the sequence, provided that at least one different combination separates the two repeated combinations.

  The advantages of the present invention stem, in the first place, from the absence of a rotary mechanical stirrer: a gain in test volume inside the chamber, the absence of a mechanical drive system, the absence of a wall passage of any axis of rotation, the absence of a positioning sensor, and the fact that there is no necessary stability time, on which it was necessary to count with the mechanical brewers.

  Secondly, they have the electrical control design of the plates by the individual switches, namely: - state combinations of switches independent of one another, and therefore successive states of the electromagnetic field which can be programmed at will and without limitations, - a faster scanning speed of the combinations, - an excellent positioning repeatability, - longer or shorter sequences depending on the need, - and a programmable modification of the scanning sequence without mechanical intervention, which allows an optimization easier of the brewing device.

  The present invention, in its various variants, and with its unlimited options of shape of the conductive elements, makes it possible to effectively modify the distribution of the current in the structure of the CRBM, namely the cavity itself and the conductive elements, by the modification of the connectivity between the different conductive elements and the walls in order to traverse different paths to the current, thereby modifying the resonance modes present in the volume of the chamber.

Claims (12)

  A mode-shifting reverberation chamber having walls comprising sidewalls (10, 11), a floor (12) and a ceiling, and a source for producing an electromagnetic field (2), said chamber being characterized by at least one wall of the side walls (10, 11), the floor (12) and the ceiling are covered with at least two conductive elements spaced apart, each conductive element (AG) being connected by at least one a connection / disconnection means (ag) to a wall and / or other conductive element, so as to enable the electrical connection between said conductive element and said wall and / or the other conductive element to be established and interrupted; .   2. mode-switching reverberation chamber according to claim 1, characterized in that at least two side walls (10, 11) are covered with at least two conductive elements spaced apart, each conductive element (AG) being connected by at least one connecting / disconnecting means (ag) to a wall and / or other conductive element, so as to make it possible to establish or interrupt the electrical connection between said conductive element and said wall and / or the other conductive element.   3. mode-switching reverberation chamber according to any one of claims 1 and 2, characterized in that the ceiling is covered with conductive elements spaced apart, each conductive element (AG) being connected by at least one means of connection / disconnection to a wall and / or other conductive element, so as to allow to establish or interrupt the electrical connection between said conductive element and said wall and / or the other conductive element.   4. mode-switching reverberation chamber according to any one of claims 1 to 3, characterized in that the floor (12) is covered with conductive elements spaced apart, each conductive element (AG) being connected by at least means for connection / disconnection to a wall and / or to another conductive element, so as to make it possible to establish or interrupt the electrical connection between said conductive element and said wall and / or the other conductive element.   5. mode-switching reverberation chamber according to any one of claims 1 to 4, characterized in that at least one conductive element (AG) has at least two connection / disconnection means for establishing or interrupting the electrical connection between said conductive element and at least two walls of the chamber.   6. mode-switching reverberation chamber according to any one of claims 1 to 4, characterized in that at least one conductive element (AG) has at least two connection / disconnection means for establishing or interrupting the electrical connection between said conductive element and at least two other conductive elements.   7. mode-switching reverberation chamber according to any one of claims 1 to 4, characterized in that at least one conductive element (AG) has at least two connection / disconnection means for establishing or 2887337 19 of interrupting the electrical connection between said conductive element and at least one other conductive element and at least one wall of the chamber, respectively.   8. mode-switching reverberation chamber according to any one of claims 1 to 7, characterized in that each conductive element (AG) is mechanically connected to said corresponding wall of the metal cavity by means of a rigid support having one end is fixed on said corresponding wall and the other end is fixed on the conductive element.   9. mode-switching reverberation chamber according to any one of claims 1 to 8, characterized in that said conductive elements (A-G) are plate-shaped elements.   10. Mode-switching reverberation chamber according to claim 9, characterized in that said conductive elements (A-G) are plate-shaped elements with rectangular contour.   11. Mode-switching reverberation chamber according to any one of claims 1 to 10, characterized in that said production source (2) of an electromagnetic field is constituted by the test equipment (4) in operation itself. even.   12. A method for electromagnetic stirring in a mode-switching reverberation chamber of type according to any one of claims 1 to 11, characterized in that a first combination of conductive elements 2887337 20 is electrically connected to the cavity of said chamber and / or between them, then a second combination of conductive elements is connected to said cavity of the chamber and / or between them, the connection being repeated n times with each time a different combination of the above combination, of thereby to form a test sequence.