NL2006275C2 - Reverberation chamber and method for reverberating electromagnetic radiation in a reverberation chamber. - Google Patents
Reverberation chamber and method for reverberating electromagnetic radiation in a reverberation chamber. Download PDFInfo
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- NL2006275C2 NL2006275C2 NL2006275A NL2006275A NL2006275C2 NL 2006275 C2 NL2006275 C2 NL 2006275C2 NL 2006275 A NL2006275 A NL 2006275A NL 2006275 A NL2006275 A NL 2006275A NL 2006275 C2 NL2006275 C2 NL 2006275C2
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- enclosure
- reverberation chamber
- reflection chamber
- wall
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/08—Measuring electromagnetic field characteristics
- G01R29/0807—Measuring electromagnetic field characteristics characterised by the application
- G01R29/0814—Field measurements related to measuring influence on or from apparatus, components or humans, e.g. in ESD, EMI, EMC, EMP testing, measuring radiation leakage; detecting presence of micro- or radiowave emitters; dosimetry; testing shielding; measurements related to lightning
- G01R29/0821—Field measurements related to measuring influence on or from apparatus, components or humans, e.g. in ESD, EMI, EMC, EMP testing, measuring radiation leakage; detecting presence of micro- or radiowave emitters; dosimetry; testing shielding; measurements related to lightning rooms and test sites therefor, e.g. anechoic chambers, open field sites or TEM cells
- G01R29/0828—TEM-cells
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- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
Description
P30413NL00/MSM
Title: Reverberation chamber and method for reverberating electromagnetic radiation in 5 a reverberation chamber.
The invention relates to a reverberation chamber, comprising an enclosure arranged for containing an electromagnetic field; an electrically conductive structure, said structure being placed inside the enclosure; and, an actuator connected to the structure. The invention 10 further relates to a method for reverberating electromagnetic radiation in a reverberation chamber comprising step a) providing electromagnetic radiation in an enclosure of the reverberation chamber.
EMC (electromagnetic compatibility) testing is concerned with the testing of electronic 15 devices with respect to the emission and susceptibility of electromagnetic energy. An electromagnetic reverberation chamber (also referred to as reverberation chamber or mode-stirred chamber) may provide an environment for such testing.
Inside a reverberation chamber, electromagnetic energy may be provided by an antenna or transmitter. Absorption of the electromagnetic energy is reduced to a minimum by 20 providing electrically conductive walls, turning the chamber into a cavity resonator. It may be necessary to increase the uniformity of the electric and magnetic field strengths inside the working volume of the chamber. One or more stirrers are commonly used for this. An example of a stirrer is a device with large rotating metal reflectors.
The effectiveness of a stirrer or a structure with respect to improving the uniformity of 25 the electrical and magnetic field strengths inside the chamber depends among others on the dimensions of the stirrer and the movement path of the stirrer. In general, increasing the volume the stirrer occupies during its movement along its movement path, increases its effectiveness.
The working volume inside a reverberation chamber, i.e. the volume in which 30 electronic devices to be tested and, optionally, other equipment, such as measurement devices or positioning devices, may be placed, is limited by the total volume of the reverberation chamber and the movement path of the stirrer inside the reverberation chamber. The devices to be tested and the equipment should not be in or near the track of the stirrer.
35 The working volume may be increased by providing a reverberation chamber with a larger total volume. However, reverberation chambers with large volumes are more expensive to produce, require more space at the premises of a user and require more power 2 to achieve the same field levels than reverberation chambers with a smaller volume. A working volume ratio may be defined as the ratio between the working volume of a reverberation chamber divided by the total volume of the (inner space of the) reverberation chamber.
5
It is an objective of the invention to provide a reverberation chamber with an increased working volume ratio. For the reverberation chamber, this objective is achieved in that the actuator is arranged for swinging the structure back and forth about a swing axis.
The enclosure of the reverberation chamber is arranged for reverberating 10 electromagnetic radiation inside the enclosure or for containing an electromagnetic field. The enclosure may then be arranged as a cavity resonator.
The term “swinging” is used here in contrast to the term “rotating”. Swinging of a structure may also be referred to as moving forth and back of the structure about a swing axis, for example between two extreme positions. It may also be referred to as pivoting the 15 structure forth and back about a pivot angle. In contrast, the term “rotating” refers here to rotating about a rotational axis for more than 360 degrees.
The term “structure” may refer to an element of any shape. The structure may be panel and/or may comprise curves. The structure may comprise a bended shape or, for example, a zigzag shape. The structure may comprises a flat panel with a certain thickness. 20 The shape of the structure may be rectangular. In the enclosure of the reverberation chamber, the electrically conductive structure functions as a stirrer.
An effect of swinging the structure back and forth about a swing axis is that the working volume ratio is increased, since the volume that the structure or stirrer occupies when it is swinging around its swing axis, is smaller than the volume that a rotating stirrer 25 occupies. Therefore, more working volume is available in the enclosure for the device to be tested and other equipment, as is explained below.
International standards for testing, such as IEC 61000-4-21, MIL-STD-461F require a certain uniformity of the electrical and magnetic field strengths during testing. At higher wavelengths or lower frequencies of the electromagnetic radiation, this required uniformity is 30 more difficult to obtain. A large stirrer or a large movement may be required. The Lowest Usable Frequency (LUF) of a reverberation chamber is the lowest frequency at which a device may be tested in the enclosure of the reverberation chamber while the requirements for the uniformity of the electrical and magnetic field strengths are met. The LUF of a reverberation chamber is determined by, among others, the dimensions of both the 35 enclosure of the reverberation chamber and the structure or stirrer and the movement path of the stirrer or structure. In an embodiment of the reverberation chamber according to the 3 invention, the reverberation chamber may be arranged for EMC testing with a LUF in a range of 30 MHz - 1 GHz, or preferably in the range of 30-80 MHz.
The working volume may then be further defined as the largest possible box inside the enclosure of the reverberation chamber, wherein the distance between each point in the 5 working volume and the enclosure (or the walls of the enclosure) or the structure is at least 1Λ of the wavelength associated with the Lowest Usable Frequency of the reverberation chamber.
Also according to this further definition of the working space, swinging the structure back and forth about the swing axis has the effect of increasing the working volume.
10 Since the reverberation chamber according to the invention may provide a increased working volume in the same total volume of a reverberation chamber, the working volume ratio is increased.
The possibilities of placing the equipment and the electronic devices to be tested in the enclosure of the reverberation chamber may not be only limited by the working volume, 15 but also by the working ground floor area, since equipment and devices may be placed on the ground floor. The working ground floor area may also be limited by the total volume of the reverberation chamber, the position of the stirrer and the movement path of the stirrer inside the reverberation chamber. Accordingly, an working ground floor ratio may be defined as the ratio between the working ground floor area of a reverberation chamber divided by the total 20 volume of the reverberation chamber. An advantage of the invention may also be that the working ground floor ratio may be increased.
Reverberation chambers are commonly used for performing EMC tests according to international standards, such as IEC 61000-4-21, MIL-STD-461F. These standards require that the testing conditions should be reproducible to a certain extent. This implies that the 25 movements of a stirrer or structure in the reverberation chamber should also be reproducible to a certain extent
In other prior art, stirrers are described that are moved on a rail in a translational direction along a movement path. Because of the inertia of the structure, a translational movement may cause the structure to deform, to twist or to rotate in an uncontrolled manner. 30 This would decrease the reproducibility of the testing performed with a reverberation chamber with such a translational stirrer.
An another effect of the swinging the structure back and forth about a swing axis may be that it is less likely to cause the structure to deform, to twist or to rotate in an uncontrolled manner. In that way, the reproducibility may be improved.
35 In an embodiment of the reverberation chamber according to the invention, the actuator is arranged for swinging the structure about the swing axis through a swing angle, 4 wherein the swing angle is less than 60 degrees, or preferably in a range of 0-20 degrees. The term swing angle may also be referred to as pivot angle in this document.
The advantage of a swing angle in the range of 0-60 degrees, or preferably in a range of 0-20 degrees may be that the volume that the structure or stirrer occupies when it is 5 swinging around its swing axis is especially small when the swing angle in this range. The working volume ratio may thus be further increased.
In an embodiment of the reverberation chamber according to the invention, the structure is moveable in one degree of freedom and fixed in all other degrees of freedom, with respect to the enclosure.
10 By limiting the movements of the structure to one degree of freedom, i.e. to swinging around the swing axis, the movement may be reproducible to a greater extent, since the movement of the structure in other degrees of freedom need not to be controlled.
In an embodiment of the reverberation chamber according to the invention, the structure has a rectangular shape.
15 In an embodiment of the reverberation chamber according to the invention, the swing axis extends horizontally through the enclosure. An advantage of this configuration may be that the structure may swing around the swing axis under the influence of the gravity. The gravity working on the structure may position the structure in a rest position, when the actuator is not exerting a force on the structure. Then, the actuator may simple move the 20 structure out of this rest position and guide the structure swinging back to the rest position under the influence of the gravity.
In an embodiment of the reverberation chamber according to the invention, the swing axis extends parallelly with an edge of the structure and/or coincides with the edge of the structure. In this way, said edge of the structure may remain at one position, while the rest of 25 the structure is moved by the actuator.
In a further embodiment of the reverberation chamber according to the invention, the enclosure comprises a wall and the edge of the structure is swing ably connected to the wall. The term “swingably” may also be referred to as pivot ably.
In this way, the structure or stirrer may be positioned close to a wall of the 30 reverberation chamber and the working volume in the reverberation chamber may be increased. Another advantage may be that the construction of the structure, being connected to a wall of the reverberation chamber, is a relatively simple construction. A complex suspension system may not be needed. Furthermore, this construction may also limit the movement of the structure in one degree of freedom in a simple way.
35 In a further embodiment of the reverberation chamber according to the invention, the wall is a ceiling wall of the enclosure. In this case, the structure of stirrer may simply hang from the ceiling.
5
In an embodiment of the reverberation chamber according to the invention, the reverberation chamber further comprises a transmitter arranged for transmitting electromagnetic radiation with a predefined frequency in the enclosure.
In an embodiment, the structure comprises a main surface, and wherein the swing 5 axis extends parallelly with the main surface. The main surface may be the largest surface of the structure, i.e. it may be the largest surface area of the structure. In a further embodiment, the main surface of the structure faces the transmitter.
In an embodiment of the reverberation chamber according to the invention, the enclosure is arranged for containing an electromagnetic field comprising electromagnetic 10 radiation with the predefined frequency.
In a further embodiment, predefined frequency is in a range of 30 MHz -40GHz, or preferably in a range of 80 MHz - 18 GHz. The Lowest Usable Frequency (LUF) of a reverberation chamber according to an embodiment of the invention may be in the same range as the predefined frequency or may have the same value as the predefined frequency. 15 The LUF of a reverberation chamber according to an embodiment of the invention may be in a range of 30 MHz - 80 MHz or may be 30 MHz or 80 MHz.
The working volume may then be further defined as the largest possible box inside the enclosure of the reverberation chamber, wherein the distance between each point in the working volume and the enclosure (or the walls of the enclosure), the transmitter or the 20 structure is at least 1Λ of the wavelength associated with the predefined frequency or the Lowest Usable Frequency of the reverberation chamber.
The transmitter may be provided as part of the structure or may be arranged on the structure. In that case, also the transmitter is also moved back and forth about the swing axis by the actuator.
25 In an embodiment of the reverberation chamber according to the invention, the structure comprises holes, the holes extending throughout a thickness of the structure. An advantage of the holes in the structure may be that the holes decreases the drag felt by the structure swinging or moving through the air (or other gases) in the reverberation chamber. The drag may influence the required stiffness of the structure, the reproducibility of testing 30 and/or the actuator force that is necessary to move the structure.
In an embodiment of the reverberation chamber according to the invention, the holes have a diameter smaller than 1/4 of a wavelength associated with the predefined frequency.
An advantage of this configuration may be that the holes do not (or to a small extent) 35 let the electromagnetic field pass through. In that case, the electromagnetic radiation may be reflected by the structure, as if the structure had no holes, or as if the structure was a solid wall.
6
In an embodiment of the reverberation chamber according to the invention, the actuator is arranged for swinging the structure about the swing axis between two extreme positions and the enclosure further comprises an other wall, the other wall arranged substantially parallel to the structure being in a position between the two extreme positions, 5 wherein a maximum distance between the structure and the other wall is less than % of a wavelength associated with the predefined frequency.
A distance between the structure and the other wall may be defined as the shortest distance between a point on a side of the structure facing the other wall and a point on a side of the other wall facing the structure. The maximum distance between the structure and the 10 other wall may then be defined as the maximum value of all possible distances between the other wall and the structure swinging about the swing axis.
An advantage of this configuration may be that the structure is located close to the other wall of the enclosure and the volume occupied by the swinging structure is positioned close to the other wall of the enclosure. This may increase the working volume of the 15 reverberation chamber.
In an embodiment of the reverberation chamber according to the invention, the actuator is arranged for swinging the structure about the swing axis between two extreme positions; wherein a cross-section area of the enclosure is defined coplanar with the structure being in a position between the two extreme positions; and, wherein an area of the 20 structure is at least 80% of said cross-section area, preferably in a range of 95-100% of said cross-section area. The position of the structure between the two extreme positions may be any position of the structure between the two extreme positions.
In this embodiment, the area of the structure may (almost) completely fill the cross-section area of the reverberation chamber. In that case, during the swinging of the structure, 25 all edges of the structure may be positioned closely or even touching to walls of the reverberation chamber. In a plane defined by the structure and the swing axis, the shortest distance between an edge of the structure and a wall of the reverberation chamber may be smaller than 1Λ of a wavelength associated with the predefined frequency. Said shortest distance may also be near zero.
30 Furthermore, the location of the transmitter and the structure may define two parts or volumes of the enclosure of the reverberation chamber. The enclosure of the reverberation chamber may be thought as divided in two parts or volumes by the swinging structure. A first part or volume containing the transmitter and a second part or volume that does not contain the transmitter. For an electromagnetic field to extend or travel from the first part or volume to 35 the second part or volume, electromagnetic waves may have to transverse around the structure.
7
When the area of the structure (almost) completely fills the cross-section of the reverberation chamber, the electromagnetic waves will not or hardly transverse around the structure and the electromagnetic field in the second part or volume will be very weak or absent. In that case, all or most electromagnetic energy transmitted by the transmitter into 5 the enclosure may be contained in the first part of volume of the reverberation chamber. When the device to be tested is located in the first part or volume, this may be an energy-efficient configuration: no (or very little) electromagnetic energy may be used or dissipated in the second part or volume of the reverberation chamber, where no devices to be tested are placed.
10 The objective of the invention is further achieved by a method for reverberating electromagnetic radiation in a reverberation chamber, comprising the step of a) providing electromagnetic radiation in an enclosure of the reverberation chamber, characterized in that the method further comprises the step of b) swinging an electrically conductive structure inside the enclosure of the reverberation chamber back and forth about a swing axis.
15 The effects of the method according to the invention may be the same as the effects of the embodiments of the reverberation chamber according to the invention as described above and below. The advantages of these effects may also apply on the embodiments of the method according to the invention. It may also be understood that embodiments of the reverberation chamber according to the invention may also be applicable to embodiments of 20 the method according to the invention.
In an embodiment of the method according to the invention, step b) comprises swinging the electrically conductive structure inside the enclosure of the reverberation chamber back and forth about the swing axis through a swing angle, wherein the swing angle is less than 60 degrees, or preferably in a range of 0-20 degrees.
25 In an embodiment of the method according to the invention, the swing axis coincides with an edge of the structure and the edge of the structure is swingably connected to a wall of the reverberation chamber, preferably to a ceiling wall of the reverberation chamber.
In an embodiment of the method according to the invention, the electromagnetic radiation has a predefined frequency, the predefined frequency being in a range of 30 MHz -30 40 GHz, or preferably in a range of 80 MHz - 18 GHz. The Lowest Usable Frequency (LUF) of a reverberation chamber according to an embodiment of the invention may be in the same range as the predefined frequency or may have the same value as the predefined frequency. The LUF of a reverberation chamber according to an embodiment of the invention may be in a range of 30 MHz - 80 MHz or may be 30 MHz or 80 MHz.
35 In an embodiment of the method according to the invention, step b) comprises swinging the structure about the swing axis between two extreme positions; wherein a cross-section area of the enclosure is defined coplanarwith the structure being in a position 8 between the two extreme positions; and, wherein an area of the structure is at least 80% of said cross-section area, preferably in a range of 95-100% of said cross-section area.
In an embodiment of the method according to the invention, the structure comprises a main surface, and wherein the swing axis extends parallelly with the main surface.
5 The effects and advantages of the above mentioned embodiments of the method according to the invention may be the same as the effects and advantages of embodiments of embodiments of the reverberation chamber according to the invention.
Embodiments of the invention will be described, by way of example only, with 10 reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:
Figure 1 shows a schematic overview of a reverberation chamber according to an embodiment of the invention;
Figure 2a shows a schematic side view of a reverberation chamber according to an 15 embodiment of the invention, for example of a reverberation chamber as shown in figure 1;
Figure 2b shows a schematic top view of a reverberation chamber according to an embodiment of the invention, for example of a reverberation chamber as is shown in figure 1 (left side of figure 2b), and a schematic top view of a reverberation chamber according to prior art (right side of figure 2b); 20 Figure 3 shows a schematic representation of a structure according to an embodiment of the invention; and,
Figure 4 shows another schematic overview of a reverberation chamber according to an embodiment of the invention, for example of a reverberation chamber as is shown in figures 1 and/or 2a.
25
Figure 1 shows a schematic overview of a reverberation chamber 11 according to an embodiment of the invention. The reverberation chamber 11 comprises an enclosure 12, which may have a rectangular shape or any other shape. The walls of the enclosure 12 are usually electrically conductive and they may comprise metals. The enclosure 12 may have a 30 box shape, comprising 6 electrically conductive walls, as is for example shown in figure 1. In an embodiment of the reverberation chamber, the enclosure may have dimensions ranging from 0.5 m to 20 m.
To provide an electromagnetic field in the enclosure 12 the reverberation chamber may be provided with a transmitter 13. The transmitter may be an antenna connected to an 35 electrical power source or it may any other provider of electromagnetic radiation.
In an embodiment, the transmitter is arranged for transmitting electromagnetic radiation with a predefined frequency in the enclosure, the predefined frequency being in a 9 range of 30 MHz - 40 GHz, or preferably in a range of 80 MHz - 18 GHz. The predefined frequency may also be 30 MHz, 80 MHz, 18 GHz or 40 GHz. For the testing of devices, electromagnetic radiation with these frequencies or in these ranges are especially of interest.
Inside the enclosure a device 15 to be tested may be positioned. The device 15 may 5 be a mobile telephone or any other piece of equipment that may be sensitive to electromagnetic waves. The device 15 may be positioned about 1 meter above the ground of the enclosure of the reverberation chamber. A wooden table may provided for positioning the device 15 in the enclosure (not depicted in the figures).
The electromagnetic radiation inside the enclosure 12 of the reverberation chamber 10 may be reflected by the walls. The electromagnetic radiation may then only be dissipated to a small extent in the walls. Because of the reflections of the electromagnetic radiation, which comprises electromagnetic waves, the electromagnetic waves may interfere with each other, turning the reverberation chamber into a cavity resonator. In that case the electrical and magnetic field strengths inside the enclosure may not be uniform. Depending on the 15 frequency of the electromagnetic radiation transmitted by the transmitter 13 and the location of the device 15 in the enclosure 12, the device 15 to be tested may experience a high ora low electrical and magnetic field strength. Since this is undesirable for the testing, the uniformity of the electrical and magnetic field strengths may be improved by the operation of a stirrer or structure inside in the enclosure.
20 Inside the enclosure 12 of the reverberation chamber 11, a structure or a stirrer 14 is placed. The structure may have a rectangular shape and may have length L and a width W. The structure or stirrer 14 comprises electrically conductive material to reflect the electromagnetic waves inside the enclosure 12. The structure may comprise a metal, wherein the weight of the metal may be more than 80% of the weight of the structure, 25 preferably the weight of the metal may be in a range of 90-100 % of the weight of the structure, or may even be 100% of the weight of the structure.
The structure 14 may have a rectangular shape as shown in figure 1, although other shapes are also possible. The structure 14 may have about the same length L and/or width W as one of the walls of the enclosure of the reverberation chamber.
30 In an embodiment of the reverberation chamber 11, structure 14 is moveable in only one degree of freedom, i.e. is able to swing around the swing axis. The structure is fixed in all other degrees of freedom, i.e. the structure 14 cannot be moved in any other translational or rotational direction. In this, all movements are defined with respect to the reverberation chamber.
35 In an embodiment, the edge of the structure 14 is swingably connected to a wall 24 of the enclosure of the reverberation chamber, as for example is shown in figure 2a. The structure 14 may be directly connected to the wall 24 by a hinge or via a connecting element, 10 which may comprise a beam. The swing axis may coincide with the edge of the structure, as for example is shown in figure 2a. The wall 24 to which the structure 14 is connected may be a ceiling wall of the enclosure of the reverberation chamber.
The structure 14 may comprise a main surface 18 (see also figure 3). The main 5 surface may be the surface of the structure with the largest area. In this respect, “largest area” refers to that no other surface of the structure has a larger area.
The swing axis may extend parallelly with the main surface. The structure 14 may have a front surface (18) and may have a back surface (not shown in figure 1), possibly with the same surface area. The front surface of the structure is the surface that faces the 10 transmitter. The main surface 18 may then be further defined as the surface having the largest surface area and facing the transmitter.
During operation, the structure 14 is moving, for example back and forth between two positions along a movement path. According to the invention, an actuator 16 is provided, connected to the structure 14 and arranged for swinging the structure 14 about a swing axis 15 17 forth and back. The movement of the structure 14 will be explained in more detail below with reference to figure 2. In an embodiment of the reverberation chamber, the structure may have dimensions of 0.5 m to 20 m.
A different position of the structure will cause the electromagnetic waves to interference with each other in a different manner. The device 15 to be tested located at a 20 certain position in the enclosure will then experience different electric and magnetic field strengths during operation of the structure, i.e. during the movement of the structure. In this way, the uniformity of the electric and magnetic field strengths is improved, both in space and in time.
In general, the movement of the structure (along the movement path) may be 25 described by the position, the velocity and/or the acceleration of the structure as a function of time. In an embodiment of the reverberation chamber, a velocity-time graph describing the relation between the velocity of the structure and time, may have a sinusoidal shape or a more or less linear or triangular shape.
The effect of the stirrer on the uniformity of the electric and magnetic field strengths 30 may depend on the size and shape of the stirrer and on the movement path of the stirrer inside the enclosure of the reverberation chamber. Usually, a larger size or a larger movement path will increase the effect on the uniformity of the electric and magnetic field strengths, i.e. it will increase the uniformity. However, a larger size or a larger movement path of the stirrer will decrease the working volume in the enclosure of a reverberation 35 chamber.
In figure 2a, a schematic side view of a reverberation chamber is shown according to an embodiment of the invention. Actuator 16 is arranged for swinging the structure 14 about 11 the swing axis 17 through a swing angle β, wherein the swing angle β is less than 60 degrees, or more preferably in a range of 0-20 degrees. The actuator may be arranged for swinging the structure 14 about the swing axis 17 between two extreme positions, indicated in figure 2a by the dotted lines 21 and 22. In that case the swing angle β may be defined by 5 the angle enclosed by the two extreme positions 21 and 22.
For all embodiments of the reverberation chamber according to the invention, it may be the case that the actuator is arranged for swinging the structure 14 forth and back in one period, the period being in the range of 10-25 seconds or preferably about 20 seconds. This means that the structure swings from the first extreme position to the second extreme 10 position back to the first extreme position during this path period.
In the embodiment of figure 2a, the swing axis 17 extends horizontally through the enclosure 12. Preferably, the swing axis extends parallelly to one of the walls of the enclosure of the reverberation chamber, as this may increase the working volume of the reverberation chamber. The structure may simply hang from the ceiling of the enclosure, as 15 is for example shown in figure 2. The gravity may cause the structure to be in a rest position, when the actuator is not exerting a force on the structure. In figure 2a this is indicated by position 25 of the structure. The actuator may be arranged to move the structure out of this rest position 25 to one of the extreme positions 21 or 22. Then, the actuator may be arranged to guide the structure swinging back to the rest position 25 under the influence of the gravity 20 and then to move the structure further to other of the extreme positions 22 or 21. Then, the actuator may be arranged to guide the structure swinging back to the rest position 25 under the influence of the gravity.
In an embodiment of the reverberation chamber according to the invention, the swing axis coincides with a central axis of the structure (not shown in the figures). When the swing 25 axis coincides with a central axis of the structure, the structure may be balanced: i.e. the weight distribution of the structure may be symmetrical, either point symmetrical or line symmetrical. The advantage of a balanced structure may be that it can be constructed using less rigid materials and that it may be moved back and forth by the actuator with a smaller force.
30 The actuator 16 may be a step motor which is for example connected to structure 14 by a rod. The actuator may be connected to an edge of structure 14. This edge may opposite to the edge, with which the swing axis coincides. In another embodiment, the structure 14 may comprise a beam, located at one edge of the structure and to which the actuator 6 is connected. By turning the beam somewhat around its axis, the actuator may move, i.e. swing 35 the structure about the swing axis 17, which coincides with the beam.
The actuator 16 may also be a linear actuator. In general, the actuator 16 may be placed in the enclosure 12 of the reverberation chamber or outside the enclosure 12.
12
The swing angle β may be defined by the angle between the two extreme positions 21 and 22 of the structure or, in other words, by the movement path of the structure 14 from a first extreme position to a second extreme position and vice versa.
In figure 2a, the volume that the stirrer or structure 14 occupies when swinging 5 around swing axis 17 (for example through the swing angle β) has been tightly enclosed by a rectangular box 23. The structure may have a length L and a width W. The volume that the structure 14 occupies when swinging around swing axis 17 (for example through the swing angle β) is smaller than the volume that the structure would occupy when rotating about a rotational axis, that may for example coincide with the swing axis 17. Therefore, the working 10 volume 26 and thus the working volume ratio is increased by the reverberation chamber according the invention.
Moreover, it can be seen from figure 2a, that the volume of such a rectangular box 23 is smaller than the volume of such a rectangular box that tightly encloses a rotating structure. Indeed, the volume associated with a rotating structure with length L and width W would be 15 at least in the order of WL2, while the volume associated with a swinging structure with length L and width W would be at most W-L-2-L-sin(1^) in the case that the swing axis is located at an edge of the structure. When the swing axis is located at a different position, this volume will be less than W-2L2isin(1/^).
It follows that W-2L2-sin(1/^) is less than WL2 if β<60 degrees. When β<20 degrees, 20 the volume of such a rectangular box enclosing the swinging structure according to an embodiment of the invention is even smaller.
However, when a rotating stirrer is provided which is smaller than structure 14, the volume that the stirrer occupies when rotating may be about the same as the volume that the structure 14 occupies when swinging. In that case, the effectiveness of the rotating stirrer 25 may be equal to the effectiveness of the swinging structure 14. The shape of the volume that the structure 14 occupies when swinging may enable the structure to be placed closer to one of the walls of the enclosure than a smaller rotating stirrer. In that way, the working volume of a reverberation chamber with the structure 14 may be larger than the working volume of a reverberation chamber with a rotating stirrer, as is explained below with reference to figure 30 2b.
In figure 2b a schematic top view of a reverberation chamber according to an embodiment of the invention, for example the embodiment of figure 2a, is shown at the left side of figure 2b and a schematic top view of a reverberation chamber according to prior art is shown at right side of figure 2b.
35 As can been seen from the left side of figure 2b, the reverberation chamber according to an embodiment of the invention comprises an enclosure 12, a transmitter 13 and a structure 14. The device 15 to be tested is placed inside working volume 26. The volume that 13 the structure 55 occupies when swinging about the swing axis, as explained above, may be tightly enclosed by rectangular box 23.
In the right side of figure 2b, the reverberation chamber according to the prior art may comprise an enclosure 51, a transmitter 52 and a stirrer 55. Also a device 53 to be tested is 5 shown inside working volume 54. In the prior art, stirrer 55 is a rotating stirrer. The volume that the stirrer 55 occupies when rotating may be tightly enclosed by rectangular box 56.
As can be seen from figure 2b, the working volume 26 is larger than working volume 54, because of the different shape of rectangular boxes 23 and 56 and the way the rectangular boxes 23 and 56 may be positioned in enclosures 12 and 51. Since the total 10 volumes of enclosures 12 and 51 are the same, it can be understood that the working volume ratio is higher in the embodiment in figure 2b according to the invention.
Furthermore, it can also be seen from figure 2b that the working ground floor area in the embodiment of the left side of figure 2b is larger than the working ground floor are in the embodiment of the right side of figure 2b. Thus, since the total volumes of enclosures 12 15 and 51 are the same, it can be understood that the working ground floor ratio is higher in the embodiment of the left side of figure 2b.
Figure 3 shows a schematic representation of structure 14 according to an embodiment of the invention. Structure 14 may be provided with holes 31 that extend throughout a thickness of structure 14. The position and the number of the holes may be 20 adjusted in order to minimize the draft that the air (or any other gas) in the enclosure of the reverberation chamber is exerting on the structure when it is swinging around swing axis 17.
The holes 31 may be provided in different parts of the structure. The further away a part of the structure is arranged from the swing axis, the more draft will be exerted on that part, because it moves faster through the air in the enclosure. Therefore, it may be 25 advantageous to provide the holes 31 in the part of the structure that is located the furthest away from the swing axis. The holes 31 may also be provided as part of a grid or a honeycomb construction. In that case, the structure comprises a grid or a honeycomb construction with holes 31 extending throughout the structure 14.
The holes may have a certain diameter. When the diameter of a hole 31 is large, for 30 example larger than 1/4 of wavelength of the electromagnetic radiation in the enclosure of the reverberation chamber, the electromagnetic radiation may not be completely reflected by the structure 14. Instead, the electromagnetic radiation may travel, at least partly, through the holes. Therefore, according to an embodiment of the invention, the holes 31 have a diameter smaller than Vt of the wavelength associated with the frequency that is transmitted by the 35 transmitter 13, or preferably with the maximum frequency that is transmitted by the transmitter 13. The holes may have a diameter in a range of 4 mm - 8 mm.
14
Figure 4 shows a schematic overview of a reverberation chamber according to an embodiment of the invention. In figure 4, the actuator 16 (not depicted in figure 4) is arranged for swinging the structure about the swing axis 17 between two extreme positions 21 and 22, as is described above. The enclosure may comprise wall 24 and wall 43. Wall 43 is bordering 5 the enclosure of the reverberation chamber and arranged substantially parallel to the structure 14, being in a position between the two extreme positions 21 and 22. In the example of figure 4, the wall 43 is parallel to the structure 14 in rest position 25, for example when the structure 14 is in the middle between the two extreme positions 21 and 22.
According to an embodiment of the invention a maximum distance between the 10 structure 14 and wall 43 is less than 1Λ of the wavelength of the electromagnetic radiation that is transmitted by the transmitter 13. In figure 4, the maximum distance between structure 14 and wall 43 is indicated by w, when the structure 14 is in extreme position 21.
In an embodiment of the invention, a cross-section area of the enclosure may be defined at the location of plane P in figure 4. In this example, the cross-section area is 15 coplanar with the structure 14 in position 25. This cross-section area is indicated by 32 in figure 3. The structure 14 may comprise an area 33, as indicated in figure 3 (this area may include the holes 31). According to an embodiment of the invention, the area 33 of the structure is at least 80% of the cross-section area 32, preferably in a range of 95-100% of said cross-section area 32.
20 In that case, the area 33 of the structure 14 (almost) completely fills the cross-section area 32 of the enclosure, as can also be seen in figure 3. In plane P the distance between an edge of structure 14 and a wall of the enclosure may be small, for example smaller than % of a wavelength associated with the predefined frequency that is transmitted by the transmitter. The distance between an edge of structure 14 and a wall of the enclosure may be close to 25 zero. In that case the edge of structure 14 and the wall of the enclosure may be touching each other when the structure is swinging. For example, in figures 2 and 3 the distance between an edge of the structure 14 and a (floor) wall of the enclosure in plane P is indicated by s.
In figure 4, it can be seen that the enclosure of the reverberation chamber may be 30 thought as divided in two parts or volumes by the position of the swinging structure. A first part 41 or volume containing the transmitter (and maybe the device to be tested and other equipment) and a second part 42 or volume that does not contain the transmitter 13.
When the distances between all edges of structure 14 and the walls of the enclosure of the reverberation chamber in plane P are small or near zero, it may be the case that hardly 35 any electromagnetic energy transmitted by the transmitter in the first part 41 of the enclosure 12 can travel along the edges of structure 14 towards the second part 42. Indeed, it may be the case that all the electromagnetic radiation containing the electromagnetic energy are 15 reflected by the structure 14 back into first part 41 of the enclosure. In this case, the electromagnetic energy will be available in the first part 41, where the device to be tested may be located.
In the above it is also explained how an electromagnetic field in a reverberation 5 chamber may be provided, by the steps of a) providing electromagnetic radiation in an enclosure of the reverberation chamber and step b) swinging an electrically conductive structure inside the enclosure of the reverberation chamber back and forth about a swing axis.
Step b) may comprise swinging the electrically conductive structure inside the 10 enclosure of the reverberation chamber back and forth about the swing axis through a swing angle, wherein the swing angle is less than 60 degrees, or preferably in a range of 0-20 degrees. The swing axis may coincide with an edge of the structure and the edge of the structure is swingably connected to a wall of the reverberation chamber, preferably to a ceiling wall of the reverberation chamber.
15 The electromagnetic radiation may have a predefined frequency, the predefined frequency being in a range of 30 MHz - 40 GHz, or preferably in a range of 80 MHz - 18 GHz. The Lowest Usable Frequency (LUF) of the reverberation chamber may be in the same range as the predefined frequency or may have the same value as the predefined frequency. More particularly, the LUF of a reverberation chamber may in a range of 30 MHz - 80 MHz 20 or may be 30 MHz or 80 MHz.
It is also explained that step b) may comprise swinging the structure about the swing axis between two extreme positions; wherein a cross-section area of the enclosure is defined coplanarwith the structure being in a position between the two extreme positions; and, wherein an area of the structure is at least 80% of said cross-section area, preferably in a 25 range of 95-100% of said cross-section area.
Futhermore, the structure may comprise a main surface, and wherein the swing axis extends parallelly with the main surface.
In all of the embodiments described above, it may be the case that device to be tested 15 is transmits electromagnetic radiation, preferably with the predefined 30 frequency, and that an antenna may be provided to receive electromagnetic radiation in the enclosure of the reverberation chamber. Providing the transmitter 13 is in that case not required. In this way, characteristics of the device to be tested with respect to transmitting electromagnetic radiation may be determined.
Embodiments of the invention may further be described by the following clauses: 35 1] Reverberation chamber, comprising an enclosure arranged for containing an electromagnetic field; an electrically conductive structure, said structure being placed inside the enclosure; and, 16 an actuator connected to the structure, characterized in that the actuator is arranged for swinging the structure back and forth about a swing axis.
2] Reverberation chamber according to clause 1, wherein the actuator is arranged for 5 swinging the structure back and forth about the swing axis through a swing angle, wherein the swing angle is less than 60 degrees, or preferably in a range of 0-20 degrees.
3] Reverberation chamber according to clause 1 or 2, wherein with respect to the enclosure, the structure is moveable in one degree of freedom and fixed in all other degrees of freedom.
4] Reverberation chamber according any of clause 1-3, wherein the structure has a 10 rectangular shape.
5] Reverberation chamber according any of clause 1-4, wherein the swing axis extends horizontally through the enclosure.
6] Reverberation chamber according to any of clauses 1-5, wherein the swing axis extends parallelly with an edge of the structure.
15 7] Reverberation chamber according to any of clauses 1 -6, wherein the swing axis coincides with the edge of the structure.
8] Reverberation chamber according to 7, wherein the enclosure comprises a wall and the edge of the structure is swingably connected to the wall.
9] Reverberation chamber according to clause 8, wherein the wall is a ceiling wall of the 20 enclosure.
10] Reverberation chamber according to any of clauses 1-9, wherein the structure comprises holes, the holes extending throughout a thickness of the structure.
11] Reverberation chamber according to any of clauses 1-10, further comprising a transmitter arranged for transmitting electromagnetic radiation with a predefined frequency in the 25 enclosure.
12] Reverberation chamber according to any of clauses 1-11, wherein the structure comprises a main surface, and wherein the swing axis extends parallelly with the main surface.
13] Reverberation chamber according to clauses 11 and 12, wherein the main surface of the 30 structure faces the transmitter.
14] Reverberation chamber according to any of clauses 1-13, wherein the enclosure is arranged for containing an electromagnetic field comprising electromagnetic radiation with the predefined frequency.
15] Reverberation chamber according to any of clauses 11-14, wherein the predefined 35 frequency is in a range of 30 MHz - 40 GHz, or preferably in a range of 80 MHz - 18 GHz.
17 16] Reverberation chamber according to clause 10 and any of clauses 11-15, wherein the holes have a diameter smaller than 1/4 of a wavelength associated with the predefined frequency.
17] Reverberation chamber according to any of clauses 11-16, 5 wherein the actuator is arranged for swinging the structure about the swing axis between two extreme positions; wherein the enclosure comprises an other wall, the other wall arranged substantially parallel to the structure being in a position between the two extreme positions; and, wherein a maximum distance between the structure and the other wall is less than % of a 10 wavelength associated with the predefined frequency.
18] Reverberation chamber according to any of clauses 11-17, wherein the actuator is arranged for swinging the structure about the swing axis between two extreme positions; wherein a cross-section area of the enclosure is defined coplanarwith the structure being in 15 a position between the two extreme positions; and, wherein an area of the structure is at least 80% of said cross-section area, preferably in a range of 95-100% of said cross-section area.
19] Method for reverberating electromagnetic radiation in a reverberation chamber, comprising the step of a) providing electromagnetic radiation in an enclosure of the 20 reverberation chamber, characterized in that the method further comprises the step of b) swinging an electrically conductive structure inside the enclosure of the reverberation chamber back and forth about a swing axis.
20] Method according to clause 19, wherein step b) comprises swinging the electrically 25 conductive structure inside the enclosure of the reverberation chamber back and forth about the swing axis through a swing angle, wherein the swing angle is less than 60 degrees, or preferably in a range of 0-20 degrees.
21] Method according to clause 19 or 20, wherein the swing axis coincides with an edge of the structure and the edge of the structure is swingably connected to a wall of the 30 reverberation chamber, preferably to a ceiling wall of the reverberation chamber.
22] Method according to one of clauses 19-21, wherein the electromagnetic radiation has a predefined frequency, the predefined frequency being in a range of 30 MHz - 40 GHz, or preferably in a range of 80 MHz - 18 GHz.
23] Method according to one of clauses 19-22, wherein step b) comprises swinging the 35 structure about the swing axis between two extreme positions; wherein a cross-section area of the enclosure is defined coplanar with the structure being in a position between the two extreme positions; and, wherein an area of the structure is at 18 least 80% of said cross-section area, preferably in a range of 95-100% of said cross-section area.
24] Method according to any of clauses 19-23, wherein the structure comprises a main surface, and wherein the swing axis extends parallelly with the main surface.
5 It is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Furthermore, 10 the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the invention. Elements of the above mentioned embodiments may be combined to form other embodiments.
The terms "a" or "an", as used herein, are defined as one or more than one. The term another, as used herein, is defined as at least a second or more. The terms including and/or 15 having, as used herein, are defined as comprising (i.e., not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The scope of the invention is only limited by the following claims.
Claims (24)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL2006275A NL2006275C2 (en) | 2011-02-22 | 2011-02-22 | Reverberation chamber and method for reverberating electromagnetic radiation in a reverberation chamber. |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL2006275 | 2011-02-22 | ||
| NL2006275A NL2006275C2 (en) | 2011-02-22 | 2011-02-22 | Reverberation chamber and method for reverberating electromagnetic radiation in a reverberation chamber. |
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| NL2006275C2 true NL2006275C2 (en) | 2012-08-24 |
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| NL2006275A NL2006275C2 (en) | 2011-02-22 | 2011-02-22 | Reverberation chamber and method for reverberating electromagnetic radiation in a reverberation chamber. |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102015118458A1 (en) | 2015-10-29 | 2017-05-04 | Hamburg Innovation Gmbh | Test chamber for testing the electromagnetic compatibility of an object arranged in the chamber |
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