Patent Grant
7924226
This is a 371 national phase application of PCT/EP2005/054297, filed Sep. 1, 2005.
The present invention relates to a tunable antenna.
Tunable antennae are desirable in order to have multiple operating frequencies, impedances, bandwidths or efficiencies available with one antenna only or to be able to compensate undesired frequency shifts, impedance shifts, bandwidth shifts or efficiency shifts or combinations of those effects.
One of the challenges of small SMD antenna devices is to provide a standard, low cost component that can be used throughout a wide range of products with many different form factors. Usually, the resonant frequency of the antenna changes with the interaction of the surrounding components (e.g., the ground of the PCB, the plastic covers, etc.)
This frequency change may render the device useless, since in communication systems the operating frequencies or at least ranges thereof are well defined and have to be maintained. It is therefore desirable to be able to compensate for such changes of the resonant frequency in order to maintain a particular resonant frequency or frequency band. In particular for the mass production of wireless devices, it is desirable to have one antenna type, that may be used for different wireless devices or may be used in one wireless device for different operating frequencies.
There is a trend in the semiconductor industry towards the so-called System on Chip (SoC) and System in Package (SiP) concepts. The full integration of systems or subsystems into a single chip (Fully Wireless System in Package/on Chip, FWSiP/FWSoC) provides many advantages in terms of cost, size, weight, power consumption, performance, modularity and product design complexity. Several electronic devices for consumer applications, such as handsets, wireless devices (headsets, dongles, computer interfaces, computer mouse, keyboards, remote controls), personal digital assistants (PDAs) or personal computers (PCs) include more and more of these SiP/SoC components. The introduction of wireless capabilities in many other devices such as digital cameras, MP3 players, portable DVD/CD players, smoke detectors, switches, sensors (such as for instance motion, pressure, temperature, medical sensors and meters) and alarms will be made easier through such compact, integrated SiP/SoC devices.
It is therefore an object of the present invention to provide an improved antenna, an improved SMD component, an improved IC-package, an improved wireless device and an improved method of contacting an antenna.
This problem is solved for instance by the antenna of claim 1, the SMD component of claim 21 or 22, the IC package of claim 42, the wireless device of claim 62, the wireless device of claim 74, the wireless device of claim 86 or the method of claim 100. Preferred embodiments are disclosed in the dependent claims.
The antenna comprises a conducting trace, which may be contacted by two or more feeding points. Depending on the contacted feeding point or the combination of contacted feeding points, the resonant frequency, the impedance, the bandwidth or the efficiency of the antenna is different. Thereby it is possible to tune the antenna by the way the antenna is contacted.
In accordance with the teachings described herein, systems and methods are provided for an antenna having multiple feed points that may be used to adjust characteristics of the antenna such as resonant frequency, impedance, bandwidth, and efficiency. The antenna may, for example, be integrated in a surface mount component (SMD/SMT) to be mounted on a ground plane or (printed) circuit board (PCB). (The terms SMD component (surface mount device component) and SMT component (surface mount technology component) both refer to the same and are used equally to describe components which may be surface mount). The antenna may, for example, be printed directly on the PCB of an electronic circuit or wireless device. In addition, the antenna may, for example, be embedded in an integrated circuit package or module that includes other parts of a wireless or radio frequency system.
The antenna described herein may, for example, be used in a wide range of wireless products with many different form factors, such as cellular and handheld telephones (handsets), wireless multimedia terminals, PDAs, portable music players (e.g., MP3 players, CD players, portable analog and digital radios), digital cameras, USB dongles, wireless headsets and earphones, hands-free kits, electronic games, remote controls, light switches, alarms and sensors for home-RF and automotive applications. In addition, the antenna described herein may be used for wireless connectivity applications, including systems for communicating in various frequency bands, such as 2.4 GHz, Bluetooth, 2.4 GHz, IEEE 802.11b/g, 5 GHz, IEEE 802.11a, ZigBee, GPS, Galileo, GSM-900, DCS-1800, UMTS, CDMA, DAB, or other bands. The antenna described herein may, for example, also be used in several geographical domains where the spectrum allocation for radio services are different (e.g., the antenna may cover the 860 MHz ZigBee European band or the 915 MHz ZigBee US band.) It should be understood, however, that other applications are also possible. The shape of the conducting trace is predetermined by the antenna structure. Thereby the antenna properties are mainly predetermined by the given shape.
In many cases, the ultimate component to achieve the true integration of a FWSiP/FWSoC component is the antenna. The concept of integrating a miniature antenna into a package or module is especially attractive due to the tremendous growth and success of cellular and wireless systems. In particular, there is a new generation of short/medium range wireless connectivity applications such as Bluetooth™, Hyperlan, IEEE802.11 (WiFi), ultra wide band (UWB), Wimax and ZigBee systems where the progressive system integration into a single, compact product is becoming a key success factor.
One of the challenges of FWSiP/FWSoC devices is to provide a standard solution that can be used throughout a wide range of products with many different form factors. Usually, the resonant frequency of the antenna changes with the interaction of the surrounding components (mainly the size and shape of the ground plane of the PCB, position on the PCB on which it is mounted, the ground plane clearance, the presence of plastic covers, and so on). The technology described herein presents ways to overcome this problem by providing an IC package with an integrated antenna that can be configured to perform well in many different environments.
The technology described herein provides a miniature antenna integrated into an IC package or module. The IC package or module may, for example, be used as a connectivity solution in several wireless connectivity applications. For instance, the IC package or module described herein may include an antenna that operates in the following systems and frequency bands: 2.4 GHz—Bluetooth™, 2.4 GHz—IEEE 802.11b/g, 5 GHz—IEEE 802.11a, ZigBee, GPS, Galileo, GSM-900, DCS-1800, UMTS, CDMA, PCS1900, KPCS, WCDMA and DAB bands.
In addition, the configurability and/or tunability of the antenna integrated in the IC package may provide a single FWSiP/FWSoC solution that can be used in several geographical domains where the spectrum allocation for radio services are different. For instance, in one example the antenna can be tuned to cover the European band or US band of ZigBee (860 MHz and 915 MHz respectively), while in another example the same AiP (Antenna in Package) module can cover either the 2.4-2.483 GHz band or the 2.471-2.497 GHz band, corresponding to the US/European and Japanese standards of Bluetooth™ respectively.
In a preferred embodiment at the feeding point, means for electrically contacting the conducting trace are provided in order to facilitate the antenna mounting. The means for electrically contacting the conducting trace may be anything that distinguishes from the trace itself and allows for contacting the trace.
In a preferred embodiment the trace may be comprised of a rigid piece and/or may be held by a rigid backing. Different materials for the rigid piece or rigid, stiff or solid backing are possible, as disclosed in the description or the claims. The rigid piece may be a stamped or punched piece of metal that maintains its shape already only due its own stiffness.
In a preferred embodiment, the antenna is provided directly on a circuit board, e.g. by printing or by etching from a conductive layer, or by a thick film process, or a thin film process. The advantage of the antenna being provided directly on the circuit board is the improved fabrication process, since the antenna may be prepared together with other circuitry.
The antenna may have one, two, three or more radiating arms. While only one radiating arm has the advantage of the possibility to use the given space with one single lengthy trace, the provision of more radiating arms offers the advantage to have more freedom in the antenna design, since the antenna geometry can be used to define, e.g., the resonant frequency, impedance, bandwidth and efficiency.
The trace may be continuous or discontinuous. Should the trace be discontinuous, the parts of the trace at the discontinuity may be not directly coupled by contact, but electromagnetically coupled by electromagnetic fields. The option of a discontinuous antenna allows for further design parameters in antenna design.
The conducting trace may comprise several separated parts or blocks. Each of those parts or blocks may have at least one, two, three or more feeding points. This allows for a very flexible system, where antenna properties can be varied to a great extend. It is for example possible to only contact one or the other of said separated parts. Since each separated part may have different antenna properties this allows for an appropriate selection. Further it is possible to connect two, three or more separated parts together allowing for all kind of antenna configurations such as a monopole, a dipole, an antenna with multiple radiation arms, etc. The length of the different arms can be selected by the choice of one or the other separated part or by connecting two or more parts together. Some or all of the separated parts may be different. The different parts may be connected together by e.g. an external by-pass or an external circuit, a switch, a switchable transistor or resistor, a filter, a matching network, an inductive, capacitive or generally passive network or by an active network or anything suitable. This allows for further antenna design options. For the connection of two separated parts also more than one of the above mentioned ways may be available. Two parts may e.g. be connected by a switch or by a network depending on the users selection.
A further possibility for designing the antenna properties is to couple the trace to another antenna structure, such as e.g. a polygonal or multilevel surface. Such surfaces may be coupled by direct contact or by electromagnetic coupling. This other antenna structure is preferably conducting or dielectric.
In a preferred embodiment the trace, or at least part of the trace, is covered by an insulator. This facilitates handling and mounting of the antenna, protects the conducting trace and further prevents the conducting trace from changing its electric properties due to protection of the conducting trace from environmental influences such as humidity, or aggressive gases. Further, by covering the trace, or at least part of the trace with an insulator, the surrounding of the antenna very close to the antenna is electromagnetically provided in a well-defined way, such that the electromagnetic properties of the antenna do not change so easily by providing the antenna in different environments. Further the insulator defines openings to the feeding points which may be e.g. configured for soldering in order to define the soldered areas. Different materials as disclosed in the description or in the claims may be used for the insulator.
At the feeding points the trace is preferably uncovered. This allows for easy contacting of the trace at the feeding points. The feeding points may alternatively also be covered by an easily removable cover such as a foil or the like. This cover may also cover part of the insulator. A single cover may be used for different feeding points. The cover offers the advantage of protecting the feeding points up to, e.g., mounting the antenna.
The antenna may be provided together with an integrated circuit. This integrated circuit may be adapted to feed the antenna and/or to contact the antenna or to connect separated parts of the antenna. The integrated circuit may provide other functions such as data processing for data transmission or data reception according to one, two or more specific data communication system.
The antenna may be provided in the conductive layer of a circuit board, wherein this conductive layer is also used to provide the contacts to the integrated circuit. The antenna may also be provided as an item which is mounted to a circuit board on which also the integrated circuit is mounted. The antenna and the integrated circuit may be provided on the same side of a circuit board or substrate or on opposite sides. Here via holes may be provided e.g. to connect the antenna and the integrated circuit.
The integrated circuit and the conducting trace may be connected in various ways such as by at least an external connection, an internal connection, a circuit board trace, an electrical circuit, a capacitive device, an inductive device, a switch, a transistor, a wire bond and a (switchable) resistor. These and other options allow for a great flexibility when combing the integrated circuit and the antenna.
In some cases it may be advantageous to have the integrated circuit well separated from (but preferably still within one and the same package as) the antenna, since the antenna radiation may be absorbed by the integrated circuit and/or may disturb the circuits functioning. In this case the conducting trace is preferably not covered by said integrated circuit. In order to reduce the size it may, however, be advantageous or necessary to partially cover the conducting trace with the integrated circuit.
It is of particular advantage if the integrated circuit covers at least some or all of the feeding points of the conducting trace. Thereby it is possible to mount the integrated circuit directly on the feeding points, e.g. by soldering. The electrical connection between the antenna and the integrated circuit is thereby achieved in a relatively easy way. Due to the above mentioned radiation absorption it is further of advantage if the integrated circuit only covers the feeding points or at most the antenna portions next to the feeding points but does not cover the major part of the conducting trace.
For a proper functioning of the antenna, a proper connection of the antenna, and well defined electrical properties of such connection, may be important due to the electrical matching requirements. Here it may be advantageous to contact some or all of the feeding points at the fabrication of the antenna such that the connection is well defined. Here also after the connection tests may be performed to check for the properties of the connection. In order to select the appropriate feeding point one or more of the connections may be removed e.g. by scratching, drilling, laser ablation or the like depending on the type of connection. An antenna with small feeding points may e.g. be provided with wire bonds which connect the small feeding points to larger solder pads, pins or to contacts to an integrated circuit. Those wire bonds may be removed such that only the desired connections remain. Also by removal of a conducting trace on a circuit board by scratching, drilling or laser ablation only the desired connections may be maintained. Those connections, however, have well defined properties and therefore may not depend on the particular and unknown connection process performed by a user.
The curve defined by the conducting trace, may have a complex geometry. Possible geometries include the geometry of a space-filling curve, of a grid-dimension curve, of a box-counting curve, and of a contour-curve or the shape of a multilevel structure.
Those different geometries do not exclude each other. This means that, e.g., a space-filling curve may at the same time be a grid-dimension, a box counting, and a contour-curve, and all other ways around. Also multilevel structures and the other geometries do not exclude each other.
The complex geometry allows e.g. for multiple operating frequencies of one antenna only (even without use of the different feeding points, i.e. additional to the possibility given by the different feeding points) and further allows for a small antenna.
In a preferred embodiment the maximum extension of the conducting trace (determined by the diameter of the smallest sphere completely enclosing the conducting trace) is less than ⅕ or 1/7 or 1/10 or 1/15 or 1/20 of the free space wavelength of the resonant (operating) frequency.
This criteria can also be used to define the terms space-filling curve, box-counting curve, grid dimension curve or contour curve. This means, that any curve with a maximum extension less than ⅕ or 1/7 or 1/10 or 1/15 or 1/20 of the free space wavelength of the resonant (operating) frequency can be said to be a space filling curve, a box counting curve, a grid dimension curve or a contour curve.
The different geometries are discussed in the following.
Space Filling Curves
In one example, the antenna or one or more of the antenna elements or antenna parts may be miniaturized by shaping at least a portion of the conducting trace (e.g., a part of the arms of a dipole, the perimeter of the patch of a patch antenna, the slot in a slot antenna, the loop perimeter in a loop antenna, or other portions of the antenna) as a space-filling curve (SFC). Examples of space filling curves are shown in
A space-filling curve can be fitted over a flat or curved surface, and due to the angles between segments, the physical length of the curve is larger than that of any straight line that can be fitted in the same area (surface) as the space-filling curve. Additionally, to shape the structure of a miniature antenna, the segments of the SFCs should be shorter than at least one fifth of the free-space operating wavelength, and possibly shorter than one tenth of the free-space operating wavelength. The space-filling curve should include at least five segments in order to provide some antenna size reduction, however a larger number of segments may be used. In general, the larger the number of segments and the narrower the angles between them, the smaller the size of the final antenna.
A SFC may also be defined as a non-periodic curve including a number of connected straight or essentially straight segments smaller than a fraction of the operating free-space wave length, where the segments are arranged in such a way that no adjacent and connected segments form another longer straight segment and wherein none of said segments intersect each other.
In one example, an antenna geometry forming a space-filling curve may include at least five segments, each of the at least five segments forming an angle with each adjacent segment in the curve, at least three of the segments being shorter than one-tenth of the longest free-space operating wavelength of the antenna. Preferably each angle between adjacent segments is less than 180° and at least two of the angles between adjacent sections are less than 115°, and at least two of the angles are not equal. The example curve fits inside a rectangular area, the longest side of the rectangular area being shorter than one-fifth of the longest free-space operating wavelength of the antenna. Some space-filling curves might approach a self-similar or self-affine curve, while some others would rather become dissimilar, that is, not displaying self-similarity or self-affinity at all (see for instance 1510, 1511, 1512).
Box-Counting Curves
In another example, the antenna or one or more of the antenna elements or antenna parts may be miniaturized by shaping at least a portion of the conducting trace to have a selected box-counting dimension. For a given geometry lying on a surface, the box-counting dimension is computed as follows. First, a grid with rectangular or substantially squared identical boxes of size L1 is placed over the geometry, such that the grid completely covers the geometry, that is, no part of the curve is out of the grid. The number of boxes N1 that include at least a point of the geometry are then counted. Second, a grid with boxes of size L2 (L2 being smaller than L1) is also placed over the geometry, such that the grid completely covers the geometry, and the number of boxes N2 that include at least a point of the geometry are counted. The box-counting dimension D is then computed as:
D=−log(N2)−log(N1)/log(L2)−log(L1)
For the purposes of this document, the box-counting dimension may be computed by placing the first and second grids inside a minimum rectangular area enclosing the conducting trace of the antenna and applying the above algorithm. The first grid in general has n×n boxes and the second grid has 2n×2n boxes matching the first grid. The first grid should be chosen such that the rectangular area is meshed in an array of at least 5×5 boxes or cells, and the second grid should be chosen such that L2=½ L1 and such that the second grid includes at least 10×10 boxes. The minimum rectangular area is an area in which there is not an entire row or column on the perimeter of the grid that does not contain any piece of the curve. Further the minimum rectangular area preferably refers to the smallest possible rectangle that completely encloses the curve or the relevant portion thereof.
An example of how the relevant grid can be determined is shown in
Alternatively the grid may be constructed such that the longer side (see left edge of rectangle in
If the value of D calculated by a first n×n grid of identical rectangular boxes (
Alternatively a curve may be considered as a box counting curve if there exists no first n×n grid of identical square or identical rectangular boxes and a second 2n×2n grid of identical square or identical rectangular boxes where the value of D is smaller than 1.1, 1.2, 1.25, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, or 2.9.
In any case, the value of n for the first grid should not be more than 5, 7, 10, 15, 20, 25, 30, 40 or 50.
The desired box-counting dimension for the curve may be selected to achieve a desired amount of miniaturization. The box-counting dimension should be larger than 1.1 in order to achieve some antenna size reduction. If a larger degree of miniaturization is desired, then a larger box-counting dimension may be selected, such as a box-counting dimension ranging from 1.5 to 2 for surface structures, while ranging up to 3 for volumetric geometries. For the purposes of this patent document, curves in which at least a portion of the geometry of the curve or the entire curve has a box-counting dimension larger than 1.1 may be referred to as box-counting curves.
For very small antennas, for example antennas that fit within a rectangle having a maximum size equal to one-twentieth the longest free-space operating wavelength of the antenna, the box-counting dimension may be computed using a finer grid. In such a case, the first grid may include a mesh of 10×10 equal cells, and the second grid may include a mesh of 20×20 equal cells. The grid-dimension (D) may then be calculated using the above equation.
In general, for a given resonant frequency of the antenna, the larger the box-counting dimension, the higher the degree of miniaturization that will be achieved by the antenna.
One way to enhance the miniaturization capabilities of the antenna (that is, reducing size while maximizing bandwidth, efficiency and gain) is to arrange the several segments of the curve of the antenna pattern in such a way that the curve intersects at least one point of at least 14 boxes of the first grid with 5×5 boxes or cells enclosing the curve. If a higher degree of miniaturization is desired, then the curve may be arranged to cross at least one of the boxes twice within the 5×5 grid, that is, the curve may include two non-adjacent portions inside at least one of the cells or boxes of the grid. The relevant grid here may be any of the above mentioned constructed grids or may be any grid. That means if any 5×5 grid exists with the curve crossing at least 14 boxes or crossing one or more boxes twice the curve may be said to be a box counting curve.
a illustrates an example of how the box-counting dimension of a curve 1 is calculated. The example curve 1 is placed under a 5×5 grid 2 (
The terms explained above can be also applied to curves that extend in three dimensions. If the extension in the third dimension is rather small the curve will fit into a n×n×1 arrangement of 3D-boxes (cubes of size L1×L1×L1) in a plane. Then the calculations can be performed as described above. Here the second grid will be a 2n×2n×1 grid of cuboids of size L2×L2×L1.
If the extension in the third dimension is larger a n×n×n first grid and an 2n×2n×2n second grid will be taken into account. The construction principles for the relevant grids as explained above for two dimensions apply equally in three dimensions.
Grid Dimension Curves
In another example, the antenna or one or more antenna elements or antenna parts may be miniaturized by shaping at least a portion of the conducting trace to include a grid dimension curve. For a given geometry lying on a planar or curved surface, the grid dimension of the curve may be calculated as follows. First, a grid with substantially square identical cells of size L1 is placed over the geometry of the curve, such that the grid completely covers the geometry, and the number of cells N1 that include at least a point of the geometry are counted. Second, a grid with cells of size L2 (L2 being smaller than L1) is also placed over the geometry, such that the grid completely covers the geometry, and the number of cells N2 that include at least a point of the geometry are counted again. The grid dimension D is then computed as:
For the purposes of this document, the grid dimension may be calculated by placing the first and second grids inside the minimum rectangular area enclosing the curve of the antenna and applying the above algorithm. The minimum rectangular area is an area in which there is not an entire row or column on the perimeter of the grid that does not contain any piece of the curve.
The first grid may, for example, be chosen such that the rectangular area is meshed in an array of at least 25 substantially equal preferably square cells. The second grid may, for example, be chosen such that each cell of the first grid is divided in 4 equal cells, such that the size of the new cells is L2=½ L1, and the second grid includes at least 100 cells.
Depending on the size and position of the squares of the grid the number of squares of the smallest rectangular may vary. A preferred value of the number of squares is the lowest number above or equal to the lower limit of 25 identical squares that arranged in a rectangular or square grid cover the curve or the relevant portion of the curve. This defines the size of the squares. Other preferred lower limits here are 50, 100, 200, 250, 300, 400 or 500. The grid corresponding to that number in general will be positioned such that the curve touches the minimum rectangular at two opposite sides. The grid may generally still be shifted with respect to the curve in a direction parallel to the two sides that touch the curve. Of such different grids the one with the lowest value of D is preferred. Also the grid whose minimum rectangular is touched by the curve at three sides (see as an example
The desired grid dimension for the curve may be selected to achieve a desired amount of miniaturization. The grid dimension should be larger than 1 in order to achieve some antenna size reduction. If a larger degree of miniaturization is desired, then a larger grid dimension may be selected, such as a grid dimension ranging from 1.5-3 (e.g., in case of volumetric structures). In some examples, a curve having a grid dimension of about 2 may be desired. For the purposes of this patent document, a curve or a curve where at least a portion of that curve is having a grid dimension larger than 1 may be referred to as a grid dimension curve.
In general, for a given resonant frequency of the antenna, the larger the grid dimension the higher the degree of miniaturization that will be achieved by the antenna.
One example way of enhancing the miniaturization capabilities of the antenna is to arrange the several segments of the curve of the antenna pattern in such a way that the curve intersects at least one point of at least 50% of the cells of the first grid with at least 25 cells (preferably squares) enclosing the curve. In another example, a high degree of miniaturization may be achieved by arranging the antenna such that the curve crosses at least one of the cells twice within the 25 cell grid (of preferably squares), that is, the curve includes two non-adjacent portions inside at least one of the cells or cells of the grid. In general the grid may have only a line of cells but may also have at least 2 or 3 or 4 columns or rows of cells.
For a more accurate calculation of the grid dimension, the number of square cells may be increased up to a maximum amount. The maximum number of cells in a grid is dependent upon the resolution of the curve. As the number of cells approaches the maximum, the grid dimension calculation becomes more accurate. If a grid having more than the maximum number of cells is selected, however, then the accuracy of the grid dimension calculation begins to decrease. Typically, the maximum number of cells in a grid is one thousand (1000).
For example,
It should be understood that a grid-dimension curve does not need to include any straight segments. Also, some grid-dimension curves might approach a self-similar or self-affine curves, while some others would rather become dissimilar, that is, not displaying self-similarity or self-affinity at all (see for instance
The terms explained above can be also applied to curves that extend in three dimensions. If the extension in the third dimension is rather small the curve will fit into an arrangement of 3D-boxes (cubes) in a plane. Then the calculations can be performed as described above. Here the second grid will be composed in the same plane of boxes with the size L2×L2×L1.
If the extension in the third dimension is larger a m×n×o first grid and an 2m×2n×2o second grid will be taken into account. The construction principles for the relevant grids as explained above for two dimensions apply equally in three dimensions. Here the minimum number of cells preferably is 25, 50, 100, 125, 250, 400, 500, 1000, 1500, 2000, 3000, 4000 or 5000.
Contour Curve
The contour-curve is defined by the ratio Q=C/E given by the ratio of the length C of the circumference of the curve and of the largest extension E of said curve. The circumference is determined by all the borders (the contour) between the inside and the outside of the curve.
The largest extension E is determined by the diameter of the smallest circle, which encloses the curve entirely.
The more complex the curve, the higher the ratio Q. A high value of Q is advantageous in terms of miniaturization.
Examples of contour-curves are shown in
In
In
In
If the curve is on a folded, bent or curved or otherwise irregular surface, or is provided in any another three-dimensional fashion (i.e. it is not planar), the ratio Q is determined by the length C of the circumference of the orthogonal projection of the curve onto a planar plane. The corresponding largest extension E is also determined from this projection onto the same planar plane. The plane preferably lies in such a way in relation to the three-dimensional curve that the line, which goes along the largest extension F of the three-dimensional curve, lies in the plane (or a parallel and hence equivalent plane). The largest extension F of the three-dimensional curve lies along the line connecting the extreme points of the curve, which contact a sphere, which is given by the smallest possible sphere including the entire curve. Further the plane is oriented preferably in such a way, that the outer border of the projection of the curve onto the plane covers the largest possible area. Other preferred planes are those on which the value of C or Q of the projection onto that plane is maximized.
If for a three-dimensional curve a single projection plane is given in which the ratio Q of the projection of the curve onto the plane is larger than the specified minimal value, or this is the case for one of the above mentioned preferred projection planes the curve is said to be a contour curve. Possible minimum values for Q are 2.1, 2.25, 2.5, 2.75, 3.0, 3.1, 3.2, 3.25, 3.3, 3.5, 3.75, 4.0, 4.5, 5.0, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30, 40, 50, 75, and 100.
In
Another plane 12 is shown in
Multilevel Structures
In another example, at least a portion of the conducting trace of the antenna may be coupled, either through direct contact or electromagnetic coupling, to a conducting surface, such as a conducting polygonal or multilevel surface. Further the curve of the antenna or of the SMD component may include the shape of a multilevel structure. A multilevel structure is formed by gathering several geometrical elements such as polygons or polyhedrons of the same type or of different type (e.g., triangles, parallelepipeds, pentagons, hexagons, circles or ellipses as special limiting cases of a polygon with a large number of sides, as well as tetrahedral, hexahedra, prisms, dodecahedra, etc.) and coupling these structures to each other electromagnetically, whether by proximity or by direct contact between elements.
At least two of the elements may have a different size. However, also all elements may have the same or approximately the same size. The size of elements of a different type may be compared by comparing their largest diameter.
The majority of the component elements of a multilevel structure have more than 50% of their perimeter (for polygons) or of their surface (for polyhedrons) not in contact with any of the other elements of the structure. Thus, the component elements of a multilevel structure may typically be identified and distinguished, presenting at least two levels of detail: that of the overall structure and that of the polygon or polyhedron elements which form it. Additionally, several multilevel structures may be grouped and coupled electromagnetically to each other to form higher level structures. In a single multilevel structure, all of the component elements are polygons with the same number of sides or are polyhedrons with the same number of faces. However, this characteristic may not be true if several multilevel structures of different natures are grouped and electromagnetically coupled to form meta-structures of a higher level.
A multilevel antenna includes at least two levels of detail in the body of the antenna: that of the overall structure and that of the majority of the elements (polygons or polyhedrons) which make it up. This may be achieved by ensuring that the area of contact or intersection (if it exists) between the majority of the elements forming the antenna is only a fraction of the perimeter or surrounding area of said polygons or polyhedrons.
One example property of a multilevel antennae is that the radioelectric behavior of the antenna can be similar in more than one frequency band. Antenna input parameters (e.g., impedance) and radiation patterns remain similar for several frequency bands (i.e., the antenna has the same level of adaptation or standing wave relationship in each different band), and often the antenna presents almost identical radiation diagrams at different frequencies. The number of frequency bands is proportional to the number of scales or sizes of the polygonal elements or similar sets in which they are grouped contained in the geometry of the main radiating element.
In addition to their multiband behavior, multilevel structure antennae may have a smaller than usual size as compared to other antennae of a simpler structure. (Such as those consisting of a single polygon or polyhedron). Additionally, the edge-rich and discontinuity-rich structure of a multilevel antenna may enhance the radiation process, relatively increasing the radiation resistance of the antenna and reducing the quality factor Q i.e. increasing its bandwidth.
A multilevel antenna structure may be used in many antenna configurations, such as dipoles, monopoles, patch or microstrip antennae, coplanar antennae, reflector antennae, wound antennae, antenna arrays, or other antenna configurations. In addition, multilevel antenna structures may be formed using many manufacturing techniques, such as printing on a dielectric substrate by photolithography (printed circuit technique); dieing on metal plate, repulsion on dielectric, or others.
The SMD component, including a conducting trace defining an antenna element allows for the mounting of an antenna with standard mass production methods. This is to a large amount possible only due to the miniaturization of the antenna due to the complex geometry of the trace which may be a space-filling curve, a grid-dimension curve, a box counting curve or a contour-curve or the curve having the shape of a multilevel structure.
An IC-package is a device comprising an integrated circuit. Usually the integrated circuit may be enclosed by a protective material such as plastic. Contact means such as pins are accessible from the outside of the package in order to contact the integrated circuit. The IC-package here includes an antenna with a conducting trace which has a complex geometry. The conducting trace or parts thereof may also be connected to the contact means accessible from the outside of the package. The conducting trace or parts thereof may also be connected to the integrated circuit. The integrated circuit may be provided for feeding the antenna. It may also be provided for performing data processing in transmission or reception.
The conducting trace may also be connected at certain points to ground of the IC-package such that certain antenna resonance modes are suppressed or supported.
The integrated circuit may be provided with a metal frame. Such frames may be used for guiding the cutting process of the substrate of the IC-package. The frame preferably has gaps which reduce currents flowing on the frame.
The wireless device has one or more of the above-mentioned antennae and/or one or more of the above-mentioned SMD components and/or one or more of the above mentioned IC-packages.
The antenna or the antenna element of the SMD or the antenna of the IC-package can be contacted in different ways. It is possible to contact only one feeding point so that by appropriate selection of the feeding point, the desired resonant frequency or any other desired antenna characteristic is given.
In a preferred embodiment, two or three or more feeding points/access ports/feeding purposes points are electrically contacted to other electric circuits of the wireless device such that the used feeding point can be selected after the production of the wireless device by an, e.g. electrical switch. This switch may be mechanically operated or electrically operated, such as a transistor or a combination of transistors or the like. The antenna may be connected to an integrated circuit (e.g. the one of the IC-package or any other integrated circuit of the wireless device) which feeds the antenna and/or which connects separated parts of the antenna.
With two, three or more feeding points/access ports electrically contacted, it is also possible not only to use a single feeding point, but also to provide energy to the antenna at two, three or more feeding points at the same time. By using different amounts of energy provided to the different feeding points, antenna characteristics such as resonant frequency, impedance, bandwidth and efficiency may be adjusted continuously.
By selecting a specific contacting mode, the antenna may be operated at resonance at different operating frequencies. This allows for adaptation of the wireless device to different wireless communication systems. Also by connecting one or more feeding points to ground of the wireless device it is possible to select certain antenna properties.
In a preferred embodiment, for at least a part of the antenna and/or the SMD component and/or the IC-package a space is provided between the antenna and/or the SMD component and/or the IC-package to any other member or constructive element of the wireless device, such that the electrical characteristics of the antenna and/or antenna element and/or IC-package can be maintained after mounting the antenna and/or the SMD component and/or IC-package. A space is in particular useful if the conducting trace is provided on one side of a substrate or circuit board and this side of the substrate faces a circuit board to which substrate or circuit board is mounted. The conducting trace is then protected by the space from mechanical impact by the circuit board due to e.g. scratching. The other side of the antenna or the SMD component may be in contact to other parts of the wireless device.
Even if the antenna and/or the SMD component and/or the IC-package allow for different operating frequencies, it may be in a preferred embodiment desirable to have two, three or more antennae or SMD components with an antenna element or IC-packages. Thereby, it is possible to provide even more operating frequencies to the wireless device. Further it is possible to operate the wireless device simultaneously at two, three or more different operating frequencies using the two, three or more different antennae and/or antenna elements. Also this is interesting for a wireless device featuring diversity and/or multiple input multiple output (MIMO) functionalities. Here at least some of the antennae have the same resonant frequency.
In order to physically hold the antenna or the SMD component or IC-package within the wireless device, it may be possible to use the feeding points, which are not electrically contacted. This may be done, e.g., by soldering the feeding (purposes) point or the access port to a circuit board, where, however, the metallic part of the circuit board has no further electrical connections such that the feeding point is not used to feed energy to the conducting trace or to ground the conducting trace.
The conducting trace is provided in the wireless device, such that a ground plane of the wireless device does not cover the antenna. This allows for a good emission of the radiation by the antenna.
The method allows for selection of the desired antenna property (e.g. the desired resonant frequency) by selecting the appropriate feeding point.
Preferred embodiments of the invention are disclosed in the figures. It is shown in:
a shows a schematic example of an antenna 14. The antenna 14 has three feeding points 16a, 16b, 16c which here have as an example only, the shape of a square and may be used as solder pads. Between feeding point 16a and 16b, only schematically the connection of the two feeding points is indicated by the dotted line 15a. Here the dotted line 15a is shown as a straight line and is supposed to be substituted by a complex curve such as a space-filling curve, a grid-dimension curve, a box-counting curve, a contour-curve or curve having the shape of a multilevel structure. Equally, the connection between feeding point 16b and 16c is shown schematically only by the dotted line 15b which may be appropriately substituted by a more complex curve such as a space-filling curve, a grid-dimension curve, a box counting curve, a contour-curve or a curve having the shape of a multilevel structure. In
A possible configuration of the antenna 14 is also given by the configuration shown in
Another connection mode of the three feeding points 16a, 16b, 16c is shown in
More radiating arms and/or more feeding points may be added to the connection modes shown in
In
The conducting trace 20 defines at least one curve with two ends. One of the ends of the conducting trace 20 may include a connection or feeding port, as illustrated in
For miniaturization purposes, at least a portion of the curve defining the conducting trace may be shaped as a space-filling curve, a box-counting, or grid-dimension curve, or a fractal based curve or as a contour-curve or have the shape of a multilevel structure. The conducting trace may include a single radiating arm, or may branch-out in two or more radiating arms. The conducting trace may also be coupled, either through direct contact or electromagnetic coupling, to a conducting polygonal or multilevel surface.
Referring again to
In one example, the pads connected along the path of the antenna which are not used to feed the antenna may be used as attachment pads.
In the example of
In
Example characteristics of an antenna mounted as shown in
While in
One possible application of the multi-feed antenna is an antenna for GPS systems. Depending on the chosen antenna feeding point it can either cover the 1.575 GHz band or the 1.227 GHz frequency band.
Some additional example applications for a tunable antenna having multiple feeding points are illustrated in
Example Methods for Manufacturing Tunable Antenna Component
Following is a description of several possible methods and processes for manufacturing a tunable antenna component with multiple feeding points, as described herein.
In one example, the antenna can be manufactured to be a SMT or SMD component. In this case, the antenna may be etched on a dielectric substrate, such as FR4, Neltek, Rogers or an equivalent material.
In other examples, ceramic, deposited materials and LCP could also be used. Different package manufacturing technologies, such as thin film and thick-film, can be used. A variety of package architectures are also possible, such as DIP, QFP, PGA, BGA, CSP or others.
The following example data is related to the mechanical aspects for manufacturing of the antenna product as a SMT or SMD component.
An example of an antenna is shown in
Example Specifications for Dielectric
Example Specifications for Metal Laminate:
Example Specifications for Cover Lay:
Example Specifications for INK
The exploded view of the layers of an antenna is shown in
Example Assembly Process:
As a SMT or SMD component, an example assembly process flow is as follows. First, a solder paste may be applied to the mounting pads on the printed wiring board and the devices are placed thereon, and then soldered. When simultaneous reflow for double-sided surface mounting or flow soldering is performed, a temporary adhesive may be used to affix the devices to the printed wiring board before the soldering is performed. A cleaning process may be performed to remove the residual flux, etc., after the soldering process is performed, after which an inspection may be performed. A baking process may be performed before soldering when a moisture-removal treatment is required when a plastic package is used
Example Environmental Integrity Test
The example antenna maintains all the dimensions and electric characteristic in the range that tests IEC 68-2-56 (humidity) and IEC 68-2-1.2 (temperature) operate.
Packing Example
The antennas may, for example, be delivered in tape and reel.
The antenna is formed from a conducting trace attached to a surface of the IC package. The antenna may, for example, be attached to the dielectric or semiconductor substrate of the package. The conducting trace may, for example, be made of copper, aluminum, brass, silver, gold or some other good conducting alloy. The substrate material to which the antenna is attached may, for example, be a PCB material, such as a low cost material based on plastic, epoxy, FR4, fiber glass or laminate materials or a more sophisticated material such as ceramic (LTCC, HTCC), glass, or semiconductor materials. The conductive trace may, for example, be fabricated on at least one of the layers of the substrate by a standard manufacturing process, such as thick film processes (printing, etching) or thin film processes.
The antenna includes a plurality of possible feed points (see feeding points # 1-# 5 in
The conductive trace of the antenna defines one or more curves (the term curve as used herein may include curved and/or straight segments.) In some examples, for miniaturization purposes, at least a portion of the curve(s) defining the conducting trace may define a space-filling curve, a box-counting curve, a grid-dimension curve, a fractal based curve and/or a contour curve, or have the shape of a multilevel structure, as described above. In some examples, the conductive trace may define a single curve, while in other examples it may define two or more curves, each of which may include a space-filling curve, box-counting curve, grid-dimension curve, a fractal based curve and/or a contour curve or have the shape of a multilevel structure. Additionally, in some examples a portion of the curve(s) may be coupled either through direct contact or electromagnetic coupling to a multilevel structure, as described above.
The IC package may provide access to the multiple feed points of the antenna from outside of the package. In this manner, the end-user can choose the proper port for feeding the antenna and/or define the connectivity among the other ports to optimally tune the antenna in terms of resonance frequency and impedance, for example to a wireless device in which the IC package is mounted. By providing user access to the multiple feed points, a single package layout can be standardized and used in a wide range of applications, for example in different devices with different form factors (such as laptops, PDAs, MP3 players, handsets, GPS navigators, multimedia terminals, etc.), and in different geographical domains with different spectrum allocations for wireless terminals.
Also it may be possible that no direct access to the feed points is given from the outside. In this case the antenna is connected to the chip which feeds and controls the antenna. The antenna is therefore contacted indirectly from the outside through the chip.
In some arrangements, one or more of the several ports at which the antenna can be accessed through pads of the package may be used as short-circuit points for the antenna, that is points that are connected to an internal ground plane of the package or to the external ground plane on the PCB of the device in which the IC package is mounted. Thus, the same antenna geometry can be arranged for instance as a monopole antenna or as an inverted-F antenna (IFA/PIFA). The IFA configuration of the antenna can be advantageous for some types of ground planes on which the antenna impedance is capacitive.
The configurability of the antenna may provide the end-user with extra degrees of freedom to adjust for instance the resonance frequency, input impedance, bandwidth, gain, efficiency and radiation pattern of the antenna to an even wider variety of application environments with PCBs of many different sizes, shapes and clearances.
In some examples, the antenna geometry may include several separated parts, or blocks, not necessarily equal, each one containing at least one point that can be accessed from the outside of the package, for instance through a pad, or from the chip. Depending on the PCB on which the AiP (Antenna in Package) module is mounted, the antenna feeding point, the connections between different parts of the antenna, and whether these parts are connected to ground or not can be selected to optimize the resonance frequency, the input impedance and/or the bandwidth of the antenna. In some examples, antenna geometries may also include parasitic elements.
The assembly of a die or chip to the substrate of a FWSiP/FWSoC module may result in the substrate becoming warped. This problem can be of especially concern in Multi-Chip Modules (MCMs). When reflowing a chip onto a package substrate, the cycle of heating and subsequent cooling of the surfaces that come together upon assembly may develop stresses on the substrate due to the differences between the thermal expansion coefficient of the material of the substrate and that of the chip. If the substrate is not rigid enough, it will become warped compromising the planarity, and hence the solderability, of the resulting FWSiP/FWSoC module.
The warpage effect is more typically severe in thin substrates, particularly when the chip is positioned in a corner of the substrate to leave room for the antenna. Reinforcement of the substrate may be necessary to avoid this problem. This can be achieved by placing an extra layer of dielectric material on top of the antenna. The detuning of the resonance frequency of the antenna can be corrected by selecting the appropriate feeding pad.
In some examples, the geometry of the antenna may be such that it is convenient to substantially arrange the die or chip at the center of the substrate and reserve the outer perimeter region of the substrate for the footprint of the antenna. Such an arrangement may minimize the warpage of the substrate for a given thickness, as the stresses produced by the assembly of the chip are more uniformly distributed.
Some semiconductor and/or package fabrication technologies use a frame to delimitate the area of the die or the substrate. Such a frame is typically used as a reference when cutting a semiconductor wafer or a laminate substrate panel with high degree of accuracy. This frame is often made of lossy metals (for instance tantalum), which can compromise the frequency tuning, bandwidth and/or radiation performance of the antenna integrated in the package, as the currents induced on the conductive frame may tend to cancel those of the antenna. This problem may be reduced or eliminated by including gaps along the perimeter of the frame, because the presence of discontinuities on the frame makes it difficult for currents to be induced, while still providing guidance for the cutting process.
The IC package is attached to the PCB substrate such that the antenna footprint is included entirely within the exposed portion of the PCB substrate, with the tip of the antenna positioned at the upper right corner of the PCB substrate in order to provide as much clearance as possible between the tip of the antenna and the PCB ground plane. Positioning the IC package at the corner of the PCB substrate enables the tip of the antenna to be positioned away from the PCB ground plane, while minimizing the amount of exposed PCB substrate. That is, the IC package position allows a maximum amount of the PCB substrate to be covered by the ground plane, while still achieving the improved antenna performance resulting from positioning the tip of the antenna at a distance away from the PCB ground plane.
In the example of
In other examples, the miniature antenna may include several pads for feeding and/or grounding along the antenna path. In order to achieve the desired performance, the antenna could be grounded at more than one of the pads connected along to its path.
The arrangement of the antenna inside the IC package in the example of
In one example, the interconnection between two or more of the antenna blocks of
a shows an IC package substrate that contains an antenna and a metal frame on its perimeter that is used as a reference to cut a single IC substrate out of a panel.
Example Applications
The flexible design of the antenna, and its careful integration in the IC package, and on the PCB, make it possible to use this FWSiP solution in a wide set of wireless connectivity applications. Some example target market segments where it can be used include: Bluetooth™ enabled handsets, Mini-PCI (Notebook PC with Wi-Fi module integrated), Compact flash wireless cards, Wireless USB/UART dongles, PCMCIA wireless cards, Headsets, Pocket PC with integrated Wi-Fi, Access points for hot-spots, Wireless switches, or Wireless sensors.
While the invention has been described with respect to specific examples including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques that fall within the spirit and scope of the invention as set forth in the appended claims.
This application is related to application number U.S. 60/613,394 filed on Sep. 27, 2004, in the U.S. and to application number U.S. 60/640,380 filed on Dec. 30, 2004 in the U.S. and claims priority to those applications, which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2005/054297 | 9/1/2005 | WO | 00 | 3/26/2007 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2006/034940 | 4/6/2006 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3680135 | Boyer | Jul 1972 | A |
| 3713162 | Munson et al. | Jan 1973 | A |
| 4243990 | Nemit | Jan 1981 | A |
| 4381566 | Kane | Apr 1983 | A |
| 4626862 | Ma | Dec 1986 | A |
| 4843468 | Drewery | Jun 1989 | A |
| 5363114 | Shoemaker | Nov 1994 | A |
| 5621199 | Calari | Apr 1997 | A |
| 5621913 | Tuttle | Apr 1997 | A |
| 5710458 | Iwasaki | Jan 1998 | A |
| 5778308 | Sroka et al. | Jul 1998 | A |
| 6011518 | Yamagishi et al. | Jan 2000 | A |
| 6087990 | Thill et al. | Jul 2000 | A |
| 6107920 | Eberhardt | Aug 2000 | A |
| 6147655 | Roesner | Nov 2000 | A |
| 6181281 | Desclos | Jan 2001 | B1 |
| 6198438 | Herd et al. | Mar 2001 | B1 |
| 6236366 | Yamamoto | May 2001 | B1 |
| 6239752 | Blanchard | May 2001 | B1 |
| 6263193 | Iseki | Jul 2001 | B1 |
| 6285342 | Brady | Sep 2001 | B1 |
| 6307519 | Livingston | Oct 2001 | B1 |
| 6317092 | Schweinitz | Nov 2001 | B1 |
| 6320543 | Ohata | Nov 2001 | B1 |
| 6333719 | Varadan et al. | Dec 2001 | B1 |
| 6362784 | Kane et al. | Mar 2002 | B1 |
| 6373447 | Rostoker | Apr 2002 | B1 |
| 6377217 | Zhu | Apr 2002 | B1 |
| 6388631 | Livingston et al. | May 2002 | B1 |
| 6421013 | Chung | Jul 2002 | B1 |
| 6424315 | Glenn | Jul 2002 | B1 |
| 6459413 | Tseng et al. | Oct 2002 | B1 |
| 6504507 | Geeraert | Jan 2003 | B2 |
| 6611237 | Smith | Aug 2003 | B2 |
| 6639555 | Kane et al. | Oct 2003 | B1 |
| 6646609 | Yuasa | Nov 2003 | B2 |
| 6650295 | Ollikainen | Nov 2003 | B2 |
| 6662028 | Hayes | Dec 2003 | B1 |
| 6670921 | Slevenpiper | Dec 2003 | B2 |
| 6693594 | Pankinaho | Feb 2004 | B2 |
| 6744411 | Osterhues et al. | Jun 2004 | B1 |
| 6756939 | Chen | Jun 2004 | B2 |
| 6762719 | Subetic | Jul 2004 | B2 |
| 6765536 | Phillips et al. | Jul 2004 | B2 |
| 6870507 | Anguera Pros et al. | Mar 2005 | B2 |
| 7026997 | Rahola | Apr 2006 | B2 |
| 7202835 | Chiang et al. | Apr 2007 | B2 |
| 7310065 | Anguera Pros et al. | Dec 2007 | B2 |
| 7417588 | Castany et al. | Aug 2008 | B2 |
| 7471246 | Soler Castany et al. | Dec 2008 | B2 |
| 7511675 | Puente-Baliarda et al. | Mar 2009 | B2 |
| 7675470 | Sanz et al. | Mar 2010 | B2 |
| 20020005433 | Nochi | Jan 2002 | A1 |
| 20020058539 | Underbrink | May 2002 | A1 |
| 20030122721 | Sievenpiper | Jul 2003 | A1 |
| 20030201942 | Poilasne | Oct 2003 | A1 |
| 20040014428 | Franca-Neto | Jan 2004 | A1 |
| 20040119644 | Puente Baliarda | Jun 2004 | A1 |
| 20040125027 | Rubinshteyn et al. | Jul 2004 | A1 |
| 20040145521 | Hebron | Jul 2004 | A1 |
| 20040227678 | Sievenpiper | Nov 2004 | A1 |
| 20070040751 | Boyle | Feb 2007 | A1 |
| Number | Date | Country |
|---|---|---|
| 0 655 797 | May 1995 | EP |
| 0902472 | Mar 1999 | EP |
| 0969375 | Jan 2000 | EP |
| 0978729 | Feb 2000 | EP |
| 1011167 | Jun 2000 | EP |
| 1085597 | Mar 2001 | EP |
| 1126522 | Aug 2001 | EP |
| 1130677 | Sep 2001 | EP |
| 1137100 | Sep 2001 | EP |
| 1307078 | Feb 2002 | EP |
| 1198027 | Apr 2002 | EP |
| 1248317 | Oct 2002 | EP |
| 1326302 | Nov 2003 | EP |
| 1396906 | Mar 2004 | EP |
| 00909089.5 | Aug 2005 | EP |
| 1610411 | Dec 2005 | EP |
| 2112163 | Mar 1998 | ES |
| 2849288 | Jun 2004 | FR |
| 11220319 | Aug 1999 | JP |
| 2001332924 | Nov 2001 | JP |
| 2002190706 | Jul 2002 | JP |
| 2006174449 | Jun 2006 | JP |
| 9706578 | Feb 1997 | WO |
| 9927608 | Jun 1999 | WO |
| 9934480 | Jul 1999 | WO |
| 0105048 | Jan 2001 | WO |
| 0122528 | Mar 2001 | WO |
| 0154225 | Jul 2001 | WO |
| 0229929 | Apr 2002 | WO |
| 02052679 | Jul 2002 | WO |
| 02060004 | Aug 2002 | WO |
| 02095869 | Nov 2002 | WO |
| 02089246 | Nov 2002 | WO |
| 02096166 | Nov 2002 | WO |
| 03050913 | Jun 2003 | WO |
| 03065499 | Aug 2003 | WO |
| 03096475 | Nov 2003 | WO |
| 03096474 | Nov 2003 | WO |
| 2004025778 | Mar 2004 | WO |
| 2004038852 | May 2004 | WO |
| 2004042868 | May 2004 | WO |
| 2004097976 | Nov 2004 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20080062049 A1 | Mar 2008 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60613394 | Sep 2004 | US | |
| 60640380 | Dec 2004 | US |
