A FLEXIBLE PATCH ANTENNA

Technical field of the invention

The present invention relates to patch antennas suitable for integration into a textile product, such as a garment, mattresses and/or automotive parts such as e.g. dashboards, bumpers and alike.

Background of the invention

Antennas, which are integrated in a textile product such as a garment and comprising woven or knitted textile structures, are known from e.g. WO01/39326A1. These patch antennas comprise two electrically conductive flexible elements, which are mechanically coupled to, but mutually separated by an electrically insulating fabric.

These patch antennas have the disadvantage that they may not function sufficiently when integrated in parts of a textile product, e.g. a garment, where the textile product is bent when worn. The presently known antennas tend to be so flexible, that this flexibility makes them rather unreliable in case of demanding applications, such as in case of integration into protective clothing e.g. fire fighters suits, rescue workers suits or military battle dresses.

Different types of textile antennas have been designed in the past. They are intended to be integrated in normal casual clothing that is not meant for use in critical situations such as fire fighter suits, rescue workers suits or military battle dresses.

Traditional garment fabrics used as antenna substrate do not exhibit resistance to harsh environmental conditions such as high temperatures, humidity and stress. Moreover, they tend to trap moisture, which is a major disadvantage for fire fighters producing sweat when active in fires and high-temperature environments.

Furthermore, these fabrics are commonly rather thin (such as less than 1 mm), preventing the design of a broadband antenna.

Summary of the invention

It is an object of the present invention to provide good patch antennas. It is an advantage of embodiments of the present invention to provide a patch antenna, more precisely a flexible patch antenna, which guarantees to a larger extent its ability to emit and/or receive signals at given frequencies when bending the patch.

The above objective is accomplished by a flexible patch antenna according to the present invention. According to a first aspect of the present invention, a flexible patch antenna is provided. The flexible patch antenna comprises a first dielectric layer of a flexible material, e.g. of an elastomer, textile, such as non-woven, woven, knitted material, the first dielectric layer having a first surface and a second surface, a first flexible patch element being mounted contiguous to the first surface of the first dielectric layer and a flexible ground plane being mounted contiguous to the second surface of the first dielectric layer. The elastomer can be a foam. The elastomer, textile, such as non-woven, woven, knitted material is preferably hydrophobic or is made hydrophobic by means of a coating. The pore size and the surface tension of the foamed elastomer, textile, such as non-woven, woven, knitted material is preferably such as to minimize moisture absorption by the dielectric layers.

The patch element is preferably aperture coupled to a feed or coaxial coupled. The antenna preferably has radiating edges. The antenna preferably is multimodal. The use of edges of different lengths and the generation of more than one mode having differing centre frequencies provides a broadband antenna. The antenna preferably receives/transmits non-linearly polarised electromagnetic radiation. The patch element is preferably mounted above a flexible ground plane.

The antenna has a central resonant frequency in planar state (fcp) and has a -1 OdB bandwidth in planar state of at least 1.30% of the central resonant frequency in planar state (fcp). Values up to 10% or 15% can be achieved.

An antenna advantageously is designed to operate within a certain frequency band. This frequency band is characterized by means of its central resonant frequency (also referred to as central frequency) and its bandwidth, i.e.

the width of the frequency band.

The frequency band refers to the "impedance bandwidth" where the S1 1 - reflection coefficient measured at the antenna terminals is less than or equal to - 1 O dB. Percentages of a bandwidth (e.g. a bandwidth of 1.3%) is to be understood as fc being the central frequency, the frequency band ranges from f1 to f2 (f1 <fc<f2), wherein all frequencies in the range of f1 to f2 are frequencies at which the S1 1 -reflection coefficient measured at the antenna terminals is less than or equal to -10 dB. The bandwidth in absolute figures is thus expressed as f2-f 1. The percentage is expressed as 100 ^* (f2-f1 )/fc.

According to some embodiments of the present invention, the antenna may have a central resonant frequency in bent state (fcb), the central resonant frequency in bent state falling within the -1 OdB bandwidth in planar state.

The bent state is defined as the ground plane of the flexible patch antenna being bent for providing a radius of curvature of 30mm to the ground plane.

It is understood that flexible patch antennas according to the present invention may optionally be bendable to a larger extent, i.e. providing a radius of curvature to the ground plane of smaller than 30mm.

According to some embodiments of the present invention, the antenna may have a central resonant frequency in bent state (fcb) and further may have a -1 OdB bandwidth in bent state of at least 1.30% of the central resonant frequency in bent state (fcb).

Optionally the antenna maintains at least the same frequency band of operation with a -10 dB bandwidth of at least 1.3% in planar state and in bent state.

When the flexible patch antenna according to embodiments of the first aspect of the present invention is integrated in a garment and the garment is not worn, the patch antenna defines a plane by means of the surface of its patch element. Upon bending the patch antenna, i.e. bending according to an axis parallel to the plane defined by the surface of the patch element, the frequency band in which the antenna can emit or receive signals, may alter. The central frequency may shift and/or the bandwidth may change. By providing a flexible patch antenna according to embodiments of the first aspect of the present invention, the influence of this shift of central resonant frequency and change in

bandwidth is kept within acceptable and workable ranges.

As this antenna may be used to cooperate with an electric circuit (EC) of the emitter and/or receiver working in a given frequency range, the antenna according to embodiments of the first aspect of the present invention remains suitable to emit or receive signals at appropriate frequencies.

The term "flexible" is to be understood as being suitable to ply and thereafter regain its original planar shape, when bended over a radius of curvature of 30 mm or optionally even less.

The patch element may be understood as an electrically conductive patch element, functioning as a radiator of the antenna. The ground plane also may be understood as an electrically conductive plane. The patch element and the ground plane advantageously may be mutually separated by the dielectric layer.

According to some embodiments of the present invention, the patch element may have a substantially polygonal shape, e.g. a substantially polygonal shape being provided with at least one aperture. According to some embodiments of the present invention, the patch element may have a substantially rectangular shape, e.g. a substantially rectangular shape being provided with at least one aperture. According to some embodiments of the present invention, the patch element may have a substantially triangular shape, e.g. a substantially triangular shape being provided with at least one aperture. According to some embodiments of the present invention, the patch element may have a substantially circular or oval or elliptical shape, e.g. a substantially circular or oval or elliptical shape being provided with at least one aperture.

According to some embodiments of the present invention, the patch element may have a truncated substantially rectangular or triangular shape.

Optionally, the substantially rectangular shape may have a first pair of parallel sides having a length L1 and a second pair of parallel sides having a length L2, for which L1 and L2 are situated between 55 and 100% of A ₀ /2, wherein A ₀ equals c/fcp, fcp being the central resonant frequency in planar state, c being the speed of light.

As an example, the central resonant frequency in planar state (fcp) for which the antenna is designed, may be e.g. 1575.42 MHz or 2.45 GHz. A ₀ is the free space wavelength. The difference between L1 and L2 optionally does not exceed 10%.

Preferably the substantially rectangular shape may be a quasi-square shape, wherein the quasi square shape has four substantially rectangular corners, and wherein the quasi-square shape has a first pair of parallel sides having a length L1 and a second pair of parallel sides having a length L2. According to some embodiments of the present invention, the shape of the patch element may be provided with at least one aperture.

According to some embodiments of the present invention, the shape of the patch element may be an elliptical shape or a non-circular shape.

According to some embodiments of the present invention, the shape of the patch element may be a triangular shape.

According to some embodiments of the present invention, the antenna further may comprise at least a second flexible patch mounted contiguous to the first surface of the dielectric layer, the at least second patch forming a parasitic radiator. According to some embodiments of the present invention, the antenna further may comprise at least a second dielectric layer of a flexible material e.g. elastomer, textile, such as non-woven, woven, knitted material which is preferably hydrophobic or is made hydrophobic by means of a coating. The elatomer may be foamed. The pore size and the surface tension of the foamed elastomer, textile, such as non-woven, woven, knitted material is preferably such as to minimize moisture absorption by the dielectric layers. The second dielectric layer of a flexible material s mounted contiguous to the side of the first flexible patch element opposite from the first dielectric layer. The antenna further may comprise a second flexible patch element being mounted contiguous to the surface of the second dielectric layer at the side opposite to the first flexible patch element.

The patch element is preferably aperture coupled to a feed or coaxial coupled. The antenna preferably has radiating edges. The antenna preferably is multimodal. The antenna preferably receives/transmits non-linearly polarised electromagnetic radiation. The patch element is preferably mounted above a flexible ground plane.

The antenna has a central resonant frequency in planar state (fcp) and has a -1 OdB bandwidth in planar state of at least 1.30% of the central resonant frequency in planar state (fcp). Optionally further additional dielectric layers and further patch elements may be stacked providing a plurality of alternating

dielectric layers and patch elements.

An advantage of the patch antenna according to embodiments of this first aspect of the present invention is that the patch antenna is provided with a wider bandwidth for receiving or emitting signals, e.g. due to the selection of the shape of the patch element. When the patch antenna, more particular the patch element, is bent, the wider bandwidth ensures to a larger extent that the bandwidth during bending remains to encompass the frequency band for which the antenna was designed in non-bent form. The fact that foam is used reduces to a large extent the drapability of the patch antenna, while still sufficient comfort is provided to the user of the patch antenna, e.g. wear comfort when the patch antenna is integrated in a textile product such as a garment. By properly selecting the drapability of the layer of flexible material e.g. of an elastomer, textile, such as non-woven, woven, knitted material elastomer material, e.g. a foamed synthetic material, the drapability, thus the ability of the patch antenna to deform with uni- or even multidirectional curvature, can be limited within acceptable ranges. Suitable flexible elastomer materials are closed cell elastomer materials, open or closed cell flexible foams such as polymeric foam materials, e.g. Flexible Polyurethane Foams (FPF) or flexible PVC foams optionally provided from polyethylene material. The flexible elastomer materials may be highly resilient, i.e. they can return to their original volume after being deformed, especially in a direction substantially perpendicular to the layer surfaces. They may have a high flex fatigue, i.e. their firmness is maintained, even after repeated flexing the foam. The resilience of the flexible elastomer material will cause the patch antenna to recover to its original thickness, i.e. the patch element and the ground plane may return to their original shape after being physical distorted by a distorting force, such as an impact or compression force

The patch antenna may be very flexible and suitable for integration into protective garments. Unlike conventional rigid antennas, this antenna will not disturb the movements of the wearer and still provide proper transmission or reception of the signal when partially bent. Furthermore, the antenna patch may be fully merged with an elastic dielectric material, such as a flexible foam material. Hence it would not contain protruding parts. The functionality of the elastic dielectric layer, such as a foamed material, may provide resistance to high temperatures, may provide shock-absorption, and/or may make the antenna

water-repellent and washable. The excellent electromagnetic properties of the elastic dielectric layer, such as a foamed material, may allow the elastic dielectric layer to be used as the dielectric layer of the patch antenna. In particular in case the elastomer material comprises air- or gas-containing cells, i.e. they have a cellular structure, such flexible elastomer materials may have a permittivity quite close to the permittivity of air, thereby providing a patch antenna with very high efficiency. Moreover, the flexible elastomer material may regain its original form after being exposed to compression, so that the patch antenna characteristics remain stable in time after compression, e.g. by impact. The flexible materials flexible material, e.g. of an elastomer, textile, such as non-woven, woven, knitted material may also easily be tailored both in thickness and dimension. The "tailorability" of a flexible material considerably enlarges the flexibility in antenna design.

According to one possible way to provide broadband characteristics to the antenna, the length and width of the antenna patch may be chosen slightly different from each other. Together with a suitable choice of the aperture parameters, two orthogonal modes at slightly different resonant frequencies may be excited. This results in an increased overall bandwidth of the patch antenna, e.g. a bandwidth being 1.3% but optionally 10 % or more of the central resonance frequency in planar state.

The bandwidth in bent state may be at least 1.3% of the central resonant frequency in bent state.

Furthermore, excitation of two orthogonal polarised modes may be obtained by placing the feeding point of the antenna on a diagonal of the patch element. This results in a circularly polarized antenna.

The term 'truncated substantially rectangular shape' is to be understood as a substantially rectangular shape of which the four corners are replaced by a side, this side being usually small with respect to the sides of the rectangular shape. A convex octagonal shape is thereby obtained, having four main sides being part of the four sides of the rectangle, and four truncate sides, obtained by cutting off the corners of the rectangle.

The lengths of the main sides are significantly larger than the lengths of the truncate sides.

A further embodiment of the patch antenna has four main sides being part

of the four sides of the rectangle, and two truncate sides, obtained by cutting off diametrically opposite corners of the rectangle.

Other embodiments are circular in shape with notches or may have other polygonal forms. The patch element, also referred to as antenna plane, may be shaped by means of field simulations in order to obtain high antenna performance over a pre-defined frequency band. Such pre-defined frequency band may be e.g. an ISM band or a GPS-band.

By means of the multimode technique, a return loss |S1 1 1 less than 1 OdB may be obtained over a broader band, thus providing a broader bandwidth. In the meantime, near to circular polarization may be obtained, thereby avoiding polarization alignment between transmitting and receiving antenna. By use of the flexible material, flexible material, e.g. of an elastomer, textile, such as non- woven, woven, knitted material, and a properly designed patch element, power gains of 8dBi are obtained.

The presented antenna topologies can be implemented on different types of foams with different thicknesses, chosen within an appropriate range (as an example, but not limited to, a range of 1 mm to 5 mm), provided that the electrical characteristics of the foam are selected, e.g. by selecting a dielectric constant of the dielectric layer between 1.0 and 3. All the different dimensions of the antenna plane and the location of the feed point may be optimised using a commercial full- wave field simulator, such as e.g. Agilent ADS-Momentum or CST Microwave Studio, in order to make the antenna resonate in the required frequency band and in order to provide adequate matching of the antenna impedance to the impedance of the feed section.

According to some embodiments of the present invention, the ground plane may be a conductive textile fabric.

According to some embodiments of the present invention, the patch element may be a conductive textile fabric. The conductive textile fabric which is used to provide the patch element and the ground plane may be a woven, knitted or non-woven fabric. The fibers used to provide the conductive textile fabric may be natural or man-made fibers, e.g. polymer fibers, which fibers are coated with an electrically conductive coating such as copper, aluminium, silver or gold. As an alternative, a textile fabric made

from such natural or man-made fibers may be provided with an electrically conductive coating such as copper, tin, aluminium, silver or gold. Alternatively, the fibers may be provided from intrinsically electrically conductive material such as silver, gold, copper or tin, and alike. The flexible patch element and the flexible ground plane may be provided to a surface of the dielectric layer by any suitable adhesive such as a glue or an adhesive layer.

Another alternative is the provision of a flexible patch element and/or a flexible ground plane by electrically conductive ink, e.g. applied by using a printing technique, e.g. screen-printing technique.

The conductivity of the flexible patch element and the ground plane may be tuned in order to obtain a proper bandwidth and a proper antenna efficiency for emitting and receiving signals.

According to some embodiments of the present invention, the antenna further may comprise at least one coupling means for electrically coupling the antenna to an electrically signal carrying device, the at least one coupling means being a coaxial feed or a via.

The coupling means may be a coaxial feed or a via. The use of a via allows integration of a transceiver module directly under the antenna. The exact position of the feeding point of the antenna is to be determined during the design process of the antenna. The position may be different for different thicknesses and/or different dielectric constant of the dielectric layer. Optimising of the positioning of the feeding points, as well as the values of parameters such as thickness, dimension of the patch antenna, the dielectric constants and alike may be done using computer programs-based design processes.

Alternatively the antenna may be an aperture-coupled antenna. According to some embodiments of the present invention, the patch antenna further may comprise at least one coupling means for electromagnetically coupling the antenna to an electric signal carrying device. The at least one coupling means may be an aperture coupled feed section.

According to some embodiments of the present invention, the antenna may have a -1 OdB bandwidth of at least 3.40% in planar state.

The patch antenna may be low profile and may have a dielectric layer that

provides robustness for the antenna towards e.g. bending. E.g. for an antenna operating in the 2.45GHz ISM band, e.g. in a frequency range of 2.4 GHz to 2.4835 GHz) a -1 OdB relative impedance bandwidth of at least 3.40% both in planar and bent state and for an antenna operating in the 1575.42 MHz GPS L1 band, e.g. in a frequency range 1565.19 MHz to 1585,65 MHz, a -1 OdB bandwidth of at least 1.30% both in planar and bent state and an axial ratio (defined as the ratio between the amplitude of the orthogonal components composing the circularly polarized field) of less than 3 dB is required.

The patch antenna according to embodiments of the first aspect of the present invention, and in particular the foamed material being part of the patch antenna, may be further made heat resistant and/or flame retardant by adding appropriate additives such as flame retarding materials e.g. aluminium trihydrate. This has the advantage that the patch antenna can be integrated in garments which may be subjected to fire or extreme heat, such as military garments or fire fighters' suits and alike.

The patch antenna according to the first aspect of the present invention, and in particular the dielectric material such as a flexible material, e.g. a foamed material, an elastomer, textile, such as non-woven, woven, knitted material being part of the patch antenna, may be further made hydrophobic by providing additives in the material, or by applying a coating to the material, increasing the contact angle between water and the surface of the material. This has the effect that humidity, such as water, rain or even sweat when the antenna is part of a garment, does not affect the dielectric constant of the components of the patch antenna, in particular the dielectric layer. It is understood that the patch antenna may further be provided with appropriate additional elements such as a textile fabric or foam layers for covering the ground plane and the patch element, both to visually hide the presence of the antenna as well as to prevent direct contact of the patch antenna with objects. The textile fabric or foam layer for covering the ground plane and the patch element may advantageously be an electrically insulating textile fabric for preventing the ground plane and the patch element to be in electrical contact with external objects, foreign to the patch antenna. Alternatively the ground plane, dielectric layer and the patch element may be encapsulated by means of a protective material such as a foam layer of electrically insulating material.

According to some embodiments of the present invention, the patch antenna may be suitable as emitter and receiver in mobile telecommunication applications.

According to a second aspect of the present invention, a textile product is provided. The textile product may comprise at least one flexible patch antenna according to embodiments of the first aspect of the present invention.

According to a second aspect of the present invention, a textile product may comprise at least one patch antenna, the patch antenna comprising a first dielectric layer of a flexible material, e.g. elastomer, textile, such as non-woven, woven, knitted material which is preferably hydrophobic or is made hydrophobic by means of a coating. The pore size and the surface tension of the foamed elastomer, textile, such as non-woven, woven, knitted material is preferably such as to minimize moisture absorption by the dielectric layers.

The patch element is preferably aperture coupled to a feed or coaxial coupled. The antenna preferably has radiating edges. The antenna preferably is multimodal. The antenna preferably receives/transmits non-liearly polarised electromagnetic radiation. The patch element is preferably mounted above a flexible ground plane.

The antenna has a central resonant frequency in planar state (fcp) and has a -1 OdB bandwidth in planar state of at least 1.30% of the central resonant frequency in planar state (fcp)., the first dielectric layer having a first surface and a second surface, a first flexible patch element being mounted contiguous to the first surface of the first dielectric layer, a flexible ground plane being mounted contiguous to the second surface of the first dielectric layer, wherein the antenna has a central resonant frequency in planar state (fcp) and has a -1 OdB bandwidth in planar state of at least 1.30% of the central resonant frequency in planar state

(fcp).

According to embodiments of the present invention, the at least one antenna may have a central resonant frequency in bent state (fcb), the central resonant frequency in bent state falling within the -1 OdB bandwidth in planar state. According to embodiments of the present invention, the at least one antenna may have a central resonant frequency in bent state (fcb) and has a 1 OdB bandwidth in bent state of at least 1.30% of the central resonant frequency in bent state (fcb).

Textile products may be garments for daily wear or professional garments such as protective clothing or fire fighter garments, military battle dresses, canvasses, dashboards of cars and alike or mattresses. When the patch antenna is integrated into a garment, best transmission may be achieved if the antenna is integrated into the sleeve or the shoulder pad. Reception will be improved when two (or even more antennas) are combined into the garment. Furthermore, the ground plane may be oriented towards the body of the person wearing the garment, thereby reflecting the radiated antenna power away from the body and shielding the person from the electromagnetic radiation. Next to being the substrate for the antenna, the foam may also have an additional function in the garment such as for protecting body parts such as shoulders, knees and elbows. Therefore, this new patch antenna can be provided in at least all these different areas of the body, thereby providing both the antenna function, and fulfilling a protective function. The patch antenna according to the first aspect of the present invention is suitable to be integrated in garments to be worn in severe circumstances, such as in fire-fighters suits, rescue workers suits and alike. Integration of wireless communications tools in all kind of protective clothing requires lightweight and flexible textile antennas invisible and unobtrusive to the wearer, as these antennas may not disturb their movements in critical situations. As an example, the antennas may be integrated in places of the protective suite which is unlikely to be subjected to extreme bending, e.g. shoulder parts, back part or parts conversing the upper leg.

Integrating the patch antennas into a garment can be done by attaching it to one of the garment textile layers or by putting it between two layers if the garment consists of more than one layer. This can be done since covering the antenna with extra textile layers has no or only a limited influence on the performance of the antenna.

The patch antennas according to the first aspect of the present invention may be used in furniture and interior components of e.g. automobiles. The possibility of integrating textile antennas in a non-obtrusive way reveals a variety of applications.

The antenna may be deployed as part of a multi-antenna system. One potential application consists of exploiting antenna diversity by placing two or

more antennas distributed over the garment to be worn on a body. When applying a single antenna solution on e.g. a human body, the signal is blocked by the ground plane and/or the body in the lower hemisphere of the antenna. By deploying two or more of the antennas according to embodiments of the present invention, where antennas point in different, preferably opposite, directions when worn on a body, a more robust communication link is created with much smaller probability of signal blockage.

When used in garments or clothing, the materials the antenna may be made of can be chosen as such that the whole textile product, comprising one or more such antennas, is washable.

Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features from the independent claims and with features from other dependent claims as appropriate and not merely as explicitly set out in the claims.

Although there has been constant improvement, change and evolution of devices in this field, the present concepts are believed to represent substantial new and novel improvements, including departures from prior practices, resulting in the provision of more efficient, stable and reliable devices of this nature. The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.

Brief description of the drawings

Figure 1 and Figure 2 schematically show a patch antenna according to an embodiment of the first aspect of the present invention.

Figure 3 is a schematic view of a garment comprising patch antennas according to an embodiment of the first aspect of the present invention.

Figure 4, 5, 6, 7, 8, 9 and 10 schematically show alternative patch antenna according to embodiments of the first aspect of the present invention.

Figures 1 1 and 12 schematically show further alternative patch antennas

according to embodiments of the present invention.

Figs. 13A-D show results obtained with the antenna of Fig. 2.

In the different figures, the same reference signs refer to the same or analogous elements.

Description of illustrative embodiments

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.

It is to be noticed that the term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices

consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

Similarly, it is to be noticed that the term "coupled", also used in the claims, should not be interpreted as being restricted to direct connections only. The terms "coupled" and "connected", along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms of each other. Thus, the scope of the expression "a device A coupled to a device B" should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means. "Coupled" may mean that two or more elements are either in direct physical or electrical contact, or that two or more elements are not in direct contact with each other but yet still co-operate or interact with each other.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but

not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Furthermore, an element described herein of an apparatus embodiment is an example of a means for carrying out the function performed by the element for the purpose of carrying out the invention.

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

The following terms are provided solely to aid in the understanding of the invention.

Under "flexible" is understood a material that can be bent around a cylinder with a radius (of curvature) of minimal 30 mm and is able to recover to its original planar shape after bending without the material being damaged.

The "hardness" of a material is expressed as the force required to compress a predefined volume of the material to 40% of its original shape on the fourth compression cycle of a number of consecutive compression cycles. The unit is kPa.

The "compression deformation" of the material is expressed by the

Compression Set, which determines the ability of an elastomeric material to maintain elastic properties after prolonged compressive stress for a given time and a given temperature (e.g. for 72 h at 23 ⁰ C). The Compression set is the difference between initial thickness (Do) and the final thickness (Dr) of the test piece or test specimen, after compression for give time (e.g. 72h) at given temperature (e.g. 23 ⁰ C) and after a given the test specimen or test piece a recovery time (e.g. 30 min), the difference being referred to the initial thickness.

The Compression set is thus 100 ^* (Do-Dr)/Do.

A layer being "resilient" is to be understood as being able to immediately recover completely or substantially to its original shape and/or volume after being deformed in a direction substantially perpendicular to the layer surfaces. The

principle of measurement consists in dropping a steel ball on to a test specimen from a specified height and measuring the height of rebound.

A dielectric material has the following properties: polarization effects in the material dominate electric conductivity and magnetization effects. In others terms, it can be stated that dielectric materials are insulators or very bad conductors.

Sheet resistance R _s (ω per square) of a thin film is the ratio of the potential gradient parallel to the current to the product of the current density and the film thickness; in a rectangular thin film, the quotient of the resistance, measured along the length of the film, divided by the length, I, to width, w, ratio. The ratio l/w is the number of squares.

"Substantially rectangular" is to be understood as having a shape with two pairs of mutually parallel sides the pairs being mutually perpendicular, whereby the parallelism and perpendicularity may deviate from perfectly parallel or perfectly perpendicular due to production tolerances applicable in the field of textile production.

The invention will now be described by a detailed description of several embodiments of the invention. It is clear that other embodiments of the invention can be configured according to the knowledge of persons skilled in the art without departing from the true spirit or technical teaching of the invention, the invention being limited only by the terms of the appended claims.

Two patch antennas according to embodiments of the first aspect of the present invention are shown in Figure 1 and Figure 2. The flexible patch antenna 100 in Figure 1 comprises a patch element 1 10, a flexible dielectric layer 120 having a first surface 121 providing the top side of the dielectric layer 120, and a second surface 122 providing the bottom side of the dielectric layer, and a ground plane 130. The patch element 110 is mounted contiguous to the first surface 121 of the first dielectric layer 120. The ground plane 130 is mounted contiguous to the second surface 122 of the dielectric layer 120.

The patch element 1 10 is an electrically conductive fabric. Suitable materials are e.g. woven nylon fabrics plated with a layer of copper and/or tin, known as Flectron ^® or Shieldit™ Super from Less EMF Inc., the invention not being limited thereto. These electroconductive textiles may have a sheet resistance of less than 0.1 Ohm/sq.

The dielectric layer 120 is a flexible foam material having a density of 187

kg/m ³ , a hardness of 80 kPa, a resilience of 15% and a thickness of 3.94 mm. The flexible foam materials have a dielectric constant of 1.46 and a dielectric loss tangent of 0.0012. The foam is closed cell foam. .

The ground plane is an electrically conductive fabric, provided out of the same material as the flexible patch element e.g. a woven nylon fabric plated with a layer of copper and/or tin, known as Flectron ^® or Shieldit™ Super from Less EMF Inc.

Turning to the dielectric layer, the elastomeric material may be a flexible polymeric material or a flexible polymeric foam material, alternatively be an open or closed cell foam, e.g. a polyurethane foam or a polyethylene foam.

The used flexible polymeric foam material may have a density less than 100% of the density of the initial material. Alternatively the flexible polymeric foam material may have a density within a range of 50% to 99% of the initial density. Still according to further alternatives, the flexible polymeric foam material may have a density between 7% and 50% of the initial density. The mechanical properties of the elastomer material may be chosen in function of the specific intended use of the patch antenna. As an example, a hardness in the range of more than 5 kPa may optionally be used. The compression deformation of the elastomer material, expressed as the compression set, may optionally not be more than 40%. Further improvements can be obtained if the compression set if not more than 30% or 20%. The resilience of the elastomer material may optionally be more than 14%. A variety of suitable foams is shown in Table 2 at the end of this text.

Optionally additives may be added to modify the fire resistance, water- repellence and other properties of the flexible polymeric foam material.

The patch element 110 may have a so-called "rectangular ring" shape, obtained by a patch element with a substantially rectangular shape and provided with one aperture 140.

The substantially rectangular shape has a first pair of parallel sides 1 1 1 having a length L1 and a second pair of parallel sides 1 12 having a length L2. In this particular example, L1 is 44mm whereas L2 is 48mm.

The aperture 140 is also substantially rectangular in shape, which shape is defined by a third pair of parallel sides 141 having a length L3 and a fourth pair of parallel sides 142 having a length L4. In this particular example, L3 is 7mm

whereas l_4 is 6mm. The aperture and patch, both with a substantially rectangular shape, are concentrically aligned with a central point 150. The first and third pair of sides are parallel to each other and the second and fourth pair of sides are parallel to each other. The patch antenna is provided with one connector 160, being a coaxial feed or a coaxial cable connector. The signal conducting line 162 is coupled to the patch element 110, whereas the mantle 161 of the coaxial feed is electrically coupled to the ground plane 130. The feeding point 170 where the signal conducting line 162 and the patch element 110 are connected, is provided on a first distance 171 form the central point 150 in a direction parallel to the second sides 1 12, and on a second distance 172 in a direction parallel to the first sides 11 1. In this embodiment, first distance 171 is 9.5mm and second distance is 7.5mm. The feeding point is optionally positioned coinciding with one of the diagonals of the substantially rectangular shape. The patch element 1 10, the dielectric layer 120 and the ground plane 130 are mechanically coupled to each other by an adhesive layer.

It is understood that for other combinations of electro-conductive textile fabrics (providing the ground plane and/or the patch element) and a dielectric layer, other possible methods to mechanically couple the surfaces of the electro- conductive textile fabrics and a dielectric layer may be used, such as calendaring, gluing (e.g. powder gluing), lamination such as flame lamination, or any other suitable binding technique.

The patch antenna is preferably aperture coupled to a feed or coaxial coupled. The antenna preferably has radiating edges. The antenna preferably is multimodal. The antenna preferably receives/transmits non-linearly polarised electromagnetic radiation. The patch element is preferably mounted above a flexible ground plane.

The antenna has a central resonant frequency in planar state (fcp) and has a -1 OdB bandwidth in planar state of at least 1.30% of the central resonant frequency in planar state (fcp). The patch antenna 100 is designed to send and receive signals within the range of e.g. 2.4 to 2.4835 GHz. The central frequency is 2.45 GHz. In order to make the antenna performance insensitive to bending, the bandwidth of the patch antenna 100 is more than 250 MHz, in other terms more than 10% of the central frequency, when the patch antenna 100 is flat as shown in Figure 1. When the

patch antenna is bent about an axis 180 parallel to the plane of the patch antenna, the frequency band will shift. According to the present invention, it was found that the frequency range for which the antenna is designed to work, still is within the actual frequency band of the antenna. The patch antenna may be bent up to a radius of curvature of 30 mm. Upon bending, the central resonant frequency in bent state may remain in the bandwidth of the antenna in planar state. The bandwidth of the antenna when bent to a radius of 30mm measured at the ground plane, is still more than 1.3%.

The flexible patch antenna 200 in Figure 2 comprises a patch element 210, a flexible dielectric layer 220, having a first surface 221 and a second surface

222, and a flexible ground plane 230. The patch element 210 is mechanically coupled contiguously to the first surface 221 of the dielectric layer 220 and the ground plane 230 is mechanically coupled contiguously to the second surface of the dielectric layer 220. The patch antenna is preferably aperture coupled to a feed or coaxial coupled. The antenna preferably has radiating edges. The antenna preferably is multimodal. The antenna preferably receives/transmits non- linearly polarised electromagnetic radiation. The patch element is preferably mounted above a flexible ground plane.

In the example shown in Figure 2, the patch element consists of the same material as the patch element 1 10 of the patch antenna 100 of Figure 1. The ground plane 230 consists of the same material as the ground plane 130 of the patch antenna 100 of Figure 1.

The dielectric layer 220 consists of identical flexible foam material as used for to the flexible dielectric layer 120 of the patch antenna 100 of Figure 1. The flexible dielectric layer 220 has a thickness 223 of 3.94 mm.

The patch element 210 has the shape of a truncated rectangle, obtained by a patch element with a substantially rectangular shape, for which at each corner 241 , 242, 243 and 244 of the rectangle a side replaces the corners. The four sides obtained by cutting off the corners of the rectangle, are referred to as four truncate sides 245, 246, 247 and 248.

The substantially rectangular shape is defined by a first pair of parallel sides 21 1 having a length L1 and a second pair of parallel sides 212 having a length L2. In this particular embodiment, L1 is 50mm whereas L2 is 46mm.

Each side of the first pair of parallel sides 21 1 is truncated at both its

corners by a truncating length t1 , in this particular embodiment being 8mm. Each side of the second pair of parallel sides 212 is truncated at both its corners by a truncating length t2, in this particular embodiment also being 8mm

The patch antenna 200 has a central point 250. The patch antenna is provided with one connector 260 being a coaxial feed or a coaxial cable connector. The signal conducting line 262 is coupled to the patch element 210, whereas the mantle 261 of the coax cable is electrically coupled to the ground plane 230. The feeding point 270 where the signal conducting line 262 and the patch element 230 are connected, is located at a first distance 271 form the central point 250 in a direction parallel to the second sides 212, and on a second distance 272 in a direction parallel to the first sides 21 1. In this embodiment, first distance 271 is 7 mm and second distance is 9mm.

The patch element 210, the dielectric layer 220 and the ground plane 230 are mechanically coupled to each other by an adhesive layer. The patch antenna 200 is designed to send and receive signals within a frequency range of e.g. 2.4 - 2.4835 GHz. In order to make the antenna performance insensitive to bending, the bandwidth of the patch antenna 200 is 210 MHz when the patch antenna 200 is flat as shown in Figure 2. When the patch antenna is bent over a cylinder with a radius of minimal 30 mm (which is representative for a human arm) about an axis 280 parallel to the plane of the patch antenna, the frequency band shifts, however the antenna will be able to send and receive signals within the given frequency range. The central resonant frequency in bent state was found to remain in the bandwidth of the antenna in planar state. The bandwidth of the antenna when bent to a radius of 30mm measured at the ground plane, is still more than 1.3%.

The antenna is described in detail in "A textile antenna for off-body communication integrated into protective clothing for firefighters", by Hertleer et all, Special Issue on Antennas and Propagation for Body Centric Wireless Communications, which is incorporated herein by reference in its entirety. In an alternative embodiment of the patch antenna according to Fig. 2 only two diametrically opposite corners (e.g. to form edges 246 and 248 as shown in Fig. 2) are truncated and not all four. Such an antenna may be used for GPS reception, e.g. 1.56342,1.58742 GHz range. The antenna is for use with non- linearly polarised electromagnetic radiation, e.g. right circularly polarised

electromagnetic radiation. Right Hand Circular Polarization was ensured by positioning the feed in the top right corner of the patch. The optimal antenna parameters, given the specifications for return loss and axial ratio in the frequency band of interest as optimization goals, are shown in Table I.

Table 1

The patch can be constructed using FlecTron ^® or Shieldlt ^® , electrotextiles with a sheet resistivity smaller than 0.1 ω/sq, and the ground plane using FlecTron ^® . The substrate consists of a layer of fire-resistant and water-repellent closed-cell foam with a density of 187.3 kg/m ³ , thickness h = 3.94 mm and relative dielectric permittivity ε _r = 1.56. The return loss is less than -10 db and the axial ratio (defined as the ratio between the amplitudes of the orthogonal components comprising the circularly polarised field is smaller than 3dB. The patch antenna is preferably aperture coupled to a feed or coaxial coupled. The antenna preferably has radiating edges. The antenna preferably is multimodal, e.g. edges having different lengths. The antenna preferably receives/transmits non-linearly polarised electromagnetic radiation. The patch element is mounted above a conductive flexible ground plane.

As shown in Figure 3, patch antennas 310 and 311 , which may be patch antennas similar to the patch antennas 100 or 200 shown in Figure 1 or Figure 2, can be integrated in a textile product, in this example in a suit 300 of a fireman.

The provision of a plurality of patch antennas, such as two antennas 310 and 31 1 in this embodiment, which direction 312 respectively 313 of the main lobe of the antenna in different, optionally opposite directions when worn on a person, has the advantage that a more robust communication link may be

created, with much smaller probability of signal blockage.

The patch antennas 310 and 31 1 are made heat resistant and/or flame retardant by applying a suitable flame retarding coating, by impregnation with flame retarding agents, or by using flame retarding additives in the elastomer material of the dielectric layer.

Similarly, the patch antennas 310 and 31 1 are made hydrophobic by applying a suitable water repellent coating, by using additives in the elastomer material of the dielectric layer rendering the material more hydrophobic, or by impregnating the elastomer material with any suitable material such as bitumen. The patch antennas 310 and 31 1 are provided with appropriate additional elements such as a textile fabric or foam layers covering the ground plane and the patch element of the patch antennas.

As shown in the detail in Figure 3, the patch antenna, in this detail e.g. patch antenna 310, is provided between liner 320 and insulating layer 321. The patch antenna 310 is provided in a fixed position in between these layers, e.g. by laminating or mechanically coupling the patch antenna to one or both these layers. At the outer side of the garment, a water repellent or waterproof layer 322 and an outer protective layer or outer shell layer 323 is provided.

Figure 4 shows an alternative patch antenna 400 according to an embodiment of the first aspect of the present invention. The flexible patch antenna 400 in Figure 4 comprises a patch element 410, a flexible dielectric layer 420, and a ground plane 430. The patch element 410 is mounted contiguous to a first surface of the first dielectric layer 420. The ground plane 430 is mounted contiguous to the second surface of the dielectric layer 420. The patch element 410 has an elliptic, non circular shape, which shape is characterised by a major axis D2 and a minor axis D1 , which D2 differs from D1. The difference between D1 and D2 can be defined during designing of the patch element, e.g. using suitable design programs. The patch antenna is preferably aperture coupled to a feed or coaxial coupled. The antenna preferably has radiating edges. The antenna preferably is multimodal. The antenna preferably receives/transmits non- linearly polarised electromagnetic radiation. The patch element is preferably mounted above a flexible ground plane.

The exemplary patch antenna furthermore is provided with one connector 460 being a coaxial fed or a coaxial cable connector. The signal conducting line

462 is coupled to the patch element 410, whereas the mantle 461 of the coax cable is electrically coupled to the ground plane 430. The feeding point 470 where the signal conducting line 462 and the patch element 470 are connected, is located substantially on the diagonal of the imaginary rectangle having a first side D1 and a second side D2 encompassing the elliptical shape, which diagonals cross at the centre 450 of the patch element 410.

Figure 5 shows an alternative patch antenna 500 according to an embodiment of the first aspect of the present invention. The flexible patch antenna 500 in Figure 5 comprises a patch element 510, a flexible dielectric layer 520, and a ground plane 530. The patch element 510 is mounted contiguous to a first surface of the first dielectric layer 520. The ground plane 530 is mounted contiguous to the second surface of the dielectric layer 520. The patch element 510 has triangular shape. The patch antenna is provided with one connector 560 being a coaxial fed or a coaxial cable connector. The signal conducting line 562 is coupled to the patch element 510, whereas the mantle 561 of the coax cable is electrically coupled to the ground plane 530. The patch antenna is preferably aperture coupled to a feed or coaxial coupled. The antenna preferably has radiating edges. The antenna preferably is multimodal. The antenna preferably receives/transmits non-linearly polarised electromagnetic radiation. The patch element is preferably mounted above a flexible ground plane.

Figure 6 shows an alternative patch antenna 600 according to the first another embodiment of aspect of the present invention. The flexible patch antenna 600 in Figure 6 comprises a patch element 610, a flexible dielectric layer 620, and a ground plane 630. The patch element 610 is mounted contiguous to a first surface of the first dielectric layer 620. The ground plane 630 is mounted contiguous to the second surface of the dielectric layer 620. The patch element 610 has a rectangular shape. The patch antenna is provided with one connector 560 being a coaxial fed or a coaxial cable connector. The signal conducting line 562 is coupled to the patch element 510, whereas the mantle 561 of the coax cable is electrically coupled to the ground plane 530. The patch antenna further comprises a plurality, in this particular case four, additional patches 690, which are rectangular and each one located adjacent to, but not in electrical contact with, one of the four sides of the first patch element 610. The four additional patches 690 are parasitic radiators. The patch antenna is preferably aperture

coupled to a feed or coaxial coupled. The antenna preferably has radiating edges. The antenna preferably is multimodal. The antenna preferably receives/transmits non-linearly polarised electromagnetic radiation. The patch element is preferably mounted above a flexible ground plane. Figure 7 shows an alternative patch antenna 700 according to a further embodiment of the first aspect of the present invention. The flexible patch antenna 700 in Figure 7 comprises a patch element 710, a flexible dielectric layer 720, and a ground plane 730. The patch element 710 is mounted contiguous to a first surface of the first dielectric layer 720. The ground plane 730 is mounted contiguous to the second surface of the dielectric layer 720. The patch element 710 has a rectangular shape. The patch antenna is provided with one connector 760 being a coaxial fed or a coaxial cable connector. The signal conducting line 762 is coupled to the patch element 710, whereas the mantle 761 of the coax cable is electrically coupled to the ground plane 730. The patch antenna further comprises one additional patch 790, which is an annular shape patch, which inner and outer side are substantially parallel to the sides of the rectangular first patch 710. The additional patch 790 is a parasitic radiator. The patch antenna is preferably aperture coupled to a feed or coaxial coupled. The antenna preferably has radiating edges. The antenna preferably is multimodal. The antenna preferably receives/transmits non-linearly polarised electromagnetic radiation. The patch element is preferably mounted above a flexible ground plane.

Figure 8 shows a further alternative patch antenna 800 according to an embodiment of the present invention. A patch antenna 100 as described and shown in Figure 1 is embedded in an electrically insulating foam layer 810 for preventing the antenna 100 to come into direct contact with the exterior. The antennas 200, 300, 400 500, 600, 700 and any other alternative antenna may be embedded in a foam layer 810. The patch antenna is preferably aperture coupled to a feed or coaxial coupled. The antenna preferably has radiating edges. The antenna preferably is multimodal. The antenna preferably receives/transmits non- linearly polarised electromagnetic radiation. The patch element is preferably mounted above a flexible ground plane.

A further alternative patch antenna according to an embodiment of the present invention is shown in Fig. 9. The patch antenna 900 is provided with a multi-layered structure and constituting a so-called "aperture coupled" antenna.

The patch antenna comprises a ground plane 920, being an electrically conducive flexible layer, e.g. a textile layer. On one side of this ground layer, the following flexible layers are provided (in this order starting from the ground layer 920 and in a direction away from the ground layer 920.): - a first flexible dielectric foam layer 919 having a permittivity approximating 1 ;

- a first feed line being a conductive element 918 for providing electric al signals to the antenna;

- a second flexible dielectric foam layer 917; - a "slot plane" being a flexible conductive layer 916 comprising on e or more slots, such as in this embodiment two slots 961 and 962.

- a third flexible dielectric foam layer 915;

- a second feed line being a conductive element 914 for providing electric al signals to the antenna; - a fourth flexible dielectric foam layer 913;

- a first patch element 912 made from a conductive flexible material, e.g. a conductive textile layer;

- a fifth flexible dielectric foam layer 91 1 ;

- a second patch element 910 made from a conductive flexible material, e.g. a conductive textile layer;

The feed lines 918 and 914 may have any suitable shape and path. As an example in the embodiment, both feed lines comprise two linear parts each, each linear part having increasing thickness towards the outer ends of the linear part. The feed lines may be microstrips. The antenna preferably has radiating edges. The antenna preferably is multimodal. The antenna preferably receives/transmits non-linearly polarised electromagnetic radiation. The patch element is preferably mounted above a flexible ground plane.

The apertures 961 and 962 used in the embodiment of figure 9 have a linear shape with increasing thickness towards the outer ends of the line and are perpendicularly oriented one to the other in the plane of the slot plane 916.

Shape of the feed lines, apertures, patches, foam thicknesses and permissively properties and appropriate dimensions of each part may be chosen in function of the desired frequency band for which the antenna is to be designed.

As an example, the apertures used may have the shape of a dog bone

965, may be linear 966, may be substantially linear with increasing thickness towards the outer ends of the line 967, cross-shaped 968, or may be provided in any other suitable shape. As an example, the shapes of the patch elements may be similar to the shapes as described with regard to figures 1 , 2, 4, 5, 6 or 7.

The first and second patch elements are electromagnetically coupled to the first and second line, being separated by the flexible foam layers and the slot plane. The construction of the layers as set out above operates as an aperture coupled antenna. The coupling of the signal on the feed line (or "feeds") to the patches happens electromagnetically. There is no direct "physical contact" as such. The electromagnetic energy, coming from the feed lines, is coupled through the slots and dielectric layers, being dielectric insulators, to the patches.

A further alternative patch antenna 1100 according to the present invention is shown in Figure 10. Two patch elements 1 1 10 and 1 1 1 1 , in this embodiment circular patch elements are provided.

A first dielectric layer 1 120 of a flexible elastomer material, having a first surface 1221 and a second surface 1222, is provided between a first patch element 1 1 10 and a ground plane 1 130.

The first flexible patch element 1 1 10 is mounted contiguous to the first surface 1221 of the first dielectric layer 1 120, the flexible ground plane 1 130 is mounted contiguous to the second surface 1222 of the first dielectric layer 1 120.

The antenna 1 1 10 further comprises at least a second dielectric layer 1 121 of a flexible elastomer material being mounted contiguous to the side of the first flexible patch element 1 1 10 opposite from the first dielectric layer 1 120. The antenna further comprises a second flexible patch element 1 11 1 being mounted contiguous to the surface 1321 of the second dielectric layer 1 121 at the side opposite to the first flexible patch element 1 1 10. Both patches are electromagnetically coupled.

The second flexible patch element 1 1 1 1 thus is mounted contiguous to the first surface 1321 of the second dielectric layer 1 121 , the first flexible patch element 1 110 is mounted contiguous to the second surface 1322 of the second dielectric layer 1 121. The two patches are positioned one relative to the other so the antenna has a -1 OdB bandwidth of at least 1.30% of the central resonant frequency in planar state

The first dielectric layer 1 120 has a thickness 1 123 of 0.1252mm, whereas the second dielectric layer 1 121 has a thickness 1 124 of 0.125mm.

This may e.g. be obtained by shifting the circular shapes of both patches, i.e. by positioning the central point or centre 1 151 of the second patch 1 1 1 1 eccentric, this in not coinciding with the centre 1 150 of the first patch element 1 1 10. By using a small dilatation of the centre 1 151 sidewise of the line defined by the centre 1150 and the coupling point 1 170 of the first patch element 1 1 10, e.g. a minor dilatation along a line 1 153 which makes an angle of 45° with the line 1 154 by the centre 1 150 and the coupling point 1 170, such bandwidth increase may be obtained.

As an example, the radius of the circular shape of the first patch element is 1.75cm. the first patch antenna is fed at point 1 170, which is on a distance of 1.65cm from the centre 1 150. The lateral shift is preferable less than 1.25cm.

The patch antenna 1 100 is provided with one connector 1 160 being a coaxial fed or a coaxial cable connector. The signal conducting line 1 162 is coupled to the patch element 11 10, whereas the mantle 1 161 of the coax cable is electrically coupled to the ground plane 1 130.

A further antenna embodiment is shown in Figs. 1 1 a and b. Both of these antennas are circular patch antennas comprising a circular patch element with notches 1 180, namely two notches 1180 applied diametrically opposite to each other. Other components are as described for previous antenna embodiments. The feeding point 1 170 where the signal conducting line and the patch element are connected, is provided at a distance offset from the centre of the circular element and also offset from the diameter linking the notches 1180. The patch antenna is preferably aperture coupled to a feed or coaxial coupled. The antenna preferably has radiating edges. The antenna preferably is multimodal. The antenna preferably receives/transmits non-linearly polarised electromagnetic radiation. The patch element is preferably mounted above a flexible ground plane. In Fig. 1 1 a the notches 1 180 are rectangular in shape and in Fig. 1 1 b they have rounded ends pointing towards the centre of the circular element. The antenna element has a radiating performance that generates or receives a non- linearly polarised signal. The antenna element has a radiating performance that generates or receives a multimodal signal. The signal that is transmitted or

received may be dual polarised. The patch element is preferably mounted above a flexible ground plane.

Fig. 12 shows a further embodiment of the present invention comprising a triangular antenna element and a feeding point 1 190 that is offset from the centre of the triangular element. The triangular element is truncated at one apex thus forming a trapezium, preferably an isosceles trapezoid. Other components are as described for previous antenna embodiments. The antenna element has a radiating performance that generates or receives a non-linearly polarised signal. The antenna element has a radiating performance that generates or receives a multimodal signal. The signal that is transmitted or received may be dual polarised. The antenna preferably has radiating edges. The patch element is preferably mounted above a flexible ground plane.

It is understood that for all alternative patch antennas as shown in figures 2 to 12, similar or identical dielectric layers and conductive textile fabrics can be used as described in relation to the patch antenna 100 of Fig. 1. It is understood that for the flexible patch elements and ground planes, similar layers such as layers of conductive ink may be used. Also the patch elements and dielectric layers can be mechanically coupled one to the other in identical or similar way as described in relation to patch antenna 100 of Fig. 1. Representative results for antennas according to the present invention are shown in Fig. 13 for the antenna as described with reference to Fig. 2. This antenna is designed for the ISM band. The return loss, measured with a HP8510C Network Analyzer, showed excellent agreement with the simulations (Figure 13A). With a 230 MHz bandwidth, this antenna meets the design requirements and any frequency shift due to bending, the proximity of the human body, temperature and humidity fluctuations or covering textile layers can easily be accommodated. The foam used had a compression set of 30% after being compressed by 50%, at 23 ⁰ C for 72 hours. Antenna characteristics Were examined when the thickness of the antenna substrate was reduced to 2.76 mm instead of the original 3.94 mm. It is clear from Figure 13B the entire ISM band remains covered. To measure the effect of bending, the antenna was attached to a cylinder with a radius of curvature of 40 mm, comparable with an arm. The antenna was bent in two ways: along its X-axis {bent X) and along its Y-axis {bent Y), which are defined in Figure 13A. On the one

hand, simulating the bent X situation predicts an increase of the return loss to -8 dB in part of the ISM band, since both resonance frequencies decrease and since the highest resonant frequency additionally shifts to the right (Figure 13C). The measurement exceeded this expectation with a maximum of -10 dB in return loss at 2.45 GHz. For the bent Vsituation on the other hand, it is the smallest resonance frequency that shifts to a higher range, thereby merging the two frequencies. This results in an overall decrease of the return loss, but also in a smaller bandwidth. Indeed, the simulated bandwidth decreases to 183 MHz, which is nonetheless still sufficient (Figure 13D). It is understood that the patch antennas according to embodiments of the present invention may be suitable for other uses, such as for being integrated in mattresses, e.g. mattresses for hospital beds, shoe soles, military clothing and alike, or for use in the automotive industry, being integrated in dashboards, bumpers, and alike. It is to be understood that although preferred embodiments, specific constructions and configurations, as well as materials, have been discussed herein for devices according to the present invention, various changes or modifications in form and detail may be made without departing from the scope and spirit of this invention.

W

Table 2