TECHNICAL FIELD The present invention relates to an antenna to be used together with or in portable radio equipment for different fields of use, such as for mobile telephony, satellite technology, other types of communication radio, measuring technology and video camera technology.

BACKGROUND OF THE INVENTION The antenna is an important component in portable transceiver equipment and influences the total transmission performance in wireless communication. Antennas that are larger in relation to the wavelength for which the antennas are intended can transmit and receive radio signals better in desired wave propagation directions and have a better efficiency. The use of such antennas can increase the number of simultaneous users within a base station cell for mobile telephony due to the improved radio coverage and can also extend both the connection time and the standby time of the equipment. A better antenna for receiving results in the fact that the effect of the transmitter can be reduced accordingly, this in turn implying that interference related to transmitters in apparatus that is particularly sensitive to interference, e. g. in hospitals and in aircraft, is reduced.

Practically, there exist many different types of antennas. A basic type includes the 1/4-wave antenna that comprises a protruding or projecting rod and has a high efficiency. It is e. g. used in the mobile telephones Nokia 2110 and Motorola StarTac. A very common type includes the shortened, helical 1/4-wave antenna that is molded into a polymer material and has the same length as the antenna conductor of a rod antenna. It is used in the mobile telephones Ericsson 337,338, 388,768, 788, T18, etc. and has a little lower efficiency. An alternative design, also having a little reduced efficiency, is used in the mobile telephones Nokia 5110 and 6110.

A disadvantage associated with protruding rod antennas, which is often stated, includes that they can get stuck in and make holes in a pocket of the user. This is true also for pull-out antennas such as in the mobile telephone Nokia 2110, and for helical antennas. It has been possible to solve this problem by building the antenna into the housing of the mobile telephone, such as in the mobile telephones Nokia 3210,3310 and 3330. However, these antennas are considerably less efficient than the 1/4-wave rod antenna. Thus, they function well in built-up areas but significantly worse in thinly populated areas.

Various types of solutions to these problems have been earlier proposed. For example,

according to published European patent application 0 862 277 the antenna has been built into the carrying handle of the telephone which when needed can be turned upwards. In another version, according to published International patent application WO 00/19625, the antenna can be activated by being folded outwards/upwards, either as an individual element or as an element built into the front lid of the telephone. According to U. S. patent 6,061, 579 a special so-called patch antenna can be folded out from the rear part of the telephone to be used in satellite communication. According to published Japanese patent application 10056397 the antenna can be designed as a flexible strip which when not in use is rolled up on a drum inside the telephone equipment. When it is to be used, the antenna can be pulled out from the drum up to a desired length. Pull-out antennas are also disclosed in published Japanese patent applications 08-288727 and 07-326913 and in published European patent application 0 343 847. The both last cited applications also disclose stripshaped antennas having a curved cross-section in order to give the antennas a sufficient stiffness.

Mobile telephones can be designed for communication within more than one frequency band. It puts particular demands on the antenna, which should be designed to give a good efficiency both for transmitting and receiving within all the frequency bands.

An antenna element for two frequency bands is disclosed in published International patent application WO 00/65686. The antenna is designed to have a zigzag shape and has a capacitive element connected thereto. A multiband antenna is also disclosed in U. S. patent 6,133, 879.

Multiband antennas including LC-elements are also known. Thus, in published European patent application 1 119 074 such an antenna having a rod shaped metal conductor is disclosed.

In published International patent application WO 99/03168 the antenna main conductor has a meander shape and extends along a band shaped carrier. In published International patent application WO 01/67716 the very antenna main conductor 3,4 is stripshaped and can be located on an isolating substrate.

SUMMARY OF THE INVENTION It is an object of the present invention to provide, for use with portable radio equipment, an efficient antenna that can be easily handled.

It is another object of the present invention to provide an antenna for portable radio equipment that has a good efficiency for communication within a plurality of frequency bands.

It is another object of the present invention to provide an antenna for portable radio equipment that includes an inductive and/or capacitive component, the impedance of which can be trimmed or changed in a simple way.

It is another object of the present invention to provide an antenna for portable radio

equipment that includes an LC-filter, the resonance frequency of which can be trimmed or changed in a simple way.

Using the antenna proposed herein, among other things, the disadvantages mentioned above can be eliminated. Thus, the antenna does not project or protrude from the equipment and makes no damage when the radio equipment is not used or when it for example is located in a pocket. In order to fold the antenna out into its full length the free end of the antenna can be easily detached from a simple holding device. For example, a user only has to press a button to detach the antenna. The antenna can have a length of a 1/4 wavelength, a 1/2 wavelength or be still longer, and it can be as long as or longer than the circumference of the equipment. The antenna takes a small space in its folded-in position-in the preferred embodiment it is less than 1 mm thick- this being important since otherwise antennas in modern equipments take more and more space in relation to other units.

An antenna which generally has a strip shape and for example can be the type described above that can be folded out, can include elements that are designed as microstrips or coplanar elements or dipole elements, including inductances, capacitances or resistances, which can be adapted to some desired characteristics such as gain, bandwidth and impedance matching. Hence, the structure is more advanced than a common pull-out 1/4-wave rod antenna. In the same time low costs in mass fabrication can be obtained.

Stripshaped microstrip antennas can then also generally include inductances and capacitances arranged so that the antennas with a good efficiency can be used for transmitting/receiving in different wavelength or frequency bands, such as for two or more of usually used frequencies for mobile telephony such as 450,900 and 1800 MHz.

To make such a stripshaped microstrip antenna efficient, "loading"can be used. Loading in the sense used herein adds an inductive and/or capacitive component to the antenna resulting in that in transmitting/receiving the antenna can enter a resonance state. Such loading can be made at different places at the antenna, such as its outermost portion, farthest away from the attachment point of the stripshaped antenna or from its connection point to other electronic circuits for transmitting/receiving, at the center portion of the antenna or at its lower portion, close to the antenna holder or location. Loading placed at the outermost portion works best since it in addition to providing a desired resonance also modifies the current distribution higher up at the antenna, this increasing the radiation resistance and thereby the radiation efficiency. However, loading placed at the outer end of the antenna cannot always be provided for mechanical reasons.

If the main conductor of the antenna is combined with an LC-resonance circuit, the antenna can work for two bands.

An LC-filter of parallel type connected in the antenna conductor can work as an interrupt due to the fact that, at the resonance frequency of the filter, the filter has a very large impedance.

For a resonance frequency within a high frequency band, e. g. at 1800 Mhz, the filter then works so that the antenna conductor effectively is shorter and thereby can be adapted to this frequency band. In contrast, in lower frequency bands, e. g. at 900 MHz, the entire length of the antenna conductor is effective. An efficient two bands antenna is thereby obtained. Providing more LC- filters the antenna can be adapted for more frequency bands.

Generally thus, the antenna is band-or stripshaped, e. g. includes an elongated element having a constant width and having a small thickness in relation to its width. Then, the antenna has a stripshaped, preferably flexible, carrier element of electrically isolating material that can also be dielectric and work as a dielectric in capacitors. An electrically conducting pattern in a single conducting layer is arranged on one side or surface of the carrying element. The pattern forms an antenna main conductor of type microstrip, e. g. a conductor having a constant width that works without any ground plane function. An inductive and/or capacitive component is connected at an interrupt of the path of the antenna main conductor and connects the two portions of the main conductor formed by the interrupt. A flexible carrier can be arranged at a suitable place of the carrying element and be detached therefrom. In or on the flexible carrier an electrically conducting area is provided which when the flexible carrier is mounted on the carrying element is electrically isolated from the antenna main conductor and the inductive and/or capacitive component and electrically cooperates with the component for changing the impedance thereof. The flexible carrier can include a piece of a strip having a pressure sensitive adhesive on one surface. The strip can furthermore include a conducting pattern in a layer on a surface, preferably a surface opposite the surface having the pressure sensitive adhesive, for forming the electrically conducting area.

The electrically conducting area is preferably a single, connected area and can be located underneath or above portions of the inductive and/or capacitive component.

Furthermore, the inductive and/or capacitive component can be included in an LC-filter and then comprises an inductive element connected at an adapted place in the antenna main conductor for dividing it into portions, so that the antenna works in a lower frequency band and a higher frequency band. The inductive element has two connection ends, that are connected to the respective portions of the antenna main conductor.

Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of

the methods, processes, instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS While the novel features of the invention are set forth with particularly in the appended claims, a complete understanding of the invention, both as to organization and content, and of the above and other features thereof may be gained from and the invention will be better appreciated from a consideration of the following detailed description of non-limiting embodiments presented hereinbelow with reference to the accompanying drawings, in which: - Figs. la, lb are front views of portable radio equipment having an antenna that is mounted thereon and is shown in a folded-in state and in a folded-out state respectively, - Figs. 2a, 2b are schematic cross-sectional part views of portions at the attachment point of the end of the antenna that is connected to the equipment and located at the equipment housing, including a screw or a snapping mechanism respectively, - Fig. 3 is a schematic cross-sectional view of a push-button lock for the end of the antenna that is not connected, - Fig. 4 is a perspective view of a metal carrying element of an antenna, - Fig. 5 is a cross-sectional view of a metal carrying element of an antenna, - Fig. 6 is a perspective view of a sandwich structure for an antenna in which an inductive element is integrated with a carrying element, - Fig. 7 is a cross-sectional view of a carrying element for an antenna integrated with two polymer substrate elements and a surrounding polymer protective layer, - Figs. 8a-8d are cross-sectional views of four different embodiments of microstrip, stripline and coplanar structures integrated with a carrying element of polymer for an antenna, - Figs. 9a-9d are perspective views of carrying elements of polymer having four different types of metal patterns, -Fig. 1 Oa is a plan view of a stripshaped antenna having an inductive element at one of its ends, - Fig. 1 Ob is a plan view of a stripshaped antenna having a capacitive element at its outer end, - Figs. 11 a and lib are plan views of opposite large surfaces of a stripshaped antenna intended for receiving/transmitting in two different frequency bands, - Fig. 11 c is an equivalent circuit diagram for the antenna of Figs. 11 a and 1 b, - Figs. 11 d, 11 e and 1 If are plan views and a circuit diagram respectively corresponding to Figs.

11 a, lib and lie for a stripshaped antenna intended for receiving/transmitting in three different frequency bands, -Figs. 11 g and llh are plan views similar to Fig. 11 a for alternative embodiments of an LC-

filter, -Fig. 1 li is a cross-sectional view of the antenna of Fig. 1 g, -Fig. 1 lj is a cross-sectional view of the antenna of Figs. 1 la and 1 lb, - Fig. 12a is a plan view of a stripshaped antenna including a main conductor having a meander shape, - Fig. 12b is a plan view of a stripshaped antenna intended for receiving/transmitting in two different frequency bands and including a main conductor having a meander shape, - Fig. 13a is a perspective view of an antenna dipole element of polymer, - Figs. 13b and 13c are views from the front of an apparatus housing having a antenna dipole element that is mounted thereon and is made from a steel band, in a folded-in and a folded-out state respectively, - Fig. 14a is a plan view of an antenna having an impedance matching facility, and - Figs. 14b-4d are plan views of free or detached carriers designed to give different impedance values.

DESCRIPTION OF PREFERRED EMBODIMENTS In Figs. la and lb an antenna structure 10 is shown that can be folded in or folded out or pulled out or pulled in and is mounted on portable radio equipment 20, such as a mobile telephone. One end of the antenna is attached to one side of the apparatus housing of the equipment by a holder 30 including a cable 40 for connecting to high frequency units, not shown, for receiving and transmitting, see further Figs. 2a and 2b. In Fig. 2a a holder 30 is shown including a screw 35 that extends through a hole in the antenna end and inwards, through a corresponding hole in the apparatus housing. As an alternative seen in Fig. 2b the holder 30 can instead include a narrow pocket or slot 15 in which the end of the antenna 10 that is connected to the equipment can be pushed down and be retained therein by a snapping device 70 that is also connected to the connection cable 40.

The antenna has a folded-in state in which it is located closely at the apparatus housing and connects thereto, preferably along the outside of the housing but in some cases also inside the housing. In the case where the apparatus housing has a substantially rectangular or similar shape including large front and rear surfaces, and edge surfaces that connect the large surfaces, the antenna can advantageously in a folded-in state be located along the edge surfaces, along only part of them or around all of the housing, possible in more than one full turn. The antenna can for example be located close to the top edge surfaces and also extend along the upper portions of the edge surfaces of the apparatus housing connected thereto. In a folded-in state the outermost portion of the antenna that is not connected is retained by some easily detachable device such as a

pocket or a push button lock 80 arranged on the side of the apparatus housing of the equipment according to Fig. 3. The push button lock can include a pin 90, one end 100 of which is mounted in the outermost portion of the antenna and the other end 105 of which is rounded and has a somewhat larger diameter than the rest of the pin. The outermost portion of the antenna is locked by pressing the rounded end of the pin 150 through a hole 110 having an elastic snap holder. By depressing a button 120 a lever 130 is operated that pushes the pin 90 out of the hole 110.

Thereby, the antenna is detached and is folded or turned automatically out to its full length and then takes a substantially straight state.

Generally, the antenna is designed as an elongated element, for example having a strip shape including parallel longitudinal edges. Generally, it has in its folded-out state a profile having a curved or arc shaped cross-section that gives it a sufficient stiffness to make it maintain its straight state. The cross-section can for example be a curve having a single curvature such as part of the periphery of a circle, e. g. a circle portion corresponding to a center angle between 15 and 60°, for example about 30°. Other shapes of the cross-section can obviously be used as long as they fulfill the requirement of making the antenna sufficiently stiff in its folded-out, straight state. In the case where the antenna is in its folded-in state, for example located along edge surfaces of the apparatus housing, suitably the convex surface of the profile is directed away from the housing. At the place of the antenna where a folding or bending exists the cross-section of the antenna is straight.

In a first alternative embodiment, according to Fig. 4, the carrying element 140 of the antenna is made from thin stiff metal plate, such as for example an elongated steel plate band that has parallel edges, and can be plated with copper, silver or gold. The connection end of the antenna is indicated by an arrow in the figure. An example of a cross-section of the antenna element is shown in Fig. 5. The antenna element thus has a profile that makes the antenna keep a straight state in its folded-out state. The length of the element is a 1/4, 1/2 or more of the wavelength for which the antenna is intended, in the same way as for a common rod antenna. It means that for typical mobile telephone applications of today it has a length of about 80 mm or more. The width of the element can in such cases be 6-10 mm or less whereas the thickness can be about 0.2 mm. A protective polymer layer 150 is applied to the outside of the carrying element 140 of the antenna.

In a second alternative embodiment the carrying element 140 can have a strip structure including the same profile and cross-section as described above, but combined with the element 140 capacitive, inductive or resistive elements can be provided as desired, which are located together with the carrying element. An example in which such a combined element consists of a

metallized pattern 115 on or in the polymer substrate 160 which is in turn mounted to one side of the carrying metal element 140 is shown in Fig. 6. This element can act as a pickup element so that some portion of the high frequency energy that is connected to the carrying element 140 is fed back through the pickup element to the equipment for checking and/or controlling the output power of the transmitter. Alternatively, the element can be grounded, e. g. when in a receiving state. The antenna here obtains of sandwich structure in which the pickup element can be shorter than the carrying element. Another example is seen in the view of Fig. 7 of a cross-section taken in a plane perpendicular to the longitudinal axis of the carrying element 140. In this embodiment the carrying element is centrally located, surrounded on each side by a layer 160 of isolating polymer material including a metallized pattern 155 provided thereon or therein. Outermost, the different parts of the antenna can be surrounded by a protective layer 160 as above. The different elements which are visible in the cross-sectional view can have different lengths. A connection of high frequency units can be made both to the carrying element and to one or more of the combined elements.

In a third alternative embodiment the carrying element of the antenna includes a polymer substrate 145 having a good mechanical stiffness and good high frequency characteristics, e. g. of polyamide. The profile, the cross-section and the dimensions can be supposed to be substantially the same as described above also in this case so that the antenna also here keeps itself straight in a folded-out state. By integrating the carrying polymer element 145 with different electrically conducting patterns microstrip, stripline or coplanar structures can be obtained to conduct signals to and from the active part of the antenna. Examples of corresponding cross-sections taken in a plane perpendicular to the longitudinal axis of the carrying element are shown in Figs. 8a-8d.

Thus, the microstrip structure of Fig. 8a comprises a long conductor 180 having a constant width that is directly applied to for example the surface of the carrying element 145 that is curved outwards, the conductor width typically being about 20-50 % of the width of the element. The stripline structure in Fig. 8b is similar to the microstrip structure in Fig. 8a but has an all covering metallization 182 on the concave side of the carrying element 145 which acts as a ground plane.

This structure obtains the character of a transmission line. In Fig. 8c it has been further developed by combining an additional substrate 165 having an all covering metallization 184 on the convex side with the structure of Fig. 8b. Thereby, a transmission line is obtained having the electromagnetic field well localized at the center metal conductor 180. In the coplanar case of Fig. 8d three stripshaped conductors 186 extend in parallel to and at each other on the convex side of the substrate. The conductors 186 can have different widths in relation to each other. The center conductor is the signal conductor.

Generally, the substrates and the metallic conductor patterns of the types of structures which have been mentioned above have different lengths and widths and in addition, the conductors can be designed in different ways along the substrate. It is illustrated for some different structures in Figs. 9a-9d. Arrows in the figures indicate the place of the connection ends of the antennas. Thus, the 1/4-wave rod antenna of Fig. 9a is an example of a structure having a conductor 180 of a constant width like that illustrated in Fig. 8a. In Fig. 9b a couple of rectangular, widened areas 190 located along such a conductor are illustrated. These areas act as capacitances. A conductor 180 having a constant width has, as is illustrated in Fig. 9c, been connected in parallel with two elements, a conductor 200 having a meander shape and a conductor 210 having a smaller width. These elements act as inductances. In Fig. 9b an example is illustrated in which the conductor 180 having a constant width is interrupted so that gaps are formed and so that it thereby is divided in a plurality of shorter segments 220 of the same type of conductor which can also be located in parallel and at the sides of each other. Such a structure can act as a filter due the fact that it can influence the wavelength dependent characteristics of the antenna and can be changed according to what is desired.

Generally, "loading"can be used for making a strip antenna efficient. By this is meant that an inductive and/or capacitive component, such as those illustrated in Figs. 9b and 9c, are added to the antenna, this resulting in that the antenna can come in resonance at suitably wavelengths.

Such a component providing"loading"can be located at a suitable place along the antenna, at its outermost end, somewhere at the center portion or at its inner end, i. e. close to the connection place of the antenna. The location at the outermost end is best, compare Figs. 10a and lOb, since it can give the antenna a desired resonance and also modify the current distribution within the portion of the antenna located at the outer end thereof, this increasing the radiation resistance of the antenna and hence its radiation efficiency. However, such a location cannot always be obtained for mechanical reasons.

Thus, in Fig. 10a a strip antenna is shown having inductive loading comprising a main conductor 300 of a constant width disposed on a flexible, electrically isolating carrier 301 which has a strip shape and at its outer end is connected to a narrower conductor 302 of meander shape that forms an inductive element in the same way as illustrated in Fig. 9c. In Fig. 10b an antenna having capacitive loading is illustrated. It includes, like the embodiment of Fig. 10a, a conductor 300 of a constant width but it is at its outer end terminated by a capacitive element 304 which, as in the embodiment according Fig. 9b, is designed as a plate shaped element having a rectangular shape. The rectangular shape has a suitably adapted width exceeding that of the conductor and a suitably adapted length.

Using the inductive and capacitive elements illustrated in Figs. 10a and lOb, the antenna can be made to work efficiently for a plurality of frequency bands. An LC-resonance circuit can be formed from such elements and can be placed at a suitable place of the stripshaped antenna conductor, connected in series therewith. Thus, an antenna designed for receiving in two different frequency bands is illustrated in Figs. 1 la and lib. It comprises, as has been described above, a stripshaped antenna including a carrier and conductors applied thereto. The main conductor 300 of the antenna is a metal conductor of a constant width which is applied to the polymer substrate 301, such as a strip of flexible tape and in which, at a suitable place, an LC-combination 306, also called an LC-filter herein, is connected. The LC-combination comprises an inductive element 308 of meander type, that includes a narrower conductor and is located in the middle of the combination, and capacitive part elements 310 of plate type which for example have rectangular shapes and are connected in series at the terminal ends of the inductive element, the capacitive part elements having widths larger than that of the main conductor of the antenna, as has been described above. Of course, other shapes of the capacitive part elements can be used such as <BR> <BR> circular, triangular, etc. , that when so is required have widths larger than that of the main conductor of the antenna such as is illustrated in the figures. The capacitive effect of the part elements 310 is enhanced by a conductive, connecting part area 312 that is located underneath these elements and is electrically isolated therefrom. The underlying conducting area also connects the two upper part elements to each other and comprises a single, connected area that includes two part areas. Each of these part areas is located completely underneath a corresponding overlying capacitive part element 310 and can have a shape coinciding with that of the overlying part element or be somewhat larger than and approximately similar thereto.

Furthermore, they are connected to each other by a narrower stripshaped portion which can be straight and provides the intended connection.

The LC-combination or LC-filter 306 formed in this way is in principle an LC-circuit of the common parallel type, see the equivalent circuit diagram of the antenna illustrated in Fig. l lc.

The LC-combination acts as an interrupt at the resonance frequency of the combination, for which the LC-combination has a very large impedance. If the LC-combination for example is given a resonance frequency of 1800 Mhz the portion of the antenna located between the connection end thereof and the combination acts as an antenna at this frequency whereas for lower frequencies such as 900 MHz the total length of the antenna is effective.

The capacitive areas 310 and the underlying conducting area 312 can be located on opposite sides of the carrying portion of the antenna if it is made from a suitable dielectric material, or on the same side of the carrying portion. In the latter case a suitable dielectric layer,

not shown, is provided between the areas 310 and 312.

A stripshaped antenna of the kind described above can in an analogous manner be designed for a plurality of frequency bands. Thus, the antenna illustrated in Figs. lid and 11 e is intended for transmitting/receiving in three different frequency bands, for example 450 MHz, 900 MHz and 1800 MHz. Two different LC-combinations 306,306'are provided, the first one 306 of which has a resonance frequency of 1800 MHz in the same way as for the embodiment of Figs.

11 a, lib and l lc and the second one 306'of which has a resonance frequency of 900 MHz. The two LC-combinations 306,306'are located at adapted distances from the holder and connection terminal of the antenna, the first LC-combination being located closer to the holder then the second one. Such an antenna has an equivalent circuit diagram as illustrated in Fig. 11 f.

In Figs. llg-llj two further embodiments of a LC-filter are illustrated. In these embodiments the capacitive part areas 310 at the interrupt of the main conductor 310 of the antenna have the same widths as that of the main conductor and actually form the areas thereof located at the connection to the inductor conductor 308. The capacitive connecting area 312 has in these embodiments the shape of a conductive metal strip of a constant width smaller than the width of the antenna main conductor and can be straight, as illustrated in Fig. 1 g, or have some suitable curved shape, for example a U-shape, such as is illustrated in Fig. 1 lh. It further appears from these figures and from the cross-sectional view of Fig. 1 li that the electrically conducting area 312 can be applied to a dielectric carrier 313 that can be piece of flexible tape attached on top of the antenna main conductor 300 so that the dielectric layer is located between the main conductor of the antenna and the electrically conductive, connecting area. The latter area can of course also be arranged on the bottom side of the dielectric carrier 301 for the main conductor, such as is illustrated in Figs. 11 a and lib and appears from the cross-sectional view of Fig. 1 lj.

In the cross-sectional views of Figs. lli and llj also the resulting capacitors are illustrated as element capacitors 315. The dielectric carrier 313 is advantageously provided with a pressure sensitive adhesive at one of its sides, that side to which the conducting area 312 is not applied.

Hence, the carrier can be detached from the carrying element 301 for the antenna main conductor and thereby be easily exchanged, for example for giving a different resonance frequency.

Furthermore, the carrier can also be gradually detached, from an end of the carrier and taken in the longitudinal direction of the antenna. In that way the effective surface area of the connecting capacitive area 321 can be made smaller, where this can be used for trimming the resonance frequency of the LC-filter 306.

Such a detachable carrier can also be used to change the impedance of a more"pure" impedance element. Thus, in Fig. 14a thus an antenna is illustrated for one frequency band

including an inductive element 317 having the shape of a narrow stripshaped conductor of meander shape as has been described above. Underneath or above the inductive element a strip 319 of electrically isolating/dielectric material is attached that includes an electrically conducting area 321, see Figs. 14b-14d. When the strip is attached to the antenna carrier 301 the conductive area 321 is electrically isolated from the main conductor 301 of the antenna and from the inductive element and modifies the impedance of the inductive element. By applying strips 319 having differently designed conductive areas, for example having different widths taken in the longitudinal direction of the antenna and the strip, the impedance of the inductive element 317 can be trimmed to a desired value. It is realized that the same type of attachable and detachable strip having different forms or sizes of a conductive area can be used for trimming the impedance of a capacitive element.

If the length of the antenna is insufficient for efficiently receiving/transmitting in a frequency band the stripshaped antenna conductor can be designed to have a meander or zigzag shape in order to obtain a suitable length. Thus, as is illustrated in Fig. 12a, the antenna conductor 380 having a constant width can over a major portion of the length of the antenna have such a shape that is illustrated in the part area 314. Such a meander or zigzag shape, that can also be called a"coiled"shape, can be combined with LC-combinations according to Figs. lla-llf.

Such an embodiment is illustrated in Fig. 12b, in which the LC-combination 306 is connected in series with meander portions 316,316'at its two connection sides. The conductor of the L- element in the LC-combination is significantly narrower than the antenna main conductor 300.

Furthermore, in this embodiment the antenna has a capacitive element at its outer end.

In a fourth alternative embodiment the antenna comprises a dipole including two active part elements arranged in a mirror symmetric way. A carrying element of polymer 105 having two metal conductors 180 of constant widths can in this case at its center be attached to the apparatus housing, see Fig. 13a. Fig. 13b shows a case in which the part elements comprise two separate metal strips 140. The ends of the element that are connected to the equipment are here seen to be attached to the housing of the equipment closely at each other and are directed oppositely of each other near the attachment point. Figs. 13b and 13c illustrate the antenna in its folded-in and folded-out states.

The embodiments of an antenna including different types of components obtained using different conductive layer areas, such as illustrated e. g. in Figs. 9a-12b, can obviously be used for all types of stripshaped carriers, in particular flexible ones. It is not necessary that the carrier in these cases has an inherent curved cross-section shape.

While specific embodiments of the invention have been illustrated and described herein, it

is realized that numerous additional advantages, modifications and changes will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative devices and illustrated examples shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within a true spirit and scope of the invention.