Different models of mobile stations taken together have a large number of proper- ties that do not belong to the primary properties required of a terminal device of a mobile communications network. One such property is the capability to receive ra- dio broadcast. In general, this means listening to transmissions from stations that operate in the VHF (Very High Frequency) range and use the FM (Frequency Modulation) technique. In that case, the keypad and audio part of the mobile sta- tion can be utilized, but, the RF (Radio Frequency) and IF (Intermediate Fre- quency) parts according to the transmission standard in question have to be added to the device. Especially another antenna is required, because mobile sta- tion antennas designed for the frequencies 1-2 GHz have a very poor matching on frequencies of the order of 100 MHz. At the frequency of 100 MHz the wave- length is three metres, and therefore the antenna requires a relatively large space.

The combination of a mobile station and an FM receiver in the same physical de- vice is thus known from some models in the market. Combinations like this have also been presented in the patent publications JP 5268151, JP 8331003 and CN 1206313. However, the implementation of the FM antenna has not been de- scribed in these at all. In addition, the published application FI 991440 discloses a combination of the type in question. In that application, there also appears a short and almost straight antenna wire for FM receiving, located within the battery pack of the mobile station. The antenna has not been described and it is not mentioned in the claims.

Fig. 1 shows a known arrangement for listening to radio broadcasts by a mobile station for the part of the antenna. In the figure there is seen a mobile station 100 and its accessory HS. The accessory includes a microphone M and earphones E, and it is intended to be placed on the user's head for freeing his hands during the connection. The accessory HS is coupled to a connector in the mobile station with a cord 110, which contains the conductors required for the transfer of audio sig- nals. One of these audio conductors is capacitively coupled to the FM receiver in the phone 100 and so at the same time functions as its antenna. The principle is the same that has been used for a long time in pocket radios that are listened to with earphones. The antenna is a monopole antenna, in which the receiving ele- ment preferably has the length of a quarter wave. Such an antenna conductor can naturally also be used independently, without the headset device. The drawback of an external monopole antenna is its inconvenience caused by its length.

An objective of the invention is to implement an antenna integrated in a mobile station and intended for the receiving of radio broadcasts in a new and advanta- geous manner. The antenna structure according to the invention is characterized in what is set forth in the independent claim 1. The mobile station according to the invention is characterized in what is set forth in the independent claim 10. Some preferred embodiments of the invention are set forth in the other claims.

The basic idea of the invention is the following : The FM antenna is located within the mobile station. The conductive antenna element rests on a piece of dielectric material within the casing of the mobile station. Together with the antenna ele- ment, said piece can form a separate antenna component to be fastened to the mobile station or it can be a part that belongs to the structure of the mobile station in any case. In order to decrease the size of the antenna, the antenna element is preferably a relatively dense meander conductor. There are preferably two an- tenna elements to form a dipole structure.

The invention has the advantage that the receiving of radio broadcasts by a mo- bile station does not require an external antenna with its connections. Another ad- vantage is the fact that the costs of manufacture and installation of an antenna according to the invention are relatively low.

In the following, the invention will be described in more detail. Reference will be made to the accompanying drawings, in which Fig. 1 shows an example of a known antenna structure for receiving radio broadcasts by a mobile station, Fig. 2a shows an example of an antenna structure in a mobile station accord- ing to the invention as a layout drawing, Fig. 2b shows the antenna structure according to Fig. 2a in more detail as a cross-section of the mobile station, Figs 3a, b show examples of an antenna component according to the invention, Fig. 4 shows another example of an antenna structure according to the inven- tion, Fig. 5 shows a third example of an antenna structure according to the inven- tion, Fig. 6 shows a fourth example of an antenna structure according to the inven- tion, Fig. 7a shows a fifth example of an antenna structure according to the inven- tion as a layout drawing, Fig. 7b shows the antenna structure according to Fig. 7a in more detail as a longitudinal section of the mobile station, Fig. 8 shows an example of an antenna component which is suitable for the structure shown by Figures 7a, b, and Fig. 9 shows another example of an antenna component which is suitable for the structure shown by Figures 7a, b.

Figure 1 was dealt with above in connection with the description of the prior art.

Fig. 2a shows a layout drawing of an exemplary antenna structure according to the invention in a mobile station, which is a brick-shaped phone in this example. A substantial part of the antenna structure is formed by two strip-like antenna com- ponents, which are located within the casing of the phone 200 beside its side walls. The first antenna component 210 is on the left side of the keypad as viewed from the front of the phone, and the second antenna component 220 is on the right side of the keypad. The antenna components could naturally also be upper, e. g. partly at the display. There is one conductive antenna element in each an- tenna component, and together they form a dipole antenna for the FM receiver in the device.

Fig. 2b presents an enlarged, simplified cross-section of the mobile phone 200 in Fig. 2a. It shows the casing 202 of the phone, the circuit board 203 and the key- pad 204. In addition, the side walls 201 of the plastic frame of the phone are shown of the basic structure. The antenna components 210,220 have been fas- tened to the outer surfaces of the side walls of the frame in the narrow empty space between the frame and the cover. The fastening means is based on some adhesive material spread on one side of the antenna component, for example. On the circuit board 203 there is an FM receiver circuit 250, which is connected by the first transmission conductor 212 to the antenna element 211 of the first antenna component and by the second transmission conductor 222 to the antenna element 221 of the second antenna component. A dipole antenna equipped with a trans- mission line is thus formed.

In Figures 3a, b there are more enlarged examples of an antenna component ac- cording to the invention and its receiving element, or antenna element. The shape of the components corresponds to the case of Figures 2a and 2b. Fig. 3a shows an antenna component 310, which includes an elongated, rectangular dielectric plate 315 and an antenna element 311. The antenna element is a thin strip con- ductor on the surface of a dielectric plate. The conductor 311 is meander-shaped in a way that it comprises close together portions that have almost the same length as the short side of the dielectric plate and are parallel with it. Fig. 3b shows an antenna component 320, which includes an elongated, rectangular di- electric plate 325 and an antenna element 321 on its surface. The antenna ele- ment is a thin meander-shaped conductor which comprises close together por- tions that have almost the same length as the long side of the dielectric plate 325 and are parallel with it. Both the antenna element 311 and element 321 have the electric length of about a quarter wave at the frequency of 100 MHz, i. e. approxi- mately 75 cm. When the antenna component has been installed in the mobile sta- tion, one end of the meander conductor is connected to the FM receiver in the mobile station. For this purpose, said end of the conductor has a through hole, for example, to which the end of the conductor going to the FM receiver is soldered.

Such a conductor end coming through the frame of the mobile station also func- tions as a positioning pin for the antenna component.

The dielectric plate 315,325 of the antenna component is made of flexible circuit board material or plastic film, for example.

Fig. 4 shows another example of the antenna structure according to the invention.

In the figure there is seen half of the casing 402 of a mobile station. The casing half is a united piece with an even bottom and side walls so that the structure re- sembles an open, shallow box. The box may have openings required by the struc- ture and function of the mobile station, the likes of which have not been drawn in Fig. 4. In this case, too, a substantial part of the antenna structure is formed by two strip-like antenna components 410 and 420, which are located side by side on the inner surface of one long side wall of the cover 402. There is one conductive antenna element in each antenna component, and together they form a dipole an- tenna for the FM receiver in the device. The casing 402 can be made of plastic, in which case the antenna components are of flexible circuit board, for example. The casing can also be metal, such as extruded aluminium. In this case, the dielectric part of the antenna components 410 and 420 is of special plastic, on the surface of which the antenna element has been processed using a technique such as MID (Molded Interconnect Devices).

Fig. 5 shows a third example of the antenna structure according to the invention.

In the figure there is seen a similar half of the casing of a mobile station as in Fig.

4. In this example, the material of the casing 502 is plastic which is suitable for the use of the MID technique. By this technique, the antenna element 511 has been processed directly onto the inner surface of the casing 502. The structure can also include another similar antenna element to form a dipole antenna.

Fig. 6 shows a fourth example of the antenna structure according to the invention.

In the figure there is seen an enlarged, simplified cross-section of a mobile phone 600. It includes, among other things, the casing 602, frame 601 and circuit board 603. The antenna component 610 has been fastened to a metallic shielding cover 608 of the electronic circuits on the circuit board 603. In this case, too, the con- ductive antenna element may have been processed by the MID technique onto the surface of the dielectric part of the antenna component 610.

Figures 7a, b show a fifth example of the antenna structure in a mobile station according to the invention, as a layout drawing. There is now one antenna com- ponent, and it is located inside the casing of the mobile station 700 on top of its battery 706. In Fig. 7b there is a simplified, longitudinal section of the mobile sta- tion 700 of Fig. 7a. There is seen the casing 702 of the mobile station, the circuit board 703, keypad 704, display 705 and battery 706. The antenna component 710 has been fastened on the surface of the battery in the empty space between it and the cover 702. If there is some ferromagnetic material on the battery wall, the fas- tening can be magnetic in a way that there is a thin layer of magnetic material on the surface of the antenna component on the battery side.

Fig. 8 shows enlarged an example of an antenna component which is suitable for the structure shown by Figures 7a, b. The antenna component 810 includes a rec- angular dielectric plate 815, a first 811 and a second 812 antenna element and a magnetic plate 816. The antenna elements are strip conductors on the upper sur- face of the dielectric plate, or as installed, on the surface that is on the side of the outer surface of the mobile station. They are meander-shaped in a way that they comprise close together portions that are parallel with the shorter side of the di- electric plate and almost of the same length. The antenna elements are symmetri- cal so that the ends that are to be connected to the FM receiver are located side by side approximately in the middle of one long side of the dielectric plate 815. In that case, as viewed from the receiver, a dipole antenna is formed with the first and the second antenna element as its branches.

On the lower surface of the dielectric plate 815, or as installed, on the surface that is facing the battery of the mobile station, there is a thin layer of magnetized fer- romagnetic material 816. Because of this, the antenna component 810 adheres to the wall containing ferromagnetic material and stays there without any other fas- tening arrangement. On the other hand, ferromagnetic materials have a lengthen- ing effect on the electric lengths of the antenna elements, which means a smaller size for an antenna of a certain frequency range.

Fig. 9 shows another example of an antenna component which is suitable for the structure shown by Figures 7a, b. In Fig. 9 the antenna component has been in- stalled on the upper surface of a battery 960 either using the magnetic joint men- tioned above or some other fastening technique. In this example, the whole an- tenna is a monopole antenna, because it comprises only one conductive antenna element 911. This is a strip conductor on the surface of a dielectric plate 915. The conductor 911 is meander-shaped in a way that it comprises close together por- tions that are parallel with the longer side of the dielectric plate and almost of the same length. Another difference as compared to the structure of Fig. 8 is the way in which the antenna element is connected to the FM receiver. In Fig. 8, the transmission line between the antenna and the receiver is connected e. g. by sol- dering to the adjacent conductive pads at the ends of the antenna elements. In the example of Fig. 9, there is instead a small extension in the flexible dielectric plate 915, extending to the end surface of the battery 960 where the feeding contacts 961 of the mobile station are. The antenna element 911 continues along said ex- tension to the antenna contact 913 at the end of the battery. The connector, through which the battery is connected to the mobile station, also has a contact pin at the antenna contact 913, connected to the FM receiver by a transmission conductor.

The antenna structure according to the invention can differ from the examples de- scribed in its details. For example, the element that receives radio radiation need not be regularly meander-shaped, or not meander-shaped at all, and the shapes and fastening places of the antenna components can vary. The inventive idea can be applied in different ways within the scope defined by the independent claim 1.