Abstract:
A device for radio communication (PH), such as for example radiophone, includes a shielding layer (RFS) which under operating conditions is between the antenna and the user. The shielding layer (RFS) reduces electromagnetic irradiation of the user. The shielding layer (RFS) may be movable in such a manner that it serves as a cover of some operational devices such as for example, the headphone, display and keyboard of the apparatus when it is not used.

Description:
This application is a continuation of prior application No. 08/507,346 filed on Aug. 15, 1995 (now U.S. Pat. No. 5,787,340). 
    
    
     TECHNICAL FIELD 
     The present invention relates to an apparatus for radio communication, such as for example a radiophone. 
     The popularity of radiophones has been rapidly increasing during the last ten years. At the same time a belief of potential health hazards related to non-ionizing radiation has been increasing. The power radiated by a radiophone is relatively low, typically few hundred milliwatts. On the other hand the antenna means of radiophones are few centimeters from the brain, the hearing organs and the organ of equilibrium. Although a direct heating effect could be left without further consideration it has been suggested that modulated radio frequency radiation induces changes in the electrical status i.e. in the ion balance of nerve cells. A continuous localized exposure to radio frequency irradiation has been suggested to weaken myelin sheets of cells and to eventually lead to an impairment of hearing capability, vertigo etc.. It has been suggested that radio frequency irradiation may stimulate extra growth among supportive cells in the nerve system, which in the worst case it has been suggested could lead to a development of malignant tumor e.g. glioma from supportive cells. Although the consequences, described above have not been scientifically verified, the uncertainty has some effects e.g. by reducing the speed of growth of the market of radiophones. 
     SUMMARY OF THE INVENTION 
     The invention avoids the drawbacks of the prior art and reduces the irradiation of the user, especially the brain and the nerve tissues. The invention and corresponding apparatus based thereon are characterized by what is not forth in the characterizing sections of the annexed claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in more detail with reference made to the accompanying drawings, in which: 
     FIG. 1 shows the main features of a radiophone of the prior art. 
     FIG. 2 shows schematically the position of a radiophone relative to the users head and lists major tissues which are penetrated by electromagnetic radiation omitted by the radiophone. 
     FIGS. 3 a - 3   d  when a radiophone of the invention. 
     FIG. 4 shows a detail of a radiophone of the invention seen from the side of the antenna. 
     FIGS. 5 a - 5   b  show construction of the shielding layer of a radiophone of the invention. 
     FIGS. 6-6 a  show another construction of the shielding layer of a radiophone of the invention. 
     FIG. 7 shows another radiophone of the invention. 
     FIGS. 8 a - 8   b  show a third radiophone of the invention. 
     FIGS. 9 a - 9   b  shows a fourth radiophone of the invention. 
     FIG. 10 shows one solution of the invention to increase the protection of the user against the irradiation from the radiophone. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows the most prominent parts of a radiophone which are visible from outside: A is an antenna, which is typically so called helix type. In most radiophones the antenna is covered with rubberlike material with carefully selected electrical properties. When the radiophone is not to be used the antenna may be positioned at least partially inside the body of the radiophone. In some devices the part which is left outside is also designed to operate as an antenna with reduced radiation efficiency and reception sensitivity. 
     The following parts are also visible: M is a microphone, P is a headphone and KB is a keyboard. 
     FIG. 2 shows schematically a position of antenna A of radiophone PH relative to brain BRAIN. The view CUT A is shown in the lower section of the figure. As shown in the figure, the power radiated by A is first penetrating a thin skin layer SKIN and thereafter a fat layer FAT. Either of these layers does not significantly attenuate or reflect electromagnetic radiation. A muscle layer MUSCLE of the head is relatively thin, therefore this layer does not markedly attenuate the penetration power. Bone and bone marrow do not significantly attenuate penetrating, radiation, although this layer is relatively thick. It has been suggested that, most of the incoming energy is absorbed by cerebrosphinal fluid CSF and brain tissue BRAIN. CSP layer is usually thin. Because antenna A is very close to brain tissue and the distance is much shorter then the wavelength of usually used electromagnetic oscillation, it has been suggested that the irradiation of brain tissue is rather significant. 
     FIG. 3 shows one solution of the invention to reduce the coupling between antenna A and tissues of user. There are guides G in the body of apparatus PH and a shielding layer RFS which slides along C. When PH is to be used, RFS is at the upper position as shown in FIG. 3 a.  RFS is between the radiating part of the antenna means and the user. When PH is not to be used, RFS is at the lower position as shown in FIG. 3 b.  In order to enforce the use of RFS, RFS is arranged to cover phone P as PH is not to be used. RFS may cover also the display D and the keyboard KB of PH, the possibility is that P is attached to RFS and it moves to the using position with the RFS. FIG. 3 c  shows the frontview of PH in the same situation as FIG. 3 a.  FIG. 3 d  shows the frontview of PH in the same situation as FIG. 3 b.    
     RFS maybe manufactured from electrically conductive plastic or plastic which is covered with a conductive layer or plastic sheet with a conductive layer inside or just metal. The conductive layer may be slitted, a mesh, or solid. The operation may be easily understood: A part of the power radiated by A is reflected by the conductive surface of RFS and the electric field is coupled via RFS to the electrical ground of PH. The coupling between the electrical ground and RFS assumes a connection at the operation frequency between the ground and RFS. RFS affects the properties of antenna means A and this effect must be taken into account in the design of the antenna means. The shielding effect of RFS improves the operation conditions of the antenna means because the loading effect of tissues is small. 
     FIG. 4, shows one embodiment of the invention for RFS. The guides G are grooves in the body of PH. RFS glides up and down along G. Obviously one may construct means e.g. flexible springs which lock RFS in the operational and resting positions. There may also be micro-switches, which enable the use of PH only when RFS is in the operational position. 
     FIG. 5 a  shows one possible construction of RFS. L 1  is a layer which has electrical characteristics different from those of layer L 2 . L 2  may be a reflective, conductive layer and L 1  is from some material which has a high dielectric constant (e.g., ceramics) and/or a high permeability (e.g. ferrite), which changes the wavelength so that the reflection from the layer L 2  is as efficient as possible. Because of this the operation conditions of the antenna means are improved and the irradiation of the user is reduced. 
     FIG. 5 b  shows an embodiment, in which RFS is constructed from material, like a composition of plastic and graphite, which absorbs energy radiated by the antenna. 
     FIG. 6 shows one embodiment of the invention which enables a reduction of the irradiation generated by apparatus already in the market. RFS is positioned over the antenna so that the antenna is fixed on the antenna support. AH and SL, the shielding part of RFS is placed between the antenna and the user. FIG. 7 shows RFS which moves guided by the hinges H in the using position. In this case RFS may form a part of the protective cover of PH. 
     FIG. 8 shows one embodiment of the invention, where RFS and A are mechanically connected with a bar or a plate CB. As A is moved to the operational position, RFS moves simultaneously to the operational position (FIG. 8 a ). FIG. 8 b  shows A and RFS in the resting position. 
     FIG. 9 a  shows a side view of PH, where A in the operational position is unconventionally directed away from the user. RFS reduces the amount of power absorbed by the user. FIG. 9 b  shows the rear view of PH. When not used, A is in the antenna holder AH, from where A is at first pulled out and then turned in the using position. 
     FIG. 10 shows an embodiment of the invention which further increases the protection of the user. The box of PH consists of at least two parts BA and BB, from which BB is electrically conductive. RFS and BB forms a solid layer which reflects the power radiated by A away from the user and prevents a direct connection between the user and the radiative parts of PH. Depending on the wavelength and the other technical features of the device BB may be connected to the electrical ground of PH. BA may be made from insulating material. The relationship between BA and BB is determined by the operational frequency, the constructions of the antenna means and the electronics. 
     There are other alternative designs of hinges H than those shown by FIG.  7 . RFS may turn sidewise or the hinges may include constructions which generate more complicated movements of RFS. 
     The above only describes a few embodiments of the invention. The invention can be subjected to a plurality of modifications within the scope of the inventional concept defined in the appended claims.