Patent Publication Number: US-6342869-B1

Title: Antenna device and a radio communication device including an antenna device

Description:
This application claims priority from the Swedish patent applications Nos. 9900445-9 and 9904256-6, which hereby are incorporated in their entireties and for all purposes by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to an antenna device for transmitting and receiving RF waves in at least a first frequency band and comprising a support structure and at least one radiating antenna portion carried by the support structure. 
     The invention also relates to a radio communication device including such an antenna device. 
     BACKGROUND OF THE INVENTION 
     In the radio communication systems of today there is an ever increasing demand for making the user devices smaller. This is especially important when it comes to handportable terminals, e.g. portable phones a design of the handportable terminals must permit the terminals to be easily and rapidly manufactured at low costs. Still the terminals must be reliable in use and exhibit a good performance. 
     It is well known that the size of an antenna is critical for its performance, see Johnsson, Antenna Engineering Handbook, McGrawHill 1993, chapter 6. The interaction between antenna, phone body and the close-by environment, such as e.g. the user himself, will become more important than ever. 
     This puts requirements on the antenna device to be compact, versatile and to have good antenna performance. It must also be robust, stable, easy to mount, easy to connect, and arranged so as to efficiently use the available space. Interest has also been focused on antenna devices mounted inside the housing of hand-portable terminals. Thereby, protruding antenna parts are avoided. 
     The radiating properties of an antenna device for a small-sized structure, e.g. for a handportable terminal, such as a portable phone, depends heavily on the shape and size of the support structure, e.g. a printed circuit board, PCB, of the phone, and also on the phone casing. All radiation properties, such as resonance frequency, input impedance, radiation pattern, impedance, polarization, gain, bandwith, and near-field pattern are products of the antenna device itself and its interaction with the PCB and the phone casing. On top of this, objects in the close-by environment affects the radiation properties. Thus, all references to radiation properties made below are intended to be for the whole device in which the antenna is incorporated. 
     What has been stated above is true also with respect to radio communication systems used in other apparatus than portable phones, such as cordless telephones, telemetry systems, wireless data terminals, etc. Thus, even if the antenna device of the invention is described in connection with portable phones it is applicable on a broad scale in various radio communication apparatus. 
     As the rate at which new models of portable phones are presented is increasing, the time from start of the development of a new model to the start of production and marketing of the same has been drastically shortened during the last few years. Further, there is a demand for a reduction of the manufacturing costs at the same time as the technical requirements are increasing which necessitates more functions to be included in each unit. Further, the different parts and units must be manufactured to fit well into the method of production. Simple interfaces is one key feature to simplify the assembly of the final product from different parts manufactured at different places. 
     For all types of radio communication devices, the part between the antenna and the active components of the RF front-end is critical for the total performance of the radio communication device. This is because all losses that are introduced here are critical from a system point of view. On the receiver side losses that occur before the Low Noise Amplifier (LNA) degrades the sensitivity of the receiver. On the transmitter side, losses that occur after the Power Amplifier (PA) causes degradation of the transmitted power, forcing the PA to transmit at a higher output level. 
     For portable terminals with energy provided by battery power, these factors are even more critical. Reduced receiver sensitivity causes the device to perform worse in areas with low signal levels. A higher output level from the PA increases the energy consumption from the battery, thereby reducing the available active operation time. 
     Modern manufacturing methods for devices, such as portable telephones, is based on modules that are assembled in a final assembly line. This procedure requires simple and reliable interfaces between the modules. This typically implies that the interfaces have large tolerances, making them hard to specify tightly. Specifically, this means that the loss in the interface can be quite large. 
     In order to obtain improvements in these respects some new principals for designing and assembling the products are necessary. Among them, the method of installing the antenna device and at least some of the required RF components must be improved. 
     Resistive losses, for instance, can be substantially reduced by shorting the connection lines between the antenna elements and the required active analogue components, such as filters, amplifiers, etc. This can be obtained by mounting the components close to the antenna elements, and preferably on a common support structure in order to form a separate antenna module. 
     This is of specific interest for future Software Radio, SR, architectures where the function of many traditional RF parts in the terminal are included in the software controlling the signal processor. The number of analogue RF parts, especially analogue filters, are strongly reduced in the software radio architecture. The ideal SR converts the analogue signal to/from digital data as close as possible to the antenna elements. However, some components, such as the Low Noise Amplifier(s), LNA, the filters to reduce strong interfering signals and noise, the Power Amplifier(s), PA, and the duplexers to separate transmitting and receiving signals, must still be made as analogue components. Thus, it would be a great advantage if the radio communication device could be assembled from modules, for instance a complete RF module including all analogue RF parts and the antenna, and a digital module comprising the signal processor, and a simple interface therebetween. 
     In more detail a number of advantages can be obtained by such a proposed complete RF module. One is the reduction of losses mentioned above. Another is the simpler RF interface enabled by feeding a lower power from the transmitter circuitry in the digital module to the RF power amplifier in the RF modul, and by amplifying the received power before feeding it from the low noise amplifier in the RF module to the receiver circuitry in the digital module. The proposed position of the interface between an antenna module and a radio module means that losses in the interface is not critical. This reduces the requirements on the tolerances of the interface (e.g. the contact pins) so that a more favourable assembly method can be chosen. 
     A further advantage can be the simplification of the duplexer, triplexer, etc. function if more than one antenna is used, e.g. separate receiving and transmitting antennas. To implement this in an efficient way it is necessary that this function is part of a complete RF module. An additional advantage is obtained by a mechanical integration in order to utilize the volume below the antenna element as well as possible. By using the physical area of the antenna module to mount some components needed for processing of the analogue signals the total space required is reduced. This is because the positions of the components can be chosen so that they have a minimum impact on the antenna performance. It is an advantage if the interaction between different components can be controlled, both for antenna performance and for interference, intermodulation, etc. 
     Preferably, the antenna structure should conform to the exterior casing of the radio communication device. However, the most of the improvement in volume below the antenna element when going from a flat antenna element to an element adapted to the form of the casing is being obtained already when using an element arranged on a carrier having a single curvature only. 
     SUMMARY OF THE INVENTION 
     In this disclosure it is to be understood that the antenna device of the invention is operable to transmit and/or receive RF signals. Even if a term is used herein that suggests one specific signal direction it is to be appreciated that such a situation can cover that signal direction and/or its reverse. 
     A main object of the present invention is to provide an antenna device which is easy to manufacture, easy to mount and which enables an efficient use of the available space, and has good antenna performance. 
     An other object is to provide an antenna device in which internal losses due to the resistivity in connection lines have been reduced. 
     A further object of the invention is to provide an antenna device which can be formed as an easily installable antenna module also including processing capacity for analogue RF signals. 
     An additional object of the invention is to provide an improved antenna device with processing capacity for analogue RF signals which can be formed as a module which via a readily connectable interface can be connected to a signal processor of a software radio module. 
     A further object of the invention is to provide an antenna device comprising matching circuits so as to let said antenna means be connectable to a connection point having a specific, matched, impedance, for instance 50 ohm. 
     A still further object of the invention is to provide an antenna device which is designed as a built-in module. 
     Another object of the invention is to provide an antenna device which can be adapted to the shape of the casing of the radio communication device it is to be installed in. 
     These and other objects are attained by an antenna device as claimed in claims  1 - 47 . 
     Claims  31 - 47  of these claims relate to antenna devices of the kind generally named Planar Inverted F-Antennas, PIFA, modified in accordance with the present invention. The space occupied by such a modified PIFA is more effectively used since circuitry is accommodated inside the antenna. An other advantage of this design of a PIFA is that such circuitry can be placed in the immediate vicinity of the antenna feeding point, thus avoiding transmission losses. 
     According to a preferred embodiment of the invention an antenna device is provided comprising duplexer, or switch means for combining transmitting and dividing receiving frequencies, filter means for filtering transmitting and receiving frequencies, low-noise amplifier means for amplifying the receiving frequencies and, possibly, power amplifier means for power amplifying the transmission frequencies, as well as a connection device for easy connecting the signal lines to a connection point having a specific impedance, for instance 50 ohm, and further coupling the signals to RF circuitry in the radio communication device. 
     According to an other embodiment of the invention an antenna device is provided comprising means for securely holding a SIM-card and connecting said SIM-card to circuitry in the radio communication device. 
     An additional object of the invention is to provide a radio communication device comprising an antenna device manufactured to fulfill the main object of the invention mentioned above. This object is obtained by a radio communication device as claimed in claims  48  and  49 , respectively. 
     An advantage, according to one embodiment of the invention, is that the space occupied by a PIFA is more effectively used since circuitry is accommodated inside the antenna which otherwise would have to be placed in the surrounding areas. 
     An other advantage, according to one embodiment of the invention, is that circuitry essential for the effective operation of the antenna can be placed in the immediate vicinity of the antenna feeding point, thus avoiding transmission losses. The feeding point being the point inside said cavity connecting said feeding means to said feeding post. 
     Another advantage, according to one preferred embodiment of the invention, is that it is possible to achieve a matched antenna having connector means with a specific impedance, for instance 50 ohm. 
     The invention is described in greater detail below with reference to the embodiments illustrated in the appended drawings. However, it should be understood that the detailed description of specific examples, while indicating preferred embodiments of the invention, are given by way of example only, since various changes and modifications within the scope of the claims will become apparent to those skilled in the art reading this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic plan view of an embodiment of an antenna device according to the present invention. 
     FIGS. 1 a  and  b  is a sectional view and a perspective view of the antenna device of FIG. 1 a , respectively. 
     FIG. 2 is a diagrammatic plan view of an antenna device comprising a slot antenna element. 
     FIG. 3 is a diagrammatic plan view of an antenna device comprising a patch antenna element. 
     FIG. 4 is a diagrammatic perspective view of a curved antenna element in accordance with the present invention. 
     FIG. 5 is a diagrammatic block diagram of an antenna module for transmitting and receiving RF waves according to a preferred embodiment of the present invention. 
     FIG. 6 shows a diagrammatic view of an antenna device according to a further embodiment of the invention in a cross-sectional view. 
     FIG. 7 shows a diagrammatic perspective view of an antenna device according to a further embodiment of the invention; 
     FIGS. 8 and 9 show diagrammatic plan views of antenna devices according to additional embodiments of the invention where part of the top of each antenna device has been lifted away for sake of clarity. 
     FIGS. 10-13 show diagrammatic sectional side views of antenna devices according to other embodiments of the invention. 
     FIG. 14 shows a diagrammatic top view of an antenna device according to a further embodiment of the invention. 
     FIG. 15 shows a diagrammatic perspective, partly ghost view of a GPS antenna device according to an embodiment of the invention. 
     FIG. 16 shows a diagrammatic sectional side view of an additional embodiment of an antenna device according to the present invention employing a traditional hotwire feed. 
     FIG. 17 shows a diagrammatic sectional side view of a further embodiment of an antenna device according to the present invention having a smooth curve line. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference to FIG. 1, a radiating antenna element  1  on a carrier  2  included in an antenna device for transmitting and receiving RF waves is diagrammatically shown. In this embodiment the antenna element  1  is of meander form. The carrier  2  can be relatively thin and is preferably made from a dielectric polymeric sheet material. The carrier can be stiff but can also be flexible so that it can be shaped so as to closely conform to the casing of the radio communication device, for instance a portable telephone, it is to be arranged in. 
     The antenna element  1  is illustrated as a receiving antenna connected to a Low Noise Amplifier, LNA,  3 , but can just as well be a transmitting antenna. The LNA is provided with an output line  14  for amplified RF signals. 
     In accordance with the present invention the LNA is mounted very close to and on the same carrier  2  as the antenna element  1 . This means that losses in the RF signal path between the antenna element  1  and the LNA  3  are substantially reduced compared to devices in which the LNA is positioned on a Printed Circuit Board, PCB, of the radio communication device spaced from the antenna. It is advantageous to reduce these losses as losses occurring before the LNA degrades the sensitivity of the receiver. 
     In order to reduce the interaction between the antenna element  1  and the LNA  3 , or other analogue components mounted on the carrier  2  a shielding can  4  is arranged to surround the LNA at least partly. The shielding can is made of an electrically conductive material and, in accordance with the present invention, the feed line  5  of the antenna goes directly into the shielding can  4  which is mounted very close to the antenna element  1 . Thus, the shielding can  4  is functionally integrated with the antenna element  1  and will act as an actively radiating part of the antenna. FIGS. 1 a  and  b  show a sectional view and a perspective view, respectively, of the antenna device of FIG. 1 a.    
     The antenna device which forms a readily installable module can easily be fitted in the casing of a radio communication device and its output is connected to additional receiver circuitry by means of a simple interface. As the received RF signals are amplified before they are passed through the interface the design of the interface is not as critical as it is in cases where it should handle un-amplified RF signals to be fed to a LNA positioned on a PCB of the radio communication device, for instance. 
     FIG. 2 illustrates a slot antenna element  6  including a conductive sheet  7  provided with a RF radiating slot  8 . In this embodiment the antenna element operates as a transmitting antenna and RF signals are supplied from a Power Amplifier, PA,  9  which feeds the antenna element with amplified RF signals across the slot  8 . This is indicated by means of a contact point  10  between the signal feed line  11  and the conductive sheet  7  in which the slot  8  is provided. 
     The shielding can  4  surrounding the PA  9  is mounted as an integrated part directly on the antenna element  6  and in galvanic contact with the conductive sheet  7 . Thus the shielding can operates as a part of the conductive sheet  7 . 
     The PA  9  is supplied with transmitting RF signals via an input line  15  connected to transmitting circuitry of a radio communication device via a simple interface (not shown). The design of that interface is simplified because it has not to be designed for handling amplified high power RF signals. The position of the PA on the antenna element  6  and after the interface also reduces losses of the amplified signals which is important. Otherwise such losses require the PA to transmit at a higher output level. This should increase the energy consumption from the battery powering the PA and should accordingly reduce the available active operation time of the radio communication device. 
     FIG. 3 illustrates a RF transmitting antenna device corresponding to that of FIG. 2 but in which the slot antenna element has been replaced by a patch antenna element  16 . The same reference numerals as in FIG. 2 have been used on corresponding parts. The PA  9  feeds the patch  16  with RF signals via a feed post  10  which passes through an opening  17  in the patch, and down towards a ground plane (not shown). The PA  9  and the shielding can  4  are mounted directly on the patch  16  and the shielding can is galvanically connected to the patch  16 . Thus, the shielding can  4  is integrated with the patch  16  and will operate as an actively radiating part thereof. The shielding can also be formed by a part of the patch  16  itself so that a cavity is formed between the patch and a supporting carrier, not shown. In that case the PA  9  is positioned in said cavity. 
     The above mentioned antenna elements have only been shown as representing preferred examples and the invention is not limited to the use of any specific form or any specific way of feeding an antenna element. Further, only one analogue RF component or circuit has been shown to be integrated with the respective antenna element and shielded by a shielding can. However, in accordance with the present invention any or all analogue RF components of the receiving and the transmitting circuitry of a radio communication device can be mounted together with the antenna element to form an easily manufactured antenna module which is readily installable in a radio communication device. 
     FIG. 4 shows an antenna device in accordance with the present invention formed as a curved antenna module  26 . The curvature has been adopted to the design of the radio communication device in which the antenna module is intended to be arranged. The module shown in the FIG. is shaped to fit into a portable phone. The carrier can be a flexible substrate which is easily adoptable to any design of a casing. A meandering antenna element  27  is provided on the concave surface of the carrier and connected to a shielding can  28  in which one or more analogue RF components are mounted. The shielding can is connected to and functionally integrated with the antenna element. The components in the can  28  can be readily connected to the remainder circuitry of a radio communication device via a simple interface (not shown). The meander element can be replaced by any other radiating antenna element, such as a patch element or a slot element, or a combination of different kinds of antenna elements. 
     As an alternative to being provided on the concave surface of the carrier the antenna element can be provided on the convex surface as well. Further, a first portion of the radiating antenna element can be on the concave surface and a second portion can be on the convex surface. 
     The shielded analogue components or some of them can be mounted on the convex surface, preferably in recesses. Antenna elements and components on opposite sides of the carrier can be interconnected by means of connecting lines passing through holes in the carrier. 
     The carrier  26  can be excluded and the antenna element and the shielding can be provided directly on the inner surface of for instance the back part of a divided casing of a portable telephone. The antenna element can be composed of a thin electrically conductive film which can be adhered to the desired surface. 
     The shielding can has been shown as a closed box provided with openings required for connection lines. However, the box can be replaced by a shield in the form of a tunnel or the like. The walls of the shield need not be completely closed, but can be provided with openings provided the greatest dimension of the openings is substantially smaller than λ/2 of the RF frequency used. 
     FIG. 5 illustrates a preferred RF antenna module according to the present invention. The module  30  comprises separated RF transmitter (TX)  31  and RF receiver (RX)  32  sections. 
     The antenna module  30  is the high frequency (HF) part of a soft ware radio communication device (not shown) for transmitting and receiving radio waves. Thus, antenna module  30  comprising all analogue components is preferably arranged to be electrically connected, via a relatively simple interface, to a digital signal processor of the radio communication device. 
     The antenna module  30  is preferably supported on a carrier  33  which may be a flexible substrate, a MID (molded interconnection device) or a PCB. Such an antenna module PCB may either be mounted, particularly releasably mounted, together with a PCB of the radio communication device side by side in substantially the same plane or it may be attached to a dielectric supporting means mounted e.g. on the radio device PCB such that it is substantially parallel with it, but elevated therefrom. The antenna module PCB can also be substantially perpendicular to the PCB of the radio communication device, or it can have a three-dimensional form. 
     The transmitter section  31  includes an input line  34  for receiving a digital signal from a digital transmitting source of the radio communication device. The input line  34  is connected to a digital to analogue (D/A) converter  35  for converting the digital signal to an analogue signal. The converter  35  is further connected to a power amplifier (PA)  36  for amplication of the frequency converted signal. An upconverter (not shown) for upconverting the frequency of the analogue signal to the desired RF frequency can be arranged between the D/A and the PA. Power amplifier  36  is further connected to a transmitter antenna element  37 . A filter (not shown) may be arranged in the signal path before or after the power amplifier. 
     A device  38  for measuring a reflection coefficient, e.g. voltage standing wave ratio (VSWR), in the transmitter section is connected between power amplifier  36  and the transmitter antenna element  37 . 
     A switching device  39 , preferably a switching matrix of MEMS (Microelectromechanical System switches), is connected between the SWR and the transmitting antenna structure  37 , which is switchable between a plurality of (at least two) antenna configuration states, each of which is distinguished by a set of radiation related parameters, such as resonance frequency, input impedance, bandwidth, radiation pattern, gain, polarization, and near-field pattern. 
     The receiver section  32  includes a receiving antenna element  40  for receiving RF waves and for generating an RF signal in dependence thereof. The receiving antenna element  40  is switchable between a plurality of (at least two) antenna configuration states, each of which is distinguished by a set of radiation related parameters, such as resonance frequency, input impedance, bandwidth, radiation pattern, gain, polarization, and near-field pattern. A switching device  41  is arranged in proximity thereof for selectively switching the antenna element between the antenna configuration states. The switching of the antennas between a plurality of antenna configuration states is further detailed in our co-pending Swedish patent application No. 9903942-2 “An antenna device for transmitting and/or receiving RF waves”, filed on Oct. 29, 1999, which application hereby is incorporated by reference. The antenna element  40  is further connected to one or several low noise amplifiers (LNA)  42  for amplifying the received RF signal. 
     If reception diversity is used the signal outputs from the low noise amplifiers  42  are combined in a combiner  43 . The diversity combining can be of switching type, or be a weighted summation of the signals. Two or more diversity branches can be used. A downconverter (not shown) for downconverting the frequency of the signal can be connected before an analogue to digital (A/D) converter  44  for converting the received signal to a digital signal. The digital signal is output on an output line  45  to digital processing circuitry of the radio communication device. The diversity function can, alternatively, be included in the digital part. This requires separate receiver circuits for each diversity branch. 
     According to the embodiment of the invention shown in FIG. 5 the transmitter section  31  and its antenna element  37 , and the receiver section  32  and its antenna element  40  are arranged on a common carrier  33  to form an easily manufactured and readily installable antenna module. The module comprises all analogue components and is intended to be connected to a digital processor unit via a rather simple interface (not shown). 
     In order to avoid disturbances between the components of the transmitter section and the components of the receiver section, and between the components and the antenna elements, shielding cans  46  and  47  are arranged to shield the components of the respective section. The shielding cans are connected to the antenna elements as has been described earlier. 
     Each shielding can  46 ,  47  can be divided into two or more compartments by partition walls  48 ,  49  to avoid disturbances between components in each section. 
     The invention may well be used for modifications of antenna devices of the kind generally named Planar Inverted F-Antennas, PIFA, and some preferred embodiments of such modified PIFA elements are shown in the FIGS. 6-17. 
     FIG. 6 shows an antenna in a cross-sectional view according to a preferred embodiment of the invention where a PCB (Printed Circuit Board) is denoted  101 . A ground plane means  102  is located on one side of the PCB  101  and on the other side is a circuit layout  103  located. An antenna support structure  104  is coated with a conductive layer  105 . The support structure  104  is connectable to a connector means  106 . The connector means  106  may for instance consist of metallic hooks  107  with spring action to grip the support to firmly fix the support structure  104  in position and electrically couple the ground plane means  102  to the conductive coating  105 . The coupling means  106  further comprises male connector means  108  arranged for cooperating with female connector means  109  located and fixed in connection with said support structure  104 . The male connector means are connected to the circuit layout diagram  103  for further coupling to circuitry located elsewhere on the PCB  101 . 
     The support structure  104  has a cavity, or a substantially confined space  114 . Since the support structure  104  is substantially completely surrounded with a conductive coating  105 , which is coupled to a ground plane means  102 , the space  114  constitutes a Faraday cage. This space  114  is thus shielded from magnetic and electric radiation and is therefore particularly suitable for housing analogue RF circuitry  110  of the antenna device. 
     The RF circuitry  110  is connected through the female connector means  109  and the male connector means  108  to circuitry located elsewhere on the PCB  101 . A feeding line  111  is also connected to the female connector means  109 , for further connection through the male connector means  108  to circuitry (not shown) located on the PCB  101 . It is thus clear that the male and female connector means  109 ,  108  may, in their turn, have one or more individual connector means for connecting different signals. The connector means  108 ,  109  may constitute an interface between analogue circuits in the cavity and digital processor circuits elsewhere on the PCB  101 . 
     The feeding line is further connected to a feeding point  112  which is connected to a conductive feeding post  113 . The conductive feeding post  113  is extending down towards the ground plane means to constitute a capacitive coupling with said ground plane means  102 . So is a planar inverted F-antenna construed having an inner shielded space suitable for mounting analogue RF components. The shielding conductive layer is completely integrated with a radiating antenna surface. 
     FIG. 7 shows a diagrammatic perspective view of an other embodiment of the invention. A support structure  201  is shown in “look through” fashion to reveal the arrangement inside the antenna means. An interface connector means  202  firmly grips and connects the support structure  201  to a PCB  203 . A ground plane means  204  on the top side of the PCB is connected, through the coupling means  202 , to a conductive coating  205  on the support structure  201 . First, second and third connector means,  206 ,  207  and  208  are coupling first, second and third circuitry  209 ,  210  and  211  located in a cavity  212 , defined by said support structure  201 , to circuitry (not shown) located outside said cavity  212 . The cavity with its surrounding conductive coating defines a Faraday cage. 
     A feeding point  213  is connected to said second and third circuitry  210  and  211 , which divides the signal in receiving and transmitting signals. The feeding point is connected to the conductive coating  205  as is a conductive post  214 , extending downwards towards the ground plane means  204  and substantially across the complete width of the support structure  201 . The feeding point is connected to the conductive feeding post, and the conductive feeding post may be connected to the ground plane means or may define a capacitive coupling with said ground plane means. 
     FIG. 8 shows a diagrammatic view according to a further embodiment of the invention in top view where the top part has been cut away. A support structure of a dielectric material  301  has a conductive coating  302 . Circuitry  303  is connected through first and second connection means  304 ,  305 . Circuitry  303  is any analogue circuitry which is conveniently positioned inside said support structure  301 . The first and second connection means may be any means for electrically connecting one or several signals to said first and second circuitry  302  and  303 , such as twisted pair cable, stripline, micro stripline, coplanar wave guide etc. A feed line  306  is connected, at one end to coupling means (not shown) for further connection to RF circuitry and, at the other end to a feeding point  307  which is connected to a conductive post  309 , shown with a dotted circle is extending down towards a ground plane means (not shown) making a capacitive coupling with the same. 
     FIG. 9 shows a diagrammatic view according to a further embodiment of the invention in top view where the top part has been cut away. In this embodiment a feeding point  402  is connected to a duplexer  401 . The feeding point  402  is located above, and connected to, an elongated conductive post  403  indicated by dotted lines which extends down towards a ground plane means (not shown). The duplexer  401  separates transmitting and receiving RF signals and couples the receiving signal to a filter  404 , a low-noise amplifier  405  and further through interface means (not shown) to the receiving circuitry (not shown) located in a portable radio communication device (not shown). Similarly the RF transmitting signal is received from the transmitting circuitry of the radio communication device, coupled to a filter  406 , to the duplexer  401  and fed through the feeding point  402 . Possibly, also matching means might be included in the arrangement. Thus a planar inverted F-antenna is achieved, which supplies a connection with separated transmitting and receiving signals, comprising amplification for the receiving signal at the closest possible location to the receiving point of the antenna, which is matched to a 50 ohm impedance. 
     In FIG. 10, a diagrammatic sectional side view of a further embodiment according to the invention is disclosed. A support  501  is mounted on a PCB  502  having a ground plane means  503  on the surface facing the support  501  and a circuit layout  504  on the opposite surface. Said support having a conductive coating  505  on a first side, orthogonal to said ground plane means  503 , and on a second side substantially facing said ground plane means. Said conductive coating being electrically coupled to said ground plane means  503 . Said coating  505  is in electrical contact on all sides with a stiff conductive metallic sheet  506  forming an integrated part of the radiating antenna and defining together with said conductive coating a shielded space  507  having one open side  508 . Inside said space is a first circuit  509  located. A feedline  510  is feeding RF signals to a feed point  511 . Said feed point  511  is in conductive contact with a conductive post  512  extending down towards said ground plane means  503  for achieving capacitive coupling. 
     FIG. 11 shows a diagrammatic cross-sectional side view of a further embodiment according to the invention. The embodiment in FIG. 11 is somewhat similar to the embodiment shown in FIG.  10 . The main difference being that a stiff conductive metallic sheet  601  has a protruding part  602  extending substantially parallel to a ground plane means  603  at a first distance  604  from the ground plane means. Said first distance is different from a second distance  605  from a conductive coating  606  to the ground plane means  603 . By designing the planar inverted F-antenna to have surfaces substantially parallel to the ground plane means  603  but at different distances, the antenna can more precisely be tuned to different resonance frequencies for multi band operation. A post  607  is extending from the conductive coating  606  to the ground plane means  603 . 
     FIG. 12 shows a diagrammatic cross-sectional side view of an antenna according to the invention. In this embodiment a shielded space  701 , for mounting circuitry  703  and  704 , is formed in the part of the PIFA which is extending orthogonal to a ground plane means  702 . A stiff conductive metallic sheet  705  is shielding the space  701  and extending substantially parallel to the ground plane means  702 . An insulated feed line  706  is extending on the sheet  705  for feeding RF energy to a feed point  707 . 
     FIG. 13 shows a diagrammatic cross-sectional side view of a further embodiment according to the invention. A first and second feed point  801  and  802  are fed with RF signals from a first and second feed line  803  and  804 , respectively. The first and second feed line  803  and  804  may be feeding transmitting and receiving RF signals respectively, or may be feeding signals from two different systems, such as GSM and PCN, respectively. 
     FIG. 14 shows a diagrammatic cross-sectional top view of the embodiment described in connection with FIG.  13 . The same reference numerals are used in FIG. 14 as in FIG.  13 . 
     FIG. 15 shows a diagrammatic view of another embodiment according to the invention. In this embodiment a GPS antenna is formed using an almost square, but somewhat rectangular, conductive portion  1001  which is fed with an offset from the center, marked with an X,  1002 , to produce a circular polarized RF signal. A shielded cavity  1003  is formed in the support structure for mounting of analogue circuits  1004 . An edge load  1005  is present to adjust the antenna to the preferred characteristics. The load  1005  make an impedance connection between the conductive portion  1001  and a ground plane means (not shown). 
     FIG. 16 shows a diagrammatic cross-sectional view of a further embodiment according to the invention where a hotwire  1101  is forming the conductive post and is arranged for feeding RF signals to the antenna according to traditional methods. A shielded cavity  1102  is formed inside a support structure  1103  and is arranged for housing circuits  1104  in similar ways as been described earlier. 
     FIG. 17 shows a diagrammatic cross-sectional view of a preferred embodiment according to the invention where the antenna has a smooth curving to follow a contour of a portable cellular phone. A conductive portion  1201  is arranged on a support and is shielding a cavity  1202 . Circuitry (not shown) on a circuit board  1203 , having a ground plane means  1204  arranged thereupon, is coupled to analogue circuitry  1205  arranged inside said cavity through coupling means  1206  as has previously been described. 
     For manufacturing purposes, or other purposes, it could be beneficial to design the cavity as a box having a lid or a hood, or, more generally, as a box having one open side which can, at a convenient time, be covered. 
     The conductive portion or coating defining and shielding said cavity need not necessarily be tight but may instead be formed as a net or may comprise a number of holes, as long as the holes is substantially smaller than λ/4, that is, one quarter of the current wavelength. This will seal the circuitry inside the cavity from the radiation emitted from the antenna device. The cavity can also be filled with a dielectricum. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.