DK176625B1 - Handheld device with antenna means for transmitting a radio signal - Google Patents

Description

DK 176625 B1

The invention relates to a hand-carried apparatus which comprises antenna means for transmitting a radio signal.

For example, In modern mobile phone systems, the hand-held transmitting and receiving units will usually be provided with antennas having an omnidirectional radiation diagram, which gives the highest possible probability of being connected to the particular mobile phone at a given time, thus facilitating system operators' system planning. Naturally, the users of the mobile phones also want the system to have as good coverage as possible.

However, the omnidirectional radiation diagram has the disadvantage that the telephone will normally be positioned in relation to a user's head so that this is precisely where the electric field from the telephone antenna is most powerful. On the one hand, this means that there will be a certain loss of power, as part of the radiation energy 20 is deposited in the head, and on the other, there is a risk that this particular energy deposit can be harmful to health. In particular, in view of the potential health risk, there is a desire to direct the radiation away from the user's head.

25

A proposal for solving this problem is known from WO 94/22235, where a shielding element is placed between the antenna and the user's head. The shielding element is intended to absorb, block or reflect the electromagnetic radiation from the antenna. In an alternative embodiment, the display is an integral part of the antenna itself. However, this solution has the disadvantage that with the radio frequencies used, e.g. may be 900 MHz or 1.8 GHz, the longitudinal extension of the screen is of the same order of magnitude as the wavelength, which will reduce the effect of the screen, since its outer end will in some degree act as antenna itself. Furthermore, since the radiation from this solution is mainly directed washing from the user's head, the sending / receiving conditions of the telephone will be deteriorated, unless there is precisely a base station in this particular direction. Therefore, the solution is really only applicable in areas where the base stations are located so close to each other that there will always be a station sufficiently close in that direction.

Another solution is known from WO 95/24746. Here, a so-called inverted F antenna is placed on the back of the phone so that the free end of the antenna is at the end of the phone which is placed against the user's ear during use. This means that the radiation from the antenna and -15 is so mainly directed away from the user's head, and the solution therefore places the same requirements on the location of the base stations as described above.

It is also known to provide a mobile phone with two different antennas. For example, US 5,530,919 discloses e.g. an apparatus having a built-in directional antenna and a rod antenna. The directional antenna is used as the transmitting antenna and the rod antenna as the receiving antenna. Therefore, this apparatus also requires that a base station be located in the direction that the directional antenna is facing, since the apparatus can only transmit in this direction. By contrast, the rod antenna can be received from all directions.

30 EP 214 806 also describes an apparatus with a built-in directional antenna and a rod antenna. Here, both antennas are used as the receiving antenna in order to obtain receiver diversity, while only the rod antenna is used as the transmitting antenna. Thus, this device does not avoid the radiation in the user's head.

3 DK 176625 B1

It is therefore an object of the invention to provide a solution which, under poor transmission / receiving conditions, can send and receive with a quality which is similar to the normal mobile phones with omnidirectional radiation characteristics, and which at the same time exposes the user's head to the least possible radiation risk. .

This is achieved according to the invention in that the hand-held apparatus for transmitting a radio signal comprises at least two transmitting antennas having different radiation characteristics.

Hereby one or the other antenna can be used depending on the reception conditions. In this way, one can make sure that the user's head is exposed to radiation only when it is necessary for the transmit / receive conditions.

This is particularly possible when one transmitting antenna, as defined in claim 2, has an omnidirectional radiation characteristic and the other has a directional radiation characteristic. The antenna with omnidirectional radiation characteristic is then used only when necessary for the transmission / reception conditions.

In a convenient embodiment of the invention as set forth in claim 3, the omnidirectional radiation characteristic antenna is a pullout antenna, while the directional radiation characteristic antenna 30 is a patch antenna.

The outlet antenna may, as stated in claim 4, be adapted to be switched on only when it is fully or partially extended. Hereby, it is the user himself who decides whether the transmitting / receiving conditions are so bad that it is necessary to switch on the pull-out antenna.

Alternatively, as set forth in claim 5, the apparatus may comprise 5 means for switching on and off the pull-out antenna in dependence on a received signal. This can be done, for example. For example, a base station, when it is difficult to receive the signal transmitted from the apparatus, requests the apparatus to engage the pull-out antenna. Another possibility, stated in claim 6, is that the apparatus comprises means for measuring the field strength of a signal received on the patent antenna and that the pull-out antenna is adapted to be switched on only when said field strength is below a certain value, the received signal level is then used as an indicator of whether the transmitted signals are sufficiently strong towards the base station. This is possible since the device will normally send to and receive from one and the same base station.

20 In particular, in the case of mobile phones, a small and easily manageable size is given great importance, and this therefore requires that the two antennas must be able to be integrated into the device without significantly increasing its size. Since the omnidirectional antenna already exists in the design of most existing devices, that is, the directional antenna must be able to be built in without significantly altering the design of the device.

This is achieved when the apparatus as claimed in claim 7 comprises a screen which surrounds a portion of the electronic components of the apparatus and consists of an insulating material which is metallized on both the side facing away from the components and the side facing the components. , Wherein the patch antenna is at least part of the metallization facing away from the components.

5 DK 176625 B1

Typically, apparatus of this type will be provided with a screen for radio frequency signals. It will normally be a metallized plastic screen, which for metallurgical reasons is metallized on both sides, so that it is in fact a double screen. When the exterior of the screen (or a portion thereof) is used as a patch antenna, the inside of the screen may continue to function as a screen for radio frequency signals as set forth in claim 8, at the same time as it constitutes the ground plane of the patent antenna.

Since the radiation diagram of such a patch antenna will be highly directional, the desired radiation diagram is obtained by the patch antenna as in claim 9 being positioned on the side of the apparatus which, when used by a person, turns away from the person. For a mobile phone, this will be the back of the phone. The directional effect is obtained, as the other metal parts and circuits of the telephone exert a shielding effect towards the person.

The invention will now be explained in more detail below with reference to the drawing, in which: FIG. 1 shows part of a circuit in an existing mobile telephone; FIG. 2 shows the design of a patch antenna according to the invention; FIG. Figure 3 shows the radiation from a mobile phone with a patch antenna according to the invention; 4 shows the radiation from a mobile phone with both a patch antenna and an activated pull-out antenna; FIG. 5 shows a block diagram of an alternative embodiment of the invention; and FIG. Figure 6 shows a mobile phone arranged in a dedicated holder with a patch antenna.

In FIG. 1 is shown how a part of the circuit in existing mobile phones can be constructed. A number of electronic components 2, 10 are mounted on a circuit board 1 and, for the purpose of radiating and radiating radio frequency signals, the components are surrounded by a screen 3, which typically consists of a plastic material 4, which is provided on both sides with a metallization 5. 6. Metalization on one of the sides will usually be sufficient to perform the shielding function; but usually the screen will be metalled on both sides for production reasons. This means that the metallization on the outside can be used for other purposes.

20 In FIG. 2 is shown how this according to the invention can be utilized for a patch antenna. On the inside of the plastic material 4, the metallization 6 is still present, while the metallization 5 of FIG. 1 in areas 7 and 8 are removed.

On the middle portion of the exterior, the metallization 25 constitutes a patch antenna 9. This patch antenna will, i.a. due to the shielding metallization 6, in particular, radiate radio signals in the direction away from the plastic material 4 and thus away from the components 2. The circuit board 1 and the other metal parts of the telephone will produce an additional shielding effect in the opposite direction. FIG. 3 shows that when the screen 4 with the patch antenna 9 is placed on the back 10 of a telephone 11, a radiation diagram is obtained, the radiation 12 being directed away from the person 13 using the telephone. It will be seen that the telephone 11 is also provided with a rod antenna 35 14, which in this situation is not connected and therefore does not emit radio signals.

in DK 176625 B1

As shown in FIG. 4, the rod antenna 14 may be arranged as a pull-out antenna which is only switched on when it is pulled out. In that case, it has an omnidirectional radiation diagram, which means that when it is pulled out, the telephone 11 will largely broadcast (and receive) radio signals equally well in all directions, and thus also in the direction of the person 13. The idea is such that in areas of sufficient radio coverage, the radiation 12 10 from the patch antenna 9 will be sufficient to ensure connection, as a base station will normally be sufficiently close to the radiation 12. The pull-out antenna 14 may thus be depressed and thus interrupted. . Thus, the person 13 is thus spared the powerful 15 radiation from the telephone. This is similar to that of FIG. 3.

In areas where the radio coverage is not good enough for this, the antenna 14 can then be pulled out and thus connected, so that the telephone 11 receives the circular radiation diagram with the radiation 15. In this situation, which corresponds to FIG. 4, the person 13 is exposed to radiation in the same way as with ordinary mobile telephones which are only provided with a radiant antenna; but, as mentioned, this will only be the case with less good radio coverage. In practice, it will usually be such that in urban areas the radio coverage will be sufficient for the situation in fig. 3 can be used and the person thereby saved for the radiation, while outside the urban areas it will typically be necessary to supplement with the extracting antenna and the associated radiation of radio energy. Thus, for the vast majority of subscribers, there will be a significant reduction in the radiation to which they are exposed.

In the embodiment described above, the omnidirectional antenna 14 is switched on so that the user 8 DK 176625 B1 himself pulls it out when the transmit / receive conditions require it. FIG. 5 shows a block diagram of an alternative embodiment. Here, the signal to and from the antenna 14 is connected to the telephone's transmit-receive circuit 16 via a switch 5. A detection circuit 18 can measure the field strength of a signal received on the patch antenna 9 and control the switch 17 in dependence thereof. If the field strength is above a predetermined threshold, the connection between the antenna 14 and the transmit / receive circuit is interrupted, while this connection is similarly terminated when the field strength of the received signal is below this threshold. The antenna 14 is thus switched on only when the signal received at the patch antenna 9 is too low to ensure a good connection. Since transmitting to one and the same base station, the received signal will often be a sufficiently good indicator of whether the transmitted signal is sufficiently strong. Of course, if the antenna 14 is also a pull-out antenna in this situation, the full effect of this principle is obtained only if the antenna is pulled out.

20

Alternatively, a special signal may be sent from the base station to the telephone if the signal received from this is too weak, and the detection circuit 18 may then be arranged to receive this signal and control the switch 17 25 in dependence thereof. In this way, it is the signal received at the base station that determines whether it is necessary to connect the radiant antenna 14.

With the above-described patch antenna on the back of the telephone, a much simpler connection to an external antenna in e.g. a car than has been possible so far. An external antenna of e.g. the car roof is used to increase the range of the phone. Heretofore, the transmission of the radio frequency signals between the mobile telephone and the external antenna has usually been done by coaxial cables. has a coaxial 9 DK 176625 B1 connector at the bottom to which the external antenna can be connected.

However, the coaxial connectors can be replaced by two patch antennas arranged opposite each other, as seen in FIG. 6. The telephone holder 20, also referred to as a cradle, is provided with a patch antenna 19, the size of which corresponds to the size of the patch antenna 9 in the telephone, and which is arranged so that it will be opposite to this one when the telephone is placed in the holder. The patch antenna 19 is connected to the external antenna by means of the cable 21. The holder 20 can furthermore be provided with e.g. guide rails which can ensure that a telephone is always placed in the holder so that the two patch antennas are 15 opposite each other and at a well-defined distance from each other.

Thus, the radio frequency signals are transmitted wirelessly between the two patch antennas. This means that the coaxial connectors can be saved and a solution that is not subject to wear, as is the case with the coaxial connectors.

Although a preferred embodiment of the present invention has been described and shown, the invention is not limited thereto, but may also assume other embodiments within the scope of the following claims.

Claims (3)

10 DK 176625 B1 A hand-held apparatus (11) comprising at least two transmitting antennas (9, 14) for transmitting a radio signal, wherein a first (14) of the at least two transmitting antennas has an omnidirectional radiation characteristic, and a second (9) of the at least two transmitting antennas are a patch antenna (9) having a directional radiation characteristic, characterized in that the apparatus comprises a screen (3) which surrounds a portion of the electronic components (2) and consists of an insulating material (4), there is metallized on both the side facing away from the components and the side facing towards the components and said patch antenna (9) being at least part of the metallization facing away from the components (5). Apparatus according to claim 1, characterized in that it is directed towards the components metallization (6) for shielding radio frequency signals. Apparatus according to claim 1 or 2, characterized in that the patch antenna (9) is arranged on the side (10) of the apparatus which, when used by a person (13), turns away from the person.