DESCRIPTION OF RELATED ART One of the major drives in the mobile radio telecommunication business is to produce and offer very small hand-held radio communication devices, such as digital and analogue cellular phones. A big part of the length of a cellular phone is constituted by the antenna, which needs to be, for optimal performance, of a predetermined length in dependence of a selected antenna type and application, for instance AMPS, PCS, GSM, DECT at predetermined frequency ranges.

A radio intended for two-way communication generally operates with either an external fixed rod or helix antenna or with a retractable antenna. An external fixed rod will add the total length to the size of a cellular phone, in practice making it impossible, for instance to carry in a pocket. A fixed mounted helical antenna will not contribute significantly to the total length of the cellular phone, but will instead require more power for transmitting signals or be more prone to disturbances when receiving signals. A fixed mounted helix operates well in a stand-by mode and for some applications even in active mode but requires at least some performance trade-off. An elegant solution to this is to combine a helix operative in stand-by mode with a retractable antenna, operative in an extended position when the cellular phone is

in active mode and which is rendered inactive in an retracted position when the cellular phone is in stand-by mode.

A retractable antenna, either by itself or in combination with an stand-by mode antenna, e. g. a helix antenna, will of course still have a specific length. When the retractable antenna is in it's retracted position it will extend into the housing of the cellular phone, requiring space and length. That is, if the radiating part of the retractable antenna needs to be, for instance 60 mm in its active position, a 60 mm long volume or more, in case where a isolation is required, need also to be reserved inside the housing of the cellular phone for the antenna in its retracted position.

In EP-467 822 is an electrical device and electrical transmitter-receiver particular useful as a CT2 cordless telephone disclosed. A retractable antenna rod is carrying an antenna coil on its top. When the antenna rod is in its retracted position the antenna rod is inactive as a radiating element and the antenna coil is active. When the antenna rod is in its extended position, the antenna rod is active and is fed with energy through said feed point, the antenna coil being inactive. A feed point for feeding RF energy to the antenna rod and the antenna coil is located in proximity of the entering point of the antenna rod into the housing. Both the antenna rod and the antenna coil are of one-quarter wavelength type establishing the physical length of the antenna rod.

In EP 516 490 an retractable antenna is disclosed. A retractable antenna rod is carrying an antenna helix. A support provides a coaxial feed to said antenna elements, with an inner conductor and an outer conductor where said outer conductor is coupled to ground. Said antenna rod is coupled to

said inner conductor in both ends in its retracted position and thus essentially becomes part of the central coaxial feed coupled directly to the helical antenna element and is rendered inactive as a radiating element. If the antenna rod is of one-quarter wavelength type, the physical length is thereby set of both the antenna rod and the support, which should substantially'cover the antenna rod in its retracted position.

SUMMARY OF INVENTION The main object of the present invention is thus to achieve a smaller and more effective antenna for hand-held radio communication devices, a smaller and more effective hand-held radio communication device and a method for receiving RF signals in a more effective manner.

The problems described above, with how to achieve an antenna which is shorter than prior art antennas and yet has good performance characteristics, is solved by allowing a part of the radiating antenna to extend into the housing of the hand- held radio communication device and to feed the antenna device in the end extending into said housing.

In more detail the objects of the present invention, with how to achieve an antenna which is shorter than prior art antennas and yet has good performance characteristics are obtained, according to one embodiment, by providing a first tube-like radiating element, comprising a feed point in a first end, and fastened in a second end in the housing of a hand-held radio communication device so that substantially the complete first element is extending into said housing.

A second radiating element is slidable mounted inside'said first element so that the second element is coupled to said second end when the second element is in a extended position, construing a combined radiating element with a total length substantially equal to the combined length of said first and second element. The second element being coupled to said first end when the second element is in a second retracted position, construing a combined radiating element with a total length substantially equal to the length of one of said first or second element. The second element is extending substantially outside said housing when the second element is in the extended position.

According to one embodiment of the invention a third radiating element is coupled to the second end of said first element so that when said second element is in its retracted position said first and third element construes a combined radiating element with a first electrical length. When said second element is in its extended position said third element is rendered inactive, either by being decoupled from said first element, or by letting the second element pass through said third element, so that said first and second element construes a combined radiating element with a second electrical length, where said first and second electrical lengths being equal.

An advantage with the present invention is that for a retractable antenna rod of a specific physical length, substantially determined by the required electrical length, the physical length extending into the housing of an hand-held radio communication device can be substantially lessened.

An advantage with the present invention is that for an retractable antenna rod of a specific electrical length, the physical volume needed, inside the housing of an hand-held

radio communication device, for the antenna rod in its retracted position can be substantially lessened.

Another advantage with the present invention is that no isolation between feeding means and coupling means, due to inductive and capacitive coupling, for the extendable antenna rod in its retracted position, is required.

Another advantage, according to one embodiment of the invention, is that smaller hand-held radio communication devices can be achieved.

Another advantage, according to one embodiment of the invention, is that since said first and third, and said first and second electrical length are equal, one matching circuit with one feeding point can be used for impedance matching in both the extended position and in the retracted position.

Another advantage, according to one embodiment of the invention, is that less power consuming transmission can be achieved both in active and stand-by mode.

Another advantage, according to one embodiment of the invention, is that an increased efficiency can be achieved for hand-held radio communication devices.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the present invention and wherein figure la shows a prior art antenna in a retracted position, figure lb shows a prior art antenna in an extended position, figure 2a shows an antenna according to a first embodiment of the invention in a retracted position, figure 2b shows an antenna according to the first embodiment of the invention in an extended position, figure 3a shows an antenna according to a second embodiment of the invention in a retracted position, figure 3b shows an antenna according to the second embodiment of the invention in an extended position, figure 4a shows an antenna according to a third embodiment of the invention in a retracted position, figure 4b shows an antenna according to the third embodiment of the invention in an extended position, figure Sa shows an antenna according to a fourth embodiment of the invention in a retracted position, figure 5b shows an antenna according to the fourth embodiment of the invention in an extended position,

figure 6a shows an antenna according to a fifth embodiment of the invention in a retracted position, figure 6b shows an antenna according to the fifth embodiment of the invention in an extended position, Figure 7a shows an antenna according to a sixth embodiment of the invention in a retracted position, figure 7b shows an antenna according to the sixth embodiment of the invention in an extended position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In figures la and lb a prior art antenna is disclosed. With 101 is a radiating antenna rod denoted and 102 denote an antenna coil carried at the outer end of the antenna rod 101.

The antenna rod 101 is slidably, movable mounted through an opening 103 in the housing 104 either to a retracted position as shown in figure la or in an extended position as shown in figure lb. When the antenna rod 101 is in its retracted position, substantially only the antenna coil 102 is disposed outside the housing 104 and when the antenna rod 101 is in its extended position, substantially the complete antenna rod 101 is disposed outside the housing 104.

Electrical switching means comprising a metal spring clip 105 fixed within a bushing 106 circumscribing opening 103 enables galvanic contact between circuitry 108, schematically shown in figure 1 and the antenna coil 102 through a feed point 107 when the antenna rod 101 is in its retracted position, and galvanic contact between the circuitry 108 and the antenna rod 101 when the antenna rod is in its extended position. In figure 1b is the active radiating part of the antenna rod 101

in its extended position denoted 109 and in figure la is'the active radiating part of the antenna rod 101 denoted 110.

As is easily realised, the physical length of the radiating part of antenna rod 101 are the same in both its active, extended position and in its inactive, retracted position.

Coupling means 111 is used for coupling the antenna rod 101 to the feed point 107 when the antenna rod is in its extended position. The feed point 107 needs to be located far away from the coupling means 111, when the antenna is in retracted position so that no inductive or capacitive coupling occur between the feed point and the coupling means. Such coupling will decrease the antenna efficiency. This effect also put requirements on the length of the antenna rod 101 and where to position the feed point.

Figures 2a and 2b shows a first preferred embodiment of the present invention. 201 denote a first elongated radiating element in the form of a conductive tube and 202 denotes a second conductive element in the form of an antenna rod. The first and second elements being substantially of the same length. A circuit 203 feeds RF signals through a feed point 204 to a first end 205 of the first element 201. Support means 206 is fixed on the top of a housing 207 of a hand-held radio communication device. The first element 201 is fixed to the support means 206 at a second end 209 through methods well known in the art, such as screwing, gluing, pressing etc.

The second element 202 is movably mounted inside the first element 201. Coupling means 208, located at the second end of said first element 201, enables the second element 202 to take two positions, a retracted position as shown in figure 2a, and an extended position as shown in figure 2b. In the retracted

position the second element is electrically coupled to the first element in the first end 205 rendering said second element 202 a integrated part of said first element 201 for radiating purposes. In the first retracted position the radiating part of the antenna assembly is denoted 210 in figure 2a.

Electrical coupling in said first end 205 between said first 201 and said second element 202 in the retracted position can for instance be achieved by narrowing the diameter of the first tube-like element so that when said second element is retracted a conductive part 212 at the end of the second element is forced against the inner sides of the tube-like first element 201 enabling galvanic contact.

In the second, extended position the second element 202 is electrically coupled to said second end 209 through the coupling means 208. The first and second element thus co- operates to construe an antenna, which is twice as long as the antenna in the retracted position. In the second, extended position the radiating part of the antenna assembly is denoted 211 in figure 2b. The length 211 is substantially twice the length 210.

Different means may be used to match the antenna and circuit impedance in the respective positions of the second element, by for instance discrete components, integrated patterns or other means In figure 3a and 3b is a second embodiment according to the invention shown. With 301 is a first radiating element in the form of a conductive tube denoted and with 302 is a second radiating element in the form of an antenna rod denoted.

Circuitry 307, schematically shown in figure 3 feeds and

retrieves RF signals from the antenna assembly through a feed portion 308 at a first end 309 of the element 301. The first element being fixed onto a housing 305 in a second end 306. A top is denoted 303, arranged so that a user may easily retract or extend the second element 302 to a retracted position shown in figure 3a or an extended position shown in figure 3b. Said second element being'movable mounted inside said first element and being able to take said retracted and extended position through first coupling means 304 located at said first end 309 and second coupling means 312 located at said second end 306.

When said second element 302 is in its retracted position both said first and second coupling means 304 and 312 couples said second element 302 to said first element 301 in both said first and second ends. When said second element is in its extended position said second coupling means 312 couples said second element to said first element 301 in said second end 306 so as to construe a combined element.

The function of the embodiment in figure 3 is basically the same as the embodiment described in conjunction with figure 2.

The main difference being that in the embodiment according to figure 3 the antenna assembly extends further into the housing 305 than in the embodiment of figure 2 where a part of the antenna is displaced outside the housing 207 and, that in the embodiment according to figure 3 the second radiating element is coupled in both said first and second end in the retracted position. The radiating length of the antenna assembly according to the embodiment shown in figure 3 in its retracted position is denoted 310 and shown in figure 3a, and the radiating length in its extended position is shown in figure 3b and denoted 311. It would of course also be possible to fixedly mount the first element in the housing in said first end 309.

In figure 4a and 4b is a third embodiment according to the invention shown. 401 denote a first radiating element in the form of a conductive tube and 402 denotes a second conductive element in the form of an antenna rod. A circuit 403 feeds RF signals through a feed point 404 to a first end 405 of the first element 401. Support means 406 is fixed on the top of a housing 407 of a hand-held radio communication device. The first element 401 is fixed to the support means 406 at a second end 409 through methods well known in the art, such as screwing, gluing, pressing etc, this is achieved through fastening means (not shown).

The second element 402 is movable mounted inside the first element 401. Coupling means 408, located at the second end of said first element 401, enables the second element 402 to take two positions, a retracted position as shown in figure 4a, and a extended position as shown in figure 4b. In the retracted position the second element is electrically coupled to the first element in the first end 405 through a conductive part 413 of said second element 402 being forced against the inner side of the first end 405 of the conductive tube 401 enabling conductive contact. Said first end 405 of said conductive tube 401 is bent inwards to form a part with increasingly smaller radius thereby enabling said conductive part 413 to be forced against the inner side when said second element being retracted to its retracted position, thus rendering said second element 402 a integrated part of said first element 401 for radiating purposes.

In said retracted position said first elements 401 conducts RF signals from said circuit 403 to a third radiating element in the form of a helical radiator 412 mounted in the support 406 and coupled to said first element when said second element 402

is in its retracted position. Said third radiating element can of course be a meander shaped radiating pattern for instance on a dielectrical thin carrier mounted on or inside a base, or any other shaped radiating element.

In a variant of the preferred embodiment the second element is coupled to the third, radiating element. Radiating feed means is used as a term denoting either or both of said first and second elements.

In the retracted position the radiating part of the antenna assembly is denoted 410 in figure 4a and comprises the combined first and second elements 401 and 402 and the third element 412.

In the extended position the second element 402 is electrically coupled to said second end 409 through the coupling means 408 and said third element 412 is rendered inactive as a radiating element. The first and second element thus co-operates to construe an antenna, which is twice as long as the antenna in the retracted position. In the second, extended position the radiating part of the antenna assembly is denoted 411 in figure 4b. The electrical length of the radiating part 410, which is formed by said first element and said third element, and 411 which is formed by said first element and said second element, are substantially the same enabling the use of only one matching circuit if any at all is required and one feed point.

The third element 412 can be decoupled through the coupling means 408 or can continue to be coupled to said second end 409 when said second element 402 is in its extended position. If the helix is left coupled to said second end when said second element is in its extended position, the helix will have no

significant influence on the radiation. This is since the antenna rod in its extended position will go through the centre of the helix, thereby raising the impedance of the helix significantly. The antenna rod will continue to have a relative low impedance, and therefore the helix contribution to the parallel coupled helix and antenna rod can be neglected. That is the helix, or meander does not substantially contribute to the antenna characteristics when the second element is in its extended position.

In a variation of this preferred embodiment, the first element 401 can be coupled to ground in both ends instead of being coupled to said third element when said second element 402 is in its retracted position. The second element being coupled to the feed point 404 in one end and to said third element 412 in the other end, thereby effectively making an coaxial connection from the feed point 404 to said third element 412 when said second element 402 is in its retracted position.

When said second element takes its extended position said first element, being decoupled from ground, and again coupled to the feed point 404 in the first end 405 and to the second element 402 in its second end 409, thus enabling both first and second elements to again act together as one radiating element.

Thus, in this variant, when said second element 402 is in its retracted position only the third element 412 function as an radiating element. When the second element 402 is in its extended position the third element 412 can either be decoupled or continue to be coupled to said second end.

In figure 5 is a fourth preferred embodiment according to the invention shown. The embodiment in figure 5 is very similar to the embodiment described in correspondence with figure 4. In

figure 5 is a first radiating element in the form of a conductive tube denoted 501, a second radiating element in the form of an antenna rod denoted 502 and a third radiating element in the form of a helical antenna, denoted 503. In the embodiment of figure 5 the third radiating element 503 is mounted on top of the second radiating element 502 so that when the second radiating element is moved to its extended position shown in figure 5b the third radiating element 503 is also moved. The third radiating element 503 may or may not be electrically coupled to circuitry 504 through said first and second radiating element 501 and 502, for radiating or receiving RF signals, when the second radiating element is in its extended position. Said coupling between the first, second and third element, ground and feed point, respectively are handled by the coupling means 505.

When the second radiating element 502 is in its retracted position as shown in figure 5a the third radiating element 503 is coupled through said first, second or both radiating elements to the circuitry 504 to receive and transmit RF signals. The first and second element 501 and 502 may function as one radiating element when the second element 502 is in its retracted position or may function as an coaxial feed to said third radiating element 503 as described in more detail in connection with figure 4.

In figure 6 a fifth preferred embodiment is shown. In figure 6 a first radiating element in the form of a antenna rod is denoted 601 and a second radiating element in the form of an antenna rod is denoted 602. A first coupling means is denoted 603, a second coupling means is denoted 610 and a circuitry, schematically shown in figure 6, is denoted 604. The circuitry 604 is coupled to said second coupling means 610 through a

feed portion 605. A support means is denoted 606, said support means being fixed in a housing 607 of a hand-held radio communication device. A second end 608 of said first element 601 is fixed in said support 606 through said first coupling means 603 and a first end 609 is coupled to said feed point through said second coupling means 610. The second radiating element 602 is movably mounted in said first and second coupling means 603 and 610, so as to let said second radiating element 602 take a retracted position, shown in figure 6a, and a extended position, shown in figure 6b.

Said first and second coupling means 603 and 610 couples said first end 609, said second end 608 or both ends of said first and second radiating elements 601 and 602 to each other, when said second element is in its retracted position, so as to let said first and second elements 601 and 602 act as one radiating element comprising two parallel rods. When the second element 602 is in its extended position the first coupling means 603 couples the second end 608 of said first element 601 to the second element 602 so as to form one radiating element comprising two antenna rods positioned substantially one after the other so the length of the combined antenna is substantially double the length of one of the elements 601 or 602.

In figure 7a and 7b is a sixth preferred embodiment according to the invention disclosed and with 701 is a first radiating pattern denoted. Said radiating pattern is a elongated conductive strip, for example a printed circuit on a printed circuit board 702. In one variant the radiating circuit may be applied directly to the housing, moulded into said housing or in any other way applied in proximity and in parallel to a second element. Said second radiating element is denoted 7Q3,

a first coupling means is denoted 708 and a second coupling means is denoted 704. Said second element 703 is coupled to said radiating pattern 701 through one or both of said coupling means 704,708 when said second element is in its retracted position shown in figure 7a, and coupled to said radiating pattern 701 through said first coupling means 708 when said second element 703 is in its extended position. A circuit 705 feeds RF signals to a feed portion 706. A cap is denoted 707. A third radiating element in the form of a meander is denoted 709 and is applied on the inside or outside of a support means 710. This embodiment is similar to the embodiment described in figure 4 but with the tube-like first element substituted with a radiating pattern on the printed circuit board or on or in the housing.

The invention being thus described, it will be obvious that the same may be varied in many ways, for instance may the feed point be located in some distance from said first end for some particular embodiments. 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.