Meander antenna for mobile telephone with whip antenna

(54) (56) (57)

PATENT INVENTOR INVENTOR'S OFFICE NAME

Allgon AB, Box 500 184 25 Åkersberga SE Bo Wass, Åkersberga SE

Axel Ehrner's Patent Office AB

Meander antenna device

CALLED PUBLICATIONS: - - SUMMARY:

An antenna device for a portable radio communication device, in particular a hand portable mobile phone, which has at least one radiating element having a meander-shaped winding and cylindrical configuration. This structure is particularly advantageous in combination with an extendable and retractable splash antenna and, when it has two or more meander-shaped radiating elements, in radiant multi-band structures. The antenna device is suitable for manufacturing in large quantities, for example by means of a technology for

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flexible printed circuit boards.

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The numbers in brackets indicate international identification code, iNID code. Letters in clamps indicate international document code.

509 640

The present invention relates to an antenna device according to the preamble of the appended independent claims. In particular, the invention relates to an antenna device for a hand-portable mobile phone which requires a compact and efficient antenna. The antenna device according to the invention is particularly advantageous when two or more radiating elements are to be combined or when an impedance matching device is required for matching the radiating element of the antenna device with transmitter / receiver circuits in the telephone.

A common problem when reducing the size of a radiant antenna is a reduction in its relative bandwidth. Helix-shaped radiators are commonly used when antennas that are limited in limited height volumes are required. However, the loops in a helix antenna generate a magnetic field that binds energy, resulting in a further reduction in bandwidth. Helix radiators also have the problem of strong interconnection when two or more radiators are arranged close to each other.

GB-A-2 280 789 discloses an antenna device having multiple loops formed by conductive radiating elements arranged on a dielectric substrate. The substrate may be tubular and be provided with conductive strips on one side, the strips being bonded along the abutting edges of the tubular substrate. In another embodiment, the substrate is flat and has conductor strips that are precipitated on both sides, the strips being interconnected with passages along opposite edges of the substrate. This prior art antenna device has the inherent disadvantages of helix antennas and is difficult and complicated to manufacture due to the necessity of providing through-holes in the substrate or connecting conductors at the edges.

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509 640

Although relatively efficient and compact, there are a large number of prior art antenna devices which are associated with the aforementioned problems due to the use of helix radiators. Such antenna devices are described, for example, in European patent applications published with the numbers 0 635 898 A1, 0 593 185 A1 and 0 467 822 A2, the PCT applications published with the numbers WO 94/10720 and WO 95/08199 and US Patent No. 4,868 576th

In the past, meander antennas have been used when required by an antenna device to have a total length that is short in relation to the wavelength at which a connected transmitter / receiver is operated. DE-A1 31 29 045 discloses a direction-determining antenna which has, for example, a meander structure. A radiant element therein has a meander winding configuration and is mounted on a dielectric carrier.

DE-A1 31 29 045 is considered to describe the antenna belonging to the prior art and is closest to the invention. The problem to be solved with this is the reduction of the height of a directional antenna, and in particular to make it mobile and possible to hide. However, it describes only a meander antenna having a flat configuration. Further, the lessons learned herein include improving the bandwidth of the antenna by using a conductor having relatively high resistance, which leads to a less efficient antenna. Furthermore, there are no measures for obtaining a mechanically durable antenna, an antenna suitable for accommodating a limited volume or an antenna that can be combined with other types of antennas.

Another planar antenna element winding in meander form is described in Abstracts of Japan 60 E 1572 (publication no. 690108) which includes a dipole winding in meander form and a matching device connected to a

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509 640 coaxial transmission line. A meander winding arrangement for a helix antenna is described in US Patent No. 5,298,910. Not in either of the two latter devices is a transmission line connected to the end of the meander winding conductor.

Swedish patent application 9601706-6 comprises devices that are integrated with an antenna for matching the antenna to circuits in a hand-portable mobile phone. A similar matching device also fits in the present invention. The aforementioned Swedish patent application is therefore incorporated herein by this reference.

An object of the invention is to provide an efficient antenna device according to the preamble of claim 1, which solves the problem of providing an antenna device which is mechanically durable and has a geometry suitable for placement in a small volume. Further objects are to provide replacements for helix radiators which also provide improved antenna performance, to overcome the aforementioned problems of bonding electromagnetic energy in the radiator or radiators of the antenna device, to avoid penetrations in a carrier carrying the radiating element (s) , to provide an efficient and cost-effective impedance matching device integrated with the antenna device, to provide a configuration that is both efficient and mechanically durable, to enable the use of more precise production techniques than, for example, wound helices, and to provide an antenna in which various radiating elements can be combined without being adversely interconnected, particularly where the combination comprises a retractable whip antenna.

These and other objects are achieved with an antenna device according to the characterizing part of claim 1. This radiator geometry has been found to be particularly advantageous in terms of stability.

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509 640 bandwidth and brilliant features. The radiant first element of this antenna device is a meander conductor which is arcuate or curved to occupy a space similar to that occupied by a radiant helix element. This configuration allows the antenna device of the invention to be used in most applications in radio communication devices, especially in mobile phones, where helix antennas have been used previously. Compared to a helix antenna, the advantages of using the antenna device according to the invention are, for example, a greater bandwidth, improved production tolerances, leading to less discarding, a lower degree of coupling to any nearby radiator, which greatly improves operation in several bands, and a possibility to integrate an impedance matching circuit on the same carrier with at least partially the same production technology. That the radiating element extends alternately in positive and negative angular directions with respect to its center axis is understood to include that the radiating element describes a meander curve which changes peripherally at least once during its propagation along a longitudinal axis of an imaginary cylinder shell, preferably having a circular or elliptical base.

When the antenna device comprises one or more additional radiating elements, it is possible to function within a wider frequency band or two or more separated frequency bands. It is possible to produce all radiant elements simultaneously in the same sequence of manufacturing steps.

When it is explicitly important to limit the electromagnetic energy bound in the radiant structure, it does not include any complete turns, preferably it may comprise only the configuration describing small fractions of an entire turn around a center axis.

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509 640

The first and second supply points may be connected and jointly connected to circuit arrangements in the radio communication device. This can also be applied when using more than two radiant elements. Alternatively, the various radiating elements may be separately connected to the radio circuit device.

The antenna device preferably includes a dielectric carrier which supports the radiating structure to allow it to project outwardly from the chassis of the radio communication device on which the device is intended to be mounted. This allows for an efficient radiation pattern. The support is preferably a dielectric flexible film or laminate having the radiant structure applied thereto or therein in the form of a conductive film structure, possibly obtained by an etching process. A printing technique is suitable for manufacturing in large quantities.

It may be advantageous to combine the antenna device according to the invention with a extendable and retractable spray antenna, as will be appreciated from the following description of preferred embodiments. The carrier and conductors of the antenna device may then include one or more switches for connecting or disconnecting different radiating elements in different modes of operation.

Especially when the carrier is a flexible film with a printed circuit pattern, it is advantageous to integrate on the carrier an impedance matching device for matching impedances of any radiating element of the film or in combination with this structure with the circuit arrangement of the radio communication device, which usually fits at 50 ohms.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1A-B show a hand-portable mobile phone equipped with an antenna device according to several fundamentally similar embodiments; 97-10-23

509 640 shapes according to the invention, wherein a meander conductor extends in a cylindrical manner and protrudes outwardly from the telephone chassis, which is also provided with a retractable and retractable spray antenna;

Figures 2 AC show various possible meander conductor configurations arranged on a flexible film carrier in accordance with the invention;

Figure 2D shows the flexible film carrier carrying the meander conductor formed in a cylindrical configuration which could be used, for example, to replace a helix conductor in different antenna applications;

Figures 3A-B show dual meander conductors tuned to different frequencies on common flexible film carriers providing dual band function of an antenna device according to the invention, wherein the dual conductor conductors are either fed separately or via a common feed point;

Figure 4 shows a combination of a meander conductor having a cylindrical configuration and an extendable and retractable rod antenna;

Figure 5 shows a combination of a meander conductor having a cylindrical configuration and an extendable and retractable rod antenna, in which a flexible film carrier for the meander conductor is provided with matching device for matching the impedances of the meander conductor and the spray antenna with an impedance of the transmitter / receiver crest device of a mobile phone;

Figure 6 shows another combination of a meander conductor having a cylindrical configuration and an extendable and retractable spray antenna, the meander conductor and the spray antenna being connected in series when the spray antenna is in its extended position;

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509 640

Figure 7 shows yet another combination of a meander conductor and an extendable and retractable riser antenna, a coaxial transmission line being connected to the meander conductor and rupture antenna respectively;

Figure 8 shows a combination of a meander conductor and an extendable and retractable ratchet antenna, the riser antenna being in an inserted position;

Fig. 9 shows a combination somewhat different from that shown in Fig. 8, wherein the spray antenna is in an inserted position;

Figures 10A-B show yet another combination of a meander conductor and an extendable and retractable riser antenna, a top of the riser antenna carrying the meander conductor and can either be conductively connected thereto or not.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Fig. 1A, a radiant meander element 1 is supported by a dielectric cylindrical carrier 2 and mounted so that it extends outwardly on a chassis 3 to a hand portable mobile phone 4. The position of the meander element 1 on the chassis 3 is selected so that the radiation of the meander conductor 1 is emitted. and is effectively received in various positions selected by a user during standby or during a telephone call. In Figures 1A-B, the meander element is located on one side of the top of the chassis 3 extending upward.

Fig. 1A also shows an extendable and retractable spray antenna 5 in its extended position. A blast antenna can either be combined with the meander element or not, depending on the antenna performance required in the particular case. Fig. 1B

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509 640 shows the arrangement of Fig. 1A with the spray antenna in its inserted position.

Fig. 2A shows a first possible shape 6 of the radiant meander element which is an etched conductor pattern on a dielectric film carrier 7 in a planar configuration. The radiating element extends from a feed point 8 at one edge of the carrier 7, which has a substantially rectangular shape, in an alternating curve including parallel sections and semi-circular curves to a free end 9 at an opposite edge of the carrier 7. The single radiant meander element is formed from the planar configuration to a configuration wherein the carrier 7 is tubular or at least forms part of a cylinder, which will be further shown below.

Figures 2B and C show, with corresponding reference numerals, second and third alternative shapes 10, 11 of the meander element, including rectangular shapes and saw tooth shapes, respectively, which extend and are formed together with the support 7 in a manner similar to that of the meander element of Figure 2A.

Fig. 2D shows a preferred cylindrical configuration in which the meander element 12 and the flexible film carrier 13 are formed together. This configuration is compact and provides good durability. It can be used in most antenna applications where substantially the space occupied by a helix antenna is available and especially when higher performance than that of a radiant helix element is required. Alternatively, the flexible film carrier may be exchanged for another dielectric carrier, preferably one having a cylindrical shape of any suitable cross-section, to which a meander conductor may also be applied or developed by a high precision technique, for example etching. As can be seen from Fig. 2A, the configuration can be said to have an imaginary center axis which the meander element 12 curves around so that the angle relative to the axis alternately increases and decreases.

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509 640

Referring to Fig. 3A, double manger elements 14, 15 are shown on a common carrier tuned to two different frequencies which allows operation of the antenna device in two overlapping or separated frequency bands. These elements are supplied via a common supply point 17 which is coupled to the circuit arrangement of a hand portable mobile phone, possibly via an impedance matching device (not shown). It is also possible to arrange more than two meander elements together to obtain function in more than two frequency bands or even wider bands than can be achieved with two elements. Although shown in a well-functioning planar configuration in Figure 3A, the flexible film carrier of the multimeander device is preferably designed to be formed into a cylindrical configuration described above for a single element winding in the mean space.

It can be shown by calculations and confirmed by simulations and tests that meander elements provide a great advantage over helix elements for function within separated or wider frequency bands, since the degree of coupling between the individual elements is much smaller for meander elements than for helix elements assuming the same or comparable geometric separations.

Fig. 3B shows an alternative to the feeding arrangement of Fig. 3A. Here, each of the individual elements 18, 19 has its own supply point 20 and 19 respectively, which are intended to be connected individually to the telephone circuit arrangement, possibly via an impedance matching device.

Referring to Fig. 4, there is shown a combination comprising a cylindrically configured radiant meander element 22 supported by a cylindrical flexible film carrier 23, one point thereof being a feed point 24 and the other being a free

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509 640 end 25, wherein a extendable conductive spray antenna 26 is provided with a stopper 27 at a lower end adapted to contact the feed point 24 of the meander element 22 through a contact device 28 when the spray antenna 26 is extended, as shown in FIG. 4, and is provided. at the opposite end 29 with an elongated dielectric line 30 of the spray antenna which terminates with a knob 31 intended to hold as the spray antenna 26 is displaced.

The length of the elongated dielectric portion 30 is substantially equal to the length of the cylindrically configured meander element 22, so that the splash antenna 26 has no common extension with the meander element 22 in the inserted position (shown in Figure 8).

The radiators 22, 26 of the antenna device of Fig. 4 are preferably both of the same type, for example of half-wave or quartz-wave type.

In general, when higher antenna performance is required, eg during a telephone call, the spray antenna is generally pulled out and contacted via the contact device to the supply point of the meander element, so that the meander element and the spray antenna will be connected in parallel to the telephone circuit arrangement. In this configuration, the spray antenna performs most of the antenna function. It is also possible to provide an antenna of this type with more complicated switching devices which can completely disengage one of the elements when not needed.

Figure 5 shows schematically a general way of providing an impedance matching device 32 integrated on a dielectric carrier 33 to the antenna device according to the invention. Matching device 32 is connected to a feed point 34 of a meander element 35 and comprises reactive components 36,

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509 640 (shown schematically) and terminal sockets 38, 39 for signal and ground connections (not shown) to the telephone.

The arrangement of Fig. 6 preferably includes a quarter wave type meander element 40 on a cylindrical dielectric carrier 41, preferably a retractable and retractable half-wave type antenna 42 having a dielectric elongate portion 43 mounted on an upper end 44. This arrangement further differs from that of Fig. 4 in that the spray antenna 42 is fed in its extended position, either conductive or capacitive at its lower end 45 by an upper portion of the meander element 40.

The arrangement of Fig. 7 preferably includes a substantially quartz-wave meander element 46 on a dielectric cylindrical carrier 47, preferably a retractable and retractable quench-wave antenna 48 having a dielectric elongated portion 49 mounted at an upper end 50. This arrangement further differs from that shown in Fig. 4 in that the inner conductor 51 in a (coaxial) transmission line 52 feeds the spray antenna 48 when it is in its extended position, either conductive or capacitive, at its lower end 53, and an upper end 54 of the meander element 46 is fed by the screen 55 in the transmission line 52 while a lower end 56 of the meander element 46 is an open end.

In situations where the antenna device is required to be more compact, the spray antenna 57 is slidable as shown in Figure 8. In general, then the spray antenna 57 provides little or no antenna function at all, while the meander element (s) 58 emits and receives radiant energy to and from the telephone. Here, the dielectric portion 59 extends along the entire axial length of the meander element 58 so that the bar is disconnected in the inserted position.

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509 640

Alternatively, as schematically shown in Fig. 9, the splash antenna 60 may extend jointly with the cylindrically configured meander element 61 at least partially also in the inserted position of the splitter antenna 60, in order to reduce the required receiving depth in the handheld mobile phone chassis. In this case, the elongated dielectric portion 62 extends only partially in common with the meander element 61 when the rod antenna is inserted.

Figs. 10A and 10B show, in inserted and extended positions, a ratchet antenna 63 carrying at its top end 64 a meander element 65. A conductive sleeve 66 forms a connection point to the telephone circuit arrangement (or a matching device). Either there is a conductive connection between the bar and the meander elements, together they contact the sleeve 66 at the portion 64 in the inserted position and at the portion 67 in the extended position, or there is no conductive contact, the meander element 65 alone contacting the sleeve 66 in the inserted position. and the antenna rod 63 alone contacts the sleeve 66 in the extended position.

A plurality of multi-band antenna devices may be constructed according to the principles described above with reference to Figures 4-10, if more than one meander element is included.

Although the invention has been described in connection with a number of preferred embodiments, it should be understood that several modifications can still be made without departing from the scope and scope of the invention as defined in the appended claims. One such possible modification is to provide the feeders and feed configurations in ways other than those shown in Figures 4-10.

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