EP1250723B1 - Antenna for a communications terminal - Google Patents

Description

The invention relates to an antenna for a communication terminal with an applied on or in a carrier Conductor structure and a communication terminal with a such antenna.

With the progressive miniaturization of mobile Communication terminals, in particular mobile phones are in the future smaller dimensions due to their size needed. In the field of mobile phones are therefore in Most recently, so-called "stub antennas" were used, the only a short distance from the case protrude. These "stub antennas" have the disadvantage that they are mechanically sensitive and can break off. About that In addition, for design reasons, the antennas as possible completely optically in the miniaturized housing disappear. One way to fully connect antennas integrate, consists of antennas of the aforementioned Type with a conductor track structure applied in or on a carrier, for example, so-called "PCB antennas" (Printed Circuit Board - Antennas).

Such an integrated antenna must be able to cover the entire bandwidth of the respective radio channel. For example, in the so-called GSM 900 MHz band in the Range from 880 to 915 MHz and in the range of 925 to 960 MHz, so that the antenna covers the range of 880 must cover well up to 960 MHz. In addition, especially at Mobile phones have the problem that it is during talk time too different strong resonance shifts of the antenna can come through the different layers of mobile devices in the user's hand. These Displacement of the resonance frequency must accordingly be compensated that the antenna is still broadband than the required frequency band is, so that synonymous with a Shifting of the resonant frequency worked throughout the band can be. However, broadband antennas usually arise then, if they are geometrically big, what the Objective for a miniaturized antenna runs counter. For example, an ideal antenna would have an effective antenna Length of a multiple of a quarter wavelength (λ / 4) the center frequency, in the case of the GSM 900 MHz band of 920 MHz. This length is due to the space in the housing often not available.

From the document EP 0 954 054 A1 is a capacitive Coupling a folding antenna with a whip antenna known.

Document WO 98/38694 discloses a resonant antenna for a radio channel.

From the document US 5,809,433 is one under a Keyboard attachable antenna device known. The Antenna device has a first antenna part and a in the same plane above the first antenna part arranged on the second antenna part.

It is an object of the present invention to provide an antenna to create relatively large bandwidth, which is cheap and reproducible can be produced.

This task is performed by the antenna with the characteristics of independent claim 1 solved.

A capacitive load according to the invention at the end of the first Track structure part leads to an improvement of Power distribution of the antenna. The capacitive load causes this is a virtual extension of the entire antenna, so that the deviation of the effective length from the ideal length can be compensated by the capacitive load. The "Height" of the antenna is not increased, since the Detour lines of the capacitive load predominantly across the height extend.

The capacitive load thus has a similar effect as those from the field of "normal" radio antenna construction well-known roof capacities, which at the upper end of on Buildings, etc., erected vertical monopole rod antennas are arranged, but in addition to note here is that due to the small geometric dimensions and close to the shield cover, the board, the battery pack or other parts of the device against unavoidable capacity the mass of the device will occur and it will also cause the said upsets come through the user's hand.

The two conductor track structure parts can in principle be relative arbitrary to the technical specifications as well as the available be adapted to the existing spatial dimensions. The second However, trace element part should be substantially extend transversely to the first printed conductor structure part. The first Conductor structure part corresponds to the rod antenna with a main extension direction, which at "normal" broadcast antenna construction the vertical direction represents; the second trace structure part corresponds to the horizontal roof capacity. Preferably, the first Conductor structure part in this case an elongated Trace on, which ends up forming the second Ladder Structure Part forks.

The second interconnect structure part preferably has one forming a T-bar at the end of the first trace structure part extending conductor track section. in the The simplest case is the second interconnect structure part only from this one track section, so that in total the conductor track structure has a simple T-shape. In particular, in order to adapt the roof capacity precisely, the second interconnect structure part also meandering or meandered on certain sections be. Various specific embodiments are still described with reference to accompanying drawings.

Depending on requirements, the second conductor structure part symmetrical with respect to the first trace structure part or asymmetric. Unlike one Symmetrical structure performs an asymmetry in the second Track structure part to that due to the two different from the first interconnect structure part spaced reflection points at the ends of the roof capacity a superposition of two waves with slightly different Phase occurs. This leads on the one hand a reduction in the quality of the antenna, but on the other hand too a desirable increase in bandwidth.

The conductor track structure can be designed so that the first Conductor structure part in the second conductor structure part opposite end portion of a connecting element, For example, has a contact pad, with the over a Contact spring a connection to the transmitting / receiving device the communication terminal takes place. This connection point corresponds to the base of a vertical antenna with Top capacity. Alternatively, it is also possible that the first Conductor structure part at both ends with a second Conductor structure part is loaded capacitively. In this Case, the power in the antenna in the first Conductor structure part coupled capacitively or inductively.

So that the antenna as so-called "multi-band antenna" in can work in different frequency ranges, she points out preferably a first antenna part with a first Conductor structure and in a substantially parallel to the first conductor track structure lying another level Antenna part with a further interconnect structure, whereby the antenna is tuned to a desired further radio channel, d. H. to a second resonance, is tuned. The others Conductor structure here is capacitive or inductive with coupled to the first interconnect structure. In the simplest case it is the carrier to a board, which on one surface the first conductor track structure and on the opposite surface of a second interconnect structure having. Of course, it is also possible that it is a kind of multilayer board, which in At various levels even more interconnect structures which makes the antenna not only in two but also can work in several resonance ranges.

In a preferred embodiment, the first Conductor structure part of the first interconnect structure one end the connection element, for example the contact pad, on, and the first trace structure part of the other Track structure is at both ends by a second Conductor structure part capacitively loaded. To be optimal Overcoupling between the second interconnect structure and the to ensure the first interconnect structure are the Conductor structures or any other Conductor structure with respect to the main extension direction of the each first interconnect structure part parallel to each other oriented, that is, the "vertical" antenna parts lie each substantially parallel, since on this piece the Overcoupling mainly takes place.

Figur 1 einen schematischen Schnitt durch ein Mobiltelefon mit einer integrierten erfindungsgemäßen Multiband-Antenne;

Figuren 2a bis 8b jeweils Darstellungen der Leiterbahnstrukturen von verschiedenen Ausführungsbeispielen von zweiseitigen Multibandantennen, wobei die Figuren 2a bis 8a jeweils die Vorderseite mit der ersten Leiterbahnstruktur zeigen und die Figuren 2b bis 8b die zugehörige Rückseite mit der zweiten Leiterbahnstruktur;

Figur 9 eine Darstellung der verschiedenen Strukturen in verschiedenen Ebenen eines Ausführungsbeispiels einer dreilagigen Multiband-Antenne.

The invention will be explained in more detail below with reference to the accompanying drawings with reference to embodiments. The illustrated features can be essential to the invention not only in the combinations mentioned, but also individually or in other combinations. Show it:

Figure 1 shows a schematic section through a mobile phone with an integrated multi-band antenna according to the invention;

FIGS. 2a to 8b are illustrations of the interconnect structures of various embodiments of two-sided multi-band antennas, FIGS. 2a to 8a respectively showing the front side with the first interconnect structure and FIGS. 2b to 8b showing the associated back side with the second interconnect structure;

9 shows an illustration of the various structures in different planes of an embodiment of a three-layered multiband antenna.

Since the main application area of the antennas 10 according to the invention is in the range of mobile phones 1 and here too especially because of the problems of covering the antenna with the hand of the user offers particularly great benefits is in the following embodiments of antennas for Mobile phones go out. It will be on it again noted that the use of such antennas of course not limited to mobile phones.

Figure 1 shows such a typical mobile phone 1 with a Housing 2 and an integrated antenna according to the invention 10. The other components of the mobile phone 1 are only partially and schematically shown. The mobile phone points on the one hand a motherboard 3, on the top the earpiece 6 and below the display 5 are arranged. Below the display 5 is the keyboard (not ) Shown. On the back of the motherboard 3 is under other the battery pack 4 is arranged. The motherboard 3 and the Battery pack 4 are usually made by a shield cover 8 shielded electrically conductive material. In the upper one free space of the housing behind the earpiece 6 between the Rear side of the motherboard 3 above the battery pack 4th there is a free space 9 in which the antenna 10 is arranged.

This antenna 10 essentially consists of a carrier 11 and one on the main board 3 facing front the carrier 11 located first interconnect structure 12 and a arranged on the back second wiring structure 13th

In a particularly simple and inexpensive to produce Case, the antenna 10 consists essentially of a double-sided board, on which side by a conventional etching process, the conductor track structure 12, 13 generates has been. Of course, the wiring patterns on printed on both sides or in another suitable manner applied to a suitable carrier 11 be.

In Figure 2a, the first wiring pattern 12 is on the Front of an antenna according to a first Embodiment shown.

The first printed conductor structure 12 here consists of a first Track structure part 14, which in turn consists of a parallel to the longitudinal axis of the mobile phone 1, "vertical" track section 17 and at the bottom of a "horizontal" track section 18 consists.

The first, "vertical" track section 17 has at the top End as roof capacity the second trace structure part 15th on. The second, "horizontal" track section 18 of the first conductor pattern part 14 serves to the lower End of the first conductor section 17 with the contact pad 19 to connect, which left in the plan view lower corner of the carrier 11 is arranged. About this Contact pad 19 is the antenna 1 via a contact spring 7 with a corresponding lead on the motherboard 3 to a transmitting / receiving unit (not shown) connected (see Figure 1). The contact spring 7 bridges in present embodiment, a distance a of about 6 up to 12 mm.

In all embodiments shown in the figures the contact pad 19 is shown in the same place. These However, position is only by the structure of the respective Mobile phones 1 conditionally. The contact pad can of course also at any other place, for example in the middle below or in the lower right corner of the Be arranged carrier 11.

The entire first conductor structure part 14 forms here, starting from the extraction point to the transmitting / receiving unit, as a so-called "foot point", to the upper end, a monopole antenna, which is almost the same in broadcast antenna construction known "rod antenna" corresponds. End is this "Rod antenna" through the second printed conductor structure part 15 loaded capacitively.

To form this "roofing capacity" 15 is the conductor track section 17 aufgabend end, that is, the second Printed conductor structure part 15 has a printed conductor section 29 on, which looks like a T-bar at the end of the track section 17 of the first conductor pattern part 14 extends.

In each case at both ends of this the T-bar forming Track section 29 extend in a parallel to Main extension direction R of the first interconnect structure part 14, d. H. in the direction of the conductor track section 17, meandering further conductor track sections 24. These meander-shaped conductor track sections 24 consist turn from straight, perpendicular and parallel to Track section 17 oriented, individual sections. In the illustrated embodiment, they extend from the Ends of the T-bar down, d. H. in the direction of vertical trace portion 17 of the first trace structure part 14 counter to the main extension direction R. Of course, they could also be in the direction of Main extension direction R, d. H. upwards, extend. Due to the exact shape of the meander can be especially the change the spatial extent in relation to the antenna length and thereby the capacity for the screen cover 8 and to adjust other components of the mobile phone 1 accordingly, around the antenna to the desired resonant frequency adapt.

The second printed conductor structure part 15 is mirror-symmetrical here to the first trace portion 17 of the first Track structure part 14 executed.

On the back of the carrier 11 is another Antenna part with another conductor track structure 13. This Printed circuit pattern 13 is connected to the printed conductor structure 14 the front very similar. The first Printed conductor structure part 20 of this second printed conductor structure 13 corresponds to the vertical conductor track section 17th of the first interconnect structure part 14 of the interconnect structure 12 on the front. This first trace structure part However, 20 is at both ends with another, as Capacitive load serving trace structure part 21 provided, which here exactly the second trace structure part 15 on the front corresponds.

In the present embodiment, the antenna part is on the front, d. H. the conductor track structure 12, so executed, a resonant frequency of the antenna is in the range of 900 MHz band of the GSM system is, of course the influences by the rear structure 13 are considered. The rear structure 13 couples Capacitive or inductive on the front structure 12 via or vice versa. The rear structure 13 is designed so that a second resonance on the 1800 MHz band of the GSM system lies. That is, the overall structure is designed so that the otherwise at a ¾ λ corresponding frequency of approx. 2700 MHz lying next higher resonance point, which a good real part, pulled down to about 1800 MHz becomes. The exact tuning of the resonance takes place in essentially by the conductor track structures 12, 13 on the Front and back side. In addition to the particular special Formation of the structures 12, 13 but of course also the thickness of the carrier 11, and thus the Distance between the two conductor track structures 12, 13 to each other, as well as the material constants, for example the Dielectric constant, of the substrate impact on the resonance tuning of the entire antenna 10 and need be considered accordingly, or may be suitable to get voted.

In particular, the widths of the tracks of the first conductor structure part and the capacitive Loads are varied. The track width has u. a. strong influence on the quality of the antenna and consequently on the Resonance bandwidth. This also applies to simple antennas with only one antenna part.

FIGS. 3a and 3b show somewhat modified conductor track structures 12, 13 on the front and on the back. in the Contrary to the antenna according to Figures 2a and 2b here the roof capacity forming second trace structure parts 15 ', 21' is not mirror-symmetrical to the main extension direction R executed. Due to the asymmetry of two reflection points at the ends of the trace structure parts 15 ', 21' therefore creates a superposition of two waves with slightly different phase angles. Although this reduces On the one hand the quality of the antenna, but on the other hand leads to a desired increase in bandwidth. in the symmetrical case according to Figures 2a and 2b arise at each of the two ends waves with the same phase, so that these ends act as a common point of resonance. The increase in bandwidth is especially in mobile phones important in which it is the hand of the user resonances on the antenna comes.

Figures 4a and 4b show a further embodiment an antenna 10 according to the invention. The first printed conductor structure parts 14, 20 respectively correspond to the Embodiments in Figures 2a to 3b. Is changed however, the shape of the second wiring pattern parts 16, 22. The second wiring pattern parts 16, 22 extend in each case on both sides from the end of the first printed conductor structure part 14, 20 away meandering in a substantially transverse to the first interconnect structure part 14, 20 extending Main direction. That is, the "T-bar" is here even meandering executed. This form of second trace structure parts 16, 22 is in both the front trace structure 12 as well as the rear Track structure 13 is carried out in this way.

FIG. 5a shows the front side of another one Embodiment. This is just in contrast to the shape according to Figure 4a, the second interconnect structure part 16 'arcuate at the end of the first conductor structure part 14 executed. There is therefore a slightly increased capacity in front. In addition, this embodiment shows that suitable choice of the shape of the second interconnect structure part 16 'the antenna can also be adapted to a round housing can. For this purpose, the carrier 11 is cut out accordingly. The backside trace structure 13 is again adapted to the front trace structure 12, that is, on the upper side corresponds to the second conductor structure part 22 'of the second conductor pattern part 16' of the front Printed Circuit Structure 12. The Lower Second Printed Circuit Structure Part 21 is similar to the second trace structure part 21 executed according to the antenna of Figure 2b.

An embodiment is shown in FIGS. 6a and 6b. in which the front conductor track structure 12 exactly the front Conductor 12 corresponds to the antenna of Figure 2a. In the back conductor pattern 20, however, are the second wiring pattern parts 23 each constructed so that a meandering section 24 to the opposite end of the first conductor pattern part 20 extends and another meandering portion 25 extends outwardly. This increases the capacity additionally.

FIGS. 7a to 8b show two different exemplary embodiments of antennas, where the rear trace structure 13 each only at one end of the first conductor track structure part 20 a second printed conductor structure part 21 ', 22 ', that is, the "vertical" part of the structure 13 is only capacitively loaded on one side. The fronts of the Antennas according to FIGS. 7a and 8a correspond to the antennas according to the figures 3a and 5a. Such one-sided capacitive Loads of the vertical element are also possible and can be useful under certain conditions. she lead, however, that the maximum current is no longer in the Center of the first conductor pattern part 20 is located. To one good overcoupling to the vertical conductor section 17 of the first wiring pattern part 14 of the front To obtain wiring pattern 12 is therefore the embodiment with a bilateral capacitive loading of the first Track structure part 20 on the backside trace structure 13 preferred.

FIG. 9 shows a further multiband antenna which is suitable for three different frequency bands is provided. Accordingly The antenna is superimposed in three levels Structures 12, 13, 26. The first interconnect structure 12 and the second conductive pattern 13 located in the middle correspond here to the conductor track structures 12, 13 on the Front and back of the antenna according to Figures 2a and 2 B. Above this is a third printed conductor structure 26, which according to the backside trace structure 20 the antenna is constructed according to Figure 4b. Of course the levels are arbitrarily interchangeable. Especially can the plane with the first interconnect structure, d. H. the plane with the contact pad, also in the middle, between the other levels. In this case, need the layers of the carrier overlying the contact pad corresponding recesses or the like have to to allow a contact of the contact pad. Alternatively, the contact pad by the above-or underlying levels in a suitable manner to the outside be plated through.

As the various embodiments show, is the Antenna according to the invention in a variety of forms executable and thus to a variety of housing and the available space adaptable. There are a lot here small antennas with relatively large bandwidth in several Frequency bands extremely cheap to produce. In contrast to they have so far used for dual band helix antennas In addition, in the development of the advantage that Prototypes by soldering or removing traces are easily changeable. Because the exact adaptation of the antenna with respect to the different resonances and the impedance of very many external, badly influenced parameters, for example, the shape of the housing, the shield cover, the depends on the motherboard components etc., the optimal structure is extremely difficult or not at all predictable. It is therefore usually in the Development of such antennas several experiments with different Prototypes required to run the device for each device find optimal antenna shape or structure, so that with The antennas according to the invention also benefits from a Reduction of development times and costs can be achieved can.

Claims (13)

1. Multiband antenna (10) for a communications terminal (1) having a conductor track structure (12) which can be provided on and/or in a carrier (11), wherein the conductor track structure (12) has a first conductor track structure part (14) which is capacitively loaded at one end in order tune the antenna (10) to a desired radio channel by means of a second conductor track structure part (16, 16'), characterized in that the antenna has, for the purpose of tuning to a desired further radio channel, a first antenna part with a first conductor track structure (12) and a further antenna part in a plane which is located essentially in parallel opposite the first conductor track structure (12), which has a further conductor track structure (13) which is provided on and/or in the carrier (11) or on/in a further carrier, which conductor track structure (13) is capacitively and/or inductively coupled to the first conductor track structure (12), wherein the further conductor track structure (13) has a first conductor track structure part (20) which is capacitively loaded at the end in order to tune the antenna (10) to a desired radio channel by means of a further second conductive track structure part (22, 22'), wherein the second and the further second conductor track structure parts (16, 16', 22, 22') extend essentially transversely with respect to the particular first conductor track structure part (14, 20), and wherein the second and further second conductor track structure parts (16, 16', 22, 22') each extend on each side from the end of the particular first conductor track structure part (14, 20) in a meandering shape in a main extending direction which runs essentially transversely with respect to the first conductor track structure part (14, 20), or said second and further second conductor track structure parts (16, 16', 22, 22') extend in an arc shape at the end of the particular first conductor track structure part (14, 20).
2. Antenna according to Claim 1, characterized in that the first conductor track structure part (14, 20, 27) has an elongated conductor track which forks at the end in order to form the second conductor track structure part (15, 15', 16, 16', 21, 21', 22, 22', 23, 28).
3. Antenna according to Claim 1 or 2, characterized in that the second conductor track structure part (15, 15', 21, 21', 23) has a conductor track section (29) which extends while forming a T-shaped bar at the end of the first conductor track structure part (14, 20).
4. Antenna according to Claim 3, characterized in that the second conductor track structure part (15, 15', 21, 21', 23) has further conductor track sections (24, 25) which run in a meandering fashion in a main extending direction which is oriented parallel to the first conductor track structure part (14, 20), at each of the two ends of the conductor track section (29) which form the T-shaped bar.
5. Antenna according to one of the preceding claims, characterized in that the second conductor track structure part (15, 21, 28) is of symmetrical design with respect to the first conductor track structure part (14, 20, 27).
6. Antenna according to one of Claims 1 to 4, characterized in that the second conductor track structure part (15', 21') is of asymmetrical design with respect to the first conductor track structure part (14, 20).
7. Antenna according to one of the preceding claims, characterized in that the first conductor track structure part (14) has a connecting element (19) in the end region lying opposite the second conductor track structure part (15, 15', 16, 16').
8. Antenna according to Claim 7, characterized in that the first conductor track structure part (14) has two conductor track sections (17, 18), wherein the first conductor track section (17) is capacitively loaded at one end by the second conductor track structure part (15, 15', 16, 16'), and the second conductor track section (18) connects the other end of the first conductor track section (17) to the connecting element (19).
9. Antenna according to one of Claims 1 to 7, characterized in that the first conductor track structure part (20, 27) is capacitively loaded at both ends by a second conductor track structure part (21, 21', 22, 22'; 23, 28).
10. Antenna according to one of the preceding claims, characterized in that the first conductor track structure part (14) of the first conductor track structure (12) has a connecting element (19) at one end, and the first conductor track structure part (20, 27) of the further conductor track structure (13, 26) has a second conductor track structure part (21, 21', 22, 22', 23, 28) as a capacitive load at both ends.
11. Antenna according to one of the preceding claims, characterized in that a respective first conductor track structure part (14, 20, 27) of the first conductor track structure (12) and a respective first conductor track structure part (14, 20, 27) of the further conductor track structure (13, 26) are oriented essentially parallel to one another.
12. Communications terminal (1) having an antenna according to one of Claims 1 to 11.
13. Communications terminal according to Claim 12, characterized in that the terminal is a mobile phone (1) .

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