EP0818847A2 - Antenna construction - Google Patents

Abstract

The antenna has a metal surface (1) and a resonator element (5) in the form of an L-shaped plate mounted at a distance from the plate. A short end (5.1) of the resonator is at a first defined distance (A1) from an extension of the metal surface, and a long end (5.2) is at a second defined distance (A2) perpendicularly from the metal surface. The first defined distance is greater than the second defined distance. The gap (A2) between the long end of the resonator and inside of the metal surface may be varied.

Description

Technical field

The invention relates to an antenna construction, in particular for handheld radios, and a handheld radio with such an antenna construction.

State of the art

The cell phones currently available on the market have the GSM standard predominantly an external antenna, which mostly functions as a λ / 4 monopole. It is known that the space required for the antenna (in particular the length) is reduced can be, if the antenna is wound into a helix. In combination with an extendable monopole antenna is capable of this construction in purely electrical View of the big requirements of the GSM standard regarding bandwidth and Efficiency enough. To increase comfort, reduce the risk of damage and improving the design options, it is desirable that the antenna can be completely housed in the housing. For applications with low bandwidth and radiated power requirements (e.g. for cordless phones according to the DECT standard) antennas already exist are integrated in the housing. However, these known antenna designs are for GSM specifications not suitable.

Presentation of the invention

The object of the invention is to provide an antenna construction that is small Has space requirements (and can therefore be integrated into flat housings) and which is suitable for higher bandwidths and services (such as those used by GSM are prescribed).

The solution according to the invention is defined by the features of claim 1. As a result, the antenna is essentially replaced by one serving as a base plate Metal surface and an L-shaped plate acting as a resonator element educated. The L-shaped plate is guided at a distance around an edge of the metal surface. That is, a short leg of the plate ends at a predetermined first distance A1 with respect to a direction "beyond" the edge lying in the plane of the metal surface. A long leg of the plate is at a predetermined second (middle) distance A2 held "over" the metal surface. The said second leg typically runs more or less parallel to the metal surface.

The transition between the long and the short leg can be angular or round be trained. The distance A2 between the resonator element and the metal surface however, need not be the same at every point. Resonator element and Metal surface can e.g. B. slightly curved or at a small angle to each other stand. Furthermore, the distance mentioned can vary locally. Overall, he is moving within a given range or varies around a certain mean around. The resonator element can therefore be an inside of a device housing be formally adapted. It also does not bother when electronic components are removed from the Protrude metal surface.

The inventive design and placement of the resonator element does it possible, the height (in a direction perpendicular to the metal surface) - without essential Loss of bandwidth - to minimize. In this sense, the distance A2 becomes smaller chosen as the distance A1.

A short-circuit element provided between the metal surface and the resonator element is essentially in the direction defined by the extension of the metal surface Level led. It can e.g. B. run straight in an extension of the metal surface. But it can also - especially with the variant explained below with the "Box" volume - thanks to a connecting tab that is perpendicular to the metal surface be educated.

The supply runs essentially parallel to the short-circuit element from the metal surface out to the resonator element. The exact starting point (location) of the feed and in particular their distance from the short-circuit element can be varied in order to achieve the desired adaptation of the antenna according to the invention. Starting point and distance are to be determined in individual cases and can be optimized as required will.

According to a particularly preferred embodiment, the metal surface defines box-shaped volume. The resonator element according to the invention is at a distance from one (preferably face) edge of the box-shaped volume. Its mechanical support can u. U. alone by the asymmetrically arranged Short circuit element take place. Depending on the type of supply, this may also be possible contribute to stabilization. The construction becomes particularly stable when using a dielectric support body or when attaching the resonator element to a plastic housing surrounding the antenna.

The metal surface can also be formed by the metallization of a printed circuit board. On this circuit board are also the electronic components of the circuit (transmitter, receiver, Control, data processing). The short-circuit element is z. B. formed by a soldered or clamped tab (which in the by the PCB defined level can be). It can also be preferably by a printed, flat metallization can be formed directly on the circuit board. The feed is then z. B. as a microstrip line on the circuit board from the circuit to Resonator element performed on the board.

The box-shaped volume is preferably enclosed on all sides by the metal surface. A circuit located in the volume is efficiently shielded. For the application for cellular phones, the volume is as flat as possible sought. However, applications are also conceivable in which it is not primarily based on a volume of low height arrives. It is of course not mandatory that the volume is enclosed on all sides. Narrow and end faces can be partial or be fully open.

Any more or less cuboid volume can be understood as a box-shaped volume be (cigarette box shape). The edges can be square or rounded be. The different side surfaces do not have to be parallel to each other. You can e.g. B. designed according to the formal specifications of the design Outer housing of the radio telephone may be inclined or curved.

The surface formed by the metal surface comprises e.g. B. two oblong rectangular Main areas (in - a small mutual in relation to the transverse dimension Distance) and at least one short connecting face. The resonator element covers the named end face and an adjacent area of one Main area (of course, while maintaining a certain distance). For Feeding the antenna is e.g. B. an inner conductor of a coaxial line (or a microstrip line) led through the metal surface to the edge of the resonator element. The short leg of the resonator plate can be connected to the metal surface angled) tab are fed. The short-circuit element can be a connecting strip be in an extension of a narrow side of the box-shaped Volume lies. In order for the resonance condition to be met, the short-circuit element must be be arranged in the region of a corner of the resonator plate. Supply and short circuit can be in the same or different (e.g. perpendicular to each other standing) levels.

The resonator element should be at a smaller distance from the main surface than from short connecting face. While the first mentioned distance also determines for the overall height of the (to be designed as flat as possible for design reasons) Handheld radio, the second distance only goes into the (not particularly critical) longitudinal dimension.

It is quite possible to have a dielectric between the resonator element and the metal surface Insert body. It can be used in particular for the stabilization of the resonator element to be helpful. The body can e.g. B. an L-shaped angled substrate with a selectively applied metal coating (to form the resonator plate, supply and short circuit).

The antenna according to the invention can also be designed such that the resonator element with the short-circuit element and five flat pieces of the box-shaped Metal surface consists of a piece of partially metallized plastic. The plastic part need not be completely metallized. The non-metallized parts can contribute to mechanical strength. The attached circuit board with the electronic Components and the printed die form complete the metal surface on the one hand to a closed surface of a box and on the other hand closes it Resonator element to the supply voltage.

Another advantageous embodiment variant is that the resonator element on the inside of the plastic housing of the mobile phone or on one flexible film or a thin circuit board substrate is applied. The mechanical Support then of course does not have to be taken over by the short-circuit element will.

The resonator element has a circumference corresponding to half a wavelength λ of the resonance vibration. Since the resonance-active length of the resonator element should be approximately λ / 4 (resonance condition), the short-circuit element should therefore be placed in the corner if possible. The box-shaped volume can e.g. B. have a dimension of 0.33 x 0.15 x 0.015 λ ³ . The distance between the connecting end face and the angled part of the resonator element can e.g. B. 0.03 λ. The distance to the main surface is z. B. just about 0.01 λ.

Further advantageous embodiments and combinations of features result from the following detailed description and the entirety of the claims.

Brief description of the drawings

Fig. 1a

Eine schematische perspektivische Darstellung einer erfindungsgemässen Antenne;

Fig. 1b

eine schematische Darstellung einer alternativen Art des Antennenanschlusses;

Fig. 1c

eine schematische Darstellung einer alternativen Ausführung des Resonatorelements;

Fig. 2

eine perspektivische Darstellung eines Konstruktionselementes bestehend aus dielektrischem Substrat und Resonatorelement;

Fig. 3

eine schematische Darstellung einer Stanzform zur Herstellung eines Resonatorelements aus einem Stück Blech;

Fig. 4

eine schematische Darstellung einer erfindungsgemässen Antennenkonstruktion für eine bestückte Leiterplatte in der Seitenansicht;

Fig. 5a bis c

eine schematische Darstellung eines möglichen konstruktiven Aufbaus der Ausführungsform gemäss Fig. 1a.

The drawings used to explain the exemplary embodiments show:

Fig. 1a

A schematic perspective view of an antenna according to the invention;

Fig. 1b

a schematic representation of an alternative type of antenna connection;

Fig. 1c

a schematic representation of an alternative embodiment of the resonator element;

Fig. 2

a perspective view of a construction element consisting of a dielectric substrate and resonator element;

Fig. 3

a schematic representation of a die for producing a resonator element from a piece of sheet metal;

Fig. 4

a schematic representation of an inventive antenna construction for an assembled circuit board in a side view;

5a to c

a schematic representation of a possible structural design of the embodiment according to FIG. 1a.

In principle, the same parts are provided with the same reference symbols in the figures.

Ways of Carrying Out the Invention

Fig. 1a shows a box-shaped metal surface 1 with two parallel to each other at a short distance arranged main surfaces 1.1, 1.2, an upper and a lower short End face 1.3 or 1.4 and two long narrow side faces 1.5, 1.6. The shape is comparable to that of an elongated flat cigarette box.

At a certain distance from edge 2 (which between main surface 1.2 and End face 1.3 is formed) an L-shaped angled resonator element 5 is held. To support a short-circuit element 4 and - depending on the mechanical Execution - possibly serve a feed.

The width of the resonator element corresponds to that of the main surface 1.2. A angled short side 5.1 is slightly larger than the end face 1.3 (accordingly the distance A2 between resonator element 5 and main surface 1.2). The said short side 5.1 has a distance A1 from the end face 1.3 and ends approximately in the Extension of a geometric plane defined by the main surface 1.1. The Long side 5.2 preferably angled by 90 ° covers the uppermost area the main area 1.2.

The short-circuit element 4 is, for. B. a strip-shaped extension of the side surface 1.5. It can be as wide as the mentioned side surface 1.5 or narrower.

Power is supplied from the shielded volume. For this purpose e.g. B. a microstrip 3.1 (or an inner conductor of a coaxial line) through the End face 1.3 led to the short side 5.1. The supply is in the range of Main surface 1.1 or the side surface 1.5 arranged (the distance from the short-circuit element 3.1 is determined by the required adjustment). The circuit for Control of the antenna is in the flat formed within the metal surface 1 Volume housed. The metal surface 1 thus forms the shield housing Circuit electronics.

The supply (microstrip line 3.1) is more or in the example shown less in the geometric plane and formed by the main surface 1.1 closes at the edge or near the edge of the angled short side 5.1 of the resonator element 5.

The variant shown in FIG. 1b differs from FIG. 1a with regard to the feed and the positioning of the short-circuit element 4. The microstrip line 3.1 (or an inner conductor of a coaxial line) is connected to a tab 3.2, which is essentially perpendicular to the short side 5.1 and protrudes towards the end face 1.3. The short-circuit element 4 is not in the extension of the side surface 1.5, but in the extension of the main area 1.1. The feed (tab 3.2 and microstrip line 3.1) and the short-circuit element 4 are in one spaced from each other by the desired adjustment.

1c shows a further alternative in which the resonator element is rounded is. The transition between the long side 5.2 and the short side 5.1 is not here by a pronounced edge, but by a continuously curved or curved transition formed. The radius of curvature is of the order of magnitude the distances A1 and A2. Experiments have shown that round transitions to one can lead to a wider range. Is the bandwidth - by replacing the square resonator element by a round - too large, it can by a reduction in the distance A1 or A2 can be reduced again. The thickness (or Overall height) of the entire antenna construction can be achieved by using rounded Resonator elements are advantageously kept small.

In the example according to FIG. 1c, the short circuit 4 is positioned similar to that in FIG. 1b. The In contrast, feeding takes place through a microstrip line 3.1 in an extension of the Side surface 1.5. FIGS. 1a to 1c are therefore different variants for the Placement of short circuit and supply can be seen. Of course, too other arrangements possible according to the required distance between these two elements.

The dimensions of the metal box are e.g. B. as follows: L = 0.33 λ, B = 0.15 λ and D = 0.015 λ. (In the present example, the thickness D is 1/10 of the width B or approximately 1/20 of length L.) The distance between the end face 1.3 and the short side 5.1 is z. B. 0.03 λ, that between the long side 5.2 and the main surface 1.2 about 0.01 λ. The second distance is therefore a multiple (e.g. 3 times) smaller than the former. The width of the resonator element 5.1 is essentially same as the width B of the metal box. The length X1 of the short side 5.1 is z. B. 0.025 λ, while the length X2 of the long side 5.2 measures 0.07 λ. In other words, the long side is e.g. B. more than twice as long as the short side 5.1.

The distance between the supply and the short-circuit element 4 can be adjusted the antenna can be varied to the required 50 Ω input impedance. In the The dimensioning mentioned above as an example was 0.037 λ.

In the application of a GSM mobile phone, the wavelength is in the range of 30 cm.

Characterized in that the resonator element 5 is angled in the manner shown in FIG. 1a or is bent round, the height in the critical environment of the To feed and the short-circuit element 4 in the longitudinal axis of the housing, where there is more space. The larger side 5.2 of the essentially rectangular The resonator element can have a low height above the radiation-side metal surface (i.e. the main surface 1.2). The box-shaped metal surface 1 carries as a counterweight to the radiation and also ensures a good radiation, when the antenna element by the hand of the cellular phone user is covered.

The input impedance of the antenna according to the invention is approximately 50 Ω real. In terms of the condition that the reflection loss should be less than 10 dB achieved a bandwidth of 20%. This value lies - with good efficiency and more compact Dimension - above the corresponding requirements of the GSM standard. Outstanding is the low detunability of the antenna by the hand or the head of the Phone user. As an antenna in the medium of air, it has exceptional efficiency of over 90% and largely independent of the radiated power (up to 2 watts for GSM). Nevertheless, the geometric dimensions are small and optimally adapted for integration into a handheld device. The radiation diagram points a predominantly omnidirectional characteristic. The following are some simple ones and inexpensive antenna designs are described.

Fig. 2 shows a dielectric body 6 with two perpendicular to each other Share 6.1, 6.2. On the outside of this L-shaped body 6 is an all-over Metal coating 7.1, 7.2 attached, which the resonator element 5 in Fig. 1a corresponds. On a side of the part opposite the metal coating 7.1 6.2 is a narrow strip-shaped metal coating 7.3 which the Supply (microstrip line 3.1 / tab 3.2) in Fig. 1a, 1b corresponds. On the L-shaped The side surface in the area of part 6.2 is a metal coating 7.4 as a short-circuit element attached (cf. short-circuit element 4 in Fig. 1 a).

The resonator construction shown in FIG. 2 can be placed on the outside of a suitably dimensioned shielding housing. The dimensions are such that the end result is a structure comparable to that of FIG. 1a (metal coating 7.3 aligned with a main surface of the shielding housing and metal coating 7.4 aligned with a side surface of the same). The body 6 forms a dielectric medium (ε _r > 1) and can lead to a reduction in the antenna dimensions. The resonator construction shown in FIG. 2 is mechanically stable and can also define the distances between the resonator element and the shielding housing in a defined manner without any special assembly effort.

With the same resonance frequency, the antenna can be made smaller. However, the bandwidth decreases with increasing dielectric constant ε _r . Conversely, the bandwidth and the size of the antenna can be adjusted by the appropriate choice of the material properties of the substrate.

Fig. 3 shows how the resonator element from a piece of sheet 8, which has two tabs 12, 13 for the supply or the short circuit, can be produced. The essentially rectangular sheet 8 has a bending line 9 at a suitable point, so that the sheet 8 can be bent L-shaped. The tabs 12, 13 also have over bending lines 10, 11 for right-angled turning. That so shaped Sheet metal is on the tabs 12 and 13 with the corresponding contacts on the shield housing soldered. On the soldering z. B. be dispensed with if the bent Sheet metal when assembling the mobile device between the plastic housing and the shielding housing arranged therein is clamped. Short circuit element and supply are then connected to the corresponding contacts on the shield housing pressed.

The embodiment shown in Fig. 4 represents a structurally simple variant without Shield housing. The starting point is a circuit board 14 with a metallization 15 on the back and equipped with various electronic components 16 on the front side. (In the present example, for the sake of simplicity, the mostly customary double-sided and multilayer PCB assemblies. It goes without saying that the invention condenses to such in a straightforward manner electronic circuits can be applied.) On a front edge 19 (which runs perpendicular to the plane of the drawing in the chosen representation) is over a short-circuit tab 18 is connected to a resonator plate 17 according to the invention. The feed runs in the same plane as the short-circuit tab 18 (and is therefore not visible in the representation according to FIG. 4). The short leg 17.1 So ends at a certain distance "beyond" the edge 19. The long second Leg 17.2 runs as close as possible above the (dielectric) Printed circuit board 14. The antenna is controlled by the circuit board 14 implemented circuit.

The embodiment shown in Fig. 4 can additionally by a shield housing the electronic circuit can be expanded. Then preferably resonator element and shield housing made of a metallized piece of plastic, the electrically conductive parts being formed by the partial metallization will. By folding this plastic part with the circuit board in one Process a) assembles the antenna, b) creates a contact and c) the electronic Shielded circuit.

This will be explained below with reference to FIGS. 5a to 5c. 5a shows a circuit board 20 in plan view. The rectangular area 21 in which the Components 23 of the electronic circuit are arranged by a revolving Contact strips 22 delimited against the edge of the circuit board 20. At one point the contact strip 22 is interrupted so that the microstrip conductor 24 is out of the range 21 can be brought out. The contact strip 22 is with the electrical Ground of the circuit board connected (which is e.g. on the back of the insulating Carrier is located). In the corners of the (formed in the manner of a rectangular frame) Contact strips are e.g. B. holes 25.1 to 25.4 are provided.

Fig. 5b shows a lid-like second part, the shield 26 and the resonator element 27 includes. This second part is e.g. B. by a selectively metallized Plastic molding formed. The shield 26 has four narrow sides 26.1 to 26.4 and a main surface 26.5. The main area 26.5 is approximately the same size as the area 21. The edges of the narrow sides 26.1 to 26.4 come on the contact strip 22 to lie when the plastic molded part according to FIG. 5b on the printed circuit board 20 according to Fig. 5a is placed. So a closed, box-shaped volume is formed, in which the components 23 can be accommodated.

The resonator element 27 is by the short-circuit element 28, which is on a Extension of the narrow side 26.3 lies, and optionally by an additional support element 30, which is mirror-symmetrical to the short-circuit element 28 in one Extension of the narrow side 26.1 is formed, worn. For further stabilization of the resonator element 27, a support element can be provided at the end 31 thereof be carried by the main surface 26.5.

A contact element 29 is formed on the resonator element 27 at the desired location. It can e.g. B. is a small feather. When attaching the in Fig. 5b Plastic molding shown on the side of the circuit board 20 shown in Fig. 5a the contact element 29 sits on the contact point 24.1 at the outer end of the Microstrip conductor 24. A recess 33 in the narrow side 26.4 forms an opening for the microstrip line in the shield. In the corners of the box-shaped Cover (i.e. inside the edges between the narrow sides 26.1 to 26.4) For example, posts 32.1 to 32.4 are provided, which with the holes 25.1 to 25.4 correlate and allow the two parts to be screwed together so that the in Fig. 5c shown structure arises.

If the circuit board is equipped with components on both sides, it is natural shield the "back" with a lid. The effective one for the antenna The metal surface is then this second cover (and not the mass of the circuit board). Of the said second cover is indicated in Fig. 5c by a dashed line.

The antenna designs described above can be used in various ways can be varied. So z. B. rounded the shape of the resonator element instead be rectangular or have various small indentations and tabs to to enclose or envelop protruding components. There may also be holes in the resonator element be provided, for example, larger circuit elements To make room. It is also easily conceivable that a larger number of holes is present. The diameter of a hole is usually not greater than the distance A1 or A2 mentioned above. This allows a kind Grid structure arise. Further cuts can be made in places that do not have high current flows show be provided. The angle between the smaller and the larger Part of the L-shaped resonator element can deviate from 90 ° and advantageously be rounded. For fine tuning, you can use the resonator element Extensions are formed, the length of which influence the resonance frequency.

There are also certain freedoms in the positioning of the short-circuit element. It can be the same width, wider or narrower than the side surface. It even takes not even necessarily lying in the plane of the side surface. It can e.g. B. to the Edge of one of the two main surfaces.

Is z. B. the resonator element through a copper layer on a flexible film formed (flexible circuit board), then a rounded bend is created. The foil is inserted into the plastic housing and in the correct shape held. The contacts can in turn be ensured by soldering or pressing will. (The copper layer can be coated in a manner known per se with a photochemical Procedures can be printed on the film.)

In summary, it should be noted that the antenna according to the invention is proportional has a high bandwidth of around 20% with a comparatively low overall height of a few millimeters. The antenna is not very sensitive to nearby ones Body parts (such as the hand or head of the phone user). It fulfills that Requirements of the GSM standard and allows full integration in the Plastic housing.

Claims (17)

Antenna construction, especially for handheld radios, with a metal surface (1) and a resonator element designed as an essentially L-shaped angled plate (5), which is at a distance from an edge (2) of the metal surface (1) is held that a short end (5.1) a predetermined first distance (A1) in the direction of an extension of the metal surface (1) and a long one End (5.2) a predetermined second distance (A2) perpendicular to the metal surface (1) has. Antenna construction according to claim 1, characterized in that the former Distance (A1) is greater than the second (A2). Antenna construction according to claim 1 or 2, characterized in that the Distance (A2) between the long end of the resonator element (5) and the Metal surface (1) varies within a given range. Antenna construction according to one of claims 1 to 3, characterized in that a short-circuit element (4) of the resonator element (5) essentially in an extension of a geometric one defined by the metal surface (1) Level is arranged and that a feed (3.1) essentially parallel to it is guided from the metal surface (1) to the resonator element (5). Antenna construction according to one of claims 1 to 4, characterized in that there is a mutual distance between the supply (3.1) and the short-circuit element (4) as well as the location of the feed (3.1) according to the given adaptation values are selected. Antenna construction according to one of claims 1 to 5, characterized in that that the metal surface (1) forms a surface of a box-shaped volume and that from this a line (3.1) for feeding through the metal surface (1) is led. Antenna construction according to one of claims 1 to 6, characterized in that that the resonator element (5) by an asymmetrically arranged short-circuit element (4) connected to the metal surface (1) and thereby preferably is also mechanically supported. Antenna construction according to one of claims 6 to 7, characterized in that that the box-shaped volume is enclosed on all sides by the metal surface (1) is and is preferably layered. Antenna construction according to one of claims 6 to 8, characterized in that the metal surface (1) two preferably elongated rectangular main surfaces (1.1, 1.2) and forms at least one short connecting end face (1.3), and that the resonator element (5) has said end face (1.3) and an adjacent one Covered area of one main surface (1.2). Antenna construction according to one of claims 1 to 9, characterized in that that a transition between the short end (5.1) and the long end (5.2) of the resonator element (5) is rounded. Antenna construction according to one of Claims 6 to 10, characterized in that that the short-circuit element (4) one in an extension of a narrow side (1.5) or broadside of the box-shaped volume of lying strips. Antenna construction according to one of Claims 4 to 11, characterized in that that the supply (3.1) is guided on a circuit board, which is also a carries electronic circuit. Antenna construction according to one of claims 1 to 12, characterized in that between the metal surface (1) and resonator element (5) a dielectric Body is arranged. Antenna construction according to one of claims 1 to 13, characterized in that that the resonator element (5) essentially corresponds to a scope half a wavelength (λ). Handheld radio with an antenna construction according to one of claims 1 to 14 and an electrical circuit housed in the box-shaped volume for Control of the antenna construction. Handheld radio according to claim 15, characterized in that it has a non-conductive housing, on the inside of the resonator element in Form of a metal coating, a preformed sheet or a conductive coating Foil is attached. Handheld radio according to claim 15 or 16, characterized in that a resonator element (5), a short-circuit element (4) and the metal surface (1.2 to 1.6) made from one piece, in particular from a partially metallized plastic are.

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