EP0795926B1 - Flat, three-dimensional antenna - Google Patents

Description

State of the art

With wireless communication in local area networks (LAN) occur to the usual Requirements (such as adapted input impedance, good radiation characteristics, Efficiency). So it is z. B. desired that the antenna or a Diversity antenna system has space on a PCMCIA card. With communicative Laptop computers are namely horizontal insertion slots for such cards intended. An antenna system integrated on a PCMCIA card should therefore be in Blast approximately equally well in all directions on the horizontal plane. So that one Antenna can be integrated on a card of this type, it is allowed as standard Do not exceed the permitted height. It is therefore in many frequency ranges not possible, a simple monopole antenna for the described communication use.

It is known to realize a flat three-dimensional antenna in such a way that a base plate on the first level and a controlled element on a second level are arranged.

An antenna array with patch antennas is described in US Pat. No. 5,309,164. All Antenna elements are arranged in a common vertical plane. The Patch antennas are slotted. The antenna arrangement has two slightly spaced base plates and a resonance structure in the same plane as that Patch antennas, which have the task of improving the angular selectivity.

In EP 0 226 390 A 2, inter alia, an SMA structure with three spaced planes described. The controlled element is above a base plate with two sides parts raised. There is a passive one above the controlled element Element provided to increase the bandwidth.

FR 2 552 937 shows a microstrip antenna with two structure levels, which is formed by conductor layers and metallizations.

Presentation of the invention

The object of the invention is to provide a flat, compact three-dimensional antenna, which is suitable for the wireless transmission of digital data in local networks suitable. The antenna should have an omnidirectional radiation characteristic as possible and a slight dependence of the adaptation on neighboring external objects to have.

The solution according to the invention is defined by the features of claim 1. As a result, the antenna is constructed in three levels. Located on a first level a base plate, in a second is a U-shaped slot divider and in a third arranged a resonance structure. The slot divider is in the second Level angled in a U-shape, so that a central part and two side legs are formed become. The legs of the slot divider are short-circuited to the base plate, see above that a first antenna slot is formed between the base plate and slot divider. The resonance structure is through flank elements with the legs of the slot divider short-circuited, so that a second antenna slot between slot splitter and Resonance structure is formed.

This antenna is extremely compact and radiates mainly through the base plate defined spatial directions (i.e. "horizontal"). Received through the resonance structure the antenna has an extremely wide bandwidth (e.g. 20% to 30%). This can the influence of neighboring surrounding objects can be kept small. The The existence of a conductive base plate additionally supports this advantage.

The antenna is preferably fed by a strip conductor which is in the second Level is guided between the two legs and the slot divider on the middle part contacted. The adaptation of the input impedance of the antenna can vary the width and length of the stripline. The stripline can e.g. B. the Completely fill in the area between the legs. The length of the stripline is preferably less than the length of the legs, so that not by feeding takes up more space than is already used by the antenna. But it is also possible to make the stripline longer (i.e., quasi on the second level lead out of the antenna and z. B. to reduce the width). The feeding of the Depending on the embodiment, the antenna can be via a microstrip line or a (through the base plate) coaxial line are made.

The middle part of the slot divider has z. B. the length λ / 4 (λ = wavelength at the resonance frequency). The two legs are each λ / 8 long. At the ends of the legs the slot divider is connected to the base plate. The length of the middle section can also be a little bit longer or shorter. Accordingly, the antenna becomes more or less elongated.

The resonance structure is through (electrically conductive) flank elements on the legs supported the slot divider. If the antenna is in a dielectric medium is embedded, then the mechanical support function is in principle through the dielectric Perceived medium. The flank elements can then be suitable attached metallizations to connect the resonance structure with the Slot divider. In the event that the antenna or at least the resonance structure in In principle, the whole antenna can be air by bending a plate with a suitable one Patterns are made. The resonance structure can e.g. B. a gap in the middle have, so that they by two plate-shaped mirror-symmetrical elements is formed. From an electrical point of view, the gap has no meaning, since in the middle the Resonance structure anyway there is a current node.

A first antenna slot formed between the base plate and slot divider is preferred larger than one formed between the slot divider and the resonance element second antenna slot. The length of the second antenna slot can be varied, the bandwidth of the antenna changes accordingly. In extreme cases it is possible to construct an antenna with two separate resonances (dual frequency Fashion). Conversely, the resonances can also be brought very close to one another become, which leads to a narrow bandwidth.

The antenna according to the invention can be constructed in different ways. It is conceivable, for. B. that the antenna is formed from a stamped or etched sheet and is soldered onto a base plate (e.g. a metallized circuit board) becomes. A dielectric can be present between the first and second levels of the antenna his. So z. B. the slot divider as a conductor structure on the upper side be printed on a suitably thick printed circuit board, the base plate being covered by a Metallization is formed on the back of the substrate. The resonance structure in the third level can then e.g. B. like a flat inverted U-profile (plate with two opposite flanks) are executed (the flanks on the Conductor structures are soldered).

According to a particularly preferred embodiment, the antenna is formed on a ceramic block. The resonance structure is then a metallization on a first (upper) main surface of the ceramic block. The slot divider in the second level is e.g. B. represented by a metallization on the narrow side surfaces of the ceramic block. The base plate can be formed by a metallization on the second (lower) main surface of the ceramic block or by a metal surface to which the ceramic block is soldered. A metallized slot in the ceramic block can be provided between the two main surfaces, in which the strip conductor for feeding the antenna is arranged. Such an antenna is not only extremely compact (due to the relative dielectric constant ε _r > 1), but also very robust. It can be handled and soldered on like any other electronic component (SMD = Surface Mounted Device). Due to the small size of the antenna, the risk of damage is also avoided (no antenna protruding from the housing).

To adjust the antenna is u. U. provide an inductance. This is preferred integrated in or in front of the stripline.

The antenna according to the invention is also well suited for diversity reception. This affects both spatial and angular diversity, sometimes called pattern diversity.

Remarkably, by juxtapositioning it becomes a sectoral one Achieved angular diversity. This means that each of the two antennas is in one Direction particularly sensitive, in which the other is only an extremely small one Has sensitivity. By switching or combining the two antenna feeds the performance of a receiver can be increased (diversity gain). It will z. B. switched from one antenna to the other when the signal of the former becomes too weak. Are the antenna signals additionally against each other out of phase, then the sensitivity pattern can be rotated in space.

To achieve space diversity, multiple antennas can be spaced apart (e.g. λ / 3 to λ / 2) can be set next to each other. With the one described below Antenna element can e.g. B. a 3-way space diversity antenna system be built up in a volume of 54x28x5.2 mm3 (which is an extension corresponds to a PCMCIA card).

The antenna according to the invention is particularly suitable for HIPERLAN applications and handheld cellular phones (including cordless phones). The one for such applications The intended frequency ranges are typically over 1 GHz (e.g. 5.2 GHz in the European Telecommunication Standard-HIPERLAN).

The antenna is also suitable for use in an antenna array because the wide range also allows adaptation in the vicinity of the neighboring antennas.

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. 1

Eine schematische perspektivische Darstellung einer erfindungsgemässen Antenne in Luft;

Fig. 2

eine schematische perspektivische Darstellung einer erfindungsgemässen Antenne auf einem Keramikblock;

Fig. 3

eine schematische perspektivische Darstellung der Ausführungsform gemäss Fig. 2 von hinten gesehen;

Fig. 4

eine schematische Darstellung eines Antennensystems zur Erzielung eines Diversity-Empfangs.

The drawings used to explain the exemplary embodiments show:

Fig. 1

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

Fig. 2

is a schematic perspective view of an antenna according to the invention on a ceramic block;

Fig. 3

is a schematic perspective view of the embodiment of FIG 2 seen from behind.

Fig. 4

is a schematic representation of an antenna system to achieve diversity reception.

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

Ways of Carrying Out the Invention

1 shows an antenna according to the invention in air. It is in three levels or Layers built up. The first level is defined by a base plate 1. It can a wall of a metal box or a metallization on a circuit board act.

The slot divider is on the second level. In principle, it is one U-shaped metal strips with a middle part 2 and two legs 3, 4. The The length of the middle part 2 is preferably λ / 4, that of the legs 3, 4 λ / 8th The slot divider is at the two ends of the legs 3, 4 via two legs 5, 6 short-circuited with the base plate 1.

There is a resonance structure on a third level. In the present example it is formed by two symmetrical plates 9, 10. These are vertical Side surfaces 12, 13 on the outer sides of the angled legs 3, 4 of the Slotted divider supported. The two plates 9, 10 are separated by a gap 11. From an electrical point of view, this is of no importance since it is located in a power node. How 1, it enables the antenna to be shaped a flat, suitably cut sheet metal shape.

For feeding the antenna, for. B. a strip conductor 7 is provided, which has a leg 8th is connected to a coaxial connector below the base plate 1. Is the base plate formed as a printed circuit board, a further microstrip line can also be connected to the Step in the place of the coaxial connection. The stripline fills accordingly required impedance matching the formed between the two legs 3, 4 Area completely out (being only through two gaps 14, 15 from the legs 3, 4 is separated).

Die beiden Platten 9, 10 decken im wesentlichen die vom U-förmig gebogenen Schlitzteiler aufgespannte Fläche ab. Der Abstand zwischen Resonanzstruktur und Schlitzteiler ist vorzugsweise kleiner als der Abstand zwischen dem Schlitzteiler und der Grundplatte 1. In diesem Sinn kann z. B. die zweite Ebene auf einer Höhe von 2.6 mm (λ/20) und die dritte Ebene in einer Höhe von 4.2 mm (λ/8) über der Grundplatte angeordnet sein (Mittelfrequenz f₀ = 6.4 GHz, λ ≅ 4.7 cm).

The following should be said about the dimensioning:

The two plates 9, 10 essentially cover the area spanned by the U-shaped slot divider. The distance between the resonance structure and the slot divider is preferably smaller than the distance between the slot divider and the base plate 1. B. the second level at a height of 2.6 mm (λ / 20) and the third level at a height of 4.2 mm (λ / 8) above the base plate (center frequency f ₀ = 6.4 GHz, λ ≅ 4.7 cm).

There is an antenna slot between the resonance structure and the slot divider, which is limited in length by the side surfaces 12, 13. The length of this Slot can be varied to determine the bandwidth. Are the side faces 12, 13 z. B. the same length as the legs 3, 4, then the antenna slot is the same length as the middle part 2. In principle, the vertical side surfaces 12, 13 can even around the Be led around the middle part 2. Conversely, you can only have one claim a small part of the legs 3, 4 and close to the ends or legs 5, 6 be placed. Accordingly, the upper antenna slot would be approximately the same size as the lower antenna slot between slot divider and base plate 1.

In principle, the antenna according to the invention is two stacked one on top of the other and angled λ / 2 slots with different slot lengths.

The impedance matching takes place via the dimensioning of the stripline 7 Starting with the numerical example started above, it has a width of z. B. 11 mm (0.24 λ) and a depth of z. B. 5.5 mm (0.12λ). The two legs 3, 4 each a width of e.g. B. 0.75 mm (0.015 λ). The gap 11 is z. B. 1 mm (λ / 50) wide. The entire antenna has a width of z. B. 0.28 λ and a depth of z. B. 0.14 λ.

The stripline 7 can u. May also be less wide and / or from which by the two Legs 3, 4 run out of the spanned area. In particular, it is for feeding suitable via microstrip line.

The antenna structure shown in FIG. 1 can be partially or completely embedded in a dielectric medium (of course, by adjusting the dimensions due to the higher relative dielectric constant ε _r > 1). So z. B. the slot divider (legs 3, 4, middle part 2) and the strip conductor 7 are applied as a conductor track structure on a dielectric substrate (printed circuit board). The base plate 1 can be provided as a metallization on the back of the substrate, the legs 5, 6, 8 (in the form of pins) being passed through the substrate.

In this case, the resonance structure can be a continuous rectangular plate, which in turn is electrically connected to the legs 3, 4 via side surfaces 12, 13 and are supported on the substrate at the same time. The simplest is a piece of sheet metal cut that cover a surface spanned by the legs 3, 4 capable and with side tabs to form the side surfaces 12, 13 (by right-angled Turn) is equipped. The gap 11 is in this embodiment neither necessary nor desirable (mechanical stability).

A dielectric can also be provided between the second and the third level his. This can e.g. B. by selectively laminating a dielectric material in the desired layer thickness can be achieved. The side surfaces 12, 13 can corresponding boundary surfaces of the laminated layer can be applied. The plate-shaped resonance structure can on the surface of the laminated layer be printed on.

A particularly preferred embodiment will be explained with reference to FIGS. 2 and 3 become. A ceramic block 16 is shown schematically in FIG. He has an upper one and a lower major surface 17 and 18 respectively. On the upper main surface 17 is the entire surface a metallization is provided as a resonance structure. The lower major surface 18 can also be metallized (so as to form the base plate 1 or the Easy to solder ceramic block to a base plate or a metal box).

The ceramic block 16 has two short and two long side surfaces 19, 20 or 21, 22. The slot divider is formed in that on the side surfaces 19, 21, 20 a continuous strip-like metallization to form a U-shaped circumferential Conductor is provided. The above-mentioned conductor track is shaped by a strip Area 25, 26 approximately in the middle between the two main surfaces 17, 18 educated. At the rear end (according to the illustration chosen in FIG. 2) of the side surface 19 is a metallization 24 down to the main surface 18. The electrical Connection between the resonance structure and the slot divider is also made produced by a metallization 27 provided on the side surface 19. The Side surface 20 is selectively metallized in mirror symmetry to side surface 19. It it is clear that the metallization 24 the leg 6, the metallization 25 the leg 4, the metallization 26 of the middle part 2 and the full-area metallization of the Main surface 17 corresponds to the two plates 9, 10 in FIG. 1.

What is still missing is a metallization corresponding to the strip line 7. To for this purpose, however, a flat, continuous slot 23 is provided. This extends from the side surface 21 to the side surface 22 and is, for. B. completely metallized. Then there is only one of the slots 23 on the side surface for feeding 22 down metallization 32 (see Fig. 3). The named Slit can be made in the mold before hardening or by drilling be made. But it is also conceivable that two thin ceramic blocks into one thick are connected, the stripline and possibly also the slot divider is formed between them in a flat design.

To bring the input resistance up to 50 Ω, an inductance may be required (from e.g. 1 - 2 nH). Such can be elegantly integrated. A possible variant will be explained with reference to FIG. 3. This figure shows in exaggerated perspective view of the ceramic block 16 from behind. The Slot 23 has a rectangular cross section and thus four inner surfaces 28, 29, 30, 31, which are all metallized. For feeding is now on the side surface 22 Selective metallization 32 (already mentioned) is provided. She contacts the interior of the slot 23. The inductance is now generated by the Current is first routed in a loop along the slot edge 34, 35, 36, before it can flow in the passage direction of the slot 23. To achieve this, a non-conductive linear region 33 is provided, which is the rear end the slit metallization. 3 shows a variant in which the non-conductive region 33 is approximately half the width of the inner surface 28, the whole Width of the inner surface 29 and about half the width of the inner surface 30 of the Separates metallization in the slot. The current must therefore be around half the circumference of the slot flow, which generates a corresponding inductance. The size of the inductance can can be varied simply by making the length of the non-conductive region 33 suitable is chosen.

In principle, the inductance can also be controlled by a corresponding loop Current are forced on the side surface 22. That means the electricity has to go first flow around the slot a certain amount before it goes into it becomes.

In the dielectric, the antenna becomes smaller at the same frequency. To the same time to optimize the decreasing bandwidth within the physical limits z. B. to increase the length of the upper slot (between the second and third levels). For the preferred applications, however, it is also sufficient in the dielectric Reserve available in the range. It should also be noted that the dielectric conditional losses should not be too large. In air has the invention Antenna namely a very high efficiency of over 90%. They are also ceramic materials known with very favorable tanδ values.

In general, the antenna is characterized by a wide bandwidth (in air e.g. 20% to 30%) and through a radiation with less or negligibly smaller Power perpendicular to base plate 1. Towards the base plate is a good one given omnidirectional characteristics.

An important application of the antenna according to the invention is in the range of wireless LANs (e.g. HIPERLAN). For this application, the antenna can be set to a PCMCIA card can be mounted. It is particularly advantageous to have two or more Position antennas of the type described. In this way there can be a diversity reception be realized.

To achieve space diversity, multiple antenna elements are combined in one Distance (λ / 3 to λ / 2) placed next to each other. (A space diversity effect poses itself even when the antennas touch.) An exemplary arrangement of three antennas at a distance of 0.4λ shows that the antennas are relatively little mutual influence, d. H. that each antenna largely behaves omnidirectionally maintains. The signals received by the different antennas are proportional independently of each other. In the exemplary arrangement mentioned could the antenna system in a volume of 54x28x5.2 mm3 (which an extension corresponds to a PCMCIA card).

4 shows an example of a U-shaped arrangement of three antenna elements 37, 38, 39 on an extension of a PCMCIA card 40. The adjacent antenna elements 37 and 38 or 38 and 39 are at right angles to each other placed. For reasons of space, the antenna elements 37, 38, 39 (which each z. B. as shown in Fig. 1) as close as possible to the corresponding edge the PCMCIA card 40.

To achieve angular diversity, two antennas with the narrow sides (i.e. the angled legs) directly next to each other.

In this arrangement, the two antennas have an angular selectivity that they as a single antenna (or not in a pronounced form). Depending on Which direction a strong signal comes in, the receiver can select the appropriate one Antenna can be switched. The antenna signals can also advantageously be combined become. By changing the phase of the signal from one antenna to the other The angle antenna of the other antenna can also be rotated as required.

The antenna is also suitable as an element for so-called antenna arrays. It will in this case, several individual antennas isolated or appropriately arranged in a network, to achieve a desired radiation / reception characteristic by combining their signals to reach.

However, the invention is also suitable for hand-held radio telephones (cordless telephones, GSM cell phones etc.). In the ceramic block variant in particular, the antenna can be used as compact component can be placed on top of the cell phone in order to achieve the desired radiation characteristics to show. It is even conceivable that the antenna according to the invention can be designed to receive two adjacent frequencies (dual Frequency mode).

The antenna described has a large number of advantages. In summary the following should be mentioned: large bandwidth, variability of the bandwidth, good options for impedance-based adaptation, small space requirement, omnidirectional Radiation pattern in one plane and no radiation perpendicular to Level, compatibility with a PCMCIA card (especially as a system several antenna elements) and suitability for diversity reception.

LIST OF REFERENCE NUMBERS

1 baseplate 2 midsection 3, 4 leg 5, 6 leg 7 stripline 8th leg 9, 10 plate 11 gap 12, 13 side surface 14, 15 gap 16 ceramic block 17, 18 main area 19, 20, 21, 22 side surface 23 slot 24, 25, 26, 27 metallization 28, 29, 30, 31 Inner surface 32 metallization 33 non-conductive area 34, 35, 36 slot edge 37, 38, 39 antenna element 40 PCMCIA card

Claims (13)

1. Flat, three-dimensional antenna, in which a base plate (1) is disposed in a first plane, a slot divider which is short-circuited to the base plate (1) is disposed in a second plane and a resonant structure (9, 10) is disposed above the slot divider in a third plane, characterised in that the slot divider is bent in the shape of a U and therefore forms a centre part (2) and two limbs (3, 4), wherein the limbs (3, 4) of the slot divider are short-circuited to the base plate (1) and therefore define a first antenna slot between the base plate (1) and the slot divider, and that the resonant structure (9, 10) is short-circuited by flank elements (12, 13) to the limbs (3, 4) of the slot divider, which thus define a second antenna slot between the slot divider and the resonant structure (9, 10).
2. Antenna according to Claim 1, characterised in that the slot divider is fed by a stripline (7), which is routed in the second plane between the two limbs (3, 4), in order to contact the centre part (2).
3. Antenna according to Claim 1 or 2, characterised in that the resonant structure (9, 10) is divided (11) in the centre.
4. Antenna according to any one of Claims 1 to 3, characterised in that a spacing between the base plate (1) and the slot divider (2, 3, 4) is greater than a spacing between the slot divider (2, 3, 4) and the resonant structure (9, 10), so that the first antenna slot is larger than the second antenna slot.
5. Antenna according to any one of Claims 1 to 4, characterised in that a dielectric substrate is provided between the first and the second plane.
6. Antenna according to Claim 5, characterised in that the slot divider (2, 3, 4) is applied as a conductor track layer to the substrate, that the base plate (1) is formed by metallization on the back of the substrate, and that the resonant structure is built up on the conductor track layer.
7. Antenna according to Claim 5, characterised in that it is constructed on a ceramic block (16), wherein the slot divider is formed by conductor tracks (24, 25, 26) on side faces (19, 20, 21), that the resonant structure is constructed on an upper face (17) of the ceramic block, and that a slot (23) for the feed is provided in the second plane.
8. Antenna according to Claim 7, characterised in that an inductor is integrated into the feed.
9. Antenna according to any one of Claims 1 to 8, characterised in that it can be adapted in terms of impedance by varying a width and a length of the stripline (7).
10. Antenna according to any one of Claims 4 to 9, characterised in that a bandwidth of the antenna can be varied by varying the second antenna slot.
11. Antenna array with a plurality of antennae according to any one of Claims 1 to 10.
12. PCMCIA card with preferably at least two antennae according to any one of Claims 1 to 10 for digital communication using space and/or angle diversity reception.
13. Handheld cordless telephone with at least one antenna according to any one of Claims 1 to 10.

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