EP2293381B1 - Antenna assembly - Google Patents

Description

The present invention relates to an antenna assembly comprising a printed circuit board and an antenna carried by the printed circuit board.

Such antenna arrangements are basically known and are used, for example, as transmitting antennas in hand transmitters or electronic keys with which, for example, Motor vehicles can be locked and unlocked remotely or garage doors can be opened and closed.

WO 2004/034512 A1 discloses an antenna arrangement according to the preamble of claim 1. US 2007/0279879 A1 discloses a similar antenna arrangement.

US 2006/0238421 A1 discloses an antenna assembly having an antenna portion disposed on an upper side and an underside of a printed circuit board, wherein the upper and lower antenna portions are electrically connected to one another by a plurality of vias.
GB 2 357 905 A and DE 196 14 362 C1 each reveal similar antenna arrangements.

The known antenna arrangements prove to be disadvantageous in that they have a comparatively low antenna efficiency. That is, the useful transmission power radiated by the antenna is relatively small compared to the power consumption of the antenna required for this purpose.

In the case of the known antenna arrangements, this generally leads to a short range and to a high energy requirement of the antenna or to a correspondingly short battery life.

The present invention is therefore based on the object to provide an antenna arrangement of the type mentioned, which has an increased antenna efficiency.

To solve this problem, an antenna arrangement with the features of claim 1 is provided.

The antenna arrangement according to the invention comprises a printed circuit board which has an upper side and a lower side, and an antenna, in particular a ring antenna, which is supported by the printed circuit board and which comprises at least one electrically conductive antenna section which is arranged on a narrow side of the printed circuit board which adjoins the upper side and / or lower side is.

According to the invention, it has been recognized that the efficiency of the antenna arrangement is impaired, in particular, by line losses in the line path of the antenna and by dielectric losses in the dielectric material of the circuit board. By arranging an antenna section on the narrow side, it is possible to reduce the line losses occurring during operation of the antenna and thus to increase the antenna efficiency.

The reason for the problem of high line losses is not least the skin effect, which is particularly pronounced at frequencies suitable for the operation of the antenna arrangement. The skin effect refers to the phenomenon that an alternating current flowing inside a conductor increasingly counteracts eddy currents that are induced by the alternating current inside the conductor and thus reduce the net current flow, so that the current flow from the center of the conductor to the edge the head is relocated. As a result, at high frequencies, essentially only the edge of the conductor contributes to the current conduction, and the effective resistance of the conductor increases.

In addition, an arranged on the top or bottom of the circuit board conductor in the edge region in which it is in contact with the top or bottom, the power is not very efficient conducts, because the surface of the circuit board and thus also the conductor in this edge region usually have a high roughness and the current path is extended accordingly in this area.

The dielectric losses occur in the circuit board carrying the antenna and thus depend on the dielectric loss properties of the materials forming the circuit board. In the context of the invention, the printed circuit board carrying the antenna preferably consists entirely of electrically nonconductive, dielectric material. For example, the circuit board may be laminated from a plurality of dielectric layers.

The inventive construction of a conductive antenna section on a narrow side of the circuit board creates an electrical current path with good power line properties and thus reduces the line losses incurred by the antenna.

An advantage of a narrow side mounted conductive antenna section here is that the antenna section itself does not take up space on the top or bottom. Thus, even with little space on the top and bottom of the circuit board, a relatively large electrically conductive antenna section can be realized and thus increased conductivity of the antenna can be achieved.

A narrow-side antenna section is particularly advantageous if the antenna is an annular antenna and has a current path which extends at least substantially annularly in the plane of the printed circuit board. A narrow-side antenna section here has at least approximately the shape of a jacket segment, resulting in a particularly good Abstrahlscharakteristik leads and contributes to increased antenna efficiency.

As a result, the antenna arrangement according to the invention thus has an improved antenna efficiency, which ultimately not only increases the antenna range, but also the energy consumption is reduced.

Advantageous embodiments of the invention are described in the subclaims, the description and the drawings.

The arranged on the narrow side conductive antenna portion preferably comprises a metallic material, in particular copper or gold. The conductive narrow-side antenna section is preferably a metallic layer, arranged on the narrow side, with a substantially constant thickness, which is, for example, several 10 μm.

According to one embodiment, the narrow side of the printed circuit board adjoins the upper side and / or the lower side of the printed circuit board. The narrow side may extend substantially perpendicular to the top or bottom of the circuit board. It is preferable if the narrow side extends from the upper side to the lower side of the printed circuit board and thus thus through the printed circuit board. In this case, the narrow side provides a particularly large area for the arranged on the narrow side antenna section.

The narrow side defines a hole extending through the printed circuit board through the printed circuit board, which is preferably elongate. If the narrow-side antenna section borders on a hole or an outer side of the printed circuit board, then there is less dielectric printed circuit board material in the direct vicinity of the narrow-side antenna section, whereby the dielectric losses of the electromagnetic field generated by a current flowing in the narrow-side antenna section are reduced. In addition, such narrow sides can be particularly easily formed, for example by holes are formed in the circuit board by a milling process or by the outer contour of the circuit board is cut by a milling process accordingly.

According to the invention, the narrow-side antenna section does not form a closed electrically conductive ring. The narrow side to which the antenna section is attached defines a hole of the circuit board, and the antenna section is attached only to a portion of the narrow side defining the hole without forming a closed ring in the hole. Such a narrow-side antenna section can be produced in a simple manner by completely coating a narrow side delimiting a hole with electrically conductive material and subsequently removing unwanted electrically conductive material.

Although an antenna arrangement is conceivable which has only a narrow-side antenna section and no upper or lower-side antenna sections, the antenna section arranged on the narrow side is connected according to the invention with an antenna section running on the upper side and with an antenna section running on the lower side. By providing the narrow-side antenna section in addition to an antenna section connected to the narrow-side antenna section and extending on the upper and lower side, the conductivity of the entire arrangement is markedly increased.

The narrow-side antenna section may be connected along its at least approximately entire length to the antenna section running on the upper or lower side.

According to a further embodiment, two narrow-side antenna sections are connected on opposite sides of an antenna section running on the top side or of an antenna section running on the underside. The two narrow-side and the upper and / or lower-side antenna section thus form two angles, in the peaks of which higher currents can flow, whereby the conductivity of the antenna section as a whole is increased even further.

According to the invention, the antenna section arranged on the narrow side extends through the printed circuit board and connects an antenna section arranged on the upper side of the printed circuit board to an antenna section arranged on the lower side of the printed circuit board. By virtue of this arrangement, two antenna section angles are also formed, in the peaks of which higher currents can flow and which contribute to increased antenna efficiency.

According to the invention, an upper-side and a lower-side antenna section are interconnected by two opposite narrow-side antenna sections. In this way, four antenna section angles are formed and an even higher current flow and antenna efficiency are achieved.

According to a further embodiment, it is provided that the antenna section arranged on the narrow side interrupts one of the top side and bottom side of the printed circuit board first antenna section electrically bridged. In this case, the narrow-side antenna section additionally connect the first antenna section to a second antenna section extending on the lower or upper side.

An interruption of the antenna portion of the top or bottom of the circuit board may serve to accommodate other circuit parts mounted on the top or bottom of the circuit board, such as an interconnect passing through the interruption to interconnect various circuit parts or components.

Thus, in addition to the antenna, the circuit board may carry other circuit parts, e.g. be made in common process steps with the antenna, for example, connecting lines and pads for more arranged on the circuit board circuit parts.

In this case, antenna sections arranged on the top and / or bottom side of the printed circuit board can be connected in a common process step with the further circuit parts, such as e.g. Connecting lines and pads are formed.

Such further circuit parts may, for example, belong to a drive circuit which applies a drive signal to the antenna mounted on the printed circuit board or, in the case of a receive antenna, to a receive and evaluate circuit. In the case of a transmitting antenna, the antenna is preferably driven with frequencies in the range between 300 and 1000 MHz.

Another object of the invention is a method having the features of claim 3. The inventive method may in particular for producing an antenna arrangement of the type described above. The advantages explained above thus apply accordingly.

In the method according to the invention, to form at least one antenna section, an electrically conductive material is attached to a narrow side of the printed circuit board which adjoins the upper side and / or the underside of the printed circuit board.

According to the invention, the narrow side of the circuit board is produced by removing printed circuit board material, in particular by forming a, in particular elongated, hole in the circuit board, for example by a drilling or milling process. Drilling and milling processes for printed circuit boards are known per se and can be accomplished in a simple manner with available tools and machines. Advantageously, a plurality of holes are produced in the circuit board along the desired antenna track for a plurality of narrow-side antenna sections. Known drilling or milling machines can produce such a variety of holes with high precision and high speed using an electronic layout, such as a CAD layout.

It is particularly preferred if the removal of printed circuit board material for generating the narrow side takes place in a common process step with the formation of holes for through connections between circuit parts on the upper side and circuit parts on the underside of the printed circuit board, so-called vias.

The co-generation of via holes and narrow side (s) simplifies the manufacturing process for the antenna assembly by not requiring a separate process step for removing printed circuit board material to produce the narrow side (s). The via holes and the narrow side (s) can thus be produced in particular in one and the same machine tool, without the circuit board having to be temporarily removed from the working area of the machine. The layout file for creating the via holes can be simply added to the geometric data for drilling and / or milling to create the narrow side (s).

According to an advantageous embodiment, the electrically conductive material is attached by a deposition process on the narrow side, in particular by means of a galvanic process. Electrodeposition processes can be used to produce layers of electrically conductive material on a narrow side which have high quality, high electrical conductivity and good adhesion to the printed circuit board material. Preferably, copper and / or gold is deposited and more preferably a layer is deposited with at least approximately constant thickness, which may be, for example, between 30 and 100 microns.

It is particularly preferred if the narrow sides and the side walls delimiting the via holes are simultaneously coated with electrically conductive material in a common deposition process, since this does not require a separate deposition process for generating the antenna sections on the narrow sides.

Preferably, electrically conductive material attached to the narrow sides and / or adjacent circuit board material is subsequently removed in regions, for example by a milling process.

In this way, unneeded electrically conductive material can be removed, e.g. electrically conductive material, which faces away from the antenna section, or reduce the weight and space requirement of the circuit board. In addition, the removal of printed circuit board material can reduce dielectric losses.

Fig. 1a

eine Leiterplattenanordnung nach dem Bohren von Via-Löchern;

Fig. 1b

eine Querschnittsansicht entlang der Linie A-A' von Fig. 1 a;

Fig. 2a

die Anordnung von Fig. 1 nach dem Fräsen von Lang-löchern;

Fig. 2b

eine Querschnittsansicht entlang der Linie A-A' von Fig. 2a;

Fig. 3a

die Anordnung von Fig. 2 nach dem Beschichten der Löcher mit leitfähigem Material;

Fig. 3b

eine Querschnittsansicht entlang der Linie A-A' von Fig. 3a;

Fig. 4a

die Anordnung von Fig. 3 nach dem Strukturieren von Leiterbahnen;

Fig. 4b

eine Querschnittsansicht entlang der Linie A-A' von Fig. 4a;

Fig. 4c

eine Rückseitenansicht der Anordnung von Fig. 4a;

Fig. 5

eine Zuschneidetrajektorie, entlang der die Leiterplattenanordnung von Fig. 4 zugeschnitten wird;

Fig. 6a

eine erfindungsgemäße Antennenanordnung, die durch das Verfahren von Fig. 1-5 hergestellt worden ist;

Fig. 6b

eine Querschnittsansicht der Antennenanordnung von Fig. 6a entlang der Linie A-A' von Fig. 6a.

According to the invention, the narrow side can be created by forming a hole in the circuit board and removed after metallization of the narrow side circuit board material extending between the hole and an outside of the circuit board so that the narrow side itself becomes the outside of the circuit board. Thus, the outer contour of the printed circuit board is reduced by cutting until the narrow side becomes the outer side of the printed circuit board. This cutting of the printed circuit board towards the narrow side reduces the space requirement of the printed circuit board and the occurring dielectric losses. Since the narrow-side antenna section extends at least partially along the outer contour of the printed circuit board, a maximum antenna length or a maximum antenna diameter is also achieved for a given size. Hereinafter, the present invention will be described purely by way of example with reference to an advantageous embodiment with reference to the accompanying drawings. Show it:

Fig. 1a

a printed circuit board assembly after drilling via holes;

Fig. 1b

a cross-sectional view along the line AA 'of Fig. 1 a;

Fig. 2a

the arrangement of Fig. 1 after milling long holes;

Fig. 2b

a cross-sectional view along the line AA 'of Fig. 2a ;

Fig. 3a

the arrangement of Fig. 2 after coating the holes with conductive material;

Fig. 3b

a cross-sectional view along the line AA 'of Fig. 3a ;

Fig. 4a

the arrangement of Fig. 3 after structuring of printed conductors;

Fig. 4b

a cross-sectional view along the line AA 'of Fig. 4a ;

Fig. 4c

a rear view of the arrangement of Fig. 4a ;

Fig. 5

a cutting trajectory along which the printed circuit board assembly of Fig. 4 is tailored;

Fig. 6a

an antenna arrangement according to the invention, by the method of Fig. 1-5 has been prepared;

Fig. 6b

a cross-sectional view of the antenna assembly of Fig. 6a along the line AA 'of Fig. 6a ,

Fig. 1 to 6 show an antenna arrangement according to the invention in different stages of their production.

Fig. 1a shows a plan view of the top of a circuit board 10, which comprises an upper and a lower side, on each of which a copper layer 14 has been applied. Fig. 1a shows holes 12 for through-connections 22 (vias, see Fig. 3 to 6 ) between circuit parts on the upper side and circuit parts on the underside of the printed circuit board 10. The via holes 12 can be produced, for example, by a drilling or milling process. Side walls 11 of the printed circuit board 10 delimit the via holes 12.

Fig. 1b shows the circuit board 10 of Fig. 1a in a cross section along the line AA 'of Fig. 1a , In addition to a via hole 12, the copper layers 14, 14 'can be seen, which are respectively applied to the top side and the bottom side of the printed circuit board 10. In Fig. 1b and also in the other cross-sectional views, the thickness s of the copper layers 14, 14 'compared to the thickness d of the printed circuit board 10 is exaggerated. The thickness d of the printed circuit board 10 may for example be about 1.5 mm and the thickness s of the copper layers 14, 14 'each about 50 microns.

Fig. 2a shows the circuit board 10 of Fig. 1 after slots 16 have been created in the circuit board 10. The elongated holes 16 extend along desired antenna conductor tracks and are bounded in each case circumferentially by a narrow side 18 of the printed circuit board 10. In each case, two elongated holes 16 run parallel to one another on opposite sides of an antenna conductor track, so that an elongate cantilevered web 19 of the printed circuit board is formed by two adjacent oblong holes 16 10 is limited, which can wear a top and bottom antenna section 24, 24 '.

In the present embodiment, the slots 16 are produced by a milling process. The elongated holes 16 are milled perpendicular to the top and bottom of the circuit board 10, so that the elongated holes 16 defining narrow sides 18 and the top or bottom of the circuit board 10 form a substantially right angle. The drilling process for the via holes 12 and the milling process for the elongated holes 16 can be performed in a common process step in the same machine.

After the formation of the via holes 12 and the elongated holes 16, the side walls 11 of the via holes 12 and the narrow sides 18 defined by the elongated holes 16 are coated by a deposition process with a conductive material, in the present embodiment with copper.

Fig. 3a shows a plan view of the arrangement of Fig. 2a after the deposition, which can be done in a conventional manner by galvanization in a galvanic bath. The thickness of the deposited copper material may be several tens of microns, for example.

The deposited on the narrow sides 18 copper material forms on the one hand narrow-side antenna sections 20 and the other unwanted or unneeded copper material 20 ', namely in the areas of the slots 16 delimiting narrow sides 18 which are remote from the desired narrow-side antenna section 20. In addition, the deposited in the via holes 12 copper forms the through-connections 22 (vias).

Fig. 3b shows that the cross section of a free-carrying printed circuit board web 19 is surrounded by conductive material all around, namely the copper layers 14, 14 'and the narrow-side antenna sections 20. The conductive material 14, 14', 20 surrounding the free-standing web 19 forms by its geometry an antenna current path with increased conductivity.

After the deposition of the conductive material, the copper layer 14 on the upper side and the copper layer 14 'on the underside of the printed circuit board 10 are patterned in a suitable manner, for example by an etching process known per se, on the upper side and the lower side of the printed circuit board 10 electrically conductive antenna sections 24, 24 'as well as electrical connection lines 28 and electrical pads 26 for in addition to the antenna on the circuit board 10 to produce circuit parts ( Fig. 4 ).

Fig. 4a, b . c show the printed circuit board 10 after patterning the copper layers 14, 14 '. For better orientation, the view on the underside of the circuit board 10 in Fig. 4c from the perspective of the top, so viewed from the top through the circuit board 10 through, shown so that it is easy to see which elements on the top of the circuit board 10 which elements on the underside of the circuit board 10 are opposite, without the viewer the mirror-inverted perspective must take into account, which arises when looking at the circuit board 10 once from above and once from below.

As Fig. 4a shows, on the upper side of the circuit board 10, an approximately annular antenna portion 24 is formed, which extends in regions along the narrow sides 18 of the slots 16 and thereby with the on the narrow sides 18 deposited conductive material of the narrow-side antenna sections 20 is in electrical contact. The antenna section 24 opposite on the underside of the printed circuit board 10, a substantially identical ausgestalteter antenna section 24 'is formed, which is also in communication with the conductive material of the narrow-side antenna portion 20. The two antenna sections 24, 24 'on the top and the bottom are as in Fig. 4b shown connected via the narrow-side antenna sections 20 with each other.

The antenna conductor tracks 24, 24 'on the upper and lower sides of the printed circuit board 10 together with the narrow-side antenna sections 20 form a substantially annular antenna which, in particular in the region of the cantilevered webs 19, increases the conductivity due to the conductive material deposited on the narrow sides 18 dielectric losses due to the formation of the elongated holes 16 in the dielectric material of the printed circuit board 10 has.

In Fig. 4a a plurality of electrical connection surfaces 26 produced in the structuring step and electrical connection lines 28 are shown. These pads 26 and connecting lines 28 allow to attach electronic components for forming a driving circuit for driving the antenna on the printed circuit board 10. The antenna is connected to the drive circuit via the connection surface 26a and via a connection surface 26b located on the back side of the circuit board 10, which serves as the reference potential for the circuit.

To form the drive circuit, electronic components, for example SMD components, can be used in a manner known per se attached to the pads 26 and interconnected via the electrical connection lines 28. As Fig. 4a, b and c In this case, circuit parts on the upper side of the printed circuit board 10 are connected to one another by the interconnections 22 produced before the patterning process. The assembly of the components for forming the drive circuit can be carried out before or after a trimming step following the structuring step or also between two sub-steps of the trimming step. The trimming step is explained below.

After patterning, the printed circuit board 10 is cut to the desired size of the antenna array. Fig. 5 schematically shows the cutting lines 30a, b, along which the circuit board 10 is cut. By the cutting line 30a, the outer contour of the circuit board 10 is defined so that the cutting line 30a adjacent narrow-side antenna portions 20 of the outer slots 16 now form the outer sides of the circuit board 10 and portions of the antenna sections 24, 24 'on the top and bottom directly to the Outside of the circuit board 10 adjacent. Unnecessary electrically conductive material 20 'and unnecessary printed circuit board material is removed in this case.

Instead of cutting the outer contour of the printed circuit board 10 all around, ie after a closed cutting line such as the cutting line 30a, the outer contour of the printed circuit board 10 can also be cut by passing printed circuit board material extending between an outer slot 16 and an outer side of the printed circuit board 10 two cut out between the outside of the circuit board 10 and the slot 16 guided cuts. In this case, the printed circuit board 10 can preferably be roughly cut to an outer contour, which is something before the structuring of the copper layers 14, 14 ' greater than its gage, so that thin webs of the circuit board 10 remain, extending between the outer slots 16 and the outside of the circuit board 10. These are then cut out in a further trimming step following the structuring.

In addition, unwanted deposited electrically conductive material 20 'is removed by the cutting lines 30b at the inner elongated holes 16. In this case, if necessary, printed circuit board material located around the unwanted electrically conductive material 20 'is also removed.

Fig. 6a and b show the finished antenna assembly after cutting. In this antenna arrangement, the electrical conductivity of the antenna is increased by the narrow-side antenna sections 20, and the dielectric losses are reduced by the removal of dielectric material. By using outer narrow sides 18 of the printed circuit board 10 for narrow-side sections 20 of the antenna, moreover, a maximum antenna diameter is achieved with a minimum space requirement of the antenna arrangement.

LIST OF REFERENCE NUMBERS

10

circuit board

11

Side wall

12

Via-hole

14, 14 '

copper layer

16

Long hole

18

narrow side

19

cantilevered bridge

20

narrow-sided antenna section

20 '

unneeded electrically conductive material

22

Through connection (Via)

24, 24 '

antenna section

26, a, b

electrical connection surface

28

electrical connection line

30a, b

cutting line

s

Thickness of the copper layer

d

Thickness of the printed circuit board

Claims (8)

1. Antenna assembly with a printed circuit board (10) having an upper side and lower side, and an antenna (20, 24, 24') carried by the circuit board (10) which comprises at least one electrically conductive antenna section (20), characterized in that
   a first antenna section (20) is arranged on a first narrow side (18) of the circuit board (10) adjoining the upper side and/or the lower side, wherein the first narrow side (18) bounds a hole (16) of the circuit board (10) and the first antenna section (20) is arranged only in a portion of the narrow side (18) bounding the hole (16) without forming a closed ring in the plane of the circuit board (10) within the hole (16),
   the first narrow side (18) is formed by a cantilevered section (19) of the circuit board (10) which comprises a second narrow side (18) opposite the first narrow side (18) forming an outside of the circuit board (10), wherein a second antenna section (20) is arranged at the second narrow side (18), and
   the first antenna section (20) and the second antenna section (20), together with antenna sections (24, 24') arranged on the upper side and lower side of the cantilevered section (19), form an annular antenna transverse to the plane of the circuit board.
2. Antenna assembly according to claim 1,
   characterized in that
   the first narrow side (18) bounds an elongated hole (16) of the circuit board (10).
3. A method for manufacturing an antenna assembly with a printed circuit board (10) having an upper side and lower side, and an antenna (20, 24, 24') carried by the circuit board (10), in which method an electrically conductive material is provided at narrow sides (18) of the circuit board (10) adjoining the upper side and/or the lower side for forming of antenna sections (20), wherein the narrow sides (18) of the circuit board (10) are created by removing circuit board material by forming holes (16) in the circuit board (10) by means of a drilling or milling operation,
   characterized in that
   the method is performed so that
   a first antenna section (20) of the manufactured antenna assembly is arranged only at a portion of the narrow side (18) bounding a first hole (16) without forming a closed ring in the plane of the circuit board (10) within the first hole (16),
   a second antenna section (20) is arranged at a second narrow side (18) of the circuit board (10) opposite the first narrow side (18), wherein the second narrow side (18) bounds a second hole (16) of the circuit board (10),
   following the attachment of the electrically conductive material at the first and second narrow side (18) material of the circuit board is removed in some areas, which extends between the second hole (16) and an outside of the circuit board (10) so that the second narrow side (18) itself becomes the outside of the circuit board (10).
4. The method according to claim 3,
   characterized in that
   the first hole and/or the second hole (16) are/is an elongated hole (16).
5. The method according to claim 3 or 4,
   characterized in that
   the removal of circuit board material for forming the narrow sides (18) is carried out in a common process step with formation of holes (12) for through-connections (22) between circuit parts (26, 28) on the upper side and the lower side of the circuit board (10).
6. A method according to any of the claims 3 to 5,
   characterized in that
   the electrically conductive material is applied on the narrow sides (18) by a deposition process in particular by means of a galvanic process.
7. A method according to claim 6,
   characterized in that
   in the deposition process at the same time the narrow sides (18) and the side walls (11), which bound holes (12) for through-connections (22) between circuit parts (26, 28) on the upper side and the lower side of the circuit board (10), are coated with electrically conductive material.
8. A method according to any of the claims 3 to 7,
   characterized in that
   electrically conductive material applied on a narrow side (18) and/or adjoining circuit board material is removed in some areas, in particular by a milling process.

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