WO2002054536A1

WO2002054536A1 - Antenna with a non-radiating coupling portion

Info

Publication number: WO2002054536A1
Application number: PCT/SE2001/002659
Authority: WO
Inventors: Christer Krebbs
Original assignee: Allgon Ab
Priority date: 2000-12-29
Filing date: 2001-12-03
Publication date: 2002-07-11
Also published as: SE0004906D0; SE0004906L

Abstract

The invention relates to an antenna device for use in a radio communication comprising a substantially flat structure formed by a dielectric substrate (4) with a conductive pattern on at least one surface. The antenna device comprises a radiating portion (9), and a feeding portion (10), where the conducting pattern comprises a signal conductor (1, 1a, 1b, 1c) for transmitting RF-signals to and from said at least one radia-ting element (6, 6a-6c), and at least one ground conductor (2, 2a-2g) connectable to electrical ground. The signal conductor (1, 1a, 1b, 1c) and the ground conductor (2, 2a-2g) extend in parallel from said contact edge portion of the feeding portion (10) to said radiating portion (9) so as to form an essen-tially lossless waveguide for RF-signals. The feeding portion (10) is rigid and is provided with a contact edge portion hav-ing signal and ground contact terminals for making electrical contact with corresponding contact terminals on the communica-tion apparatus. The antenna device may be a meander antenna, a patch antenna, a slot antenna or a PIFA.

Description

Antenna with a non-radiating coupling portion

The present invention relates to an antenna according to the introductory portion of claim 1. In particular, it relates to antennas comprising an essentially non-radiating coupling por- tion.

Summary of the invention

Antennas arranged on thin substrates, often manufactured by etching a radiating pattern on a conductive layer, made from for example copper, on the substrate, comprising a coupling portion etched from the same or an other conductive layer, for transmitting RF-signals from a communication apparatus to the antenna, are known in the art. Manufacturing the radiating pattern and the coupling portion in the same manufacturing step is cost effective and simple, as compared to adding a separate coupling element. A disadvantage is that the thin substrate is often made from substances such as nylon, cap- tone, polyester plastic or polyamides, which makes it flexible and not easily inserted into an electrical connector without bending. Further, the coupling portion radiates and emits ra- diation in directions where it might not have been intended to radiate, thus loosing effective radiating power, and the coupling portion also affects the impedance properties of the antenna .

WO 99/63622 discloses an antenna comprising a conductive la- mina opposing a reference plane, such as a planar inverted F- antenna (PIFA) . The antenna further comprises a feed section extending from the reference plane and connected to the lamina, with two conductors forming a transmission line, which may be embodied as a microstrip, a coplanar strip or a stripline, and coaxial transmission lines are mentioned. The feed section is described as a separate element, which by fur- ther manufacturing steps is attached and electrically connected to the conductive lamina and to the RF-transceiver in the communication apparatus.

US-A-4197544 discloses an antenna comprising a flat dielectric substrate with a grounded conductive pattern on its upper and lower surfaces. On one of these surfaces or in the dielectric substrate itself extends a conductive pattern constituting a microstrip feeding waveguide and a radiating portion. The radiating portion transceives RF-signals through a window in one of the grounded conductive patterns. The microstrip feeding waveguide extends from a connector element to the radiating portion of the antenna. This connector element extends from the feeding end of the microstrip feeding waveguide, through a small window in the other grounded conductive pattern and is adapted to be connected to the RF transceiver of a communication apparatus. Additional elements are needed for connecting the two grounded conductive patterns to the ground of the communication apparatus, and the connector element needs to be separately assembled on the antenna.

EP 924 797 Al discloses an antenna on a plane dielectric substrate, having an grounded conductor on the lower side, a radiating conductor on the upper surface, and a conductor short- circuiting the lower and the upper side conductors at a point. The radiating conductor has a particular candle- stick shape for achieving resonances at desired frequencies. The short- circuiting conductor and an other conductor for transmitting signals to and from an RF-transceiver may extend along a side of the substrate. The signal transmitting conductor is connected to the RF-transceiver by a separate element, such as a coaxial cable, and needs to be attached to and electrically connected to the separate element by soldering or the like. An object of the invention is therefore to provide an antenna apparatus that overcomes the above mentioned problems with prior art antennas .

These and other objects are attained by an antenna apparatus according to the characterizing portion of claim 1.

The invention relates to an antenna apparatus for use in a radio communication apparatus. The apparatus comprises a flat structure comprising a substrate with a conductive pattern on at least one surface. The structure comprises a radiating por- tion, and a feeding portion, with a signal conductor and at least one ground conductor. The structure is a separate unit arranged to be electrically and mechanically coupled to the communication apparatus, with a rigid feeding portion having a contact edge portion for engaging and making electrical con- tact with contact terminals on the communication apparatus.

The signal conductor and the at least one ground conductor extend in parallel from the contact edge portion of the feeding portion to the radiating portion. The signal conductor and at least one of the ground conductor (s) constitute an essentially lossless waveguide for RF-signals.

The ground conductor and the signal conductor may, in one embodiment, constitute a microstrip waveguide if the ground conductor is arranged on one side of the feeding portion and the signal conductor is arranged on the other side of the feeding portion. Alternatively, in another embodiment, the ground conductor and the signal conductor may constitute a coplanar waveguide, if two ground conductors and the signal conductor are arranged on one side of the feeding portion. Even if the waveguide is embodied as a coplanar waveguide having all elec- trically active conductive patterns on one side of the feeding portion, the other side of the substrate may still have a con- ductive pattern on the other side for increased rigidity or stiffness. Independently of which embodiment is selected for the feeding portion, an element extends along and is attached to the feeding portion for increasing its rigidity. The ele- ment which gives this rigidity may be a ground conductor or a separate element, which in turn may be conductive or non conductive. The rigidity of the feeding portion gives the advantage that it may easily be inserted into a connecting element, or resiliently press against a contact tongue. Generally, the term rigid, when related to the properties of the feeding portion, should be interpreted as rigid enough to be inserted into a connecting element or more rigid than other portions of the substrate.

Brief description of the drawings

Fig. 1 shows a first embodiment of the feeding portion in cross section.

Fig. 2 shows a second embodiment of the feeding portion in cross section.

Fig. 3 shows a third embodiment of the feeding portion in cross section.

Fig. 4 shows a fourth embodiment of the feeding portion in cross section.

Fig. 5 shows a fifth embodiment of the feeding portion in cross section.

Fig. 6 shows a sixth embodiment of the feeding portion in cross section.

Fig. 7 shows a seventh embodiment of the feeding portion in cross section. Fig. 8 shows an eighth embodiment of the feeding portion in cross section.

Fig. 9 shows a first embodiment of the antenna apparatus according to the invention.

Fig. 10 shows a second embodiment of the antenna apparatus according to the invention.

Fig. 11 shows the second embodiment of the antenna apparatus according to the invention in perspective.

Figs 12 and 13 shows a ninth embodiment of the feeding portion in a side view.

Description of preferred embodiments

Fig. 1 shows a first embodiment of the feeding portion in cross section. The dielectric substrate 4 has conductive patterns on its upper and lower surfaces. The upper conductive pattern is the signal conductor 1 and the lower conductive pattern is the ground conductor 2. The ground conductor is arranged to be grounded, as indicated by the ground symbol connected to the ground conductor, and the signal conductor 1 and the ground conductor 2 act as a microstrip waveguide, trans- ceiving RF-signals between the radiating portion and the communication apparatus.

Fig. 2 shows a second embodiment of the feeding portion in cross section. The dielectric substrate 4 has conductive patterns on its upper surface, the central conductive pattern be- ing the signal conductor 1 and the outer conductive patterns being ground conductors 2a, 2b. The ground conductors are arranged to be grounded, as indicated by the ground symbols connected to the ground conductors, and the signal conductor 1 and the ground conductors 2a, 2b act as a coplanar waveguide, transceiving RF-signals between the radiating portion and the communication apparatus.

Fig. 3 shows a third embodiment of the feeding portion in cross section, similar to both previous embodiments. The di- electric substrate 4 has conductive patterns on its upper surface, the central conductive pattern being the signal conductor 1 and the outer conductive patterns being ground conductors 2a, 2b, as in fig. 2. It has an additional conductive or non conductive pattern 3 on the lower side of the substrate, giving additional rigidity to the feeding portion as compared to the previous embodiments.

The additional conductive pattern 3 may be electrically disconnected, making the signal conductor 1 and the ground conductors 2a, 2b act as a coplanar waveguide, or it may be grounded, in which case the signal conductor 1 and the ground conductors 2a, 2b and 3 act as a waveguide. The latter waveguide then cannot easily be defined as being either of the coplanar or microstrip type.

Fig. 4 shows a fourth embodiment of the feeding portion in cross section, similar to the first embodiment. However, it has three signal conductors la, lb, lc, each of which act as a separate microstrip waveguide, transceiving three separate RF- signals between the radiating portion and the communication apparatus. Each of the signal conductors may transceive RF- signals to and from separate radiating portions.

Fig. 5 shows a fifth embodiment of the feeding portion in cross section, similar to the second embodiment. It does, as in the previous embodiment, have three signal conductors la, lb, lc, but four ground conductors 2a, 2b, 2c, 2d separate the signal conductors from each other and surround these on both sides. The three signal conductors la, lb, lc and the four ground conductors 2a, 2b, 2c, 2d act as coplanar waveguides, being able to transceive three separate RF-signals to and from the radiating portion.

Fig. 6 shows a sixth embodiment of the feeding portion in cross section, similar to the previous embodiments. It has an additional conductive pattern 3 on the lower side of the substrate, as the embodiment in figure 3, giving additional rigidity to the feeding portion as compared to the previous embodiments. The pattern 3 may be conductive and electrically disconnected, as in the embodiment in figure 3, or it may be conductive and grounded, or it may be non conductive.

Fig. 7 shows a seventh embodiment of the feeding portion in cross section, where the feeding portion is split into three separate legs, appearing in this cross sectional view as dis- joint elements. Each of the legs act as microstrip waveguide similar to the one in fig. 1.

The advantage of splitting the feeding portion into separate legs, each of which has one conductive pattern per surface only, is that it allows for a larger tolerance in a connector element, into which the feeding portion is inserted for connecting the antenna apparatus to the RF-transceiver (s) of a communication apparatus. One continuous feeding portion with several conductors, whether microstrip, coplanar or a single conductor line, might be offset or bent in the connector ele- ment, giving bad or no contact between one or several conductors and the RF-transceiver (s) .

Fig. 8 shows an eighth embodiment of the feeding portion in cross section, comprising one signal conductor la and the ground conductor 2 acting as a microstrip waveguide, trans- ceiving high-frequency RF-signals between the radiating portion and the communication apparatus without radiating. It further comprises four conductors 5a, 5b, 5c, 5d on its upper conductive pattern. These are not intended for transceiving high-frequency RF-signals, but lower frequency control signals for actively controlling properties of the antenna apparatus, or for other purposes. For avoiding overhearing between individual microstrip or coplanar waveguides on one feeding portion, a certain minimum distance between the signal conductors is necessary, while this is not as pronounced for lower frequency signals, such as the ones intended for transmission in conductors 5a, 5b, 5c, 5d.

Fig. 9 shows a first embodiment of the antenna device according to the invention with a feeding portion 10 similar to the one shown in fig. 7, and a radiating portion 11. The ground conductors 2e, 2f, 2g each extends to the radiating portion 11, where there are three separate radiating elements 6a, 6b, 6c. The ground conductors and signal conductors la, lb, lc act as lossless waveguides. The radiating elements 6a, 6b, 6c are here embodied as meander antenna elements, each of which is connected to one of the signal conductors la, lb, lc, but more generally each signal conductor may be directly of capaci- tively connected to one or more radiating elements. In this embodiment, the feeding portion may be bent in relation to the radiating portion, or it may be in plane with the radiating portion. Generally, the feeding portion may be bent in rela- tion to, or it may be in plane with the radiating portion, if both embodiments are possible in terms of the radiative properties of the antenna.

Fig. 10 shows a second embodiment of the antenna apparatus with a feeding portion 10 similar to the one shown in fig. 8, and a radiating portion 9. The antenna device also comprises a control element 7, which may contain logic circuitry for actively controlling the properties of the antenna device, for transmitting information to the communication apparatus regarding the properties of the antenna, or for any other purpose. The radiating portion 9 is provided with a conductive pattern suitable for a PIFA or a slot antenna. Characterising for these antenna types is that they may need to be grounded.

The ground conductor 2 extends onto a part of the radiating portion 3, and this defines where the radiating element 6 radiates, and where the signal conductor 1 act as lossless waveguide. The ground conductor 2 extends onto part of the ra- diating portion 9 so as to supply the control element 7 with a ground level signal, and it also makes it possible to ground the radiating element 6. The ground conductor 2 extends along the lower surface of the feeding portion and reaches to an area under the radiating portion, and is connected to the ra- diating portion via an element 8 extending through the dielectric substrate.

Fig. 11 shows the second embodiment of the antenna apparatus in perspective. The antenna apparatus is bent along the dividing line between the radiating portion 9 and the feeding por- tion 10. This configuration is advantageous for PIFA, patch or slot antennas, as the feeding portion 10 can be introduced into a connector element of the communication apparatus upon mounting the device, the radiating portion 9 is oriented essentially in parallel to a grounded conductive portion of a circuit board (PCB) of the communication apparatus

The rigidity of the feeding portion 10 makes it possible to insert the free edge with the contact terminal ends of the signal 1, 5a-d and ground conductors 2 into corresponding contact terminals 13a-e, e.g. in the form of resilient clamping elements, on the communication apparatus. The rigidity is attained by a proper dimensioning of the conductors on the fee- ding portion, whereas the substrate is somewhat flexible so as to enable bending as indicated above.

Figure 12 shows a ninth embodiment of the feeding portion in cross section, where the resiliency of the comparatively rigid feeding portion is used for resiliently pressing the free edge of the feeding portion with the contact terminal ends of the signal 1, 5a-d conductors against contact elements 11 on a PCB 12. Obviously a separate contact element is needed for contacting conductor on the rear side of the feeding portion to ground, if the rear side pattern 3 is conductive and should be grounded, which is not necessarily the case. It may alternatively be conductive but not directly electrically connected to any other element, or it may be non conductive.

Figure 13 shows the ninth embodiment of the feeding portion in cross section, where the resiliency of the comparatively rigid feeding portion only is used for fixing the feeding portion against contact terminal 13a, contacting the antenna with the RF-transciever of the communication apparatus.

Although the invention has been described in conjunction with a number of preferred embodiments, it is to be understood that various modifications may still be made without departing from the scope of the invention as defined by the appended claims. One such possible modification is to be assure the necessary rigidity of the feeding portion by making the substrate thicker in that portion or laminate the substrate with a layer of a more rigid dielectric material .

Claims

1. An antenna device for use in a radio communication apparatus with a ground plane, said device comprising a substantially flat structure formed by a dielectric substrate (4) with a conductive pattern on at least one surface thereof, said substantially flat structure arrangeable at a fixed distance to the ground plane, and comprising

- a radiating portion (9) , where the conducting pattern constitutes at least one radiating element (6, 6a-6c) , and

- a feeding portion (10) , where the conducting pattern comprises a signal conductor (1, la, lb, lc) for transmitting RF-signals to and from said at least one radiating element (6, 6a-6c) , and at least one ground conductor (2, 2a-2g) connectable to electrical ground,

- said signal conductor (1, la, lb, lc) and said at least one ground conductor (2, 2a-2g) extend in parallel from said contact edge portion of the feeding portion (10) to said radiating portion (9) so as to form an essentially lossless waveguide for RF-signals,

characterised in that

- said feeding portion (10) is rigid and is provided with a contact edge portion having signal and ground contact terminals for making electrical contact with corresponding contact terminals on the communication apparatus.

2. Antenna device according to claim 1 characterised in that - said device is a separate unit adapted to be electrically coupled to and detachably mounted to said communication apparatus.

3. Antenna device according to claim 1 or 2 characterised in that

- said substrate (4) is flexible, and

- the rigidity of said feeding portion is obtained by way of a separate element attached to the feeding portion.

4. Antenna device according to claim 1 or 2 characterised in that

- said substrate (4) is flexible, and

- the rigidity of said feeding portion is obtained by way of said signal and ground conductors.

5. The antenna device according to any one of claims 1-4, characterised in that the radiating portion (9) is bent in relation to the feeding portion (10) .

6. The antenna device according to any one of claims 1-5, characterised in that the ground conductor (2, 2e-2g) is ar- ranged on one side of the feeding portion (10) and the signal conductor (1, la-lc) is arranged on the other side of the feeding portion (10) , the ground conductor and the signal conductor constituting a microstrip waveguide.

7. The antenna device according to any one of claims 1-5, characterised in that two ground conductors (2, 2a-2d) and the signal conductor (1, la-lc) are arranged on one side of the feeding portion (10) , the ground conductors and the signal conductor constituting a coplanar waveguide.

8. The antenna device according to claim 7, characterised in that the feeding portion (10) comprises a conductive pattern (4) on the other side of the substrate.

9. The antenna device according to claim 7, characterised in that the feeding portion (10) comprises a flat metal portion attached to the other side of the substrate.

10. The antenna device according to any one of claims 1-9, characterised in that the ground conductor (2, 2a-2g) extends over part of the radiating portion (9) .

11. The antenna device according to any one of claims 1-0, characterised in that the feeding portion (10) is divided into more than one leg.

12. The antenna device according to claim 11, characterised in that each leg comprises one essentially lossless waveguide for RF-signals .

13. The antenna device according to any one of claims 1-12, characterised in that the radiating portion (9) comprises a meander antenna element.

14. The antenna device according to any one of claims 1-12, characterised in that the antenna device is a patch antenna, a slot antenna or a PIFA.

15. A method of mounting an antenna device in a radio communi- cation apparatus, characterised in that an antenna device as defined in any one of claims 1-14 is fitted onto said apparatus by inserting said edge portion with said contact terminals into said corresponding contact terminals of said apparatus .

16. A method of mounting an antenna device in a radio communication apparatus, characterised in that an antenna device as defined in any one of claims 1-14 is fitted onto said apparatus by resiliently pressing said edge portion with said contact terminals against corresponding contact terminals of said apparatus .

17. A radio communication apparatus provided with an antenna device as defined in any one of claims 1-14.