T 1652/14 (Multi-band branched monopole antenna / Sony Ericsson) 18-02-2021

The invention and its interpretation

1. The invention lies in the field of radio antennas for mobile devices like mobile phones. Such antennas often need to be able to send and receive signals in different frequency bands, like GSM-850 or GSM-900 at lower frequencies, and GSM-1800 (DCS), GSM-1900 (PCS), or UMTS at higher frequencies. Preferably, such antennas are small, simple, and cheap to manufacture, have a high front-to-back ratio (reduced emission towards the head of the user), and little coupling between the different bands.

2. Monopole antennas are often used in mobile devices, because their size of a quarter of a wavelength is only half that of a comparable dipole antenna. A particular kind of monopole antenna used in this context is the PIFA (planer inverted F antenna), which is easy to produce, has a good front-to-back ratio, and a good impedance matching. On the downside, PIFAs have narrow bandwidths in low-frequency bands. They are typically arranged in parallel to a ground plate, to which they are connected through a shorting pin. One measure to expand the bandwidth of PIFAs is to reduce the area by which the ground plate overlaps the antenna pattern. Such configurations are known as "semi-PIFA" antennas.

3. Hence, when the patent refers to a "semi-PIFA" as being "ground free", the term "ground free" cannot say more than what is inherent to this kind of antenna, namely that it is arranged at most partially over a ground plate. In particular, it cannot say that there is no ground connection, or else the antenna would no longer be a (semi-) PIFA. This interpretation is supported by the description, which states on page 3, line 15 that the antenna is ground-free and on page 4, line 35 - page 5, line 4, that the same antenna may be connected to ground (thereby making it a semi-PIFA).

4. Although a PIFA is a particular kind of monopole antenna, the term "monopole antenna" was (and still is) mostly used in the art, in distinction to PIFA, for an antenna that is positioned in a ground-free volume away from any ground plate and which does not have a direct connection to ground. In the context of a monopole antenna, the term "ground free" was, therefore, understood by the skilled person as emphasizing the difference from a PIFA, in so far as the antenna has no connection to ground and is not placed over a ground plate. Such (ground-free) monopole antennas exhibit large bandwidths.

5. The present invention aims at providing an improved antenna that is either a monopole antenna or semi-PIFA, which combines all above qualities (large bandwidth, in particular in the low-frequency band; good front-to-back ratio; little coupling between the bands) whilst still being compact and simple to manufacture.

6. The application is not specific on the differences between the two types of antenna. Nevertheless, the Board is confident that the skilled person would have understood the differences, from her knowledge of the art as explained above.

Main request - Clarity

7. Claim 1 is directed to a carrier comprising a back surface, a side surface and an antenna pattern. The antenna pattern is defined, at least partly, in terms of the antenna in which the carrier will be employed. Certain elements of the antenna, as, for example, the ground elements, in this case in the form of "mass blocks" (as they are called in the application on page 9, lines 7 - 11), are not part of the carrier. Hence, the carrier is a stand-alone element that is ground-free, even if it comprises connectors for connection to an external ground.

8. It is, therefore, not clear to what extent the definitions "wherein said antenna pattern constitutes part of a high gain multi?band branched monopole or semi-PIFA antenna" and "said antenna is ground free" serve to restrict the claimed carrier. This problem persists under the appellant's interpretation of the carrier as "being suitable for use" as part of the defined antenna. The Board fails to see how it could be possible to judge, for an arbitrary carrier and antenna pattern, if it is suitable for use in such an antenna or not. To give an example: is a pattern that happens to be arranged over a ground plate also suitable for use when separated from the ground plate? If this separation caused a deterioration in performance, would the pattern still be considered as suitable to be used as such?

9. As a result, claim 1 is not clear (Article 84 EPC).

Main request - Novelty

10. Figure 8c of D4 shows a carrier 15 with an antenna pattern 2, the pattern having a wider first branch K arranged on a horizontal back surface of the carrier and a narrower second branch 12 arranged on a side surface, with both branches extending from a common point, and with the second branch having a vertically extending section and a horizontally extending section. The question of whether the stub 12 is able to emit radiation is irrelevant for its designation as a "branch", which is a purely geometrical description without any implication for its function.

11. It can be seen, in the same figure, that the carrier with its antenna pattern has a connection Gq intended for a connection to ground. When not included in an antenna structure, the carrier is ground-free.

12. The type of antenna in which the carrier is used is not a characteristic of the carrier itself, and is interpreted as not restrictive for the carrier. The antenna type is, therefore, of no relevance for the question of novelty.

13. As a result, the subject-matter of claim 1 is not new (Article 54 EPC).

14. The above argument notwithstanding, it is noted that, in this particular case, it is possible to assert that the carrier of D4 is suitable for use in a ground-free semi-PIFA antenna (see the interpretation of this term given under item 3.), by using its connector Gq for a connection to ground, using its connector Q for a connection to the feed, and by using a small ground plate that only partially overlaps the antenna. Hence, the subject-matter of claim 1 would also not be new if the reference to the antenna could have been interpreted as the appellant argued.

First auxiliary request

15. The first auxiliary request contains only formal amendments with no change to the substance of the claims. The amendments do not address the the problems of clarity and novelty that apply to the main request and, hence, there are no exceptional circumstances, in the meaning of Article 13(2) RPBA 2020, that would justify taking this request into account.

Second auxiliary request - General remarks

16. In contrast to the main request, claim 1 is no longer directed to a carrier comprising an antenna pattern that "constitutes part of a high gain multi-band branched monopole or semi-PIFA antenna", but to a "high gain multi-band branched monopole antenna" that comprises said carrier.

17. This amendment is a reaction to the problem with clarity - and the consequential claim interpretation and novelty argument - first set out by the Board in its communication sent in preparation of oral proceedings. These newly identified issues constitute exceptional circumstances, in the sense of Article 13(2) RPBA 2020, that justify the consideration of this request.

18. It is apparent, from the amendment, that the clarity issues no longer apply.

19. The application as filed was directed to "an improved antenna" (see page 2, line 14 of the description) and, for this purpose, provided a carrier with a particular antenna pattern. The technical effects of the pattern depended on the type of antenna in which it was put to use, because the ground plate, and the ground connection in particular, have a strong influence on the emission properties. In this case, the advantages of the invention, which consist of a wide bandwidth, high directivity, small coupling, and good isolation (page 3, lines 5 - 20 of the published application), are intricately linked to the pattern used in a "high gain multi-band branched monopole or semi-PIFA antenna".

20. For this reason, the attempt to define the invention by the carrier alone failed, despite the definition, in the claims, of the intended use.

21. In defining the whole antenna, the present claims define no more than the initially described invention, without deviating from the originally described idea. In its assessment of novelty and inventive step the Examining Division, in its decision under items 1.1 and 2 of the Reasons, explicitly considered the use of the carrier in an antenna and also assessed dependent claims 13 - 15, which were directed to a device like a mobile phone that comprises the carrier - and therefore, necessarily, the whole antenna.

22. For these reasons, the Board considers the documents on file suitable for a complete examination of patentability and sees no special reasons, in the sense of Article 11 RPBA 2020, that would prevent it from issuing a decision on that matter.

Second auxiliary request - Novelty

23. Document D1 discloses a semi-PIFA with a single branch folded in two orthogonal planes. D2 discloses a semi-PIFA with 3 branches, one of which is folded in two orthogonal planes. D3 discloses combined monopole and dipole antennas with a single branch each, the branch of the monopole antenna being folded in two orthogonal planes. D4 discloses a PIFA with two branches in orthogonal planes. D5 comprises a PIFA and a microstrip antenna coupled by a single feed. And D6 discloses a planar monopole antenna with two branches.

24. It follows that the subject-matter of claim 1 differs from D1, D2, D3, D4, and D5 in that the antenna is a ground-free monopole, from D1 further in that the antenna comprises two branches, and from D1, D2, D3, D5, and D6 in that each of the two branches is entirely arranged in a plane orthogonal to the other.

25. Hence, the subject-matter of claim 1 is new (Article 54 EPC).

Second auxiliary request - Inventive step

26. Document D6 is the only document on file that discloses a ground-free, multi-band, branched, monopole antenna. In contrast to the other documents, it has broadband properties in the low-band, similar to the invention, due to its ground-free structure.

27. The two branches of the antenna in D6 lie in the same plane, whereas claim 1 defines two branches in orthogonal planes.

28. The technical effect of that difference starting from D6 lies in a reduced capacitive coupling between the branches and a higher directivity in the emission pattern.

29. The objective problem was to reduce the coupling between the high-band und the low-band, or to improve the front-to-back ratio.

30. The skilled person, trying to solve either or both these problems, would have had no incentive to deviate from the geometry described in D6, because the primary goal of D6 is "to provide a planar monopole antenna" for dual frequency operation.

31. Even if the skilled person would have considered changing the geometry to a non-planer arrangement, she would have been bound by the specific dimensions indicated in D6, which would not have allowed the narrow branch of width 1 mm to fit the carrier's side surface of width 0.8 mm. Further, even if she would have considered amending the widths to fit branch 524 of Figure 5 to the side surface, this would have changed it's emission properties, because the antenna would no longer be centered with respect to the large ground plate 58. This would further have discouraged the skilled person from such changes.

32. For these reasons, the skilled person would also not have considered a combination of D6 with an antenna pattern of any of D1 - D5. The antennas described in the latter documents are of a different type and have different emission properties, and could not have been simply combined with a monopole antenna.

33. On the other hand, taking one of D1 - D5 as a starting point, the skilled person would have refrained from removing the ground connection from any of the antennas described in those documents. Each of them intentionally choose an antenna with a ground connection. The fundamental resonant frequency is mainly determined by the LC-circuit formed by the capacitive coupling of the antenna pattern to the ground plate and by the inductive properties of the short-circuited stub. D1 - D5 use different means of increasing the bandwidth or of adding further resonances to this fundamental frequency. D1 uses a combination of folding a single antenna branch for inducing harmonic resonances and coupling the branch to one or more parasitic elements that induce further resonances. D2 uses a plurality of branches with different resonant frequencies that can be folded in order to save space. D3 combines a single-branch monopole with a dipole antenna. D4 couples a dual-band PIFA with an unfed, similar antenna with different resonance frequencies. Finally, D5 combines a PIFA with different antennas using the same feed and a common ground plate.

34. All these particular ideas for adding bandwidth would have been pointless without the ground connection.

35. It follows that the subject-matter of claim 1 involves an inventive step (Article 56 EPC). As a consequence, the lower ranking third auxiliary request needs not be assessed.

Conclusion

36. It follows from the above that the main request is not allowable for lack of novelty and clarity; the first auxiliary request is not considered; and the second auxiliary request is allowable, although some adaptation of the description will be needed.