T 1310/11 () of 26.10.2012

Summary of Facts and Submissions

I. European patent application No. 03 749 246.9, filed on 29 August 2003 as international application PCT/US2003/027194 in the name of THE REGENTS OF THE UNIVERSITY OF CALIFORNIA was refused by a decision of the examining division, which was announced orally on 28 October 2010 and issued in writing on 9 December 2010.

II. The examining division's decision was based on a main request containing claims 1 and 2 filed on 18 January 2010 and claims 3 to 14 filed with entry into the regional phase before the EPO and on an auxiliary request containing claims 1 and 2 filed on 5 October 2010 and claims 3 to 14 filed with entry into the regional phase before the EPO.

Claim 1 of the main request read as follows:

"1. A compensating multi1ayer material comprising:

- an indefinite anisotropic first layer having material properties of epsilon1 and my1, both epsilon1 and my1 being tensors, and a thickness d1;

- an indefinite anisotropic second layer adjacent to said first layer, said second layer having material properties of epsilon2 and my2, both epsilon2 and my2 being tensors, and having a thickness d2; and,

wherein epsilon1, my1, epsilon2 and my2 are simultaneously diagonalizable in a diagonalizing basis that includes a layer normal to said first and second layers, and

epsilon2 = psiepsilon1

my2 = psimy1

where

FORMULA/TABLE/GRAPHIC

d1/d2 0 0

psi = - 0 d1/d2 0

0 0 d2/d1

and psi is a tensor represented in the diagonalizing basis with a third basis vector that is normal to said first and second layers.

Claim 1 of the auxiliary request differed from claim 1 of the main request in that epsilon1, my1, epsilon2 and my2 were at least closely approximately simultaneously diagonalizable and in that epsilon1, my1, epsilon2 and my2 at least closely approximately satisfied the equations epsilon2 = psiepsilon1 and my2 = psimy1.

III. The examining division argued essentially as follows:

The main request does not meet the requirements of Article 83 EPC.

Claim 1 requires the first and second layers to have permittivity and permeability tensors epsilon and my that can be simultaneously diagonalized. It is however nowhere mentioned in the application as to how this diagonalization can be achieved, and whether physical materials exist that have permittivity and permeability tensors epsilon1, my1, epsilon2 and my2 that are indeed simultaneously diagonalizable. Even more so, the application actually states that such materials do not exist, by mentioning on page 6 that "metamaterials" can be constructed that closely approximate these my and epsilon tensors rather than having exactly these tensors. From this statement it has to be concluded that materials having the required diagonalization property do not exist and that hence also the materials used in the embodiment of figure 5 do not fulfil this requirement of claim 1. Since, furthermore, this embodiment of figure 5 is the only way indicated in the application as filed as to how to carry out the invention, the requirements of Article 83 EPC in conjunction with Rule 42(1)(e) EPC are not met.

In addition, claim 1 is not restrictive as to the values of the thickness ratio d1/d2 and thus covers ratios with very small thicknesses d1, such as 0.001lambda. For such a thickness, the invention cannot be carried out, since there are no materials that constitute an indefinite anisotropic first layer having the assumed properties with a thickness dl equal to 0.001lambda. For example, when split ring resonators are used in one of the layers, the minimum thickness of such a layer would be at least in the order of lambda/4, since this would be the length of a side of said split ring.

The auxiliary request was not admitted into the proceedings under Rule 137(3) EPC because it was filed late and was clearly not allowable under Articles 84, 123(2) and 83 EPC.

IV. On 9 February 2011, the applicant (in the following "appellant") filed a notice of appeal against the above decision and paid the prescribed fee on the same day. A statement setting out the grounds of appeal was filed on 19 April 2011 together with a main and an auxiliary request, which were identical to the requests before the examining division; and

D5: Affidavit by Professor Sir J. B. Pendry dated 15 April 2011.

Further, reference was made to

D6: J. B. Pendry et al, "Magnetism from conductors and enhanced nonlinear phenomena", IEEE Transactions on microwave theory and techniques, volume 47(11), 1999, pages 2075-2084 (a copy of this article was filed by the then-applicant on 5 October 2010 during examination proceedings).

V. By communication dated 12 March 2012, the board issued its preliminary opinion, in which the main request was objected to under Articles 83 and 84 EPC.

As to the requirements of Article 84 EPC, the board questioned the clarity of inter alia the following expressions:

- "indefinite anisotropic layer";

- "that may be defined as" and "generally planar"; and

- "Never Cutoff property".

As to sufficiency of disclosure the board raised the following objections:

- Claim 1 covers multilayer materials with any type of building blocks provided only that they meet the mathematical requirements defined in this claim. The application as filed discloses however only one way of carrying out the invention, namely a composite material containing two specific building blocks, namely one being composed of straight wires and the other being composed of split ring resonators. There is no information at all in the application as filed as to how a multilayer material with building blocks different from these two specific ones can be constructed that meets the mathematical requirements of claim 1.

- The elements of the tensor psi and linked thereto the elements of the tensors epsilon and my are defined in claim 1 by the thickness ratio d1/d2. For infinitely small thicknesses d2, this ratio can be infinitely large such that the tensors epsilon and my can have infinite values though no materials with infinite permittivity and permeability exist.

- Claim 1 requires epsilon1, my1, epsilon2 and my2 to be "simultaneously diagonalizable" while according to the penultimate paragraph of page 6 of the application as filed, simultaneous diagonalizability is achievable only approximately.

VI. By letter of 28 September 2012, the appellant submitted a new main and a new auxiliary request together with

D7: D. R. Smith et al, "Partial focusing of radiation by a slab of indefinite media", Applied Physical Letters, volume 84(13), 2004, pages 2244- 2246;

D8: D. Schurig et al, "Metamaterial electromagnetic cloak at microwave frequencies", Science, volume 314, 2006, pages 977-980;

D9: R. A. Shelby et al, "Experimental verification of a negative index of refraction", Science, volume 292, 2001, pages 77-79;

D10: J. B. Pendry et al, "Controlling Electromagnetic Fields", Science, volume 312, 2006, pages 780-782; and

D11: R. A. Shelby et al, "Microwave transmission through a two-dimensional, isotropic, left-handed metamaterial, Applied Physics Letters, volume 78(4), 2001, pages 489-491.

VII. By letter of 2 October 2012, the appellant filed

D12: Supplemental affidavit of Professor Sir J. B. Pendry, dated 30 September 2012.

VIII. On 26 October 2012, oral proceedings were held before the board. During the oral proceedings, the appellant presented background information on "metamaterials" and addressed the objections raised by the board in its preliminary opinion. In this context, the following document was filed

D13: "Indefinite materials - EPO Oral Proceedings 26 Oct. 2012", pages 1-30.

The appellant also filed a new main request as sole request. Claim 1 of the new main request is reproduced in point 2.1 below.

IX. The appellant's position, in as far as relevant to the present decision, can be summarised as follows:

Clarity

- The term "indefinite anisotropic layer" in claim 1 is clear in that it implies that the tensors defining the layer must be indefinite, ie must have negative and positive eigenvalues.

- The term "Never Cutoff property" in claim 3 does not lack clarity as it is clearly defined by the mathematical equations present in this claim.

Sufficiency of disclosure

- Straight wires create negative permittivity while split ring resonators lead to negative permeability. By combining the two structural elements in one layer, indefinite permittivity and permeability tensors as required by claim 1 can be realised.

- The straight wire and split ring resonator structures of claim 1 have well-defined permittivity and permeability values and these translate into well-defined thickness ratios. The thickness ratio is therefore inherently restricted in claim 1 by way of these structures.

- As confirmed by point 12 of the supplemental affidavit D12 of Professor Sir J. B. Pendry, simultaneous diagonalizability is achievable by the straight wire and split ring resonator structures as shown in figure 5 of the application as filed. As to the passage on page 6 of the application as filed, this does not say that simultaneous diagonalizability cannot be reached but only states that approximate simultaneous diagonalizability is achievable.

X. The appellant requested that the decision under appeal be set aside and a patent be granted on the basis of the main request filed during the oral proceedings.

Reasons for the Decision

1. The appeal is admissible.

Main request (sole request)

2. Amendments - Article 123(2) EPC

2.1 Claim 1 refers to "A compensating multi1ayer material comprising:

- an indefinite anisotropic first layer having material properties of epsilon1 and my1, both epsilon1 and my1 being tensors, and a thickness d1;

- an indefinite anisotropic second layer adjacent to said first layer, said second layer having material properties of epsilon2 and my2, both epsilon2 and my2 being tensors, and having a thickness d2;

each of said first and second layers comprising a composite material including a host dielectric medium with split ring resonators and straight wires embedded in said host medium in a periodic spatial arrangement;

wherein epsilon1, my1, epsilon2 and my2 are simultaneously diagonalizable in a diagonalizing basis that includes a layer normal to said first and second layers, and

epsilon2 = psiepsilon1

my2 = psimy1

where

FORMULA/TABLE/GRAPHIC

d1/d2 0 0

psi = - 0 d1/d2 0

0 0 d2/d1

and psi is a tensor represented in the diagonalizing basis with a third basis vector that is normal to said first and second layers."

2.1.1 Claim 1 is identical to claim 1 as filed except that:

(a) the symbol psi is consistently used throughout the equations and the corresponding passages of the text (originally, mixed symbols had been used, namely the symbols psi, phi and ?); and

(b) each of the first and second layers now comprise a composite material including a host dielectric medium with split ring resonators and straight wires embedded in said host medium in a periodic spatial arrangement.

2.1.2 The first amendment (a) represents a correction of an obvious error allowable under Rule 139 EPC. Firstly, it is obvious that original claim 1 contains an error as three different symbols psi, phi and ? are used in the same context. Secondly, the first paragraph on page 3 of the application as filed uses in all equations and the corresponding text exclusively the symbol psi so that the only possible correction in claim 1 is the consistent use of the symbol psi.

2.1.3 The second amendment (b) is based on claim 12 as filed in conjunction with claim 14 and page 12, lines 1-2 as filed.

Claim 12 as filed refers to "A compensating multi-layer material as defined by claim 1 wherein each of said layers comprises a composite material including a host dielectric and one of an artificial electric or magnetic medium embedded in said host medium." (emphasis added). Claim 14 as filed is directed to "A compensating multi-layer material as defined by claim 12 wherein said artificial electric or magnetic medium comprises one or both of split ring resonators and substantially straight wires in a periodic spatial arrangement." (emphasis added). Finally, page 12, lines 1-2 as filed states that "Also, combination of conductors may be made, with lengths of straight wires and split ring resonators being one example combination [sic]." (emphasis added).

In particular, the underlined text of the above-cited passages of the application as filed clearly and unambiguously discloses the combination of split ring resonators and straight wires in the context of the invention.

2.2 Dependent claim 2 refers to "A compensating multi-layer material as defined by claim 1 wherein said first and second layers are planar and of equal thickness ... and wherein each of said material properties epsilon and my for both of said layers are tensors that are defined as: ..." (emphasis added by the board).

Claim 2 is identical to claim 2 as filed except that "generally planar" has been replaced by "planar" and the wording "that may be defined" has been replaced by "that are defined" (see highlighted terms above).

The terms "generally" and "may be" in the original claim imply that apart from the explicit embodiments, eg planar, other options may exist. The deletion of these terms hence merely removes this optionality which is not objectionable under Article 123(2) EPC.

2.3 Dependent claims 3 and 4 are based on a combination of claims 3 and 4 and of claims 5 and 6 as filed, respectively. The fact that claims 3 and 4 as filed and claims 5 and 6 as filed are combined does not add any new subject-matter, as claim 4 as filed refers back to claim 3 as filed and claim 6 as filed refers back to claim 5 as filed.

2.4 Dependent claim 5 is based on claim 7 as filed.

2.5 Dependent claim 6 refers to "A compensating multi-layer material as defined by claim 1 wherein epsilon1 = my1, epsilon2 = my2 and d1 = d2".

The feature "A compensating multi-layer material as defined in claim 1 wherein epsilon1 = my1, epsilon2 = my2" is based on claim 8 as filed and the feature "and d1 = d2" is based on claim 11 as filed. There is at least a pointer to the combination of the two features in the paragraph bridging pages 16 and 17 of the application as filed. This paragraph deals with the case where the epsilon and my tensors are equal to each other and where, in a particular embodiment, also the layer thickness is equal.

Thus, the subject-matter of claim 6 is clearly and unambiguously derivable from the application as filed.

2.6 Claims 7-10 refer to preferred compensating multi-layer materials, spatial filter and antenna embodiments and, by way of back-reference to any of the preceding claims, combine these with the specific first and second layer features of the preceding claims.

The compensating multi-layer material, spatial filter and antenna embodiments of claims 7-10 are based on claims 16, 19 and 22 as well as the paragraph bridging pages 21 and 22 of the application as filed, respectively. The combination of these embodiments with the specific first and second layer features of the preceding claims is based on the same paragraph bridging pages 21 and 22 of the application as filed. More particularly, this paragraph discloses the multi-layer designs, spatial filters and antennae of claims 7-10 in general terms such that it is clear that this disclosure applies to any first and second layer embodiments disclosed in the application as filed.

2.7 The main request thus meets the requirements of Article 123(2) EPC.

3. Clarity (Article 84 EPC)

3.1 As regards the term "indefinite anisotropic layer" in claim 1, it has been convincingly explained by Professor Sir J. B. Pendry in his supplemental affidavit D12 that the terms "indefinite tensor" and "indefinite matrix" are elementary mathematical concepts and mean that the tensor or matrix is neither "positive definite" (ie all elements having positive eigenvalues) nor "negative definite" (ie all elements having negative eigenvalues). The term "indefinite anisotropic layer" in claim 1 can thus only mean that the tensors defining the layer must be indefinite, ie must have negative and positive eigenvalues. This means eg for the permittivity tensor epsilon1 of the first layer

FORMULA/TABLE/GRAPHIC

epsilon1**(xx) 0 0 0

epsilon1 = 0 epsilon1**(yy) 0

0 0 epsilon1**(zz)

that the eigenvalues epsilon1**(xx), epsilon1**(yy) and epsilon1**(zz) are not all positive or negative. The term "indefinite anisotropic layer" in claim 1 thus is clear.

3.2 The board's objection raised in its preliminary opinion against the wordings "that may be defined as" and "generally planar" of the then-pending claim 2 has been met by the appellant's amendment of claim 2, ie the replacement of "that may be defined as" by "that are defined as" and by deletion of the term "generally".

3.3 As regards the term "Never Cutoff property" in claim 3, the appellant has convincingly argued during the oral proceedings that this term is exhaustively defined by the immediately following mathematical equations present in claim 3. Therefore, no clarity objection arises in this context.

3.4 The main request thus meets the requirements of Article 84 EPC.

4. Sufficiency of disclosure (Article 83 EPC)

4.1 In its preliminary opinion, the board took the view that guidance was missing for structures different from those specifically disclosed in the present application, namely layers comprising split ring resonators and straight wires. By restricting claim 1 to these specific structures (point 2.1 above), this objection has been met.

4.2 While there is still no explicit limitation present in claim 1 with regard to the thickness ratio d1/d2, the limitation in claim 1 that the first and second layers of this material contain split ring resonators and straight wires introduces an implicit limitation to physical values that are actually achievable by these two elements. More particularly, as pointed out by the appellant during the oral proceedings, the properties of metamaterials composed of split ring resonators and straight wires are accurately characterised by Maxwell's equations, and therefore highly predictable. Accordingly, there is a predictable, well-defined range of achievable permittivity and permeability for a given implementation of the metamaterial building blocks and this translates into a predictable, well-defined range of achievable thickness ratios (in this context see also lines 3-7 of paragraph 10 of D12).

This is in line with the examining division's argument that split ring resonators must have a side length of at least a fourth of the incoming radiation's wavelength (lambda/4) and that thicknesses below this value thus are not possible.

In view of the above, the board's objection raised in the preliminary opinion with regard to the thickness ratio in claim 1 no longer applies.

4.3 One reason for the examining division's refusal of the application was that the requirement "simultaneously diagonalizable" could not be achieved (point III above). Since according to the penultimate paragraph of page 6 of the application as filed, this requirement was achievable only "closely approximately", the board upheld this objection in its preliminary opinion.

4.3.1 However, in its supplemental affidavit D12, Professor Sir J. B. Pendry resists this argument. More specifically, in point 12 of D12, he makes the following statement:

"With respect to the Board's statement that "no material is available for which the permittivity and permeability tensors are simultaneously diagonalizable", I believe that this statement is incorrect. As I explained in my earlier affidavit at points 9-14, a simultaneously diagonalizable metamaterial can be constructed by positioning wires and split rings along orthogonal axis. The inventors of the current application have followed this prescription, as seen in Figure 5 of the application, which shows various arrangements of wires and split rings along x, y, and z axes. Based upon my earlier work, cited in paragraph 10 of the prior affidavit, it can be stated with certainty that the arrangements depicted in Figure 5 of the current application satisfy the condition of simultaneous diagonalizability. This certainty follows from the fact that the structures behave according to Maxwell's equations, which are predictable and solvable." (emphasis added by the board).

In view of this clear and unequivocal statement made by a leading expert in the field, the board accepts that with the specific straight wire and split ring structures to which claim 1 has now been restricted, simultaneous diagonalizability rather than an approximate simultaneous diagonalizability is indeed achievable. This is also not in contradiction to the above cited passage on page 6 of the application as filed as this passage only states that approximate simultaneous diagonalizability is achievable which does not necessarily imply that simultaneous diagonalizability is not achievable.

4.3.2 Furthermore, it is stated in point 13 of D12 that there have been experimental demonstrations of simultaneously diagonalizable media.

4.3.3 The board is therefore persuaded that the invention underlying the main request is sufficiently disclosed with regard to the diagonalizability requirement of claim 1.

4.4 The main request thus meets the requirements of Article 83 EPC.

5. Remittal

In view of the fact that novelty and inventive step have not yet been dealt with by the examining division, remittal to the examining division for further prosecution is appropriate.

ORDER

For these reasons it is decided that:

1. The decision under appeal is set aside.

2. The case is remitted to the examining division for further prosecution on the basis of claims 1-10 of the main request filed during the oral proceedings before the board.