T 1600/06 (Repeater with variable bandwidth/ALLGON) 10-10-2008

1. Inventive step (excluding late-filed documents D25-D28)

1.1 The parties and the board are in agreement that D6 represents the closest prior art to the present invention as it concerns a mobile telephone [system] repeater having all the features of the preamble of claim 1. In particular, the claimed repeater comprises inter alia a number of parallel amplifier chains, each amplifier chain being designed to pass through a specific frequency band.

1.2 The board regards the objective technical problem to be solved, starting from D6, as to facilitate frequency bandwidth changes in one or more amplifier chains of the repeater of D6 without necessitating hardware replacements.

1.3 In order to solve this problem, the characterising part of claim 1 defines inter alia that two band pass filter units have controllable pass bands which at least partially overlap each other, each of said band pass filter units comprising an input down-mixer, a band pass filter, an output up-mixer and an associated, controllable local oscillator.

The principle of operation defined in claim 1 is that each local oscillator is controlled to shift the frequency band entering each band pass filter to be cut off at one end, whereby the centre frequency of each band pass filter unit is controllable so as to make the bandwidth of the resulting overlap pass band variab1e.

1.4 The appellant argued that starting from D6, the skilled person would be led by the teaching of D20 to arrive at the subject-matter of claim 1 without an inventive step.

1.5 Document D20 concerns a radio telephone receiver with adjustable bandwidth. The receiver chain includes first and second intermediate frequency (IF) filters at respectively 45 MHz and 0.455 MHz. A first mixer converts the RF input signal to the first intermediate frequency (1.IF). A second mixer converts the first intermediate frequency to the second intermediate frequency (2.IF). By offsetting the local oscillator inputs 1.LO and 2.LO to the first and second mixers, the frequency band can be cut off at the top and bottom, resulting in a variable pass band according to the degree of offset of the local oscillator frequencies.

1.6 Although in the board's view D20 uses a similar concept to the present patent, the board doubts that the skilled person would seek from D20 a solution to a problem concerning a repeater. In this respect, D20 relates to a double-conversion super-heterodyne receiver employing a second intermediate frequency far below the first intermediate frequency (in the disclosed embodiments of D20, the second intermediate frequency is 0.455 MHz, a factor 100 lower than the first intermediate frequency), making the use of this receiver circuit implausible in a repeater environment in which the signal is be reconverted to a radio signal for retransmission. The board notes that in the claimed repeater, the intermediate frequencies of the first and second filter units must be close to each other in order that the pass bands of the two fixed filters at least partially overlap.

1.7 However, if for the sake of argument the skilled person were to attempt to modify the arrangement of D6 based on the teaching of D20, the board agrees with the reasoning of the opposition division that a different arrangement to that claimed would result and that a number of additional steps would be required by the skilled person to arrive at the arrangement claimed (cf. paragraph III, "Summary of Facts and Submissions" above). In particular, the arrangement of two variable filter units each comprising a mixer followed by a band pass filter and a second mixer would not be suggested, since the structure of D20 makes use of only a single mixer between the two band pass filters; ie there would be no up-conversion following the first band pass filter followed by a down-conversion before the second band pass filter.

1.8 In the statement of grounds, the appellant commented on this difference as follows:

"In contrast to D6 and the opposed patent, the filter unit does not included [sic] a second mixer. As obvious for the skilled person referring to D6, the function of the second mixer in the first filter unit and the function of the first mixer in the second filter unit can be realized in combination in said first mixer of the second filter unit. By this measure, the configuration of a filter unit slightly varies while the realized technical function remains the same as compared to D6 or the opposed patent".

In other words, the function of two mixers for up and down-conversion is alleged to be an equivalent arrangement to a single mixer with the appropriately modified local oscillator input frequency.

1.9 However, the respondent argued in its response to the statement of grounds that this difference does not concern a technically equivalent alternative, but produces a technical effect. In this respect, the respondent submitted the following:

"....it can be concluded that it is essential, for achieving a good repeater function, that a frequency originating from the VCO, in each filter unit (10, 11) is first subtracted and then added, such that the centre frequency of the signal passing through the filter unit (10, 11) is not altered. To be totally sure that the frequency from the VCO is really cancelled out, the same VCO can be used for both the down-mixer and the up-mixer within each filter unit (10, 11), as is stated in claim 1 of the main request. This also necessitates the up-mixer (21a, 21b) at the output of each filter unit (10, 11) and the down-mixer at the input of each filter unit (10, 11) to be separately configured.

On the contrary .... if two different VCOs had been used for feeding the down-mixers (20a, 20b) and the up-mixers (21a, 21b) in each filter unit, there would always be a risk that the frequencies from these two VCOs (here denoted fLo1 and fLo2 ) might differ (e.g. due to aging and temperature drift), which would lead to that [sic] the frequency contribution of the VCOs would not be cancelled out".

1.10 The board agrees with the respondent that the difference with respect to the putative D6-D20 combination does not concern a mere equivalent arrangement where the function of a single mixer is carried out by two mixers connected in series, since in the claimed arrangement the two filter units are self-compensating as regards frequency offset, whereas with an arrangement such as in D20 the two oscillators would have to be locked to avoid any risk of a frequency offset at the repeater output.

1.11 Moreover, the board considers that the claimed arrangement would not be obvious to the person skilled in the art who is aware of documents D6 and D20 without the benefit of hindsight, as nothing in these documents might lead a skilled person to make such a modification, nor is the resulting advantage a priori so self-evident that the skilled person would be led to do so on the basis of his common general knowledge.

1.12 The appellant argued at the oral proceedings that directly applying the arrangement of D20 as discussed above is only the first of two obvious solutions, the second obvious solution being to extract the general concept of bandwidth variation disclosed in D20, which is to couple two filters in series and to variably control the mixers, and to apply this concept to the arrangement of D6. Since the skilled person would find it advantageous to use a series of known and available filter units of the type disclosed in D6, the arrangement of claim 1 would be arrived at without inventive step.

However, the board considers that the appellant's second solution is based on an ex-post facto analysis and therefore finds this line of argumentation unconvincing.

1.13 The board therefore agrees with the opposition division that the subject-matter of claim 1 as maintained involves an inventive step with respect to the combination of D6 and D20 (Articles 52(1) and 56 EPC). These documents therefore do not prejudice the maintenance of the patent in amended form.

1.14 In the appeal procedure (leaving aside the submissions based on D25-D28), the appellant did not attempt to argue on the basis of any combination of documents other than D6 and D20.

2. Admissibility of D25-D28

2.1 As the board concludes that documents D6 and D20 filed during the opposition procedure do not prejudice the maintenance of the patent as amended, the board has to decide on the admissibility of documents D25-D28 filed during the appeal proceedings.

2.2 In accordance with Article 114(1) EPC, in proceedings before it, the European Patent Office shall examine the facts of its own motion. On the other hand, in accordance with Article 114(2) EPC the European Patent Office may disregard facts or evidence which are not submitted in due time. Article 13 RPBA (OJ 11/07, 536-546), which sets outs the procedural provisions applicable to the boards of appeal rather than Rule 71a(1) EPC 1973 (now Rule 116(1) EPC) mentioned by the respondent (cf. G 6/95, OJ 1996, 649), stipulates that any amendment to a party's case after it has filed its grounds of appeal or reply made be considered at the board's discretion. This discretion shall be exercised in view of, inter alia, the complexity of the new subject-matter submitted, the current state of the proceedings and the need for procedural economy (Article 13(1) RPBA). Further, amendments sought to be made after oral proceedings have been arranged shall not be admitted if they raise issues which the board or the other parties cannot reasonably be expected to deal with without adjournment of the proceedings (Article 13(3) RPBA).

2.3 When exercising its discretion under Articles 114(2) EPC and 13(1) RPBA whether or not to admit a late-filed document the board will seek to balance on the one hand the need to avoid unnecessary delay in reaching a final decision, which is implicit in the criteria set out in Article 13(1) RPBA, and on the other hand the public interest which requires that invalid patents should not be maintained. In balancing these principles, it is well-established case law of the boards of appeal that a late-filed document may, exceptionally, be admitted to the proceedings if it is prima facie highly relevant in the sense that it is highly likely to prejudice the maintenance of the patent (see eg T 1002/92, OJ 1995, 605).

2.4 D25 and D26 were filed with the statement of grounds of appeal, ie after the nine month period for opposition. In its communication, the board informed the appellant that the documents did not appear to add anything of significance to the documents on file. At the oral proceedings the appellant essentially agreed that the documents did not add anything of substance and offered no line of argumentation based on them. D25 and D26 are therefore not relevant to the decision and the board, making use of its discretionary power under Article 114(2) EPC, has not admitted these documents to the proceedings.

2.5 D27 and D28 were filed on 24.09.08, ie approximately two weeks before the date set for the oral proceedings.

In this respect, the board cannot see any justification for D27 and D28 being filed this late in the proceedings and nor has the appellant offered one. It is therefore not in doubt that D27 and D28 were "not submitted in due time" within the meaning of Article 114(2) EPC.

2.6 D27 is a magazine article from 1975 by Ulrich L. Rohde, an acknowledged expert in the field of radio receiver design. The relevant section of D27 on pages 90 and 91 describes a method for radio reception employing "a double conversion i-f with fixed low-pass filters to give a variable bandwidth and constant slope". In figure 6, the fixed filters are shown as "band-pass filters". From this figure, it appears that D27 discloses a circuit with a similar structure to that of the embodiments of the opposed patent. The text accompanying figure 6 indicates that the circuit is operated to adjust the bandwidth "not by changing the filter, but by changing the frequency offset between two local oscillators".

The board therefore regards D27 as prima facie highly relevant to the presently claimed invention, and, exercising its discretionary power under Article 114(2) EPC in accordance with the above principles, admits it to the proceedings.

2.7 Although the respondent argued that documents D27 and D28 should be disregarded in view of their late filing, given that they could have been filed at a much earlier stage of the procedure, the board for the above reasons comes to the conclusion that the prima facie high relevance of D27 must take precedence, even under the circumstances that D27 was filed after the final date for response set by the board in the communication accompanying the summons to oral proceedings.

2.8 The respondent argued further that the late filing of D27 and D28 had prevented a proper consultation between the representative and the proprietor, and hence in the time available before the oral proceedings it had not been possible to make a proper study of D27 or D28, or to consider the filing of further auxiliary requests. D27 and D28 should therefore not be admitted. However, this argument in the board's view concerns more the respondent's right to be heard (cf. Article 113(1) EPC) which the board has taken account of by remitting the case to the first instance (see below).

2.9 The respondent argued finally that under the revised EPC, it was possible for a patent proprietor to limit the patent at a later date. The board should consider this aspect in deciding whether to admit D27 and D28 However, in the board's view the possibility of limitation allowed by Articles 105a - 105c EPC is a different procedure to the opposition and appeal procedures and governed by its own independent requirements.

2.10 The board is therefore not convinced by the respondent's arguments for not admitting D27.

2.11 The board leaves it to the discretion of the opposition division whether or not to admit D28.

3. Remittal

3.1 As noted above, the board finds D27 prima facie highly relevant. It is therefore not in a position to accede to the respondent's main request which is to dismiss the appeal.

3.2 The board has accordingly addressed the question of whether or not it should itself consider D27 with regard to inventive step or should remit the case to the department of first instance. In this respect, even if the patent proprietor has no automatic right of remittal after the citation of a new document (cf. for example T 402/01, first decision, paragraphs 8 and 9, not published), the patent proprietor's right to be heard in accordance with Article 113(1) EPC may require remittal when the new document alters the legal and factual framework of the case significantly and a "fresh case" results. In the present case, in the board's view, the request for revocation based on lack of inventive step with respect to the combination of D6 and D27 constitutes such a fresh case.

3.3 The appellant argued that the matters to be discussed involving D27 were not technically complex and could be discussed before the board at the oral proceedings.

The board however considers that for the aforementioned reasons remittal is the more appropriate step in the present circumstances, particularly as the respondent has declared its intention to submit new claims in the proceedings before the opposition division. The right to two instances is deemed to take precedence here over the need for procedural economy, and also rules out the possibility of continuing the appeal proceedings in writing.

3.4 In view of the above, the board exercises its discretion under Article 111(1) EPC and remits the case to the opposition division for further prosecution.

3.5 As the case is to be remitted, there is no need for the board to consider the claims of any of the auxiliary requests.

4. Costs

Under Article 104(1) EPC, each party to the opposition procedure shall bear the costs it has incurred, unless the opposition division, for reasons of equity, orders a different apportionment of costs. The board observes that the filing of D27 at a late stage and its subsequent admission to the proceedings has until now not resulted in an increase of costs to the respondent, since the oral proceedings would have been held in any case. However, it is probable that as a result of the case being remitted, the respondent will incur an increase in costs in defending its patent in comparison with the costs which would have arisen if D27 had been filed in due time. The question of a different apportionment of costs is however a matter for the opposition division.