The European Patent Office decided that a computer-implemented method with mathematical steps for simulating the performance of a circuit subject to 1/f noise is technical. Here are the practical takeaways from the decision T 1227/05 (Circuit simulation I/Infineon Technologies) of 13.12.2006 of Technical Board of Appeal 3.5.01:
This European patent application aimed at simulating or modelling the performance of a circuit under the influence of a 1/f noise, i.e. a stochastic process with a frequency spectrum whose intensity is inversely proportional to a power beta of the frequency.
The solution is based on the notion that 1/f noise can be simulated by feeding suitable random numbers into the circuit model. The application derives the numbers from a Gaussian stochastic process BFBM (fractional Brownian motion as a function of time) whose derivative is known to have a 1/f spectrum. The BFBM process and its derivative are characterised in particular by a covariance function and a covariance matrix.
Claim 1 (main request)Computer-implemented method for the numerical simulation of a circuit with a step size delta which is subject to 1/f noise, wherein:
– the circuit is described by a model (1) featuring input channels (2), noise input channels (4) and output channels (3);
– the performance of the input channels (2) and the output channels (3) is described by a system of differential equations or algebroid differential equations;
– an output vector (OUTPUT) is calculated for an input vector (INPUT) present on the input channels (2) and for a noise vector (NOISE) y of 1/f-distributed random numbers present on the noise input channels (4); and
– the noise vector y is generated by the following steps:
– determining a desired spectral value beta of the 1/f noise,
– determining a value n for the number of random numbers to be generated for a 1/f noise,
– determining an intensity constant const,
– forming a covariance matrix C of dimension (n x n), each element e(i,j) of covariance matrix C being determined by the following equation:
where i,j = 1, …, n
– forming the Cholesky decomposition L of covariance matrix C,
the following steps being performed for each sequence of random numbers to be generated for a 1/f noise:
– forming a vector x of length n from random numbers having a Gaussian (0,1) distribution,
– generating the vector y of length n of the desired 1/f-distributed random numbers by multiplying the Cholesky decomposition L by the vector x.
Is it patentable?
First of all, the Board briefly touched on the first patentability hurdle (“patent-eligibility”), which is basically no issue at the EPO:
To be eligible for patent protection it is necessary and sufficient for the claimed method to have technical character (see e.g. T 930/05 – Modellieren eines Prozessnetzwerks/ XPERT, not published in OJ EPO). As the method according to independent claim 1 or 2 is computer-implemented, it uses technical means and by that very token has technical character, see in particular T 258/03 – Auction method/HITACHI (OJ EPO 2004, 575, Reasons 4.1 to 4.7) and T 914/02 – Core loading arrangement/GENERAL ELECTRIC (not published in OJ EPO, Reasons 2.3.4 to 2.3.6).
Then, the Board assessed which of the other features of the claim actually contributed to the technical character of the invention, since only those features can establish an inventive step according to the Comvik approach. With respect to the feature “simulation of a circuit subject to 1/f noise”, the Board came to a positive assessment:
Beyond its implementation, a procedural step may contribute to the technical character of a method only to the extent that it serves a technical purpose of the method.
The board is persuaded that simulation of a circuit subject to 1/f noise constitutes an adequately defined technical purpose for a computer-implemented method, provided that the method is functionally limited to that technical purpose.
However, the Board also emphasized that the technical purpose has to be made specific in the claim:
The metaspecification of an (undefined) technical purpose (simulation of a “technical system”, see original claim 4), on the other hand, could not be considered adequate, as the purpose of a claim in this context is not to quote the technical character requirement, but to identify clear features supported by the description which meet that requirement.
Besides that, the Board also made a more general remark on the patentability of computer-implemented simulation methods:
Specific technical applications of computer-implemented simulation methods are themselves to be regarded as modern technical methods which form an essential part of the fabrication process and precede actual production, mostly as an intermediate step. In view of this development it must be assumed that the outlay for implementing a technical product will increasingly shift to the numerical simulation phase, while final implementation of the simulation result in the actual manufacture of the product will entail no or only comparatively little extra innovation effort. In that light, such simulation methods cannot be denied a technical effect merely on the ground that they do not yet incorporate the physical end product.
Therefore, the Board ultimately decided that all features relevant to circuit simulation, including the steps expressed by formulae, contribute to the technical character of the simulation method and thus could potentially establish an inventive step. Since the question of inventive step itself had not been discussed before the Examining Division, the Board remitted the case back to first instance.
You can read the whole decision here: T 1227/05 (Circuit simulation I/Infineon Technologies) of 13.12.2006