**Case:**

T_1227/05

**Claimed Subject Matter:**

The purpose of the application is to simulate or model 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 process describes the time dynamics of a physical variable, e.g. electric voltage.

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.

The invention generates a covariance matrix which features the same simple elements as the covariance matrix (equation 2.7) of the derivative of the fractional Brownian motion. A triangular (Cholesky) decomposition of the generated covariance matrix is multiplied by a vector x of random numbers having a Gaussian distribution. Due to the design of the covariance matrix, the resultant random number sequence y forms a 1/f noise source.

**Comments:**

The board held that specific technical applications of computer-implemented simulation methods are themselves to be regarded as modern technical methods which can form an essential part of the fabrication process and precede actual production of a product. Such simulation methods cannot be denied a technical effect merely on the grounds that they do not yet incorporate the physical end product.

The take-away point is that if a simulation is clearly and specifically limited to a narrow technical field (and particular technical features within that field) it is more likely to be found to be technical it itself.

While the invention may be preceded by a mental or mathematical act, the claimed result must not be equated with this act. The present claims relate to a simulation method that cannot be performed by purely mental or mathematical means, not to the thought process that led to that simulation method.

Simulation performs technical functions typical of modern engineering work. It provides for realistic prediction of the performance of a designed circuit and thereby ideally allows it to be developed so accurately that a prototype’s chances of success can be assessed before it is built. The technical significance of this result increases with the speed of the simulation method, as this enables a wide range of designs to be virtually tested and examined for suitability before the expensive circuit fabrication process starts.

Without technical support, advance testing of a complex circuit and/or qualified selection from many designs would not be possible, or at least not in reasonable time. Thus computer-implemented simulation methods for virtual trials are a practical and practice-oriented part of the electrical engineer’s toolkit. What makes them so important is that as a rule there is no purely mathematical, theoretical or mental method that would provide complete and/or fast prediction of circuit performance under noise influences.

For example, 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.

A further fundamental change is to be found in the fact that development and production are increasingly separated, materially and geographically, in a globally distributed industry. In that light, too, the board considers specific patent protection to be appropriate for numerical development tools designed for a technical purpose.