A method of designing a digital filter for example for use in an FBMC/OQAM telecommunications system, with a target overlapping factor and meeting a specified signal to interference ratio is described, whereby a candidate filter design defined by an impulse response, satisfying the Nyquist criterion and having an overlapping factor higher than the target is selected, and the time and frequency coefficients of its impulse response inverted to define a new filter design; and

truncating the impulse response defining said new filter design to the minimum number of coefficients achieving said specified signal to interference ratio.

A method of filtering includes generating a random value by a random number generator circuit, filtering a first signal by a first filter to form a filtered first signal, dithering the filtered first signal using the random value to form a dithered first signal, filtering a second signal by a second filter to form a filtered second signal, and dithering the filtered second signal using the random value to form a dithered second signal.

An infinite impulse response filter includes a plurality of lower order filter stages and a random number generator circuit. The plurality of lower order filter stages include a first filter stage coupled to a second filter stage. The random number generator circuit includes a first output coupled to the first filter stage and a second output coupled to the second filter stage. The random number generator circuit is configured to generate the same random value at both the first output and the second output. The infinite impulse response filter is an n.sup.th-order filter. The respective order of each of the lower order filter stages is less than n.

An infinite impulse response filter includes a plurality of lower order filter stages and a random number generator circuit. The plurality of lower order filter stages include a first filter stage coupled to a second filter stage. The random number generator circuit includes a first output coupled to the first filter stage and a second output coupled to the second filter stage. The random number generator circuit is configured to generate the same random value at both the first output and the second output. The infinite impulse response filter is an n.sup.th-order filter. The respective order of each of the lower order filter stages is less than n.

A processing element for implementation in a digital signal processing system is provided. The processing element is configured to receive a first data stream comprising a plurality of digital values where each value represents a sample of an analog signal. The processing element is further configured to receive a second data stream comprising a series of digital values where each value represents a sample of the analog signal. The processing element is configured to filter the first data stream via a first Farrow-structured fractional delay (FD) filter and output a filtered first data stream; filter the second data stream via a second Farrow-structured FD filter and output a filtered second data stream; and temporarily store values from the second data stream and output the stored values to the first Farrow-structured FD filter so that the stored values can be used to filter the first data stream.

A process for processing a digital signal comprises constructing a fractional order control system that models a desired frequency response by assembling filter components from a filter component library. The filter components are defined by Laplace functions that include a non-integer control order having a variable fractional scaling exponent. Then, the fractional order control system is adjusted by applying an altitude exponent to the fractional order control system, and the altitude exponent changes a magnitude of the frequency response without changing a width of a transition band of the frequency response. An input signal in the digital frequency domain is received and processed based upon the fractional order control system to generate a digital output that is conveyed.

A method of filtering includes generating a random value by a random number generator circuit, filtering a first signal by a first filter to form a filtered first signal, dithering the filtered first signal using the random value to form a dithered first signal, filtering a second signal by a second filter to form a filtered second signal, and dithering the filtered second signal using the random value to form a dithered second signal.

The present invention relates broadly to a method of digitally filtering a signal, such as an audio signal, using a digital filter. The digital filter includes a plurality of neighbouring sample points broken into zones having different frequency content or frequency ranges. The zones adjacent one another may have neighbouring sample points in common. Generally each zone has at least same distinct frequencies compared with other zones. That is, the zones are roughly dependent on the frequency content. The invention in its preferred form involves combining values for two or more of the neighbouring sample points for select of the zones depending on its frequency content. The values are combined so as to provide a modified zone having substantially the same number of sample points as the select zone. The modified zones together provide a modified filter to be applied to the signal.

A process for processing a digital signal comprises constructing a fractional order control system that models a desired frequency response by assembling filter components from a filter component library. The filter components are defined by Laplace functions that include a non-integer control order having a variable fractional scaling exponent. Then, the fractional order control system is adjusted by applying an altitude exponent to the fractional order control system, and the altitude exponent changes a magnitude of the frequency response without changing a width of a transition band of the frequency response. An input signal in the digital frequency domain is received and processed based upon the fractional order control system to generate a digital output that is conveyed.

A method of designing a digital filter for example for use in an FBMC/OQAM telecommunications system, with a target overlapping factor and meeting a specified signal to interference ratio is described, whereby a candidate filter design defined by an impulse response, satisfying the Nyquist criterion and having an overlapping factor higher than the target is selected, and the time and frequency coefficients of its impulse response inverted to define a new filter design; and truncating the impulse response defining said new filter design to the minimum number of coefficients achieving said specified signal to interference ratio.