Abstract:
The frequency response of a digital filter, such as a pre-emphasis filter in a signal transmitter having a phase-locked loop, is adjusted using interpolation of the filter coefficients, enabling sets of filter coefficients to be pre-computed or generated as needed in the transmitter. The phase error behavior of the digital filter can be significantly improved.
Abstract:
An apparatus for processing an audio signal is provided. The apparatus comprises a configurable first audio signal processor (110) for processing the audio signal (s 0 ) in accordance with different configuration settings (conf) to obtain a processed audio signal (s 1 ), wherein the apparatus is adapted so that different configuration settings (conf) result in different sampling rates (sr 1 ) of the processed audio signal (s 1 ). The apparatus furthermore comprises n analysis filter bank (120) having a first number (c 1 ) of analysis filter bank channels, a synthesis filter bank (130) having a second number (c 2 ) of synthesis filter bank channels, a second audio processor (140) being adapted to receive and process an audio signal (s 2 ) having a predetermined sampling rate (sr 2 ), and a controller (150) for controlling the first number (c 1 ) of analysis filter bank channels or the second number (c 2 ) of synthesis filter bank channels in accordance with a configuration setting (conf).
Abstract:
L'invention concerne l'amélioration de la bande passante des systèmes physiques. On utilise un filtre à réponse impulsionnelle finie qui est calculé de la manière suivante, à partir du comportement (observé ou connu) du système physique (SP) : on détermine la réponse impulsionnelle a(t) du système physique selon une variable temporelle ou spatiale; on calcule échantillon par échantillon une réponse impulsionnelle b(t) de forme semblable mais comprimée selon l'échelle de la variable t dans un rapport n et dilatée en amplitude dans le même rapport, et on calcule les coefficients d'un filtre à réponse impulsionnelle finie apte à fournir à sa sortie le signal b(t) lorsqu'on applique le signal a(t) à son entrée. Ce filtre à réponse impulsionnelle finie est incorporé au système physique, de préférence à la sortie, pour en améliorer la bande passante dans le rapport n.
Abstract:
A multimode audio amplifier comprises: a mode controller adapted to provide a control signal; and at least one multimode module, wherein each of the multimode modules has a plurality of operating modes, wherein the operating modes are selected in accordance with the control signal, wherein changing the operating modes results in a measurable change in at least one characteristic of the multimode audio amplifier; wherein the characteristics of the multimode audio amplifier consist of signal to noise ratio (SNR); total harmonic distortion and noise (THD+N); input to output delay; power consumption; and efficiency.
Abstract:
An analog-to-digital conversion system has an analog-to-digital converter (300) and a digital-filter system (100). The digital-filter system (100) is connected to the output of the analog-to-digital converter (300). A processor (310) is connected to the output of the digital-filter system (100) so that the processor (310) transparently receives filtered sample data in the native format of the analog-to-digital converter (300). An FIR filter circuit (130) in the digital-filter system (100) is connected to receive data from, and output filtered data to, a sample capture and data-type conversion circuit (120) connected between the analog-to-digital converter (300) and the processor (310). A configuration and control-register circuit (110) is connected to the circuit for sample collection and data-type conversion (120), and to the FIR filter circuit (130), for selectively controlling the operation of the digital filter system (100) according to parameters for data conversion and filter operation passed to the configuration and control-register circuit (110) over a serial interface.
Abstract:
An architecture for cascaded digital filters (104-1, 106-1 to 104-6, 106-6) comprises independently programmable controlling registers and independent interpolating factors (Il to 16); a digital to analog converter (108) for converting the digital signals into analog signals with a constant sampling rate which matches with the interpolating factors of the cascaded digital filters. Each filter (106-1 to 106-6) property (filters order, coefficient symmetry, half- band, and poly-phase) can be programmed independently to support different system requirements and extract maximum throuput from a given hardware. The method of filtering digital signals comprises the steps of determining an interpolation factor of the cascaded digital filters with the lowest number of computations so as to match with the single sampling rate of the digital to analog converter, determining active filters and an interpolation factor of each digital filter in the cascaded digital filters, and determining a mode of operation of the cascaded digital filters.
Abstract:
Techniques are described for sampling rate conversion in the digital domain by up-sampling and down-sampling a digital signal according to a selected intermediate sampling frequency. A prototype anti-aliasing filter that has a bandwidth with multiple factors is stored in memory. The techniques include selecting an intermediate sampling frequency to be an integer multiple of a desired output sampling frequency of a digital signal based on the factors of the prototype filter, and selecting a down-sampling factor to be the same integer associated with the selected intermediate sampling frequency. A filter generator generates an anti-aliasing filter for the selected down-sampling factor based on the prototype filter. A sampling rate converter up-samples the digital signal at an input sampling frequency to the selected intermediate sampling frequency, filters the digital signal with the derived anti-aliasing filter, and down-samples the digital signal by the selected down-sampling factor to the desired output sampling frequency.
Abstract:
Adaptively processing an input signal, such as an input signal of a hearing aid. The input signal is passed through an adaptive time domain filter to produce an output signal. At least one of the input signal and the output signal is used as an analysis signal. The analysis signal is transformed into a transform domain to produce a transformed analysis signal, which is analysed to produce a desired gain for each respective transform domain sub-band. A minimum phase time domain filter characteristic is synthesised which approaches the desired gains. The adaptive filter is updated with the synthesised filter characteristic.