Filters and filter chains
AssigneeCirrus Logic, Inc.
InventorJohn P. Lesso
Life of this patent
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Abstract
An apparatus, comprising: an audio input for receiving an input audio signal; an tuning input for receiving a tuning signal; a filter chain comprising a plurality of filters for filtering the audio signal to produce a filtered input audio signal, the filter chain comprising: a first filter module operating at a first sampling rate; and a second filter module operating at a second sampling rate greater than the first sampling rate, wherein a phase response of the first filter module is dependent on the tuning input and wherein a magnitude response of the first filter module is substantially independent of the tuning input.
Claims23
An audio filter system comprising:
- an oversampled filter chain, the filter chain comprising a plurality of audio filter modules, wherein a first filter module of the plurality of audio filter modules running at a lowest sample rate of the chain is arranged to receive a tuning signal and to adjust the phase response of the first filter module based on the tuning signal such that pre-ringing and/or post-ringing of the filter chain is varied.
A filter module comprising:
- a first filter configured to receive an input signal and provide a first filtered signal, and
- a second filter configured to receive the first filtered signal and provide a second filtered signal as an output signal,
- wherein the first and second filters present a combined filter response for the filter module, the second filter arranged to receive a tuning signal and dynamically adjust a level of pre-ringing of the filter module based on the tuning signal, while maintaining a substantially constant magnitude response of the filter module.
A filter module comprising:
- a first filter configured to receive an input signal and provide a first filtered signal,
- a plurality of second filters configured to receive the first filtered signal and provide a plurality of second filtered signals, the plurality of second filters having different phase responses, and
- a multiplexer configured to receive the plurality of second filtered signals and provide an output signal selected from the plurality of second filtered signals, wherein the first filter and the selected second filter present a combined filter response for the filter module,
- wherein the multiplexer is arranged to receive a tuning signal and to select one of the plurality of second filtered signals to be output based on the tuning signal.
Dependencies are inferred from the claim text.