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US 7,142,819 B1Granted
Circuits and methods for controlling switching noise in switched-mode circuits
AssigneeCirrus Logic, Inc.
InventorsChang Yong Kang, John Laurence Melanson
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Abstract
A method of controlling noise in a pulse width modulation circuit includes varying a sample frequency and a range of information levels, wherein each sample within a data sample stream at the sample frequency represents a level within the range of information levels, to shift in frequency noise generated at the sample frequency during encoding of the data sample stream into pulse width modulated patterns.
Claims11
A method of controlling noise in a pulse width modulation circuit comprising:
- selecting between first and second operating modes;
- in response to an input signal received in the first operating mode:
- generating at the sample frequency a data sample stream, wherein each sample within the data sample stream represents a level within a range of information level;
- and
- encoding the data sample stream into a stream of pulse width modulated data patterns at the sample frequency, wherein encoding the data sample stream generates noise at a frequency proportional to the sample frequency;
- and
- in response to an input signal received in the second operating mode:
- generating at another sample frequency another data sample stream, wherein each sample within the another data stream represents a level within another range of information levels, and wherein the another sample frequency differs from the sample frequency and the another range of information levels differs from the range of information levels;
- and
- encoding the another data sample stream at the another sample frequency into a stream of pulse width modulated data patterns at the another sample frequency, wherein encoding the another data stream generates noise shifted to a frequency which is an integer multiple of the another sample frequency.
7 more elements
A method of controlling noise in a pulse width modulation system comprising:
- receiving a radio frequency signal within a selected radio frequency band;
- selecting a sample frequency and a number of information levels per sample for generating an audio data sample stream, wherein the sample frequency and the number of information levels per sample are selected to avoid generation of interference in the selected radio frequency band during subsequent encoding of the audio data sample stream into pulse width modulated patterns;
- generating the audio data sample stream having the selected sample frequency and the selected number of information levels from the radio frequency signal;
- encoding the data sample stream into the pulse width modulated data patterns at the sampling frequency;
- receiving another radio frequency signal within another frequency band;
- and
- in response to receiving another radio frequency signal, generating another data sample stream with another sample frequency and another number of information levels per sample, wherein the another sample frequency and the another number of information levels per sample differ from the sample frequency and the number of information levels per sample and are selected to avoid generation of interference in the another radio frequency band during subsequent encoding of the another sample stream into pulse width modulated patterns.
4 more elements
Dependencies are inferred from the claim text.