Invention Grant
- Patent Title: Over-sampling digital processing path that emulates Nyquist rate (non-oversampling) audio conversion
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Application No.: US15099293Application Date: 2016-04-14
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Publication No.: US09936282B2Publication Date: 2018-04-03
- Inventor: Dylan Alexander Hester , Bala Vishnu Shankar Rao
- Applicant: Cirrus Logic International Semiconductor Ltd.
- Applicant Address: US TX Austin
- Assignee: Cirrus Logic, Inc.
- Current Assignee: Cirrus Logic, Inc.
- Current Assignee Address: US TX Austin
- Agency: Norton Rose Fulbright US LLP
- Main IPC: H03G5/00
- IPC: H03G5/00 ; H04R1/22

Abstract:
The behavior of a NOS DAC and an analog filter may be emulated by electronic components of an integrated circuit (IC) by upsampling data and applying a digital filter to the upsampled data. For example, the IC may include a zero-order-hold circuit that upsamples data from a first input sample rate to a second, higher input rate. The upsampled data may be passed to an Asynchronous Sample Rate Converter (ASRC) that performs further upsampling (e.g., from 8*Fs-64*Fs). The upsampled data may be passed to a digital low pass filter. The digital low pass filter may emulate, for example, a response of a fifth order Butterworth analog filter to mimic the effect of analog processing. The IC may integrate the upsampling circuit, the low pass digital filter, a digital-to-analog converter (DAC) and an amplifier to provide an audio solution for playing high-fidelity music in a mobile device.
Public/Granted literature
- US20170303032A1 OVER-SAMPLING DIGITAL PROCESSING PATH THAT EMULATES NYQUIST RATE (NON-OVERSAMPLING) AUDIO CONVERSION Public/Granted day:2017-10-19
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