Yamaha Corporation

Masamitsu Yamamura

Akira Usui

Shigenobu Kimura

Yusuke Yamamoto

Junji Torii

Lenichi Takeuchi

A digital filter performs a predetermined arithmetic operation on input digital data inputted thereto in time-series manner by the predetermined first sampling period to thereby generate output digital data corresponding to a second sampling frequency which is N (where N denotes an integral number) times larger than the predetermined first sampling frequency. This digital filter provides a synchronizing signal generating circuit and an operation control circuit. The synchronizing signal generating circuit detects the predetermined first sampling period of the input digital data to thereby generate a synchronizing signal having the second sampling frequency. The operation control circuit is activated by its internal clock which is asynchronous with the input digital data. This operation control circuit starts to perform its operation processes when the synchronizing signal is supplied thereto, thereafter it terminates the operation processes when a predetermined step number is completed.

Digital filter capable of sample rate alteration

A .DELTA..SIGMA. modulation type 1-bit digital-to-analog conversion circuit includes an addition circuit for adding feedback digital data to input multi-bit digital data to provide results of addition, an integration circuit for integrating the results of addition provided by the addition circuit, a quantizer for quantizing output of the integration circuit to provide 1-bit digital data, and a circuit for providing analog data corresponding to the input multi-bit digital data on the basis of the 1-bit digital data. A bit of a predetermined order and bits of orders lower than the predetermined order in the feedback data are respectively made zero and bits of orders higher than the predetermined order only in the feedback data are added by the addition circuit. By feeding back only high order bits of feedback data for addition, the feedback addition is simplified and computation time thereby is shortened.

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Hamamatsu, Japan

Masamitsu Yamamura