Motorola Corporation

Sergio Liberman

Vladimir Koifman

Yachin Afek

A noise cancellation circuit for use with a digital signal includes a plurality of equally weighted cells (,) for providing an analogue output signal (,) in dependence upon the value of the digital signal. A switching arrangement (,) dynamically switches a number of the plurality of cells according to a sequencing scheme, which comprises a first sequence arranged to switch each of the plurality of cells (,) an equal number of times, and a second sequence arranged to define one of the plurality of cells (,) as a starting position for the first sequence. In this way low frequency tone generation within the analogue output signal is substantially eliminated.

Sequencing scheme for reducing low frequency tone generation in an analogue output signal

A noise cancelling circuit (10) is used with a D/A converter, the converter including a first modulator (11) and a data output. The circuit (10) has an error measuring arrangement (12, 13, 14) for measuring a quantization error signal of the modulator (11). A filter (19) receives the error signal end provides a fired error signal. A filter compensator (17) is coupled to the data output and provides a compensated output. A scaler (15) is coupled to receive the filtered error signal and provides a scaled filtered error signal. A second modulator (16) is coupled to receive the scaled filtered error signal and provides a single bit stream of error data. A summing arrangement (18) sums the single bit stream of error data and the compensated output from the first modulator and provides a corrected output, such that the error signal is filtered, sealed and modulated end the data output is compensated such that the corrected output is obtained having a substantially reduced quantization error.

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Natania, Israel

Sergio Liberman