Cascaded Nth order (N>2) feedforward sigma-delta modulators
AssigneeTapani Ritoniemi
InventorsTapani Ritoniemi, Teppo Karema, Hannu Tenhunen
Life of this patent
Estimating the term…
Abstract
The invention relates to a method for cascading two or more feedforward-type sigma-delta modulators, and a modulator system comprising at least two cascaded modulators (1, 2). According to the invention, each subsequent modulator (2) in the cascade quantizes the integrated signal estimate error (e) of the preceding modulator (1), the quantized error (e') is differentiated (3) and subtracted (6) from the quantized output signal (D") of the preceding modulator (1).
Claims9
A method of cascading at least two feedforward sigma-delta modulators, comprising the steps of:
- producing an integrated signal estimate of a primary signal, in a first feedforward sigma-delta modulator;
- producing an integrated signal estimate error associated with said integrated signal estimate;
- quantizing the integrated signal estimate error, in a second feedforward sigma-delta modulator;
- differentiating the quantized error;
- and
- subtracting the differentiated quantized error from the integrated signal estimate.
A feedforward sigma-delta modulator system comprising:
- a first feedforward sigma-delta modulator which integrates and quantizes a primary signal, said first feedforward sigma-delta modulator including:
- at least two integration stages, each of said integration stages having an associated output signal;
- quantizing means for quantizing said output signals of said integration stages to thereby produce an integrated signal estimate of said primary signal;
- and
- means, responsive to said at least two integration stages, for providing an integrated signal estimate error associated with said integrated signal estimate;
- a second feedforward sigma-delta modulator, operatively connected to said first feedforward sigma-delta modulator, which integrates and quantizes said integrated signal estimate error, including:
- at least two integration stages, each of said integration stages producing an associated output signal;
- and
- quantizing means, responsive to said at least two integration stages, for quantizing said output signals of said integration stages to thereby produce a quantized integrated signal estimate error;
- differentiating means, responsive to said second feedforward sigma-delta modulator, for differentiating the quantized integrated signal estimate error, said differentiating means having a transfer function substantially equal to the inverse function of a common transfer function of said at least two integration stages of said first feedforward sigma-delta modulator;
- means, responsive to said first feedforward sigma-delta modulator, for delaying said integrated signal estimate by an amount corresponding to a delay associated with said second feedforward sigma-delta modulator;
- and
- means, responsive to said differentiating means and to said means for delaying said integrated signal estimate, for subtracting said differentiated quantized integrated signal estimate error from said delayed integrated signal estimate.
Dependencies are inferred from the claim text.