Signal processing method and device

Details Signal processing method and device Signal processing method and device

H - Electricity

04

B

H04B 14/06 (2006.01) H03M 1/08 (2006.01) H03M 3/02 (2006.01) H03M 7/36 (2006.01)

Patent

CA 2274637

The invention relates to digital signal processing and specificly to level control of a pulse density modulated (PDM) signal generated by a sigma-delta modulator. A single-bit pulse density modulated PDM signal is generated by a first sigma-delta modulator (2) being an analog modulator, for instance. Level control is performed by multiplying the single-bit pulse density modulated PDM signal by a multibit multiplier (300) to obtain a multibit number stream, which is reconverted into a single-bit PDM signal by a second digital sigma- delta modulator (4). In accordance with the invention, the performance of the second sigma-delta modulator (4) is better than that of the first sigma-delta modulator (2), as to the signal-to-noise ratio. Thus, the most significant factor in the total signal-to-noise ratio (SNR) is the noise level of the first sigma-delta modulator (2), by which the PDM signal was originally generated. In the subsequent second sigma-delta modulator (4), the PDM signal can then be attenuated as much as is the difference between the SNR performances of the modulators without any decrease in the total signal-to- noise ratio. A relative amplification of the PDM signal is provided in this manner.

La présente invention concerne le traitement de signaux numériques et spécifiquement la régulation du niveau d'un signal modulé en densité d'impulsions (PDM) produit par un modulateur sigma-delta. Un signal PDM à un seul bit est produit par un premier modulateur sigma-delta (2) qui est un modulateur analogique par exemple. La régulation de niveau est effectuée par multiplication du signal PDM à un seul bit par un multiplicateur (300) multibit pour obtenir un flux multibit de nombres qui est reconverti en un signal PDM à un seul bit par un second modulateur sigma-delta (4). Selon la présente invention, la performance du second modulateur sigma-delta (4) est meilleure que celle du premier modulateur sigma-delta (2) pour ce qui est du rapport signal-bruit. Par conséquent, le facteur le plus significatif dans le rapport total signal-bruit est le niveau de bruit du premier modulateur sigma-delta (2) par lequel le signal PDM a été initialement produit. Dans le second modulateur sigma-delta (4), le signal PDM peut être atténué à l'intérieur d'une plage qui est égale à la différence entre les performances de rapport signal-bruit des modulateurs sans aucune baisse du rapport total signal-bruit. Une amplification relative du signal PDM est ainsi obtenue.

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