Granted Patent B2

US 7,378,997 · App. 10/594,488 · Granted May 27, 2008

Abstract

Claims (23)

1. A method of reducing inter-symbol interference of a one-bit digital signal stream, the generation of said one-bit digital signal stream comprising the steps of:

converting an input signal to said one-bit digital signal stream with a sigma-delta configuration of a low pass filter having an output coupled to the input of a quantizer whose output is fed back to the input of the low pass filter,

characterized by generating a control signal that is representative of the density of the edges of the one-bit digital signal stream at the output of the quantizer,

multiplying the control signal with said one-bit digital signal stream and

applying the result of the multiplication together with the output of the low pass filter (F) to the input of the quantizer.

2. A one-bit sigma-delta converter for converting an input signal to a one-bit digital signal stream, said converter comprising

a quantizer with an input and an output,

a low pass filter whose output is coupled to the input of the quantizer and whose input is coupled to the output of the quantizer, thereby constituting a feedback arrangement with the quantizer,

means to supply the input signal to the feedback arrangement and

means to derive the one-bit digital signal stream from the output of the quantizer, characterized by an edge-density controller connected to the output of the quantizer for providing a control signal indicative of the density of the edges of the one-bit digital signal stream,

a multiplier for multiplying said control signal with the one-bit digital signal stream of the quantizer and

means for applying the output of the multiplier to the input of the quantizer.

3. A one-bit sigma-delta converter as claimed in claim 2 characterized in that the edge-density controller comprises

an edge-extractor connected to receive the one-bit digital signal stream of the quantizer, and

a second low pass filter receiving the output signal of the edge-extractor and providing said control signal.

4. A one-bit sigma-delta converter as claimed in claim 3 characterized by a reference signal source connected to the second low pass filter for referencing the level of the control signal.

5. A one-bit sigma-delta converter as claimed in claim 3 characterized in that the second low pass filter is an integrator and that the reference signal is applied with a polarity opposite to that of the edge-extractor pulses to the input of the integrator.

6. A multi-bit sigma-delta converter for converting an input signal to a multi-bit digital signal, said converter comprising said converter comprising:

a plurality of interconnected one-bit sigma-delta converters each with a low pass filter in feedback arrangement with one of a plurality of interconnected quantizer means,

means to supply the input signal to said plurality of quantizer means and means to derive the multi-bit digital signal from the outputs of the plurality of quantizer means, characterized in that each of the outputs of the plurality of quantizer means is connected to an edge-density controller for providing a control signal indicative of the edges of the one-bit digital stream at said output,

a multiplier for multiplying said control signal with the one-bit digital stream of said output and

means for applying the result of the multiplication to the respective input of the quantizer means.

7. A storage medium having stored thereon at least one signal track in one-bit digital stream format, characterized in that the number of clock periods comprising an edge in the one-bit digital stream of said signal track is less than 40% of the total number of clock periods of the one-bit digital stream of said signal track.

Assignments (13)