Claims
- 1. A digital noise shaper circuit for generating an output digital data stream having predefined noise characteristics and a predefined frequency bandwidth from a multi-bit input digital data stream, said noise shaper comprising;
- a greater than two-pole digital noise-shaping filter network for receiving and processing an error signal to generate said output data stream;
- means responsive to said output stream for generating a feedback signal;
- means responsive to said feedback signal for frequency-shaping said feedback signal; and
- means for digitally adding said multi-bit input digital data stream and said frequency-shaped feedback signal to generate said error signal, so that the combination of said digital filter and said feedback signal shapes quantization noise generated when said noise shaper circuit converts said input digital data stream into said output data stream in order to shift most of said quantization noise to frequencies outside of said predefined frequency bandwith wherein the number of bits in the output digital data stream is less than the number of bits in the input digital data stream.
- 2. A digital noise shaper circuit according to claim 1 wherein said frequency-shaping means comprises a feedback processing network connected between said feedback signal generating means and said adding means.
- 3. A digital noise shaper circuit according to claim 1 wherein said feedback signal generating means is the most significant bit of said output data stream.
- 4. A digital noise shaper circuit according to claim 1 wherein said multi-pole digital filter network is comprised of at least two digital accumulators.
- 5. A digital noise shaper circuit according to claim 1 wherein said multi-pole digital filter network is comprised of a plurality of filter stages, each of said filter stages being comprised of a digital adder with an output connected to a digital accumulator.
- 6. A digital noise shaper circuit for generating a single-bit pulse-density modulated output digital data stream having predefined noise characteristics from a multi-bit input digital data stream, said noise shaper comprising:
- a greater than two-pole digital filter network for receiving and processing an error signal to generate said output data stream;
- a comparator responsive to said output stream for generating a feedback signal;
- means responsive to said feedback signal for frequency-shaping said feedback signal; and
- means for digitally adding said multi-bit input digital data stream and said frequency-shaped feedback signal to generate said error signal.
- 7. A digital noise shaper circuit for generating a single-bit pulse-density modulated output digital data stream having predefined noise characteristics from a multi-bit input digital data stream, said noise shaper comprising:
- a greater than two-pole digital filter network for receiving and processing an error signal to generate said output data stream;
- a comparator responsive to said output stream for generating a feedback signal;
- means responsive to said feedback signal for frequency-shaping said feedback signal comprising means for multiplying said feedback signal by a predetermined digital number; and
- means for digitally adding said multi-bit input digital data stream and said frequency-shaped feedback signal to generate said error signal.
- 8. A digital noise shaper circuit for generating a single-bit pulse-density modulated output digital data stream having predefined noise characteristics from a multi-bit input digital data stream, said noise shaper comprising:
- a greater than two-pole digital filter network for receiving and processing an error signal to generate said output data stream, said multi-pole digital filter network being comprised of a plurality of filter stages, each of said filter stages being comprised of a digital adder with an output connected to a digital accumulator;
- means responsive to said output stream for generating a feedback signal;
- means responsive to said feedback signal for frequency-shaping said feedback signal comprising a plurality of frequency-shaping circuits and said digital adder in each of said filter stages has a first input connected to a filter stage input and a second input connected to one of said frequency-shaping circuits; and
- means for digitally adding said multi-bit input digital data stream and said frequency-shaped feedback signal to generate said error signal.
RELATED APPLICATIONS
This application is a continuation of application Ser. No. 07/498,941, filed Mar. 26, 1990 now abandoned which is a continuation in part of U.S. patent application Ser. No. 07/472,706 filed on Jan. 31, 1990 entitled "SIGMA DELTA MODULATOR" by Paul F. Ferguson, Jr., Apparajan Gameson and Robert W. Adams now U.S. Pat. No. 5,055,843.
US Referenced Citations (8)
Foreign Referenced Citations (1)
Number |
Date |
Country |
0190694 |
Feb 1986 |
EPX |
Non-Patent Literature Citations (5)
Entry |
A 17-bit Oversampling D-to-A Conversion Technology Using Multistage Noise Shaping, Yasuyuki Matsuya, Kuniharu Uchimura, Atsushi Iwata, Takao Kaneko, IEEE Journal of Solid-State Circuits, vol. 24, No. 4, pp. 969-975, Aug., 1989. |
Manfred Dietrich, Signal-to-Noise Ratio Improvement of Interpolative Analog-to-Digital Converters, pp. 66-72. |
Yasuyuki Matsuya, et al., A 16-Bit Oversampling A-to-D Conversion Technology Using Triple-Integration Noise Shaping, Dec. 1987, pp. 921-929, IEEE Journal of Solid-State Circuits. |
Japanese Abstract-Noise Shaping Coder. |
B. P. Agrawal, et al., Specification-Based Design of .epsilon..DELTA.M for A/D and D/A Conversion, pp. 1980-1983. |
Continuations (1)
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498941 |
Mar 1990 |
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Continuation in Parts (1)
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472706 |
Jan 1990 |
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