Method and apparatus for delta modulator and sigma delta modulator

• US 6,498,572 B1
• Filed: 07/30/2001
• Issued: 12/24/2002
• Est. Priority Date: 06/18/2001
• Status: Expired due to Fees

• Current Assignee: Singapore The National University of
• Original Assignee: National University of Singapore
• Inventors: Lye, Kin Mun, Joe, Jurianto
• Primary Examiner(s): Tokar, Michael
• Assistant Examiner(s): NGUYEN, LINH V
• Application Number:
  US09/919,079
• Publication Number:
  US 20020196168A1
• Time in Patent Office: 512 Days
• Field of Search: 341/143, 341/133, 341/111, 341/113, 341/118, 341/120, 341/166
• US Class Current: 341/143
• CPC Class Codes: H03M 1/508 the pulse width modulator being of the self-oscillating type

Abstract

According to the invention, oscillating signals are generated from analog signals by providing an analog signal having a variable slope or amplitude to a circuit with a variable operating point and having a transfer function characterized by an unstable operating region bounded by a first and a second stable operating region. The unstable operating region contains a first and a second reference point. The circuit is capable of producing an oscillating signal having a variable duty cycle, the duty cycle increasing as the variable operating point is positioned closer to the first reference point, the duty cycle decreasing as the variable operating point is positioned closer to the second reference point. The variable operating point is positioned substantially within the unstable region to produce the oscillating signal. The positioning of the operating point relative to the first and the second reference points is a function of the variable slope or amplitude of the analog signal. The oscillating signal is capable of being used to directly or indirectly generate a delta modulation or sigma delta modulation signal corresponding to the analog signal.

Claims

1. A method for generating oscillating signals from analog signals comprising:

providing an analog signal having a variable slope to a circuit with a variable operating point and having a transfer function characterized by an unstable operating region bounded by a first and a second stable operating region, said unstable operating region being symmetric about an origin point of said transfer function, said unstable operating region containing a first and a second reference point, said circuit capable of producing an oscillating signal having a variable duty cycle, said duty cycle increasing as said variable operating point is positioned closer to said first reference point, said duty cycle decreasing as said variable operating point is positioned closer to said second reference point; and

positioning said variable operating point substantially within said unstable region to produce said oscillating signal, said positioning of said variable operating point being dependent on said variable slope of said analog signal,

wherein said positioning of said operating point relative to said first and said second reference points is a function of said variable slope of said analog signal,

wherein said oscillating signal is capable of being used to directly or indirectly generate a delta modulation signal corresponding to said analog signal.

2. The method of claim 1 wherein said first and said second reference points can be adjusted to provide a desired dynamic range of said circuit.

3. The method of claim 1 wherein a more positive value of said slope of said analog signal corresponds to a closer positioning of said variable operating point relative to one of said first and said second reference points, and wherein a more negative value of said slope of said analog signal corresponds to a closer positioning of said variable operating point relative to another of said first and said second reference points.

4. The method of claim 1 wherein said variable operating point at or near said origin point corresponds to said duty cycle being at or near 50%.

5. The method of claim 1 wherein said oscillating signal comprises a plurality of pulses.

6. The method of claim 1 further comprising a step of generating said delta modulation signal from said oscillating signal.

7. An apparatus for generating oscillating signals from analog signals comprising:

a circuit with a variable operating point and having a transfer function characterized by an unstable operating region bounded by a first and a second stable operating region, said unstable operating region containing a first and a second reference point, said unstable operating region symmetric about an origin of said transfer function, said circuit capable of producing an oscillating signal having a variable duty cycle, said duty cycle increasing as said variable operating point is positioned closer to said first reference point, said duty cycle decreasing as said variable operating point is positioned closer to said second reference point; and

an input to provide an analog signal having a variable slope to said circuit, wherein said variable operating point is positioned substantially within said unstable region to produce said oscillating signal, wherein positioning of said variable operating point relative to said first and said second reference points corresponds to said variable slope of said analog signal;

wherein said oscillating signal is capable of being used to directly or indirectly generate a delta modulation signal corresponding to said analog signal.

8. The apparatus of claim 7 wherein said first and said second reference points can be adjusted to provide a desired dynamic range of said circuit.

9. The apparatus of claim 7 wherein a more positive value of said slope of said analog signal corresponds to a closer positioning of said variable operating point relative to one of said first and said second reference points, and wherein a more negative value of said slope of said analog signal corresponds to a closer positioning of said variable operating point relative to another of said first and said second reference points.

10. The apparatus of claim 7 wherein said variable operating point at or near said origin corresponds to said duty cycle being at or near 50%.

11. The apparatus of claim 7 wherein said oscillating signal comprises a plurality of pulses.

12. A system for generating oscillating signals from analog signals comprising:

means for providing an analog signal having a variable amplitude to a circuit with a variable operating point and having a transfer function characterized by an unstable operating region bounded by a first and a second stable operating region, said unstable operating region symmetric about an origin of said transfer function, said unstable operating region containing a first and a second reference point, said circuit capable of producing an oscillating signal having a variable duty cycle, said duty cycle increasing as said variable operating point is positioned closer to said first reference point, said duty cycle decreasing as said variable operating point is positioned closer to said second reference point; and

means for positioning said variable operating point substantially within said unstable region to produce said oscillating signal, wherein positioning of said variable operating point relative to said first and said second reference points corresponds to said variable amplitude of said analog signal;

wherein said oscillating signal is capable of being used to directly or indirectly generate a delta modulation signal corresponding to said analog signal.

13. A method for generating oscillating signals from analog signals comprising:

providing an analog signal having a variable amplitude to a circuit with a variable operating point and having a transfer function characterized by an unstable operating region bounded by a first and a second stable operating region, said unstable operating region symmetric about an origin point of said transfer function, said unstable operating region containing a first and a second reference point, said circuit capable of producing an oscillating signal having a variable duty cycle, said duty cycle increasing as said variable operating point is positioned closer to said first reference point, said duty cycle decreasing as said variable operating point is positioned closer to said second reference point; and

positioning said variable operating point substantially within said unstable region to produce said oscillating signal, wherein positioning of said variable operating point relative to said first and said second reference points corresponds to said variable amplitude of said analog signal;

wherein said oscillating signal is capable of being used to directly or indirectly generate a sigma delta modulation signal corresponding to said analog signal.

14. The method of claim 13 wherein said first and said second reference points can be adjusted to provide a desired dynamic range of said circuit.

15. The method of claim 13 wherein a more positive value of said amplitude of said analog signal corresponds to a closer positioning of said variable operating point relative to one of said first and said second reference points, and wherein a more negative value of said amplitude of said analog signal corresponds to a closer positioning of said variable operating point relative to another of said first and said second reference points.

16. The method of claim 13 wherein said variable operating point at or near said origin point corresponds to said duty cycle being at or near 50%.

17. The method of claim 13 wherein said oscillating signal comprises a plurality of pulses.

18. An apparatus for generating oscillating signals from analog signals comprising:

a circuit with a variable operating point and having a transfer function characterized by an unstable operating region bounded by a first and a second stable operating region, said unstable operating region being symmetric about an origin of said transfer function, said unstable operating region containing a first and a second reference point, said circuit capable of producing an oscillating signal having a variable duty cycle, said duty cycle increasing as said variable operating point is positioned closer to said first reference point, said duty cycle decreasing as said variable operating point is positioned closer to said second reference point; and

an input to provide an analog signal having a variable amplitude to said circuit, wherein said variable operating point is positioned substantially within said unstable region to produce said oscillating signal, wherein positioning of said variable operating point relative to said first and said second reference points corresponds to said variable amplitude of said analog signal;

wherein said oscillating signal is capable of being used to directly or indirectly generate a sigma delta modulation signal corresponding to said analog signal.

19. The apparatus of claim 18 wherein said first and said second reference points can be adjusted to provide a desired dynamic range of said circuit.

20. The apparatus of claim 18 wherein a more positive value of said amplitude of said analog signal corresponds to a closer positioning of said variable operating point relative to one of said first and said second reference points, and wherein a more negative value of said amplitude of said analog signal corresponds to a closer positioning of said variable operating point relative to another of said first and said second reference points.

21. The apparatus of claim 18 wherein said variable operating point at or near said origin corresponds to said duty cycle being at or near 50%.

22. The apparatus of claim 18 wherein said oscillating signal comprises a plurality of pulses.

23. A system for generating oscillating signals from analog signals comprising:

means for providing an analog signal having a variable amplitude to a circuit with a variable operating point and having a transfer function characterized by an unstable operating region bounded by a first and a second stable operating region, said unstable operating region symmetric about an origin point of said transfer function, said unstable operating region containing a first and a second reference point, said circuit capable of producing an oscillating signal having a variable duty cycle, said duty cycle increasing as said variable operating point is positioned closer to said first reference point, said duty cycle decreasing as said variable operating point is positioned closer to said second reference point; and

means for positioning said variable operating point substantially within said unstable region to produce said oscillating signal, wherein positioning of said variable operating point relative to said first and said second reference points corresponds to said variable amplitude of said analog signal;

wherein said oscillating signal is capable of being used to directly or indirectly generate a sigma delta modulation signal corresponding to said analog signal.