Claims
- 1. A machine comprising an oscillator for producing a non-linear segment waveform for use in a conversion application from the set of conversion applications consisting of analog-to-digital conversion and digital-to-analog conversion, said non-linear segment waveform having the following properties:
a. said non-linear segment waveform consists of comparison-useful segments and comparison-irrelevant segments b. said comparison-useful segments are substantially equal to segments of desired non-linear waveform shapes c. said comparison-useful segments are, in said conversion application, waveform segments which are not treated as linear waveform segments d. said comparison-irrelevant segments comprise a non-zero portion of said non-linear segment waveform whereby said oscillator may produce a waveform which includes some segments of desired, accurately-known non-linear waveform shape and which also includes some segments of unknown or undesired waveform shape, the former segments, for instance, sinusoidal segments, being suitable for processing in said conversion application with accurate knowledge of their non-linear waveform shape taken into account, the latter segments, for instance, unchanging or insufficiently well-known time-varying segments, being tolerated but not used for comparison, so that the waveform may have high distortion globally, but low distortion locally.
- 2. The machine of claim 1 in which said non-linear segment waveform is periodic, whereby said comparison-useful segments occur repeatedly over time, whereby said comparison-irrelevant segments have a non-zero duty cycle, and whereby said non-linear segment waveform can be generated using low-cost oscillatory generation means.
- 3. The machine of claim 1 in which:
a. said oscillator is fabricated on a first integrated circuit chip b. non-oscillator conversion circuitry is also fabricated on said first integrated circuit chip whereby said oscillator and other conversion circuitry of said conversion application, for instance, comparators, counters, or digital registers, are fabricated on the same integrated circuit chip, resulting in manufacturing cost savings, operating cost savings, or both.
- 4. The machine of claim 3 further including a sensor fabricated on said first integrated circuit chip, whereby said oscillator, said non-oscillation conversion circuitry, and said sensor can be fabricated on the same integrated circuit chip, such as may be desired in an imaging sensor array that is part of a digital imaging system.
- 5. The machine of claim 3 further including a transducer fabricated on said first integrated circuit chip, whereby said oscillator, said non-oscillation conversion circuitry, and said transducer can be fabricated on the same integrated circuit chip, such as may be desired in an transducer array that is part of an image display system.
- 6. The machine of claim 1 in which said conversion application is analog-to-digital conversion, said machine further including:
a. a first comparator having a first comparator input, a second comparator input, and a first comparator output b. means for providing said non-linear segment waveform as an input to said first comparator input during a first conversion cycle whereby said non-linear segment waveform can be used as a reference analog signal level compared by said first comparator to a signal applied to said second comparator input during said first conversion cycle, with a change in said first comparator output indicating when the difference between the comparator inputs reaches zero during said first conversion cycle.
- 7. The machine of claim 6 further including:
a. a second comparator having a third comparator input, a fourth comparator input, and a second comparator output b. means for providing said non-linear segment waveform as an input to said third comparator input during said first conversion cycle whereby said non-linear segment waveform can be used as a reference analog signal level for both said first comparator and said second comparator during said first conversion cycle, so that said non-linear segment waveform can be shared in parallel analog-to-digital converters.
- 8. The machine of claim 1 in which said conversion application is digital-to-analog conversion, said machine further including:
a. a first analog hold-capable circuit such as a track-and-hold circuit or a sample-and-hold circuit b. means for causing said first analog hold-capable circuit to hold a first value of said non-linear segment waveform reached during a first conversion cycle whereby said non-linear segment waveform can be used as a reference analog signal level the value of which is tracked and then held or sampled and then held during said first conversion cycle.
- 9. The machine of claim 8 further including:
a. a second analog hold-capable circuit b. means for causing said second analog hold-capable circuit to hold a second value of said non-linear segment waveform reached during said first conversion cycle whereby said non-linear segment waveform can be used as a reference analog signal which is shared by both said first analog hold-capable circuit and said second analog hold-capable circuit during said first conversion cycle, so that said non-linear segment waveform can be shared in parallel digital-to-analog converters.
- 10. The machine of claim 1 in which said non-linear segment waveform is a truncated sinusoid, whereby saturated peaks and valleys of said truncated sinusoid may be comparison-useless segments, while transitions between said saturated peaks and valleys of said truncated sinusoid may be comparison-useful segments.
- 11. The machine of claim 1 in which said oscillator comprises:
a. an operational amplifier having an inverting input, a non-inverting input, and an output b. a positive feedback network connecting said output and said non-inverting input, said positive feedback network providing a positive feedback gain between said non-inverting input and said output which is frequency-dependent c. a negative feedback network connecting said output and said inverting input whereby an op-amp circuit using a Wien Bridge can be the means for generating said non-linear segment waveform.
- 12. The machine of claim 11 in which the negative feedback gain of said negative feedback network connecting said output and said inverting input is greater than the maximum positive feedback gain, whereby said output is forced to saturate.
- 13. The machine of claim 11 in which said positive feedback network comprises:
a. a first positive network leg connected between said output and said non-inverting input b. a second positive network leg connected between said non-inverting input and a reference node whereby a simple bridge circuit can set said positive feedback gain.
- 14. The machine of claim 13 in which said reference node is ground.
- 15. The machine of claim 13 in which said reference node is not ground.
- 16. The machine of claim 13 in which:
a. said first positive network leg comprises a first resistor in series with a first capacitor, said first resistor having a first resistance value and said first capacitor having a first capacitance value b. said second positive network leg comprises a second resistor in parallel with a second capacitor, said second resistor having said first resistance value and said second capacitor having said first capacitance value whereby said positive feedback network is substantially a Wien Bridge, which requires only one capacitance value and one resistance value, and for which a resonant frequency of maximum positive feedback gain is easily computed or designed for by proper choice of component values.
- 17. The machine of claim 16 in which said negative feedback network comprises a third resistor connected between said output and said inverting input and a fourth resistor connected between said inverting input and either said reference node or a second reference node having substantially the same voltage as said reference node, whereby said negative feedback network is implemented with a simple resistor bridge.
- 18. The machine of claim 17 in which said third resistor and said fourth resistor have values such that the negative feedback gain is greater than three, whereby said negative feedback gain is greater than said positive feedback gain.
- 19. The machine of claim 13 further including a second operational amplifier configured to force said non-inverting input to be a virtual ground.
- 20. The machine of claim 19 in which said reference node is the output of said second operational amplifier.
- 21. The machine of claim 20 in which the output of said second operational amplifier is connected to one end of a leg of said negative feedback network, the other end of which is connected to said inverting input, whereby said second operational amplifier provides a common reference node for both said negative feedback network and said positive feedback network.
- 22. A machine for producing a sinusoidal reference waveform, comprising:
a. a first oscillatory waveform which is a truncated sinusoid at a first fundamental frequency b. as said sinusoidal reference waveform, a second oscillatory waveform which is a filtered version of said first oscillatory waveform, said second oscillatory waveform substantially having less relative attenuation at said first fundamental frequency than at other frequencies, in comparison with relative attenuation at said first fundamental frequency and at other frequencies in said first oscillatory waveform whereby said first oscillatory waveform is a truncated, and hence high-distortion sinusoid at said first fundamental frequency, and whereby said second oscillatory waveform is also a sinusoid at said first fundamental frequency but with lower distortion due to a higher relative gain (or equivalently a lower relative attenuation) at said first fundamental frequency than at other frequencies, a low-distortion sinusoid being produced by filtering a high-distortion sinusoid being particularly useful in integrated circuit implementations where an oscillator must be built using a small part count of components selected from a small library of standard components such as capacitors, resistors, and transistors.
- 23. The machine of claim 22 comprising:
a. a first operational amplifier having a first inverting input, a first non-inverting input, and a first output b. a positive feedback network connecting said first output and said first non-inverting input, said positive feedback network providing a positive feedback gain between said first non-inverting input and said first output, said positive feedback gain being frequency-dependent relatively high at said first fundamental frequency c. a negative feedback network connecting said first output and said first inverting input, said negative feedback network providing a negative feedback gain which is greater than said positive feedback gain whereby an op-amp circuit using frequency-dependent positive feedback can be the means for generating said first oscillatory waveform.
- 24. The machine of claim 23 in which said positive feedback network comprises:
a. a first positive network leg connected between said first output and said first non-inverting input b. a second positive network leg connected between said first non-inverting input and a reference node whereby a simple bridge circuit can set said positive feedback gain.
- 25. The machine of claim 24 in which said reference node is a constant-voltage reference node such as ground.
- 26. The machine of claim 25 in which said second oscillatory waveform is the value of the voltage at said first non-inverting input.
- 27. The machine of claim 25 further including means for filtering the value of the voltage at said first non-inverting input to provide said second oscillatory waveform.
- 28. The machine of claim 24 in which said reference node is not a constant-voltage reference node.
- 29. The machine of claim 28 in which the value of the voltage at said reference node defines said second oscillatory waveform.
- 30. The machine of claim 28 further including means for filtering the value of the voltage at said reference node to provide said sinusoidal reference waveform.
- 31. The machine of claim 24 in which said negative feedback network comprises a third resistor connected between said output and said inverting input and a fourth resistor connected between said inverting input and either said reference node or a second reference node having substantially the same voltage as said reference node, whereby said negative feedback network is implemented with a simple resistor bridge.
- 32. The machine of claim 24 in which:
a. said first positive network leg comprises a first resistor in series with a first capacitor, said first resistor having a first resistance value and said first capacitor having a first capacitance value b. said second positive network leg comprises a second resistor in parallel with a second capacitor, said second resistor having said first resistance value and said second capacitor having said first capacitance value whereby said positive feedback network is substantially a Wien Bridge, which has a single resonant frequency of maximum positive feedback gain, and which requires only one capacitance value and one resistance value, and for which a resonant frequency of maximum positive feedback gain is easily computed or designed for by proper choice of component values.
- 33. The machine of claim 32 which said negative feedback network comprises a third resistor connected between said first output and said first inverting input and a fourth resistor connected between said first inverting input and either said reference node or a second reference node having substantially the same voltage as said reference node, whereby said negative feedback network is implemented with a simple resistor bridge.
- 34. The machine of claim 33 in which said third resistor and said fourth resistor have values such that the negative feedback gain is greater than three, whereby said negative feedback gain is greater than said positive feedback gain.
- 35. The machine of claim 34 further including a second operational amplifier configured to force said non-inverting input to be a virtual ground.
- 36. The machine of claim 35 in which a second output which is the output of said second operational amplifier is said reference node.
- 37. The machine of claim 36 in which the output of said second operational amplifier is connected to one end of a leg of said negative feedback network, the other end of which is connected to said inverting input, whereby said second operational amplifier provides a common reference node for both said negative feedback network and said positive feedback network.
- 38. The machine of claim 36 further including means for filtering the value of said output of said second operational amplifier in order to produce said second oscillatory waveform, whereby one or more filter stages can be used to guarantee suitably low distortion for said sinusoidal reference waveform.
- 39. The machine of claim 38 in which said means for filtering said value of said output of said second operational amplifier comprises:
a. a third operational amplifier having a third inverting input, a third non-inverting input, and a third output b. a first filter network leg consisting of a fifth resistor in series with a third capacitor, where:
i. one end said first filter network leg is connected to said second output of said second operational amplifier ii. the other end of said first filter network leg is connected to said third inverting input iii. said fifth resistor has substantially the same resistance as said first resistor iv. said third capacitor has substantially the same capacitance as said first capacitor c. a second filter network leg consisting of a sixth resistor in parallel with a fourth capacitor, where:
i. one end said second filter network leg is connected to said third inverting input ii. the other end of said second filter network leg is connected to said third inverting input iii. said sixth resistor has substantially the same resistance as said first resistor iv. said fourth capacitor has substantially the same capacitance as said first capacitor d. said third non-inverting input being connected to ground whereby a second Wien bridge provides means for filtering said second output, with bridge components being substantially similar to the components of the Wien bridge which provides positive feedback for said first operational amplifier.
- 40. The machine of claim 22 further including means for changing said first fundamental frequency, whereby said machine can be used to generate sinusoidal reference waveforms of more than one frequency.
- 41. The machine of claim 40 in which said means for changing said first fundamental frequency comprises a circuit comprising one or more members of the set of variable-parameter components consisting of transistors, variable-capacitance capacitors, variable-resistance resistors, and variable-inductance inductors.
- 42. The machine of claim 41 in which sad means for changing said first fundamental frequency comprises a self-adaptive silicon circuit.
- 43. The machine of claim 22 further including means for providing said sinusoidal reference signal to a device under test, whereby said sinusoidal reference signal can be used for calibration of said device under test, possible devices including waveform generators, audio equipment, synthesizers, analog-to-digital converters, and digital-to-analog converters.
- 44. The machine of claim 22 in which:
a. said machine is fabricated on a first integrated circuit chip b. non-oscillator circuitry is also fabricated on said first integrated circuit chip whereby rather than having an oscillator chip and a non-oscillator chip, said machine of claim 22 and non-oscillator circuitry are fabricated on the same integrated circuit chip, resulting in manufacturing cost savings, operating cost savings, or both.
- 45. The machine of claim 44 further including a sensor fabricated on said first integrated circuit chip, whereby said machine of claim 22, said non-oscillator circuitry, and said sensor can be fabricated on the same integrated circuit chip, such as may be desired in an imaging sensor array that is part of a digital imaging system, for instance a CMOS image sensor array.
- 46. The machine of claim 44 further including a transducer fabricated on said first integrated circuit chip, whereby said machine of claim 22, said non-oscillator circuitry, and said transducer can be fabricated on the same integrated circuit chip, such as may be desired in an transducer array that is part of an image display system.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The invention is related to ANALOG-TO-DIGITAL CONVERSION WITH PIECE-WISE NON-LINEAR REFERENCE WAVEFORMS submitted as a separate application by the US PTO by the applicant of the present invention and having filing date Jun. 24, 2002 and filing number 10/179937.