A/D converter with improved resolution by sampling a superposed signal

• US 6,831,576 B2
• Filed: 11/13/2003
• Issued: 12/14/2004
• Est. Priority Date: 11/13/2002
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Geiger, Albert, Rieger, Reinhard, Fehrenbach, Michael, Landsgesell, Juergen
• Primary Examiner(s): Tokar, Michael
• Assistant Examiner(s): Mai, Lam T.
• Application Number:
  US10/713,335
• Publication Number:
  US 20040135713A1
• Time in Patent Office: 397 Days
• Field of Search: 341/131, 341/155, 341/120, 341/126
• US Class Current: 341/131
• CPC Class Codes: H03M 1/0639 using dither, e.g. using triangular or sawtooth waveforms for increasing resolution H03M1/201
• CPC Class Codes: H03M 1/12 Analogue/digital converters H03M1/001 – H03M1/10 take precedence

Abstract

A method for improving the resolution of an A/D converter and/or a converter system having an S/H device and an A/D converter is described. In order to improve the resolution of the A/D converter, an auxiliary signal is superposed on an analog signal, and the superposed signal is sampled and converted into digital output values using the A/D converter. Based on the digital output values, it is possible to determine an output value having higher resolution, e.g., by averaging.

Claims

1. A method for improving a resolution of an A/D converter, comprising:

receiving an analog signal;

superposing an auxiliary signal on the analog signal, whereby a superposed signal is produced;

sampling the superposed signal using an S/H device, whereby sampled values are produced;

performing an A/D conversion of the sampled values, whereby a number of digital output values are produced; and

determining a high-resolution digital output value based on the digital output values;

wherein the high-resolution digital output value is determined from a ratio of one of those of the digital output values having a higher bit value and those of the digital output values having a lower bit value to a total number of the digital output values that were input.

2. The method as recited in claim 1, wherein:

the high-resolution digital output value is determined by averaging the digital output values.

3. The method as recited in claim 1, wherein:

the auxiliary signal includes a periodic signal.

4. A method for improving a resolution of an A/D converter, comprising:

receiving an analog signal;

superposing an auxiliary signal on the analog signal, whereby a superposed signal is produced;

sampling the superposed signal using an S/H device, whereby sampled values are produced;

performing an A/D conversion of the sampled values, whereby a number of digital output values are produced; and

determining a high-resolution digital output value based on the digital output values;

wherein the auxiliary signal has a peak-to-peak amplitude that is greater than or equal to a resolution of a least significant bit of the digital output values.

5. A method for improving a resolution of an A/D converter, comprising:

receiving an analog signal;

superposing an auxiliary signal on the analog signal, whereby a superposed signal is produced;

sampling the superposed signal using an S/H device, whereby sampled values are produced;

performing an A/D conversion of the sampled values, whereby a number of digital output values are produced; and

determining a high-resolution digital output value based on the digital output values;

wherein the auxiliary signal includes one of a sine wave signal and a square-wave signal.

6. A method for improving a resolution of an A/D converter, comprising:

receiving an analog signal;

superposing an auxiliary signal on the analog signal, whereby a superposed signal is produced;

sampling the superposed signal using an S/H device, whereby sampled values are produced;

performing an A/D conversion of the sampled values, whereby a number of digital output values are produced; and

determining a high-resolution digital output value based on the digital output values;

wherein a sampling frequency at which the superposed signal is sampled by the S/H device is selected in such a way that a beat is produced.

7. An A/D converter system, comprising:

a device for superposing an auxiliary signal on an analog signal, whereby a superposed signal is produced;

an S/H device for sampling the superposed signal, whereby sampled values are produced;

an A/D converter that converts the sampled values into binary output values; and

a processing unit that determines a high-resolution output value based on the binary output values;

wherein the device for superposing the auxiliary signal includes one of a capacitor and a current source.

8. The A/D converter system as recited in claim 7, wherein:

the processing unit determines the high-resolution output value by averaging the binary output values.

9. An A/D converter system, comprising:

a device for superposing an auxiliary signal on an analog signal, whereby a superposed signal is produced;

an S/H device for sampling the superposed signal, whereby sampled values are produced;

an A/D converter that converts the sampled values into binary output values; and

a processing unit that determines a high-resolution output value based on the binary output values;

wherein the processing unit determines the high-resolution digital output value from a ratio of one of those of the digital output values having a higher bit value and those of the digital output values having a lower bit value to a total number of the digital output values that were input.

10. The A/D converter system as recited in claim 9, wherein:

the device for superposing the auxiliary signal includes one of a capacitor and a current source.