Method for tuning a bandpass analog-to-digital converter and associated architecture

• US 6,819,274 B2
• Filed: 04/14/2003
• Issued: 11/16/2004
• Est. Priority Date: 04/14/2003
• Status: Active Grant

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Khoini-Poorfard, Ramin, Krone, Andrew W.
• Primary Examiner(s): Tokar, Michael
• Assistant Examiner(s): Nguyen, Linh V
• Application Number:
  US10/412,961
• Publication Number:
  US 20040201508A1
• Time in Patent Office: 582 Days
• Field of Search: 341/118, 341/155, 341/143, 341/141, 341/110, 341/120, 341/144, 375/350, 375/327, 375/332, 375/347, 375/279, 375/281, 375/150, 375/326, 375/147, 375/343, 375/206, 375/208, 375/209, 375/210, 455/511, 455/132, 455/140, 455/142, 455/144
• US Class Current: 341/141
• CPC Class Codes: H03J 3/26 the circuits being coupled so as to form a bandpass filter
• CPC Class Codes: H03L 7/18 using a frequency divider or counter in the loop H03L7/20, H03L7/22 take precedence

Abstract

Methods and architectures for tuning bandpass analog-to-digital converters (ADCs) are disclosed that can be used, for example, with receiver architectures and associated methods that are also disclosed. The notch of the bandpass ADC can be tuned to the desired channel frequency by adjusting the notch to reduce noise energy in the output signal through a feedback process that adjusts the tuning signal. In addition, a master-slave approach can be implemented to tune a tunable bandpass filter configured as a slave circuit based upon the tuning adjustments made to the master bandpass ADC circuit. In addition, receiver architectures and associated methods are disclosed that utilize coarse analog tune circuitry to provide initial analog coarse tuning of desired channels within a received spectrum signal, such as a set-top box signal spectrum for satellite communications.

Claims

1. A method for tuning a tunable bandpass analog-to-digital converter (ADC), comprising:

calibrating the bandpass ADC utilizing a predetermined calibration signal as an analog input signal;

converting the analog input signal to a digital output signal using a tunable bandpass analog-to-digital converter (ADC), the bandpass ADC utilizing a tuning signal to tune the bandpass ADC by adjusting a notch location for the bandpass ADC;

digitally processing the digital output signal to generate a baseband output signal;

determining a noise energy level in the baseband output signal;

modifying the tuning signal applied to the bandpass ADC; and

repeating the converting, processing, determining and modifying steps to adjust the tuning signal so that the noise energy level in the baseband output signal tends to be reduced;

completing the repeating step by selecting a final calibration value for the tuning signal; and

then

operating the tunable ADC by receiving a channel signal spectrum as the analog input signal and keeping the tuning signal set to the final calibration value, wherein the channel signal spectrum comprises a plurality of channels within a frequency range, wherein the tunable bandpass ADC is tuned to a desired channel within the channel signal spectrum, and wherein the baseband output signal is representative of the desired channel.

2. The method of claim 1, wherein the calibration step is utilized each time a new channel is desired to be tuned.

3. The method of claim 2, wherein the predetermined calibration signal is ground.

4. The method of claim 1, wherein the tuning signal is configured to be selected from a predetermined number of discrete settings, and the modifying step comprises selecting one of these discrete settings for the final calibration value.

5. The method of claim 4, wherein the discrete setting selected is a setting that tends to minimize the noise energy level in the baseband output signal.

6. A method for tuning a tunable bandpass analog-to-digital converter (ADC), comprising:

converting an analog input signal to a digital output signal using a tunable bandpass analog-to-digital converter (ADC), the bandpass ADC utilizing a tuning signal to tune the bandpass ADC by adjusting a notch location for the bandpass ADC;

digitally processing the digital output signal to generate a baseband output signal;

determining a noise energy level in the baseband output signal;

modifying the tuning signal applied to the bandpass ADC; and

repeating the converting, processing, determining and modifying steps to adjust the tuning signal so that the noise energy level in the baseband output signal tends to be reduced;

wherein the analog input signal comprises a channel signal spectrum including a plurality of channels within a frequency range;

wherein the tunable bandpass ADC is tuned to a desired channel within the channel signal spectrum;

wherein the baseband output signal is representative of the desired channel; and

wherein the signal spectrum comprises a channel signal spectrum from satellite communications, the satellite channel signal spectrum comprising a plurality of transponder channels with each transponder channel including a plurality of program channels.

7. The method of claim 6, wherein the frequency range for the channel signal spectrum comprises 950 MHz to 2150 MHz.

8. The method of claim 6, further comprising filtering the analog input signal with a tunable bandpass filter prior to the converting step.

9. A method for tuning a tunable bandpass analog-to-digital converter (ADC), comprising:

filtering an analog input signal with a tunable bandpass filter,

converting the filtered analog input signal to a digital output signal using a tunable bandpass analog-to-digital converter (ADC), the bandpass ADC utilizing a tuning signal to tune the bandpass ADC by adjusting a notch location for the bandpass ADC,

digitally processing the digital output signal to generate a baseband output signal;

determining a noise energy level in the baseband output signal;

modifying the tuning signal applied to the bandpass ADC; and

repeating the converting, processing, determining and modifying steps to adjust the tuning signal so that the noise energy level in the baseband output signal tends to be reduced;

wherein the method further comprises configuring the tunable bandpass ADC as a master circuit and configuring the tunable bandpass filter as a slave circuit such that the tunable bandpass filter is created from circuit elements that are similar to those used in the tunable bandpass ADC, and utilizing a slave tuning signal to tune the tunable bandpass filter, the slave tuning signal matching the master tuning signal used to tune the tunable bandpass ADC.

10. A tunable analog-to-digital conversion system, comprising:

a tunable bandpass analog-to-digital converter (ADC) coupled to receive an analog input signal and configured to utilize a tuning signal to tune a notch location for the bandpass ADC;

digital processing circuitry coupled to receive a digital output signal from the bandpass ADC and configured to output a baseband output signal;

an energy detector coupled to receive the baseband output signal and configured to determine a noise energy level in the baseband output signal;

control circuitry coupled to the energy detector and having the tuning signal as an output, the

control circuitry being configured to adjust the tuning signal so that the noise energy level in the baseband output signal tends to be reduced; and

input selection circuitry coupled to the input of the bandpass ADC, the input selection circuitry configured to allow a predetermined calibration signal or a channel signal spectrum as the input signal to the bandpass ADC, and the input selection circuitry configured to receive a selection control signal from the control circuitry;

wherein the channel signal spectrum comprises a plurality of channels within a frequency range;

wherein the tunable bandpass ADC is configured to be tuned to a desired channel within the channel signal spectrum; and

wherein the baseband output signal is representative of the desired channel.

11. The tunable analog-to-digital conversion system of claim 10, wherein the control circuitry is further configured to select the predetermined calibration signal as the input signal, to determine a final calibration value for the tuning signal, and then to select the channel signal spectrum as the input signal while keeping the tuning signal set to the final calibration value.

12. The tunable analog-to-digital conversion system of claim 11, wherein the signal spectrum comprises a channel signal spectrum from satellite communications.

13. The tunable analog-to-digital conversion system of claim 11, wherein the control circuitry is further configured to select the tuning signal from a predetermined number of discrete settings, and wherein the discrete setting selected as the final calibration value represents the one that tends to minimize the noise energy level in the baseband output signal.

14. The tunable analog-to-digital conversion system of claim 10, further comprising a tunable bandpass filter coupled to receive the analog input signal and configured to provide a filtered analog input signal to the tunable bandpass ADC.

15. A tunable analog-to-digital conversion system, comprising:

a tunable bandpass filter coupled to receive an analog input signal and configured to provide a filtered analog input signal to the tunable bandpass ADC;

a tunable bandpass analog-to-digital converter (ADC) coupled to receive the filtered analog input signal and configured to utilize a tuning signal to tune a notch location for the bandpass ADC;

digital processing circuitry coupled to receive a digital output signal from the bandpass ADC and configured to output a baseband output signal;

an energy detector coupled to receive the baseband output signal and configured to determine a noise energy level in the baseband output signal; and

control circuitry coupled to the energy detector and having the tuning signal as an output, the control circuitry being configured to adjust the tuning signal so that the noise energy level in the baseband output signal tends to be reduced, and

wherein the tunable bandpass ADC is configured as a master circuit and the tunable bandpass filter is configured as a slave circuit such that the tunable bandpass filter is created from circuit elements that are similar to those used in the tunable bandpass ADC, and

wherein a slave tuning signal is utilized to tune the tunable bandpass filter, the slave tuning signal matching the master tuning signal used to tune the tunable bandpass ADC.

16. A receiver for tuning a channel within a signal spectrum, comprising:

local oscillator (LO) circuitry having a channel selection signal as an input and having a coarse-tune analog mixing signal as an output, the output mixing signal being selected from a plurality of predetermined output mixing signals depending upon a desired channel to be tuned;

analog coarse tune circuitry having the coarse-tune analog mixing signal as an input and having a signal spectrum as an input, the signal spectrum including a plurality of channels within a frequency range, and the analog coarse tune circuitry being configured to use the coarse tune analog mixing signal to output a coarsely tuned signal spectrum;

a tunable bandpass analog-to-digital converter (ADC) coupled to receive the coarsely tuned signal spectrum as an input and configured to utilize a tuning signal to tune a notch location for the bandpass ADC, the tunable bandpass ADC being tuned to a desired channel within the plurality of channels;

digital processing circuitry coupled to receive a digital output signal from the bandpass ADC and configured to output a baseband output signal representative of the desired channel;

an energy detector coupled to receive the baseband output signal and configured to determine a noise energy level in the baseband output signal; and

control circuitry coupled to the energy detector and having the tuning signal as an output, the control circuitry being configured to adjust the tuning signal so that the noise energy level in the baseband output signal tends to be reduced.

17. The receiver of claim 16, wherein the digital processing circuitry comprises a digital mixer and a channel select filter.

18. The receiver of claim 16, wherein the signal spectrum comprises a channel signal spectrum from satellite communications.

19. The receiver of claim 18, further comprising input selection circuitry coupled to the input of the tunable bandpass ADC, the input selection circuitry configured to allow a predetermined calibration signal or the signal spectrum as the input to the tunable bandpass ADC, and the input selection circuitry configured to receive a selection control signal from the control circuitry.

20. The receiver of claim 19, wherein the control circuitry is further configured to select the predetermined calibration signal as the input signal, to determine a final calibration value for the tuning signal, and then to operate to select the channel signal spectrum as the input signal while keeping the tuning signal set to the final calibration value.

21. The receiver of claim 16, further comprising a tunable bandpass filter coupled to receive the coarsely tuned signal spectrum and configured to provide a filtered coarsely tuned signal spectrum to the tunable bandpass ADC.

22. The receiver of claim 21, wherein the tunable bandpass ADC is configured as a master circuit and the tunable bandpass filter is configured as a slave circuit such that the tunable bandpass filter is created from circuit elements that are similar to those used in the tunable bandpass ADC, and wherein a slave tuning signal is utilized to tune the tunable bandpass filter, the slave tuning signal matching the master tuning signal used to tune the tunable bandpass ADC.

23. A satellite set-top box for tuning a program channel within a satellite signal spectrum using a receiver that includes a tunable bandpass analog-to-digital converter (ADC), comprising:

a receiver configured to receive a satellite signal spectrum including a plurality of transponder channels and to tune a transponder channel within the signal spectrum, each transponder channel including a plurality of program channels, comprising;

local oscillator (LO) circuitry having a channel selection signal as an input and having a coarse-tune analog mixing signal as an output, the output mixing signal being selected from a plurality of predetermined output mixing signals depending upon a desired channel to be tuned;

analog coarse tune circuitry having the coarse-tune analog mixing signal as an input and having a signal spectrum as an input, the signal spectrum including a plurality of channels within a frequency range, and the analog coarse tune circuitry being configured to use the coarse-tune analog mixing signal to output a coarsely tuned signal spectrum;

a tunable bandpass analog-to-digital converter (ADC) coupled to receive the coarsely tuned signal spectrum as an input and configured to utilize a tuning signal to tune a notch location for the bandpass ADC, the tunable bandpass ADC being tuned to a desired channel within the plurality of channels;

digital processing circuitry coupled to receive a digital output signal from the bandpass ADC and configured to output a baseband output signal representative of the desired channel;

an energy detector coupled to receive the baseband output signal and configured to determine a noise energy level in the baseband output signal; and

control circuitry coupled to the energy detector and having the tuning signal as an output, the control circuitry being configured to adjust the tuning signal so that the noise energy level in the baseband output signal tends to be reduced; and

a demodulator coupled to receive a digital baseband output signal from the receiver representative of a tuned transponder channel, the demodulator being configured to tune a program channel within the tuned transponder channel and to provide the tuned program channel as an output.

24. The satellite set-top box of claim 23, wherein the digital processing circuitry comprises a digital mixer and a channel select filter.

25. The satellite set-top box of claim 23, further comprising input selection circuitry coupled to the input of the tunable bandpass ADC, the input selection circuitry configured to allow a predetermined calibration signal or the signal spectrum as an input to the tunable bandpass ADC, and the input selection circuitry configured to receive a selection control signal from the control circuitry.

26. The satellite set-top box of claim 25, wherein the control circuitry is further configured to select the predetermined calibration signal as the input signal, to determine a final calibration value for the tuning signal, and then to operate to select the channel signal spectrum as the input signal while keeping the tuning signal set to the final calibration value.

27. The satellite set-top box of claim 23, further comprising a tunable bandpass filter coupled to receive the coarsely tuned signal spectrum and configured to provide a filtered coarsely tuned signal spectrum to the tunable bandpass ADC.

28. The satellite set-top box of claim 27, wherein the tunable bandpass ADC is configured as a master circuit and the tunable bandpass filter is configured as a slave circuit such that the tunable bandpass filter is created from circuit elements that are similar to those used in the tunable bandpass ADC, and wherein a slave tuning signal is utilized to tune the tunable bandpass filter, the slave tuning signal matching the master tuning signal used to tune the tunable bandpass ADC.