Adaptive digital spectral compensation and calibration of analog components and transceiver chains

• US 6,724,331 B1
• Filed: 11/26/2002
• Issued: 04/20/2004
• Est. Priority Date: 11/27/2001
• Status: Active Grant

• Current Assignee: Ostendo Technologies Inc.
• Original Assignee: Ellipsis Digital Systems, Inc.
• Inventors: El-Ghoroury, Hussein S., Karsi, Murat F.
• Primary Examiner(s): Young, Brian
• Assistant Examiner(s): LAUTURE, JOSEPH J
• Application Number:
  US10/304,331
• Time in Patent Office: 511 Days
• Field of Search: 341/118, 341/120, 370/335, 370/342, 375/297, 375/345
• US Class Current: 341/118
• CPC Class Codes: H03M 1/0626 by filtering
• CPC Class Codes: H03M 1/1038 by storing corrected or correction values in one or more digital look-up tables H03M1/1057 takes precedence

Abstract

According to one aspect of the invention, an apparatus is provided which includes one or more analog components, an analog to digital (A/D) converter, and a spectral compensator. The operational characteristics of the one or more analog components have variations based on input signal frequency. The one or more analog components perform their corresponding operations with respect to an input analog signal to generate an output analog signal. The analog to digital (A/D) converter is coupled to receive the output analog signal from the one or more analog components and to convert the output analog signal to a digital signal. The spectral compensator is coupled to receive the digital signal generated by the A/D converter and to compensate spectral characteristics of the digital signal based on variations in the operational characteristics of the one or more analog components.

Claims

1. An apparatus comprising:

a spectral compensator coupled to receive a digital input signal;

a digital to analog (D/A) converter coupled to the spectral compensator to receive a digital signal from the spectral compensator and to convert the digital signal to an analog signal; and

one or more analog components coupled to the D/A converter to receive the analog signal from the D/A converter,

the spectral compensator having coefficients determined during, calibration of the one or more analog components to pre-distort the spectral characteristics of the digital signal dependent on the spectral characteristics of the one or more analog components coupled to the D/A converter;

wherein undesired spectral characteristics of the one or more analog components are compensated by the pre-distortion of the spectral compensator.

2. The apparatus of claim 1 wherein the digital input signal is transformed from time domain into frequency domain before being inputted to the spectral compensator.

3. The apparatus of claim 1 wherein the compensated digital signal generated by the spectral compensator is transformed from frequency domain to time domain.

4. The apparatus of claim 1 wherein the spectral compensator is configured to compensate the frequency domain phase and magnitude transfer characteristics of the one or more analog components over a particular bandwidth.

5. A method comprising:

receiving an input digital signal;

pre-distorting spectral characteristics of the input digital signal;

converting the pre-distorted digital signal to an analog signal; and

providing the analog signal to one or more analog components;

the spectral characteristics of the input digital signal being pre-distort using coefficients determined during calibration with the one or more analog components to pre-distort the spectral characteristics of the digital input signal dependent on undesired spectral characteristics of the one or more analog components couple to the D/A converter.

6. The method of claim 5 further including:

transforming the input digital signal from time domain into frequency domain before compensating spectral characteristics of the input digital signal.

7. The method of claim 5 further including:

transforming the compensated digital signal from frequency domain to time domain before converting the compensated digital signal to analog signal.

8. The method of claim 5 wherein undesired spectral characteristics include:

phase and magnitude transfer characteristics of the one or more analog components over a particular bandwidth.

9. An apparatus comprising:

one or more analog components coupled to receive a analog signal;

an analog to digital (A/D) converter coupled to receive an output analog signal from the one or more analog components and to convert the output analog signal to a digital signal; and

a spectral compensator coupled to receive the digital signal generated by the A/D converter;

the spectral compensator having coefficients determined during calibration of the one or more analog components to post-distort the spectral characteristics of the digital signal dependent on the undesired spectral characteristics of the one or more analog components.

10. The apparatus of claim 9 wherein the digital signal generated by the A/D converter is transformed from time domain into frequency domain before being inputted to the spectral compensator.

11. The apparatus of claim 9 wherein the compensated digital signal generated by the spectral compensator is transformed from frequency domain to time domain.

12. The apparatus of claim 9 wherein the spectral compensator is configured to compensate the frequency domain phase and magnitude transfer characteristics of the one or more analog components over a particular bandwidth.

13. A method comprising:

receiving an analog signal from one or more analog components;

converting the analog signal from the one or more analog components to a digital signal; and

compensating spectral characteristics of the digital signal to generate a compensated digital signal using coefficients determined during calibration of the one or more analog components to post-distort the spectral characteristics of the digital signal dependent on the undesired spectral characteristics of the one or more analog components.

14. The method of claim 13 further including:

transforming the digital signal generated by the A/D converter from time domain into frequency domain before compensating spectral characteristics of the digital signal.

15. The method of claim 13 further including:

transforming the compensated digital signal generated by the spectral compensator from frequency domain to time domain.

16. The method of claim 13 wherein compensating spectral characteristics includes:

compensating phase and magnitude transfer characteristics of the one or more analog components over a particular bandwidth.

17. A system comprising:

a transmitter chain including;

a pre-compensator coupled to receive digital signals and perform spectral compensation on the digital signals before the digital signals are converted to analog signals and processed by one or more analog components in the transmitter chain, the digital signals being compensated based on undesired spectral characteristics of the one or more analog components in the transmitter chain using coefficients determined during calibration of the transmitter chain; and

a digital to analog (D/A) converter coupled to receive and convert the compensated digital signals generated by the pre-compensator to analog signals to be processed by the one or more analog components in the transmitter chain; and

a receiver chain including;

an analog to digital (A/D) converter coupled to receive analog signals generated by one or more analog components in the receiver chain and convert the analog signals to digital signals; and

a post-compensator coupled to receive and perform spectral compensation on the digital signals generated by the A/D converter, the digital signals being compensated based on undesired spectral characteristics of the one or more analog components in the receiver chain using coefficients determined during calibration of the transmitter chain.

18. The system of claim 17 wherein the pre-compensator is configured to compensate phase and magnitude transfer characteristics of the one or more analog components in the transmitter chain over a particular bandwidth.

19. The system of claim 17 wherein the post-compensator is configured to compensate phase and magnitude transfer characteristics of the one or more analog components in the receiver chain over a particular bandwidth.

20. The system of claim 17 wherein the digital signals in the transmitter chain are transformed from time domain to frequency domain before being compensated by the pre-compensator and transformed from frequency domain to time domain after being compensated by the pre-compensator.

21. The system of claim 17 wherein the digital signals in the receiver chain are transformed from time domain to frequency domain before being compensated by the post-compensator and transformed from frequency domain to time domain after being compensated by the post-compensator.

22. The system of claim 17 wherein the pre-compensator and post-compensator are coupled with transmit and receive chains used in multi-carrier transceiver systems that utilize frequency domain multi-carrier modulation techniques.

23. The system of claim 17 wherein the transmit and receive chains are coupled through set of loop-back switches coupling the output of the transmit chain to the input of the received chain to allow adaptive calibration of the transmitter and receiver chains using the pre-compensator and post-compensator.

24. An apparatus comprising:

an anti-aliasing filter (AAF) coupled to receive an input analog signal and perform anti-aliasing filtering function on the input analog signal to generate an output analog signal, the output analog signal generated by the AAF having spectral distortion;

an analog to digital (A/D) converter coupled to convert the output analog signal generated by the AAF to a digital signal; and

a spectral compensator unit coupled to receive the digital signal generated by the (A/D) converter and perform a spectral compensation function on the digital signal to compensate for spectral distortion caused by the AAF based on spectral distortion measurements of the digital signal generated by the (A/D) converter, the spectral compensator having coefficients determined during calibration with the AAF.

25. The apparatus of claim 24 wherein the spectral compensator performs compensation of frequency domain amplitude distortion caused by the AAF.

26. The apparatus of claim 24 further including a spectral distortion measurement unit coupled to measure the spectral distortion of the digital signal generated by the (A/D) converter and provide spectral distortion information to the spectral compensator.