Digital demodulation utilizing frequency equalization

• US 7,085,315 B1
• Filed: 04/15/2002
• Issued: 08/01/2006
• Est. Priority Date: 04/15/2002
• Status: Expired due to Fees

• Current Assignee: VIXS Systems Incorporated (Pixelworks Incorporated)
• Original Assignee: VIXS Incorporated
• Inventors: Kelton, James R
• Primary Examiner(s): Tran, Khanh
• Assistant Examiner(s): Ahn, Sam K.
• Application Number:
  US10/122,784
• Time in Patent Office: 1,569 Days
• Field of Search: 375/229, 375/232, 375/233, 375/234, 375/235, 375/236, 375/260, 375/261, 375/285, 370/206, 370/210, 708/323
• US Class Current: 375/219
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/03522 Frequency domain
• CPC Class Codes: H04L 25/03159 operating in the frequency domain H04L25/03165, H04L25/03178 take precedence

Abstract

A method and apparatus for digital demodulation for use in a wireless communication device include processing that begins by performing a fast Fourier transform to convert a plurality of time domain symbol components representing inbound data into a plurality of frequency domain symbol components. The processing continues by frequency domain equalizing at least some of the plurality of frequency domain symbol components based on a dynamic compensation control signal to dynamically compensate for adverse transmission characteristics of the plurality of time domain symbol components. The processing then continues by generating a plurality of estimated symbols and a plurality of error values for the plurality of compensated frequency domain symbol components. The processing then continues by generating the dynamic compensation control signal based on at least one of the plurality of error values, the plurality of frequency domain symbol components and the plurality of compensated frequency domain symbol components.

Claims

1. A wireless communication device comprises:

transmitter section operably coupled to convert outbound data into outbound radio frequency (RF) signals;

receiver section operably coupled to convert inbound RF signals into inbound data, wherein the receiver section includes a digital demodulator that includes;

fast Fourier transform module operably coupled to convert a plurality of time domain symbol components representing the inbound data into a plurality of frequency domain symbol components;

frequency-domain equalizing module operably coupled to dynamically compensate for adverse transmission characteristics of the plurality of time domain symbol components by adjusting frequency characteristics of at least some of the plurality of frequency domain symbol components in accordance with a dynamic compensation control signal to produce a plurality of compensated frequency domain symbol components, wherein the dynamic compensation control signal includes dynamic updates of coefficients for each of the at least some of the plurality of frequency domain symbol components and wherein the frequency-domain equalizing module includes first frequency domain equalizer operably coupled to compensate for adverse frequency characteristics of the plurality of time domain symbol components that are induced by the receiver section to produce a plurality of partially compensated frequency domain symbol components, and second frequency domain equalizer operably coupled to produce the plurality of compensated frequency domain symbol components by compensating the plurality of partially compensated frequency domain symbol components for adverse frequency characteristics of the plurality of time domain symbol components induced by a channel on which the plurality of time domain symbol components was received in accordance with the dynamic compensation control signal;

slicer operably coupled to generate a plurality of estimated symbol values and a plurality of error values from the plurality of compensated frequency domain symbol components; and

fixed filter feedback module operably coupled to determine the dynamic compensation control signal based on at least one of;

the plurality of error values, the plurality of frequency domain symbol components and the plurality of compensated frequency domain symbol components.

2. The wireless communication device of claim 1, wherein the first frequency domain equalizer further comprises:

a plurality of fixed single-tap filters operably coupled to filter the plurality of frequency domain symbol components.

3. The wireless communication device of claim 1, wherein the second frequency domain equalizer further comprises:

a plurality of programmable filters operably coupled to filter the plurality of partially compensated frequency domain symbol components, wherein coefficients of the plurality of programmable filters are established in accordance with the dynamic compensation control signal.

4. The wireless communication device of claim 3, wherein the fixed filter feedback module further comprises:

temporal and frequency weighting module operably coupled to determined a plurality of weighted offsets for the plurality of compensated frequency domain symbol components, wherein each of the plurality of weighted offsets indicates of at least one of time and frequency error of a corresponding one of the plurality of compensated frequency domain symbol components; and

smoothing filter operably coupled to filter the plurality of weighted offsets to produce the dynamic compensation control signal.

5. The wireless communication device of claim 4, wherein the smoothing filter further comprises:

N-tap filter that performs a filtering function of

6. The wireless communication device of claim 5, wherein the smoothing filter further comprises:

interpreting module operably coupled to generate an indication when an adjacent symbol component of the plurality of frequency domain symbol components has a negligible symbol value, wherein the interpreting module provides the indication to the N-tap filter such that for a current one of the plurality of frequency domain symbol components, the N-tap filter filters the current one of the plurality of frequency domain symbol components based on at least one of;

H_iF=H_i and

7. A wireless communication device comprises:

transmitter section operably coupled to convert outbound data into outbound radio frequency (RF) signals;

receiver section operably coupled to convert inbound RF signals into inbound data, wherein the receiver section includes a digital demodulator that includes;

fast Fourier transform module operably coupled to convert a plurality of time domain symbol components representing the inbound data into a plurality of frequency domain symbol components;

first frequency domain equalizer operably coupled to compensate for adverse frequency characteristics of the plurality of time domain symbol components that are induced by the receiver section to produce a plurality of partially compensated frequency domain symbol components;

second frequency domain equalizer operably coupled to produce a plurality of compensated frequency domain symbol components by compensating the plurality of partially compensated frequency domain symbol components for adverse frequency characteristics of the plurality of time domain symbol components induced by a channel on which the plurality of time domain symbol components was received in accordance with a dynamic compensation control signal;

slicer operably coupled to generate a plurality of estimated symbol values and a plurality of error values from the plurality of compensated frequency domain symbol components; and

feedback module operably coupled to generate the dynamic compensation control signal by filtering at least one of the plurality of error values, the plurality of estimated symbol values, and the plurality of compensated frequency domain symbol components.

8. The wireless communication device of claim 7, wherein the first frequency domain equalizer further comprises:

a plurality of fixed single-tap filters operably coupled to filter the plurality of frequency domain symbol components.

9. The wireless communication device of claim 7, wherein the second frequency domain equalizer further comprises:

a plurality of programmable filters operably coupled to filter the plurality of partially compensated frequency domain symbol components, wherein coefficients of the plurality of programmable filters are established in accordance with the dynamic compensation control signal.

10. The wireless communication device of claim 7, wherein the feedback module further comprises:

temporal and frequency weighting module operably coupled to determined a plurality of weighted offsets for the plurality of compensated frequency domain symbol components, wherein each of the plurality of weighted offsets indicates of at least one of time and frequency error of a corresponding one of the plurality of compensated frequency domain symbol components; and

smoothing filter operably coupled to filter the plurality of weighted offsets to produce the dynamic compensation control signal.

11. The wireless communication device of claim 10, wherein the smoothing filter further comprises:

N-tap filter that performs a filtering function of

12. The wireless communication device of claim 11, wherein the smoothing filter further comprises:

interpreting module operably coupled to generate an indication when an adjacent symbol component of the plurality of frequency domain symbol components has a negligible symbol value, wherein the interpreting module provides the indication to the N-tap filter such that for a current one of the plurality of frequency domain symbol components, the N-tap filter filters the current one of the plurality of frequency domain symbol components based on at least one of;

H_iF=H_i and

13. A method of digital demodulation in a radio receiver, the method comprises:

performing a fast Fourier transform on a plurality of time domain symbol components representing the inbound data to produce a plurality of frequency domain symbol components;

performing frequency-domain equalization on at least some of the plurality of frequency domain symbol components in accordance with a dynamic compensation control signal to produce a plurality of compensated frequency domain symbol components such that adverse transmission frequency characteristics of the plurality of time domain symbol components are dynamically compensated, wherein the dynamic compensation control signal includes dynamic updates of coefficients for each of the at least some of the plurality of frequency domain symbol components and wherein the performing frequency-domain equalization includes compensating for adverse frequency characteristics of the plurality of time domain symbol components that are induced by the radio receiver to produce a plurality of partially compensated frequency domain symbol components, and producing the plurality of compensated frequency domain symbol components by compensating the plurality of partially compensated frequency domain symbol components for adverse frequency characteristics of the plurality of time domain symbol components induced by a channel on which a radio frequency signal embodying the plurality of time domain symbol components was received in accordance with the dynamic compensation control signal;

generating a plurality of estimated symbol values and a plurality of error values from the plurality of frequency domain symbol components; and

determining the dynamic compensation control signal based on at least one of;

the plurality of error values, the plurality of frequency domain symbol components, and the plurality of compensated frequency domain symbol components.

14. The method of claim 13, wherein the producing the plurality of compensated frequency domain symbol components further comprises:

establishing coefficients in accordance with the dynamic compensation control signal to filtering the plurality of partially compensated frequency domain symbol components.

15. The method of claim 14, wherein the determining the dynamic compensation control signal further comprises:

determining a plurality of weighted offsets for the plurality of compensated frequency domain symbol components, wherein each of the plurality of weighted offsets indicates of at least one of time and frequency error of a corresponding one of the plurality of compensated frequency domain symbol components; and

smoothing the plurality of weighted offsets to produce the dynamic compensation control signal.

16. The method of claim 15, wherein the smoothing the plurality of weighted offsets further comprises:

performing a filtering function of

17. The method of claim 16, wherein the smoothing the plurality of weighted offsets further comprises:

generating an indication when an adjacent symbol component of the plurality of frequency domain symbol components has a negligible symbol value; and

filtering, based on the indication, a current one of the plurality of frequency domain symbol components based on at least one of;

H_iF=H_i and

18. A digital demodulation for use in a radio receiver, the digital demodulator comprises:

processing module; and

memory operably coupled to the processing module, wherein the memory includes operational instructions that cause the processing module to;

performing a fast Fourier transform on a plurality of time domain symbol components representing the inbound data to produce a plurality of frequency domain symbol components;

performing frequency-domain equalization on at least some of the plurality of frequency domain symbol components in accordance with a dynamic compensation control signal to produce a plurality of compensated frequency domain symbol components such that adverse transmission frequency characteristics of the plurality of time domain symbol components are dynamically compensated by;

compensating for adverse frequency characteristics of the plurality of time domain symbol components that are induced by the radio receiver to produce a plurality of partially compensated frequency domain symbol components; and

producing the plurality of compensated frequency domain symbol components by compensating the plurality of partially compensated frequency domain symbol components for adverse frequency characteristics of the plurality of time domain symbol components induced by a channel on which a radio frequency signal embodying the plurality of time domain symbol components was received in accordance with the dynamic compensation control signal;

wherein the dynamic compensation control signal includes dynamic updates of coefficients for each of the at least some of the plurality of frequency domain symbol components;

generating a plurality of estimated symbol values and a plurality of error values from the plurality of frequency domain symbol components; and

determining the dynamic compensation control signal based on at least one of;

the plurality of error values, the plurality of frequency domain symbol components, and the plurality of compensated frequency domain symbol components.

19. The digital demodulator of claim 18, wherein the memory further comprises operational instructions that cause the processing module to produce the plurality of compensated frequency domain symbol components by:

establishing coefficients in accordance with the dynamic compensation control signal to filtering the plurality of partially compensated frequency domain symbol components.

20. The digital demodulator of claim 19, wherein the memory further comprises operational instructions that cause the processing module to determine the dynamic compensation control signal by:

determining a plurality of weighted offsets for the plurality of compensated frequency domain symbol components, wherein each of the plurality of weighted offsets indicates of at least one of time and frequency error of a corresponding one of the plurality of compensated frequency domain symbol components; and

smoothing the plurality of weighted offsets to produce the dynamic compensation control signal.

21. The digital demodulator of claim 20, wherein the memory further comprises operational instructions that cause the processing module to smooth the plurality of weighted offsets by:

performing a filtering function of

22. The digital demodulator of claim 21, wherein the memory further comprises operational instructions that cause the processing module to smooth the plurality of weighted offsets by:

generating an indication when an adjacent symbol component of the plurality of frequency domain symbol components has a negligible symbol value; and

filtering, based on the indication, a current one of the plurality of frequency domain symbol components based on at least one of;

H_iF=H_i and