AM digital audio broadcasting with analog signal pre-compensation

• US 6,798,849 B2
• Filed: 12/10/2001
• Issued: 09/28/2004
• Est. Priority Date: 12/10/2001
• Status: Expired due to Term

• Current Assignee: iBiquity Digital Corporation (Xperi Inc.)
• Original Assignee: iBiquity Digital Corporation (Xperi Inc.)
• Inventors: Kroeger, Brian William, Bronder, Joseph Bertram
• Primary Examiner(s): Bayard, Emmanuel
• Application Number:
  US10/012,828
• Publication Number:
  US 20030108123A1
• Time in Patent Office: 1,023 Days
• Field of Search: 375/316, 375/320, 375/322, 375/240.21, 375/240.24, 375/240.28, 375/240.79, 370/208, 370/209, 370/210, 370/203, 348/663, 348/726
• US Class Current: 375/316
• CPC Class Codes: H04H 20/36 for AM broadcasts
• CPC Class Codes: H04H 2201/20 digital audio broadcasting [DAB]
• CPC Class Codes: H04H 60/07 characterised by processes or methods for the generation
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

A method for pre-compensating an analog signal in a composite digital audio broadcasting signal including the analog signal and a plurality of digitally modulated sub-carrier signals, the method comprising the steps of sampling the analog signal to obtain successive blocks of samples, demodulating each of the blocks of samples to obtain a plurality of demodulator outputs, remodulating the demodulator outputs that correspond to the predetermined ones of the digitally modulated sub-carrier signals to produce an error signal, subtracting the error signal from the one of the blocks of samples to produce a pre-compensated block of samples, and combining the pre-compensated block of samples with a plurality of OFDM pulses to produce a compensated composite signal. An apparatus for performing the method is also included.

Claims

1. A method for pre-compensating an analog signal in a composite digital audio broadcasting signal including the analog modulated carrier signal and a plurality of digitally modulated sub-carrier signals, the method comprising the steps of:

sampling the analog signal to obtain successive blocks of samples;

demodulating each of the blocks of samples to obtain a plurality of demodulator outputs;

remodulating the demodulator outputs that correspond to the predetermined ones of the digitally modulated sub-carrier signals to produce an error signal;

subtracting the error signal from one of the blocks of samples to produce a pre-compensated block of samples; and

combining the pre-compensated block of samples with a plurality of OFDM pulses to produce a compensated composite signal.

2. The method of claim 1, wherein successive ones of the blocks of samples overlap each other.

3. The method of claim 1, wherein the number of samples in the pre-compensated block is equal to the number of samples in an OFDM symbol in the composite digital audio broadcasting signal.

4. The method of claim 1, further comprising the step of zeroing the demodulator outputs that correspond to complementary sub-carriers in the composite digital audio broadcasting signal.

5. The method of claim 1, further comprising the step of:

synchronizing the pre-compensated block of samples with the plurality of OFDM pulses.

6. An apparatus for pre-compensating an analog signal in a composite digital audio broadcasting signal including the analog signal and a plurality of digitally modulated sub-carrier signals, the apparatus comprising:

means for sampling the analog signal to obtain successive blocks of samples, p1 means for demodulating each of the blocks of samples to obtain a plurality of demodulator outputs;

means for remodulating the demodulator outputs that correspond to the predetermined ones of the digitally modulated sub-carrier signals to produce an error signal;

means for subtracting the error signal from one of the blocks of samples to produce a pre-compensated block of samples; and

means for combining the pre-compensated block of samples with a plurality of OFDM pulses to produce a compensated composite signal.

7. The apparatus of claim 6, wherein successive ones of the blocks of samples overlap each other.

8. The apparatus of claim 6, wherein the number of samples in the pre-compensated block is equal to the number of samples in an OFDM symbol in the composite digital audio broadcasting signal.

9. The apparatus of claim 6, further comprising;

means for zeroing the demodulator outputs that correspond to complementary sub-carriers in the composite digital audio broadcasting signal.

10. The apparatus of claim 6, further comprising:

means for synchronizing the pre-compensated block of samples with the plurality of OFDM pulses.

11. An apparatus for pre-compensating an analog signal in a composite digital audio broadcasting signal including the analog signal and a plurality of digitally modulated sub-carrier signals, the apparatus comprising:

a sampler for sampling the analog signal to obtain successive blocks of samples,

a demodulator for demodulating each of the blocks of samples to obtain a plurality of demodulator outputs;

a modulator for remodulating the demodulator outputs that correspond to the predetermined ones of the digitally modulated sub-carrier signals to produce an error signal;

a first combiner for subtracting the error signal from one of the blocks of samples to produce a pre-compensated block of samples; and

a second combiner for combining the pre-compensated block of samples with a plurality of OFDM pulses to produce a compensated composite signal.

12. The apparatus of claim 11, wherein successive ones of the blocks of samples overlap each other.

13. The apparatus of claim 11, wherein the number of samples in the pre-compensated block is equal to the number of samples in an OFDM symbol in the composite digital audio broadcasting signal.

14. The apparatus of claim 11, further comprising;

means for zeroing the demodulator outputs that correspond to complementary sub-carriers in the composite digital audio broadcasting signal.

15. The apparatus of claim 11, further comprising:

means for synchronizing the pre-compensated block of samples with the plurality of OFDM pulses.