Broadcast encoding system and method
First Claim
1. A method for adding a binary code bit to a block of a signal varying within a predetermined signal bandwidth, the method comprising the following steps:
- a) selecting a reference frequency within the predetermined signal bandwidth, and associating therewith both a first code frequency having a first predetermined offset from the reference frequency and a second code frequency having a second predetermined offset from the reference frequency;
b) measuring the spectral power of the signal within the block in a first neighborhood of frequencies extending about the first code frequency and in a second neighborhood of frequencies extending about the second code frequency;
c) increasing the spectral power at the first code frequency so as to render the spectral power at the first code frequency a maximum in the first neighborhood of frequencies; and
, d) decreasing the spectral power at the second code frequency so as to render the spectral power at the second code frequency a minimum in the second neighborhood of frequencies.
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Accused Products
Abstract
An encoder is arranged to add a binary code bit to block of a signal by selecting, within the block, (i) a reference frequency within the predetermined signal bandwidth, (ii) a first code frequency having a first predetermined offset from the reference frequency, and (iii) a second code frequency having a second predetermined offset from the reference frequency. The spectral amplitude of the signal at the first code frequency is increased so as to render the spectral amplitude at the first code frequency a maximum in its neighborhood of frequencies and is decreased at the second code frequency so as to render the spectral amplitude at the second code frequency a minimum in its neighborhood of frequencies. Alternatively, the portion of the signal at one of the first and second code frequencies whose spectral amplitude is smaller may be designated as a modifiable signal component such that, in order to indicate the binary bit, the phase of the modifiable signal component is changed so that this phase differs within a predetermined amount from the phase of the reference signal component. As a still further alternative, the spectral amplitude of the first code frequency may be swapped with a spectral amplitude of a frequency having a maximum amplitude in the first neighborhood of frequencies and the spectral amplitude of the second code frequency may be swapped with a spectral amplitude of a frequency having a minimum amplitude in the second neighborhood of frequencies. A decoder may be arranged to decode the binary bit.
409 Citations
39 Claims
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1. A method for adding a binary code bit to a block of a signal varying within a predetermined signal bandwidth, the method comprising the following steps:
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a) selecting a reference frequency within the predetermined signal bandwidth, and associating therewith both a first code frequency having a first predetermined offset from the reference frequency and a second code frequency having a second predetermined offset from the reference frequency;
b) measuring the spectral power of the signal within the block in a first neighborhood of frequencies extending about the first code frequency and in a second neighborhood of frequencies extending about the second code frequency;
c) increasing the spectral power at the first code frequency so as to render the spectral power at the first code frequency a maximum in the first neighborhood of frequencies; and
,d) decreasing the spectral power at the second code frequency so as to render the spectral power at the second code frequency a minimum in the second neighborhood of frequencies. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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4. The method of claim 1 wherein the reference frequency is selected in step a) according to the following steps:
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a1) finding, within a predetermined portion of the bandwidth, a frequency at which the signal has a maximum spectral power; and
,a2) adding a predetermined frequency shift to that frequency of maximum spectral power.
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5. The method of claim 4 wherein the signal is an audio signal, wherein the predetermined portion of the bandwidth comprises a lower portion of the bandwidth extending from the lowest frequency by 2 kHz, and wherein the predetermined shift frequency is substantially equal to 5.
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6. The method of claim 1 wherein the first and second code frequencies are selected according to the following equations:
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7. The method of claim 1 wherein a synchronization block is added to the signal, and wherein the synchronization block is characterized by a triple tone portion.
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8. The method of claim 1 wherein the signal has a spectral power which is a maximum in neighborhoods of the reference frequency, of the first code frequency, and of the second code frequency.
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9. The method of claim 8 wherein a synchronization block is added to the signal, and wherein the synchronization block is characterized by a triple tone portion.
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10. The method of claim 1 wherein the first and the second predetermined offsets have equal magnitudes but opposite signs.
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11. The method of claim 1 wherein the first code frequency is greater than the reference frequency, and wherein the second code frequency is less than the reference frequency.
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12. The method of claim 1 wherein the second code frequency is greater than the reference frequency, and wherein the first code frequency is less than the reference frequency.
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13. The method of claim 1 wherein a plurality of binary code bits are added to the signal by repeating steps a)-d) a number of times.
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14. A method for adding a binary code bit to a block of a signal having a spectral amplitude and a phase, both the spectral amplitude and the phase varying within a predetermined signal bandwidth, the method comprising the following steps:
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a) selecting, within the block, (i) a reference frequency within the predetermined signal bandwidth, (ii) a first code frequency having a first predetermined offset from the reference frequency, and (iii) a second code frequency having a second predetermined offset from the reference frequency;
b) comparing the spectral amplitude of the signal near the first code frequency to the spectral amplitude of the signal near the second code frequency;
c) selecting a portion of the signal at one of the first and second code frequencies at which the corresponding spectral amplitude is smaller to be a modifiable signal component, and selecting a portion of the signal at the other of the first and second code frequencies to be a reference signal component; and
,d) selectively changing the phase of the modifiable signal component so that it differs by no more than a predetermined amount from the phase of the reference signal component. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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17. The method of claim 14 wherein the reference frequency is selected in step a) according to the following steps:
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a1) finding, within a predetermined portion of the bandwidth, a frequency at which the signal has a maximum spectral amplitude; and
,a2) adding a predetermined frequency shift to that frequency of maximum spectral amplitude.
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18. The method of claim 17 wherein the signal is an audio signal, wherein the predetermined portion of the bandwidth comprises a lower portion of the bandwidth extending from the lowest frequency by 2 kHz, and wherein the predetermined shift frequency is substantially equal to 5.
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19. The method of claim 14 wherein the first and second code frequencies are selected according to the following equations:
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20. The method of claim 14 wherein a synchronization block is added to the signal, and wherein the synchronization block is characterized by a triple tone portion.
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21. The method of claim 14 wherein the signal has an spectral amplitude which is a maximum in neighborhoods of the reference frequency, of the first code frequency, and of the second code frequency.
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22. The method of claim 21 wherein a synchronization block is added to the signal, and wherein the synchronization block is characterized by a triple tone portion.
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23. The method of claim 14 wherein the first and the second predetermined offsets have equal magnitudes but opposite signs.
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24. The method of claim 14 wherein the first code frequency is greater than the reference frequency, and wherein the second code frequency is less than the reference frequency.
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25. The method of claim 14 wherein the second code frequency is greater than the reference frequency, and wherein the first code frequency is less than the reference frequency.
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26. The method of claim 14 wherein a plurality of binary code bits are added to the signal by repeating steps a)-d) a number of times.
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27. A method of reading a digitally encoded message transmitted with a signal having a time-varying intensity, the signal characterized by a signal bandwidth, the digitally encoded message comprising a plurality of binary bits, the method comprising the following steps:
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a) selecting a reference frequency within the signal bandwidth;
b) selecting a first code frequency at a first predetermined frequency offset from the reference frequency and selecting a second code frequency at a second predetermined frequency offset from the reference frequency; and
,c) finding which one of the first and second code frequencies has a spectral amplitude associated therewith that is a maximum within a corresponding frequency neighborhood and finding which one of the first and second code frequencies has a spectral amplitude associated therewith that is a minimum within a corresponding frequency neighborhood in order to thereby determine a value of a received one of the binary bits. - View Dependent Claims (28, 29, 30, 31, 32)
finding, within a predetermined portion of the bandwidth, the frequency at which the spectral amplitude of the signal is a maximum; and
,adding a predetermined frequency shift to that frequency of maximum spectral amplitude.
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31. The method of claim 30 wherein the signal is an audio signal, wherein the predetermined portion of the bandwidth comprises a lower portion of the bandwidth extending from the lowest frequency thereof to 2 kHz thereabove, and wherein the predetermined shift frequency is substantially equal to 5.
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32. The method of claim 27 wherein the first and the second predetermined frequency offsets have equal magnitudes but opposite signs.
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33. A method of reading a digitally encoded message transmitted with a signal having a spectral amplitude and a phase, the signal characterized by a signal bandwidth, the message comprising a plurality of binary bits, the method comprising the steps of:
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a) selecting a reference frequency within the signal bandwidth;
b) selecting a first code frequency at a first predetermined frequency offset from the reference frequency and selecting a second code frequency at a second predetermined frequency offset from the reference frequency;
c) determining the phase of the signal within respective predetermined frequency neighborhoods of the first and the second code frequencies; and
,d) determining if the phase at the first code frequency is within a predetermined value of the phase at the second code frequency and thereby determining a value of a received one of the binary bits. - View Dependent Claims (34, 35, 36, 37, 38)
finding, within a predetermined portion of the bandwidth, the frequency at which the spectral amplitude of the signal is a maximum; and
,adding a predetermined frequency shift to the frequency at which the spectral amplitude of the signal is a maximum.
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37. The method of claim 36 wherein the signal is an audio signal, wherein the predetermined portion of the bandwidth comprises a lower portion of the bandwidth extending from the lowest frequency thereof to 2 kHz thereabove, and wherein the predetermined shift frequency is substantially equal to 5.
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38. The method of claim 33 wherein the first and the second predetermined frequency offsets have equal magnitudes but opposite signs.
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39. A method for adding a binary code bit to a block of a signal varying within a predetermined signal bandwidth, the method comprising the following steps:
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a) selecting a reference frequency within the predetermined signal bandwidth, and associating therewith both a first code frequency having a first predetermined offset from the reference frequency and a second code frequency having a second predetermined offset from the reference frequency;
b) measuring the spectral power of the signal within the block in a first neighborhood of frequencies extending about the first code frequency and in a second neighborhood of frequencies extending about the second code frequency, wherein the first frequency has a spectral amplitude, and wherein the second frequency has a spectral amplitude;
c) swapping the spectral amplitude of the first code frequency with a spectral amplitude of a frequency having a maximum amplitude in the first neighborhood of frequencies while retaining a phase angle at both the first frequency and the frequency having the maximum amplitude in the first neighborhood of frequencies; and
,d) swapping the spectral amplitude of the second code frequency with a spectral amplitude of a frequency having a minimum amplitude in the second neighborhood of frequencies while retaining a phase angle at both the second frequency and the frequency having the maximum amplitude in the second neighborhood of frequencies.
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Specification