Method and apparatus for symbol synchronization in multi-level digital FM radio
First Claim
1. A method for deriving a first symbol clock associated with a first received multilevel FM radio signal burst of symbols using samples of the burst itself, comprising the steps of:
- capturing said first received multilevel FM radio signal burst to produce burst samples;
squaring said burst samples to produce squared burst samples;
differentiating said squared burst samples;
cyclically accumulating said differentiated squared burst samples to produce accumulated samples;
identifying a zero crossing in said accumulated samples; and
deriving said symbol clock from said zero crossing.
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Abstract
A block demodulation method and apparatus that provides for synchronizing bursts of incoming data without a special symbol synchronization word, and minimal frame synchronization overhead. An entire burst, comprising ramp up time, a preamble, guard times, data and ramp down time, is captured and stored in the form of baseband samples of the signal burst. The burst samples are then filtered to reduce pattern jitter. Thereafter, the samples are squared to derive the symbol clock. Then, the samples are differenced and cyclically accumulated. The cyclicly accumulated samples are examined to find a valid zero crossing. In the event that the aforementioned method does not identify a valid zero crossing, two additional methods for finding a valid zero crossing are employed.
75 Citations
22 Claims
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1. A method for deriving a first symbol clock associated with a first received multilevel FM radio signal burst of symbols using samples of the burst itself, comprising the steps of:
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capturing said first received multilevel FM radio signal burst to produce burst samples; squaring said burst samples to produce squared burst samples; differentiating said squared burst samples; cyclically accumulating said differentiated squared burst samples to produce accumulated samples; identifying a zero crossing in said accumulated samples; and deriving said symbol clock from said zero crossing. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for deriving a symbol clock associated with a first received multilevel FM radio signal burst of symbols using samples of the burst itself, comprising the steps of:
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capturing said first received multilevel FM radio signal burst to produce burst samples; forming a histogram from said burst samples, said histogram having a selected number of counter increments; cyclically accumulating said counter increments for said first received multilevel FM radio signal burst; determining the point in said histogram having the maximum value; and deriving said symbol clock from said point. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. A method for deriving a symbol clock associated with a first received multilevel FM radio signal burst of symbols using samples of the burst itself, comprising the steps of:
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capturing said first received multilevel FM radio signal burst to produce an original set of burst samples; constructing a new set of samples by differencing said original set of burst samples one symbol apart; forming a histogram from said new set of burst samples, said histogram having a selected number of counter increments; cyclically accumulating said counter increments for said first received multilevel FM radio signal burst; determining the point in the histogram having the maximum value; and deriving said symbol clock from said point. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22)
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Specification