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Patent US3786358A successfully refreshed from Google Patents.
US3786358A
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Method and apparatus for detecting the beginning of data block
Assignee: International Business Machines Corp
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Filing: 1972-12-27
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Granted: 1974-01-15
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Expires: 1992-12-27
Abstract
Abstract The base frequency of digital data signal is detected by using the transitions in the digital signal to control the duration of ramp signals generated by ramp generators. One ramp is restarted by each positive transition while a second ramp is restarted by each negative transition. Comparators monitor each ramp and compare the ramp against a threshold level. The threshold is set so that the comparator will change its state of output at a time period T 1/2 f where f is the base frequency of the expected data signal. The outputs from the two comparators are exclusiveOR''d to produce a signal whose duration is a measure of the frequency departure of the input data signal from the expected data frequency. The output of the exclusive-OR is integrated to obtain an average DC voltage level which is a measure of the frequency of the input data signal. This average DC level varies linearly with the departure of the input data frequency from the expected data frequency. The output of the integrator is compared against a threshold by a comparator. This comparator generates an output signal indicating when the frequency of the input data signal is approaching the expected data frequency, i.e., the condition of beginning of record or beginning of data block. The threshold used by this last comparator may be adjusted to change the selectivity or bandwidth of frequencies that will result in the apparatus detecting the beginning of a data record.
Inventors
- 👤 B Fiorino
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 12:57
CPC Classifications
H; H04; H04L; H04L1/00; H04L1/0078; H04L1/0083; H03; H03K; H03K5/00; H03K5/153
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
74 words
Apparatus for identifying the presence of an expected digital signal on a digital signal input line comprising: means for digitally detecting continuously over a frequency range the frequency deviation of the base frequency of the input digital signal from the base frequency of the expected digital signal; means for measuring the deviation against an acceptable tolerance range and indicating the presence of the expected signal if the deviation is within the acceptable tolerance range.
Claim 2
Dependent Claim
74 words
Apparatus for identifying the presence of an expected digital signal on a digital signal input line comprising: means for digitally detecting continuously over a frequency range the frequency deviation of the base frequency of the input digital signal from the base frequency of the expected digital signal; means for measuring the deviation against an acceptable tolerance range and indicating the presence of the expected signal if the deviation is within the acceptable tolerance range.
Claim 3
Dependent Claim
49 words
The apparatus of claim 1 wherein said detecting means comprises: means for comparing the period of the digital signal being received and the period of the expected digital signal and generating a time difference signal whereby the time difference corresponds to a period deviation and thus a frequency deviation.
Claim 4
Dependent Claim
125 words
The apparatus of claim 1 wherein said detecting means comprises: means for generating a ramp signal where each ramp is initiated by the periodic transitions in the digital signal; means for sensing when the ramp signal crosses a threshold whereby the time from ramp-initiated until ramp-crosses-threshold corresponds to a first period related to the frequency of the expected digital signal, and the time from ramp-crosses-threshold until ramp-initiated corresponds to a second period related to the frequency of the received digital signal; means responsive to said sensing means for generating a pulse waveform where the duration of the pulses corresponds to deviation of said second period from said first period and thereby to the frequency deviation of the received digital signal from the expected digital signal.
Claim 5
Dependent Claim
43 words
The apparatus of claim 3 and in addition: means for adjusting the slope of the ramp generated by said generating means so that said first period related to the frequency of the expected digital signal may be adjusted to change the expected frequency.
Claim 6
Dependent Claim
114 words
Apparatus for detecting the beginning of a data block in a received digital signal comprising: means for comparing the duration of digital signal cycles against a period corresponding to the frequency expected in a data block; logic means responsive to said comparing means for generating a pulse waveform where the pulse duration is indicative of frequency deviation of the received digital signal from the expected data block frequency; means responsive to said logic means for measuring the duration of pulses in the pulse waveform over a predetermined length of the pulse waveform to thereby detect the frequency deviation over a predetermined time and indicate beginning of data block if the frequency deviation is acceptable.
Claim 7
Dependent Claim
114 words
Apparatus for detecting the beginning of a data block in a received digital signal comprising: means for comparing the duration of digital signal cycles against a period corresponding to the frequency expected in a data block; logic means responsive to said comparing means for generating a pulse waveform where the pulse duration is indicative of frequency deviation of the received digital signal from the expected data block frequency; means responsive to said logic means for measuring the duration of pulses in the pulse waveform over a predetermined length of the pulse waveform to thereby detect the frequency deviation over a predetermined time and indicate beginning of data block if the frequency deviation is acceptable.
Claim 8
Dependent Claim
44 words
Apparatus of claim 5 wherein said comparing means comprises: means for indicating the duration of digital signal cycles as compared to said period and generating a comparison signal indicative of both the frequency of expected data block and the frequency of received digital signal.
Claim 9
Dependent Claim
45 words
Apparatus of claim 6 wherein said logic means comprises: means responsive to said comparison signal for logically determining the difference between the frequency of expected data block and the frequency of received digital signal and producing pulses whose duration is indicative of the frequency deviation.
Claim 10
Dependent Claim
26 words
ApparAtus of claim 6 and in addition: means for adjusting said indicating means so that the frequency expected can be adjusted for different data block signals.
Claim 11
Dependent Claim
52 words
The apparatus of claim 5 wherein said measuring means comprises: means for determining the average duration of pulses in said pulse waveform over said predetermined length of the pulse waveform; means for comparing the average duration against a threshold duration and indicating beginning of data block when the threshold duration is satisfied.
Claim 12
Dependent Claim
30 words
The apparatus of claim 9 and in addition: means for adjusting said threshold duration to thereby change the amount of frequency deviation acceptable when detecting the beginning of data block.
Claim 13
Dependent Claim
69 words
Method for detecting the presence of an expected frequency in a digital signal comprising: comparing the base frequency of the digital signal against the expected frequency and indicating the frequency deviation over a continuous frequency bandwidth; comparing the frequency deviation against a predetermined bandwidth about the expected frequency and indicating presence of expected frequency if frequency deviation indicates the frequency of the digital signal is within the predetermined bandwidth.
Claim 14
Dependent Claim
69 words
Method for detecting the presence of an expected frequency in a digital signal comprising: comparing the base frequency of the digital signal against the expected frequency and indicating the frequency deviation over a continuous frequency bandwidth; comparing the frequency deviation against a predetermined bandwidth about the expected frequency and indicating presence of expected frequency if frequency deviation indicates the frequency of the digital signal is within the predetermined bandwidth.
Claim 15
Dependent Claim
33 words
Method of claim 11 and in addition: adjusting the bandwidth in the second comparing step so that the selectivity of the method in detecting the presence of an expected frequency may be varied.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-01-14 | 1977-07-16 | 1978-01-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-14 | 1981-07-16 | 1982-01-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-14 | 1985-07-16 | 1986-01-15 | $7700.00 | Window Closed / Lapsed |