EP0308150A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method of communicating digital signals and receiver for use with such method
Assignee: British Telecommunications PLC
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Filing: 1988-09-09
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Granted: —
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Expires: 2008-09-09
Abstract
Abstract A receiver (2) for selectively extracting one of two or more time division multiplexed channels of digital signals, which channel has been scrambled before multiplexing using a predetermined digital sequence comprising - a clock means (4) arranged to provide clock pulses having a repetition rate dependent on a clock control signal; a digital sequence generator (10) triggered by each clock pulse to provide a generator signal representative of the next digit in the predetermined digital sequence; a sampling means (8) arranged to provide a sampled signal the clock pulse rate; and a phase lock means (8, 18, 25, 26, 22, 4, 10) controlling the clock control signal whereby the generator sequence is delay - lockable to the sampled signal. The receiver finds particular application with the reception of digital video signals broadcast through a passive optical network.
Inventors
- 👤 David Wynford Faulkner
- 👤 Dianne Margaret Russ
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 06:26
CPC Classifications
H; H04; H04J; H04J3/00; H04J3/02; H04J3/08
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
116 words
A receiver for selectively extracting one of two or more time division multiplexed channels of digital signals, which channel has been scrambled before forming the multiplexed signal using a predetermined digital sequence comprising- a clock means arranged to provide clock pulses having a repetition rate dependent on a clock control signal; a digital sequence generator means for providing a generator signal representative of the next digit in the predetermined digital sequence at the clock repetition rate; a sampling means arranged to provide a sample signal which is the multiplexed signal sampled at the clock pulse rate; and a phase lock means controlling the clock control signal whereby the generator sequence is phase-lockable to the sampled signal.
Claim 2
Dependent Claim
116 words
A receiver for selectively extracting one of two or more time division multiplexed channels of digital signals, which channel has been scrambled before forming the multiplexed signal using a predetermined digital sequence comprising- a clock means arranged to provide clock pulses having a repetition rate dependent on a clock control signal; a digital sequence generator means for providing a generator signal representative of the next digit in the predetermined digital sequence at the clock repetition rate; a sampling means arranged to provide a sample signal which is the multiplexed signal sampled at the clock pulse rate; and a phase lock means controlling the clock control signal whereby the generator sequence is phase-lockable to the sampled signal.
Claim 3
Dependent Claim
73 words
A receiver as claimed in claim 1 in which the phase lock means comprises a comparison means providing an output signal representative of the XOR of the generator signal and the sampled signal, a signal detector coupled to receive the XOR output signal and an averaging means arranged to provide the clock control signal such that the clock control signal is representative of the time - averaged d.c. component of the detected signal.
Claim 4
Dependent Claim
17 words
A receiver as claimed in claim 2 in which the signal detector is a logical zero detector.
Claim 5
Dependent Claim
29 words
A receiver as claimed in any one of claims 2 or 3 in which the phase lock means is lockable to the line blanking interval of a video channel.
Claim 6
Dependent Claim
40 words
A receiver as claimed in any preceding claim including a further sampling means arranged to provide a sample signal which is the multiplexed signal sampled at the clock pulse rate at times delayed with respect to the other sampling means.
Claim 7
Dependent Claim
20 words
A receiver as claimed in any preceding claim in which the digital sequence is provided by a pseudo-random sequence generator.
Claim 8
Dependent Claim
14 words
A receiver as claimed in claim 6 in which the descrambler is self synchronising.
Claim 9
Dependent Claim
27 words
A receiver as claimed in either of claims 6 and 7 in which the setting means is controllable by the received multiplexed signal before or after descrambling.
Claim 10
Dependent Claim
32 words
A receiver as claimed in any one of claims 6 and 8 including a setting means whereby the characteristic function of the PRSG can be set by the operator of the receiver.
Claim 11
Dependent Claim
30 words
A receiver as claimed in any preceding claim including means for deactivating the phase locking means thereby causing the generator output to phase slip relative to the multiplexed input signal.
Claim 12
Dependent Claim
33 words
A receiver as claimed in any preceding claim including a transparent channel sampler driven by a further clock signal which is time delayed from the from the clock pulses from the clock means.
Claim 13
Independent Claim
49 words
A method of communication in which a transmitter transmits two or more time division multiplexed digital signals, one or more of which has been scrambled using a predetermined digital sequence, and selectively extracting the scrambled signal by means of a receiver according to any one of the preceding claims.
Claim 14
Independent Claim
42 words
A method of transmitting a digital signal in which the digital signal is scrambled using a predetermined digital sequence, and time division multiplexing with one or more other digital signals and transmitting the multiplexed signals are transmitted to one or more receivers.
Claim 15
Independent Claim
42 words
A method of transmitting a digital signal in which the digital signal is scrambled using a predetermined digital sequence, and time division multiplexing with one or more other digital signals and transmitting the multiplexed signals are transmitted to one or more receivers.
Claim 16
Dependent Claim
6 words
A receiver substantially as hereinbefore described.
Claim 17
Dependent Claim
6 words
A receiver substantially as hereinbefore described.
Claim 18
Independent Claim
8 words
A method of communication substantially as hereinbefore described.
Claim 19
Independent Claim
8 words
A method of communication substantially as hereinbefore described.
Claim 20
Independent Claim
9 words
A method of transmissing signals substantially as hereinbefore described.
Claim 21
Independent Claim
9 words
A method of transmissing signals substantially as hereinbefore described.
References Cited (Backward Citations)
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