EP0772332A2
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EP
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Synchronisation of OFDM signals
Assignee: British Broadcasting Corp
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Filing: 1996-11-04
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Granted: —
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Expires: 2016-11-04
Abstract
Abstract Information is extracted from an OFDM signal, namely a signal which comprises a succession of symbol periods T T each consisting of an active symbol period T S and a guard interval T G . To achieve this an input signal Y is received, and a signal X is provided which is delayed by a delay (10) having a time period equal to the active symbol period T S . The complex product XY* of the input and delayed signals is formed by a full four-component complex multiplier (12) to provide a succession of pulses, one for each symbol period. The complex product signal is filtered using a filter (42; Fig. 4,5 or 6) based on filter elements which provide a delay equal to the total symbol period T T . Symbol timing synchronization information is derived from the filtered complex product signal in a phase-locked loop (44). The argument (phase) of the signal in the pulses is detected by an angle-forming circuit (70;82). The frequency of a local oscillator (78) is controlled in dependence upon the argument of the signal in the pulses. To reduce continuous wave (CW) interference, any constant complex component of the signal XY* is removed, such as by using an integrate-and-dump circuit (80), or by extracting the complex mean by low-pass filtering the XY* signal and subtracting the mean from the XY* signal itself.
Inventors
- 👤 Jonathan Highton c/o British Broadc. Corp. Stott
- 👤 Christopher K P c/o British Broadc. Corp. Clarke
- 👤 Adrian Paul c/o British Broadc. Corp. Robinson
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 09:00
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/26; H04L27/2601; H04L27/2647; H04L27/2655; H04L27/2662; H04L27/2665; H04L27/2656; H04L27/2657; H04L27/266
Claims Analysis
Total Claims: 36
Claim 1
Independent Claim
102 words
A method of extracting information from a signal which comprises a succession of symbol periods T T each consisting of an active symbol period T S and a guard interval T G , the method comprising the steps of: receiving an input signal Y (or X); providing a signal X (or Y) delayed by a time period equal to the active symbol period T S ; forming a signal related to the complex product XY* of the input and delayed signals to provide a succession of pulses, one for each symbol period; and detecting the argument of the signal in the pulses.
Claim 2
Dependent Claim
35 words
A method according to claim 1, including, after the forming step, filtering the complex product signal with a filter based on filter elements having a delay equal to the total symbol period T T .
Claim 3
Dependent Claim
25 words
A method according to claim 2, including the step of controlling the frequency of a local oscillator in dependence upon the filtered complex product signal.
Claim 4
Dependent Claim
53 words
A method according to claim 1, in which the complex product signal is formed as X Q Y* + XY Q *, where X Q ,Y Q have the possible values 1+j, 1-j, -1+j, -1-j, and are formed by replacing each Cartesian component of X and Y, by its sign multiplied by unity.
Claim 5
Dependent Claim
24 words
A method according to claim 1, in which the step of detecting the arguments comprises detecting the sense of the phase deviation from zero.
Claim 6
Dependent Claim
29 words
A method according to claim 5, including the step of controlling the frequency of a local oscillator in dependence upon the detected argument of the signal in the pulses.
Claim 7
Dependent Claim
21 words
A method according to claim 1, including the step of controlling the symbol timing in dependence on the complex product signal.
Claim 8
Dependent Claim
27 words
A method according to claim 1, including the step of integrating the signal, with sucessive portions of the signal being integrated in alternating positive and negative sense.
Claim 9
Independent Claim
117 words
A method of extracting information from a signal which comprises a succession of symbol periods T T each consisting of an active symbol period T S and a guard interval T G , the method comprising the steps of: receiving an input signal Y (or X); providing a signal X (or Y) delayed by a time period equal to the active symbol period T S ; forming a signal related to the complex product XY* of the input and delayed signals to provide a succession of pulses, one for each symbol period; and filtering the complex product signal with a filter based on filter elements having a delay equal to the total symbol period T T .
Claim 10
Dependent Claim
25 words
A method according to claim 9, including the step of controlling the frequency of a local oscillator in dependence upon the filtered complex product signal.
Claim 11
Dependent Claim
26 words
A method according to claim 10, including the step of controlling a local oscillator in dependence upon the detected argument of the signal in the pulses.
Claim 12
Dependent Claim
21 words
A method according to claim 9, including the step of controlling the symbol timing in dependence on the complex product signal.
Claim 13
Independent Claim
103 words
A method of extracting information from a signal which comprises a succession of symbol periods T T each consisting of an active symbol period T S and a guard interval T G , the method comprising the steps of: receiving an input signal Y (or X); providing a signal X (or Y) delayed by a time period equal to the active symbol period T S ; forming a signal related to the complex product XY* of the input and delayed signals to provide a succession of pulses, one for each symbol period; and substantially removing any constant complex component of the XY* signal.
Claim 14
Dependent Claim
34 words
A method according to claim 13, in which the step of removing any constant complex component comprises integrating the signal, with sucessive portions of the signal being integrated in alternating positive and negative sense.
Claim 15
Dependent Claim
32 words
A method according to claim 13, in which the step of removing any constant complex component comprises low-pass filtering the XY* signal to extract the mean and subtracting it from the signal.
Claim 16
Dependent Claim
18 words
A method according to claim 13, in which the complex product is formed by a full four-component multiplier.
Claim 17
Independent Claim
138 words
A method of extracting information from a signal which comprises a succession of symbol periods T T each consisting of an active symbol period T S and a guard interval T G , the method comprising the steps of: receiving an input signal Y (or X); providing a signal X (or Y) delayed by a time period equal to the active symbol period T S ; and forming a signal related to the complex product XY* of the input and delayed signals to provide a succession of pulses, one for each symbol period, the complex product signal being formed as X Q Y* + XY Q *, where X Q ,Y Q have the possible values 1+j, 1-j, -1+j, -1-j, and are formed by replacing each Cartesian component of X and Y, by its sign multiplied by unity.
Claim 18
Independent Claim
100 words
A method of extracting information from a signal which comprises a succession of symbol periods T T each consisting of an active symbol period T S and a guard interval T G , the method comprising the steps of: receiving an input signal Y (or X); providing a signal X (or Y) delayed by a time period equal to the active symbol period T S ; and forming a complex product signal XY* from the input and delayed signals to provide a succession of pulses, one for each symbol period, the complex product being formed by a full four-component multiplier.
Claim 19
Dependent Claim
106 words
Apparatus for extracting information from a signal which comprises a succession of symbol periods T T each consisting of an active symbol period T S and a guard interval T G , the apparatus comprising: means for receiving an input signal Y (or X); means for providing a signal X (or Y) delayed by a time period equal to the active symbol period T S ; means for forming a signal related to the complex product XY* of the input and delayed signals to provide a succession of pulses, one for each symbol period; and means for detecting the argument of the signal in the pulses.
Claim 20
Dependent Claim
37 words
Apparatus according to claim 19, including, after the means for forming, means for filtering the complex product signal with a filter based on filter elements having a delay equal to the total symbol period T T .
Claim 21
Dependent Claim
23 words
Apparatus according to claim 20, including means for controlling the frequency of a local oscillator in dependence upon the filtered complex product signal.
Claim 22
Dependent Claim
52 words
Apparatus according to claim 19, in which the complex product signal is formed as X Q Y* + XY Q *, where X Q ,Y Q have the possible values 1+j, 1-j, -1+j, -1-j, and are formed by replacing each Cartesian component of X and Y, by its sign multiplied by unity.
Claim 23
Dependent Claim
25 words
Apparatus according to claim 19, in which the means for detecting the arguments comprises means for detecting the sense of the phase deviation from zero.
Claim 24
Dependent Claim
24 words
Apparatus according to claim 23, including means for controlling a local oscillator in dependence upon the detected argument of the signal in the pulses.
Claim 25
Dependent Claim
19 words
Apparatus according to claim 19, including means for controlling the symbol timing in dependence on the complex product signal.
Claim 26
Dependent Claim
26 words
A method according to claim 19, including means for integrating the signal, with sucessive portions of the signal being integrated in alternating positive and negative sense.
Claim 27
Dependent Claim
121 words
Apparatus for extracting information from a signal which comprises a succession of symbol periods T T each consisting of an active symbol period T S and a guard interval T G , the apparatus comprising: means for receiving an input signal Y (or X); means for providing a signal X (or Y) delayed by a time period equal to the active symbol period T S ; means for forming a signal related to the complex product XY* of the input and delayed signals to provide a succession of pulses, one for each symbol period; and means for filtering the complex product signal with a filter based on filter elements having a delay equal to the total symbol period T T .
Claim 28
Dependent Claim
23 words
Apparatus according to claim 27, including means for controlling the frequency of a local oscillator in dependence upon the filtered complex product signal.
Claim 29
Dependent Claim
24 words
Apparatus according to claim 28, including means for controlling a local oscillator in dependence upon the detected argument of the signal in the pulses.
Claim 30
Dependent Claim
19 words
Apparatus according to claim 27, including means for controlling the symbol timing in dependence on the complex product signal.
Claim 31
Dependent Claim
108 words
Apparatus for extracting information from a signal which comprises a succession of symbol periods T T each consisting of an active symbol period T S and a guard interval T G , the apparatus comprising: means for receiving an input signal Y (or X) ; means for providing a signal X (or Y) delayed by a time period equal to the active symbol period T S ; means for forming a signal related to the complex product XY* of the input and delayed signals to provide a succession of pulses, one for each symbol period; and means for substantially removing any constant complex component of the XY* signal.
Claim 32
Dependent Claim
35 words
Apparatus according to claim 31, in which the means for removing any constant complex component comprises means for integrating the signal, with sucessive portions of the signal being integrated in alternating positive and negative sense.
Claim 33
Dependent Claim
33 words
Apparatus according to claim 31, in which the means for removing any constant complex component comprises means for low-pass filtering the XY* signal to extract the mean and subtracting it from the signal.
Claim 34
Dependent Claim
17 words
Apparatus according to claim 31, in which the complex product is formed by a full four-component multiplier.
Claim 35
Dependent Claim
140 words
Apparatus for extracting information from a signal which comprises a succession of symbol periods T T each consisting of an active symbol period T S and a guard interval T G , the apparatus comprising: means for receiving an input signal Y (or X); means for providing a signal X (or Y) delayed by a time period equal to the active symbol period T S ; and means for forming a signal related to the complex product XY* of the input and delayed signals to provide a succession of pulses, one for each symbol period, the complex product signal being formed as X Q Y* + XY Q *, where X Q ,Y Q have the possible values 1+j, 1-j, -1+j, -1-j, and are formed by replacing each Cartesian component of X and Y, by its sign multiplied by unity.
Claim 36
Dependent Claim
131 words
Apparatus for extracting information from a signal which comprises a succession of symbol periods T T each consisting of an active symbol period T S and a guard interval T G , the apparatus comprising: means for receiving an input signal Y (or X) ; means for providing a signal X (or Y) delayed by a time period equal to the active symbol period T S ; means for forming a signal related to the complex product XY* of the input and delayed signals to provide a succession of pulses, one for each symbol period; and means for forming a complex product signal XY* from the input and delayed signals to provide a succession of pulses, one for each symbol period, the complex product being formed by a full four-component multiplier.
References Cited (Backward Citations)
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