Method and apparatus for symbol timing recovery
AssigneeThomson Licensing
InventorsPaul Gothard Knutson, Dirk Schmitt, Wen Gao
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Abstract
Methods and apparatus for symbol timing recovery are provided. Both a coarse symbol timing recovery method and apparatus, and a fine symbol timing recovery method and apparatus are described which can be used jointly for symbol recovery, for example in phase shift keying receivers. The coarse method involves the use of differential correlations and finding the time difference in peak values of the correlation results. The fine method involves interpolation of a received digital signal, followed by filtering and timing error detection. The error detection signal is further filtered and used to control the interpolator. The methods provide for robust symbol timing synchronization.
Claims22
A method of symbol timing recovery, comprising:
- performing one or more differential correlation operations on a received signal;
- measuring a time difference between peak values of the correlation function;
- using the time difference as an estimate of symbol timing offset to determine a coarse symbol timing;
- receiving a further digital signal using said coarse symbol timing.
An apparatus for symbol timing recovery, comprising:
- a processing circuit for performing one or more differential correlation operations on a received signal;
- circuitry for measuring a time difference between peak values of the correlation function;
- a timing error detector for determining coarse symbol timing using the time difference as an estimate of symbol timing offset;
- a receiver for receiving a further digital signal using said coarse symbol timing.
A method of improved symbol timing recovery, comprising:
- interpolating a received digital signal, wherein interpolating is controlled by a numerically controlled delay;
- filtering a timing error detection signal with a loop filter;
- controlling the numerically controlled delay using output of said loop filter
- filtering of the interpolated signal using at least one of a matched filter or a second filter, wherein the second filter can also be a matched filter;
- finding a timing error of said filtered interpolated signal as an estimate of fine symbol timing offset to determine symbol timing;
- receiving a further digital signal using said fine symbol timing.
An apparatus for improved symbol timing recovery, comprising:
- an interpolator for interpolating a received digital signal, wherein interpolating is controlled by a numerically controlled delay;
- a loop filter for filtering a time difference signal;
- a controller for controlling the numerically controlled delay using output of said loop filter;
- a filter for filtering of the interpolated signal using at least one of a matched filter or a second filter, wherein the second filter can also be a matched filter;
- a timing error detector for finding the timing error as an estimate of symbol timing offset to determine symbol timing;
- a receiver for receiving a further digital signal using said fine symbol timing.
A method of symbol timing recovery, comprising:
- performing one or more differential correlation operations on a received signal;
- measuring a time difference between peak values of the correlation function;
- using the time difference as an estimate of symbol timing offset to determine a coarse symbol timing;
- using said coarse symbol timing to receive a further digital signal;
- interpolating further received digital signal, wherein interpolating is controlled by a numerically controlled delay;
- filtering a timing error detection signal with a loop filter;
- controlling the numerically controlled delay using output of said loop filter
- filtering of the interpolated output using at least one of a matched filter or a second filter, wherein the second filter can also be a matched filter;
- finding the timing error of the filtered interpolated signal as a further estimate of symbol timing offset to determine a fine symbol timing;
- using said fine symbol timing to receive a subsequent digital signal.
An apparatus for symbol timing recovery, comprising:
- a processing circuit for performing one or more differential correlation operations on a received signal;
- circuitry for measuring a time difference between peak values of the correlation function;
- a first timing error detector for determining coarse symbol timing using the time difference as an estimate of symbol timing offset;
- a receiver for receiving a further digital signal using said coarse symbol timing;
- an interpolator for interpolating said further received digital signal, wherein interpolating is controlled by a numerically controlled delay;
- a loop filter for filtering a time difference signal;
- a controller for controlling the numerically controlled delay using output of said loop filter;
- a filter for filtering the interpolated output using at least one of a matched filter or a second filter, wherein the second filter can also be a matched filter;
- a second timing error detector for calculating the timing error of the filtered interpolated signal as an estimate of symbol timing offset to determine the symbol timing;
- a receiver for receiving a subsequent digital signal using said fine symbol timing.
Dependencies are inferred from the claim text.