Viterbi receiver with improved timing means
AssigneeU.S. Philips Corporation
InventorsJohannes W. M. Bergmans, Ho W. Wong
Life of this patent
Estimating the term…
Abstract
Data receiver in which a received signal is sampled and converted to a digital signal by an analog-to-digital converter (1), the signal samples being detected by a Viterbi detector (3). In order to have the sampling effected at the correct instants, these sampling instants are derived from the received symbol values and an error signal which is a metric for a difference between an expected and a recent signal sample. This is effected by a multiplier 4, a low-pass filter 5 and a control signal for a controllable clock oscillator (6). For utilizing the energy in a precursor of the received signal, an error signal e(k-1) is used which is obtained at a later instant than the instant at which a provisional decision about the relevant data symbol a(k-2) is made.
Claims6
Data receiver comprising deriving means for deriving a detection signal from an input signal, an output of the deriving means being coupled to an input of detection means, said detection means determining a most probable sequence of data symbols on the basis of the detection signal, the symbols occurring in the detection signal with a symbol interval T, by recursively updating candidate sequences (survivors) with associated path metrics derived from branch metrics, the branch metrics being an even function of a difference value e.sub.k, present at a sampling instant kT of the detection signal, and of the detection signal expected for a respective candidate survivor, where k is an integer, characterized in that the receiver comprises timing means for delaying the sampling instants if
- the sign of the difference value e.sub.k-n at a sampling instant (k-n)T, where n is a fixed positive number, and where the difference value is associated to the most probable candidate survivor at the sampling instant kT, and the sign of an estimate f.sub.(k-n-m)T (a.sub.k-n-m) of the contribution of a symbol a.sub.k-n-m (m=1,2,3, . . .), estimated at a sampling instant (k-n-m)T, to the detection signal at an instant (k-n-m)T are equal, the symbol a.sub.k-n-m being taken from the candidate survivor which is the most probable at the sampling instant kT;
- and for advancing the sampling instants
- if the two signs are different.
Dependencies are inferred from the claim text.