Coarse tuning of the channel frequency
AssigneeNokia Mobile Phones Ltd.
InventorAntti Kansakoski
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Abstract
The channel frequency of a digital radiotelephone is coarse tuned utilizing the phase information of the symbols. According to the invention the phase change between the measured phases of one or more received symbols (d) and the previous symbol (e) is detected, the phase change being compared with allowed phase changes. Based on this a decision (g) is made concerning the phase of the transmitted symbol, the phase error (f.sub.err) or difference between the decision (g) and the measured phase change (d) is generated, and on this basis the channel frequency is adjusted.
Claims11
A method for coarse tuning of a channel frequency in a digital radiotelephone receiver, whereby phase information contained in symbols of a differentially encoded, quadrature amplitude modulated (QAM) signal transmitted on the channel is used for the coarse turning, comprising the steps of:
- a) measuring a phase of a received symbol;
- b) generating a signal indicating a phase change between the measured phase of the received symbol and a measured phase of a previously received symbol;
- c) comparing the signal indicating the phase change with predefined allowed phase changes;
- d) deciding, based on the comparison, a transmitted phase of the received symbol;
- e) generating a phase error signal indicting a phase difference between the decided transmitted phase and the measured phase of the received symbol;
- and
- f) adjusting a frequency generator which controls the channel frequency according to the phase error signal.
A carrier tracker, comprising:
- a) symbol receiving means for receiving a transmitted information symbol;
- b) means connected to the symbol receiving means for measuring a phase of the transmitted information symbol;
- c) means connected to the phase measuring means for generating a signal indicating a phase change between a measured phase of the received symbol and a measured phase of a previously received symbol;
- d) means connected to the signal generating means for comparing the generated signal with predetermined phase changes;
- e) means connected to the comparing means for determining a transmitted phase of the received symbol based on an output of the comparing means;
- f) means connected to the determining means for generating a phase error signal indicating a phase difference between an output of the determining means and the measured phase of the received symbol;
- and
- g) a frequency generator connected to and responsive to an output of the phase error signal generator means.
Dependencies are inferred from the claim text.