Synchronizing position detecting circuit

1. A synchronizing position detecting circuit for use in a receiver at a mobile station in a mobile communication system, comprising:

a window size determining circuit which calculates a moved distance in which the mobile station has moved from a first location to a second location during a sleep time based on a moving speed of the mobile station and a duration of the sleep time, the window size determining circuit selecting a window size corresponding to the moved distance for ascertaining a phase change of a received signal that includes a code;

a synchronizing code generating circuit which repeatedly generates a synchronizing code with at least part of the code of the received signal, the synchronizing code generating circuit successively shifting a phase of the synchronizing code by a predetermined phase width so as to provide a plurality of candidate signals with phases lying within the window;

a correlation circuit for calculating a correlation function between the candidate signals and the received signal; and

a synchronizing position determining circuit that determines which candidate signal has a maximum correlation value with the received signal.

2. A synchronizing position detecting circuit according to claim 1 , wherein when the synchronizing position determining circuit has determined which candidate signal has a maximum correlation value with the received signal, the synchronizing code generating circuit synchronizes a phase of the synchronizing code with a phase of the received signal based on the candidate signal having a maximum correlation value.

3. A synchronizing position detecting circuit according to claim 1 , wherein the window size determining circuit selects a window size from a plurality of predetermined window sizes.

4. A synchronizing position detecting circuit according to claim 1 , wherein the window size determining circuit selects a window size based on a phase change of the received signal corresponding to the moved distance and a phase change of the synchronizing code.

5. A synchronizing position detecting circuit according to claim 4 , wherein the phase change of the synchronizing code is caused during one sleep time due to an error of the synchronizing code generating circuit.

6. A synchronizing position detecting circuit according to claim 1 , wherein the synchronizing position determining circuit judges that the received signal is detected when the correlation function calculated by the correlation circuit exceeds a threshold value.

7. A synchronizing position detecting circuit for use at a receiver in a mobile station in a mobile communication system, comprising:

a distance estimating circuit which calculates a distance between a first distance and a second distance as an estimated distance, the first distance being defined by a distance between a location where a base station is located and a location where the mobile station is located before a sleep time of the mobile station and the second distance being defined by a distance between the location where the base station is located and a location where the mobile station is located after the sleep time;

a window size determining circuit which selects a window size, the window size being selected to accommodate a phase change of a received signal from the base station corresponding to the estimated moved distance, the received signal including a code;

a synchronizing code generating circuit which repeatedly generates a synchronizing code that coincides with at least part of the code of the received signal, the synchronizing code generating circuit successively shifting a phase of the synchronizing code by a predetermined phase width so as to produce a plurality of a candidate signals with phases laying within the window;

a correlation circuit which calculates a correlation function between the code candidate signals and the received signal; and

a synchronizing position determining circuit that determines which candidate signal has a maximum correlation value with the received signal.

8. A synchronizing position detecting circuit according to claim 7 , wherein when the synchronizing position determining circuit has determined which candidate signal has a maximum correlation value with the received signal, the synchronizing code generating circuit synchronizes a phase of the synchronizing code with a phase of the received signal based on the candidate signal having a maximum correlation value.

9. A synchronizing position detecting circuit according to claim 7 , wherein the window size determining circuit selects a window size from a plurality of predetermined window sizes.

10. A synchronizing position detecting circuit according to claim 7 , wherein the window size determining circuit selects a window size based on a phase change of the received signal corresponding to the estimated distance and a phase change of the synchronizing code.

11. A synchronizing position detecting circuit according to claim 10 , wherein the phase change of the synchronizing code is caused during one sleep time due to an error of the synchronizing code generating circuit.

12. A synchronizing position detecting circuit according to claim 7 , wherein the synchronizing position determining circuit judges that the received signal is detected when the correlation function calculated by the correlation circuit exceeds a threshold value.