Code phase error estimating method, code phase calculating method, program, code phase error estimating device, and code phase calculating device

A code phase calculating method, comprising:

• performing correlation calculation for I and Q components of a reception signal as a positioning signal modulated in spread codes and a replica signal in the spread codes;
• judging code phase based on the result of the correlation calculation;
• calculating an angle formed by position vectors of the correlation values at advanced phase and delayed phase from the code phase in advanced and delayed directions by N chip (0<N<1) plotted on IQ coordinates;
• calculating a ratio of a first difference to a second difference, the first difference being a first correlation value minus a third correlation value, the second difference being a second correlation value minus the third correlation value, the first correlation value being a correlation value at the code phase, the second correlation value being a correlation value at a phase shifted from the code phase by X chip (0<X<1), and the third correlation value being a correlation value at a phase shifted from the code phase by Y chips (1<Y);
• judging whether the reception signal is multipath signal by using the angle and the ratio;
• estimating a code phase error by using the ratio and an offset value of the ratio determined in advance for each of the spread codes when the reception signal is a multipath signal;
• and
• correcting the code phase by using the estimated code phase error when the reception signal is judged as a multipath signal.

A code phase error estimating device, comprising:

• a correlation calculating unit which calculates correlation for I and Q components of a reception signal of a spread modulated positioning signal, and a replica signal of a spread code;
• a code phase judging unit which judges code phase based on the result of the correlation calculation;
• a ratio calculating unit that calculates a ratio of a first difference to a second difference, the first difference being a first correlation value minus a third correlation value, the second difference being a second correlation value minus the third correlation value, wherein the first correlation value being a correlation value at the code phase, the second correlation value being a correlation value at a phase shifted from the code phase by X chip (0<X<1), and the third correlation value being a correlation value at a phase shifted from the code phase by Y chips (1<Y);
• and
• a code phase error estimating unit which estimates the code phase error by using the ratio and an offset value of the ratio determined in advance for the spread code when the reception signal is a multipath signal.