| 摘要 |
PURPOSE:To reduce the residual error of a delay locked loop by providing plural correlating means, and obtaining correlation between a PN code delayed or forwarded only in a prescribed time and a digital signal from an A/D converting means. CONSTITUTION:An A/D converter 14 samples a base band signal in a speed N times as fast as a spread code in the signal. Also, squaring circuits 18 and 21 makes the outputs of first and second digital correlators 15 and 16 so as to be always positive, and an adder 19 searches the difference of the outputs of the circuits 18 and 21. Moreover, the output of the adder 19 is inputted through a loop filter 22, and the oscillation frequency of a voltage control oscillator 24 is changed according to the output of the adder 19. The correlators 15 and 16 obtain the correlation by the spread code length in the base band signal. At that time, the correlator 15 obtain the correlation between the PN delayed only on a time T{=1/2.Ts.(2m-1)} and the digital signal from the converter 14, and the correlator 16 obtains the correlation between the PN code forwarded only in the time T and the signal from the converter 14. Thus, the time width of a target point at which a phase is matched can be shortened, and the residual error of the delay locked loop can be reduced. |
