| 摘要 |
PURPOSE:To obtain a PN code acquisition circuit which realizes high-speed data demodulation by deciding the phase difference of carrier from a pair of correlation outputs and pulling the phase difference in the nearest phase among the phase of prescribed four points. CONSTITUTION:The carrier phase difference theta is decided by a phase decision circuit 28 based on the respective output X1 and XQ of the correlators 10 and 11 and this decision is executed by using a following formula, theta=arctan (XQ/X1). After finishing acquisition, the phase difference theta is pulled in the nearest phase among the four points of 0. pi/2, pi and (3/2)pi. Thereby, the high-speed phase synchronization of the carrier can be possible. After that, a selector 32 decides which output of the selectors 10 or 11 is selected as demodulated data based on the phase among the four points which the phase difference is pulled in. Concretely, when it is theta=0, pi, the output of the correlator 10 is selected and when it is theta=pi/2, (3/2)pi, the output of the correlator 11 is selected. |
