| 摘要 |
PURPOSE:To obtain a lock range expanded by GMSK, two-phase PSK, four- phase PSK, and eight-phase PSK modulation/demodulation by setting a tracking dedicated mode. CONSTITUTION:In a capture mode 1, the frequency of a local oscillator at a reception side is switched at certain constant step width, and the frequency with the maximum correlation level of PN code at the transmission/reception sides is decided as the frequency nearest to a reception wave carrier frequency. In a tracking mode 3, the data chip of a new system is always set at (0) at the transmission side, therefore, phase change in one period of the new system at the reception side always displays (0), therefore, the frequency is decreased so as to lag the phase at the reception side when observed phase change is between 0 and 180 deg., and the frequency is increased so as to lead the phase at the reception side when it is between 180 deg. and 360 deg.. Therefore, it is enough to set the phase change due to a frequency error at a value less than (pi) for one period of the new system, and the frequency switching step width and the lock range in the capture mode can be doubled compared with that of a conventional system. |
