| 摘要 |
PURPOSE:To improve the processing capacity of the transmitter without lowering its service by simultaneously performing MSK demodulation and AM-MSK demodulation against a link establish signal and, after selecting AM-MSK or MSK modulation in accordance with the detected state of a frame synchronizing signal, transmitting a link response signal of the format of the selected modulation. CONSTITUTION:AM-MSK demodulation and MSK demodulation are simultaneously performed on the frame synchronizing signal of a link establish signal 11 and, when a frame synchronizing signal A 26 of the format of AM-MSK modulation is obtained, the signal 26 is transmitted as a link response signal 28 in a format using AMMSK and MSK modulated signals. When the signal 26 is not obtained, but a frame synchronizing signal B 27 only, the signal 27 is transmitted as the link response signal in a format using the MSK modulated signals only. Therefore, a mutual communication speed selection reference is obtained for the link establishment and, by selecting the transmitting speed on the basis of this reference, communication is performed by using the MSK modulation only in the peripheral section of a service area, while high-speed communication is performed by using the AM-MSK modulation in the central part of the service area. |
