| 摘要 |
PURPOSE:To obtain a system with strong fluctuation by modulating a basic signal including phase information, detecting this at the receiving side, lowering a frequency handled when the basic signal (sub-carrier signal) is obtained and expanding the frequency pull-in scope. CONSTITUTION:In the system, a four-phase DPSK (QPSK) signal, of 1.5MHz a basic signal, is frequency-converted once and the second signal of 3.58MHz is generated. An intermediate frequency signal (carrier) (58.75MHz) is modulated by the second signal, this is converted to high frequency and transferred. Consequently, at the receiving side, the second signal is obtained by demodulating the intermediate frequency signal by an intermediate frequency detecting device 32. Further, since the second signal is different from the basis signal of 1.5MHz in frequency, a QPSK demodulator 33 sets a crystal and a peripheral circuit constant so that the oscillating device for synchronizing detection may oscillate by 3.58MHz. Consequently, it is not necessary to install the second frequency converting part with a narrow frequency pull-in scope, and the receiving system with a strong frequency fluctuation can be obtained. |
