| 摘要 |
PURPOSE:To eliminate the need for two phase synchronizing oscillators and to simplify a circuit by providing a voltage-controlled oscillator whose frequency is controlled by the output voltage of a loop amplifier and a crystal oscillator for obtaining a difference frequency from the voltage-controlled oscillator by a mixer. CONSTITUTION:Part of an IF band signal outputted by a mixer 12 is supplied to a pilot receiver 26 and its frequency is divided by N through a frequency divider 23. The frequency-divided signal is compared with the output of a mixer 17 by a phase detector 16 to output a DC voltage corresponding to the phase difference between both signals. This DC voltage is amplified by a loop amplifier 18 and applied to the voltage-controlled oscillator 19, whose output frequency is controlled. The output of the voltage-controlled oscillator 19 is mixed with the output of the crystal oscillator 20 by the mixer 17 and the difference frequency is supplied to the phase detector 16. When the local oscillation frequency of a satellite relay varies by DELTAF, all signals of reception frequency vary by DELTAF similarly, a reception pilot wave also varies by DELTAF, and the input frequency of a receiver 26 also shifts by DELTAF. |
