MODULATOR

摘要

PROBLEM TO BE SOLVED: To provide a modulator for preventing any jamming to other channels under the environment of the hard mechanical impact or vibration of an air plane. SOLUTION: A first frequency converting part 31a frequency-converts a modulated wave of an intermediate frequency by using the output signal of a first local oscillating part 32. A first band limiting/amplifying part 33 band- limits and amplifies the output signal of the first frequency converting part 31a. A second frequency converting part 31b converts the output signal of the first band limiting/amplifying part 33 into a signal with a prescribed channel frequency by using the output signal of a PLL frequency synthesizer 34. When a lock detecting part 37 detects the lock deviation of the PLL frequency synthesizer 34, a microcomputer 38 turns off a signal switch part 35 for preventing any obstacle on other frequency multiplexed channels.