| 摘要 |
A radio frequency (RF) modulator for use with an antenna, a television receiver, and a video tape recorder or the like. The RF modulator contains a modulator which converts an input video signal and an input audio signal into a modulated signal having a predetermined channel frequency; an amplifier amplifying an input signal from an antenna input terminal; and a mixer which mixes the modulated signal with the input signal amplified by the amplifier to output a mixed signal from an antenna output terminal. A first switch is connected in parallel with the amplifier between the antenna input terminal and the antenna output terminal; a second switch is connected between the antenna input terminal and the amplifier; and a third switch is connected between the mixer and the antenna output terminal. When the amplifier and the modulator are not used, a signal path from the antenna input terminal to the antenna output terminal through the first switch can be formed and isolated from the amplifier and the modulator by turning the second and third switches off, so as to reduce power consumption and signal loss. <IMAGE> |
