| 摘要 |
PURPOSE: An RF(Radio Frequency) signal level adjustor for automatic tracking control in a VCR(Video Cassette Recorder) is provided to output a specific range of RF signal level proper for automatic tracking control without regard to the kinds and magnetization of video tapes or the characteristics of a video head by setting the amplification gain of RF signals variably. CONSTITUTION: An RF signal level adjustor consists of a video head(12) reading a signal recorded on a video tape(11) as an RF signal; an amplifier(13) pre-amplifying the RF signal; an LPF(Low Pass Filter,14) converting the pre-amplified RF signal into a DC envelope signal; a microcomputer(15) outputting an automatic tracking control signal to maximize the level of the envelope signal; and a motor driver(16) driving a capstan motor(17) according to the automatic tracking control signal. The RF signal level adjustor additionally includes an ADC(Analog to Digital Converter,18) converting the analog DC envelope signal into a digital signal; a comparator and control bit generator(19) comparing the A/D-converted value with reference value and outputting a corresponding control bit; and a gain controller(20) variably setting the gain of the amplifier. The level of an RF signal is output properly for automatic tracking control. Therefore, the automatic tracking control is performed normally.
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