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背投影彩色电视机为了提高画面清晰度和伴音保真度, 在射频电视信号接收与处理部分的主要措施有三项:一是采用频率合成式高频调谐器,二是采用准分离式中频放大电路, 三是采用锁相环PLL上同步检波电路。一、频率合成式高频调谐器工作过程与特点数字方式高频调谐器有电压合成式和频率合成式两种。由于前者易受温度、电压等因素变化的影响而引起频率漂移, 克服的难度又较大,其结果导致调谐稳定度不是很高。因此, 在背投影彩色电视机和其它高档彩色电视机中均采用频率合成式高频调谐器。
Rear projection color TV In order to improve the picture clarity and sound fidelity, the main measures in the RF television signal reception and processing part of the three: First, the use of frequency synthesis of high-frequency tuner, the second is the use of quasi-separation IF amplifier Third, the use of phase-locked loop PLL synchronous detection circuit. First, the frequency synthesis of high-frequency tuner work process and characteristics of Digital high-frequency tuner voltage synthesis and frequency synthesis of two. As the former is susceptible to changes in temperature, voltage and other factors caused by the frequency drift, to overcome the more difficult, as a result of the tuning stability is not very high. Therefore, in the rear projection color TV and other high-end color TV are using frequency synthesis of high-frequency tuner.