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引言 流行的电视调谐器原理是对每一调谐频段采用二到三级预选。现行的解决办法需要长达大约5分钟的时间进行两步频率跟踪, 以便达到所有调谐的射频电路与振荡电路的 最佳同步。采用表面安装元件,在第一步频 率跟踪过程中,能部分地将这种时间消耗减 小到大约三分半钟。然而,这种方法需要昂 贵的分立元件,如匹配的调谐二极管和电容 器等。 半导体技术方面的重大进步使得有可能 研制一种调谐器自动调准集成电路。这是一 个集成在一块芯片上的预定标器,由一个锁 相环、三个数模转换器和四个高压运算放大 器组成。 系统说明 调谐器自动调准可大大地减少调整所花 费的劳力和时间。在这种系统中,每一调谐 频段的高频道(图1和图2)仅需要粗略地
Introduction The popular TV tuner principle is to use two to three preselections for each tuned band. Current solutions require up to about 5 minutes for two-step frequency tracking in order to achieve optimal synchronization of all tuned RF and oscillating circuits. With surface mount components, this time consumption can be partially reduced to about three-and-a-half minutes during the first frequency tracking. However, this method requires expensive discrete components such as matched tuning diodes and capacitors. Significant advances in semiconductor technology have made it possible to develop a tuner auto-aligning integrated circuit. This is a prescaler integrated on a single chip, consisting of a phase-locked loop, three digital-to-analog converters and four high-voltage op amps. System Description Tuner auto-alignment greatly reduces the amount of time and effort required to make adjustments. In this system, the high frequency channel for each tuning band (Figures 1 and 2) only needs to be roughly