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在彩色电视机中,为了将相邻两行色度信号产生的色度失真相互抵消,需要把前一行的色度信号延时一个行周期(指采用标准PAL解码的电视机)。这种延时是用一种特制的超声延迟线来实现的,其电路符号如图所示。 超声延迟线的特性 超声延迟线是以压电陶瓷作为换能器,玻璃作介质,并利用超声波在玻璃介质中传播速度变换的特点制成的。因为一根长度为17.6cm的玻璃棒就能使声波延时
In color televisions, in order to cancel chrominance distortion caused by two adjacent lines of chrominance signals, it is necessary to delay the chrominance signals in the previous line by one line period (referring to a television set using standard PAL decoding). This delay is achieved using a special ultrasonic delay line, the circuit symbol as shown. Ultrasonic delay line characteristics Ultrasonic delay line is based on the piezoelectric ceramic as a transducer, glass as a medium, and the use of ultrasonic wave propagation velocity in the glass medium made of characteristics. Because a length of 17.6cm glass rod can make the sound delay