时间:2011-03-11 23:13来源:蓝天飞行翻译 作者:admin 点击:次
frequency doubler (electronic circuit). An electronic circuit whose output is resonant at the second harmonic of the input signal. The frequency of the second harmonic of an alternating current is exactly two times the frequency of the input AC. The output frequency of the frequency doubler is two times that of the input. frequency meter (electrical measuring instrument). An electrical instrument that measures the frequency of an alternating current and shows this frequency directly on its dial. One commonly used type of frequency meter is a vibrating reed-type instrument. A series of metal reeds of different lengths is excited by the AC, and the reed that vibrates with the greatest amplitude is resonant at the frequency of the AC. The frequency at which each reed is resonant is marked beside each reed. frequency modulation (radio communications). One method of putting an audio frequency signal on a radio frequency carrier. Rather than the AF signal changing the amplitude of the carrier, as is done in amplitude modulation (AM), the AF signal changes the frequency of the carrier by an amount determined by the amplitude of the audio signal. The amplitude of the frequency-modulated carrier is clipped so static caused by electrical interference causes a minimum of distortion. frequency multiplier (electronic circuit). An electronic circuit whose output has a frequency that is a multiple of the frequency of the input signal. Frequency doublers and triplers are commonly used frequency multipliers. |