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在研制用磁带记录宽频带信号的设备时会碰到一些问题:象频率比50赫低得多的信号的传输过程,单位长磁带上之磁通量变化很慢,这种信号的重放电平将很低;如果频率高达几兆赫,主要的问题是使磁带上波长超过磁头的缝宽,这一点用提高带速或者减小磁头缝宽可以做到.为了能够经济地利用磁带并保证信号的带宽能令人满意地传输,在磁带录像机上采用调频方式传输图像信号.本文将叙述调频特性,残留边带传输方式以及介绍一些调制器和解调器的电路.
Some problems have been encountered in the development of equipment for recording wideband signals with magnetic tapes: the transmission of signals at much lower frequencies than 50 Hz, the magnetic flux changes slowly per unit of tape, and the reproduction level of such signals will be very high Low; at frequencies up to several megahertz, the main problem is to make the wavelength of the tape exceed the head width, which can be done by increasing the tape speed or by reducing the head width. In order to be able to use the tape economically and to keep the signal bandwidth Satisfactory transmission, the use of frequency modulation in the video tape recorder to transmit image signals.This article will describe the FM characteristics, the transmission of the residual sideband and introduce some of the modulator and demodulator circuit.