| 摘要 |
1430416 Recording video signals BADISCHE ANILIN- & SODA-FABRIK AG 13 April 1973 [14 April 1972] 17816/73 Heading H4F In a method of recording broad-band videosignals, on a magnetizable medium, e.g. tape or disc, the video signal, after having its upper frequency limited by a low-pass filter 1 to a maximum fm is frequency-modulated on to a carrier fc where fc=2<SP>n</SP>fm. To reduce the bandwidth of the resulting f.m. signal to that of the recording medium, the signal (b) is frequencydivided at 3 by 2<SP>n</SP> and, after amplification at 4 and low-frequency emphasis at 5 has its lower sideband recorded on the medium. With fm=2À5 MHz, n=1, fc=5 MHz, the F.M. signal extends from 4 to 6 MHz, or from 2 to 3 MHz after frequency division and the recorded lower sideband extends downwards from the carrier fc=2À5 MHz to 2 MHz. With these parameters the modulation index or: indicating narrow band frequency modulation wherein the spectrum of the modulated signal comprises substantially only the carrier and the first order upper and lower sidebands. This results in the recorded signal comprising a component derived from the carrier at 2À5 MHz and the first order sideband derived signal extending from 2À5 MHz to 2 MHz. For replay, the recorded bandwidth compressed lower sideband signal is first high-frequency emphasized at L, C 2 , amplified at 9 and "squared-off" at 10, before being frequency-multiplied at 11. In general, n stages of differentiation and full-wave rectification are used. |
