ES2021536A6 - Vestigial-band modulator for television - Google Patents

Abstract

Vestigial-sideband modulator for television, characterised in that it comprises an integrated circuit through one of the pins of which a video signal enters the modulator, an audio signal entering via another connector, in that it uses a transistor in common-emitter mode for amplifying the signal, being pre-emphasised then later entering the abovementioned integrated circuit into which a TV IF oscillator signal and a signal originating from the resonant network also enter, in that an IF amplifier compiles the modulated TV signal input then entering a surface-wave filter, a transistor having been provided for amplifying the vestigial signal appearing out of the filter, the output frequency being determined by a PLL of adjustable frequency which can be matched to that from a VCO, in that an active low-pass filter is provided for filtering the resulting oscillation, a pre- scaling circuit being present and another integrated circuit for the purpose of successively reducing this frequency, in that it uses a diode bridge for the purposes of mixing the frequency from the CO and the video signal, the low-frequency signals being selected by means of a low-pass filter, in that it uses a variable attenuator before the signal is input into the amplifier, and the amplifier unit being of the plug-in type.