| 摘要 |
<p>1,176,214. Amplitude modulation. COMMUNICATIONS PATENTS Ltd. 3 May, 1968 [25 May, 1967], No. 24398/67. Heading H3R. An electrical signal processing device comprises input and output terminals, means for deriving from an amplitude modulated signal passing between the input and output terminals a modulation component, and means establishing a signal path between the input and output terminals which includes a beam deflection tube by means of which amplitude modulation of the signals passing along the signal path is effected by the said modulation components. In a highfrequency wired television broadcasting system, the arrangement is used to compensate for loss of higher modulation frequencies due to trap circuits. Signals from input terminal 1 are applied via cascaded amplifiers 5, 7 and delay network 6 to a modulator 8, comprising a beam deflection tube. The output from amplifier 5 is also applied via further amplifier 11 to a demodulator 12, the output of which comprises the video signals, which are passed via a lowpass filter 14 to remove any colour components, to an amplifier 15. Amplifier 15 is arranged to remove any sync. pulses and its output is passed to a differentiating circuit 16 to provide signals only representing video transients. These are passed via amplifier 18 to a level selecting device 19 which provides on output line 20 only those portions of the differentiated video signal which lie between predetermined amplitude limits, so as to eliminate unwanted noise components. The output on line 20 is passed via an adjustable attenuator 21 to modulator 8 to provide further modulation of the signal. The output from amplifier 15 may in addition be applied to an echo equalizing device 24 and thence to the modulator 8 via filter 27 which removes video components and also provides an impedance match.</p> |
