| 摘要 |
<p>1,166,431. Radio receiving systems. RADIO CORPORATION OF AMERICA. 4 Jan., 1968 [4 Jan., 1967], No. 703/68. Heading H4L. The output of an I.F. amplifier 10 of a television receiver is supplied via a coupling circuit 13, arranged to attenuate the sound carrier frequency, to the video detector 15, the sound and vision carriers being mixed at 12 to provide an intercarrier sound signal in conventional manner. Resonant circuits L 1 , C 1 and L 2 , C 2 are broadly tuned to the video signal and coupled through a capacitor C c .A resonant sound trap L 3 , C 3 is inductively coupled to the input circuit L 1 , C 1 and supplies sound signals in opposite phase to those appearing in circuit L 2 , C 2 so that they are cancelled at the output terminals 14, 14<SP>1</SP>. A variable resistor R adjusts the phase and amplitude of the voltage in circuit L 2 , C 2 for optimum rejection of the sound signal. The resistor R may be placed in series with the inductor L 2 , or may be dispensed with by suitable selection of the circuit components.</p> |
