Abstract: In a television receiver a downconverter responding to a selected television signal respectively supplies its first and second output signals as the input signals of first and second IF amplifiers, respectively. The downconverter includes a local oscillator for generating oscillations at a frequency controlled in response to the AFT signal. The first IF amplifier includes a first adjacent-channel sound carrier trap, in consequence whereof the first-IF-amplifier response is substantially reduced for the downconverted picture carrier, and an in-channel sound carrier trap. Responsive to the first-IF-amplifier response, a video detector generates a composite video signal in which sound beats are suppressed to relatively low level by the first adjacent-channel sound carrier trap.

Abstract: An NTSC interference canceler for eliminating NTSC signal interference from a HDTV signal uses recursive notch filters with adjustable center frequencies to isolate an NTSC signal's major components, i.e. the picture carrier signal, the chrominance subcarrier signal and the audio carrier signal. A single filter is used to isolate each NTSC interference signal component, with each particular filter's center frequency being adjusted to match the frequency of the particular NTSC interference signal component to be isolated by the filter. Each filter's gain may be either fixed or dynamically adjusted to match the amplitude of the NTSC interference signal component. Once isolated, these interference signal components are subtracted from the received television signal which includes both the NTSC interference signal and the HDTV signal. In this manner, the NTSC interference is removed from the HDTV signal.