U.S. Philips Corporation

Herbert Heinemann

Gunter Hildebrandt

Shin-Ichi Uchiyama

A circuit arrangement processes a color signal reproduced from a record carrier, preferably a video tape, and modulated on a carrier wave of a first carrier frequency (color-under signal). The color signal modulated on the first carrier frequency is applied to a first mixer which converts the color signal to a second carrier frequency by mixing it with a first mixing signal. An output signal of the first mixer is applied to a comb filter circuit, whose output signal is applied to a second mixer. The second mixer converts the comb-filtered signal to a third carrier frequency by mixing it with a second mixing signal, in order to achieve an optimum comb filtering. The first mixing signal is subjected to a phase shift of a given magnitude by a first phase shifter after a given number of picture lines of the color signal. Each phase shift is in addition to the previously applied phase shifts and is selected so as to compensate for the possible non-integral ratio between the period of one picture line and the period of the color signal modulated on the first carrier frequency, in such a manner that a period of the color carrier wave on the input of the comb filter circuit begins at the beginning of the next picture line. A second phase shifter subjects the second mixing signal to a phase shift of the same magnitude but of opposite sign at the same instants.

Circuit arrangement for phase shifting a color signal prior to comb

For purposes of simple construction and universal application, a circuit arrangement for frequency conversion of a color signal to a second carrier frequency, this color signal being present in picture lines and including a color burst and a chrominance information signal modulated on a chrominance sub-carrier of the first carrier frequency, the circuit arrangement being switchable in a mode for conjugate-complex formation in which it generates an output signal in which, additionally to the frequency conversion, the color signal has a phase position in accordance with the standard, which alternates from picture line to picture line, and which color signal is present in a conjugate-complex form in every second picture line, is characterized in that

Circuit arrangement for frequency conversion of a color signal

In a circuit arrangement for processing a color subcarrier signal reproduced by a video recorder and modulated on a carrier with a first carrier frequency to let a comb filter circuit in the arrangement have the least possible required memory capacity, there is provided that the color subcarrier signal modulated on the first carrier frequency is applied to a first mixer (1) by which the color subcarrier signal is converted to a second carrier frequency which is higher than the first carrier frequency, that the output signal of the first mixer (1) is applied to a comb filter circuit (2, 3, 4) which suppresses adjacent track originating crosstalk color signals in the reproduced color signal, and that the output signal of the comb filter circuit (2, 3, 4) is applied to a second mixer (5) by which the comb-filtered signal is converted to a third carrier frequency which is higher than the second carrier frequency.

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Pinneberg, Germany

Herbert Heinemann