Color mixing or interference reduction circuit in color TV decoding circuits

Claim 2

A circuit to reduce color mixing, interference, or cross-modulation, for use with a color television coding circuit, comprising an input terminal (1) receiving a luminance signal; an output terminal (7) adapted for connection to the coding circuit and supplying a low-interference luminance signal thereto; and a transmission channel between the input terminal and the output terminal; wherein, in accordance with the invention, the transmission channel comprises a subtraction circuit (3) receiving the luminance signal; a branch circuit, including a band-pass filter (4) connected to receive the luminance signal and a controlled circuit (5) having a main input terminal and a control input terminal (6), said main input terminal being serially connected with the band-pass filter, the branch circuit being connected to the subtraction circuit to apply a subtraction signal to the subtraction circuit (3); and a control signal generating circuit, connected to said control input terminal (6) and controlling the level of transmission of the controlled circuit (5) as a function of portions of the luminance signal which are approximately centrally within the range of the chroma subcarrier of a television signal.

Claim 3

Circuit according to claim 1, further including a control voltage generating means including an adjustable voltage generating element (40) having its output connected to control the controlled circuit and forming said control signal.

Claim 4

Circuit according to claim 1, wherein said controlled circuit comprises a controlled amplifier, the amplification of which is controlled by said control signal.

Claim 5

A circuit to reduce color mixing, interference, or cross-modulation, for use with a color television coding circuit, comprising an input terminal (1) receiving a luminance signal; an output terminal (7) adapted for connection to the coding circuit; and a transmission channel between the input terminal and the output terminal; wherein, in accordance with the invention, the transmission channel comprises a subtraction circuit (3) receiving the luminance signal; a branch circuit including a band-pass filter (4) connected to receive the luminance signal and a controller circuit (5) serially connected with the band-pass filter, the branch circuit being connected to the subtraction circuit to apply a subtraction signal to the subtraction circuit (3); and a control signal generating circuit controlling the level of transmission of the controlled circuit (5) as a function of a portion of the luminance signal, which portion is within the band-pass width of the chroma subcarrier of a television signal, said control signal generating circuit comprising level signal generating circuits (19,20) having the chroma difference signals (R-Y, B-Y) applied thereto, and a summing circuit (21) assuming the output signals from the level signal generating circuits.

Claim 6

A circuit to reduce color mixing, interference, or cross-modulation, for use with a color television coding circuit, comprising an input terminal (1) receiving a luminance signal; an output terminal (7) adapted for connection to the coding circuit; and a transmission channel between the input terminal and the output terminal; wherein, in accordance with the invention, the transmission channel comprises a subtraction circuit (3) receiving the luminance signal; a branch circuit including a band-pass filter (4) connected to receive the luminance signal and a controller circuit (5) serially connected with the band-pass filter, the branch circuit being connected to the subtraction circuit to apply a subtraction signal to the subtraction circuit (3); and a control signal generating circuit controlling the level of transmission of the controlled circuit (5) as a function of a portion of the luminance signal, which portion is within the band-pass width of the chroma subcarrier of a television signal, said control signal generating circuit comprising level signal generating circuits (19,20) having the chroma difference signals (R-Y, B-Y) applied thereto, and a summing circuit (21) assuming the output signals from the level signal generating circuits.

Claim 7

A circuit to reduce color mixing, interference, or cross-modulation, for use with a color television coding circuit, comprising an input terminal (1) receiving a luminance signal; an output terminal (7) adapted for connection to the coding circuit; and a transmission channel between the input terminal and the output terminal; wherein, in accordance with the invention, the transmission channel comprises a subtraction circuit (3) receiving the luminance signal; a branch circuit including a band-pass filter (4) connected to receive the luminance signal and a controlled circuit (5) serially connected with the band-pass filter, the branch circuit being connected to the subtraction circuit to apply a subtraction signal to the subtraction circuit (3); and a control signal generating circuit controlling the level of transmission of the controlled circuit (5) as a function of a portion of the luminance signal, which portion is within the band-pass width of the chroma subcarrier of a television signal, the control signal generating circuit (6; 19-23) including a synchonous demodulator (27) demodulating the luminance signals with respect to the chroma subcarrier; and a low-pass filter (29) connected to receive the output of the synchronous demodulator (29), the output of the low-pass filter providing a control signal (R) to control the controlled circuit (5) in said branch circuit (4,5).

Claim 8

A circuit to reduce color mixing, interference, or cross-modulation, for use with a color television coding circuit, comprising an input terminal (1) receiving a luminance signal; an output terminal (7) adapted for connection to the coding circuit; and a transmission channel between the input terminal and the output terminal; wherein, in accordance with the invention, the transmission channel comprises a subtraction circuit (3) receiving the luminance signal; a branch circuit including a band-pass filter (4) connected to receive the luminance signal and a controlled circuit (5) serially connected with the band-pass filter, the branch circuit being connected to the subtraction circuit to apply a subtraction signal to the subtraction circuit (3); and a control signal generating circuit controlling the level of transmission of the controlled circuit (5) as a function of a portion of the luminance signal, which portion is within the band-pass width of the chroma subcarrier of a television signal, the control signal generating circuit (6; 19-23) including a synchonous demodulator (27) demodulating the luminance signals with respect to the chroma subcarrier; and a low-pass filter (29) connected to receive the output of the synchronous demodulator (29), the output of the low-pass filter providing a control signal (R) to control the controlled circuit (5) in said branch circuit (4,5).

Claim 9

A circuit to reduce color mixing, interference, or cross-modulation, for use with a color television coding circuit, comprising an input terminal (1) receiving a luminance signal; an output terminal (7) adapted for connection to the coding circuit; and a transmission channel between the input terminal and the output terminal; wherein, in accordance with the invention, the transmission channel comprises a subtraction circuit (3) receiving the luminance signal; a branch circuit including a band-pass filter (4) connected to receive the luminance signal and a controlled circuit (5) serially connected with the band-pass filter, the branch circuit being connected to the subtraction circuit to apply a subtraction signal to the subtraction circuit (3); and a control signal generating circuit controlling the level of transmission of the controlled circuit (5) as a function of a portion of the luminance signal, which portion is within the band-pass width of the chroma subcarrier of a television signal, the control signal generating circuit including a comb filter (31, 32) having the luminance signal applied thereto and being connected to a level signal generating circuit (33) and a detector (34) to derive said control signal (Q) for application to the controlled circuit (5).

Claim 10

A circuit to reduce color mixing, interference, or cross-modulation, for use with a color television coding circuit, comprising an input terminal (1) receiving a luminance signal; an output terminal (7) adapted for connection to the coding circuit; and a transmission channel between the input terminal and the output terminal; wherein, in accordance with the invention, the transmission channel comprises a subtraction circuit (3) receiving the luminance signal; a branch circuit including a band-pass filter (4) connected to receive the luminance signal and a controlled circuit (5) serially connected with the band-pass filter, the branch circuit being connected to the subtraction circuit to apply a subtraction signal to the subtraction circuit (3); and a control signal generating circuit controlling the level of transmission of the controlled circuit (5) as a function of a portion of the luminance signal, which portion is within the band-pass width of the chroma subcarrier of a television signal, the control signal generating circuit including a comb filter (31, 32) having the luminance signal applied thereto and being connected to a level signal generating circuit (33) and a detector (34) to derive said control signal (Q) for application to the controlled circuit (5).