SU438141A1 - Chroma decoding block - Google Patents

Description

one

The invention relates to a television receiving technique and is intended for decoding color signals in SECAM television receivers.

Known lightness blocks for SECAM system television receivers, performing decoding of chroma signals without a signal delay line commonly used in such receivers for the duration of the line interval. These devices use two video amplifiers of color-difference signals, which are alternately connected to the amplifiers.

The proposed color block is simpler because it uses only one video amplifier.

Pa drawing shows the block diagram of the proposed device.

The chromaticity block includes a frequency discriminator 1, a switch 2 that controls the operation of this switch trigger 3, a video amplifier 4, a matching circuit 5 and 6, a dematrix circuit 7, and an identification device 8.

The device works as follows.

The amplified signal of the color subcarrier frequency transmitted through the limiter is demodulated by frequency discriminator 1, the outputs of which are alternately alternated at the horizontal interval by the switch 2, controlled by the signal from trigger 3. This

Color difference signals are transmitted to the input of video amplifier 4 in the corresponding polarity. Due to the difference in nominal subcarrier frequency for strings

DR and Db, at the output of the frequency discriminator, a meander type voltage is generated, to compensate for which a square wave is supplied to the video amplifier input from trigger 3 in the opposite polarity. From the exit

video amplifier 4, the amplified color-contrast signals are alternately fed to the matching circuits 5 and 6, to the other inputs of which control signals from trigger 3 are received, therefore, ER-Y EB-Y signals are alternately output from the output of the matching circuits 5 and 6. To form the EG-Y target-difference signal, dematrixing circuit 7 is used, the output of which receives the signal to the identification device 8. The identification device 8 establishes the correct polarity of operation of the trigger 3 that controls the operation of the switch 2, i.e., provides the synchronization of the receiving switch with the transmitter .

Thus, in the proposed device, color difference signals and EB-Y are alternately outputted from the output of the same video amplifier to the kinescope. This ensures simplicity and cost effectiveness.

the proposed block color compared to existing ones.

Predlmet invention

A color decoding block for a SECAM TV receiver, containing a frequency discriminator, whose input is fed a color subcarrier frequency, a video amplifier, a dematrix circuit with two inputs, the output of which is connected to the first trigger input through the identification block, and the second and third trigger inputs are lowercase a sync pulse, characterized in that, in order to simplify the color density unit, two discriminator outputs are connected to the first and second inputs of the switch, the third and fourth inputs of which are connected to the first and second outputs of the trigger respectively; one of the switch outputs is grounded and the second is connected to the first input of the dematrix circuit via serially connected video amplifier and the first matching circuit, the second input of which is connected simultaneously to the second output of the switch and the first output of the trigger connected by the second output from the second input of the dematrixing circuit through the second matching circuit, the second input of which is connected to the output of the video amplifier, and the signals from the outputs of the matching circuit and dematrixing are applied to the respective modulators.