SU1248078A1 - Versions of chrominance signal channel of secam decoder - Google Patents

Abstract

The invention relates to a color television technique and reduces the distortion caused by echoes in an LZ of a chromaticity channel. The chroma signal passes through the inverter 1 phase, the corrector 2 high frequency distortion and amplitude I Sicmpoff limiter 3 to the output in the form of a signal Uo. The output signal is delayed by the LS4 by the line interval. From the received chroma signal using the entered LZ 9 (into two lower-case intervals), adder 5, amplitude detector 6, amplitude limiter 7 and generator 8 of switching pulses, the law of switching the phase of the color subcarrier is made. In accordance with this law, the phase of the color sub-carrier is inverted with the help of the first-phase inverter so that the LZ 4 receives the color sub-carrier with the same initial phase in all rows. This ensures the elimination of distortions from echoes in LZ 4, since the echoes add to the delayed signal in the same phase in all. lines. The resulting change in amplitude of the subcarrier is easily compensated. 3 sp.f-ly, 9 Il. (L tvO Njib 00 about sj 00

Description

one

The invention relates to a color television technique and, in particular, to color television sets and video monitoring devices.

The aim of the invention is to reduce the distortion caused by echoes in the delay line of a color signal channel.

Fig. 1 shows the structural electrical circuit of the channel in the first embodiment; 2 and 3, a phase inverter; 4 shows the signal plots in the TOCHKY.X circuit of the first channel variant; 5 shows a second embodiment of the channel in the first embodiment; 6 and 7 - structural electrical diagrams of the channel according to the second and third options; in Fig.8 plot of the signals at the points of the circuit channel according to the third option; Fig. 9 illustrates examples of the execution of a switching pulse generator for the third embodiment of the channel.

The SECAM decoder chrominance signal channel contains a 1 phase inverter, 2 high frequency predistortion corrector (UHF), amplitude limiter 3, delay line 4, the delay time of which is equal to the line interval, adder 5, amplitude detector 6, amplitude limiter 7, generator 8 switching pulses, line 9 delay, the delay of which is equal to two line intervals, the delay line 10, having one piezoelectric transducer. Ka- According to the second variant, the key 11 also contains the multiplier 12, the switch 13, the first and second oscillators 14 and 15, and the third option also contains the key 16.

Channel color signal works as follows.

The essence of all options is that the received chroma signal separates the law of phase commutation by the color subcarrier and, in accordance with this law, inverts the phase of the color subcarrier so that the input of the subcarrier delay line arrives with the same initial phase on all rows,

In the first version of the channel (Fig, 1.5, the chroma signal (Fig, 4a) is fed to the input of the delay line 9. The output of the delay line 9 separates the signal (Fig, 46), which is delayed by two lines. This signal in the adder 5 is skl480782

Comes with the undelayed (FIG. 4 a). In the process, the like signals are added (Dp-c Dp; Dg-c D). As a result, the sum signal (FIG. 4c)

5 acquires amplitude modulation. The modulation has the same law as the phase change in the input signal (signals with an increased amplitude repeat in two lines on

0 third), but shifted with respect to the switching law in the input signal by one line. The amplitude detector 6 converts subcarrier packets with a variable span into a pulse of 5 different amplitudes (FIG. 4 g). This signal is limited in amplitude limiter 7 to a minimum (Fig. 4 d). The generator 8 switching pulses generates a signal that is offset from the signal to the signal (figure 4) one line so that the pulses at its output (figure 4 e) coincide in time with those lines where the phase of the input signal (figure 4 a) inverted.

25 The control signal (Fig. 4e) is connected to inverter 1 and changes the phase of the color subcarrier by 180. As a result, the subcarrier phase in the signal is color-. : The output of inverter 1 is the same in all rows.

(figure 4). This ensures the elimination of distortions from echoes in delay line 4, since echoes add up to a delayed signal in the same phase on all lines, which only leads to the same change in the subcarrier amplitude on all lines, which is easily compensated by the tuning resistor present in the channel. Perhaps a different implementation of the generator 8 switching pulses. In particular, it can be made according to the well-known scheme of the generator of switching pulses of the encoder SECAM, which is based on the horizontal frequency divider by three. In this case, the signal from the amplitude limiter 7 provides synchronization

50 generator 8 in phase. Other circuit solutions of the generator 8 switching pulses are possible.

. The 1 phase inverter can also be built differently. This may be a logical exclusive or link.

(Fig. 2), on the first input of which an input signal is applied, and on the second - a control signal from the generator 8.

3

It is possible to use a phase-split transformer (FIG. 3), the secondary winding of which is connected to the inputs of the switch. Instead of a transformer, a phase splitter on a transistor can be used,

In the channel implementation example shown in FIG. 5, where an ultrasonic delay line is used, the chrominance signal arrives at the input of delay line 1, along which the signal propagates during one line, the signal as an ultrasound wave passes through the sound line of the line, is reflected from its opposite end and returns to the input, where it is added to the input signal. The delay of the signal in this case is just two lines. An output piezo transducer in such a delay line is not needed and may not be installed. The output piezoelectric transducer performs the function of an adder,

In the second variant of the color signal channel of the SECAM decoder, the key 11 is closed under the action of lower-case strobes and passes the first input of the multiplier 12 to the protective subcarrier packets from the input signal. The switch 13 is controlled by a half-line frequency meander formed in the color synchronization block of the SECAM decoder and the corresponding phase alternation of lines D and Dp. Switch 13 passes to the second input of the multiplier 12 alternate sinusoidal signals from the first and second oscillators 14 and 15 having frequencies equal to the frequencies of the unmodulated subcarriers (such oscillators are included in the SECAM studio decoders, where they are used to form black areas for fixing the color difference signals). At the output of the multiplier 12 at the beginning of the lines where the phase of the subcarrier in the input signal is switched, short pulses are extracted. The generator 8 commuting pulses in this case consists

 from the counting trigger, to the installation input of which string gating pulses are fed, and to the counting input - the signal from the multiplier 12 output. As a result, at the output of the generator 8 switching pulses a control signal is output in the form of pulses on the lines where the phase under the carrier switches on pass

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storole. The duration of the pulses is equal to the line interval. They arrive at the control input of inverter 1 and provide a 180-phase change in the color subcarrier. Therefore, at the output of the inverter 1, the phase of the color subcarrier becomes the same on all rows, which ensures the suppression of distortions from the echo signals in the delay line.

Inverter 1 phase in all versions can be included at any point of the chroma channel up to the input of the delay line 4, t, e, at the channel input of the chroma signal, between the high-frequency predistortion corrector 2 and the amplitude limiter 3 or between the amplitude limiter 3 and the delay line 4 input. This does not change the essence of the device operation.

Consider now the operation of the third variant of the SECAM decoder chrominance channel. Its principal difference from the first two options is to remove the clock signal from the circuit point after the phase 1 inverter, namely from the input of the delay line channel 4 of the chrominance signal, which simultaneously generates the clock signal for generator 8 commuting pulses.

The chroma signal passes KVCHP 2, 1invert6p 1 phase, amplitude limiter 3 and is fed to the input line 4 of the delay. Suppose that the inverter 1 phase and the key 16 is not yet functioning. Then the chroma signal at the input is le-. The scientific research institute will consist of packages of relevant ones (FIG. 8 a), which are frequency-modulated by the R-Y and B-Y signals alternating in rows. The phase of the subcarrier varies from line to line | according to the law: 0-0-tt-O-O-TT - ,,,.,, And t, d, or -tg-0-tt-tt-O -, ,, That does not change the final result. This signal passes to the output of the delay line 4 and forms a delayed signal U (Fig. 8b), shifted with respect to the direct signal and for the time line iT, Modern delay lines to enable their use in TVs PAL / SECAM are made: for the delay time, 943 μs. In this case, the subcarrier in the signal U, is additionally shifted by 180 °, as shown in FIG. 8, b. The result does not change if

The SECAM old type delay line is used. having a delay of exactly 64 ISS. Part of the ultrasound energy, reflected from the transducer, returns to the line input to form an echo (FIG. 8c). Due to the difference in the phases of the signals and "and and J, amplitude modulation of the subcarrier packets (Fig. 8g) is created, which causes distortions on the TV screen. Strobe pulses, such as lower case, close keys 11 and 16, Key 11 removes distorted signals. subcarrier packets, areas bounded in FIG. 8 g, with dashed lines and corresponding to protective flashes of unmodulated subcarriers transmitted in line blanking intervals. The key 16 short-circuits the output of the delay line 4, which causes the delay line to misalign by the return stroke along the lines and dramatically increases the amplitude modulation of the pulses at its input. (It should be noted that frame strobe pulses can be used in the device, not horizontal. frame identification signals with amplitude modulation due to the interference of direct and reflected signals), highlighted by subcarrier flash key 11 with parasitic amplitude modulation are shown in FIG. 8, these signals decode in the amplitude detector 6 to form pulses of FIG, 8 g. By limiting the minimum in the amplitude limiter, 7 of them are pulsed with a maximum amplitude, | (Fig, 8h), which are repeated two lines after the third, m, e, correspond to the law of phase switching in the input signal (Fig. 8 a), but shifted one line down. These signals control the operation of the generator 8 switching pulses, which generates switching signals (FIG. 8 m) supplied to the control input of the phase 1 inverter. In the signal at the output of the inverter 1, the phase of the subcarrier on the active sections of the rows becomes constant, which eliminates parasitic amplitude modulation of the chrominance signal and distortion on the screen of the kinescope; In the generator. 8 commuting pulses, circuits must be provided to suppress its output signal at time

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m passing the gating pulses to keep spurious amplitude modulation of the subcarrier at these intervals on the input of delay line 4, as shown in FIG. 8n, since this modulation is a useful signal controlling the operation of the generator 8 of switching pulses. In the first two In embodiments of the proposed device, where the synchronization signal is removed before the phase 1 inverter, it is not necessary to take measures to suppress the control signal supplied to the inverter 1.

The generator 8 switching pulses in the third version can be performed according to the well-known scheme in the form of a horizontal frequency divider by three, synchronized by a signal from the amplitude limiter 7, However, other circuit solutions of this generator are possible (see FIG. 9). impulses contains counting triggers 17, 18, element EXCLUSIVE IL 19, element I 20 and inverter 21, the counting input of counting trigger 17 is fed by a lowering gating pulse, and to the installation input there is an R signal shown in FIG. 8 3 with an amplitude output The limiter 7, At the output of the counting trigger 17, there is a signal (FIG. 8) that goes to the counting input of the next counting trigger 18. The installation R-input of the counting trigger 18 receives the signal shown in FIG. 8. Signals from the outputs Both counting triggers are applied to the EXCLUSIVE OR 19 element. The signal (FIG. 8l) passes the output of this element AND 20, the second input of which is fed with inverted horizontal Strobe pulses (FIG. 8 d). As a result, The signal (FIG. 8 m) forms gaps for the duration of the flash flashes, which ensures the preservation in them of the parasitic amplitude modulation necessary for the operation of the chroma channel.

Claims (3)

Invention Formula 1, The color channel of the SECAM decoder chrominance signal, containing a series-connected high-frequency predistortion corrector (SHF), a first amplitude limiter and a first delay line, so that, in order to reduce distortion caused echo signals in the delay lines, a phase inverter is inserted into it through which either the first amplitude limiter and the first line are connected: holders, or SHF and the first amplitude limiter, or the channel input of the color signal of the SECAM decoder and SHF decoder, as well as the adder, the amplitude d Tector second amplitude limiter and a switching pulse generator sequentially connected between the input channel decoder SECAM chrominance signal and a control input of the phase inverter, the second input of the adder connected to its first input inputted through the second delay line. 2, A SECAM decoder's chrominance signal channel containing series-connected high-frequency predistortion corrector (SHF), amplitude limiter and delay line, characterized in that, in order to reduce distortions caused by echoes, a phase inverter is introduced into it, through which either the amplitude limiter and the delay lines, or the UHF and amplitude limiter, or the channel input of the color signal of the SECAM decoder and the UHF decoder, as well as the key, multiplier, and generator of switching pulses, are connected sequentially between the input of the CECAM decoder chroma input signal and the phase inverter control input, the switch, the first and second signal inputs of which are connected to the outputs of the first and second oscillators respectively input, the output with the second multiplier input, and the control input is the signal input synchronization chromaticities, wherein the control inputs of the key and the generator of switching pulses are combined and are the input of the gating pulses. 3. A SECAM decoder's chrominance signal containing a series-connected high-frequency predistortion corrector (CVSP), a first amplitude limiter and a delay line, characterized in that, in order to reduce distortion caused by echoes in the delay line, a phase inverter is inserted into it, through which or the first amplitude limiter and delay lines, or SHF and the first amplitude limiter, or the channel input of the chroma signal of the SECA and SHF decoder, as well as the first key, the amplitude detector, the second A specific limiter and a switching pulse generator, connected in series between the input of the delay line and the control input of the phase inverter, and a second switch, are connected between the output of the delay line and the common bus, the control inputs of the first and second switches and the generator of switching pulses are combined and are input gating pulses. l U8. 3 L n) I cmpoS Vo fe  Agffin AO PU8, 6 Rig. 7  H  CZ EKliIHiDHIOHIO43Ib- g n - . N / Y / ff 17 Editor M. Bandura Compiled by V. Maksimova Tehred I. Gaidosh Order 4142/59. Circulation 624 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4 U8. 9 Proofreader A. Obruchar