SU1356264A1 - Decoding device of secam system receiver - Google Patents

Abstract

The invention relates to television. The object of the invention is to simplify a device by eliminating a high-speed analog-to-digital converter (ADC). The receiver device contains a high-frequency predistortion corrector 1, a color subcarrier signal conversion unit 2, a switch 3, a delay unit 4, two color difference signals formers 7 and 8, a color synchronization unit 9, a control signal conditioner IO. In order to simplify the device, two functional converters (AF) were introduced. 5 and 6. OP 5 and OP 6, implemented on the basis of permanent storage devices, convert codes proportional to the period deviation of the color subcarrier into codes proportional to the deviation frequencies, which provides linear demodulation x-ki. P-bit binary codes from the outputs of the FP 5 and FP 6, which also contain the sign bit, come from. from the yut to the inputs acc. formers of color difference signals 7 and 8. 2 3. p. f-crystals, 4 ill. 9 С / С Bxaff fj-Y о; cr a to about:. /

Description

The invention relates to a television. Technique and can be PENDED by the television receivers and video monitoring devices of the CEfCAM system. The purpose of the invention is to simplify the device by eliminating a high-speed analog-digital converter.

FIG. Figure 1 shows the electrical structure of the decoding device of the SECAM system receiver; in fig. 2 is a structural electrical circuit of a color subcarrier signal conversion unit; FIG. 3 is a structured electrical color lock circuit | Fig. 4 shows timing charts explaining the operation of the proposed device.

The decoding device of the SECAM receiver system (Fig. 1) contains a high frequency predistortion corrector 1 (CBS), a color subcarrier signal conversion unit 2, a switch 3, a delay unit 4, first 5 and second 6 functional converters first 7 and second 8 shapers of differential color signals, block 9 is the color of YOU synchronization and driver 10 control signals.

The color subcarrier signal conversion unit 2 (FIG. 2.) contains the first pulse generator 11,

frequency divider 12, first 13 and second 35 subcarriers, denoted as D;

a swarm 14 period-time meters of the color subcarrier signal, a clock generator 15, a switch 16, an arithmetic unit 17, a blend code generator 18 and a second pulse generator 19.

Color synchronization unit 9 (FIG. 3) contains LLIshekcop 20, threshold unit 21, first 22 and second 23 pulse counters, first 24 and second 25 comparators, prohibition block 26, trigger 27 and chroma deactivator 28.

Each of the drivers 7 and 8 color-difference signals (Fig. 1) contains multiplexers 29-1 and 29-2, analog-to-digital converters (D / A converters) 30-1, 31-1 and 30-2, 31-2, adders 32-1 and 32-2, low-frequency predistortion correctors 33-1 and 33-2 (kip).

The decoding device of the receiver system SECAM works as follows.,

40

D ;, (Fig. 4e). In order for the output code of block 2 to be proportional to the color deviation of the period, with respect to the unmodulated (average value) for each of the rows of the CEK / vM signal, the arithmetic block 17 subtracts the codes generated by the shifter of the offset code 18, which is

45 is supplied by pulses of a semi-line clock, coming from the first output of the color synchronization unit 9, From the outputs of the meters 13 and 14, M different codes are received through the switch

50 16, also controlled by the output divider of the frequency 12. From the first output of block 2, codes proportional to the period deviation of the color n carrier relative to the period

55 lied color subcarriers in it and red lines, arriving at the third input of the color sync block and at the inputs of the switch directly and through block 4 for

The video signal from the device input is fed to the input of the FPC 1, in which the chrominance signal is extracted and corrected in accordance with the predistortion shown on the transmitting side. From the KVP 1 output, the selected chroma signal (Fig. 4a) is fed to the input 2 of the transducer

nor a color subcarrier signal measuring the period of the color subcarrier. The first shaper 11 of the pulses of block 2 (Fig. 2c) generates short pulses (Fig. 4b) in

moments of transition color subcarrier through the zero level. The frequency of the pulses is twice the frequency of the color subcarrier. The frequency divider 12 generates square pulses whose frequency is determined by the division factor of divider 2, chosen based on the required conversion accuracy. The pulses from the output of divider 12 control the operation of the first 13

and the second 14 period meters of the color subcarrier signal, working alternately (in antiphase) and counting the clock pulses arriving at their second inputs in

even and odd half-periods of the output signal of the divider 12 (FIG. 4d). At the outputs of the meters 13 and 14, M-bit binary codes are formed, which are proportional to the color period.

and

35 subcarriers, denoted as D;

40

D ;, (Fig. 4e). In order for the output code of block 2 to be proportional. the deviation of the color subcarrier period relative to the unmodulated (average value) for each of the rows of the CEK / vM signal, in the arithmetic unit 17, the codes generated by the displacement code generator 18, which is controlled by

45 are pulses of a semi-line frequency, coming from the first output of the color synchronization unit 9, From the outputs of the meters 13 and 14, M-bit codes are received through the switch

50 16, also controlled by the output of frequency divider 12. From the first output of block 2, codes proportional to the deviation of the period of the color subcarrier relative to the period of the non-modulated color subcarriers in the blue and red lines are sent to the third input of the color synchronization unit and to the inputs of the switch 3 directly and through the block 4

holders, executed, for example, on the elements of the RAM and providing a delay for the duration of one line. Switch 3 is controlled by pulses of a half-line frequency, whereby only blue and only red lines are generated at its outputs.

Functional converters 5 and 6, performed, for example, on the basis of permanent storage devices (ROM), convert codes proportional to the deviation of the period of the color subcarrier into codes proportional to the frequency deviation, which ensures a linear demodulation characteristic. P-bit binary codes from the outputs of functional converters 5 and 6, which also contain the significant digit, are fed to the inputs of the corresponding drivers 7 and 8 of color difference signals, each of which contains multiplexers 29-1 (29-2), two DACs ( 30-1, 31-1 and 30-2, 31-2), adders 32-1 (32-2) and KNP 33-1 (33-2). Each of the DACs is unipolar, therefore, depending on the sign bit value in the output code of function converters 5 and 6, multiplexer 29-1 passes the input code to the first DAC 30-1 or to the second DAC 31-1, and their output signals in the adder 32-1 taking into account the sign. The analogue color signal obtained in this way, via KNP 33-1, is output to the device. Similarly, a second color difference signal is formed at the output of the second; shaper 8. In FIG. 4e represents; a signal, the unit level in which corresponds to the active part of the line; in fig. 4g, the signals at the outputs of the first and second functional transducers 5 and 6 are conditionally presented, and FIG. 4h - output: signals from the formers 7 and 8 color difference signals.

The correct alternation of the phases of operation of the shaper 18 of the block 2, as well as to the switch 3, is provided by a color-locking block 9 (Fig. 3), in which the trigger 27 of the line frequency pulses forms a square line frequency generator.

When you turn on the television receiver, the signal coming from the output of the trigger 27 of the block 9 color sync

ten

15

20

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This may result in a phase mismatch with the order in which the color-difference signals arrive at the outputs of switch 3. This leads to incorrect color reproduction. Therefore, the task of the color synchronization unit 9 is to set the correct phase of the pulses coming from the output of the trigger 27 to the control inputs of the switch 3 and the generator 18 of the offset code of the unit 2, and to generate a color off signal when receiving a black and white image. This is achieved by means of identification signals transmitted during the action of quenching pulses on frames that come from the second output of the driver 10 of the control signals to the second input of the block 9.

The color synchronization unit 9 operates as follows.

The frame damping pulses arrive at the second gating. the input 25 of the multiplexer 20 of block 9 and together with the horizontal pulses of the horizontal frequency at the first gate entrance prepare the multiplexer 20 for passing alternating codes from the video of the block 2 to the inputs of the threshold block 21. On the front of the frame extinguishing pulse, the counters 22 and 23 are transferred to the initial state The signal is turned off, and the driver of the color off signal 28 is transferred to the state of a higher color off signal, which is fed to the first inputs of the driver 7 and 8 of the color difference signals.

The alternating codes from the output of block 2 are fed through multiplexer 20 to its input, depending on the sign bit at its control input. At the same time, identification signal codes

thirty

35

40

colors for red lines come with a minus sign, and for blue lines

plus sign The threshold unit 21 generates a pulse at its first output whenever the numerical value of the input code on the first input exceeds the number A1 or when the numerical value of the input code on the second exceeds the number A2. Similarly, threshold block 21 generates a pulse at its second output whenever the numeric value of the input code on the first input exceeds the number B1 or when the numerical value of the input code on the second input exceeds the number B2. Number of pulses

The excess thresholds are detected by the counters 22 and 23, previously set to the zero state. In this case, the counter 22 records the number of exceedances for the duration of nine line intervals with the correct arrival phase of the rectangular control pulses from the trigger 27, and the counter 23 with the wrong arrival phase. The accumulated values of the numbers in counters 22 and 23 are compared with threshold numbers Cp (corresponding to the number of periods of measured color recognition signals at nine line intervals) by comparators 24 and 25. At their outputs, they form signals when the number from the output of the corresponding counter exceeds compared threshold number Cn. However, when a signal appears at the output of the comparator 24, the signal at the output of the comparator 25 is blocked by the prohibition unit 26.

If the lines are correctly synchronized, the pulse signals are generated on the code of the comparator 24 and are fed to the first input of the color disconnect signal generator 28, switching it to a state of turning on the color switch signal and prohibiting the control signal from passing through the last extinguishing pulse to interval of frame duration. The signal from the output of the second comparator 25 through the block 26 of the ban does not arrive at the corrective input of the trigger 27.

In the case of incorrect synchronization, the pulse signals are generated only at the output of the second comparator 25, pass uninterruptedly through the prohibition block 26 to the first input of the trigger 27, thereby establishing the correct sequence of formation of rectangular pulses at its output. This accomplishes the correction of the phase of the trigger 27 when it is incorrectly initially installed. The absence of a pulse from the first comparator 24 does not change the state of the driver on the basis of the color off signal over the entire frame duration interval and permits the passage of pulses on the front of the frame extinguishing pulse to the second input of the driver 28 of the color off signal for the following frame intervals. The operation of block 9 in the absence of color recognition signals, i.e. gfi taking a black and white image is similar,

Shaper 10 control signals are designed to generate from the pulses the frequency of lines and fields of arbitrary shape (for example, from the reverse pulses) pulses

line and frame frequencies with normalized parameters both in amplitude and in time (duration and phase).

The second driver 19 block 2

generates clock pulses for block 4 of the delay, synchronizing its operation with the incoming input information, and horizontal pulses from: the first output of block 10, arriving at the third input

unit 4, synchronize its operation with the horizontal scanning frequency by linking the start of the write / read process to the beginning of the active part of the line.

Thus, unlike the analogs, the proposed device provides high accuracy and stability of parameters due to the use of digital signal processing methods, however, it is much simpler than the prototype, due to the exclusion of a parallel high-speed ADC, as well as simplifying the procedure for demodulating a frequency-modulated chrominance signal.

Claims (3)

Invention Formula . The decoding device of the SECAM system receiver, containing a series-connected high-frequency predistortion corrector, a color subcarrier signal conversion unit, a delay unit and a switch, the second input of which is connected to the transducer the output of the color subcarrier signal conversion unit, and the control input is connected to the first output of the color burst unit, the second output of which is connected to the first the inputs of the first and second drivers of color-difference signals, the outputs of which are the outputs of the device, while the first and second inputs of the color lock unit connect neny respectively with the first and second-. control signal generator outputs, the first and second JCOTO inputs are inputs of the horizontal and frame frequency pulses, respectively. you. duplicating topics that, in order to simplify the device by eliminating the high-speed analog-digital converter, the first and second functional converters are inserted, connected respectively between the first and second outputs of the switch and the second inputs of the first and second shapers of the color difference signals, while the second and third inputs of the color conversion signal block - during the day they are connected respectively with the first outputs of the color-locking unit and the driver of control signals, and the third input of the color-coded unit nhronizatsii connected to the first input of the delay unit. 2. The device according to claim 1, characterized in that the color subunit signal conversion unit comprises serially connected first pulse shaper and a frequency divider, the output of which is connected via a switch to the first input of the arithmetic unit, as well as to the second pulse shaper. the first inputs of the first and second period meters of the color subcarrier signal, the second inputs of which are connected to the output of the clock generator, and the outputs are connected to the second and third inputs of the switch, respectively, The second input of the arithmetic unit is connected to the code of the displacement code generator, and the output is the first output F Omw ten the subcarrier signal conversion unit, the second output of which is the output of the second pulse driver, and the first, second and third inputs are respectively the input of the first pulse driver,. the input of the bias code generator and the second input of the frequency divider, 3. The device according to claim 1, about tl and tea. The color block contains a multiplexer, the first and second gating inputs of which are The first and second inputs of the color-locking unit, the third input of which is the bus-connected signal and control inputs of the multiplexer, the first and second the outputs of which are connected to the same inputs of the threshold unit, the first and second inputs of which through the successively connected first pulse counter and the first comparator, as well as the second pulse counter and the second comparator are connected to the first and second inputs of the prohibition unit, the output of which is connected via a trigger to the first output of the color-locked block, the second input of the trigger is connected to the first gate input of the multiplexer, the second gate input is connected to the second inputs of the first and second counters pulses and with the first input of the chroma cut-off signal generator, the output of which is the second output of the color-locking unit. FROM Phie. 2 arZ ffd .s - d VTT Bi Ш1 / f2 tF№ ll : rtJ Compiler L. Stasenko Editor A. Makovska Tehred L. Serdyukova Proofreader S. Cherni 5815/57 Circulation 636 Subscription Vshipi State Committee of the USSR for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Design, .4 FIG.