KR100281050B1 - Apparatus and method for detecting vertical synchronization signal of digital television - Google Patents

Abstract

The present invention relates to an apparatus and a method for detecting a vertical synchronization signal in a digital TV receiver using a residual side band (VSB) method. In particular, a vertical synchronization correlation unit for obtaining a correlation between a received signal and a preset vertical synchronization signal, The maximum position detector detects the position of the symbol having the maximum correlation degree for each field, and checks the reliability of the output of the maximum position detector and vertically synchronizes the output of the maximum position detector if the reliability is equal to or greater than the determination threshold. Consisting of a reliability measurer that recognizes the position of the signal, first detects a highly reliable vertical synchronizing signal, and then detects a horizontal synchronizing signal at a relative position from the detected vertical synchronizing signal, thereby stabilizing the synchronization of the receiving system to restore data To facilitate. In addition, there is no need for a separate horizontal synchronizing signal detecting apparatus for detecting the horizontal synchronizing signal using the vertical synchronizing signal.

Description

Apparatus and method for detecting vertical synchronization signal of digital television

The present invention relates to an apparatus and method for detecting vertical synchronization signal in a digital TV receiver using a residual side band (VSB) method.

High Definition Television (HDTV) is the next generation of digital TV system developed to make the impression of theater in the same room. Compared to today's analog TVs, the screen resolution is much higher, wider in the horizontal direction, and CD-level sound is supplied in multiple channels.

Such digital TVs are being standardized by the US, Europe, and Japan in their own broadcasting methods and standards. In the United States, the transmission format adopts the residual sideband (VSB) method proposed by Zenith in the United States, the compression format adopts MPEG (MPEG) for video compression, and Dolby AC-3 for audio compression. The display format is specified to be compatible with existing display methods.

Error correction coding (ECC) is performed on the compressed image data to digitally transmit the image data compressed according to the above standard. At this time, in order to facilitate data recovery on the receiving side, a synchronization signal is created and inserted into a predetermined period between the data before transmitting the data.

The synchronization signal is largely classified into two types, one as a horizontal synchronization signal and a data segment synchronization signal, and the other as a vertical synchronization signal and called a field synchronization signal. The horizontal and vertical synchronization signals are different from the horizontal and vertical synchronization signals of NTSC.

Here, the transmission signal frame of the VSB digital TV system is shown in FIG. That is, one frame is composed of two fields, each field is composed of 313 data segments, and one data segment is composed of 832 symbols, that is, four symbols of horizontal synchronization signals and 828 symbols of data. At this time, since the horizontal synchronization signal is not error corrected coded, each data segment is composed of four symbols of the horizontal synchronization signal and a 828 symbol data + EEC signal. In addition, each field is composed of 313 data segments. The 313 data segment is composed of one field sync segment and a general data segment of 312 including a training sequence signal.

That is, a transmitting side such as a broadcasting station passes a mapper that changes the desired power level before transmitting a signal. In the case of 8 VSB for terrestrial broadcasting, the output level of the mapper is one of eight symbol values (amplitude level). In addition, the mapper forcibly creates and inserts 4 symbols of horizontal sync signals for every 832 symbols by appointment, and forcibly creates and inserts vertical sync signals at 313 data segment positions.

And the promised form of the horizontal synchronization signal is logically 1, 0, 0, 1, with only these two levels and repeating every data segment continuously.

In addition, the vertical synchronization signal has a length of one data segment, as shown in FIG. 2, where the horizontal synchronization pattern '1001' exists in the first four symbols, and then for signal waveform equalization. There is a training sequence of the adaptive equalizer, a VSB mode signal, and a reserved region. The training sequence consists of one PN 511 signal sequence and three PN 63 signal sequences. The second PN 63 ^* signal sequence of the three PN 63 signal sequences is polarized every field. That is, '1' is changed to '0' and '0' is changed to each field.

At this time, the horizontal synchronization signal is used for timing recovery of the system while determining the start position of the segment. That is, the conventional receiving system first detects the horizontal synchronizing signal and recovers the data after detecting the timing synchronizing signal and the vertical synchronizing signal using the same.

However, since the horizontal synchronization signal is composed of only four symbols 1001, although it is repeated every segment, it may be difficult to detect the damaged channel due to the large size of the proximity ghost. Therefore, since the system timing recovery and the vertical synchronization signal detection are not started unless the horizontal synchronization signal is detected, there is a fatal disadvantage of delaying data restoration or not performing data restoration at all.

Therefore, a method of using general data symbols without using horizontal synchronization signals for system timing recovery is disclosed (Floyd M. Gardner, "A BPSK / QPSK timing-error detector for sampled receivers," IEEE Transactions on Communications, VOL. COM-34, No. 5, MAY 1986). At this time, it is not necessary to detect the horizontal synchronization signal to recover the system timing.

However, the above-described problem occurs because the horizontal synchronization signal must be used for data restoration.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an apparatus and method for detecting a vertical synchronization signal of a digital TV which detects the vertical synchronization signal before the horizontal synchronization signal.

1 is a view showing the structure of a data frame of a typical digital TV

FIG. 2 is a diagram illustrating a structure of a vertical synchronization signal of FIG. 1.

3 is a block diagram of a vertical synchronization signal detection apparatus according to the present invention;

4 is a detailed block diagram of the vertical sync correlator of FIG.

5 is an operation flowchart of the maximum position detector of FIG.

6 is a flowchart illustrating the operation of the reliability meter of FIG. 3.

Explanation of symbols for main parts of the drawings

31 vertical sync correlator 32 maximum position detector

33: reliability meter 41: sign detector

42: correlation filter 43: absolute value output

In order to achieve the above object, a vertical synchronization signal detecting apparatus for a digital TV according to the present invention includes a vertical synchronization correlation unit for obtaining a correlation between a received VSB signal and a vertical synchronization signal, and a maximum correlation for each field. And a maximum value position detector for finding and outputting a position of a symbol having a symbol, and a reliability measurer for preventing determination of a wrong vertical synchronization signal position.

The horizontal synchronization signal may be detected at a relative position from the vertical synchronization signal output from the reliability measuring unit.

The vertical synchronization signal of the next field may be detected as a relative position from the vertical synchronization signal output from the reliability measuring unit.

In the method for detecting a vertical synchronization signal of a digital TV according to the present invention, a vertical synchronization correlation step of obtaining a correlation between a received signal and a vertical synchronization signal of a pattern as inserted at a transmitting side, and a maximum correlation for each field The maximum position detection step of finding and outputting the position of the symbol having the maximum value, and the reliability of the output of the maximum position detection step are examined, and when the reliability is equal to or greater than the determination threshold value, the position of the symbol found in the maximum position detection step is vertical. And a reliability measurement step of acknowledging the position of the synchronization signal.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the present invention, since the transmission signal has a regular frame structure as shown in FIG. 1, when the vertical synchronization signal is detected first, the position of the horizontal synchronization signal can be easily distinguished from general data by the relative position from the vertical synchronization signal. That is, unlike the horizontal synchronization signal, the vertical synchronization signal is transmitted in every field, not in every segment, but is composed of a large number of symbols 832 so that detection is easy even if the channel is severely damaged. As a result, the synchronization of the receiving system is more stable, and there is an advantage in that data recovery is easy. In addition, the received signal may be received with the polarity reversed due to the characteristics of the VSB signal, and the polarity thereof may be easily determined in the process of detecting the vertical synchronization signal.

An apparatus for detecting a vertical synchronization signal of a digital TV according to the present invention for realizing this is shown in FIG. 3.

Referring to FIG. 3, a vertical sync correlator 31 for obtaining a correlation between a received VSB signal and a vertical sync signal, a maximum position detector 32 for finding the position of a symbol having the maximum correlation for each field, and an incorrect value And a reliability measurer 33 for preventing the detection of the vertical synchronization signal.

As shown in Fig. 4, the vertical sync correlator 31 is a code detector 41 for detecting a sign of an input VSB signal, a vertical sync signal value known in advance, i.e., a vertical sync of a pattern as inserted at the transmitting side. A correlation filter 42 that compares the sign detected by the sign detector 41 with each tap with the sign of the signal value as a coefficient and adds the value of each tap, and an absolute value that takes an absolute value at the output of the correlation filter 42. And a value output unit 43.

In the present invention configured as described above, the vertical sync correlator 31 uses part or all of the training sequence. Here, the training sequence refers to four horizontal synchronization signal symbols, a PN511 signal sequence 511 symbol, and three PN63 signal sequence 189 (= 63 x 3) symbols.

That is, the sign detector 41 of the vertical sync correlator 31 determines that the sign of the vertical sync signal value is '+' if the sign of the input VSB signal is larger than the reference value and '-' if the sign of the vertical sync correlator is smaller. Output to the correlation filter 42 as follows.

Here, since the vertical synchronizing signal is known as shown in FIG. 2, the coefficients of the taps of the correlation filter 42 are set to the vertical synchronizing signal pattern. At this time, the values available in the correlation filter 42 are 4 symbols of horizontal synchronization signal, 511 symbols of PN511 signal sequence, and 63 × 3 = 189 symbols of PN63 signal sequence. Therefore, every tap of the correlation filter 42 outputs 1 if the sign of the input signal and the sign of the coefficient match, and outputs 0 if it does not match. Therefore, the larger the sum of the values of each tap, the more likely the vertical synchronization signal is. In addition, since the polarity of the vertical synchronization signal may be reversed according to the result of the demodulator, there is a high possibility that the vertical synchronization signal is a vertical synchronization signal even when the value of each tap is small. This is because when the polarity is reversed, the sign of the input signal and the sign of the coefficient hardly coincide with each tap in the vertical synchronization signal section.

At this time, the polarity of the second PN63 signal sequence of the three PN63 signal sequence is calculated separately when adding the value of each tap at the output of the correlation filter 42. Therefore, the output of the correlation filter 42 is two a, b as shown in Equation 1 below.

a = Correlation value with Σ horizontal sync + Correlation value with Σ PN511 + Correlation value with 2Σ PN63

b = correlation with Σ PN63

Here, the maximum value of the number of taps of the correlation filter 42 is 4 + 511 + (3 × 63) = 704, but in actual implementation, the size may be adjusted in consideration of performance.

In this case, assuming that the total number of taps of the correlation filter 42 is N and the number of taps calculated separately is M, the a value of Equation 1 will be a value between 0 and (NM), and the value of b Will be a value between 0 and M. For example, if the total number of taps (N) is 704 and the number of taps (M) calculated separately is 63, the value of a in Equation 1 is any value between 0 and 641 (= 704-63). It becomes one value and the value of b becomes any value between 0 and 63.

If both the sign of the input signal of the correlation filter 42 and the sign of the coefficient coincide with each other, a and b in Equation 1 have the largest values MN and N, and the sign of the input signal and the sign of the coefficient are the same. If does not match, it will have zero. By the way, that the sign of the input signal and the sign of the coefficient do not match, that is, the value of a, b is 0 means that the polarity of the input signal is reversed. Finally, the intermediate value between 0 and the largest value (for example, 641 or 63) ( ) Is most likely not a vertical synchronization signal.

As described above, since the polarity of the vertical synchronizing signal may be reversed according to the result of the demodulator, the absolute value output unit 43 outputs the absolute value of the correlation filter 42 to the maximum value position detector 32 after the absolute value. do.

In this case, the absolute value of a may be obtained as in Equation 2 or Equation 3 below.

In addition, the absolute value of b may be obtained as in Equation 4 or 5 below.

Here, x is a value of the equation (1), y is a b value, Is the largest integer less than i Is 1 And, Is the smallest integer greater than i If it is two. At this time The value does not necessarily have to be an integer.

At this time, since the output of the correlation filter 42 has two a and b, there is a method of using both a and b as shown in Equation 6 below, or using only a as shown in Equation 7 when performing absolute value.

Absolute value = | a | + | b |

Absolute value = ｜ a ｜

On the other hand, the maximum position detector 32 is for detecting the position of the symbol having the greatest correlation with the vertical synchronizing signal in one field, and a flowchart thereof is shown in FIG. At this time, the register required by the maximum position detector 32 is a CNT register for storing the position of a symbol in one field, a MAX register for storing the maximum value of the output of the vertical synchronization correlator 31, and a symbol having a maximum correlation. LOC register that stores the position.

When the output of the vertical sync correlator 31 is COR, the operation sequence of the maximum value position detector 32 is as follows.

First, the CNT, MAX, and LOC registers are initialized to zero (step 501). Then, every symbol, it is checked whether the value of COR, which is the output of the vertical sync correlator 31, is greater than the value of the MAX register (step 502). At this time, if it is determined that the value of COR is less than or equal to the value of the MAX register, the value of the CNT register is increased by 1 (step 504). If it is determined to be large, the LOC register stores the value of the CNT register, and the MAX register is the value of COR. And store the value of the CNT register by one (step 503).

When step 503 is performed, it is checked whether the value of the CNT register is equal to M (step 505). Here, M is the number of symbols in one field, 832 x 313 = 260416. At this time, if it is determined that the value of the CNT register is equal to M, the maximum position detector 32 determines the value of the LOC register since the value of the LOC register at this time is the position of the symbol having the highest correlation with the vertical synchronization signal in one field. Output to the reliability meter 33 (step 506).

The CNT, MAX, and LOC registers are then initialized to zero and the process returns to step 502 (step 507).

On the other hand, the reliability measuring device 33 is for determining whether the position of the vertical synchronizing signal detected by the maximum position detector 32 is the same as the position of the actual vertical synchronizing signal, and a flowchart thereof is shown in FIG. This is because although the probability is small, there may be an array of data having a high correlation with the vertical sync signal among random data. The register required by the reliability measurer 33 is a FLOC register for storing the position of the vertical synchronization signal, a CONF register for storing the reliability of the number of repetitions, and a FOUND register for confirming whether a reliable vertical synchronization signal has been detected. When the output of the maximum position detector 32 is the LOC register value, the operation sequence is as follows.

First, the FLOC, CONF, and FOUND registers are initialized to zero (step 601). Then, for each field, the value of the FLOC register is compared with the value of the LOC register (step 602). If the two values are the same, the reliability indicated by the position of the FLOC register is likely to be that of the vertical synchronization signal.

That is, if it is determined in step 602 that the value of the FLOC register is equal to the value of the LOC register, first, the value of the CONF register is compared with the maximum value of the CONF register, that is, the maximum value N of reliability (step 603). If it is determined in step 603 that the two values are equal, the reliability can no longer be increased, and the process returns to step 602. If it is determined to be wrong, the value of the CONF register is increased by 1 (step 604).

When step 604 is performed, the value of the CONF register is compared with the decision threshold THR (step 605). In step 604, if it is determined that the value of the CONF register is less than or equal to the determination threshold value THR, the process returns to step 602. Return to 602. At this time, the determination threshold THR is a variable, and the larger the value, the greater the reliability of the detected vertical synchronization signal, but the detection time is longer initially. That is, when the value of the FOUND register is '1', the value of the FLOC register at this time is recognized as the position of the vertical synchronization signal.

On the other hand, if it is determined in step 602 that the value of the FLOC register is not equal to the value of the LOC register, the position indicated by the value of the FLOC register is not a vertical synchronization signal, thereby reducing reliability. To do this, first, compare the value of the CONF register with the minimum value 0 of the CONF register (step 607).

If the minimum value is 0, the reliability can no longer be reduced, so the FLOC register stores the value of the LOC register, that is, the position value of the new vertical sync signal, and returns to the step 602 (step 608). On the other hand, if it is determined in step 607 that the value of the CONF register is not the minimum value 0, the value of the CONF register is decreased by one (step 609).

Then compare again if the value of the CONF register is equal to the minimum value 0 of the CONF register (step 610). If it is determined in step 610 that the value of the CONF register is not the minimum value of 0 in the CONF register, the process returns to step 602. If it is determined that the value of the CONF register is 0, since there is no reliability of the detected vertical synchronization signal, the value of FOUND is changed from 1 to 0. Returning to 602 (step 611).

Here, the output of the reliability measuring device 33 is a value of the FOUND register confirming the detection of the reliable vertical synchronizing signal and a value of the FLOC register informing the position of the vertical synchronizing signal. Therefore, the value of the FOUND register output from the reliability meter 33 indicates whether the vertical synchronization signal is properly detected, and the value of the FLOC register indicates the position of the vertical synchronization signal.

In this case, since the transmission signal frame structure shown in FIG. 1 is defined in a standard, the position of the horizontal synchronization signal can be easily found as a relative position from the detected vertical synchronization signal using only counts without the need for a separate horizontal synchronization signal detection device. .

In addition, the position of the vertical synchronization signal following the detected vertical synchronization signal may also be detected as a relative position from the detected vertical synchronization signal by using a counter.

As described above, according to the apparatus and method for detecting the vertical synchronizing signal of the digital TV according to the present invention, the highly reliable vertical synchronizing signal is first detected, and then the horizontal synchronizing signal and the data starting position are detected as relative positions from the detected vertical synchronizing signal. By detecting, the synchronization of the receiving system is stabilized to facilitate data recovery. In addition, the vertical synchronization signal is easy to detect even if the channel is severely damaged, and there is no need for a separate horizontal synchronization signal detection device to detect the horizontal synchronization signal using the vertical synchronization signal.

Claims (13)

In the apparatus for detecting the vertical synchronization signal inserted every 313 data segments at the transmitting side, A vertical sync correlation unit for obtaining a correlation between the received signal and a preset vertical sync signal; A maximum value position detector for finding and outputting a position of a symbol having a maximum correlation in every field; And a reliability measurer that checks the reliability of the output of the maximum position detector and recognizes the output of the maximum position detector as a position of a vertical synchronization signal when the reliability is equal to or greater than a determination threshold value. Vertical synchronization signal detection device. The method of claim 1, wherein the vertical sync correlation unit A sign detector for detecting a sign of a received signal; A correlation filter which compares the sign detected by the sign detector with each tap and adds the value of each tap, using the sign of the vertical synchronizing signal value of the same pattern inserted at the transmitting side as a coefficient; And an absolute value output device which takes an absolute value at the output of the correlation filter. The method of claim 2, wherein the correlation filter The PN63 signal sequence device of claim 1, wherein the PN63 signal string whose polarity is inverted in each field is calculated and output when the tap values are added. The method of claim 2, wherein the absolute value output unit And an absolute value is obtained by subtracting a value obtained by dividing the number of taps of the correlation filter by two from the output value of the correlation filter. The apparatus of claim 1, wherein the horizontal synchronization signal is detected at a relative position from the vertical synchronization signal output from the reliability measuring unit. The apparatus of claim 1, wherein the vertical synchronization signal of the next field is detected at a relative position from the vertical synchronization signal outputted last by the reliability measuring unit. In the method for detecting the vertical synchronization signal inserted every 313 data segments at the transmitting side, A vertical synchronization correlation step of obtaining a correlation between the received signal and the vertical synchronization signal of the same pattern as inserted at the transmitting side; A maximum position detection step of finding and outputting a position of a symbol having a maximum correlation in every field; And checking the reliability of the output of the maximum position detection step and acknowledging the position of the symbol found in the maximum position detection step as the position of the vertical synchronization signal when the reliability is equal to or greater than the determination threshold value. A vertical TV signal detection method for a digital TV. 8. The method of claim 7, wherein the step of detecting the maximum value position is Comparing for each symbol whether the output COR of the vertical sync correlation step is greater than the value of the MAX register which stores the maximum value of the vertical sync correlation step; Increasing the value of the CNT register storing the position of a symbol in one field if it is determined that the output COR of the vertical sync correlation step is less than or equal to the value of the MAX register; If it is determined that the output (COR) of the vertical synchronous correlation step is greater than the value of the MAX register, the value of the CNT register is stored in the LOC register storing the position of the symbol having the maximum correlation, the value of COR in the MAX register, and the CNT Increasing the value of the register, Comparing the value of the CNT register with the number of symbols (M) in one field; And if it is determined in the above steps, outputting the value of the LOC register at this time to the reliability measurement step. The method of claim 7, wherein the measuring the reliability Comparing the value of the FLOC register which stores the position of the vertical synchronization signal for each field with the value of the LOC register which stores the position of the symbol having the maximum correlation; If it is determined that the two values are equal in the above step, increasing the reliability; If it is determined that the two values are not equal in the above step, reducing the reliability; And setting a FOUND register for confirming whether or not a reliable vertical synchronization signal has been detected if the reliability is equal to or greater than a determination threshold value in the above step. 10. The method of claim 9, wherein increasing the reliability And if the value of the CONF register that stores the reliability of the number of repetitions is equal to the maximum value of the reliability, the reliability is no longer increased. 10. The method of claim 9, wherein reducing the reliability is When the value of the CONF register that stores the number of repetitions is equal to the minimum value of the reliability, the reliability is no longer reduced, and the value of the LOC register is stored again in the FLOC register and the value of the FOUND register is reset to zero. TV's vertical sync signal detection method. The method of claim 7, wherein the horizontal synchronization signal is detected at a relative position from the vertical synchronization signal finally output in the reliability measurement step. 8. The method of claim 7, wherein the vertical synchronization signal of the next field is detected at a relative position from the vertical synchronization signal finally output in the reliability measurement step.