KR0179569B1 - Apparatus for generating data field synchronizing signals and ghost cancel reference synchronizing signals - Google Patents

Abstract

The present invention relates to an apparatus for generating a data field synchronization signal and a ghost cancellation reference synchronization signal, wherein the apparatus of the present invention is a television receiver capable of receiving all of a QAM signal, a VSB signal, and an NTSC signal. ; A first field reference signal generator 32; A ghost removal reference signal generator 34; Multiplexer 36; A first subtractor 38; A first integrator 40; A first minimum error signal detector 42; A first counter 44; A second field reference signal generator 46; A second subtractor 48; Second integrator 50; A second minimum error segment detector 52; And a second counter 54. According to the present invention, the data field synchronization signal and the ghost cancellation reference synchronization signal are considered in consideration of the similarity between the VSB data field synchronization signal generator and the NTSC ghost cancellation reference synchronization signal generator. Implementing them all can reduce chip size as well as reduce power consumption.

Description

Data field sync signal and ghost cancellation reference sync signal generator

1E is a frame-by-frame VSB data structure diagram of a GA HDTV system.

2 is a block diagram of a field synchronization signal in VSB.

3 is a block diagram of a conventional VSB data field synchronization signal generator.

4 is a block diagram of a data field synchronization signal and a ghost cancellation reference synchronization signal generator according to the present invention.

* Explanation of symbols for main parts of the drawings

30: mode selector 32: first field reference signal generator

34: ghost cancellation reference signal generator 36: multiplexer

38: first subtractor 40: first integrator

42: first minimum error signal detector 44: first counter

46: second field reference signal generator 48: second subtractor

50: second integrator 52: second minimum error signal detector

54: second counter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for generating a data field synchronization signal and a ghost cancellation reference synchronization signal. In particular, the present invention relates to a data field sync signal of a VSB signal in a television receiver receiving all of a QAM signal, a VSB signal, and an NTSC signal. Considering the similarity between the generating device and the Ghost Cancel Reference (GCR) synchronization device generating the NTSC signal, the data field synchronization signal of the VSB signal and the ghost cancellation reference synchronization signal of the NTSC signal are generated. A data field synchronization signal and a ghost cancellation reference synchronization signal generator.

Information is one of the most important resources and is called the information society in modern times. As the amount of information to be accepted and processed is increasing day by day, data compression is indispensable to effectively use existing transmission bands.

In particular, since a digital video signal requires a lot of memory for the representation of the information, the image information compression technology enables more efficient storage, retrieval, and transmission of information.

Each system proposes a variety of data compression techniques in high definition television (hereinafter referred to as HDTV). Such data compression techniques include motion estimation (ME) and motion compensation (MC). ), Discrete Cosine Transfrom (DCT), Quantization (Q), Variable Length Coding (VLC), and the like. I use it.

Highly compressed image data through the data compression technique described above forms a certain data format and is transmitted to the receiving end.

There are various transmission methods for HDTV transmission system for transmitting compressed video data. For example, digital methods such as DigiCipher, DSC-HDTV, ADTV, and CCDC are used. Grand Alliance (hereinafter referred to as GA) was formed to determine the final transmission method.

Referring to the four transmission schemes listed above, the GigiCipher scheme is proposed by GI (General Instrument) and Massachusetts Institute of Technology (MIT). In this system, quadrature amplitude modulation is performed to transmit a 20Mbps signal with a bandwidth of 6MHz. Quadrature Amplitude Modulation (hereinafter referred to as QAM). 16QAM has a wider broadcast area than 3QAM, while image quality is lower than 32QAM. Therefore, 32QAM is set as the default transmission mode, and 16QAM can be used in special cases such as where co-channel interference is severe or where broadcast power cannot be increased. In other words, the 32QAM mode can transmit a better image quality than the 16QAM mode when the carrier-to-noise ratio (hereinafter referred to as C / N) becomes 16.5 dB or more, whereas the 16QAM mode has a C / N threshold of 12.5. If it is lower than dB, it is a transmission method that enables HDTV broadcasting over a wider area although there is a slight deterioration in image quality.

DSC (Digital Spectrum Compatible) -HDTV is a method proposed by Zenith and ATT that combines powerful video compression and simultaneous broadcasting system to provide high quality even after compressing wide bandwidth into 6MHz bandwidth. The system transmits compressed signals using taboo channels with minimal mutual interference with NTSC channels. This system has the effect of eliminating interlaced artifacts using the 787.5 line progressive scan method. Another feature of the DSC-HDTV system is that the four-level residual side band (hereinafter referred to as VSB) modulation method is used to eliminate noise and interference signal interference, thereby extending the service area. The 4-VSB coating is supplemented by a 2-VSB system that can broaden the service area. This modulation method is classified into two-level data or four-level data according to the importance of data, and transmits them with different immunity to noise. In other words, important information is transmitted as two levels of data, which ensures a certain level of image quality and sound quality even when noise and other disturbing signals are present in a distant place from the transmitter, and the extra information necessary to obtain a full HDTV quality is transmitted. It is a technique for transmitting data with 4 levels of efficiency. In this way, the cliff effect can be eliminated.

The ADTV scheme was proposed by the Advanced Television Research Consortium (ATRC) of Philips and Thomson, and the biggest feature of the ADTV transmission scheme is the Spectally Shaped QAM (QAM), which has a spectrum formed to minimize co-channel interference of NTSC signals. It is called SS-QAM). SS-QAM is a method of independently QAM modulation of two separate channels each consisting of data having HP (High Priority) and data having SP (Standard Priority).

The Channel Compatible DigiCipher (CCDC) scheme has been proposed by MIT and GI. The main characteristics of this system are the data rates of 21.5Mbits / sec for 16QAM and 26.43Mibts / sec for 32QAM. The 3dB bandwidth is 5.28MHz with a C / N threshold of 11.7dB for 16QAM and 15.7dB for 32QAM.

On the other hand, in order to drastically improve the poor image quality and sound quality of the current analog television system, the digital TV broadcast as described above will be trial-casted. Considering the penetration rate of the digital television, the current analog broadcasting It will last for a while.

The U.S. has set VSB modulation as a standard for HDTV terrestrial and cable broadcasting, but QAM is currently used for cable broadcasting, and it is expected to be used as a transmission method with VSB in the future.

Therefore, there is a need to develop a television receiver capable of receiving both QAM signals, VSB signals, and NTSC signals, and an apparatus that processes each signal even if a television receiver is implemented that can receive all such QAM signals, VSB signals, and NTSC signals. Considering the similarity between them, it is necessary to implement economical hardware.

In particular, in the television receiver receiving both QAM, VSB, and NTSC signals, the digital transmission methods VSB and QAM provide excellent picture quality, but in analog NTSC, picture quality is degraded due to ghosting caused by multipath. In order to remove such ghosts, the ghost removal reference signal is included in the transmission signal for transmission and the ghost is removed with the ghost removal signal. In this process, a device for synchronizing the ghost removal reference signal is required.

Prior to synchronizing the ghost cancellation reference signal, the ghost cancellation method is described in detail.

There are many ways to remove ghosts, but the best method is to send a ghost cancellation reference (GCR) signal and compare the reference signal distorted by the multipath at the receiving end with the original undistorted reference signal. Find the distortion level and use it to remove ghosts.

In order to compare the distorted ghost cancellation reference signal with the original undistorted ghost cancellation signal during ghost removal, synchronization of the ghost cancellation reference signal must be preceded first.

FIG. 1 is a frame-by-frame VSB data structure diagram of a GA HDTV system. In the GA HDTV transmission system, data is transmitted in frame units.

As shown in FIG. 1, one frame consists of two fields, each field consists of 313 segments, and the first segment of each field has a field synchronization signal. Sync), and each segment is composed of 836 symbols, and the first four symbols are assigned a segment sync signal.

When data is transmitted to the receiving end in the structure shown in FIG. 1, the receiving end enables stable signal tracking even in the presence of severe noise and interference due to the segment synchronizing signal and the field synchronizing signal.

The data segment synchronization signal and the field synchronization signal have two levels, but other signals have several levels.

In case of terrestrial broadcasting, it consists of 8-level signals, which means that 3 bits are allocated per unit symbol, which is called 8-VSB.

In addition, in the case of cable broadcasting, a 16-level signal is transmitted and 4 bits are transmitted per unit symbol, which is called 16-VSB.

2 is a block diagram of a field synchronization signal in a VSB. The data segment synchronization signal uses four symbols, which have two levels of +5 and -5 and occur at a period of 77.695 µS.

In addition, a field sync signal is allocated to a front end of each field to form a segment. The field sync signal includes a PN sequence of 511 symbols in length, a PN sequence of 63 symbols in length, a control symbol, and the like. The PN sequence of 63 symbols in length is repeated three times, and the sign of the second PN sequence is inverted for each field.

The data field synchronization signal is used for field synchronization purposes, but is also used as a training signal for an equalizer and a phase tracker, and this signal is also used to determine whether to use an NTSC interference cancellation filter.

FIG. 3 is a block diagram of a conventional VSB data field sync signal generator, and a conventional VSB data field sync signal generator is configured to generate a first field reference signal by receiving a data segment sync signal. A field reference signal generator 10; A first subtractor 12 outputting a difference signal by subtracting an input data segment and a first field reference signal from the first field reference signal generator 10; A first integrator (14) for integrating the difference signal from the first subtractor (12) and outputting an integral value; A first minimum error segment detector (16) for detecting a data segment having a minimum error in accordance with the integral value from the first integrator (14); A first counter (18) which determines that field synchronization has been made when a data segment having a minimum error from the first minimum error segment detector (16) occurs regularly; A second field reference signal generator 20 for receiving a data segment synchronization signal and generating a second field reference signal; A second subtractor (22) for subtracting the input data segment and the second field reference signal from the second field reference signal generator (20) to output a difference signal; A second integrator (24) for integrating a difference signal from the second subtractor (22) to output an integral value; A second minimum error segment detector (26) for detecting a data segment having a minimum error according to the integral value from the second integrator (24); And a second counter 28 which determines that field synchronization has been made if a data segment having a minimum error from the second minimum error segment detector 26 occurs regularly.

Referring to FIG. 3, the synchronization principle is briefly described. The difference between the input data segment and the field reference signal is integrated in each segment unit (832 Symbol), and the integrated value is divided into segments smaller than a predetermined threshold. The field sync signal is to be selected as a segment.

In implementing the NTSC ghost cancellation reference signal generator, there is a need to manufacture an economically useful television receiver considering the similarity to the conventional VSB data field synchronization signal generator described above.

Accordingly, the present invention has been made to meet the above necessity, and the ghost cancellation of the data field synchronization signal generator of the VSB signal and the NTSC signal in a television receiver capable of receiving all of the QAM signal, the VSB signal and the NTSC signal. It is an object of the present invention to provide a data field synchronization signal and a ghost cancellation reference synchronization signal generator configured to generate both a data field synchronization signal of a VSB signal and a ghost cancellation reference synchronization signal of an NTSC signal in consideration of similarities between the reference synchronization signal generators. .

The data field synchronizing signal and the ghost cancellation reference synchronizing signal generator of the present invention for achieving the above object are data segment synchronizing signals of VSB in a television receiver capable of receiving all of a QAM signal, a VSB signal, and an NTSC signal. A mode selection unit which receives a horizontal synchronization signal of the NTSC and outputs a control signal according to the input signal; A first field reference signal generator for generating a first field reference signal according to the control signal from the mode selector; A ghost removal reference signal generator configured to generate a ghost removal reference signal according to the control signal from the mode selector; A multiplexer for selecting one of a first field reference signal from the first field reference signal generator and a ghost removal reference signal from the ghost removal reference signal generator according to a control signal from the mode selector; A first subtractor for outputting a difference signal by subtracting a selection signal from the multiplexer from an input VSB signal or an NTSC signal; A first integrator that integrates the difference signal from the first subtractor and outputs an integral value; A first minimum error signal detector for detecting a minimum error signal in accordance with an integral value from the first integrator; A first counter receiving a minimum error from the first minimum error signal detector and outputting a first data field synchronization signal or a ghost cancellation reference synchronization signal; A second field reference signal generator for generating a second field reference signal according to the control signal from the mode selector; A second subtractor configured to subtract the data segment of the input VSB and the second field reference signal from the second field reference signal generator to output a difference signal; A second integrator which integrates the difference signal from the second subtractor and outputs an integral value; A second minimum error signal detector for detecting a minimum error signal in accordance with an integral value from the second integrator; And a second counter receiving the minimum error signal from the second minimum error signal detector and outputting a second data field synchronization signal.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

4 is a block diagram of a data field synchronizing signal and a ghost cancellation reference synchronizing signal generator according to the present invention, in which a television receiver capable of receiving both a QAM signal, a VSB signal, and an NTSC signal, A mode selector 30 which receives an NTSC horizontal synchronization signal and outputs a control signal according to the input signal; A first field reference signal generator 32 generating a first field reference signal according to the control signal from the mode selector 30; A ghost removal reference signal generator 34 generating a ghost removal reference signal according to the control signal from the mode selector 30; One signal from the first field reference signal from the first field reference signal generator 32 and the ghost removal reference signal from the ghost removal reference signal generator 34 according to the control signal from the mode selector 30. A multiplexer 36 for selecting a; A first subtractor 38 for subtracting a selection signal from the multiplexer 36 from an input VSB signal or an NTSC signal to output a difference signal; A first integrator (40) for integrating the difference signal from the first subtractor (38) to output an integral value; A first minimum error signal detector (42) for detecting a minimum error signal in accordance with an integral value from the first integrator (40); A first counter 44 which receives a minimum error signal from the first minimum error signal detector 42 and outputs a first data field synchronization signal or a ghost cancellation reference synchronization signal; A second field reference signal generator 46 for generating a second field reference signal according to the control signal from the mode selector 30; A second subtractor 48 for subtracting the input data segment of the VSB and the second field reference signal from the second field reference signal generator 48 to output a difference signal; a difference signal from the second subtractor 48 A second integrator 50 for outputting an integral value by integrating a second integrator; a second minimum error segment detector 52 for detecting a minimum error signal in accordance with an integral value from the second integrator 50; and the second minimum error The second counter 54 receives a minimum error signal from the signal detector 52 and outputs a second data field synchronization signal.

Next, look at the operation and effect of the present invention configured as described above are as follows.

When the VSB signal is inputted and when the NTSC signal is inputted, the description will be given.

1) When inputting VSB signal

When the data segment synchronization signal of the VSB is input to the mode selector 30, a control signal according to the data segment synchronization signal is output, and the control signal is input to the first field reference signal generator 32 and the multiplexer 36. In this case, the first field reference signal generator 32 generates a first field reference signal, and the first field reference signal is selected by the multiplexer 36.

The first subtractor 38 subtracts the input data segment of the VSB and the first field reference signal selected by the multiplexer 36 to output a difference signal, and the difference signal is integrated in the first integrator 40 to integrate the integrated value. Is output.

The minimum error segment is detected when the integral value is input to the first minimum error signal detector 42, and the first counter 44 determines that the field is synchronized when the minimum error segment occurs regularly (every 626 segments). do.

When the control signal from the mode selector 30 is input to the second field reference signal generator 46, a second field reference signal is generated, and the second subtractor 48 generates a data segment of the input VSB. The difference signal is output by subtracting the second field reference signal, and the difference signal is integrated in the second integrator 50.

When the integral value from the second integrator 50 is input to the second minimum error signal detector 52, the minimum error segment is detected. At the second counter 54, if the minimum error segment occurs regularly, the data field is synchronized. Is determined to be.

2) NTSC signal input

When the NTSC horizontal synchronization signal is input to the mode selector 30, a control signal according to the horizontal synchronization signal is output. When the control signal is input to the ghost removal reference signal generator 34 and the multiplexer 36, the ghost is output. The removal reference signal generator 34 generates a ghost removal reference signal, and the generated ghost removal reference signal is selected by the multiplexer 36, wherein the ghost removal reference signal is used as a PN sequence and a complimentary. Complementary sequence, sin x / x, and the like.

The first subtractor 38 outputs a difference signal by subtracting the input NTSC signal and the ghost removal reference signal selected by the multiplexer 36, and the difference signal is integrated in the first integrator 40 and output as an integral value. do.

When the integral value is input to the first minimum error signal detector 42, a minimum error signal is detected, and the first counter 44 receives the minimum error signal and outputs a ghost removal reference synchronization signal.

As described above, according to the present invention, the data field synchronization signal and the ghost cancellation reference synchronization signal can be generated in consideration of the similarity between the VSB data field synchronization signal generator and the NTSC ghost cancellation reference synchronization signal generator. As a result, the chip size can be reduced as well as the power consumption.

Claims (1)

In a television receiver capable of receiving both a QAM signal, a VSB signal, and an NTSC signal, the mode selector 30 receives a data segment synchronization signal of a VSB and a horizontal synchronization signal of an NTSC, and outputs a control signal according to the input signal. )Wow; A first field reference signal generator 32 generating a first field reference signal according to the control signal from the mode selector 30; A ghost removal reference signal generator 34 generating a ghost removal reference signal according to the control signal from the mode selector 30; According to the control signal from the mode selector 30, one of the first field reference signal from the first field reference signal generator 32 and the ghost removal reference signal from the ghost removal reference signal generator 34 is selected. A multiplexer 36 for selecting a signal; A first subtractor 38 for subtracting a selection signal from the multiplexer 36 from an input VSB signal or an NTSC signal to output a difference signal; A first integrator (40) for integrating the difference signal from the first subtractor (38) to output an integral value; A first minimum error signal detector (42) for detecting a minimum error signal in accordance with an integral value from the first integrator (40); A first counter 44 which receives a minimum error signal from the first minimum error signal detector 42 and outputs a first data field synchronization signal or a ghost cancellation reference synchronization signal; A second field reference signal generator 46 for generating a second field reference signal according to the control signal from the mode selector 30; A second subtractor (48) for subtracting the input data segment of the VSB and the second field reference signal from the second field reference signal generator (48) to output a difference signal; A second integrator (50) for integrating the difference signal from the second subtractor (48) to output an integral value; A second minimum error segment detector (52) for detecting a minimum error signal in accordance with an integral value from the second integrator (50); And a second counter 54 which receives the minimum error signal from the second minimum error signal detector 52 and outputs a second data field synchronization signal. Device.