KR100966550B1 - Digital TV receiver and symbol clock recovery device - Google Patents

Abstract

The present invention relates to a digital TV receiver and a symbol clock recovery apparatus, and more particularly, to convert a signal of a VSB digital baseband real component and an imaginary component into a signal of a real component and an imaginary component of an OQAM method, respectively, by high pass filtering, squared, and adding In addition, by removing the region in which data other than the frequency used by the symbol clock recovery unit exists, accurate symbol clock recovery can be performed even in the presence of severe multipath noise on the transmission channel. In addition, by determining the magnitude of the signal input to the prefilter and controlling the magnitude of the signal input to the prefilter to be constant at all times, the ghost is present on the transmission channel so that the signal does not exist at the frequency used by the symbol clock recovery unit. Accurate symbol clock recovery can be performed even when none is present.

Symbol Clock, VSB, OQAM, Gain

Description

Digital TV receiver and symbol clock recovery device

1 is a block diagram of a general digital TV receiver

FIG. 2 is a block diagram illustrating a general configuration of the carrier recovery unit of FIG. 1.

3A is a diagram illustrating frequency characteristics of a pre-filter of a symbol clock recovery unit in a case where there is no noise due to multipath;

3B is a diagram illustrating frequency characteristics of a pre-filter of a symbol clock recovery unit in case of noise due to multipath;

4 is a block diagram of a digital TV receiver according to a first embodiment of the present invention;

5 is a diagram illustrating frequency characteristics of an output signal of the adder of FIG.

6 is a block diagram illustrating a digital TV receiver according to a second embodiment of the present invention.

7 is a diagram illustrating frequency characteristics of a band pass filter to be used instead of the high pass filter of FIGS. 4 and 6.

8 is a block diagram illustrating a digital TV receiver of the present invention for performing symbol clock recovery using a band pass filter having the frequency characteristic of FIG.

Explanation of symbols for main parts of the drawings

104: A / D converter 105: phase separator                 

106: carrier recovery unit 201: resampling unit

202: fixed oscillator 400: symbol clock recovery unit

401: OQAM converter 402: high pass filter

403,404: Squarer 405: Adder

406: gain adjustment unit 407: DC calculation unit

408: Pre filter 408: Gardner phase error detection unit

410 loop filter 411 NCO

802: Bandpass Filter

The present invention relates to a digital TV receiver, and more particularly, to a symbol clock recovery apparatus for recovering a symbol clock from received data.

Currently, the ATSC (Advanced Television Systems Committee) 8 VSB (Vestigial Side Band) transmission system, which has been proposed for most digital transmission systems and digital TV transmission systems for the United States, carries only data in a transmission signal to improve frequency efficiency. That is, the receiver does not transmit information about the clock necessary for data recovery. Therefore, the receiving side should generate the same clock as used at the time of transmission to recover these data among the received signals in which only data exists. The part performing this role is a symbol clock recovery unit.                         

FIG. 1 is a block diagram illustrating a typical digital TV receiver including a symbol clock recovery unit. When a RF (Radio Frequency) signal modulated in a VSB manner is received through an antenna 101, the tuner 102 selects a specific channel desired by a user. After only the frequency is selected, the VSB signal of the RF band carried on the selected channel frequency is converted into a first intermediate frequency (IF) band and output to the analog processor 103. The analog processor 103 controls passband filtering and gain on the first IF signal output from the tuner 102 to convert the first IF signal into a second IF signal, thereby converting the A / D converter 104 into a second IF signal. Will output The A / D converter 104 digitizes the second IF signal and outputs it to the phase separator 105.

 The phase separator 105 separates the digital signal into a passband signal having a real component and an imaginary component whose phases are -90 ° to each other, and outputs the digital signal to the carrier recovery unit 106. Here, for convenience of explanation, the real component signal output from the phase separator 105 is called an I signal, and the imaginary component signal is called a Q signal.

The carrier recovery unit 106 transitions the I, Q passband digital signal output from the phase separator 105 into an I, Q baseband digital signal and outputs the symbol clock recovery unit 107 for symbol clock recovery. At the same time, the data is output to the digital processing unit 108 that performs channel equalization, phase tracking, error correction, and the like for actual data recovery.

2 is a general block diagram of the carrier recovery unit 106, and uses a frequency phase locked loop (FPLL). That is, the carrier recovery unit 106 composed of the FPLL demodulates the pass band I, Q signals output from the A / D converter 105 into baseband I, Q signals to lock frequencies and phases.                         

Referring to FIG. 2, the I, Q signals of the passband digitized through the A / D converter 104 and the phase splitter 105 are input to the complex multiplier 201 of the carrier recovery unit 106. do.

At this time, the signal r (t) of the real component (real) and the signal i (t) of the imaginary component (imaginary) output from the phase separator 105 is represented by Equation 1 below.

는 입력되는 신호에 존재하는 반송파 신호의 위상이다. Q(t)는 I(t) 신호의 직교 신호 성분이다. Here, I (t) is a data signal before modulation and p is a pilot signal inserted by a transmitter for carrier recovery. In addition, w _c is the frequency of the carrier signal present in the input signal,

Is the phase of the carrier signal present in the input signal. Q (t) is the orthogonal signal component of the I (t) signal.

On the other hand, the complex multiplier 201 of the carrier recovery unit 106 multiplies the passband I, Q signal as shown in Equation 1 by the reference carrier signal (NCOI, NCOQ) output from the NCO 205 to the passband The I and Q signals are converted into baseband I and Q signals I '(t) and Q' (t) as shown in Equation 2 below.

는 수신단에서 발생하는 기준 반송파 신호(NCOI,NCOQ)와 송신단에서 사용된 반송파 신호(w_c)의 주파수 오차(beat frequency) 성분이다. here,

Is a frequency error component of the reference carrier signals NCOI and NCOQ generated at the receiver and the carrier signal w _c used at the transmitter.

The baseband I and Q signals are output to the low pass filter 202 and to the symbol clock recovery unit 107 and the digital processing unit 108.

The low pass filter 202 performs low pass filtering on the baseband I and Q signals, extracts only the carrier portion, and outputs the carrier portion to the error detector 203. That is, since the carrier recovery unit 106 for recovering a carrier needs only a signal around a frequency at which a pilot frequency p exists among a bandwidth of 6 MHz, the low pass filter 202 has a remaining frequency component in which data components exist. Is removed from the I and Q signals to prevent the performance of the carrier recovery unit from being degraded by the data.

The error detector 203 detects the residual error of the carrier from the carrier signal and outputs the residual error to the low pass filter 204. That is, the residual error of the carrier detected by the error detector 203 is output to the NCO 205 via the low pass filter 204 to prevent instantaneous false detection. The NCO 205 generates a new reference carrier signal (NCOI, NCOQ) from the output of the low pass filter 204 and outputs it to the complex multiplier 201.

및

는 모두 '0'이 되어, 상기 수학식 2는 하기의 수학식 3과 같이 된다. If carrier recovery is completely performed in the carrier recovery unit 106,

And

Are all '0', and Equation 2 is as in Equation 3 below.

Then, the symbol clock recovery unit 107 performs symbol clock recovery from the signal of Equation 3 to generate a symbol clock used in all digital regions of the receiver.

와

의 영향을 받아 정상적인 심볼 클럭의 복구가 어렵게 된다.However, if carrier recovery is not completely performed in the carrier recovery unit 106, the symbol clock recovery unit 107 recovers the symbol clock from the signal as shown in Equation 2, and thus the carrier signal used in the transmitter and Frequency and phase error between the reference carrier signal generated by the receiver

Wow

Under the influence of, it is difficult to recover the normal symbol clock.

That is, in the structure in which the carrier recovery unit and the symbol clock recovery unit are sequentially connected as shown in FIG. 1, since the performance of the carrier recovery unit greatly affects the performance of the symbol timing recovery unit, the symbol clock recovery unit is not completely removed from the carrier recovery unit. It is affected by the residual frequency and phase error flowing in, which adversely affects the performance of the entire symbol clock recovery unit.

This is because the symbol clock recovery unit is usually located after the carrier recovery unit because the symbol clock recovery unit is designed on the assumption that the role of the carrier recovery unit is already completed. Therefore, recovery of the symbol clock also becomes impossible if carrier recovery is not completed.

Therefore, the applicant of the present invention to solve this problem, a patent application in Korea to recover the symbol clock irrespective of the residual carrier phase error of the carrier recovery unit patent application (application number: P02-041001, application date: 2002.07.13) I've done it.

However, in the case of the patent application described above, when there are severe multipath noises (ghosts) on the transmission channel, the signal of the frequency band used for symbol clock recovery becomes very small, so that the influence of the data present in the surrounding frequency is reduced. It may not work properly. 3A shows frequency characteristics of an adder output signal and a prefilter after a squarer in the absence of noise. 3b is a characteristic of the frequency and prefilters when the delay of multipath noise on the transmission channel is one symbol, the magnitude is equal to the original signal, and the phase is in phase (0 °).

In FIG. 3A, information exists in a frequency band used by a symbol clock recovery unit, and its size is also large so that a symbol clock recovery may be performed even if a signal exists in a neighboring frequency band. However, when there is almost no information in the frequency band used as shown in FIG. 3B, the influence of information of the surrounding frequency band, that is, the data, becomes relatively large, which hinders symbol clock recovery and degrades performance.

An object of the present invention is to supplement the above-described patent application, by effectively attenuating the frequency signal around the information used by the symbol clock recovery unit while maintaining a constant magnitude of the frequency used for symbol clock recovery at all times. In addition, the present invention provides a digital TV receiver and a symbol clock recovery apparatus that accurately perform symbol clock recovery even in the presence of severe multipath noise on a transmission channel.

A digital TV receiver according to a first embodiment of the present invention for achieving the above object, A / D for sampling the analog passband signal of the VSB method at a fixed frequency generated by a fixed oscillator and converting it into a digital passband signal A carrier recovery unit for multiplying the VSB digital passband signal by a reference carrier signal generated through a carrier recovery process and converting it into a VSB digital baseband signal, a VSB digital baseband real component output from the carrier recovery unit; A resampling unit which resamples an imaginary component signal at a frequency of twice the symbol clock and interpolates respectively, and a VSB digital baseband real component and an imaginary component signal interpolated and output from the resampling unit by an OQAM real number component. Transformed into imaginary and imaginary components, high pass filtered, squared, and added, Pre-filtering by adjusting the gain to be constant at all times, and generating a frequency of twice the symbol clock corrected from the timing error information detected from the pre-filtered signal and outputting the frequency to the resampling unit. It is done.

A digital TV receiver according to a second embodiment of the present invention includes an A / D converter for sampling a VSB analog passband signal at twice the symbol clock frequency and converting the signal into a VSB digital passband signal, and the VSB digital passband signal. A carrier recovery unit for multiplying a reference carrier signal generated by a carrier recovery process to a VSB digital baseband signal, and a real component of an OQAM method using a VSB digital baseband real component and an imaginary component signal output from the carrier recovery unit. After converting and imaginary components, high pass filtering and squared are added, pre-filtering by adjusting gain so that the added signal is always constant, and double corrected from timing error information detected from pre-filtered signal. Comprising a symbol clock recovery unit for generating a frequency of the symbol clock and output to the A / D converter It is characterized by.

An apparatus for recovering a symbol clock according to the present invention includes an OQAM converter for converting a signal of a VSB digital baseband real component and an imaginary component into a signal of an OQAM real component and an imaginary component, and an OQAM real component output from the OQAM converter. The high pass filter removes the information of the data interval by high pass filtering the signals of the imaginary component and the signal of the imaginary component, and squares the signals of the OQAM real component and the OQAM imaginary component, respectively, filtered and output from the high pass filter. A square arithmetic unit for outputting the result, a gain adjusting unit for adjusting the gain of the square arithmetic unit according to the input DC value, so that the magnitude of the output signal of the square arithmetic unit is constant, and an impulse magnitude of the signal output from the gain adjusting unit. A DC calculator for determining a value and outputting the determined result as a DC value to the gain adjuster; A pre-filter for passing only a frequency of a specific band for symbol clock recovery from a signal output from a signal, a phase error detector for detecting information on timing error from an output of the pre-filter, and timing error information output from the phase error detector. Filtering only the middle low-band signal component, and generates a frequency of the newly corrected double symbol clock according to the low-band component of the filtered timing error information, characterized in that it is composed of a NCO.

The OQAM converter uses a band pass filter instead of the high pass filter to remove information of the data section by band pass filtering the signals of the real and imaginary components of the OQAM, respectively.

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, with reference to the accompanying drawings illustrating the configuration and operation of the embodiment of the present invention, the configuration and operation of the present invention shown in the drawings and described by it will be described as at least one embodiment, By the technical spirit of the present invention described above and its core configuration and operation is not limited.

In other words, if the squared real signal and the imaginary signal are squared and added to the prefilter to recover the symbol clock unaffected by the carrier recovery unit, the difference between the real signal and the imaginary signal (the square of the squares) is added to each other. Same as Therefore, as shown in FIG. 3A, when the input signal has no noise, the frequency used by the symbol clock recovery unit is always the same. This is because there is an automatic gain adjuster at the receiving end that always makes the magnitude of the input signal constant. However, when ghost noise due to multiple paths exists on a transmission channel, even if a signal with automatic gain control is input, the magnitude of the frequency used by the symbol clock recovery unit is changed according to the characteristics of the ghost noise.

Therefore, the output of the pre-filter of the symbol clock recovery unit changes in size depending on the ghost, and thus the performance of the symbol clock recovery unit is deteriorated.

That is, when the high pass filter is used in the present invention, since the magnitude of the signal input to the prefilter is changed by the ghost present on the transmission channel, the magnitude of the prefilter input signal is determined, and the prefilter is adjusted by gain adjustment. It is a feature of the present invention to improve the performance of symbol clock recovery by modifying the signal input to the same magnitude all the time.

Fig. 4 is a block diagram showing the configuration of the digital TV receiver according to the first embodiment of the present invention. Only the configuration of the symbol clock recovery unit will be described.

The symbol clock recovery unit 400 converts the real component signal and the imaginary component signal of the VSB transmission method outputted from the resampler 201 into the real component signal and the imaginary component signal of the Offset QAM (OQAM) transmission method. An OQAM transforming unit 401 for converting, a high pass filter 402 for high pass filtering the I and Q signals of the OQAM component, and an OQAM real component output from the high pass filter 402, the square of which is squared. A first squarer 403, a second squarer 404 that squares the signal of the OQAM imaginary component, an adder 405 that adds the outputs of the first and second squarers 403, 404, an impulse present in DC The gain adjusting unit 406 adjusts the gain of the output signal of the adder 405 by using the magnitude of the signal, and detects the magnitude of the impulse signal present in the DC from the signal output from the gain adjusting unit 406. DC calculation unit 407 to output to (406) The preliminary filter 408 passing only the edge portion of the output spectrum from the signal output from the gain adjusting unit 406 and the gardner outputting information on the timing error from the signal passed through the prefilter 408. Output frequency according to a phase error detector 409, a loop filter 410 for filtering only low-band signal components among the timing error information output from the Gardner phase error detector 409, and a low-band component of the timing error information. The NCO 411 converts the sampling timing of the resample unit 201.

In the first embodiment of the present invention configured as described above, the A / D converter 104 oscillates from the fixed oscillator at a fixed frequency (that is, the fixed frequency is different from the frequency of the symbol clock and is usually 25 MHz). This is the case of sampling and digitizing. That is, the data sampled at 21.52 MHz, which is twice the symbol clock frequency fs, is transmitted from the transmitting side, but the data output from the A / D converter 104 is digital data sampled at 25 MHz.

At this time, the fixed frequency oscillated by the fixed oscillator 202 is higher than twice the symbol frequency (2fs) and can not be adjusted so that the resampling unit 201 between the carrier recovery unit 106 and the symbol clock recovery unit 400. To place.

The resampler 201 samples and outputs the digital baseband signal at twice the symbol clock frequency 2fs, that is, 21.52 MHz, for symbol clock recovery. The resampling unit 201 basically changes the sampling rate. That is, since the data sampled at 21.52 MHz and received at 25 MHz is output by the A / D converter 104 at 25 MHz, the resampler 201 is again sampled at twice the symbol clock frequency, that is, 21.52 MHz. Will print.                     

To this end, the resampling unit 201 doubles the baseband digital signal output through the A / D converter 104 and the carrier recovery unit 106 using the output frequency of the symbol clock recovery unit 400. The interpolated digital signal is synchronized with the symbol clock frequency, and is outputted to the symbol clock recovery unit 107 and output to the digital processing unit 108 for channel equalization, phase tracking, error correction, and the like.

The symbol clock recovery unit 400 obtains a timing error of current symbols, generates a frequency proportional to the timing error, and outputs the frequency to the resampling unit 201.

That is, the OQAM converter 401 of the symbol clock recovery unit 400 applies a center frequency of 2.690559 MHz to a VSB I, Q signal that is resampled at 21.52 MHz and output from the resampler 201. The baseband VSB I, Q signals are multiplied by a fixed oscillation frequency, and output to the high pass filter 402 by converting the baseband VSB I, Q signals into OQAM I, Q signals.

The high pass filter 402 removes the information of the data interval from the OQAM I, Q signal and outputs the first and second squarers 403 and 404.

The first and second squarers 403 and 404 square the OQAM I and OQAM Q signals, respectively, and output the squared OQAM I and OQAM Q signals. The adder 405 adds the squared OQAM I and OQAM Q signals to adjust the gain. )

In this case, when the OQAM I and OQAM Q signals passing through the high pass filter 402 are squared by the first and second squarers 403 and 404, respectively, and then added by the adder 405, the output signal of the adder 405 The characteristics are as shown in FIG.

That is, due to the frequency characteristics of the first and second squarers 403 and 404, the signal existing in the fs / 4 frequency of FIG. 5 is changed to the fs / 2 frequency and DC (direct current, 0). There is a large impulse signal. At this time, the magnitude of the impulse signal present in the DC, that is, the DC value is equal to the magnitude of the power of the signal before squared. If the magnitude of the output signal of the high pass filter 402 of FIG. 4 increases due to the ghost present on the transmission channel, the magnitude of the impulse signal present in the DC of FIG. Also decreases in size.

Accordingly, the DC calculator 407 of the present invention determines the magnitude of the impulse signal input to the prefilter 408 by using such a characteristic, and converts the determined magnitude of the impulse signal, that is, the DC value, into the gain adjuster 406. Output

The gain adjusting unit 406 adjusts the gain of the signal input to the prefilter 408 from the determined magnitude of the impulse signal so that a signal having a constant magnitude is always input to the prefilter 408. In other words, the gain adjusting unit 406 always inputs a signal having a constant gain to the prefilter 408.

The prefilter 408 passes only the edge portion of the spectrum where the gain is adjusted by the gain adjusting unit 406 to obtain timing information from an input signal having the same size at all times, and outputs the signal to the Gardner phase error detector 409. . The Gardner phase error detector 409 multiplies the difference value of two adjacent symbol samples by one intermediate sample value to obtain information on the timing error and outputs the information on the timing error to the loop filter 410. The loop filter 410 filters only low-band signal components of the timing error information extracted by the Gardner phase error detector 409 and outputs the low-band signal component to the NCO 411. The NCO 411 adjusts the sampling timing of the resample unit 201 by converting an output frequency according to the low band component of the timing error information.

6 is a block diagram of a digital TV receiver according to a second embodiment of the present invention. The operation and configuration of the symbol clock recovery unit 600 are the same as those of FIG. 4 described above, but the A / D converter 104 is used instead. The embodiment of the present invention relates to a case where the frequency of the clock inputted as is 2 times the symbol clock frequency (2fs) rather than the fixed frequency. In the case of FIG. 6, since the A / D converter 104 samples the second IF signal at twice the symbol clock frequency 2fs and converts the second IF signal into a digital passband signal, the carrier recovery unit 106 and the symbol clock recovery unit ( There is no need for resampling between 600). Therefore, the hardware burden can be reduced by that amount.

That is, the output of the loop filter 610 for low pass filtering the timing error information of the current symbol detected by the symbol clock recovery unit 600 is a variable oscillator generating a new double symbol clock frequency 2fs. oscillator 611, and the variable oscillator 611 generates a newly generated double symbol clock frequency 2fs from the low pass filtered timing error information and outputs it to the A / D converter 104. .

At this time, if there is no high pass filter in the symbol clock recovery units of the first and second embodiments of the present invention, the role of the OQAM converter is not necessary at all. This is because the outputs of the two squarers and the adder transform the signal into the signal as shown in FIG. 3 even though the input signal is not necessarily the baseband signal. However, when the high pass filter is used in front of the two squarers, most of the frequency region in which data is present is removed, and only the components necessary for the symbol clock recovery are input to the square, which improves the residual jitter characteristic of the symbol clock recovery unit. In addition, even if there is severe multipath noise on the transmission channel, the performance of the symbol clock recovery unit is improved because it is not disturbed by data operation.

On the other hand, the high pass filter used in the first and second embodiments of the present invention can recover the symbol clock even if a band pass filter having a frequency characteristic as shown in FIG. 7 is used.

FIG. 8 illustrates an embodiment in which the band pass filter 802 is used instead of the high pass filter of the symbol clock recovery unit in the first embodiment of the present invention as shown in FIG. 4.

In FIG. 8, the roles and operations of the blocks except for the band pass filter 802 are the same as those of FIG. 4, and when the frequency characteristics of the band pass filter 802 are set as shown in FIG. 7, the OQAM converter 801 Information of the data section is removed from the output, and only the frequency part used by the symbol clock recovery unit 800 is passed.

Meanwhile, as another embodiment of the present invention, the digital TV receiver performing A / D conversion using the variable oscillator as shown in FIG. 6 has the frequency characteristics as shown in FIG. 7 instead of the high pass filter of the symbol clock recovery unit. A band pass filter can be used instead to perform symbol clock recovery.

As described above, the present invention removes an area in which data other than the frequency used by the symbol clock recovery unit using an OQAM converter and a high pass filter (or a band pass filter), and uses a gain adjuster and a DC calculation unit as a prefilter. By controlling the size of the input signal to be constant at all times, even if there is no ghost on the transmission channel because there is no signal at the frequency used by the symbol clock recovery unit, symbol clock recovery is possible, thereby maximizing the performance of the receiver.

The present invention is applicable to all terrestrial digital broadcast receivers of the ATSC method using VSB modulation.

As described above, according to the digital TV receiver and the symbol clock recovery apparatus according to the present invention, a VSB digital baseband real component and an imaginary component are converted into signals of a real component and an imaginary component of the OQAM method, respectively, for high pass filtering and squared. In addition, by removing the region in which data other than the frequency used by the symbol clock recovery unit exists, accurate symbol clock recovery can be performed even in the presence of severe multipath noise on the transmission channel.

In addition, by determining the magnitude of the signal input to the prefilter and controlling the magnitude of the signal input to the prefilter to be constant at all times, the ghost is present on the transmission channel so that the signal does not exist at the frequency used by the symbol clock recovery unit. Accurate symbol clock recovery can be performed even when none is present.

Therefore, the symbol clock recovery unit of the present invention can operate without receiving the residual carrier components, and at the same time, it can perform accurate symbol clock recovery even in the presence of severe multipath noise on the transmission channel. It can also improve the performance of the entire system.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (10)

An A / D conversion unit for sampling the analog passband signal of the VSB method at a fixed frequency generated by the fixed oscillator and converting the analog passband signal into a digital passband signal; A carrier recovery unit multiplying the VSB digital passband signal by a reference carrier signal generated through a carrier recovery process to convert the VSB digital baseband signal into a VSB digital baseband signal; A resampler for resampling the VSB digital baseband real component and the imaginary component signal output from the carrier recovery unit at twice the frequency of the symbol clock; And The VSB digital baseband real component and imaginary component signals interpolated and output from the resampler are converted into signals of the real component and the imaginary component of the OQAM method, respectively, high pass filtered, squared, and added, and the magnitude of the added signal is always Pre-filtering by adjusting the gain to be constant, and generating a frequency of a double symbol clock corrected from the timing error information detected from the pre-filtered signal and outputting the frequency to the resampler. Digital TV receiver. The method of claim 1, wherein the symbol clock recovery unit An OQAM conversion unit for converting the VSB digital baseband real component signal and the imaginary component signal interpolated and output from the resampler into an OQAM real component signal and an imaginary component signal; A high pass filter which removes information of a data section by high pass filtering the signals of the real component and the imaginary component of the OQAM signal output from the OQAM converter; A square arithmetic unit for squaring the signals of the OQAM real component and the signal of the OQAM imaginary component which are filtered and output from the high pass filter, and outputting the squared result; A gain adjusting unit adjusting the gain of the square calculating unit according to the input DC value so that the magnitude of the output signal of the square calculating unit is constant; A DC calculator for determining an impulse magnitude of the signal output from the gain adjuster and outputting the determined result as a DC value to the gain adjuster; A pre-filter for passing only frequencies of a specific band for symbol clock recovery from the signal output from the gain adjuster; A phase error detector for detecting information on timing error from an output of the prefilter; And A filter for filtering only low-band signal components of the timing error information output from the phase error detection unit, generating a frequency of a newly corrected double symbol clock according to the low-band components of the filtered timing error information, and outputting the frequency to the resampler; Digital TV receiver, characterized in that consisting of NCO. The method of claim 1, The OQAM conversion unit multiplies the signal of the VSB digital baseband real component and the imaginary component signal interpolated and output from the resampler by a fixed oscillation frequency having a center frequency of 2.690559 MHz to obtain a signal of the OQAM real component. A digital TV receiver characterized by converting into an imaginary component signal. An A / D converter configured to sample the VSB analog passband signal at twice the symbol clock frequency and convert the VSB analog passband signal into a VSB digital passband signal; A carrier recovery unit multiplying the VSB digital passband signal by a reference carrier signal generated through a carrier recovery process to convert the VSB digital baseband signal into a VSB digital baseband signal; And VSB digital baseband real and imaginary component signals outputted from the carrier recovery unit are converted into real and imaginary component signals of the OQAM method, high pass filtered, squared, and added, so that the magnitude of the added signal is always constant. Pre-filtering by adjusting the gain, and generating a frequency of a double symbol clock corrected from the timing error information detected from the pre-filtered signal and outputting the frequency to the A / D converter. Digital TV receiver. The method of claim 4, wherein The symbol clock recovery unit, An OQAM converter for converting a signal of a VSB digital baseband real component and an imaginary component output from the carrier recovery unit into a signal of an OQAM real component and an imaginary component; A high pass filter which removes information of a data section by high pass filtering the signals of the real component and the imaginary component of the OQAM signal output from the OQAM converter; A square arithmetic unit for squaring the signals of the OQAM real component and the signal of the OQAM imaginary component which are filtered and output from the high pass filter, and outputting the squared result; A gain adjusting unit adjusting the gain of the square calculating unit according to the input DC value so that the magnitude of the output signal of the square calculating unit is constant; A DC calculator for determining an impulse magnitude of the signal output from the gain adjuster and outputting the determined result as a DC value to the gain adjuster; A pre-filter for passing only frequencies of a specific band for symbol clock recovery from the signal output from the gain adjuster; A phase error detector for detecting information on timing error from an output of the prefilter; And Filtering only low-band signal components of the timing error information output from the phase error detection unit, generating a frequency of a newly corrected double symbol clock according to the low-band components of the filtered timing error information, and outputting the frequency to the A / D converter. Digital TV receiver, characterized in that consisting of a filter and NCO. The method of claim 5, The OQAM conversion unit multiplies the signal of the VSB digital baseband real component and the imaginary component signal interpolated and output from the carrier recovery unit by a fixed oscillation frequency having a center frequency of 2.690559 MHz to obtain a signal of the OQAM real component. A digital TV receiver characterized by converting into an imaginary component signal. An OQAM conversion unit for converting a signal of a residual sideband (VSB) digital baseband real component and an imaginary component into a signal of an OQAM real component and an imaginary component; A square arithmetic unit for squaring and adding the signals of the OQAM real component and the signal of the OQAM imaginary component respectively output from the OQAM converter and outputting the result; A gain adjusting unit adjusting the gain of the square calculating unit according to the input DC value so that the magnitude of the output signal of the square calculating unit is constant; A DC calculator for determining an impulse magnitude of the signal output from the gain adjuster and outputting the determined result as a DC value to the gain adjuster; A phase error detector which passes only a frequency of a specific band for symbol clock recovery from the signal output from the gain adjuster and detects information on a timing error; And Filtering only the low-band signal components of the timing error information output from the phase error detector, and a filter for generating a frequency of the newly corrected double symbol clock according to the low-band components of the filtered timing error information and NCO Symbol clock recovery device. The method of claim 7, wherein And a high pass filter between the OQAM converter and the square arithmetic unit to remove information of the data interval by high pass filtering the signals of the real component and the imaginary component output from the OQAM converter, respectively. Symbol Clock Recovery Device. The method of claim 7, wherein And a band pass filter between the OQAM converter and the square operator to remove information of the data section by band pass filtering the signals of the real component and the imaginary component respectively output from the OQAM converter. Symbol Clock Recovery Device. The method of claim 7, wherein The OQAM conversion unit multiplies the VSB digital baseband real component signal and the imaginary component signal by a fixed oscillation frequency having a center frequency of 2.690559 MHz to convert the OQAM real component signal and the imaginary component signal. Symbol clock recovery device characterized in that.

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