CN100499755C - Unit for recovering symbol clock in digital TV - Google Patents
Unit for recovering symbol clock in digital TV Download PDFInfo
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- CN100499755C CN100499755C CNB2003101190325A CN200310119032A CN100499755C CN 100499755 C CN100499755 C CN 100499755C CN B2003101190325 A CNB2003101190325 A CN B2003101190325A CN 200310119032 A CN200310119032 A CN 200310119032A CN 100499755 C CN100499755 C CN 100499755C
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Abstract
The invention is related to unit for recovering symbol clock in digital TV. Especially, when component of residual carrier wave is not cleaned out from carrier wave recovery section completely, using two pieces of squarers and accumulators can clean out residual carrier wave. Squaring outputs from accumulators also can generate signal of new fs/2 portion to recover symbol clock even if there is no signal of fs/2 frequency portion in synchronizing signal generated caused by double image. Thus, symbol clock can be recovered correctly and safely no matter in situations: unfulfilled recovered carrier wave or no fs/2 frequency caused by double image. The invention improves performance of algorithm for recovering symbol clock, and integrity of system.
Description
Technical field
The present invention is relevant with Digital Television TV receiver, is particularly recovered a relevant invention of symbol clock recovery device of symbol clock by received data.
Background technology
Current, most of digital transmission system is in the residual sideband ATSC of the advanced television standard committee (Advanced Television Systems Committee) 8VSB (the Vestigial Side Band) transfer system with U.S.'s digital delivery pattern motion, for improving frequency efficiency, the transmission signal is only loaded numeral transmit.That is, not transmitting receiving terminal is the necessary clock information of restore data.And, be these data of recovery, the same clock that uses in the time of must producing as transmission in the digital signal in only existing of receiving terminal reception.The part of finishing these functions is a symbol clock recovery portion.
Fig. 1 is the formation block diagram with general Digital Television TV receiver of this symbol clock recovery portion.By the tuner 102 of antenna 101 receptions, only select the desirable special modality frequency of user with radio frequency (Radio Frequency) signal of residual sideband VSB pattern modulation; The residual sideband VSB signal transformation that to load radio frequency (RF) frequency band in the selected channel frequence then is the 1st intermediate frequency (IF) frequency band, and it is outputed to analog portion 103.Analog portion 103 carries out the control of passband filtering and amplification etc. to the 1st intermediate frequency (IF) signal of tuner 102 output, is the 2nd intermediate frequency (IF) signal with the 1st intermediate frequency (IF) signal transformation, and it is outputed to analog/digital A/D converter section 104.Analog/digital A/D converter section 104 is sampled the 2nd intermediate frequency (IF) signal with fixed frequency (fixed frequency is different with the symbol clock frequency, is generally 25MHz), and it is outputed to phase separator 105.That is, in the data of transmission end transmission with 2 times 21.52MHz frequency sampling of symbol clock frequency (fs); And and be numerical data in the data of analog/digital A/D converter section 104 output with the 25MHz frequency sampling.
Carrier wave recovery section 106 is with the I of phase separator 105 outputs, the digital signal that Q passband digital signal is converted to I, Q base band, and the signal rows conversion that has recovered for symbol then outputs to resampling portion (Re sampler) 107 with it.
Resampling portion 107 works to change sampling rate basically.That is, will be with the reception data of 21.52MHz frequency sampling, be transformed to the 25MHz frequency sampling at analog/digital A/D converter section 104 and export; And in resampling portion 107 again with 2 times of symbol clock frequencies, that is, and 21.52MHz frequency sampling output.
For this reason, resampling portion 107 will be through the baseband digital signal of analog/digital A/D converter section 104 and 106 outputs of carrier wave recovery section, utilize the output frequency of symbol clock recovery portion 108, to be carried out interpolation by synchronous digital signal with 2 times of symbol clock frequencies, and when it is outputed to symbol clock recovery portion 108, for channel-equalization, Phase Tracking, error correction etc. output to digital processes 109.
Symbol clock recovery portion 108 obtains the synchronous error of current sign, produces with the proportional frequency of synchronous error then and outputs to resampling portion 107.
Fig. 2 is the general formation block diagram as above-mentioned carrier wave recovery section 106, uses to be called frequency phase lock ring FPLL (Frequency Phase Locked Loop).That is, the carrier wave recovery section 106 that constitutes with frequency phase lock ring FPLL is demodulated into baseband I, Q signal with passband I, the Q signal of analog/digital A/D converter section 104 outputs, and with this semaphore lock frequency and phase place.
105, passband I, the Q signal that is digitized is input to the complex multiplier 201 of carrier wave recovery section 106.
At this moment, from real number composition (real) the signal r (t) and imaginary number composition (imaginary) the signal i (t) of phase separator 105 output, identical with following mathematical expression 1.
[mathematical expression 1]
r(t)＝{I(t)+P}cos(w
ct+ψ)—Q(t)sin(w
ct+ψ)
i(t)＝{I(t)+P}sin(w
ct+ψ)+Q(t)cos(w
ct+ψ)
Here, I (t) is modulation (modulation) data-signal before; P is master control (pilot) signal that inserts in transport unit for the carrier wave recovery.And, w
cFrequency for the carrier signal that in input signal, exists; ψ is the phase place of the carrier signal that exists in input signal.Q (t) is the orthogonal signalling composition of I (t) signal.
On the one hand, the complex multiplier 201 of carrier wave recovery section 106, passband I, Q signal as above-mentioned mathematical expression 1 be multiply by the reference carrier signal of numerically-controlled oscillator NCO 205 output, and (the numerically-controlled oscillator real number becomes sub-signal NCOI, the numerically-controlled oscillator imaginary number becomes sub-signal NCOQ), and above-mentioned passband I, Q signal be transformed to baseband I, Q signal I as following mathematical expression 2
1(t), Q
1(t).
[mathematical expression 2]
I
1(t)＝{I(t)+P}cos(△w
ct+ψ)—Q(t)sin(△w
ct+ψ)
Q
1(t)＝{I(t)+P}sin(△w
ct+ψ)+Q(t)cos(△w
ct+ψ)
Here, △ w
cBe reference carrier signal (the numerically-controlled oscillator real number becomes sub-signal NCOI, and the numerically-controlled oscillator imaginary number becomes sub-signal NCOQ) that produces at receiving terminal and the carrier signal (w that uses at transmitting terminal
c) frequency error (beat frequency) composition.
When baseband I, Q signal output to low pass filter 202, output to symbol clock recovery portion 108 and digital processes 109 through resampling portion 107.
Error-detecting portion 203 is the detected carrier residual error from carrier signal, and it is outputed to low pass filter 204.That is, survey, output to numerically-controlled oscillator NCO 205 through low pass filter 204 for the flase drop of moment of the carrier residual error that prevents to detect from error-detecting portion 203.Numerically-controlled oscillator NCO 205 will output to complex multiplier 201 from the new reference carrier signal (numerically-controlled oscillator real number composition NCOI, numerically-controlled oscillator imaginary number composition NCOQ) that low pass filter 204 outputs produce.
Recover if in carrier wave recovery section 106, be completed into carrier wave, then △ w
cAnd ψ is ' 0 ', and at this moment, it is identical with following mathematical expression 3 that above-mentioned mathematical expression 2 becomes.
[mathematical expression 3]
I
1(t)＝I(t)+P
Q
1(t)＝Q(t)
So, the signal of symbol clock recovery portion 108 usefulness mathematical expressions 3 carries out the recovery of symbol clock, and is created in the operable clock of all data fields of receiving terminal.
But, if not finishing carrier wave in carrier wave recovery section 106 recovers, then symbol clock recovery portion 108 is owing to use the recovery of carrying out symbol clock as the signal of above-mentioned mathematical expression 2, therefore, be subjected to frequency and phase error △ w between the reference carrier signal that the carrier signal used and receiving terminal produce in sending part
cWith the influence of ψ, thereby bring difficulty for normal symbol clock recovery.
Promptly, as shown in Figure 1, if carrier wave recovery section and symbol clock recovery portion connected structure in turn, then because carrier wave recovery section performance has bigger influence to the performance of symbol clock recovery portion, therefore, symbol clock recovery portion is subjected to not removing and flow to the next residual carrier frequency and the influence of phase error fully in the carrier wave recovery section, and this is to symbol clock recovery portion overall performance generation ill effect.
This is because symbol clock recovery portion is usually located at carrier wave recovery section rear end; And during design symbol clock recovery portion, be that the effect of supposition carrier wave recovery section is all finished to prerequisite design and caused.This shows, not recover that the then symbol clock recovery is to be difficult to realize if finish carrier wave.
Fig. 3 is the formation block diagram that comprises the Digital Television TV receiver of symbol clock recovery portion, as seen from the figure, utilizes two squarers 401,402 and accumulator 403 can eliminate because of not finishing carrier wave and recovers caused frequency and phase error.
That is, in carrier wave recovery section 303, because under the situation of not finishing the carrier wave recovery, the residual phase error also can be eliminated by the 1st, the 2nd squarer 401,402 and accumulator 403, therefore, in outputing to prefilter 404 signals, do not comprise the residual phase error.This residual phase error that just means symbol clock recovery portion 400 and 303 outputs of carrier wave recovery section irrespectively can be worked; Also mean simultaneously the recovery of more stable realization symbol clock.
Synchronous error test section 405 comes detected symbol clock synchronization error promptly, phase error by prefilter 404 outputs usually as the synchronous error test section of Gardner (name) pattern that adopts general Gardner (Gardner, name) pattern or correction.The synchronous error signal is input to numerically-controlled oscillator NCO 407 through low pass filter 406; And numerically-controlled oscillator NCO 407 produces the new twice symbol clock frequency that has compensated (2fs, fs are the symbol clock frequency) by the synchronous error signal of low-pass filtering, and it is outputed to resampling portion 304.
Fig. 4 represents that the synchronous error test section 405 of symbol clock recovery portion 400 is under the situation with correction Gardner (name) mode detection synchronous error, finish the frequency characteristic that the carrier wave recovery is input to real number composition (real) signal and the prefilter (pre-filter, band pass filter) of symbol clock recovery portion 400.
Usually, use is as the situation of the specification-residual sideband VSB (Vestigial side band) of the Digital Television TV transfer mode of the U.S. and Korea S modulation (modulation) pattern, and the recovery that 1/2 frequency (fs/2) signal that extracts symbol clock frequency (fs) by the frequency characteristic of real number signal carries out symbol clock utilizes the elemental motion of proofreading and correct Gardner (name) mode symbol clock recovery portion exactly.
That is, proofread and correct zero crossing (zero-crossing) characteristic that Gardner (name) synchronous error test section 405 utilizes data usually, so-called zero crossing characteristic is to have this information in two continuous nested places of symbol frequency spectrum from the angle of frequency spectrum; In other words, two above-mentioned continuous symbol spectrum overlapping parts, its frequency is near the fs/2 frequency; Obtain the needed information of synchronous error only on this position (the nested place of frequency spectrum) for utilizing in the data zero crossing characteristic of proofreading and correct the reception of Gardner (name) pattern.And, in symbol clock recovery portion 400,, that is,, use the prefilter 404 in screening frequency band path for obtaining needed zero cross signal in order in this part, more correctly to detect synchronous error.Therefore, frequency (fs/2) signal of extraction symbol clock frequency 1/2 is the main effect of prefilter 404.
The symbol clock recovery portion of Fig. 5 for not influenced by the carrier wave recovery section, sum signal frequency characteristic and the prefilter characteristic used for the phase error of detection Gardner (name) pattern after using squarer 401,402 and 403 pairs of real number (real) signals of accumulator and imaginary number (imaginary) signal separately square.
By Fig. 4 and Fig. 5 as seen, in being input to the signal of antenna, if there is not line noise, then since the frequency characteristic of finishing the real number signal under the situation that carrier wave recovers with to the frequency characteristic of sum signal after real number signal and the imaginary signal square much at one, therefore, even if the synchronous error test section of use Gardner (name) pattern also can regular event.
But in being input to symbol clock recovery portion 400 signals, if there is not frequency (fs/2) signal of symbol clock frequency 1/2, then the recovery of signal Synchronization is impossible realize.For example, if, then can not realize the recovery of symbol clock transmitting 1/2 frequency (fs/2) signal that there is heavier line noise in passage and does not have symbol frequency.
Fig. 6 is identical with the original signal size, and same-phase (in phase) line noise of correct 1 symbol of delay is in the frequency characteristic that transmits under the situation about existing on the passage.
Fig. 7 is that size is identical with original signal, and has each frequency characteristic signal under the situation of quadrature phase (quadrature) line noise of 2 symbols of correct delay.
By Fig. 6 and Fig. 7 as seen, there is not the situation of 1/2 frequency (fs/2) signal of symbol clock frequency fully.Can not realize the recovery of symbol clock in this case with correction Gardner (name) pattern.
Summary of the invention
The present invention proposes for solving above-mentioned existing problems, even if its objective is to provide in reasons such as ghost images causes under the situation of fs/2 frequency partial distortion of synchronizing signal, also can correctly recover the symbol clock device of the Digital Television TV receiver of symbol clock.
The symbol clock recovery device of Digital Television TV according to the present invention that puts forward for achieving the above object is by constituting with the lower part: will simulate the analog/digital A/D converter section that the passband signal is sampled with analog/digital A/D clock frequency and is converted into digital passband signal; To the reference carrier signal of digital passband signal times, and be converted into the carrier wave recovery section of digital baseband signal to produce by carrier wave recovery process; In comprising the Digital Television TV receiver of carrier wave recovery section, symbol clock recovery portion becomes sub-signal its result's of output operational part after the summed square separately with the real number composition of the digital baseband of carrier wave recovery section output with imaginary number; The squarer that square operation portion output is carried out square again; Recovery section when exporting symbol according to squarer; In comprising the Digital Television TV receiver of carrier wave recovery section, symbol clock recovery portion becomes sub-signal its result's of output operational part after the summed square separately with the real number composition of the digital baseband of carrier wave recovery section output with imaginary number; The squarer that square operation portion output is carried out square again; According near the prefilter that carries out filtering 1/2 frequency of squarer output to the symbol clock frequency; Two symbol sampler differences by prefilter multiply by a median sample value, and detect Gardner (name) the synchronous error test section of the relevant signal of synchronous error; In the synchronous error signal of Gardner (name) synchronous error test section output, only carry out the filtering of low band signal composition, and, produce new twice symbol clock frequency filtering and the oscillator that have compensated according to the synchronous error signal low band signal composition of filtering.
Operational part will become sub-signal with imaginary number to the digital passband real number composition of analog/digital A/D converter section output, separately its result of output after the summed square.
Operational part will be to the real number composition and the imaginary number composition of the digital baseband of carrier wave recovery section output, its result of output after its absolute value addition of respectively asking for.
Operational part will be to the digital passband real number composition and the imaginary number composition of analog/digital A/D converter section output, its result of output after its absolute value addition of respectively asking for.
If the analog/digital A/D clock frequency of analog/digital A/D converter section is a fixed frequency, then between carrier wave recovery section and symbol clock recovery portion, the real number composition that the digital baseband of exporting with the carrier wave recovery section is set becomes sub-signal also to carry out the resampling portion (promptly having a resampling portion) of interpolation separately with 2 times of clock frequency resamplings more with imaginary number; And 2 times of symbol clock frequencies that symbol clock recovery portion produces output to resampling portion.
Analog/digital A/D converter section uses 2 times of symbol clock frequencies that symbol clock recovery portion produces as analog/digital A/D clock frequency.
Advantage of the present invention is as above-mentioned, the Digital Television TV symbol clock recovery device according to the present invention, thus new information is carried out the recovery of symbol clock; Also can recover situation about finishing at carrier wave, perhaps still carry out correct symbol clock recovery restfully under the situation that 1/2 frequency (fs/2) information of reason symbol clock frequency such as ghost image does not have, therefore not only improve the symbol clock recovery algorithm performance, and can improve the entire system performance.
Description of drawings
Fig. 1 is that general Digital Television TV receiver constitutes block diagram.
Fig. 2 is the general pie graph in Fig. 1 carrier wave recovery section.
Fig. 3 constitutes block diagram at example of Fig. 1 symbol clock recovery portion.
Fig. 4 is the synchronous error test section in Fig. 1 symbol clock recovery portion, under with the situation of proofreading and correct Gardner (name) mode detection synchronous error, finishes the real number signal and the prefilter frequency characteristic figure that are input to symbol clock recovery portion after carrier wave recovers.
Fig. 5 is in Fig. 1 symbol clock recovery portion, to real number signal and the imaginary signal frequency characteristic signal of summed square and the prefilter performance plot that uses for Gardner (name) pattern phase error detection separately.
Fig. 6 is identical with the original signal size, and same-phase (in phase) line noise of correct 1 symbol of delay transmit under the situation about existing on the passage Fig. 1 symbol clock recovery portion real number signal frequency characteristic and to real number and the imaginary signal frequency characteristic of summed square signal separately, and the frequency characteristic figure of prefilter.
Fig. 7 is identical with the original signal size, and exist under the situation of quadrature phase (quadrature) noise of 2 symbols of correct delay Fig. 1 symbol clock recovery portion real number signal frequency characteristic and to real number and the imaginary signal frequency characteristic of summed square signal separately, and the frequency characteristic figure of prefilter.
Fig. 8 constitutes block diagram for the Digital Television TV receiver that has symbol clock recovery portion according to the present invention.
Fig. 9 is that signal magnitude is identical, and same-phase (in phase) line noise of correct 1 symbol of delay exists the output frequency characteristic of Fig. 8 symbol clock recovery portion accumulator under the situation and the output frequency characteristic of the 3rd squarer transmitting on the passage, and the output frequency characteristic figure of prefilter.
Symbol description to the drawing major part:
801: analog/digital A/D converter section; 802: phase separator;
803: the carrier wave recovery section; 804: resampling portion;
900: symbol clock recovery portion; 901,902,904: squarer;
903: accumulator; 905: prefilter;
906: proofread and correct Gardner (name) synchronous error test section;
907: low pass filter; 908: numerically-controlled oscillator NCO.
Embodiment
Other purposes of the present invention, feature and doubtful point etc. are appreciated that by the example explanation of reference accompanying drawing.
Below, with reference to accompanying drawing example formation of the present invention and effect thereof are described.Constitute and the example that acts at least more than one carries out according to the present invention that drawing is described, but because these explanation the technology of the present invention thoughts and its core constitute and act on restricted.
Fig. 8 is for constituting calcspar according to the Digital Television TV receiver that the present invention includes the symbol clock recovery device.The simulation passband conversion of signals that analog/digital A/D converter section 801 will be imported is digital passband signal, and it is outputed to phase separator 802.Phase separator 802 separates digital passband signal real number composition (I) and imaginary number composition (Q) signal, outputs to carrier wave recovery section 803 then.Carrier wave recovery section 803 pairs of digital passband I, Q signals multiply by reference carrier signal, and passband I, Q signal are converted to digital baseband I, Q signal, output to resampling portion 804 then.Resampling portion 804 will be with 2 times of symbol clock frequencies (2fs) of symbol clock recovery portion 900 output, to I, the Q signal of base band sample and the signal of interpolation output to symbol clock recovery portion 900.
Symbol clock recovery portion 900 is by constituting with the lower part: the 1st squarer 901 that becomes sub-signal (I ＂ (t)) to carry out square to the digital passband real number of resampling portion 804 output; The 2nd squarer 902 that becomes sub-signal (Q ＂ (t)) to carry out square to imaginary number; The accumulator 903 that two square values that the 1st, the 2nd squarer 901,902 is exported carry out addition; The 3rd squarer 904 that output is carried out square again to accumulator 903; Only allow prefilter 905 by the marginal portion of the 3rd squarer 904 output spectrums; Gardner (name) synchronous error test section 906 by the relevant signal of input synchronous error that passes through prefilter 905; In the synchronous error signal of proofreading and correct 906 outputs of Gardner (name) synchronous error test section, the low pass filter 907 of a filtering low band signal composition; And according to synchronous error signal low band signal composition, numerically-controlled oscillator NCO 908 formations that produce new 2 times of symbol clock frequencies (2fs) and the synchronized sampling of resampling portion 804 is regulated.
As the 1st squarer 901 of the symbol clock recovery of the present invention portion 900 of above-mentioned formation, the I signal (I ＂ (t)) of the output base band that resampling portion 804 has been interpolated carries out square; And 902 pairs of resampling portions 804 of the 2nd squarer the Q signal of the output base band of interpolation (Q ＂ (t)) carry out square, and it is outputed to accumulator 903.If in accumulator 903, two quadrature signal are carried out addition, then be transformed to I, the Q signal of the base band of eliminating the carrier wave composition.
At this moment, the input of the 1st, the 2nd squarer 901,902 { I ＂ (t), Q ＂ (t) } recovers if all finish carrier wave when representing with mathematical expression, and then the mathematical expression 3 with above-mentioned is identical; Do not recover action if finish carrier wave, then the mathematical expression 2 with above-mentioned is identical.
And, recover if all finish carrier wave, then the output of the 1st, the 2nd squarer 901,902 is identical with following mathematical expression 4.
[mathematical expression 4]
{I＂(t)}
2＝{I(t)+P}
2＝I
2(t)+P
2+2PI(t)
{Q＂(t)}
2＝Q
2(t)
Recover if finish carrier wave, then the output of the 1st, the 2nd squarer (901,902) is identical with following mathematical expression 5.
[mathematical expression 5]
{I＂(t)}
2＝[{I(t)+P}cos(△w
ct+ψ)—Q(t)sin(△w
ct+ψ)]
2
＝{I(t)+P}
2cos
2(△w
ct+ψ)+Q
2(t)sin
2(△w
ct+ψ)
—2{I(t)+P}Q(t)cos(△w
ct+ψ)sin(△w
ct+ψ)
{Q＂(t)}
2＝[{I(t)+P}sin(△w
ct+ψ)+Q(t)cos(△w
ct+ψ)]
2
＝{I(t)+P}
2sin
2(△w
ct+ψ)+Q
2(t)cos
2(△w
ct+ψ)
+2{I(t)+P}Q(t)sin(△w
ct+ψ)cos(△w
ct+ψ)
But, the output of the accumulator (903) of addition is carried out in the output of the 1st, the 2nd squarer (901,902), no matter carrier wave recover be all finish or do not finish all identical with following mathematical expression 6.
[mathematical expression 6]
X(t)＝I
2(t)+Q
2(t)+P
2+2P?I(t)
That is, if carry out symbol clock recovery by the output of accumulator 903, the recovery of carrying out symbol clock that not influenced by any carrier wave.
And, the output of the carrier frequency of elimination carrier wave recovery section 803 outputs and the accumulator 903 of phase error composition, in order under the situation of 1/2 frequency (fs/2) information that does not have the symbol clock frequency fully, also to recover symbol clock, be entered into the 3rd squarer 904 and carry out square.The output process of squarer 904 only allows to be input to correction Gardner (name) synchronous error test section 906 by the prefilter 905 of the marginal portion of spectrum.
Fig. 9 is identical with the original signal size, and same-phase (in phase) line noise that correctly postpones a symbol is transmitting accumulator 903 output characteristic under the situation about existing on the passage, the output frequency characteristic and prefilter 905 output frequency characteristics of the 3rd squarer 904.As seen from Figure 9,1/2 frequency (fs/2) information that in accumulator 903 output signal frequency characteristics, does not have the symbol clock frequency fully.But, in the frequency characteristic of the 3rd squarer 904 outputs, have the new information of 1/2 frequency (fs/2) of symbol clock frequency.This is because when the output of accumulator 903 carried out square, and 1/4 frequency (fs/4) of symbol clock frequency becomes to grade to move and comes to form.Carry out filtering near 1/2 frequency (fs/2) of the symbol clock frequency of 905 pairs the 3rd squarers of prefilter, 904 outputs, output to then and proofread and correct Gardner (name) synchronous error test section 906.
And, proofread and correct Gardner (name) synchronous error test section 906 owing to can extract the synchronous error signal of symbol clock, therefore, can carry out the recovery of symbol clock.
That is, 906 pairs of two symbol sampler differences by prefilter 905 of correction Gardner (name) synchronous error test section multiply by a median sample value and detect the synchronous error signal.From proofreading and correct the synchronous error signal that Gardner (name) synchronous error test section 906 detects, be input to numerically-controlled oscillator NCO 908 through low pass filter 907.Numerically-controlled oscillator NCO 908 produces the 2 times of new symbol clock frequencies (2fs, wherein fs is the symbol clock frequency) that compensated by the synchronous error signal of low-pass filtering, and it is outputed to resampling portion 804.
At this moment, do not utilize the 1st, the 2nd squarer 901,902 and accumulator 903, and only utilize the real number of 904 pairs of resampling portions of squarer 804 output to become sub-signal to carry out square, be input to prefilter then and can obtain result much at one yet as Fig. 9; But because the influence of the carrier signal composition that comprises in the real number composition is also moved simultaneously, therefore, be impossible carry out the symbol clock recovery action normally under the situation of not finishing the carrier wave recovery this moment.
On the one hand, symbol clock recovery of the present invention portion 900 is the recovery of symbol clock, if use two squarers 901,902 and accumulator 903, then is not subjected to the influence of any carrier wave recovery section fully; As another example of the present invention, without carrier wave recovery section 803 passband signals, can recover symbol clock by symbol clock recovery portion 900.
As another example of the present invention, if replace the 1st, the 2nd squarer 901,902 use two signed magnitude arithmetic(al) portions that I, the Q signal of base band are respectively asked for its absolute value, then can constitute not only and to reduce the hardware burden that produces when signal being carried out square, and the formation symbol clock recovery portion that not influenced by the carrier wave recovery section.
And, analog/digital A/D converter section 801 of the present invention utilizes the fixed frequency of fixed oscillator (not shown in the drawings) output or utilizes 2 times of symbol clock frequencies (2fs) of variable oscillator (not shown in the drawings) output, can be digital passband signal with simulation passband conversion of signals.At this moment, because the symbol clock frequency (2fs) of fixed frequency than 2 times that produces in fixed oscillator is taller and can not regulate, therefore, between carrier wave recovery section 803 and symbol clock recovery portion 900, the resampling portion 804 that the signal of digital baseband is carried out interpolation with 2 times of symbol clock frequencies (2fs) need be set; If the use variable oscillator does not then need to be provided with resampling portion 804.
The present invention is provided with squarer to aforesaid other examples if append between accumulator and prefilter, then can obtain the resulting result as Fig. 9; And, also can carry out the recovery of symbol clock under the situation of this frequency even if cause because of reasons such as ghost images near symbol clock frequency 1/2 frequency (fs/2) of synchronizing information big distortion to be arranged or do not have.
By the content of above-mentioned explanation, if the colleague has multiple improvement and modification to well imagine not leaving the technology of the present invention thought range.
And technical scope of the present invention is not that the content in the example explanation limits, but decides according to patent request scope.
Claims (6)
1. the symbol clock recovery device of a Digital Television is characterized in that it comprises and will simulation passband signal samples with the analog/digital clock frequency and be converted into the analog/digital conversion portion of digital passband signal; To the reference carrier signal of digital passband signal times, and it is transformed to the carrier wave recovery section of digital baseband signal to produce by carrier wave recovery process;
Real number composition to the digital baseband of carrier wave recovery section output becomes sub-signal with imaginary number, separately its result's of output operational part after the summed square;
The squarer that operational part output is carried out square again;
In the squarer output signal, 1/2 frequency of symbol clock frequency is carried out the prefilter of filtering;
Two sampling differences by prefilter multiply by Gardner (Gardner) the synchronous error test section that a median sample value detects the synchronous error signal;
In the synchronous error signal of Gardner (Gardner) synchronous error test section output, filtering low band signal composition, and, produce the filtering and the oscillator of the 2 times of new symbol clock frequencies that compensated according to the synchronous error signal low band signal composition of filtering;
The symbol clock recovery portion that forms by described operational part, squarer, prefilter, Gardner (Gardner) synchronous error test section, filtering and oscillator.
2. the symbol clock recovery device of Digital Television according to claim 1 is characterized in that described operational part is that the digital passband real number composition that analog/digital conversion portion exports is become sub-signal with imaginary number, separately its result of output after the summed square.
3. the symbol clock recovery device of Digital Television according to claim 1 is characterized in that described operational part is that the digital baseband real number composition that the carrier wave recovery section is exported is become sub-signal with imaginary number, its result of output after the addition that takes absolute value separately.
4. the symbol clock recovery device of Digital Television according to claim 1, it is characterized in that described operational part is that the digital passband real number composition that analog/digital conversion portion exports is become sub-signal with imaginary number, its result of output after its absolute value addition of respectively asking for.
5. the symbol clock recovery device of Digital Television according to claim 1, it is characterized in that if the clock frequency of the analog/digital of analog/digital conversion portion is a fixed frequency, then between carrier wave recovery section and symbol clock recovery portion, set up a digital baseband real number composition and become sub-signal with imaginary number with the output of carrier wave recovery section, with 2 times of symbol clock frequency resamplings and carry out the resampling portion of interpolation, promptly have a resampling portion more; And 2 times the symbol clock frequency that symbol clock recovery portion produces outputs to resampling portion.
6. the symbol clock recovery device of Digital Television according to claim 1 is characterized in that described analog/digital conversion portion with 2 times of symbol clock frequencies that symbol clock recovery portion produces, uses as the analog/digital clock frequency.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2003101190325A CN100499755C (en) | 2003-12-11 | 2003-12-11 | Unit for recovering symbol clock in digital TV |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2003101190325A CN100499755C (en) | 2003-12-11 | 2003-12-11 | Unit for recovering symbol clock in digital TV |
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| CN1627805A CN1627805A (en) | 2005-06-15 |
| CN100499755C true CN100499755C (en) | 2009-06-10 |
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| CNB2003101190325A Expired - Fee Related CN100499755C (en) | 2003-12-11 | 2003-12-11 | Unit for recovering symbol clock in digital TV |
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| CN104092529B (en) * | 2014-07-24 | 2018-05-01 | 上海寰视网络科技有限公司 | A kind of clock is adjusted in synchronism system and its adjusting method |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5483292A (en) * | 1994-03-09 | 1996-01-09 | Samsung Electronics Co., Ltd. | Symbol clock regeneration in digital signal receivers for recovering digital data buried in NTSC TV signals |
| US5859671A (en) * | 1995-06-09 | 1999-01-12 | Samsung Electronics Co., Ltd. | Symbol timing recovery circuit and method |
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2003
- 2003-12-11 CN CNB2003101190325A patent/CN100499755C/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5483292A (en) * | 1994-03-09 | 1996-01-09 | Samsung Electronics Co., Ltd. | Symbol clock regeneration in digital signal receivers for recovering digital data buried in NTSC TV signals |
| US5859671A (en) * | 1995-06-09 | 1999-01-12 | Samsung Electronics Co., Ltd. | Symbol timing recovery circuit and method |
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| CN1627805A (en) | 2005-06-15 |
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