CN1780274A - Carrier releaser of DTV receiver - Google Patents
Carrier releaser of DTV receiver Download PDFInfo
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- CN1780274A CN1780274A CNA200410084330XA CN200410084330A CN1780274A CN 1780274 A CN1780274 A CN 1780274A CN A200410084330X A CNA200410084330X A CN A200410084330XA CN 200410084330 A CN200410084330 A CN 200410084330A CN 1780274 A CN1780274 A CN 1780274A
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Abstract
A DC clearer that can clear pilot frequency is installed in input path of Q signal in phase error detector in carrier recovery device to improve defects of VSB transmission system, which are low tracing performance of carrier synchronization and data pattern jitter in long distance transmission.
Description
Technical field
The present invention relates to digital TV (DTV) receiver aspect, more particularly, relate to the carrier centering device in the DTV receiver of VSB mode.
Background technology
Usually, the VSB mode of the Major Leagues (Grand Alliance) that adopt as the U.S. and domestic digital TV (for example HDTV) load mode standard is a kind of when modulation signal, be the center with the carrier wave only to decay, the mode that the remainder during a side bandwidth signal is modulated in 2 side bandwidth of Sheng Chenging up and down.
That is, the mode that a side wave bandwidth spectrum of baseband is moved, transmits to transmission band only, it is a kind of mode in the efficient utilized bandwidth domain mode.
When VSB modulates, if the DC frequency spectrum of baseband (base band) is moved to transmission band (pas sband), be transformed into the tone frequency spectrum, we are called pilot signal with this signal.That is, when TV station carries out VSB when modulation, can be in order to make receiver correctly with signal demodulator, with pilot signal to aerial transmission.
Fig. 1 is the formation block diagram of common digital TV receiver.We can be with A/D converter section 103; Phase place cutting part 104; Frequency mixer 105; Integration kalman filter device 106; Channel equalisation portion 107; Timing recovery portion 108, carrier resetting portion 109 is called the VSB wave detector.
Promptly, if receive according to VSB mode modulated RF signal by antenna, tuner 101 uses the heterodyne method modulation system, behind the channel frequency of selecting to wish, the VSB signal that is loaded in the RF bandwidth in the above-mentioned channel frequency is reduced to fixing intermediate frequency bandwidth (IF; Usually be extensive use of 44MHz or 43.5MHz), start other suitable channel signals.
And the output signal of the tuner 101 that the frequency spectrum of arbitrary channel is moved, exports to the IF bandwidth of regulation is removed surface acoustic wave (the Surface Acoustic Wave of noise signals and simulation integration filter function by having other bandwidth signal of removing; SAW) filter 102.
At this moment, be example with the digital broadcast signal, only stay bandwidth, after the rest interval full scale clearance, to 103 outputs of A/D converter section from the intermediate frequency of 44MHz to 6MHz.A/D converter section 103 is sampled to the output of above-mentioned SAW filter 102, with above-mentioned SAW filter 102 output digitlizations according to 2 times of the VSB symbol clock of timing recovery portion 108 output.
To 104 inputs of phase place cutting part, with I, Q signal multiplies each other with the output of above-mentioned A/D converter section 103, be separated into I Q composition after, to frequency mixer 105 outputs.
(Numerically ControlledOscillator:NCO: numerically-controlled oscillator) 112 inputs form the complex carrier of carrier resetting to above-mentioned frequency mixer 105 by the complex oscillation device, promptly, behind sinusoidal wave (SIN) and the cosine wave (COS), I with the transmission band of exporting by above-mentioned phase place cutting part 104, Q signal multiplies each other respectively, with the I of transmission band, Q signal is to the I of baseband, and Q signal moves.
The I of baseband, Q signal are in the time of 106 outputs of integration kalman filter device, for carrier resetting, to 109 outputs of carrier resetting portion.
After the frequency offset (frequency offset) and phase jitter (phase jitter) of above-mentioned carrier resetting portion 109 removing carrier wave from the pilot signal of the baseband of frequency mixer 105 outputs, to above-mentioned frequency mixer 105 feedback related compound sine waves.Therefore, above-mentioned frequency mixer 105 is exported the baseband digital signal of frequency offset and phase jitter recovery to integration kalman filter device 106.
At this moment, in A/D converter, 103 be transformed into digital signal, be separated into I by phase place cutting part 104, behind the Q signal, to 109 outputs of carrier resetting portion through the signal of all simulation process process.Therefore, if carrier resetting portion 109 does not finish carrier resetting, all digital processing units in carrier resetting portion 109 rear ends just can not normally move.
Fig. 2 is the schematic diagram of the frequency characteristic of the aerial ripple signal that defines in the DTV specification of the present Korea S and the U.S..Centre frequency of each channel (fc) and pilot tone (pilot) frequency (fp) difference, here, with centre frequency fc, pilot carrier frequency fp mark.
Give one example, the middle frequency of the 6MHz of the bandwidth of each surface wave channel (width) is exactly centre frequency (fc), transmits on the signal to exist the frequency of carrier signal to be called as pilot carrier frequency (fp).At this moment, not using carrier wave, and be to use this term of pilot tone, is in order to make analog tv signal in the existing broadcasting not be subjected to the influence of DTV signal, and the amplitude of carrier signal is dwindled the cause that (approximately 13dB) transmits.
Present carrier resetting portion 109 prevailing algorithms, just be to use DFPLL (the Digital Frequency Phase Loop Lock: the locking of numerical frequency phase loop) that shows in the parts that dot among Fig. 1, its circuit structure is simple, and superior performance is widely used.That is, the carrier resetting portion 109 of DFPLL structure is the I of the transmission band of phase place cutting part 104 outputs, and Q signal is to the I of baseband, Q signal detection, locking (locking) frequency and phase place.
From Fig. 1 we as can be seen, by A/D converter 103 and phase separator 104, with the I of digitized transmission band, Q signal is to frequency mixer 105 inputs, frequency mixer 105 will form the complex carrier input of carrier resetting, promptly by NCO112, behind input sine wave (SIN) and the cosine wave (COS), with the I of the transmission band of exporting by above-mentioned phase separator 104, Q signal multiplies each other respectively, with the I of transmission band, Q signal is to the I of baseband, and Q signal moves.
The I of baseband, Q signal for carrier resetting, export to the frequency plot error sense part (Frequency PhaseErrorDetector:FPED) 110 of carrier resetting portion 109 in the time of 106 outputs of integration kalman filter device.
Above-mentioned FPED110 removes FLL (the Frequency Locked Loop: the frequency lock circulation) after the process, enter PLL (the Phase Locked Loop: the phase locking circulation) process that the phase error between above-mentioned two carrier signals of having removed frequency difference is removed of frequency difference of the standard carrier composition of the carrier wave composition of received signal and receiver self.
That is, after above-mentioned FPED110 goes out frequency offset and phase error from the pilot signal detection of the baseband of frequency mixer 105 output, to recursive filter 111 outputs.
The output that above-mentioned recursive filter 111 filters above-mentioned FPED110 is after the accumulative total, to complex oscillation device (NCO) 112 outputs.Above-mentioned NCO112 generates the compounded sine ripple according to the export ratio of recursive filter 111, to frequency mixer 105 outputs.
Fig. 3 is the schematic diagram of the frequency plot error sense part of existing technologies.The frequency plot error sense part of existing technologies is made of following components: the 1st, the 2 low territory is by filter (301) (302; Delayer 303; Symbol extractor displacer 304; Multiplier 305.
With the I of the baseband of above-mentioned frequency mixer 105 outputs, Q signal is input in the FPED110, the I signal of baseband to the 1st low territory of FPED110 by filter 301 inputs, the Q signal of baseband to the 2nd low territory by filter 302 inputs.
At this moment, 109 in the carrier resetting portion of carrier resetting needs to exist in the bandwidth of 6MHz the signal of the frequency periphery of pilot carrier frequency (fp).
Therefore, the above-mentioned the 1st, the 2 low territory from I, is removed all the other frequency contents that have data component by filter 301,302 in the Q signal, can prevent the low problem of performance of the carrier resetting portion that data cause.That is, the I of baseband, the pilot signal of Q signal is transformed into the DC composition.Say more closely, be transformed into the frequency content of DC composition periphery.
This is that the difference of the carrier frequency composition that generates according to the carrier frequency composition of input signal and NCO112 produces.Owing to only have the composition of DC periphery, may realize carrier resetting.Therefore, the 1st, 2 low territory is by the remainder data composition of filter 301,302 removings except the signal of DC composition periphery.
The above-mentioned the 1st low territory is imported to delayer 303 by the output of filter 301.Above-mentioned delayer 303 will have been removed the I signal of data component and postpone certain hour, to 304 outputs of symbol extractor displacer.
At this moment, delayer 303 is passed through by the I signal of the pilot component of filter 302 outputs in the 1st low territory, if pilot tone is not transformed into DC composition accurately, will produce the phase error of respective degrees.Therefore, the pilot carrier frequency composition and the difference of the carrier frequency composition of NCO112 of the transmission band signal of delayer 303 input is transformed into the form of phase error, exports to symbol extractor displacer 304.
Above-mentioned symbol extractor displacer 304 is extracted the symbol of the signal of above-mentioned delayer 303 outputs out, and the signal with 1 or-1 is to above-mentioned multiplier 305 outputs.After multiplier 305 multiplies each other the symbol of above-mentioned I signal and the Q signal of having removed data component, as phase error, to recursive filter 111 outputs.
Through after such process, above-mentioned complex carrier and former comparing, more approaching with the carrier frequency composition of the more signals of input.If move such process repeatedly, NCO112 produces the carrier frequency signaling similar to the carrier frequency composition of input signal, and to frequency mixer 106 outputs, frequency mixer 106 becomes the signals migrate of transmission band the signal of the baseband of hope.
That is, if the on all four words of frequency content of the carrier signal that produces in the frequency of the pilot tone of the carrier signal composition that exists in the transmission band of input and the NCO112 finish the FLL process.But in fact, because the natural characteristic of NCO112 and the influence that is subjected to transmission line characteristics, the frequency of two carrier signals is merely able to have similar frequency content, can not be in full accord.Therefore, 109 pairs of mutual inconsistent frequency contents of carrier resetting portion are carried out revisal, change the frequency of NCO112, realize the frequency unanimity of two carrier signals.
Finish before the FLL process, above-mentioned symbol extractor displacer 304 exports 1 and-1 in turn, in case any one signal is only exported in 1 and-1 in the end of FLL process.
Like this, the certain signal of symbol extractor displacer 304 outputs, being failure to actuate by filter 301, delayer 303, symbol detector 304 in the above-mentioned the 1st low territory, still has only the 2nd low territory by filter 302 actions.
That is,, will automatically enter PLL (the Phase Locked Loop: the phase locking circulation) process that removes the phase error between two carrier signals if finish the FLL process.
The above-mentioned the 2nd low territory is by the Q signal of filter 302 receiving mixers 106, and composition clears data.The output signal of the 2nd low territory by filter 302 be by multiplier 305, after multiplying each other with the symbol of I signal, as phase error, to recursive filter 111 outputs.
By such process, above-mentioned complex carrier and former comparing, owing to removed the phase error of complex carrier, more approaching with the phase place of input composite signal.
Such DFPLL algorithm constitutes by simple, has the search performance brilliance, improves the advantage of the stability of system.
There are the following problems for existing technologies.
Because the DFPLL algorithm moves by pilot tone (pilot) composition of signal of reception basically, is subjected to the influence of pilot signal power.Therefore, when the intensity of approving pilot signal slowly changes, when the slow mobile ghost of action (slow moving ghost) produces, especially can see the characteristic that it is fragile.
Fig. 4 is the schematic diagram of the baseband signal spectrum of vestigial sideband (VSB) transfer system.
If form the frequency and the phase place of carrier synchronization, only in I signal, can see the pilot signal that DC is relevant.The DC pilot signal offsets in the Q signal, can not see.We can see this characteristic of VSB transfer system from figure.
But, when importing the phase place of VSB transmission signal carrier, in Q signal, show the DC pilot component according to the state of 90 degree or particular phases.
The frequency of carrier synchronization forms synchronous state, that is, when finishing the situation of FLL, the DC pilot signal value former state that shows in the Q signal is imported to recursive filter (loop filter).If to recursive filter input DC pilot signal, VSB baseband signal demonstrates the effect with frequency offset according to the power of DC pilot signal in this manner.
From restoring the parts side of symbol clock, can experience this frequency offset as the symbol clock variation, by this frequency offset, can see VSB receiver picture error.
And the VSB transfer system has bad characteristic from structure to remote ghost (ghost).This is owing to for main signal, have data pattern shake (data pattern jitter) cause that phenomenon is more serious of remote ghost (ghost).This causes approving that the serious performance of the channel of remote ghost is low.
Summary of the invention
The present invention is in order to address the above problem, and its objective is to the user provides carrier centering device in a kind of DTV receiver of the tracking performance that slowly moves (slow moving) that can improve ghost (ghost) signal.
Another object of the present invention is the amount that a kind of pattern shake that must take place when reducing carrier synchronization is provided for the user, can improve TOV (the Threshold OfVisibility: the carrier centering device in the DTV receiver of characteristic visibility limit) of white noise.
A further object of the present invention is for the user provides a kind of VSB of having transfer system, can effectively solve the carrier centering device in the DTV receiver of mis-behave problem of remote ghost.
To achieve these goals, the carrier centering device of DTV receiver of the present invention is made of following components, and as feature: form after the Frequency Synchronization of carrier synchronization, drive, I with digitized transmission band, Q signal is transformed into the I of baseband, Q signal, the DC remover of removing DC pilot component from the baseband Q signal that frequency mixer receives; From above-mentioned baseband I signal, remove the 1st low territory of the data component except pilot component and pass through filter; The 2nd of the composition that clears data from the Q signal of above-mentioned DC remover output hangs down the territory and passes through filter; The above-mentioned the 1st low territory is transformed into the delayer of DC composition by the I signal of the pilot component of filter output; From the output signal of above-mentioned delayer, extract the symbol extractor displacer of I signal symbol out; Multiply each other removing the symbol of above-mentioned I signal and the Q signal of data component, generate the multiplier of phase error.
The feature of the carrier centering device in the DTV receiver of the present invention is: above-mentioned DC remover did not preferably drive before the Frequency Synchronization that forms carrier synchronization, walked around the Q signal that (bypass) receives.
Carrier centering device in the DTV receiver of the present invention preferably also comprises following structure, and as feature: the phase error that above-mentioned multiplier generates is filtered the recursive filter of accumulative total; Ratio according to above-mentioned recursive filter output generates complex carrier, to the complex oscillation device of above-mentioned frequency mixer feedback.
The feature of the carrier centering device in the DTV receiver of the present invention is: above-mentioned DC remover was preferably walked around the Q signal of frequency mixer reception (bypass) the above-mentioned the 2nd low territory and is passed through filter before the Frequency Synchronization of carrier synchronization forms.
The feature of the carrier centering device in the DTV receiver of the present invention is: for the I signal of above-mentioned pilot component correctly being transformed into the DC composition, above-mentioned delayer preferably postpones certain hour with the I signal of pilot component.
The feature of the carrier centering device in the DTV receiver of the present invention is: above-mentioned DC remover preferably also comprises following structure, and as feature: the subtracter of DC inferred value of removing the Q signal of migration signal demodulator from the Q signal that frequency mixer receives; Extract the accumulator of residual DC components in the output signal of above-mentioned subtracter out; Calculate the DC inferred value of Q signal from above-mentioned residual DC components, to the multiplier of above-mentioned subtracter feedback.
The feature of the carrier centering device in the DTV receiver of the present invention is: above-mentioned multiplier is preferably on duty with the step amplitude with the residual DC of above-mentioned accumulator output, calculates the DC inferred value of Q signal.
The feature of the carrier centering device in the DTV receiver of the present invention is: above-mentioned step amplitude is big more, and the coalescence rate of DC remover is fast more, and the residual DC value of normal condition increases, and the step amplitude is more little, and the residual DC value reduces, and the coalescence rate of DC remover is slack-off.
Other purposes of the present invention, feature are that advantage will can fully understand by the detailed description of accompanying drawing to embodiment.
Digital restoring means in the DTV receiver of the present invention is removed the DC composition of Q signal by the DC remover, can prevent the phenomenon of the serious change of symbol clock.
Therefore, can reduce effectively that the shortcoming that the VSB transfer system is had--the tracking performance of-carrier synchronization is low, especially when the slow mobile ghost of approval, can improve because the tracking performance of the carrier synchronization system of the fragility that the construction problem of VSB transfer system causes.And, converge characteristic owing to improve the frequency of carrier resetting portion, also can improve the symbol frequency characteristic of the symbol restoring device of carrier resetting portion rear end.
And, owing to can reduce the pattern jitter phenomenon of remote ghost, can effectively prevent to have the performance degradation of the remote ghost of VSB system construction, because the amount of the pattern that must take place in the time of can reducing carrier synchronization shake can improve TOV (the Threshold Of Visibility: limit of visibility) characteristic about white noise.
And, by the DC remover, reach effect with the carrier phase error equalization, can improve the performance of the removing noise of normal condition.As a result, change VSB receiver that still can operating stably even can produce receiving channels.
Description of drawings
Fig. 1 is the formation block diagram of common digital TV dispensing device;
Fig. 2 is the schematic diagram of the frequency characteristic of the aerial ripple signal that defines in the DTV specification of the present Korea S and the U.S.;
Fig. 3 is the schematic diagram of the frequency plot error sense part of existing technologies;
Fig. 4 is the schematic diagram of the baseband signal spectrum of vestigial sideband (VSB) transfer system;
Fig. 5 is the schematic diagram of carrier centering device medium frequency phase error sense part of the present invention;
Fig. 6 is the formation schematic diagram of DC remover;
Fig. 7 is in Q signal, during approval DC, existing technologies and carrier synchronization of the present invention is converged the analog waveform figure that characteristic compares;
Fig. 8 is in Q signal, during approval DC, with the analog waveform figure that characteristic compares that converges of existing technologies and symbol restoring device of the present invention;
Fig. 9 is in the channel of the remote ghost of approval, and existing technologies and carrier synchronization of the present invention are converged the analog waveform figure that characteristic compares.
Accompanying drawing major part symbol description
Filter is passed through in 502: the 1 low territories of 501:DC remover
Filter 504 was passed through in low territory in 503: the 2: delayer
505: symbol extractor displacer 506: multiplier
Embodiment
Embodiment to the carrier centering device in the DTV receiver of the present invention is elaborated below with reference to accompanying drawings.Structure of the present invention and effect according to description of drawings describe as just an embodiment, and above-mentioned technological thought of the present invention and core constitute and effect is not limited thereto.
By the A/D converter and the phase separator of VSB detector arrangement, with the I of digitized transmission band, Q signal is imported to frequency mixer, and frequency mixer forms the complex carrier of carrier resetting by complex oscillation device (NCO) input.That is, behind sinusoidal wave (SIN) and the cosine wave (COS), with the I of the transmission band of exporting by above-mentioned phase separator, Q signal multiplies each other respectively, and with the I of transmission band, Q signal moves into the I of baseband, Q signal.
When the I of baseband, Q signal export to the integration kalman filter device, for carrier resetting, frequency plot error sense part (the Frequency Phase ErrorDetector:FPED) output to carrier resetting portion.
Fig. 5 is the detailed construction schematic diagram of carrier centering device medium frequency phase error sense part of the present invention (FPED).
With reference to Fig. 5, carrier centering device medium frequency phase error sense part of the present invention (FPED) is made of following components: form after the Frequency Synchronization of carrier synchronization, drive, I with digitized transmission band, Q signal is transformed into the I of baseband, Q signal, the DC remover 501 of removing DC pilot component from the baseband Q signal that frequency mixer receives; The 1st low territory of removing the data component except pilot component from above-mentioned baseband I signal is by filter 502; The 2nd of the composition that clears data from the Q signal of above-mentioned DC remover output hangs down the territory by filter 503; The above-mentioned the 1st low territory is transformed into the delayer 504 of DC composition by the I signal of the pilot component of filter output; From the output signal of above-mentioned delayer, extract the symbol extractor displacer 505 of the symbol of I signal out; With the symbol of the I signal of above-mentioned symbol extractor displacer 505 outputs with after removing the Q signal of the above-mentioned the 2nd low territory by the data component of filter 503 outputs and multiplying each other, as phase error, the multiplier 506 of recursive filter output to the back-end.
On the characteristic of VSB transfer system, if form the Frequency Synchronization of carrier synchronization, only see the corresponding pilot signal of DC in I signal, in Q signal, the DC pilot signal is offset, and can not see.
But, when the phase place of VSB transmission signal carrier is imported according to the state of 90 degree or particular phases, in Q signal, demonstrate the DC pilot component, after above-mentioned DC remover 501 forms the Frequency Synchronization of carrier synchronization, from the baseband Q signal that frequency mixer receives, remove the DC composition, by the DC composition of Q signal, can prevent that the performance of carrier resetting portion is low.
Promptly, before the Frequency Synchronization that forms carrier synchronization, above-mentioned DC remover 501 does not drive, the Q signal former state that receives is walked around (bypass), after, the Frequency Synchronization of formation carrier synchronization, promptly, finish the FLL process, receive the FrequencyLocking Indication Signal (frequency locking index signal) that shows the Frequency Synchronization that forms carrier synchronization and just drive later on.
Fig. 6 is the formation schematic diagram of DC remover.
With reference to Fig. 6, we as can be seen, DC remover 501 is made of following components: remove the DC inferred value that moves the present Q signal that moves signal demodulator from the Q signal that frequency mixer receives, the subtracter 501a to the above-mentioned the 2nd low territory by filter 503 outputs; With the output signal equalization of above-mentioned subtracter 501a, extract the accumulator 501b of DC composition out; From the DC value of above-mentioned accumulator (501b) output, calculate the DC inferred value, and it is fed back the multiplier 501c of (feedback) to above-mentioned subtracter.
Therefore, above-mentioned subtracter 501a receives the DC inferred value of multiplier 501c output, subtracts from the Q signal of frequency mixer input and calculates the DC inferred value, can remove the DC composition of Q signal.
Here, it should be noted that above-mentioned DC inferred value is exactly that the DC of former subtracter 501a output signal is on duty with step amplitude (μ), in fact the DC inferred value of Q signal ' now ' of acquisition, have different values with the DC value of the Q signal of present input.
Therefore, the output signal of subtracter 501a is in does not remove the DC composition fully, the state of remaining residual DC components.Extract this residual DC components out by above-mentioned accumulator 501b, in multiplier 501c, step amplitude and μ are multiplied each other, calculate new DC inferred value.
Therefore, more repeatedly circulation (1oop) through constituting by above-mentioned subtracter 501a, accumulator 501b, multiplier 501c, the residual DC value is just more and more littler.
The value of above-mentioned step amplitude and μ has determined the coalescence rate of DC remover and the DC residue of normal condition.
That is, when step amplitude and μ were big, although coalescence rate speeds, the residual DC value of normal condition was big.On the contrary, when step amplitude and μ hour, although residue diminishes, coalescence rate slowed down.
The action of the carrier centering device that constitutes according to said structure is as follows.
At first, carrier centering device starts FLL, carries out the search of carrier resetting medium frequency, finish frequency search after, automatically start PLL, enter the phase search process.
Because carrier resetting only needs to exist in the bandwidth of 6MHz the signal of the frequency periphery of pilot carrier frequency, at first, the residual frequency composition that has data component is removed by filter 502,503 in the above-mentioned the 1st, the 2 low territory from I signal and Q signal.
At this moment, owing to do not drive above-mentioned DC remover 501 before forming FLL, the Q signal former state of input is walked around (bypass) DC remover 501.
Along with the I signal of baseband by the 1st low territory by filter 502, be transformed into the DC pilot component.This is to produce according to the difference between the carrier frequency composition that generates in the carrier frequency composition of the signal of input and the complex oscillation device.That is,, just may carry out carrier resetting owing to only have pilot component, so, 502 li removings of filter all the other compositions except DC periphery signal passed through in the 1st low territory.
On the other hand, the Q signal of baseband passes through filter 503 by the 2nd low territory.Therefore, the data component of removing except DC periphery signal.
And, the above-mentioned the 1st low territory is imported to delayer 504 by the output of filter 502.
Above-mentioned delayer 504 will have been removed the I signal of data component and postpone certain hour, to 505 outputs of symbol extractor displacer, at this moment, delayer 504 is passed through by the I signal of the pilot component of filter 502 outputs in the 1st low territory, if pilot tone does not become the DC composition, will produce the phase error of respective degrees.
Therefore, above-mentioned delayer 504 is transformed into the form of phase error with the difference of the carrier frequency composition of pilot carrier frequency composition and the complex oscillation device of the transmission band signal of input, exports to symbol extractor displacer 505.
And, 505 of above-mentioned symbol extractor displacers are extracted the symbol of the signal of above-mentioned delayer 504 outputs out, to multiplier 506 output, after multiplier 506 multiplies each other the symbol of I signal and the Q signal of having removed data component, as phase error recursive filter output to the back-end.
Recursive filter filters the phase error of input, carries out cumulative calculation, and to complex oscillation device (NCO) output, above-mentioned NCO is according to the export ratio of above-mentioned recursive filter, and (COS SIN), exports to above-mentioned frequency mixer to generate complex carrier.
Through after such process, above-mentioned complex carrier and former comparing, more approaching with the carrier frequency composition of input composite signal.If move such process repeatedly, NCO112 generates the carrier frequency signaling similar to the carrier frequency composition of input signal, and to frequency mixer 106 outputs, frequency mixer 106 becomes the signals migrate of transmission band the signal of the baseband of hope.
That is, if the on all four words of frequency content of the carrier signal that produces in the frequency of the pilot tone of the carrier signal composition that exists in the transmission band of input and the NCO112 finish the FLL process.But in fact, because the natural characteristic of NCO112 and the influence that is subjected to transmission line characteristics, the frequency of two carrier signals is merely able to have similar frequency content, can not be in full accord.Therefore, 109 pairs of mutual inconsistent frequency contents of carrier resetting portion are carried out revisal, change the frequency of NCO112, realize the frequency unanimity of two carrier signals.
Finish before the FLL, above-mentioned symbol extractor displacer 505 exports 1 and-1 in turn, if any one signal is only exported in 1 and-1 in the FLL end.
Like this, the certain signal of symbol extractor displacer 505 outputs, being failure to actuate by filter 502, delayer 504, symbol detector 505 in the above-mentioned the 1st low territory, still has only the 2nd low territory by filter 503 actions.
That is,, will automatically enter PLL (the Phase Locked Loop: the phase locking circulation) process that removes the phase error between two carrier signals if finish the FLL process.
On the other hand, above-mentioned DC remover 501 has only the FLL of reception to finish, and behind the Frequency Locking Indication Signal (frequency lock index signal) of the Frequency Synchronization of demonstration formation carrier synchronization, can drive.
Therefore, the Q signal of the baseband of frequency mixer 106 input is removed the DC pilot components by DC remover 501, with the Q signal of having removed the DC pilot component to the 2nd low territory by filter 503 inputs, the 2nd low territory is by filter 503 composition that clears data.
And, by multiplier 506, the Q signal of removing above-mentioned data component is exported to recursive filter 111 as phase place and error.Above-mentioned recursive filter 111 filters phase errors, after the accumulative total, to NCO112 output, above-mentioned NCO112 according to the export ratio of above-mentioned recursive filter 111 generate complex carrier (COS, SIN), to above-mentioned frequency mixer 105 outputs.
By such process, remove the phase error of complex carrier.
Fig. 7 when approving DC in Q signal, converges the analog waveform figure that characteristic compares with existing technologies and carrier synchronization of the present invention.Fig. 8 is when approving DC in Q signal, with the analog waveform figure that characteristic compares that converges of existing technologies and symbol restoring device of the present invention.
The DC value of using in the simulation is 0.5.
From Fig. 7 we as can be seen, according to the DC signal of existing technologies approval, the frequency of carrier synchronization converges characteristic and changes a lot suddenly.
The frequency of this carrier synchronization converges characteristic variations and brings very big influence for the symbol restoring device of rear end.As shown in Figure 8, we can confirm that symbol clock restores synchronous symbol frequency characteristic and changes a lot from figure.This silp phenomenon by symbol clock shows.
But the frequency of observing the carrier resetting portion that is suitable for FPED of the present invention converges characteristic, and we approve what difference is the characteristic before and after the DC almost do not have as can be seen.And the symbol clock of the symbol restoring device of carrier resetting portion rear end restores synchronous symbol frequency characteristic does not have to take place too big variation.
On the other hand, FPED of the present invention detects the DC signal with the aignal averating of DC remover, and at this moment, the phase error of carrier wave also has the effect of equalization together, under the normal condition, can improve the performance of removing noise.
Analog waveform figure by Fig. 9 can obtain confirming about this point.
Fig. 9 is the channel of the remote ghost of approval, and existing technologies and carrier synchronization of the present invention are converged the analog waveform figure that characteristic compares.
The VSB transfer system has bad characteristic for remote ghost (ghost).This is owing to for main signal, have data pattern shake (data patternjitter) cause that phenomenon is more serious of ghost far away (ghost).
We exist very serious performance low in the channel of the remote ghost of approval as can be seen under the existing technologies from Fig. 9.But the system of the FPED that employing the present invention proposes can significantly improve the data pattern jitter phenomenon of remote ghost.
By above-mentioned description, the related work personnel can carry out various change and modification fully in the scope that does not depart from this invention technological thought.
Therefore, the technical scope of this invention is not limited to the content on the specification, must determine its technical scope according to interest field.
Claims (7)
1, a kind of carrier centering device of DTV receiver, it comprises:
The Frequency Synchronization that forms carrier synchronization is with rear drive, and with the I of digitized transmission band, Q signal is transformed into the I of baseband, Q signal, the DC remover of removing D pilot component from the basic frequency Q signal that frequency mixer receives;
From above-mentioned baseband I signal, remove the 1st low territory of the data component except pilot component and pass through filter;
The 2nd of the composition that clears data from the Q signal of above-mentioned DC remover output hangs down the territory and passes through filter;
The above-mentioned the 1st low territory is transformed into the delayer of DC composition by the I signal of the pilot component of filter output;
From the output signal of above-mentioned delayer, extract the symbol extractor displacer of the symbol of I signal out;
Take advantage of and settle, generate the multiplier of phase error except that the symbol of above-mentioned I signal and the Q signal of data component.
2, the carrier centering device of DTV receiver as claimed in claim 1 is characterized in that:
Above-mentioned DC remover was preferably walked around the Q signal of frequency mixer reception (bypass) the above-mentioned the 2nd low territory and is passed through filter before the Frequency Synchronization of carrier synchronization forms.
3, the carrier centering device of DTV receiver as claimed in claim 1 is characterized in that, also comprises:
The phase error that above-mentioned multiplier generates is filtered the recursive filter of accumulative total;
Ratio according to above-mentioned recursive filter output generates complex carrier, to the complex oscillation device of above-mentioned frequency mixer feedback.
4, the carrier centering device of DTV receiver as claimed in claim 1 is characterized in that:
For the I signal with above-mentioned pilot component correctly is transformed into the DC composition, above-mentioned delayer postpones certain hour with the I signal of pilot component.
5, the carrier centering device of DTV receiver as claimed in claim 1 is characterized in that, above-mentioned DC remover also comprises:
Remove the subtracter of the DC inferred value that moves the Q signal that moves signal demodulator from the Q signal of frequency mixer reception;
Extract the accumulator of residual DC components in the output signal of above-mentioned subtracter out;
Calculate the DC inferred value of Q signal from above-mentioned residual DC components, to the multiplier of above-mentioned subtracter feedback.
6, the carrier centering device of DTV receiver as claimed in claim 5 is characterized in that:
Above-mentioned multiplier is taken advantage of from the residual DC value of above-mentioned accumulator output and is calculated the step amplitude, calculates the DC inferred value of Q signal.
7, the carrier centering device of DTV receiver as claimed in claim 6 is characterized in that:
Above-mentioned step amplitude is big more, and the coalescence rate of DC remover is fast more, and the residual DC value of normal condition increases; The step amplitude is more little, and the residual DC value reduces, and the coalescence rate of DC remover is slack-off.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB200410084330XA CN100542150C (en) | 2004-11-18 | 2004-11-18 | The carrier centering device of DTV receiver |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB200410084330XA CN100542150C (en) | 2004-11-18 | 2004-11-18 | The carrier centering device of DTV receiver |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1780274A true CN1780274A (en) | 2006-05-31 |
| CN100542150C CN100542150C (en) | 2009-09-16 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB200410084330XA Expired - Fee Related CN100542150C (en) | 2004-11-18 | 2004-11-18 | The carrier centering device of DTV receiver |
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| Country | Link |
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| CN (1) | CN100542150C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110082746A (en) * | 2018-01-25 | 2019-08-02 | 株式会社东芝 | Range unit and distance measuring method |
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2004
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110082746A (en) * | 2018-01-25 | 2019-08-02 | 株式会社东芝 | Range unit and distance measuring method |
| CN110082746B (en) * | 2018-01-25 | 2023-06-09 | 株式会社东芝 | Distance measuring device and distance measuring method |
Also Published As
| Publication number | Publication date |
|---|---|
| CN100542150C (en) | 2009-09-16 |
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