CN101867740B - Sampling rate converter and conservation method for digital television baseband signals - Google Patents
Sampling rate converter and conservation method for digital television baseband signals Download PDFInfo
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Abstract
The invention discloses a sampling rate converter and a sampling rate conversion method for digital television baseband signals. The sampling rate converter comprises a data extraction module, a spectrum formation module, a ratio detection module, a ratio search module, an interpolation control module, an interpolation filter module and a regular locking detection module. In the invention, interpolation factors of the interpolation filter module are adjusted by adjusting the proportional value of a total bandwidth and a signal bandwidth, judgment is carried by the regular locking detection module, and finally, sampling frequencies are converted into symbolic frequencies. The conversion effect is good.
Description
Technical field
The present invention relates to a kind of Digital Signal Processing, particularly a kind of baseband signal sample rate converter and conversion method for the Digital TV Receiving field.
Background technology
Along with developing by leaps and bounds of information and digital technology, TV is just stepping into the total digitalization epoch.Digital Television has that efficiency of transmission is high, signal quality is high and the advantages such as antijamming capability is strong.QAM (QuadratureAmplitude Modulation, quadrature amplitude modulation) modulation system is generally adopted in the transmission of Digital Television.In the demodulating system of these systems, need to utilize the data that receive to realize sign synchronization.To be a kind of clock that makes receiver keep the method for synchronizeing with transmitter clock to sign synchronization.
The high-frequency signal that data receiver receives becomes analog intermediate frequency signal through tuner, and analog intermediate frequency signal becomes digital little intermediate-freuqncy signal after changing through A/D, then by carrier recovery block, the little intermediate-freuqncy signal of numeral is become baseband signal.Because the sampling clock of the sampling clock of transmitting terminal and receiving terminal is inconsistent, causing the sampling rate of baseband signal and character rate is not the integral multiple relation, so need to be character rate with the sample rate conversion of baseband signal.
Summary of the invention
In view of this, being necessary to provide a kind of can be sample rate converter and the sample rate conversion method of character rate with the sample rate conversion of digital television baseband signals.
The sample rate converter that is used for digital television baseband signals that the present invention proposes comprises:
Data extraction module is used under the control of extracting multiple, the digital baseband signal of inputting evenly being extracted;
Frequency spectrum forms module, is used for collecting N point from the digital baseband signal of described data extraction module output, each point is done discrete Fourier transform exports discrete spectrum, with data transaction to frequency domain, the bandwidth that finds signal to occupy on frequency domain;
The ratio detection module, ratio value for detection of frequency spectrum total bandwidth and signal bandwidth, and according to the corresponding relation of this ratio value and extracting multiple, reset the extracting multiple of described data extraction module, and data extraction module is reset the ratio value that obtains after extracting multiple as the initial proportion value;
The ratio search module, be used for scanning traversal near the frequency spectrum ratio value that ratio detects, and the method for search is " Z " font, and near the rule that namely replaces with the left and right ratio value that detects outwards enlarges search gradually, until find a correct ratio value;
The interpolation control module is used for the search percent information is added up, output interpolation factor and data enable signal;
The interpolation filtering module is used for according to interpolation factor, data extraction module is established the data of exporting after extracting multiple again carry out the conversion of sampling rate;
Timely lock detection module, be used for determining according to data enable signal whether the data of interpolation filtering module output are effective, and active data is timely locked detection, when being judged to be non-locking, send the control signal that continues next ratio value of search to described ratio search module, when being judged to be locking, sample rate conversion is completed.
The present invention also proposes a kind of sample rate conversion method for digital television baseband signals, comprises the following steps:
A receiving digital television baseband signal evenly extracts the digital baseband signal of input under the control of extracting multiple;
B collects N point from the digital baseband signal of data extraction module output, each point is done discrete Fourier transform exports discrete spectrum, with data transaction to frequency domain, the bandwidth that finds signal to occupy on frequency domain;
C detects the ratio value of frequency spectrum total bandwidth and signal bandwidth, and according to the corresponding relation of this ratio value and extracting multiple, reset the extracting multiple of described data extraction module, and data extraction module is reset the ratio value that obtains after extracting multiple as the initial proportion value;
D scans traversal near the frequency spectrum ratio value that ratio detects, and the method for search is " Z " font, and near the rule that namely replaces with the left and right ratio value that detects outwards enlarges search gradually, until find a correct ratio value;
E adds up to the search percent information, and output interpolation factor and data enable signal;
F establishes with data extraction module the data of exporting after extracting multiple again and carries out the conversion of sampling rate according to interpolation factor;
G determines according to data enable signal whether the data of interpolation filtering module output are effective, and active data is timely locked detection, when being judged to be non-locking, send the control signal that continues next ratio value of search to described ratio search module, when being judged to be locking, sample rate conversion is completed.
Sample rate converter provided by the invention is adjusted the interpolation factor of interpolation filtering module by the ratio value of adjusting total bandwidth and signal bandwidth, recycling timely locks detection module and judges, finally complete sample frequency and convert symbol frequency to, conversion effect is good.
Description of drawings
The present invention is described in detail below in conjunction with embodiment and accompanying drawing, wherein:
Fig. 1 is the structured flowchart of the sample rate converter that proposes of the present invention;
Fig. 2 is that the ratio in the present invention detects schematic diagram;
Fig. 3 is that the extracting multiple in the present invention is selected flow chart;
Fig. 4 is the schematic diagram of the search ratio value obtain manner in the present invention;
Fig. 5 is the schematic diagram of the interpolation control module in the present invention;
Fig. 6 is the schematic diagram of the interpolation filtering construction module in the present invention;
Fig. 7 is the schematic diagram that timely locks detection module in the present invention.
Embodiment
See also Fig. 1, the sample rate converter 100 that the present invention proposes comprises that a data abstraction module 101, frequency spectrum form module 102, ratio detection module 103, ratio search module 104, interpolation control module 105, interpolation filtering module 106 and one and timely lock detection module 107.
Described data extraction module 101 is used for receiving digital baseband signal, and its default initial value is 1 extracting multiple.When extracting multiple was initial value, described data extraction module 101 was exported to described frequency spectrum with data and is formed module 102; When extracting multiple was arranged again, data are exported to described interpolation filtering module 106 to described data extraction module 101 simultaneously and described frequency spectrum forms module 102.Certainly, described data extraction module 101 also can all be exported to data described interpolation filtering module 106 before and after extracting multiple changes, but this moment, described interpolation filtering module 106 needed to judge whether data extraction module 101 is to send for the first time digital baseband signal, sends for the first time digital baseband signal will not receive if be judged as.The initial value of described data extraction module 101 is 1, and expression is not extracted digital baseband signal first.
Described frequency spectrum forms module 102 and is used for collecting a plurality of points from the digital baseband signal of described data extraction module 101 outputs, each point is done the discrete spectrum that discrete Fourier transform obtains data, and export to described ratio detection module 103.In present embodiment, described frequency spectrum forms module 102 and collects 128 points.Certainly, described frequency spectrum forms module 102 and also can collect 256 or 512 points.
In present embodiment, the total bandwidth of the discrete spectrum of described frequency spectrum formation module 102 outputs and the ratio value for the first time of signal bandwidth are made as and do not extract ratio value.See also Fig. 2, form total number of discrete spectrum point of discrete spectrum of module 102 outputs take described frequency spectrum as 128, it is example that signal discrete frequency spectrum point is 30.The shared bandwidth of A representation signal wherein, i.e. the bandwidth of the character rate of signal, B represents total bandwidth, i.e. the bandwidth of sampling rate.The unit of this bandwidth represents with the number of discrete spectrum point, and the width of A has occupied 30 discrete spectrum points, and the bandwidth that claims signal is 30; Due to the discrete Fourier transform of having adopted at 128, so total bandwidth is 128.The not extraction ratio value that described ratio detection module 103 calculates is 128/30.
See also Fig. 3, this is not extracted ratio value be defined as p.The interior default a plurality of piecewise intervals of described ratio detection module 103.Because satisfy nyquist sampling theorem, so sampling rate is at least the twice of character rate, so the value of p necessarily greater than 2, and integral multiple that neither character rate in present embodiment.In present embodiment, the piecewise interval of described ratio detection module 103 comprises 2＜p＜4,4＜p＜6,6＜p＜9,9＜p＜12,12＜p＜15 etc.When 2＜p＜4, the extracting multiple that described ratio detection module 103 arranges described data extraction module 101 is 1, and expression is not extracted data.When 4＜p＜6, the extracting multiple that described ratio detection module 103 arranges described data extraction module 101 is 2, namely gets a point as effectively exporting and being even output in every two points; When 6＜p＜9, the extracting multiple that described ratio detection module 103 arranges described data extraction module 101 is 3; When 9＜p＜12, the extracting multiple that described ratio detection module 103 arranges described data extraction module 101 is 4; When 12＜p＜15, the extracting multiple that described ratio detection module 103 arranges described data extraction module 101 is 5, by that analogy.
In present embodiment, after described ratio detection module 103 arranges the extracting multiple of described data extraction module 101, make described data extraction module 101 carry out extraction operation.Data after described data extraction module 101 will extract are exported to described frequency spectrum and are formed module 102 and interpolation filtering module 106.Described frequency spectrum forms module 102 and described ratio detection module 103 operates according to the data of described data extraction module 101 outputs again, obtains described initial proportion value.Increase to some extent because account for the proportion of total bandwidth through inromation bandwidth after extracting, so the initial proportion value that the data after extracting through data extraction module 101 calculate than the not extraction ratio value that calculates for the first time more accurately.Described ratio detection module 103 is exported to ratio search module 104 with the initial proportion value, as shown in Figure 1.
Described ratio search module 104, for increasing a step value as the search ratio value, when increasing first, the initial proportion value is increased a step value, when again increasing, the search ratio value of last time is increased by a step value, and this step value and the last step value sign opposite in sign that increases, the many step-lengths of the step value of the more last increase of size.See also Fig. 4, the residing position of positional representation initial proportion value of the described longitudinal axis, label is that 1 point represents the ratio value after the initial proportion value increases a step value, namely searches for ratio value; Label is that 2 point represents the ratio value after first search ratio value increases a step value, and label is that 3 point represents the ratio value after second search ratio value increases a step value.In present embodiment, this step value is followed successively by 1, and-2,3 ,-4,5 ,-6,7 ,-8.
Interpolation filtering module 106 is used for according to interpolation factor, data extraction module 101 being established the data of exporting after extracting multiple again and carries out the conversion of sampling rate.In present embodiment, described interpolation filtering module 106 adopts the sectional parabola interpolater, and as shown in Figure 6, certainly, described interpolation filtering module 106 can also be triangle interpolater, cubic interpolation device etc.
Timely locking detection module 107 is used for determining according to data enable signal whether the data of interpolation filtering module 106 outputs are effective, and active data is timely locked detection, when being judged to be non-locking, send the control signal that increases the ratio value step-length to described ratio search module 104, when being judged to be locking, sample rate conversion is completed.In present embodiment, the described structure that timely locks detection as shown in Figure 7.Described timely lock detection module 107 former and later two data of the data after interpolation are remake after first square respectively poor, 2000 differences are added up try to achieve mean value and lock-in threshold comparison, if this value higher than lock-in threshold illustrate the search ratio value correct, with sampled data rate transition to 2 times character rate, sampling rate is locked for described interpolation filtering module 106.If this value is lower than lock-in threshold search ratio value mistake is described, sampling rate is not locked, the simultaneously described detection module 107 that timely locks sends the control signal that increases the ratio value step-length to described ratio search module 104, described ratio search module 104 will generate new search ratio value after receiving control signal.
See also Fig. 8, be the flow chart of sample rate conversion method, concrete steps are as follows:
Step S110: receive digital baseband signal.In present embodiment, utilize described data extraction module 101 to receive digital baseband signal.
Step S112: collect N point from the digital baseband signal that receives, each point is done the discrete spectrum that discrete Fourier transform obtains data.In present embodiment, described data extraction module 101 does not extract digital baseband signal for the first time, directly the digital baseband signal that receives is transferred to frequency spectrum and forms module 102.Described frequency spectrum forms 128 points that module 102 is collected in digital baseband signal, and each point is done the discrete spectrum that discrete Fourier transform obtains data.Certainly, described frequency spectrum forms module 102 and also can collect 256 or 512 points.
Step S114: calculate the total bandwidth of discrete spectrum in discrete spectrum and the ratio value of signal bandwidth, and obtain extracting multiple corresponding to ratio value according to default ratio value with the corresponding relation of extracting multiple.In present embodiment, utilize described ratio detection module 103 to calculate the ratio value of total bandwidth and signal bandwidth in discrete spectrums, the position in piecewise interval arranges the extracting multiple of described data extraction module 101 according to ratio value for the interior default piecewise interval of described ratio detection module 103, described ratio detection module 103.
Step S116: digital baseband signal is extracted according to the extracting multiple that resets.In present embodiment, described abstraction module 101 extracts digital baseband signal according to the extracting multiple that described ratio detection module 103 arranges.
Step S118: collect a plurality of points the digital baseband signal after extracting, each point is done the discrete spectrum that discrete Fourier transform obtains data.This step and step S112 are basic identical, and difference is to process is digital baseband signal after extracting.
Step S120: the total bandwidth of the discrete spectrum of the digital baseband signal after calculating is extracted and the ratio value of signal bandwidth are as the initial proportion value.Described ratio detection module 103 obtains described initial proportion value according to the discrete spectrum of the digital baseband signal after extracting.
Step S122: described initial proportion value is increased by a step value as the search ratio value.In present embodiment, described ratio search module 104 increases by a step value with the initial proportion value and obtains searching for ratio value, and will search for ratio value and export to described interpolation control module 105.
Step S124: obtain data enable signal and interpolation factor according to the search ratio value.In present embodiment, the ratio value input interpolation control module 105 of described ratio search module 104 outputs first multiplies each other with 0.5, the result that multiplies each other and 1 is subtracted each other, result after subtracting each other is added up, when reaching 1, accumulated value exports the data enable invalid signals to the described detection module 107 that timely locks, the data that represent current described interpolation filtering module 106 interpolation outputs are invalid, and deduct a sampled point; Otherwise output data enable useful signal.The result that accumulated value removes after integer part is called interpolation factor, exports to interpolation filtering module 106.
Step S126: according to interpolation factor, according to interpolating method, the digital baseband signal that extracts is carried out the conversion of sampling rate.In present embodiment, utilize the sectional parabola interpolater according to interpolation factor, the digital baseband signal after extracting to be carried out the conversion of sampling rate.
Step S128: judge whether data enable signal is effective, described what timely lock described interpolation control modules 105 outputs of detection module 107 judgement is data enable useful signal or data enable invalid signals.
Step S130: when enabling useful signal, utilize to timely lock detection method and judge that can the sampling rate of conversion locked when data enable signal.In present embodiment, when described timely lock described interpolation control modules 105 outputs of detection module 107 judgement be the data enable useful signal time, it is poor that former and later two data of data after described interpolation filtering module 106 interpolations are remake after first square respectively, 2000 differences are added up try to achieve mean value and lock-in threshold comparison, if this value higher than lock-in threshold illustrate the search ratio value correct, with sampled data rate transition to 2 times character rate, sampling rate is locked for described interpolation filtering module 106; Otherwise search ratio value mistake, sampling rate is not locked.
Step S132: when sampling rate is judged as non-locking, described search ratio value is increased by a step value, forward to according to the search ratio value and obtain in the step of data enable signal and interpolation factor.In present embodiment, described ratio search module 104 will be searched for the step value that ratio value increases a sign opposite direction, and the size of this step value forwards step 124 to than step-length of step value increase last time.
In step S128,, return to step S124 and again obtain data enable signal when enabling invalid signals when the data enable signal of judging.In step S130, when utilization timely locked detection method and judges that the sampling rate of conversion can be locked, sample rate conversion was completed.
Sample rate converter provided by the invention is adjusted the interpolation factor of interpolation filtering module by the ratio value of adjusting total bandwidth and signal bandwidth, recycling timely locks detection module and judges, thereby can be so that the interpolation filtering module can convert sample frequency to symbol frequency.
Be to be understood that, for the person of ordinary skill of the art, can make other various corresponding changes and distortion by technical conceive according to the present invention, and all these change and distortion all should belong to the protection range of claim of the present invention.
Claims (10)
1. sample rate converter that is used for digital television baseband signals is characterized in that comprising:
Data extraction module is used under the control of extracting multiple, the digital baseband signal of inputting evenly being extracted;
Frequency spectrum forms module, is used for collecting N point from the digital baseband signal of described data extraction module output, each point is done discrete Fourier transform exports discrete spectrum, with data transaction to frequency domain, the bandwidth that finds signal to occupy on frequency domain;
The ratio detection module, ratio value for detection of frequency spectrum total bandwidth and signal bandwidth, and according to the corresponding relation of this ratio value and extracting multiple, reset the extracting multiple of described data extraction module, and data extraction module is reset the ratio value that obtains after extracting multiple as the initial proportion value;
The ratio search module, for increasing a step value as the search ratio value, when increasing first, the initial proportion value is increased a step value, when again increasing, the search ratio value of last time is increased by a step value, and this step value and the last step value sign opposite in sign that increases, the many step-lengths of the step value of the more last increase of size; And the method for search is " Z " font, and near the rule that namely replaces with the left and right ratio value that detects outwards enlarges search gradually, until find a correct ratio value;
The interpolation control module is used for the search percent information is added up, output interpolation factor and data enable signal;
The interpolation filtering module is used for according to interpolation factor, data extraction module is established the data of exporting after extracting multiple again carry out the conversion of sampling rate;
Timely lock detection module, be used for determining according to data enable signal whether the data of interpolation filtering module output are effective, and active data is timely locked detection, when being judged to be non-locking, send the control signal that continues next ratio value of search to described ratio search module, when being judged to be locking, sample rate conversion is completed.
2. the sample rate converter for digital television baseband signals as claimed in claim 1, it is characterized in that: when initial extracting multiple is set as 1, described data extraction module is directly exported to described frequency spectrum with data and is formed module, when extracting multiple was arranged again, data are exported to described interpolation filtering module to described data extraction module simultaneously and described frequency spectrum forms module.
3. the sample rate converter for digital television baseband signals as claimed in claim 1, it is characterized in that: default piecewise interval in described ratio detection module, described ratio detection module is according to the extracting multiple that does not extract the position of ratio value in piecewise interval and arrange described data extraction module; Described total bandwidth that ratio value is the described frequency spectrum discrete spectrum that forms module output and the ratio value for the first time of signal bandwidth of not extracting.
4. the sample rate converter for digital television baseband signals as claimed in claim 1, it is characterized in that: in described ratio detection module, the unit of bandwidth represents with the number of discrete spectrum point.
5. the sample rate converter for digital television baseband signals as claimed in claim 1, is characterized in that, described interpolation filtering module adopts the sectional parabola interpolater.
6. a sample rate conversion method that is used for digital television baseband signals, is characterized in that comprising the following steps:
A receiving digital television baseband signal evenly extracts the digital baseband signal of input under the control of extracting multiple;
B collects N point from the digital baseband signal of data extraction module output, each point is done discrete Fourier transform output discrete spectrum, and be converted to frequency domain, the bandwidth that finds signal to occupy on frequency domain;
C detects the ratio value of frequency spectrum total bandwidth and signal bandwidth, and according to the corresponding relation of this ratio value and extracting multiple, reset the extracting multiple of described data extraction module, and data extraction module is reset the ratio value that obtains after extracting multiple as the initial proportion value;
D increases a step value as the search ratio value, when increasing first, the initial proportion value is increased a step value, when again increasing, the search ratio value of last time is increased by a step value, and this step value and the last step value sign opposite in sign that increases, the many step-lengths of the step value of the more last increase of size; And the method for search is " Z " font, and near the rule that namely replaces with the left and right ratio value that detects outwards enlarges search gradually, until find a correct ratio value;
E adds up to the search percent information, and output interpolation factor and data enable signal;
F establishes with data extraction module the data of exporting after extracting multiple again and carries out the conversion of sampling rate according to interpolation factor;
G determines according to data enable signal whether the data of interpolation filtering module output are effective, and active data is timely locked detection, when being judged to be non-locking, send the control signal that continues next ratio value of search to the ratio search module, when being judged to be locking, sample rate conversion is completed.
7. the sample rate conversion method for digital television baseband signals as claimed in claim 6, it is characterized in that: in step e,, forward to according to the search ratio value and obtain in the step of data enable signal and interpolation factor when enabling invalid signals when data enable signal.
8. the sample rate conversion method for digital television baseband signals as claimed in claim 6, it is characterized in that: when initial extracting multiple is set as 1, described data extraction module is directly exported to described frequency spectrum with data and is formed module, when extracting multiple was arranged again, data are exported to described interpolation filtering module to described data extraction module simultaneously and described frequency spectrum forms module.
9. the sample rate conversion method for digital television baseband signals as claimed in claim 6, it is characterized in that: the unit of described total bandwidth and signal bandwidth represents with the number of discrete spectrum point.
10. the sample rate conversion method for digital television baseband signals as claimed in claim 6, is characterized in that: in step f, use the sectional parabola interpolater to carry out the conversion of sampling rate.
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| ES2221570B2 (en) * | 2003-05-30 | 2005-10-01 | Diseño De Sistemas En Silicio, S.A. | REMEDY PROCEDURE IN TRANSMISSION AND RECEPTION OF A DIGITAL SIGNAL WITH TRANSFER IN DIGITAL BAND. |
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| US5878088A (en) * | 1997-04-10 | 1999-03-02 | Thomson Consumer Electronics, Inc. | Digital variable symbol timing recovery system for QAM |
| CN1365207A (en) * | 2001-01-09 | 2002-08-21 | 深圳市中兴集成电路设计有限责任公司 | A digital baseband filter |
| CN1658658A (en) * | 2004-02-19 | 2005-08-24 | 乐金电子（沈阳）有限公司 | Digital TV. receiver |
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