CN1845538B - Time-domain channel synchronous tracker - Google Patents
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- CN1845538B CN1845538B CN2005100654590A CN200510065459A CN1845538B CN 1845538 B CN1845538 B CN 1845538B CN 2005100654590 A CN2005100654590 A CN 2005100654590A CN 200510065459 A CN200510065459 A CN 200510065459A CN 1845538 B CN1845538 B CN 1845538B
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Abstract
The disclosed time-domain channel synchronous tracker comprises a signal resampling module, a center indicator for equalizer with output signal from last module as its input, a channel correlation estimator with input and output connected to output of resampling module and the analyzer input respectively, a large/small-step synchronous regulation controller, a channel information analyzer, and a signal superimposer to process signals from two controller. This invention improves capacity to anti multi-path signal.
Description
Technical field
The present invention relates to a kind of time domain channel tracker,,, become multipath effect when playing antagonism, belong to synchronization channel estimation and adaptive equalization technique field in conjunction with improved time domain linear balancing technique by the time domain of channel being estimated and being followed the tracks of synchronously.
Background technology
In the practical application of many different digital informations such as sound, data and video communication etc., equalizer is a kind of very important element.Equalizer is used as the Echo Canceller of speakerphone in the full-duplex communication or video anti-ghost device, radio modem and the wireless telephonic signal conditioner etc. in compensator, Digital Television or the digital cable transmission.In signals transmission, the existence of multipath signal can bring intersymbol interference (ISI) in the channel, and intersymbol interference is a major reason that produces error.In most of single carrier digital application, generally all use time-domain adaptive equalizer to revise the ISI mistake.
In signals transmission, because moving of peripheral reflection thing and moving of reception or transmitting station, make the size of each reflection echo, direction and time delay are all along with the time, variation took place, be that variation has taken place in transmission course channel over time, be commonly referred to the Doppler effect in the transmission.
When channel takes place, becoming, traditional time-domain adaptive equalizer can't be followed the tracks of the main footpath signal of variation, thereby the multipath effect that becomes in the time of can't resisting, and the time domain linear equalizer with virtual center need not the fixing main footpath signal of following the tracks of becomes possibility thereby become multipath effect when making antagonism.Because the length of equalizer itself is limited, need multipath signal better be covered by equalizer by the equalizer virtual center rationally is set, thereby improve the ability that equalizer resists multipath signal; Simultaneously, equalizer dynamic tracking ability also is limited, needs to become the multipath signal ability when improving the equalizer antagonism by timely estimation and the dynamic position of adjusting virtual center to channel.
Summary of the invention
The object of the present invention is to provide a kind of time-domain channel synchronous tracker.This time-domain channel synchronous tracker is by estimating to follow the tracks of the variation of dynamic multi-path to channel synchronization, can help to determine the virtual center of equalizer, variation according to channel resamples to signal, dynamically adjust the position of multipath signal with respect to virtual center, multipath signal is optimally covered by adaptive equalizer, thus best antagonism dynamic multi-path channel.
The present invention seeks to be achieved through the following technical solutions:
Time-domain channel synchronous tracker provided by the present invention comprises that signal resampling module, equalizer center tester, the relevant estimator of channel, big step-length are adjusted controller synchronously, little step-length is adjusted controller, channel information analyzer and signal superimposer synchronously.The signal that is input as the output of signal resampling module of equalizer center tester, the input of the relevant estimator of channel is connected with the output of signal resampling module, the output of the relevant estimator of channel and the input of channel information analyzer are connected, the output of channel information analyzer is adjusted controller synchronously with big step-length simultaneously, the input that little step-length is adjusted controller and equalizer center tester synchronously is connected, big step-length is adjusted controller and little step-length synchronously and is adjusted the step-length of controller output synchronously and adjust signal and export signal resampling module to by the stack of signal superimposer, and described signal resampling module is controlled by the adjustment step-length of input.
Signal resampling module is finished input analog signal R is sampled, and obtains digital signal T; The relevant estimator of channel is finished the estimation to the channel information parameter; The equalizer center tester, output result according to the channel information analyzer, dynamically adjust the position of multipath signal, thereby make that this kind equalizer can the adaptive variation along with channel variation with respect to the virtual center of " adaptive equalizer " with virtual center; Big step-length is adjusted controller synchronously, according to the analysis result of channel information analyzer, finishes the synchronous tracking Control of big step-length to channel; Little step-length is adjusted controller synchronously, according to the analysis result of channel information analyzer, finishes the synchronous tracking Control of little step-length to channel.
Digital sampled signal T is as the input of relevant estimator of channel and equalizer center tester, the output H of the relevant estimator of channel is the input that channel information analyzer and little step-length are adjusted controller synchronously, channel information analyzer output control information C is that equalizer center tester, big step-length are adjusted the input that controller and little step-length are adjusted controller synchronously synchronously, and channel information analyzer output step-length control information L adjusts controller for big step-length synchronously.Big step-length adjusts controller output S1 synchronously and little step-length is adjusted controller output S2 synchronously, adds and produce step length command signal S to control or resampler to VCXO, and the output signal of equalizer center tester is data-signal 0 and control signal I.Digital signal T is the data complex signal after sampling, digital signaling zero is a signal of exporting to equalizer, and digital signal C, G, I are the Boolean type control signal, are used to indicate the state of control, digital signal H, S1, S2, S, L are the data type control signal, are used to indicate the size of concrete control.
Signal resampling module can be made of an A/D sampler and a VCXO, input analog signal R enters the A/D sampler, the A/D sampler generates digital sampled signal T under the control of VCXO, the output of signal superimposer at this moment is connected to the VCXO of signal resampling module; Signal resampling module can also be made of an A/D sampler, a fixed crystal oscillator and a signal resampler, the A/D sampler is subjected to the control of fixed crystal oscillator, input analog signal R is by entering signal resampler again behind the A/D sampler, obtain digital sampled signal T, the output of signal superimposer at this moment is connected to the fixed crystal oscillator of signal resampling module.
Described signal resampler comprises an addition and controller, two interpolaters, a data Strobe Controller and three delay units.Three outputs of addition and controller are connected with three delay units respectively, and the output of two delay units is connected with interpolater, and the output of the output of another delay unit and two interpolaters is linked and connect the data strobe controller.The step change amount that the is input as Δ u of addition and controller, addition and controller obtain step-length output u to Δ u modulo operation; Interpolater is finished the interpolative operation of data, and the size according to step-length output u resamples to data, and interpolater can be the interpolater of sinusoidal structured, also can be the interpolater of Farrow structure; The data strobe controller is according to the signal after the output decision output resampling of interpolater and addition and controller.
The relevant estimator of channel comprises two channel correlators, two squarers, a signal superimposer and an energy converging filter.Two inputs of channel correlators are respectively the in-phase component II and the quadrature component IQ of sampled signal, channel correlators is output as the input of squarer, the squarer of homophase road signal and positive cross-channel signal is output as the input of signal superimposer, the signal superimposer is output as the input of energy converging filter, and the output of energy converging filter is the output of channel correlators.
Described channel correlators is the time-domain signal correlator, by the relevant time domain impulse response that obtains channel of preamble word or other predetermined sequences; Squarer carries out square operation to signal, to eliminate the influence of phase deviation; The signal superimposer sums up computing to signal; The energy converging filter carries out matching aggregation to signal correction estimated energy signal.
Channel correlators is utilized preamble word or other Given informations in the transmission signals, input signal is carried out asynchronous related operation, consider that The noise carries out Threshold detection to relevant output, surpass of the time domain impulse response of the response numerical value of thresholding as channel, wherein correlator can be the correlator of integral multiple, also can be the correlator of branch several times.As: the M sequence of " PN255+0 " adopts the BPSK mapping at diagonal angle to obtain 256 symbols, for with these 256 symbols as preamble word, 1024 symbols frame structure as data, it is asynchronous relevant that channel correlators selects for use these 256 symbols to do, again the output thresholding of correlator is selected, to the correlation that surpasses thresholding as the channel time domain impulse response.
Described energy converging filter, its filter construction are a FIR filter, and described filter can superpose to signal, and this filter coefficient requires and the correlator output signal is complementary.Consider that correlator is the relevant of quadratic sum, this filter coefficient should be the SINC function square.In addition, consider the problem that hardware is realized, this filter coefficient can be reduced to the shape of " broad in the middle, narrowing toward each end ", as coefficient models such as the filter coefficient of triangular form, semi-circular filter coefficient or parabolical filter coefficients.
The channel information analyzer comprises an information detector, an area dividing device, a regional peak detector, a State Control machine and a direction confidence counter.The input signal of information detector is a channel estimating information, information detector is output as the input of area dividing device, the area dividing device is output as the input of regional peak detector, the zone peak detector is output as the input of State Control machine, and the State Control machine is output as the input of direction confidence counter.
Described information detector is finished the relevant estimator estimated channel information of channel is detected, and finds the regional location at information place, for the work of area dividing device is prepared; The area dividing device, the channel information that information detector is found carries out the division on the time zone; The zone peak detector extracts the channel information in the zones of different, finds out size and the relative position and the output of correlation largest peaks in this zone; The State Control machine is triggering with the size and the position of peak value in each zone of regional peak detector output, is mechanism with the workflow diagram of state machine, the adjustment operating state; The direction confidence counter is by the control information that letter finally produces output of putting to control signal.
Described information detector is finished from the information of the relevant estimator output of channel and is detected the channel information that will analyze, comprises a threshold detector, positional information counter and a confidence counter.As frame structure for above-mentioned " 256 preamble word+1024 data ", the relevant estimator estimated channel information of channel is the time domain impulse response of channel, this time domain impulse response meeting occurred according to the situation cycle of frame structure, per 1280 symbols occur once, information detector at first carries out Threshold detection to correlation, surpass thresholding then confidence counter begin counting, add 1 when then counting appears again in the situation that surpasses thresholding every 1280 symbols, otherwise subtract 1, threshold value is that 0 o'clock information detector resets, put the letter number if confidence counter surpasses thresholding, such as 6, then the position of perch channel information is found.By the method that this kind put letter, information detector is finished the detection to channel information.
Described State Control machine, for the state between several states is coordinated controller, output result according to area dividing device and regional peak detector, the variation of dynamic debugging system state, export control signal simultaneously and give confidence counter, control signal is+1 ,-1 or 0 Boolean type signal, wherein+1 is designated as big step-length and accelerates sampling rate,-1 is designated as the big step-length sampling rate that slows down, and 0 for not doing big step-length adjustment.
The direction that described direction confidence counter determine to be adjusted, the variation that prevents to adjust direction is too frequent, and counter is to being continuously positive situation or being continuously negative situation counting, when counting satisfies certain thresholding, outbound course control signal then.
Big step-length is adjusted the big step-length of controller ground synchronously and is adjusted the position of data in equalizer, and multipath signal is optimally covered by equalizer, thereby strengthens the ability of equalizer antagonism multipath signal.Big step-length is adjusted controller according to the control signal C of channel information analyzer output and the concrete numerical value of L, produces step-length and adjusts signal S1.The symbol decision of S1 is accelerated or the sampling rate that slows down, and step-length is adjusted the size of the concrete numerical value decision sampling rate adjustment of signal.The symbol of S1 is according to the decision of the symbol of control signal C, the concrete numerical value of S1 is by adopting suitable weighting to decide to L, and the process that requires to change is level and smooth change procedure, and promptly the first derivative of weighting function is continuous, the method of weighting has a lot, as adopting y=x
3Method of weighting.L is big more, and S1 is just big more, and the speed of " pulling " is just fast more; L is more little, and S1 is just more little, and the speed of " pulling " is just slow more, and purpose is to finish one continual, level and smooth, progressive " pulling ".
Little step-length is adjusted controller synchronously and is comprised a channel frequency discrimination filter and a loop filter.The control information of the channel estimating information that is input as of channel frequency discrimination filter and the output of channel information analyzer, the control information of the output of channel frequency discrimination filter and the output of channel information analyzer is the input of loop filter, and loop filter is output as the long control information of small step.
The filter that described channel frequency discrimination filter is a FIR structure and a data gate, the output result of filter is input in the data strobe device, data strobe device according to the output of the control information decision filter of channel information analyzer output whether as the output of channel frequency discrimination filter, thereby make filter finish the frequency discrimination filter function of a kind of " photographic means ".The central area size that the length of filter is divided for the area dividing device, the tap coefficient model of filter is the odd symmetric model in center, the i.e. model on " both sides big, middle little ", the filter tap coefficients model can be the first-order linear function type, perhaps positive cotangent function type or parabolic function type.
Described loop filter is the structure of the active proportional integral low pass filter of second order, and concrete coefficient calculates according to the loop formula.
The time-domain channel synchronous tracker of the present invention's design, by channel synchronization being estimated to follow the tracks of the variation of dynamic multi-path, can help to determine the virtual center of equalizer, signal be resampled, dynamically adjust the position of multipath signal with respect to virtual center according to the variation of channel.Along with the variation of multipath signal, the present invention adopts uniting of big step-length and little step-length to adjust and realizes " pulling " of multipath signal, thereby makes multipath signal optimally be covered by equalizer, has improved the ability of equalizer antagonism multipath signal.
Description of drawings
Fig. 1 is a channel synchronous tracker construction module block diagram of the present invention.
Fig. 2 is a first embodiment of the invention channel architecture module frame chart.
Fig. 3 is a second embodiment of the invention channel architecture module frame chart.
Fig. 4 is the functional block diagram of signal resampler.
Fig. 5 is the construction module block diagram of Farrow interpolater.
Fig. 6 is the relevant estimator functionality module frame chart of channel.
Fig. 7 is an energy converging filter examples coefficient sketch.
Fig. 8 is a channel information analyser function module frame chart.
Fig. 9 adjusts the controller function module frame chart synchronously for little step-length.
Figure 10 is a channel information analyser function example sketch.
Figure 11 is the state machine control flow chart.
Figure 12 is a channel frequency discrimination filter coefficient example sketch.
Figure 13 is the loop filter structure module frame chart.
Figure 14 adjusts control weighting example (y=x synchronously for big step-length
3).
Figure 15 adjusts control example sketch synchronously for little step-length.
Embodiment
With the digital television ground broadcast transmission system is application example.This system makes a start and adopts the single-carrier modulated mode, and the frame structure of transmission frame is the structure of " preamble word+data ", and wherein preamble word is the M sequence of " PN255+0 ", mapping mode is the BPSK mode at diagonal angle, that is, 0 is mapped as (4.5,4.5), 1 is mapped as (4.5 ,-4.5); Data are transmission information and system information through coding protection, and length is 1024 symbols, and mapping mode is the 4QAM mode.In order to resist the abominable channel situation under the terrestrial broadcasting environment, the signal that promptly receives is the stack of various reflected waves, and in order to realize high-quality mobile reception, system adopts " a kind of time-domain adaptive equalizer with virtual center " simultaneously.Channel synchronous tracker of the present invention utilizes preamble word to do channel estimating, obtains the channel information of dynamic channel, adjusts multipath signal by control resampler or A/D sampler, makes being covered by equalizer of multipath signal optimum.
Analog signal R becomes digital signal T behind over-sampling, digital signal T is the restituted signal of QAM, sample rate is 2 times of symbol rate, restituted signal resamples (also can resample by the control VCXO) through the signal resampler, and resampler is controlled by the adjustment step-length of input.Be sent to the relevant estimator of the channel that is operated on the sample rate through the complex data signals after resampling, the relevant estimator of channel respectively with the preamble word of " PN255+0 " carries out relevant with the Q road I road of input signal, and square add up, obtain relevant information, i.e. the time domain correlation energy value of signal.Carry out the energy matched filtering through as shown in Figure 7 energy converging filter again, then will be through flux matched relevant information sending into big step-length isochronous controller and the long isochronous controller of small step respectively.
Time-domain channel synchronous tracker provided by the present invention comprises that signal resampling module, equalizer center tester, the relevant estimator of channel, big step-length are adjusted controller synchronously, little step-length is adjusted controller, channel information analyzer and signal superimposer synchronously.The signal that is input as the output of signal resampling module of equalizer center tester, the input of the relevant estimator of channel is connected with the output of signal resampling module, the output of the relevant estimator of channel and the input of channel information analyzer are connected, the output of channel information analyzer simultaneously and big step-length adjust controller, little step-length synchronously and adjust the input of controller and equalizer center tester synchronously and be connected, big step-length is adjusted output that controller and little step-length adjust controller synchronously synchronously and is connected with signal resampling module after by the stack of signal superimposer.
Signal resampling module is finished input analog signal R is sampled, and obtains digital signal T; The relevant estimator of channel is finished the estimation to the channel information parameter; The equalizer center tester, output result according to the channel information analyzer, dynamically adjust the position of multipath signal, thereby make that this kind equalizer can the adaptive variation along with channel variation with respect to the virtual center of " adaptive equalizer " with virtual center; Big step-length is adjusted controller synchronously, according to the analysis result of channel information analyzer, finishes the synchronous tracking Control of big step-length to channel; Little step-length is adjusted controller synchronously, according to the analysis result of channel information analyzer, finishes the synchronous tracking Control of little step-length to channel.
Digital sampled signal T is as the input of relevant estimator of channel and equalizer center tester, the output H of the relevant estimator of channel is the input that channel information analyzer and little step-length are adjusted controller synchronously, channel information analyzer output control information C is that equalizer center tester, big step-length are adjusted the input that controller and little step-length are adjusted controller synchronously synchronously, and channel information analyzer output step-length control information L adjusts controller for big step-length synchronously.Big step-length adjusts controller output S1 synchronously and little step-length is adjusted controller output S2 synchronously, adds and produce step length command signal S to control or resampler to VCXO, and the output signal of equalizer center tester is data-signal 0 and control signal I.Digital signal T is the data complex signal after sampling, digital signaling zero is a signal of exporting to equalizer, and digital signal C, G, I are the Boolean type control signal, are used to indicate the state of control, digital signal H, S1, S2, S, L are the data type control signal, are used to indicate the size of concrete control.
Signal resampling module can be made of an A/D sampler and a VCXO, input analog signal R enters the A/D sampler, the A/D sampler generates digital sampled signal T under the control of VCXO, the output of signal superimposer at this moment is connected to the VCXO of signal resampling module; Signal resampling module can also be made of an A/D sampler, a fixed crystal oscillator and a signal resampler, the A/D sampler is subjected to the control of fixed crystal oscillator, input analog signal R is by entering signal resampler again behind the A/D sampler, obtain digital sampled signal T, the output of signal superimposer at this moment is connected to the fixed crystal oscillator of signal resampling module.
Described signal resampler comprises an addition and controller, two interpolaters, a data Strobe Controller and three delay units.Three outputs of addition and controller are connected with three delay units respectively, and the output of two delay units is connected with interpolater, and the output of the output of another delay unit and two interpolaters is linked and connect the data strobe controller.The step change amount that the is input as Δ u of addition and controller, addition and controller obtain step-length output u to Δ u modulo operation; Interpolater is finished the interpolative operation of data, and the size according to step-length output u resamples to data, and interpolater can be the interpolater of sinusoidal structured, also can be the interpolater of Farrow structure; The data strobe controller is according to the signal after the output decision output resampling of interpolater and addition and controller.
The relevant estimator of channel comprises two channel correlators, two squarers, a signal superimposer and an energy converging filter.Two inputs of channel correlators are respectively the in-phase component II and the quadrature component IQ of sampled signal, channel correlators is output as the input of squarer, the squarer of homophase road signal and positive cross-channel signal is output as the input of signal superimposer, the signal superimposer is output as the input of energy converging filter, and the output of energy converging filter is the output of channel correlators.
Described channel correlators is the time-domain signal correlator, by the relevant time domain impulse response that obtains channel of preamble word or other predetermined sequences; Squarer carries out square operation to signal, to eliminate the influence of phase deviation; The signal superimposer sums up computing to signal; The energy converging filter carries out matching aggregation to signal correction estimated energy signal.
Channel correlators is utilized preamble word or other Given informations in the transmission signals, input signal is carried out asynchronous related operation, consider that The noise carries out Threshold detection to relevant output, surpass of the time domain impulse response of the response numerical value of thresholding as channel, wherein correlator can be the correlator of integral multiple, also can be the correlator of branch several times.As: the M sequence of " PN255+0 " adopts the BPSK mapping at diagonal angle to obtain 256 symbols, for with these 256 symbols as preamble word, 1024 symbols frame structure as data, it is asynchronous relevant that channel correlators selects for use these 256 symbols to do, again the output thresholding of correlator is selected, to the correlation that surpasses thresholding as the channel time domain impulse response.
Described energy converging filter, its filter construction are a FIR filter, and filter wants to satisfy the effect of signal stack, and this filter coefficient requires and the correlator output signal is complementary.Consider that correlator is the relevant of quadratic sum, this filter coefficient should be the SINC function square.In addition, consider the problem that hardware is realized, this filter coefficient can be reduced to the shape of " broad in the middle, narrowing toward each end ", as coefficient models such as the filter coefficient of triangular form, semi-circular filter coefficient or parabolical filter coefficients.
The channel information analyzer comprises an information detector, an area dividing device, a regional peak detector, a State Control machine and a direction confidence counter.The input signal of information detector is a channel estimating information, information detector is output as the input of area dividing device, the area dividing device is output as the input of regional peak detector, the zone peak detector is output as the input of State Control machine, and the State Control machine is output as the input of direction confidence counter.
Described information detector is finished the relevant estimator estimated channel information of channel is detected, and finds the regional location at information place, for the work of area dividing device is prepared; The area dividing device, the channel information that information detector is found carries out the division on the time zone; The zone peak detector extracts the channel information in the zones of different, finds out size and the relative position and the output of correlation largest peaks in this zone; The State Control machine is triggering with the size and the position of peak value in each zone of regional peak detector output, is mechanism with the workflow diagram of state machine, the adjustment operating state; The direction confidence counter is by the control information that letter finally produces output of putting to control signal.
Described regional peak detector is a data search engine, and maximizing from several buffers of area dividing device should peaked numerical value and relative position output.Situation for 3 zones, in 33 data among the buffer R0, maximizing P0 and relative position L0, maximizing P1 and relative position L1 in 240 data from buffer R1, maximizing P2 and relative position L2 in 240 data from buffer R2.
Described area dividing device, the channel information that information detector is found carries out the division on the time zone, by this kind method, channel information is simplified extraction, and the number of area dividing is preferably 3.As Figure 10: determined the information position by information detector, by 3 zones of time area dividing, be respectively R0, R1 and R2 zone, R0 is the central area, R1 and R2 are the areas at both sides of symmetry, the size in 3 zones is respectively 33 symbols, 240 symbols and 240 symbols, and the correlation in 3 zones is stored in respectively in 3 buffers.
Described information detector is finished from the information of the relevant estimator output of channel and is detected the channel information that will analyze, comprises a threshold detector, positional information counter and a confidence counter.As frame structure for above-mentioned " 256 preamble word+1024 data ", the relevant estimator estimated channel information of channel is the time domain impulse response of channel, this time domain impulse response meeting occurred according to the situation cycle of frame structure, per 1280 symbols occur once, information detector at first carries out Threshold detection to correlation, surpass thresholding then confidence counter begin counting, add 1 when then counting appears again in the situation that surpasses thresholding every 1280 symbols, otherwise subtract 1, threshold value is that 0 o'clock information detector resets, put the letter number if confidence counter surpasses thresholding, such as 6, then the position of perch channel information is found.By the method that this kind put letter, information detector is finished the detection to channel information.
Described State Control machine, for the state between several states is coordinated controller, output result according to area dividing device and regional peak detector, the variation of dynamic debugging system state, export control signal simultaneously and give confidence counter, control signal is+1 ,-1 or 0 Boolean type signal, wherein+1 is designated as big step-length and accelerates sampling rate,-1 is designated as the big step-length sampling rate that slows down, and 0 for not doing big step-length adjustment.
The direction that described direction confidence counter determine to be adjusted, the variation that prevents to adjust direction is too frequent, and counter is to being continuously positive situation or being continuously negative situation counting, when counting satisfies certain thresholding, outbound course control signal then.
Big step-length is adjusted the big step-length of controller ground synchronously and is adjusted the position of data in equalizer, and multipath signal is optimally covered by equalizer, thereby strengthens the ability of equalizer antagonism multipath signal.Big step-length is adjusted controller according to the control signal C of channel information analyzer output and the concrete numerical value of L, produces step-length and adjusts signal S1.The symbol decision of S1 is accelerated or the sampling rate that slows down, and step-length is adjusted the size of the concrete numerical value decision sampling rate adjustment of signal.The symbol of S1 is according to the decision of the symbol of control signal C, the concrete numerical value of S1 is by adopting suitable weighting to decide to L, and the process that requires to change is level and smooth change procedure, and promptly the first derivative of weighting function is continuous, the method of weighting has a lot, as adopting y=x
3Method of weighting.L is big more, and S1 is just big more, and the speed of " pulling " is just fast more; L is more little, and S1 is just more little, and the speed of " pulling " is just slow more, and purpose is to finish one continual, level and smooth, progressive " pulling ".
Big step size controller detects the relevant information of the input information of carrying out, from relevant information, find the channel information that to analyze, job step is for setting a threshold value, when surpassing threshold value, think and tentatively found the position of channel related information, consider that channel related information is to occur in the cycle, should occur in the cycle once every 1280 symbols, so situation about occurring again for correlation peak behind 1280 symbols, counter adds 1, otherwise subtract 1, when counter is 0, think that the detection of front is wrong, and when counter is 6, think the enough believable position of finding channel related information, and this positional information is passed to the area dividing device.
Little step-length is adjusted controller synchronously and is comprised a channel frequency discrimination filter and a loop filter.The control information of the channel estimating information that is input as of channel frequency discrimination filter and the output of channel information analyzer, the control information of the output of channel frequency discrimination filter and the output of channel information analyzer is the input of loop filter, and loop filter is output as the long control information of small step.
The filter that described channel frequency discrimination filter is a FIR structure and a data gate, the output result of filter is input in the data strobe device, data strobe device according to the output of index signal decision filter whether as the output of channel frequency discrimination filter, thereby make filter finish the frequency discrimination filter function of a kind of " photographic means ".The central area size that the length of filter is divided for the area dividing device, the tap coefficient model of filter is the odd symmetric model in center, the i.e. model on " both sides big, middle little ", the filter tap coefficients model can be the first-order linear function type, perhaps positive cotangent function type or parabolic function type.
Described loop filter is the structure of the active proportional integral low pass filter of second order, and concrete coefficient calculates according to the loop formula.
Described State Control machine, for the state between several states is coordinated controller, according to the output result of area dividing device and regional peak detector, the variation of Adjustment System state makes being covered by equalizer of multipath signal optimum.Shown in Figure 11 is the flow chart of 3 states, according to the relation between the maximum in 3 zones, the dynamically variation of adjustment state, export control signal simultaneously and give confidence counter, control signal is+1 ,-1 or 0 Boolean type signal, wherein+1 be designated as big step-length and accelerate sampling rate ,-1 is designated as the big step-length sampling rate that slows down, and 0 for not doing big step-length adjustment.
Described direction confidence counter, purpose are for the direction of determine adjusting, and the variation that prevents to adjust direction is too frequent, and counter is to being continuously positive situation or being continuously negative situation counting, when counting satisfies certain thresholding, and outbound course control signal then.
The area dividing device is divided into 3 zones with relevant information by the time based on this positional information, and as shown in figure 10,3 zones are R0, R1 and R2, and the R0 area size is 33 sampled points, and the R1 zone is 496 sampled points, and the R2 zone also is 496 sampled points.By three buffers that the area dividing device obtains, size is respectively 33,496 and 496.The zone peak detector carries out maximum value search for the data in these 3 buffers, as maximizing P0, P1 and P2, obtains three relative position L0, L1 and the L2 of maximum correspondence simultaneously.Suppose P0=100, P1=10, P2=120, L0=0, L1=-20, L2=30.
State machine is adjusted operating state according to trizonal maximum P0, P1 and the P2 of regional peak detector output, situation according to P0=100, P1=10 and P2=120, state machine will be promptly by accelerating sample rate, the position of peak value P2 " is drawn in " zone of R0, because the center correspondence of " adaptive equalizer with virtual center " the center in the zone of R0, to make strong footpath drop on the center of equalizer so the position of P2 " is drawn in " the R0 zone, thereby improve the ability of time-domain equalizer antagonism multipath signal.Sample rate is accelerated in state machine outbound course control signal+1 expression, and the distance 30 that output simultaneously will be adjusted is given the direction confidence counter.The direction confidence counter thinks it really is the speed that will accelerate sample receiving continuously at 4+1 o'clock, thereby outbound course control signal C is+1, and the distance L that output simultaneously will be adjusted is 30.
Little step-length is adjusted only work when C is 0 of controller synchronously, does not work for+1 o'clock at C, and inner counter all is reset to 0.Big step-length is adjusted controller synchronously and is started working when C is for+1, and S1 is according to C=+1 and L=30 in output, adopts y=x
3Weighting, S1 is output as+27000.
Weighting S by step-length is+27000, voltage controlled oscillator or signal resampler will be accelerated the signals sampling rate according to step-length adjustment+27000 of input, make multipath signal by " pulling ", thereby make multipath P2 be covered, improved the performance of equalizer anti-multipath by the equalizer center.
Wherein, along with the quickening of sample rate, by " pulling " close R0 zone, equalizer center, L is more little gradually for P2, and step-length S is also just more little, and the speed of " pulling " is also just slow more.Thereby realized level and smooth, continual, progressive " pulling ", the corresponding equalizer of LMS adaptive algorithm that adopts of this mode is very important.
In addition, when peak value P2 adjusts controller synchronously by after " pulling " enter the R0 zone by big step-length, step-length is adjusted controller synchronously and will be quit work greatly, and little step-length is adjusted controller synchronously and started working.Little step-length is adjusted controller synchronously for example as Figure 15.The signal that 2 multipaths are wherein arranged in the R0 zone, obtaining its correlation by the relevant estimator of channel is 3 and 2, if the center in R0 zone is shown in figure a, then obtaining the frequency discrimination filtering output value by channel frequency discrimination filter " photograph " mode is 3 * 0.5+2 * (0.5)=0.5, numerical value 0.5 will control voltage controlled oscillator by loop filtering or the signal resampler is accelerated sampling rate, thereby the center of adjusting the R0 zone is for shown in the figure b, this moment, the output valve of frequency discrimination filter was 3 * 0.4+2 * (0.6)=0, thereby loop enters stable status.
In the above-described example as can be seen, variation along with multipath signal, the present invention samples to adjust uniting of big step-length and little step-length and realizes " pulling " of multipath signal, thereby makes multipath signal optimally be covered by equalizer, improves the ability of equalizer antagonism multipath signal.
Claims (7)
1. time-domain channel synchronous tracker, it is characterized in that, comprise that signal resampling module, equalizer center tester, the relevant estimator of channel, big step-length are adjusted controller synchronously, little step-length is adjusted controller, channel information analyzer and signal superimposer synchronously; The signal that is input as the output of signal resampling module of equalizer center tester, the input of the relevant estimator of channel is connected with the output of signal resampling module, the output of the relevant estimator of channel and the input of channel information analyzer are connected, the output of channel information analyzer is adjusted controller synchronously with big step-length simultaneously, the input that little step-length is adjusted controller and equalizer center tester synchronously is connected, big step-length is adjusted controller and little step-length synchronously and is adjusted the step-length of controller output synchronously and adjust signal and export signal resampling module to by the stack of signal superimposer, and described signal resampling module is controlled by the adjustment step-length of input;
Signal resampling module is finished input analog signal R is sampled, and obtains digital signal T; The relevant estimator of channel is finished the estimation to the channel information parameter; The equalizer center tester, output result according to the channel information analyzer, dynamically adjust the position of multipath signal, thereby make that this kind equalizer can the adaptive variation along with channel variation with respect to the virtual center of " adaptive equalizer " with virtual center; Big step-length is adjusted controller synchronously, according to the analysis result of channel information analyzer, finishes the synchronous tracking Control of big step-length to channel; Little step-length is adjusted controller synchronously, according to the analysis result of channel information analyzer, finishes the synchronous tracking Control of little step-length to channel.
2. time-domain channel synchronous tracker according to claim 1, it is characterized in that, signal resampling module is made of an A/D sampler and a VCXO, input analog signal R enters the A/D sampler, the A/D sampler generates digital sampled signal T under the control of VCXO, the output of signal superimposer at this moment is connected to the VCXO of signal resampling module.
3. time-domain channel synchronous tracker according to claim 1, it is characterized in that, signal resampling module is made of an A/D sampler, a fixed crystal oscillator and a signal resampler, the A/D sampler is subjected to the control of fixed crystal oscillator, input analog signal R is by entering signal resampler again behind the A/D sampler, obtain digital sampled signal T, the output of signal superimposer at this moment is connected to the fixed crystal oscillator of signal resampling module;
Described signal resampler comprises an addition and controller, two interpolaters, a data Strobe Controller and three delay units; Three outputs of addition and controller are connected with three delay units respectively, and the output of two delay units is connected with interpolater, and the output of the output of another delay unit and two interpolaters is linked and connect the data strobe controller; Interpolater is the interpolater of sinusoidal structured or is the interpolater of Farrow structure; The data strobe controller is according to the signal after the output decision output resampling of interpolater and addition and controller.
4. time-domain channel synchronous tracker according to claim 1 is characterized in that, the relevant estimator of channel comprises two channel correlators, two squarers, a signal superimposer and an energy converging filter; Two inputs of channel correlators are respectively the in-phase component II and the quadrature component IQ of sampled signal, channel correlators is output as the input of squarer, the squarer of homophase road signal and positive cross-channel signal is output as the input of signal superimposer, the signal superimposer is output as the input of energy converging filter, and the output of energy converging filter is the output of channel correlators;
Described channel correlators is the time-domain signal correlator, by the relevant time domain impulse response that obtains channel of preamble word or other predetermined sequences; Squarer carries out square operation to signal, to eliminate the influence of phase deviation; The signal superimposer sums up computing to signal; The energy converging filter carries out matching aggregation to signal correction estimated energy signal;
Channel correlators is utilized preamble word or other Given informations in the transmission signals, input signal is carried out asynchronous related operation, consider that The noise carries out Threshold detection to relevant output, surpass of the time domain impulse response of the response numerical value of thresholding as channel, wherein correlator can be the correlator of integral multiple, also can be the correlator of branch several times;
Described energy converging filter, its filter construction are a FIR filter, and described filter can superpose to signal, and this filter coefficient requires and the correlator output signal is complementary; Filter coefficient is coefficient models such as the filter coefficient of triangular form, semi-circular filter coefficient or parabolical filter coefficient.
5. time-domain channel synchronous tracker according to claim 1 is characterized in that, the channel information analyzer comprises an information detector, an area dividing device, a regional peak detector, a State Control machine and a direction confidence counter; The input signal of information detector is a channel estimating information, information detector is output as the input of area dividing device, the area dividing device is output as the input of regional peak detector, the zone peak detector is output as the input of State Control machine, and the State Control machine is output as the input of direction confidence counter.
6. time-domain channel synchronous tracker according to claim 1 is characterized in that, big step-length is adjusted controller according to the control signal C of channel information analyzer output and the concrete numerical value of L, produces step-length and adjusts signal S1; The symbol decision of S1 is accelerated or the sampling rate that slows down, and step-length is adjusted the size of the concrete numerical value decision sampling rate adjustment of signal; The symbol of S1 is according to the decision of the symbol of control signal C, and the concrete numerical value of S1 decides by L is weighted, and the weighting function first derivative is continuous; Described big step-length is adjusted the big step-length of controller ground synchronously and is adjusted the position of data in equalizer, and multipath signal is optimally covered by equalizer, thereby strengthens the ability of equalizer antagonism multipath signal.
7. time-domain channel synchronous tracker according to claim 1 is characterized in that, little step-length is adjusted controller synchronously and comprised a channel frequency discrimination filter and a loop filter; The control information of the channel estimating information that is input as of channel frequency discrimination filter and the output of channel information analyzer, the control information of the output of channel frequency discrimination filter and the output of channel information analyzer is the input of loop filter, and loop filter is output as the long control information of small step;
The filter that described channel frequency discrimination filter is a FIR structure and a data gate, the output result of filter is input in the data strobe device, data strobe device according to the output of the control information decision filter of channel information analyzer output whether as the output of channel frequency discrimination filter; The central area size that the length of filter is divided for the area dividing device, the tap coefficient model of filter is the odd symmetric model in center, is the first-order linear function type, perhaps positive cotangent function type or parabolic function type;
Described loop filter is the structure of the active proportional integral low pass filter of second order, and concrete coefficient calculates according to the loop formula.
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